Article: 40296 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Solar airships Date: 30 Sep 1995 08:55:11 -0400 Organization: Villanova University Anthony Kalenak wrote: >Have you tried to make a physical model of a solar powered airship. Not yet. Altho I've thought about trying to make a higher temperature version, an indoor floating lamp with a very lightweight bulb inside, perhaps just some fine tungsten wire, with some fine copper wires for power transmission and tethering. This might be an interesting toy. Physics professor Paul Bashus and physics student Erik Ferragut and I are now putting together a fully-instrumented 2' x 4' x 8' tall solar closet and "house", which we will reassemble and install this week next to the astronomical observatory on top of the science building at the local college, Ursinus. It will have a microprocessor-controlled multichannel I/O electronic data logger/controller (a Lambert Engineering "Data Trap") and a modem, with five temperature probes and a Licor pyroheliometer. (We could use some low-speed airflow measurement equipment too.) The test box will contain three 36 watt fans, which we hope to seldom use. The system is designed so that it will also operate without any fans. The data logger will control the fans, and measure the power needed to drive them, as well as the rest of the power used in the house, including its own, via a current transformer and watt transducer. Our goal is to develop and test an inexpensive system that will maintain the house at exactly 70 F all winter, 24 hours a day, even on -10 F nights in January, up there on the roof in the wind and the snow, while using absolutely no backup heat at all this winter. We will put a backup heater in the "house," and measure the power required to run it. None, we hope. If you'd like to contribute to the expenses for this project, send your tax-deductable contribution to: Physics Equipment Gift Fund Ursinus College Collegeville, PA 19426 with an email note to me, with your postal address, and I'll send you our paper "Solar Closets and Sunspaces," with some illustrations and simple mathematics. Paul and I have spent about $3,000 of our own money on this so far. Nick Below is a test box, a 2' x 4' x 8' tall "house" attached to a solar closet. 8' 2' R20 ---------------.--------------- 30 F | | | | 70 F Vr Tw | 2' | | | | "house" | solar closet | | | | ------Vs------- ------Vc------- | | | 9" | Ts ggggggggggggggg | sunspace | 7" ggggggggggggggggggggggggggggggg south It is built with 7 2' x 8' insulated modular panels, each made from a 1 x 3 frame with a 2 x 8 sheet of 1/4" plywood attached to the inside face and a 2 x 8 x 2" piece of Styrofoam cut to fit into the 1 x 3 frame, and another 2" piece of Styrofoam screwed to the outside of the frame. Such panels have an R-value of about 20. This would be a poorly-insulated house, by today's standards. Each panel weighs about 20 pounds, and can be easily lifted by one person. The sun shines in through the glazing over the air heater, which is attached to the front of the solar closet, and a plastic film backdraft damper Vc allows solar heated air to enter the closet and heat some 55 gallon drums full of water, when the passive air heater is warmer than the drums. In our test box, Vc will also have a fan to blow air into the solar closet. We expect to omit this in the final design. The glazing is Replex ((800) 726-5151) 20 mil flat, clear, polycarbonate plastic, which comes in rolls 48" wide x 50' long, and costs about $1.50/ft^2. Vr is a $12 Leslie-Locke AFV-1B automatic foundation vent, available from Home Depot, attached to a rectangular hole at the top of the closet, with its bimetallic spring reversed and adjusted so the louvers are fully closed when the house is above 60 F. This will allow warm air from the solar closet to heat the house on a cloudy day. An open slot at the bottom of the closet serves as the return air path. Vc will have a fan, which will only be used on very cold nights. Vs is another foundation vent, adjusted so the louvers are fully closed at 70 F (or lower.) When the house temperature is less than 70 F, Vs will open to allow sunspace air to warm the house. Vs has another plastic backdraft damper in front of it so that air can only flow through Vs from the sunspace into the house, not in the other direction. Vs has a fan in our test box. We expect to omit this in the final design. Steady-state performance ------------------------ It is interesting to calculate two temperatures above: Ts is the average sunspace temperature when the sun is shining on an average day, and Tw is the steady-state solar closet temperature after a string of average days, with some sun. The sunspace in this scheme overheats to act as a parasitic or slave heater, helping the solar closet achieve a higher temperature, while the losses from the hot glazing on the solar closet make the air in the sunspace hotter. The sunspace air is used to heat the house on an average day, with some sun. (This is similar to "Khanh's Radically New Approach to Increasing the Useful Output of a Flat-Plate Collector Panel..." as described on pages 118-125 of William Shurcliff's 1979 book _New Inventions in Low-Cost Solar Heating_, Published by Brick House, except that not all the "slave heat" is lost to the outside world.) With these assumptions: 1. The average wintertime outdoor temperature is 30 F; 2. On an average winter day, the sunspace receives 1000 Btu/ft^2 of sun over 6 hours; 3. The average house temperature is 70 F, with no air infiltration or internal heat generation; 4. The water and air in the solar closet and the passive air heater all have the same temperature (approaching this requires careful design); and 5. Each layer of glazing has an R-value and solar transmittance of 1, on an average winter day, the 8' x 8' sunspace would receive (1) Eins = 4' x 8' x 1000 Btu/ft^2 = 32K Btu, and this would be lost to the outside world through the sides and roof of the structure as (2) Eouts = 6 hours (Ts - 30) 32 ft^2/R1 Sunspace, daytime + 18 hours (70 - 30) 16 ft^2/R20 West sunspace, nightime + 18 hours (Tw - 30) 16 ft^2/R20 East sunspace, nightime + 24 hours (Tw - 30) 36 ft^2/R20 Solar closet, daily + 24 hours (70 - 30) 36 ft^2/R20 House, daily = 192 Ts - 5760 + 576 + 14.4 Tw - 432 + 43.2 Tw - 1296 + + 1728 -------------------------------- = 192 Ts + 57.6 Tw - 5184. On an average winter day, the solar closet would receive (3) Einc = 2' x 8' x 1000 Btu/ft^2 = 16K Btu, and this would be lost through the outside world and the rest of the house as approximately (4) Eoutc = 6 hours (Tw - Ts) 16 ft^2/R1 To the sunspace, daytime + 18 hours (Tw - 30) 16 ft^2/R20 To the sunspace, nightime + 24 hours (Tw - 30) 36 ft^2/R20 To the outside, daily + 24 hours (Tw - 70) 16 ft^2/R20 To the house, daily. = -96 Ts + 96 Tw + 14.4 Tw - 432 + 43.2 Tw - 1296 + 19.2 Tw - 576 ------------------------------- = -96 Ts + 172.8 Tw - 2304. Setting (1) = (2) and (3) = (4), and adding (4) to (2) twice, 64K = 403.2 Tw - 9,792, so Tw = (64K + 9,792)/403.2 = 183 degrees F. Substituting Tw back into (1), 32K = 192 Ts + 5,358, so Ts = 138.8 F. So after a string of average days with some sun, the closet will be about 40 degrees warmer than the peak daytime sunspace temperature, but it will stay at that temperature 24 hours a day, "just coasting," vs. the low- thermal mass sunspace, which will get icy cold every night. Cloudy-day performance ---------------------- On the first of several days with no sun, the structure will lose about (2) Ens = 24 hours (70 - 30) 16 ft^2/R20 West sunspace + 24 hours (183 - 30) 16 ft^2/R20 East sunspace + 24 hours (183 - 30) 36 ft^2/R20 Solar closet + 24 hours (70 - 30) 36 ft^2/R20 House --------------------------------- = 12,043 Btu. If a 2' x 4' x 8' solar closet contains 2 55 gallon drums full of water, along with some cement blocks and plastic soda bottles, it might have a thermal mass of 1120 Btu/F (see below) so on the first day with no sun, the water temperature would decrease by about Ens/C = 10.8 degrees F. If the closet lost heat at this rate every day until it reached a minimum usable temperature of say, 80 F, (as the closet cools down, it actually loses heat more slowly), it could provide useful heat for the "house" for at least (183-80)/10.8 = 9.5 days in a row with no sun. Taking account of the fact that the closet cools more slowly as time goes on, it should provide heat for about 14 days without sun: 10 '2' x 4' x 8' solar closet house carryover 20 ' find steady-state closet temp 30 EINS=32000!'sunspace solar gain (Btu/day) 40 EINC=16000'closet solar gain (Btu/day) 50 CWS=18*16/20+24*36/20'sunspace Tw factor 60 CWC=6*16/1+18*16/20+24*36/20+24*16/20'closet Tw factor 70 CS=6*30*32/1+18*30*16/20+24*30*36/20'sunspace constant 80 CS=CS-18*(70-30)*16/20-24*(70-30)*36/20'more sunspace constant 90 CC=18*30*16/20+24*30*36/20+24*70*16/20'closet constant 100 TW=(EINS+2*EINC+CS+2*CC)/(CWS+2*CWC)'initial solar closet temperature 140 C=2*55*8+51*4.2+13*2.1'thermal mass of solar closet (Btu/F) 150 CLOSS=24*(70-30)*16/20'constant daily west sunspace heat loss (Btu) 160 CLOSS=CLOSS+24*(70-30)*36/20'constant daily house heat loss (Btu) 163 PRINT"1000' Temp at" 165 PRINT"1020' Day end of day" 170 FOR D=1 TO 14 STEP 1'calc closet temp for 30 days without sun 180 TLOSS=24*(TW-30)*(16+36)/20'solar closet daily heat loss 190 HEATLOSS = CLOSS+TLOSS 200 TW=TW-HEATLOSS/C'new solar closet temperature 210 PRINT 1020+D;"'";D,INT(TW+.5) 220 NEXT D Thermal mass: 1122 Btu/F Initial water temp: 187 F Temp at Day end of day 1 176 2 166 3 156 4 147 5 138 6 130 7 122 8 115 9 108 10 101 11 95 12 89 13 84 14 78 Trying this out should be interesting :-) Nick Article: 41300 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Today's high, in the solar attic Date: 24 Oct 1995 07:28:09 -0400 Organization: Villanova University Andrew McKegney wrote: >If your attic has any wood , paper or non-fireproofed wood fibers in it >you could create a problem for yourself. It has all that stuff. Wide pine floorboards, cedar shingles on the north side, dacron ropes around the rafters, holding up the second floor, etc. >If these materials are exposed to high temperatures for long periods of time, >they develop phyric (?) compounds that can eaisly catch fire. I wonder how high these high temperatures have to be? It seems unlikely to me that the attic will catch fire, since it has little insulation. That would be interesting, tho. A pyric victory, in solar air heater design. I'd worry more if this were a concentrating system. Howard Reichmuth, P.E., says he almost melted a pair of good rubber boots, by accidentally standing in the line focus of his parabolic concentrating greenhouse, 20 years ago. His advice: "Don't stand in the focus!" The attic will have some cooling, eventually, in the form of blowing some of the warm air down to the rest of the stone house, to store heat in the stone walls, surrounded by foam insulation on the outside. >This is why the idea of building solar panels of wood went up in flames. >Literally. Sounds like suburban folklore to me. Altho I could imagine that happening in a well-insulated, stagnated, liquid solar collector, if the pump failed. That kind of collector is expensive and goes on the roof, in the wind and the snow, with antifreeze and heat exchangers and complicated control panels. I'm not very interested in those things. If I insulated it _really_ well, perhaps my attic could use some 180 F passive vent openers to open the doors under the turbine vents, if the temperature gets too high up there. Solar Components 121 Valley Street/Manchester, NH 03103-6211 $56 #13040 Solarvents are said to start opening at 188 F and be fully open at 212 F, altho the last one I tried 20 years ago didn't work very well. Perhaps you are not supposed to boil them long in a pot full of water on the stove. Jade Mountain (800) 442-1972 sells $54 #FC115 Thermofor vents, and Steve Troy says they work well, lifting 15 pounds 15", but the catalog says "select a temperature between 55-85 degrees." BTW, I've decided to hang a $70, 32' x 16' layer of 80% greenhouse shadecloth on top of the transparent part of the attic next summer, using a couple of pulleys and ropes. This should make the attic a lot cooler, and make the clear, corrugated, polycarbonate glazing last a lot longer. It won't interfere with the view that much. I had it hanging over the whole south front wall of the house this summer, and the worst part was the moire pattern it made as I looked through the screened part of the windows from the inside. From the outside, it just looked black. A new look in houses. Trendy, perhaps. >Better consult your local fire department before you go much further. I don't think they know much about this sort of thing. I gave them a copy of my solar closet paper a while ago, and suggested that they modify their firehouse accordingly. The firehouse has a very nice white stucco south-facing wall, with no windows, but I don't see any changes yet. I suspect they don't even know about Ohm's law for heatflow. The south wall of the Ursinus College building next to the firehouse is completely shaded by big evergreens close to the wall, and it has a lovely porch upstairs that is crying out to be glazed in, after the evergreens are cut down, but that hasn't happened either. I guess Ursinus College doesn't know much about Ohm's law for heatflow either. >A point to consider. Unless you have something to store the heat in, >you'd be better off installing a skylight directly into the living space. Sounds like a good idea for daylighting, perhaps with a reflective sunscoop, aimed south, but I'd think one would want a large amount of vertical glazing to collect low-angle winter sun, and one needs some way to avoid having all the house heat disappear out the glazing at night, or during periods of cloudy weather. >The mass in the living space will absorb some of the heat... Indeed it will. We should build more stone houses, surrounded by polyurethane foam. There was one described in a recent Mother Earth News, built by two brothers with wheelbarrows--13 million pounds of rocks, including the stone roof, but they forgot the foam on the outside. Concrete furniture also helps, in ordinary houses. >Remember maximize the insulation before trying to use the insolation! Perhaps someone should tell David Boyer about that. His 2,000 ft^2 commercial greenhouse in Sassamansville, PA is doing fine at the moment, with a single layer of R0.7 polyethylene greenhouse film surrounding a lot of poinsettias, which are sitting on top of 200 55 gallon drums full of water. He doesn't seem worried about fire, either. I think he understands Ohm's law for heatflow. Thank you for your concern, Andy. Nick Article: 41323 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Today's high, in the solar attic Date: 25 Oct 1995 01:29:04 -0400 Organization: Villanova University Dan Settles wrote: >Hi Nick, Hi Dan :-) >Glad to see you are still sharing information on your solar experiment. I'm happy that there is more than one of them underway: David Boyer's greenhouse, the small solar house on top of the science building at the local college (donations still welcome :-), and the roof of my house. Now that the small solar house is up on the roof and working, the next thing I want to do is to bring down some hot air from my attic with a fan, and add a lean-to sunspace on the front of my house, using some curved steel pipes and plastic film glazing, standard commercial greenhouse materials. >I was wondering if you are approaching the upper temperature limit for the >polycarbonate. I can't remember what that upper limit is, but I was >wondering if you may start degrading your roof if it gets much warmer? I don't know what the upper limit is either, but nothing's sagged or melted yet, and the fires are under control :-) The manufacturer says that a continuous temperature of 130 F is no problem. Nick Article: 41329 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Today's high, in the solar attic Date: 25 Oct 1995 05:09:01 -0400 Organization: Villanova University >Dan Settles wrote: >I was wondering if you are approaching the upper temperature limit for the >polycarbonate... Three more thoughts: My polycarbonate plastic roof is very thin, a single layer 0.020" thick, and the plastic itself has a fairly high thermal conductivity, so it will probably have a uniform temperature that is halfway between the attic air temperature and the outdoor temperature, like a paper cup used to boil water over a candle. Even if the attic were perfectly insulated, the attic air temperature has a natural limit, based on radiation losses. If the peak solar power into a square foot of glazing were 300 Btu/hour, and there were no thermal storage in the attic, and the outdoor temperature were 30 F, and all of the solar power left through the glazing by radiation (it doesn't, in this case-- Table 4.2 of _Greenhouse Engineering_ (3rd revision, August, 1994, published by the Northeast Regional Agricultural Engineering Service at Cornell, 152 Riley-Robb Hall/Cooperative Extension/Ithaca, NY 14853-5701) lists the solar and infrared transmissivities of polycarbonate as 0.85 and 0.01, _better_ than a single layer of window glass, listed at 0.85 and 0.02-- meltdowns are less likely with polyethylene film :-), which has solar and infrared transmissivities of 0.92 and 0.81) we have a maximum attic air temperature of roughly 122 F, from the following formula: 300 = 0.174 x 10^-8 ((Ta+460)^4 - (30+460)^4). If the R-value of the inside air film under the plastic were 2/3, and the plastic itself and outside air film were perfectly conductive, and the plastic passed no infrared radiation at all, the maximum attic air temperature would be closer to 478 F, using Ohm's law for heatflow: 300 = (Ta-30)/R0.67. Double glazing would be more dangerous. Nick Article: 41328 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Solar Energy Date: 25 Oct 1995 04:45:09 -0400 Organization: Villanova University Axel Berger wrote: >...A solar panel can be bought at about 10 DM/W, a Varta >"Solar" lead acid battery is above 3 DM/Ah. This breaks down to 0.63 >DM/kWh for the panel (20 years at 800 nominal hours) and 1.22 DM/kWh >for the battery (maximum charge throughput is 20 kAh at 600 cycles with >40% depth for a 85 Ah unit) making the battery twice as expensive as >the panel. Yes, but if we feed the power back to the grid, we can use just a few batteries. One local builder is designing very nice houses with 2 kW PV arrays and only 8 batteries (the minimum number needed to make enough current for the Trace inverter to work--he could probably use nicad D cells :-) This gives a 3 day supply of electricity for the house, and makes the utility more cooperative, since they get the message "we CAN do this without you." In fact, one of the nice things about these houses is that they do not need a temporary hookup for electrical service, while they are under construction. As soon as the shell is finished (in a day or two, since these are modular houses), the carpenters and plumbers come in and plug their power tools and radios into the wall sockets and go to work. Nick Article: 41410 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Solar Energy Date: 27 Oct 1995 06:50:24 -0400 Organization: Villanova University John Carter wrote: >>Yes, but if we feed the power back to the grid, we can use just a few >>batteries. One local builder is designing very nice houses with 2 kW PV >>arrays and only 8 batteries... > Can you provide additional information regarding the "local" builder >and his modular houses? I am involved in three projects where we want >to build three houses, two very remote and mostly solar powered, the >other less remote, but cost effective with modular and solar advantages. Sure, see the attached reposting. I suggested building this house without the PV panels, since they are still so expensive... Article: 41174 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: An inexpensive, 100% solar house? Date: 20 Oct 1995 09:18:44 -0400 Organization: Villanova University Here's a house that looks like it could be 100% solar-heated, while providing close to 100% solar hot water as well, inexpensively... One might start with Jim Cahill's house, designed by engineer Lyle Rawlings at (609) 466-4495. This was manufactured by AvisAmerica at (800) 284-7263, and built by Jim Cahill at (508) 677-3533. It is described in the September/October 1995 issue of Solar Today, pp 24-27. This very nice house in Falmouth, MA (5800 F DD), has 2530 ft^2 of floorspace. The selling price is listed as $185K, including dealer/builder markup and a 2 kW PV system, so the basic price of the house would be about $170K, without the PV system, and about $160K without the backup heating system or other solar features. Building it without a basement should also lower the price. The estimated annual non-solar fuel requirement is the heat equivalent of 140 gallons of oil (although the house has a natural gas-fired forced hot water backup heating system.) Minimal hot water usage would add another 60 gallons of oil a year to that requirement, making 200 gallons of oil per year. How can we lower that backup heating requirement to zero? (One might also ask, why bother to do anything at all to this superinsulated house, with a basic yearly heating bill of $660, but that's another story.) As designed, the house has 419 ft^2 of south-facing glass, with minimal glazing on the other walls. The ceiling has R38 insulation, and the walls are R27. The house has a remarkably low air infiltration rate of 0.0125 ACH, based on a 50 Pascal air infiltration rate of 0.25 ACH. The house is 44' long and 28' wide and two stories tall. The south windows seem to be the biggest heat losers here: Sum (Ai/Ri) = 420 ft^2/R2 + 28'x44'/R38 + (16'(28'+44')x2-420)/R27 windows ceiling walls = 210 + 32 + 70 = 312. It looks like these south windows account for about 70% of the heat loss of the house, ignoring the air infiltration, which is 1/8 of the ceiling loss. The south windows also contribute solar gain, when the sun is shining. Suppose we somehow change this house so most of the south wall is an insulated frame wall, like the rest of the house walls... ("Oh, it will be less dramatic!" :-) And add some curved galvanized steel pipes and plastic glazing to make a low-thermal mass sunspace, with a solar closet behind it. How big will the sunspace and solar closet have to be, in order to provide 100% of the space heating and close to 100% of the hot water for the house? With an insulated south wall, the new sum above becomes about 120 Btu/hr-F. If the average temperature in December is 32 F, the house would need about 100K Btu of heat on an average December day. If the the sunspace provides a net solar gain of say, 750 Btu/ft^2/day, it will have to have 24hr x 120 (68-32) = 138 ft^2 of glazing. Let's make it 200 ft^2, so the solar closet can provide hot water as well. If the sunspace were 16' tall, it would be about 12' wide. The house would look something like this: 28' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44' . . . . . . . 4' . . . . . . . . . . . . . . . . . . . . 12' sauna? . . . . . ./ clothes drying? . . . . . . . . . . . . . . . . . . . . . . . . . . 8' . . f . . \ . polycarb roof? . s \ . I added a solar attic here too, for fun, . s \ . using corrugated clear polycarbonate . s \ . plastic, and a fan with a backdraft . s \ . damper at the top, to blow down warm . md. . . . . . . . . . . g . air from the peak of the attic into .. . . the house, where it wends its way back . . . . up to the attic through a motorized . .dhw . . return damper, md. g are airflow grates. . . . . g . . . . . . . . . g . The fan is controlled by an attic fan . . f . . . thermostat in series with a house . . . . . thermostat. This is another way to make . . . <== g . a low-thermal-mass sunspace. . . . . . . . . . . . . . . . . . . . . . . . . . s is some greenhouse shadecloth (optional), f is 10' of fin-tube radiator pipe, and dhw is a conventional or indirect-fired water heater ("geyser" in the UK), which is heated by natural water convection using the fin-tube as an air-water heat exchanger. The low-thermal mass sunspace ($1000?) would work best with a fan controlled by an attic thermostat and a house thermostat in series, as well as plastic film backdraft dampers, to prevent reverse airflow at night. The solar closet ($500?) would store enough heat for 5 days without any sun, using 5 days x 100K Btu/day /((130F-80F)x 55 gal x 8lb/gal) = 24 55-gallon sealed drums full of water, assuming an initial water temperature of 130 F, and a minimal usable space heating closet water temperature of 80 F. Who will be the first to order one of these houses? Nick Article: 41412 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Today's high, in the solar attic Date: 27 Oct 1995 08:18:27 -0400 Organization: Villanova University Nick Pine wrote: >... closer to 478 F, using Ohm's law for heatflow: >300 = (Ta-30)/R0.67. Jeez, doesn't ANYONE look at the numbers in these postings?! It's been almost a week now, and nobody's noticed the simple and glaring math error above. Nobody gets any points for finding this mistake. The maximum attic air temperature above should be T = 0.67 x 300 + 30 = 230 F, not 478 F, which is 300/0.67 + 30. One of the nice things about USENET is how people so kindly offer corrections, when one makes a mistake, but that useful process does not seem to work well when we use numbers. How depressing. Our solar closet house model is now overheating, because of some lack of forsight on my part. Yesterday when it was 70 F outside, the house was 104 F, the 1,200 pounds of water in the solar closet was 81 F (still warming up very slowly :-) and the sunspace was 154 F. So today I'm adding a small cooling fan with a thermostat, inter alia, to bring in some cold winter air during the day. This could be done with less energy, using the stack effect and winter winds. We will be measuring and recording windspeeds shortly. Yesterday, the average power used in this 2' x 4' x 8' "house" was about 20 watts, counting power for the three fans and the modem and the data logger itself, which has been taking readings every 2 minutes for the last 24 hours. The data logger also measures its own power. The maximum solar intensity was about 900 watts/m^2. The pyroheliometer sensitivity was insufficient to record starlight, and we observed no significant solar radiation at night :-) If we have some thermal mass up near the ceiling of the house, we can also do night ventilation for summer cooling--low-energy air conditioning: keep the house buttoned up during the day, then ventilate it at night, when the outside air is cool, to cool the thermal mass of the house, which will very gradually warm up over the next day. The 1994 Van Nostrand (?) book by Architect/Engineer Professor Baruch Givoni, _Passive and Low-Energy Cooling of Buildings_, indicates that this technique works well in many parts of the world. Steve Baer estimates that there are very few days in Philadelphia, even in August, in which the night temperature fails to get down to 74 F. We can test that weather hypothesis, and find a cumulative distribution of summer night minimum temperatures, and experiment with this simple form of cooling, now that we have this cooling fan. Steve thinks this will require about 1 cfm/ft^2 of house, which is a lot of ventilation. We want to connect the fans to the Data Trap soon, so we can control them in more interesting programmable ways. Perhaps some gentle reader can do a small theoretical investigation of this, and post the results. How much thermal mass do we need in the house, eg some containers of water near the top of the house, and how much surface area does the thermal mass have to have, and how long does our 6.8 watt, 55 cfm fan have to run each night, if the daily night min is 74 F, and the daily max is 94 F, in order to keep the house at 80 F max, given that it has 72 ft^2 of R20 walls? What will the daily temperature swing be? By the way, contributions to this project are still welcome. If someone sends us some money, we might give them the phone number and password for the house, so they can call up the Data Trap and observe how things have been going, using a modem with simple help menus. Perhaps it can be accessed via a web page. If someone sent us more money, they could do their own experiments remotely, eg write some new real-time fan control algorithms and measure the results. We could even put in a Trombe wall, if somebody wanted to measure its performance, or fill up the solar closet with cement blocks instead of sealed containers of water, or put some fin tube pipe near the ceiling and an insulated container of water on the roof for a solar closet water heating experiment, using a warm water convective loop. This would be a little bit like renting a part of the space shuttle, but much less expensive, and administratively simpler :-) It is more like what Howard Reichmuth, PE, is now doing by modem from Hood River, Oregon. Howard also has a Data Trap and a modem and a solar heating experiment underway somewhere in Hawaii. He probably has a project schedule that requires a site visit in early February. I'll likely be going to Lewiston, Maine, instead :-) So please feel free to send money, even tiny amounts, to: Nicholson L. Pine System design and consulting Pine Associates, Ltd. (610) 489-0545 821 Collegeville Road Fax: (610) 489-7057 Collegeville, PA 19426 Email: nick@ece.vill.edu We will put it to good use. Nick Article 41458 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Solar heat for swimming pool Date: 28 Oct 1995 07:26:16 -0400 Organization: Villanova University Lines: 86 Henry Baker wrote: >I would like to swim as much of the year as possible, but do not want to heat >the pool with a gas heater. I currently have a solar pool cover, which helps a >lot, but before investing in anything more substantial, like solar panels, I >wanted to understand more about the physics of the situation. Solar heating of swimming pools should be easy, compared to say, heating water for showers, because you just have to keep the water warm, not heat up more cold water all the time, and the water constitutes a large built-in thermal mass, and you don't necessarily have to pump it around or use heat exchangers or antifreeze, or go climbing around on roofs, and swimming pool temperatures are lower than domestic hot water temperatures. Covering the pool with a better insulator would help. A "solar pool cover" might have an R-value of 1. Two inches of Styrofoam (R10) would be better. Also, more winter sun falls on a vertical surface than a horizontal surface, since winter sun is low in the sky. "Ohm's law for heatflow" says that an area of A square feet with a (USA) thermal resistance of R, with Farenheit temperatures Tc and Th on each side, will have a heatflow of Q Btu/hour, where Q = (Th-Tc) A/R. It takes 1 Btu to heat or cool 1 pound of water 1 degree F. It takes about 1,000 Btu to evaporate 1 pound of water, and 144 to freeze it. Water weighs about 64 pounds per cubic foot. The average amount of sun falling on 1 square foot of a vertical south-facing surface might be 1,000 Btu/day. The average temperature in December might be 32 F. Suppose the only heat lost from a pool were through the pool cover, and you could somehow collect all the solar heat that fell on a wall the same size as the top of the pool. What would the R-value of the pool cover have to be if you wanted to keep the pool at 72 F in December? Suppose the pool were a 1' cube. Each day, the pool water would lose 24 hours x (72F-32F) x 1/R = 960/R Btu, by Ohm's law for heatflow, and it might collect 1,000 Btu of solar energy, so it looks like an R1 pool cover would work here, giving an average pool water temperature of 1000/24 + 32, ie 73.7 F. After one day with no sun, the temperature of the 1' cube of water would drop about 960/64 = 15 F. Not too bad. But how do you collect the sun on a vertical surface? I knew a man who had a house without much flat ground around it, and he liked both tennis and swimming, so he build a swimming pool with a tennis court on top. When you pushed a button, the tennis court would separate and slide back horizontally to uncover the pool. There were some motors and tracks to make this happen. I keep thinking that a movable rigid cover would be a nice way to heat a swimming pool, IF the long edge of the pool ran east and west. One might make a hinge along the north edge out of 2" galvanized pipe, and attach 20' curved galvanized greenhouse pipes ($35 each) on 4' centers perpendicular to that 2" pipe, with the curved end near the 2" pipe, and use foil-faced foam with some sort of protective coating for the foil, or attach some sort of reflective material to the pool side of plain foam, eg very thin stainless steel or 3M SA-85 outdoor solar reflective film or the coated foil product used on mobile home roofs, made by companies like Innovative Insulation near Dallas, TX. The next step would be to make a small winch (or a passive solar tracker that unbalances its counterweight) raise this parabolic reflective cover automatically during the day, to about a 50 degree angle, if the sun were shining and the pool needed to be warmer. The solar pool cover would stay on the water, preventing evaporation. On a day with no sun, this pool would cool down by less than 2 degrees F. Doing this seems simpler than putting a tennis court on top of a pool... A less elaborate and lower performance system would have the solar pool cover (why don't they make them clear instead of blue, so they will pass more solar energy into the water?) in place all the time, with a fixed parabolic, non-insulating reflector along the north edge. Perhaps a standard commercial greenhouse (52 cents/square foot from Stuppy at (800) 877-5025)) over the whole pool, with some white polyethylene film over the north side of the greenhouse, and clear poly film on the south side. One might have an articulated movable foam cover/reflector inside the greenhouse as well. It would be flat when it covered the pool, becoming a segmented parabola in the raised position. A more elaborate system for an existing pool might use a heliostat, eg a large parabolic reflector combined with a passive tracker that moves it in such a way as to keep the sun shining into the pool all day. Sounds complicated and expensive, doesn't it? But it's basically just a large collection of pipes and refrigerant gas, to produce what Steve Baer calls "sameshine." Nick Article 41456 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: How do you sell to the grid? Date: 28 Oct 1995 05:59:51 -0400 Organization: Villanova University Arnt Karlsen wrote: >>>if electricity goes the other way through the meter, it goes backwards? >.usually, no... Usually, yes, I believe, at least in the US, unless the meter has been modified so it will only turn in one direction. A curious fact: in large buildings, many elevators supply energy to the grid as they go down. Rarely enough to offset the building load, I suppose. This is just clever design on the part of the elevator companies, not deliberate cogeneration. Perhaps these elevators are all being operated illegally :-) Nick Article 41584 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Chimney air-air heat exchangers Date: 1 Nov 1995 08:53:31 -0500 Organization: Villanova University Does anyone use a woodstove or fireplace chimney as an air-air heat exchanger? Seems like this might work with a bare fluepipe running up through a masonry chimney, or a triple wall air-cooled "all-fuel" fluepipe with cold outside air coming down the from the outside, to a point lower than the air intake for the fireplace, to supply combustion/ventilation air which is heated as it travels down the outside of the fluepipe. I suppose this is a "counterflow air-air heat exchanger" as explained on page 3-4 of the 1993 ASHRAE Handbook of Fundamentals. If the hot flue gas enters the fluepipe at a temp Thi, say 68 F (when there is no fire) and the cold outside air enters the top of the chimney at a temperature Tci, say 32 F, and the amount of airflow is, say, 50 cfm, and the fluepipe is 6" in diameter and smooth and 16' long, what will the temperature Tco of the cold air that enters the house be, and what will the heat exchanger efficiency be? The area of the fluepipe is A = 16' x pi x 6"/12" = 25 ft^2. The U value of the smooth fluepipe surface is about 1.5 for each side, if the air and flue gases are flowing slowly, so the overall U value is 1.5/2 = 0.75 Btu/hr-F. The Number of exchanger heat Transfer Units is approximately NTU = AU/Cmin = 25 ft^2 x 1.5/2/50 = 0.375, E = NTU/(1+NTU) = 0.375/1.375 = 0.27 = (Tco-Tci)/(Thi-Tci) = (Tco-32)/(68-32), and the incoming air temp is Tco = 32 + 0.27 (68-32) = 42 F. We might do better with earth-coupled air for winter ventilation, but if we need a chimney anyway, why not use it in this way? If we roughen the fluepipe somehow and make the chimney fit around the pipe more closely, and increase the air velocity to V = 2 mph, using a small blower for incoming air, the thermal conductance of the fluepipe airfilms would increase to about U = 1/(1/Uinside + 1/Uoutside) = 1/(1/2 + 1/(2+V/2) = 1.2, and the NTU would increase to about 25 ft^2 x 1.2/50 = 0.6 and the heat exchanger effectiveness increases to E = 0.6/1.6 = .375, so Tco = 32 + 0.375 (68-32) = 45 F. We could turn on the blower when the fluepipe gets hot, with a thermostat, or when the humidity rises, in an airtight house. What will the incoming air temperature be when there is 600 F flue gas going into the chimney, and how much of this "waste heat" can be recovered in Btu/hr? One could use the formula above, substituting 600 for 68. How much wood could we save during an 8 hour fire every day over a 200 day heating season, with one of these chimneys, assuming a cord of wood contains the heat equivalent of 100 gallons of oil at 100K Btu/gallon? The outgoing flue gas temp, Tho, would come from the formula E = (Thi-Tho)/(Thi-Tci) = (600-Tho)/(600-32) = 0.375, so Tho = 600 - 0.375 (600-32) = 387 F, which is greater than 212 F, so the water in the flue gas would exit as vapor, but the creosote may condense. So the fluepipe joints should be installed "downhill," lapped so the creosote runs back into the woodstove. Does all this conflict with building codes, eg using triple-wall all-fuel fluepipe? I don't know. If it does, perhaps an exception should be made, in the name of energy efficiency. Nick Article 41714 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: This morning in the solar closet house Date: 4 Nov 1995 17:06:08 -0500 Organization: Villanova University ambient house sunspace drum sun power elec power temp (F) temp (F) temp (F) temp (F) (w/m^2) (w) 11/04 00:05 50.5 65.0 60.1 73.3 1 12 11/04 00:10 50.0 64.8 60.1 73.3 1 12 11/04 00:15 49.8 64.6 60.0 73.3 1 12 11/04 00:20 50.2 64.9 59.9 73.3 1 12 11/04 00:25 49.8 65.0 59.9 73.3 1 12 11/04 00:30 49.3 64.6 59.8 73.2 1 13 11/04 00:35 49.4 64.6 59.8 73.2 1 12 11/04 00:40 48.9 64.4 59.5 73.2 1 12 11/04 00:45 48.6 64.3 59.6 73.2 1 13 11/04 00:50 48.8 64.3 59.5 73.1 1 13 11/04 00:55 48.3 63.7 59.3 73.1 1 13 11/04 01:00 47.8 63.6 59.1 73.1 1 13 11/04 01:05 48.1 63.6 59.0 73.0 1 13 11/04 01:10 47.9 63.6 58.9 73.0 1 13 11/04 01:15 47.6 63.9 58.9 73.0 1 27 11/04 01:20 47.5 63.3 58.9 73.0 1 13 11/04 01:25 47.6 63.4 59.0 73.0 1 13 11/04 01:30 47.2 63.3 58.8 72.9 1 13 11/04 01:35 47.6 63.3 58.7 72.9 1 13 11/04 01:40 47.1 63.8 58.6 72.9 1 27 11/04 01:45 47.5 63.7 58.6 72.9 1 12 11/04 01:50 47.1 63.3 58.6 72.9 1 13 11/04 01:55 47.2 62.9 58.6 72.8 1 13 11/04 02:00 46.8 63.3 58.6 72.8 1 28 11/04 02:05 46.8 63.1 58.6 72.8 1 13 11/04 02:10 46.6 62.9 58.6 72.7 1 13 11/04 02:15 46.8 63.2 58.6 72.7 1 27 11/04 02:20 46.5 63.3 58.5 72.7 1 13 11/04 02:25 46.0 62.7 58.3 72.7 1 13 11/04 02:30 46.6 63.4 58.4 72.7 1 28 11/04 02:35 45.7 62.9 58.4 72.6 1 13 11/04 02:40 46.4 63.2 58.3 72.6 1 31 11/04 02:45 45.6 62.7 58.2 72.6 1 13 11/04 02:50 45.5 62.8 57.9 72.6 1 13 11/04 02:55 45.0 62.6 57.8 72.5 1 25 11/04 03:00 44.6 62.8 57.7 72.5 1 13 11/04 03:05 44.2 62.3 57.5 72.5 1 13 11/04 03:10 44.2 62.2 57.2 72.4 1 28 11/04 03:15 43.7 61.7 57.1 72.4 1 13 11/04 03:20 43.5 61.6 56.9 72.4 1 28 11/04 03:25 43.6 62.2 56.9 72.4 1 13 11/04 03:30 44.1 62.1 57.0 72.4 1 13 11/04 03:35 43.2 62.6 57.0 72.3 1 32 11/04 03:40 43.3 62.3 57.1 72.3 1 13 11/04 03:45 43.2 62.5 57.0 72.3 1 13 11/04 03:50 42.5 62.2 56.8 72.3 1 13 11/04 03:55 42.1 62.0 56.8 72.2 1 30 11/04 04:00 42.1 61.6 56.7 72.2 1 12 11/04 04:05 42.1 61.8 56.5 72.2 1 13 11/04 04:10 42.0 61.8 56.4 72.1 1 26 11/04 04:15 42.0 62.1 56.4 72.1 1 13 11/04 04:20 42.6 62.4 56.4 72.1 1 26 11/04 04:25 42.1 62.4 56.4 72.1 1 13 11/04 04:30 42.4 62.4 56.3 72.1 1 12 11/04 04:35 42.6 62.2 56.3 72.1 1 13 11/04 04:40 41.7 62.1 56.3 72.0 1 21 11/04 04:45 41.1 61.6 56.3 72.0 1 13 11/04 04:50 41.1 62.0 56.2 72.0 1 31 11/04 04:55 40.7 62.1 56.1 72.0 1 13 11/04 05:00 40.3 61.6 55.9 71.9 1 13 11/04 05:05 40.4 61.1 55.7 71.9 1 13 11/04 05:10 40.0 61.1 55.5 71.8 1 24 11/04 05:15 40.1 60.7 55.3 71.8 1 13 11/04 05:20 40.1 61.2 55.3 71.8 1 24 11/04 05:25 42.0 61.5 55.3 71.8 1 13 11/04 05:30 40.3 61.1 55.3 71.8 1 25 11/04 05:35 39.9 61.1 55.2 71.7 1 13 11/04 05:40 39.5 60.6 55.0 71.7 1 13 11/04 05:45 39.3 60.9 54.8 71.6 1 28 11/04 05:50 40.3 60.8 54.7 71.6 1 13 11/04 05:55 41.0 61.2 54.7 71.6 1 13 11/04 06:00 39.5 61.1 54.8 71.6 1 28 11/04 06:05 39.0 60.7 54.8 71.6 1 12 11/04 06:10 39.4 60.5 54.7 71.5 1 12 11/04 06:15 40.3 61.3 54.7 71.5 1 30 11/04 06:20 39.8 60.7 54.7 71.5 0 13 11/04 06:25 40.0 60.7 54.7 71.5 1 13 11/04 06:30 39.5 60.9 54.6 71.4 1 29 11/04 06:35 39.6 60.8 54.5 71.4 3 (dawn) 12 11/04 06:40 38.4 60.4 54.4 71.4 6 29 11/04 06:45 38.5 60.1 54.2 71.3 9 13 11/04 06:50 38.6 60.1 54.2 71.3 12 12 11/04 06:55 38.5 60.1 54.2 71.3 14 30 11/04 07:00 38.1 59.2 54.2 71.2 17 13 11/04 07:05 38.8 59.8 54.3 71.2 20 28 11/04 07:10 39.0 59.9 54.4 71.2 24 12 11/04 07:15 38.6 59.8 54.3 71.2 26 26 11/04 07:20 39.8 60.2 54.5 71.1 29 12 11/04 07:25 38.7 59.7 54.6 71.1 31 25 11/04 07:30 39.8 59.9 54.6 71.1 37 12 11/04 07:35 41.2 60.6 54.6 71.1 88 29 11/04 07:40 40.0 60.5 54.9 71.1 248 12 11/04 07:45 41.7 60.5 57.7 71.0 407 12 11/04 07:50 41.8 61.3 63.5 71.0 449 28 11/04 07:55 40.9 60.8 68.3 71.0 480 12 11/04 08:00 40.2 60.6 72.0 71.0 511 16 11/04 08:05 39.5 60.8 75.5 71.1 534 33 11/04 08:10 41.1 62.4 79.6 71.2 553 23 11/04 08:15 40.8 62.4 82.4 71.3 572 24 11/04 08:20 40.4 62.5 85.2 71.4 598 35 11/04 08:25 40.5 63.0 87.9 71.5 617 35 11/04 08:30 40.4 63.6 90.8 71.6 635 35 11/04 08:35 41.0 64.9 93.9 71.7 655 35 11/04 08:40 40.9 65.7 96.9 71.8 675 35 11/04 08:45 40.6 65.5 99.7 71.8 693 34 11/04 08:50 41.4 66.2 101.6 71.9 709 34 11/04 08:55 41.1 66.6 104.0 72.0 726 34 11/04 09:00 41.2 66.8 106.6 72.1 744 34 11/04 09:05 42.1 67.6 109.0 72.2 757 34 11/04 09:10 41.9 68.3 111.5 72.4 772 34 11/04 09:15 41.9 68.3 113.3 72.5 789 34 11/04 09:20 41.8 69.1 114.7 72.6 805 34 11/04 09:25 42.2 69.6 116.3 72.7 819 34 11/04 09:30 43.0 70.5 118.2 72.8 833 34 11/04 09:35 43.4 72.1 120.4 73.0 847 34 11/04 09:40 43.0 71.9 121.2 73.1 855 34 11/04 09:45 44.2 72.6 121.2 73.2 866 34 11/04 09:50 43.7 72.1 122.0 73.4 876 34 11/04 09:55 43.2 72.8 122.5 73.5 888 34 11/04 10:00 43.4 74.1 123.9 73.6 895 34 11/04 10:05 44.3 75.3 124.6 73.8 882 34 11/04 10:10 43.7 74.7 124.5 73.9 921 34 11/04 10:15 46.0 76.7 126.3 74.0 925 33 11/04 10:20 44.9 77.2 126.6 74.2 813 33 11/04 10:25 47.1 77.8 122.2 74.2 849 33 11/04 10:30 47.4 78.4 125.2 74.4 969 33 11/04 10:35 46.4 78.5 126.8 74.6 977 33 11/04 10:40 46.3 78.0 126.9 74.7 901 33 11/04 10:45 45.6 78.9 126.9 74.9 878 33 11/04 10:50 45.2 78.7 126.1 75.0 927 33 11/04 10:55 45.4 77.9 123.6 75.0 809 33 11/04 11:00 46.0 78.5 129.0 75.2 1029 33 11/04 11:05 47.3 80.9 130.9 75.5 868 32 11/04 11:10 46.7 80.6 123.2 75.4 854 33 11/04 11:15 46.7 80.9 126.4 75.6 898 33 11/04 11:20 47.7 81.6 124.5 75.7 796 33 11/04 11:25 48.4 82.9 127.4 75.8 959 33 11/04 11:30 47.7 83.0 129.5 76.1 992 33 11/04 11:35 48.9 83.1 127.4 76.3 676 33 11/04 11:40 49.2 82.4 116.9 76.0 507 33 11/04 11:45 45.9 80.8 122.9 76.0 990 33 11/04 11:50 45.7 80.1 122.9 76.3 686 33 11/04 11:55 46.5 81.1 125.6 76.4 1041 34 11/04 12:00 47.0 82.1 125.4 76.8 788 34 min average max Ambient temp 38.1 43.1 50.5 House temp 59.2 63.1 72.8 It looks like there is still a heat leak into the sunspace at night. For instance, at 7 AM, the ambient temp was 38.1, the average house and closet temp were about 65, and the sunspace was 54.2. If the R20 walls between the closet and house, and the sunspace, really had an effective R-value of 20, we would have R20/32 ft^2 R1/32 ft^2 = Rw = Rg 65 F -------wwww-------------wwww----------- 38.1 F | | Tsunspace = 38.1 + (65-38.1)/(Rw+Rg) x Rg = 39.2 F, not 54.2. So maybe the closet is leaking warm air into the sunspace at night. Perhaps the Tedlar film damper is stuck open, and should be replaced with something heavier, eg Teflon. Nick Article 196 of bit.listserv.Alternative.Energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.Alternative.Energy Subject: Re: Life on the grid Date: 9 Nov 1995 04:53:18 -0500 Organization: Villanova University Marge Wood wrote: >I just called the New Hampshire company, Advanced Energy Systems, Inc, that >Malcolm mentioned earlier, and they sure were surprised to hear from someone >in Texas! I asked them if they were, indeed, selling a PV with built-in >sine wave inverter that could be installed and plugged in and they said >yes, but they're still in R&D and call them back around March, so I'm >putting that on my calendar! Hmmm. Are there two companies doing this? Article: 41143 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: More on backwards lamp dimmers Date: 19 Oct 1995 16:48:27 -0400 Organization: Villanova University Today an engineer told me that he was at a DOE review meeting yesterday in Washington, DC. One of the speakers got up and showed the audience a PV panel with a line cord coming out of the back and a 110 VAC plug. He then plugged the cord into a wall socket and put the panel near a window and measured the power being fed back into the building's AC supply. The developer was apparently Solar Design Associates, a small company near Boston, and the eventual seller of this integrated small grid-tie inverter product will be Solarex, owned by Amoco. >Nick, did you ever try the idea of building a "solar hot cube" in the >form of a concrete porch with water modules (55 gal drums, old milk jugs, >whatever) set into it and built on the sunny side of the house so it could >look pretty and do something at the same time? I guess pretty-looking is in the eye of the beholder... You can make things look pretty... Why concrete, I wonder? Why not just lay a piece of plastic on the ground to keep down the dust, and put the drums on top. When they are filled with water, they won't go anywhere. This sounds like the right idea, Marge. But I wouldn't "set in" the thermal mass. To me that sounds like the concrete would conduct the heat back into the ground. The cube wants to have insulation on all sides. For the perimeter drumwall, you could lay 2 8' pressure treated 2 x 4s on the ground, 2' apart, put 4 drums on top of them, standing up, fill them with water, put two more plain 2 x 4s on top of those drums, so the outside edges of the tops and bottoms of the drums are tangent to the outside edges of the 2 x 4s, fill those drums, lay 2 more 2 x 4s on top of those drums, and 2 more horizontal drums on top, to make a 8' tall x 8' long wall. Then attach vertical 1 x 3s to the horizontal 2 x 4s every 4' along the wall (3 of them for an 8' long wall) and attach some 4'x 8', 2" thick pieces of Styrofoam to the 1 x 3s with some long decking screws. Paint the foamboard with latex or acrylic paint. (Here you can be an artist :-) to make it last a long time. Paint the south side a dark color, and attach a thin layer of polycarbonate glazing to it, 3 or 4" away from the foamboard. Put a couple of plastic film dampers at the top and the bottom of the south side. Build 3 more perimeter walls and fill the rest of the cube inside with 10 more drums. Lay two pieces of foamboard on top and put a 10' x 10' piece of EPDM rubber over that for a roof, with some rocks on top to hold it down (or old tires, if you like the AE look :-) Voila. An 8' cube containing about 42 55 gallon drums full of water. The most expensive thing is the 10 sheets of Styrofoam, $160 at 50 cents a square foot. This would store the heat equivalent of about 10 gallons of oil at 130 F. Enough for several days with no sun. I think it would make a dandy backup house heater and water heater, if combined with a low-thermal-mass sunspace... Where can you get some free 55 gallon drums near Abilene? I put a small ad in the local paper and found a company who were glad to give me 40 a month... >or would that hold too much heat? I doubt that will happen. How much is too much? >and could it be reversed during the summer? You could do some summer cooling this way, ventilating it at night, but then you couldn't make hot water for the house... Nick Article 41924 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Fuel Value / Composition of Hog Manure Date: 10 Nov 1995 06:11:02 -0500 Organization: Villanova University >Robert Tomenchok Jr (retjr@ix.netcom.com) wrote: > I heard a story on National Public Radio the other day about the plight > of North Carolina Hog Farmer's disposal of manure. It seems that they > are raising Hogs in very high density and as such, generate a lot of > hog poopies. I was thinking that perhaps the sludge might have a fairly > good fuel value, and could be dried out to a high enough solids content > for incineration in either a power or recovery boiler. They might well add water, not remove it, as in expired US Patent No. 3,933,628 (US Patents are available for $3 each from The Superintendent of Patents and Trademarks, Washington, DC 20231) "Method and Apparatus for the Anaerobic Digestion of Decomposable Organic Materials," issued to inventor Frederick T. Varani of Golden, CO on Jan 20, 1976, and assigned to Bio-Gas of Colorado. This patent describes a way to make methane in conjunction with a 100,000-cow feedlot, using 2 EPDM-rubber-lined trenches, each 700 feet long x 80 feet wide x 40 feet deep. The trenches have self-inflated translucent "solar covers" and cost $0.02 per gallon, including excavation. The feedlot generates 3.3 million pounds of manure each day, along with 6 million pounds of water and 200,000 pounds of carbon, which the digesters turn into about 7 million cubic feet of methane per day with a heating value of about 277 million Btu per hour, along with 2 1/2 million cubic feet of CO2 per day. The digesters contain heat exchangers for temperature control. The patent says: The fermentation reaction will proceed satisfactorily at any temperature between approximately 90 F and 115 F, however, between these limits many different species of bacteria become active, each in its own particular temperature zone carved out of this broader range. In other words, the digestion process is basically an equilibrium between many species of bacteria that live upon various substrates (food) and on one another. Changes in temperature cause this equilibrium to shift and some of the more temperature-sensitive species die off or become less active while others assume a more active role... Ideally, methanogenic bacteria should be kept at about 95 F and the temperature range should not be allowed to vary more than +/- 2 F per day from this base temperature if temperature shock is to be avoided. This could be an interesting municipal sewage treatment system, without the cows, or an efficient way to combine sewage treatment and long term passive solar thermal storage, for a single house, on a smaller scale. Pages 825-826 of Metcalf and Eddy's 1991 _Wastewater Engineering_ say Typical values [of gas production] vary from 12-18 ft^3/lb of volatile solids destroyed... Gas production can also be crudely estimated on a per capita basis. The normal yield is 0.6 to 0.8 ft^3/person/day (15 to 22 m^3/1000 persons/day) in primary plants treating normal domestic wastewater. In secondary plants, the gas production is increased to 1.0 ft^3/person/day... Because digester gas is typically about 65% methane, the low heating value of digester gas is approximately 600 Btu/ft^3 (22,400 kJ/m^3.)... In large plants digester gas may be used as fuel for boiler and internal combustion engines, which are in turn used for pumping wastewater, operating blowers, and generating electricity... Because digester gas contains hydrogen sulfide, particulates and water vapor, the gas frequently has to be cleaned in dry or wet scrubbers before it is used in internal combustion engines. Nick Article 221 of bit.listserv.Alternative.Energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Life on the grid Date: 10 Nov 1995 07:47:17 -0500 Organization: Villanova University David W Graham wrote: >If your porch is enclosed in glass, using water drums is in theory a >fine way to store the solar energy. There have been some passive structures >which have used passive water storage in a solarium type environment. One problem with this approach is that although glass lets the sun in, it is a poor insulator at night and on cloudy days. (Another is that you have to live inside this heat battery, so you can't charge it up to a high temperature.) If you don't get sun every day (and perhaps even if you do) it's better to have some movable insulation over the glass at night, or make the porch into a low thermal mass sunspace, by insulating the wall between the porch and the house, and moving warm air into the house (or a high thermal mass space) when the sun is shining, and blocking airflow at night. >I filled [some pots] with water and set them on the window sill... >The pots did get somewhat warm during the afternoon. But because... >of there lack of solar gain from only about 1/3 of a day of exposure, >they cooled to room temperature by late that evening. They might have become warmer with some insulation between the pots and the house to store up that solar heat at a higher-than-room-temperature, instead of letting it leak back out into the room right away. >My wife would close the curtain with the pots on the window sill >(behind the curtain) and they would get quite cold over night. The problem here is that the window is a poor insulator, and a lot of the solar heat that was stored during the day goes back out the window at night, as in a Trombe wall. Trombe walls are very poor solar performers at night and on cloudy days. This system could use some insulation between the pots and the window at night, eg an insulated wall with some dampers, separating the pots and a low thermal mass air heater or sunspace, ie the space between the insulated wall and the window. >So there was little advantage in having them in the window. In that case, yes. The house would have been warmer without the pots. You created a way to absorb some of the heat from the window (vs. letting it all come into the house) and radiate it back to the outside world at night through the window. A solar cooler :-) >I would like to try the experiment again in a south facing window. A lot more solar energy comes in south windows in the winter. About 4 times more, where I live. >But I suspect that there will never be enough storage in the little pots >to make it through the night. (A calculation I have not bothered to do.) Well, first you might define what it means to "make it through the night," using numbers :-), and then bother to do a calculation along the lines of T(t) = Tr + (T(0)-Tr) exp(-t/RC), where t is the time in hours, T(t) is the temperature of the pot at time t, T(0) is the initial temperature of the pot at time 0, warmer than Tr, the constant room temperature, exp is the "e to the x" key on a calculator, R is the thermal resistance surrounding the pots at night, and C is the number of pounds of water in the pots. Then you might look up how much sun comes in a south window on an average winter day where you live. Where I live, that's about 1000 Btu/ft^2/day, and the average outdoor temp is about 32 F, so if the pots were sitting behind a 1 ft^2 low-thermal mass sunspace on an average day, and the R-value of the glazing were 1, and the pots contained a lot of water and surface area, and there were perfectly insulating walls surrounding the pots at night, and the winter sun shined for 6 hours a day, the constant water temperature T(0) would come from the formula 1000 Btu = 6 hours x (T(0)-32F) / R1, or T(0) = 32 + 1000/6 = 198.7 F, almost boiling. To make that situation a bit less ideal, suppose the pots contain 24 pounds of water, and they are surrounded at night by an R10 wall, say a 1' cube made with Stryofoam 2" thick, and the surrounding room is 68 F all the time. Then 1000 Btu = 6 hours x (T(0)-32F) x 1 ft^2/R1 + 18 hours x (T(0)-32F) x 1 ft^2/R10 + 24 hours x (T(0)-68F) x 5 ft^2/R10, = 6 x T(0) - 6 x 32 + 1.8 x T(0) - 1.8 x 32 + 12 x T(0) - 12 x 68 = 19.8 x T(0) - 816, so T(0) = 1816/19.8 = 91.7 F, and R = R10/6 ft^2 = 1.67, so RC = 24 x R = 40 hours. If the pots had a temperature of 91.7 at say, 3 PM, then at 9 AM their temperature would be T(15) = 68 + (91.7-68) exp(-18/40) = 83.1 F. >\)/ David W. Graham (970) 491-8945 | 1500 W. Plum St. >~O~ Graduate Student in Mechanical Engineering | Apt 6-O Really? :-) Nick Article 3970 of bit.listserv.geodesic: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: slenderness ratio Date: 29 Nov 1995 11:20:45 -0500 Organization: Villanova University From some email to Tagdi, after his posting with some some numbers that indicate that some metals are stronger in compression than tension... >>I'm not sure you have the whole picture here, but it's a good start. Look up >>steel, especially piano wire... Metals are often used in long thin strands, >>ie wires or cables or rods, which are strong in tension but very weak in >>compression, because the strands buckle. Look up "slenderness ratio" for >>a column... Another way to verify that long thin pieces of metal are stronger in tension than in compression is to unbend a wire paper clip or coathanger into a straight piece of wire. Then try to pull the wire apart, holding the ends in your hands. Impossible. But, if you push on the wire from each end it will buckle or fold up easily. This is more of a geometric property of materials than a matter of the basic strength of the material. When wood is used as a column or post, in compression, it is considered to be as strong as the wood itself for a short column, but a lot weaker in a long column. In the case of wood, the difference between "short" and "long" happens when the ratio of the length of the column to the thickness of the column exceeds about 12:1; the number 12 is the critical "slenderness ratio." For example, a 1" x 1" column of wood might support 1000 psi in compression, and it might have a "modulus of elasticity" E, of 1,000,000, and it might be used to hold up 800 pounds. How long can the column be, if it has no side-bracing to keep it straight? I have a book that has a calculation, from Euler, who said that if a column is so long that when you bend it a little bit, the new forces on the column make it bend more, then the column is too long to be safe. This "Euler limit for buckling" requires that for a column of length L and thickness D, the compressive stress in the wood, C, be less than 0.3E/((L/D)^2). So L^2 < 0.3ED^2/C, or L < square root(0.3(10^6)(1)^2/800) = 19.36" above. So even though the wood itself in this column can support 1000 pounds, it cannot stably support 800 pounds, if the post is more than 19.36" long... If it were 16' long, it could support about 1000 pounds hanging from the bottom, but it could only hold up about 8 pounds, before it became unstable in buckling. Materials in tension don't buckle, so they don't have this critical "slenderness ratio" limit on their strength. Bucky talked about this... Nick Article 4038 of bit.listserv.geodesic: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Solar economics Date: 3 Dec 1995 07:37:35 -0500 Organization: Villanova University James Fischer wrote: > Tagdi said: >> I want to bring Nick Pine into this. He told me that solar >> energy is not economical these days, > Well, that seems strange, given that Nick seems to know > all the basic math required to make solar-driven systems work. He thinks he does :-) He finds it easy math, compared to geodesic geometry. Mostly just arithmetic, with an occasional push on the e-to-the-x button of his calculator... Would that more geodesic geometers discover this easy math. He'd be happy to help, in exchange for some geodesic math tutoring... > One would hope that he could do some math with dollar signs in front, He does that a lot. Lately he is impressed by labor rates for house builders, who seem to charge almost as much as lawyers these days. I guess we need more tooling and prefabrication, if not do-it-your-selfery. > and figure out how to justify the investment required to implement a design. I'm not sure what that means, exactly. _I_ think some solar heating investments are quite well justified, and my house is already mostly solar heated, but where are the rest of the people who want to build things? That's another step. As I already said, one way to make solar heating economics look nicer is to combine it with something else, eg walls. In _How Buildings Learn_, Stewart Brand says: The 80-story Amoco building (1974) in Chicago was originally faced with 1 1/4-inch-thick panels of prime Carrara marble, which soon dished and distorted because it was cut too thin. Replacing the 43,000 panels with 2-inch thick granite is taking three years and $80 million. I suppose photovoltaic walls are cheaper than marble facades: Article: 43011 of sci.energy From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: AC PV panels Date: 3 Dec 1995 06:22:24 -0500 Organization: Villanova University Tom Gray wrote: >Nick Pine writes: >>Solar panels with built-in inverters that plug into wall sockets >>to lower electric bills should be coming quite soon. MrSolar@netins.net (Charlie Collins) kindly forwarded the following from http://www.ultranet.com/~sda, paraphrased below with a few comments... Solar Design Associates is now developing an AC solar module with Solarex, owned by Amoco. The AC module is a DC module with a small integrated inverter. Solarex calls the product "PowerWall." The first modules are designed for curtain walls, the shear wall systems used on modern office buildings. These modules replace the glass or other sheet material used in curtain walls, eg in framing manufactured by Kawneer of Norcross, Georgia. A residential roof product is also in the works. PowerWall modules are available in AC and DC models, in sizes up to 53" X 87", [32 ft^2--why not 4' x 8'?] with outputs up to 250 watts. An ideal solar system should harvest both heat and electricity from the same aperture [although PV power falls off as temperature rises...] Virtually every building has thermal as well as electrical energy needs, and roof area is limited... In 1979, SDA developed a combined, flat-plate, PV/thermal collector. The device worked well. Unfortunately, no company was willing to produce it. Now they are revisiting this device... [I wonder if it still has a thermal output?] In 1980, existing PV modules (~ 4 ft^2) were not large enough to integrate well with building systems. Too many connections were needed to make a significant electrical output. SDA presented the case to all major PV makers for building a large-area module of 25 to 30 square feet, which could be integrated into a building skin to form the structure and weathering surface. Every manufacturer thought they were crazy - except one. SDA began working with Mobil to develop a 24 ft^2, glass-superstrate PV module which could be sold with or without a frame. Now the rest of the industry is following suit. Custom module manufacturers in Europe now offer PV modules of 3 square meters and larger, designing them to architect's specifications for direct building integration. DC outputs of PV arrays impose serious limits on the electrical use. Most electrical loads require AC power, and 30-40% of the cost of a PV system has been used in the transition from the DC PV module to the load. Such systems were complex and required special DC-rated components not readily available. The obvious answer was to create an AC PV module. SDA is now doing that now. --- > My model is simple - let's say the house of your dreams would cost > $100,000 US. OK... > Let's be really depressing, and estimate the cost of the same house, > after designing in "energy autonomy", to be $150,000 to $250,000. Houses need siding and roofs, right? Suppose we use thin polycarbonate plastic in place of siding and roof, with an airspace underneath, to collect some sun. No sheathing, no tarpaper, no shingles. Less labor, since these plastic sheets come in very large pieces and rolls... So to my mind, a solar heated house can be LESS expensive to construct than a conventional house. I wouldn't make the roof out of PV panels, yet... But let's say you did, and it cost another $50-150K... > Now, over your lifetime, will you EVER have to pay a total of $150,000 > for energy? No way in hell! Even if your "energy bills" ran $200 per > month, you could pay them for 62 years, and be under the extra $150,000. Yes, although that is future money, and some economists argue that energy costs rise faster than inflation. > BUT... Yes? > Most people have a mortgage, and pay interest on their home loan. > The way mortgages work, people end up paying them off in either > 30 years, or 15 years. Let's be optimistic, and say that you can > get a 6% interest rate on the loan... > > 15-yr model 30-yr model > > Cost of House $100,000 $100,000 > Monthly Payment $843.86 $599.56 > Number of Months 180 360 > Total Payments $151,894.80 $215,841.60 > > Gee, isn't that nice? It seems that FINANCING the silly > roof over your head is not economical. In what sense, exactly? It seems to me that deciding to buy a house is different from deciding to invest in a stock or put money in a savings account. People live in houses. It's hard to live in a bank account, no matter how much interest the bank pays. Mortgage "payback" is not the same as investment "payback." When I talk about solar economics, I'm thinking that most people are making decisions about where to invest money, or whether to borrow money to do something that has a monetary return. I suppose that most people would rather put money in a bank, rather than buy a solar system, if the bank deposit pays equally well, and has a lower risk and takes less time to manage. > So, if we pay no interest... I'm not quite following you here. I thought you were talking about 6%. If you put up the cash out of your pocket up front (is that what you are talking about?), you forgo the opportunity of putting it in the bank and earning some interest. > we can afford the extra cost of investing in stuff that "pays us back" > by reducing or eliminating our long-term need to pay bills to the power > company, water utility, sewer utility and such. My original point with Tagdi was that if a "solar heater" allows you to avoid paying the oil dealer for 1 gallon of oil per square foot of "heater" per year, about 60 cents, where I live, the "solar heater" has to be very inexpensive to build, OR it has to serve more than one purpose, to make this kind of narrow economic sense to the owner. Nick Article 43021 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: sunspace plans Date: 3 Dec 1995 15:44:19 -0500 Organization: Villanova University Now that winter is upon us northern hemispherites, I've finally gotten around to answering some people who asked me by email about possible sunspace additions to their houses, and sent little ascii sketches. I'm posting my replies. Perhaps some other people can find a useful idea or two here... Hello T: Just getting around to some older email, finally. >I've been following your posts and trying to see how I could fit something >onto my own house. Let me throw some ideas at you and see if they stick :) OK... >I have a room that was added onto the south side of my house that looks like: +---------------------------------------------------------+ | | | | | | |15' W ^ | W | | W N | W | 23' | +----------WWWWWWW----------------------------------------+ 6' T T = Tree Is the wall of this room 8' high? Perhaps you can also paint the roof with white or aluminum paint to make it into a reflector and add a solar air heater to the second floor south wall of the house... Or even add a sunspace on top of the roof of the new room, if it's fairly flat... >My thoughts are to add something where the window is now, using the window as >the top opening and punching a hole at the bottom for the lower vent. This >would make it a much easier project for me to fly past the family. I guess so :-) Altho that's a pretty small solar collection area. You can recover something like the heat equivalent of a gallon of oil per square foot of glazing per year... Perhaps you could start with that, and if it works, make a lean-to sunspace/ greenhouse along the whole south side. Or maybe just from the east edge of the window to the NE corner of the house. You have an easier retrofit than M. I'll insert what I sent him below... Greetings M: >Some ways to improve my house are pretty obvious: it has a sheltered >concave corner facing South where I'd love to put an attached greenhouse >which would capture a lot of solar heat in Spring and Fall which could be >distributed to the house via a fan. Sounds good to me. >Above that greenhouse I could mount a thermal collector panel. That sounds expensive, altho the homemade version wouldn't cost much, made by screwing some boards on the roof on 4' centers to make a 3" airspace and attaching a thin layer of polycarbonate plastic over that. >All this seems obvious, but I don't know the costs, except that they're high. Not necessarily. Polyethylene film costs about 5 cents per square foot, and lasts 3 years. If you make a framework out of 2 x 4s and only attach the film at the ground and the peak and the sides of the structure, using aluminum extrusion clamps, the whole thing can be inexpensive, and it's easy to change the film every 3 years. Standard commercial poly film greenhouses sell for as little as 50 cents a square foot, and 3 people can put up a 30' wide x 100' long commercial greenhouse in 1 day, from scratch. Like a tent. Find a local supplier to commercial greenhouse growers and check out pipe-frame poly film greenhouses. You don't give dimensions below, but I'll take a guess... windowless North steep-sloping roofing --------------------------------- | 32'? | some | | some windows | | windows on this | TOP VIEW | here side | | too |24'? | | | side view | | of this side | | below | | | | -----------------------|--------- | | steep-sloping | | | roofing-type material | | | |16'? | no windows at all | | in this corner area | | | | | | | 16'? | -------------- - - - - - - - - - <------------- large windows | here already How about extending the sunspace out to make the house a big rectangle, so you don't get afternoon shading from the existing southwestern protuberance? >CRUDE side view looking from East side: --------------------- / ----- ----- \ --------------/ | | | | \ | / ----- ----- \ | / \ | / ---- ---- ---- ---- \ | ---- / | || || || | \ | h | ---- ---- ---- ---- | ------------------------------------------- Looks like h is very small. Does the roof really come to within 2 or 3' of the ground? >What I think should be done: --------------------------------- | | | | | | | TOP VIEW | | | |.................................| | | | This is all potential solar area| | too. Some poly film over the | | roof, to make a big air heater? | | Or take off the shingles first. | A solar attic? --------------------------------- | | | | | | | | |-- greenhouse | | | | ditto |--------- The poly film could go over the | | existing roof, extending the life of the | | roof, perhaps. Or perhaps melting or | | curling up the shingles :-( The polyethylene -------------- film or polycarbonate plastic might be removed someday to expose the original roof, more or less intact, if you decided to do that for some reason. solar panel__ --------------------- \ // ----- ----- \ ------------\// | | | | \ | // ----- ----- \ | -----*-/ \ | / * / ---- ---- ---- ---- \ | | * / | || || || | \ | | * | ---- ---- ---- ---- | ------------------------------------------- | \__ greenhouse Another possibility is to just extend the roofline down to the ground (*), with glazing a few inches above the roof, and parallel to it, or a little more horizontal, so there's more sunspace floorspace on the ground. Or use some curved steel pipes from commercial greenhouses, 20' long, $35 each, on 4' centers, with their straight ends touching the ground and their curved ends attached to a horizontal board near the peak of the roof. The greenhouse would be a bit less complicated to build without that kink in the roofline that you drew at the top of the south wall... >There are some details to work out, e.g., what kind of foundation... Perhaps some railroad ties on the ground with a couple of holes in each one and 4' of 1/2" rebar driven into the ground through each hole... Or a pressure treated 2 x 6 pipe sandwich along the ground. >how to store the heat there, It's best to store the heat in the house. If the greenhouse/sunspace is not too big, most of the heat will be usable in the house. A 16' wide x 16' tall sunspace can provide about 200K Btu/day to an attached house, about the same as 2 gallons of oil on an average day. How much heat does your house need on an average winter day? I think of greenhouses as being warm at night, and humid, BTW, and sunspaces as being cold at night and dry, with much less thermal mass. Much more energy-efficient. If you really want to store the heat in the sunspace, it can be done, but ideally you need some insulation between the thermal mass and the glazing, so warm air can flow through to the thermal mass during the day, but not at night, so the thermal mass stays stay warm at night, while the airspace just inside the glazing gets icy cold quickly, losing little heat to the night. >and how to cover it in summer to avoid overheating, A big piece of 80% greenhouse shadecloth with grommets to hang it up, made to order in a week for 20 cents a square foot or so... This would make the glazing last longer too. It's good to hang this inside the sunspace in the winter. >and how to avoid losing heat from the house to the greenhouse at night Blow warm air into the house from the sunspace during the day, through some passive plastic film dampers that close at night. Let the currently insulated SE and SW walls of the house keep the heat inside the house itself at night. Hope this helps... --- Back to T: >This tree is in the way of the afternoon sun and is about 6 ft out from the >house. This tree is also one that does not drop its leaves in the winter. >It's not a very big tree, 6" at the base and maybe 12 ft high. Yuck. I'd cut it down and use it for a Christmas tree, or move it to the north or west side of the house, and plant some vines or clematis or beans or grapes or something along the south wall for summer shading. >If I added on something like what you've described here or your earlier >posting of the "Fall Project", I wonder much of an impact that tree is going >to have. If you have something along the whole wall to the east, the tree won't matter much. If your solar collector only covers the window, the tree might cut the solar gain by a third or a quarter. Midwinter sun arrives from south +/- 45 degrees, at a low angle, with a maximum elevation of 17 degrees from the horizon on 12/21, where I live. >Instead, I'd buy 9 20' curved galvanized steel pipes from Stuppy or X. S. >Smith in New Jersey for about $250, put them up on 4' centers, burying the >straight end of each pipe in the ground and attaching the other end to a >horizontal board under the eave of the house. >Why steel? Why not PVC? I can't get a true curve with PVC but I can have a >pair of 45 degree corners. Seems like this would be much cheaper. PVC rots polyethylene in contact. If you wanted something cheaper, how about long 2 x 4s or 2 x 6's, painted white so they don't heat up in the sun and deteriorate the poly film? Also: >Then I'd attach a large sheet of 5 cent/ft^2 3-year greenhouse poly film >perhaps Jade Mountain's 5-year, 43 cent/ft^2, Tuff-Glass, which comes in 48" >x 144' rolls >Another glazing option is Dupont's heat-sealable, clear, UV-transparent, >Tedlar PVF film, which is very strong and light, and should last about 10 >years. Are these listed in increasing order of durability? I think so. And cost. 1 mil tedlar costs about $35/pound (?), and a pound is about 200 ft^2, but the catch is that Dupont has something like a $5K minimum order. An AE distributor could help with this problem. The poly film is also much easier to attach, since it comes in huge pieces. >How durable is the poly film? Greenhouse UV poly film is guaranteed for 3 years, it comes in pieces up to 30' wide and 100' long, and it's about as easy to change as a bedsheet if you attach it with aluminum extrusion clamps ($1/linear foot.) It IS recyclable. And: >>For moving more air, I like the $12 K-Mart 3-speed slimline HABF-20 20" box >>fanmade by Holmes (1-800-5-HOLMES) in China. I'd put the fan in series with a >>room heating thermostat and a sunspace attic fan thermostat. >Why two thermostats? They go in series with the fan, to turn on the fan when the sunspace is warmer than 80 F and the house is cooler than, say 70 F. My favorite thermostat is now Grainger's 2E158, $14.03, which can be used for heating or cooling. It has a powerful switch too: 115-277 VAC at 22 amps. >This room is about 23x15 and is where we spend most of our time as a family. Aha, dimensions :-) So the south glazed area is potentially 23 x 8', if it's one story tall. This might save you 200 gallons of oil a year. If the sunspace were two stories tall, touching the eave of the roof of the new room, and running up to the peak of the (2 story) house behind it, it might save twice that. If it goes all the way up to the peak of the steep south roof of the main house, it might save 600 gallons of oil a year. If it has a shallow reflecting pond along the south edge, extending out 16 feet or so, it might save 50% more. >We only have 2 windows so I would like to keep as much sunshine as possible. >This room was added on by a previous owner and does not receive heating or >cooling as well as the rest of the house (long runs of ductwork). Sounds like a perfect place to add on a sunspace. Maybe another window while you are at it... >Thanks for the ideas, and keep posting these small projects/ideas that >the average Joe can try. Thanks for the encouragement :-) Nick Article 4158 of sci.engr.heat-vent-ac: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Question about Heating a Home Date: 14 Dec 1995 06:03:37 -0500 Organization: Villanova University paul milligan exemplifies: > Let's create an example - take 1 lb of water, in a container with 0 R >value. Heat it up from 50 to 100 degrees. That takes 50 BTU's, right ? I guess you would have to put the whole container in an oven to heat it up, if it had 0 R-value... Heat sinks have close to 0 R-value... The R-value of a slowly moving air film near a smooth surface is about 2/3, in English units, which would be most of the overall R-value of the container, if it were made of a thin piece of metal, or a paper cup. > With no setback, there will be an identifiable rate of heat loss to the >surrounding 50 degree room. Yes... >You will need to continuously add 'x' BTU's to that water to keep it at 100. Where x is infinity :-) Breeng zee beeeg torch... Suppose the container is a cubical box with a lid, with an edge length of s = 4", ie 1/3 foot. If the cube is sitting in midair, its resistance will be about 6 s^2/(2/3) = 1 "Ohm," so we need to add 50 Btu/hour to keep it at 100 F in the 50 F room. >Let's say it wants to cool down at 25 degrees per hour. That would make it want to be slightly smaller, with a thermal resistance of 2 Ohms and an edge length of 2.83". (A cube like that would only hold 0.8 pounds of water, but let's ignore that.) > _With_ setback, there will also be an identifiable rate of heat loss. >It will start at 25 degrees / hr. One hour later, with the water at 75 in >your 50 degree room, your heat loss rate is cut in half. One more hour, >and your heat loss rate is zero, as the water and the room are both at 50. The time constant of this heat battery is 2 Ohms x 1 lb = 2 hours :-) After time t has passed, the water temp will be T(t) = 50 + (100-50) exp(-t/RC). After 1 hour, the water temp will be T(1) = 50 + (100-50) exp(-1/2) = 80.3 F. After 2 hours, the water temp will be T(2) = 50 + 50 exp(-1) = 68.4 F. If we make the cube an EPDM-rubber-lined plywood box, 8' on a side, with a foot of insulation, ie R-40 sides, with a 6' cube of water weighing 13,500 pounds inside, then RC = 40/(6x8x8)x13500 = 1872 hours or 78 days. If the water began at 100 F, after 1 hour in a 50 F room it would have a temp of 50 + 50 exp(-1/1872) = 50 + 50 x 0.99947 = 99.97 F. It would cool to 68 F in t = -RC ln((68-50)/(100-50)) = 1913 hours or 80 days... We might make the south face of this cube dark and glaze it with thin plastic over an air gap, and add a $100 10" x 10" Honeywell 64LS damper and 6161B1000 motor that opens to the inside of the cube when the sun shines, and replace the EPDM rubber tank with 18 sealed plastic 55 gallon drums full of water... The average outdoor temp in December in Philadelphia is about 32 F. On an average December day, 1000 Btu/ft^2 of sun falls on a south wall, in about 6 hours. How hot will the cube get, sitting outdoors, or inside the house, behind a window? I agree with you, Paul, setbacks do save energy. Nick Article 4160 of sci.engr.heat-vent-ac: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Question about Heating a Home Date: 14 Dec 1995 12:37:22 -0500 Organization: Villanova University Nick Pine wrote: :If we make the cube an EPDM-rubber-lined plywood box, 8' on a side, with a :foot of insulation, ie R-40 sides, with a 6' cube of water weighing 13,500 :pounds inside, then RC = 40/(6x8x8)x13500 = 1872 hours or 78 days. If the :water began at 100 F, after 1 hour in a 50 F room it would have a temp of :50 + 50 exp(-1/1872) = 50 + 50 x 0.99947 = 99.97 F. It would cool to 68 F :in t = -RC ln((68-50)/(100-50)) = 1913 hours or 80 days... :We might make the south face of this cube dark and glaze it with thin plastic :over an air gap, and add a $100 10" x 10" Honeywell 64LS damper and 6161B1000 :motor that opens to the inside of the cube when the sun shines, and replace :the EPDM rubber tank with 18 sealed plastic 55 gallon drums full of water... :The average outdoor temp in December in Philadelphia is about 32 F. On an :average December day, 1000 Btu/ft^2 of sun falls on a south wall, in about :6 hours. How hot will the cube get, sitting outdoors, or inside the house, :behind a window? Crudely assuming that the water and the air in the passive air heater and the "solar closet" all have the same temperature T when the sun is shining, the R40 wall insulation value includes thermal bridges, the glazing transmits all of the sun and none of the heat by radiation, and it has an R-value of 1, then on an average December day, the energy that goes into the box is Ein = 1000 Btu/day x 64 ft^2 = 64K Btu/day, and the energy that leaves the box is Eout = 6 hours x (T-32F) x 64 ft^2/R1 for the south face, daytime + 18 hours x (T-32F) x 64 ft^2/R40 for the south face, nightime + 24 hours x (T-32F) x 64 ft^2 x 5/R40, for the other 5 cube faces. So if Ein = Eout, then 64K = 64 x (6 + 18/40 + 24x5/40) x (T-32), or equivalently 1K = (6 + 9/20 + 3) x (T-32), or equivalently T = 32 + 1000/9.45 = 32 + 105.8 = 137.8 F. If this ideal cube were sitting inside a house, the water temperature would be T = 68F + 105.8F = 173.8 F. After a week, the water temperature would be T(168 hrs) = 68F + (173.8F-68F) x exp(-168hr/1872hr) = 164.7 F. If there is snow in front of the window, or some other 50% reflective surface, the water temperature would be T = 68 + 1.5 x 105.8 = 226.7 F. If the ideal cube were a long EPDM-rubber-lined plywood box full of water with a transparent horizontal top and an insulating/reflecting movable cover, lying along the north wall in the line focus of a 5:1 linear parabolic concentrating 80% reflector, the "water temperature" would be something like T = 68 + 5 x 0.8 x 105.8 = 491.2 F :-) And the water would be quite warm even on this gray day, with 3" of fresh wet snow on the ground outside. Nick Article 43627 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.architecture.alternative,alt.solar.thermal,bit.listserv.Alternative.Energy,sci.engr.heat-vent-ac,alt.home.repair,alt.energy.renewable Subject: A passive window solar collector Date: 17 Dec 1995 09:31:35 -0500 Organization: Villanova University Lines: 104 Message-ID: <4b19k7$i6@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:43627 bit.listserv.Alternative.Energy:677 sci.engr.heat-vent-ac:4190 Would someone like to experiment with a convective air loop window heater with no dampers, that makes heat for a house during the day, and insulates the window at night? This might make for an interesting paper or science fair project... Windows are big heat leakers, compared to most walls. Malcolm Wells used to leave very nice looking interior foam/stucco panels in place all winter over the windows of part of his underground office in Cherry Hill, NJ. My friend Tom minimizes his heating bill dramatically by pushing plain foamboard into most of his house windows in the winter. But it would be nice to have a small transparent opening in the foamboard to let some daylight and solar heat in from the south windows... Perhaps like this: view from room side view | wall | | | --------------------------- --- |--------------| | air | foam | air | |/ . <== cool air in | in | board | in | | . . |---------------------------| | | /--------- | | air | | | | warm air out ==> | | out | | | | | | ------------ | | | a| | | vent area Av | | | | a | | | | | | a | | | | | | | a | | | | | | a | | | foam | | | | a | | | board | | | a | f | | | | | | a | o | | | | | a | a | | | H |<-G->| a | m | | | | | a | | room | window area A | | | | a | b | | | | | a | o | | | | | | a | a | | | | | a | r | | | | | | a | d | | | | | a | | | | | | |a | | | | | | | | | | |\ /| | --------------------------- --- |--------------| | | | wall | | | Steve Baer suggests trying out a very simple passive system in which the sun shines through an outer layer of glazing, then through an inner layer of glazing onto an absorber surface. There would be an air gap of dimension G between the outer and inner glazings, and another air gap between the inner glazing and the absorber. As I understand it, cool house air to be heated would somehow be persuaded to flow down between the cold outer glazing and the inner glazing, then up through the air gap between the inner glazing and the absorber. This tends to be more thermally efficient than a system in which solar heated air is in contact with the cold outer glazing. There would be some insulation behind the absorber, between the absorber and the room. No backdraft damper would be needed, because at night the cold air would form a stagnant pool that stays behind the insulation, since cold air sinks. The width of gap G determines the airflow resistance, in part. Steve suggests that G might want to be on the order of H/15. The vent area Av might want to be about 5% of the window area. The absorber might be one or more layers of black aluminum window screen, with an absorbing area of something like 5 times the window area, large enough so that most of the heat from the absorber is transferred to the flowing air, vs having a small-area hot absorber that loses a lot of heat to the glazings by radiation. One measure of success is glazing and absorber temperatures, the lower the better. One way to measure these temperatures is to use Exergen D501 scanning thermometer (about $1000.) One way to look at the airflow is to blow some smoke into the collector. The useful heat output of the collector is proportional to the product of the air velocity and the temperature difference between the input and output air. Steve suggests that 50% solar collection efficiency is a good target. Perhaps we will see a commercial product someday, a clever reversible storm window, in which the summer screen doubles as a winter solar absorber. Nick Some useful rules of thumb: Q (cfm) = 16.6 Av sqrt(H delta T), for a chimney, in which Av is the smaller vent area in square feet, H is the chimney height in feet, and delta T is the input/output air temp difference (F). U = 0.174E-8 Ac (T+460)^4 Btu per hour is re-radiated by an Ac ft^2 surface at temperature T (F). Full sun is about 300 Btu/ft^2/hour. 1 Btu will heat about 55 ft^3 of air 1 degree F. Steve would doubtless be happy to hear of such experiments, at Zomeworks P O Box 25805 Albuquerque, NM 87125 Article 4231 of sci.engr.heat-vent-ac: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Home Insulation - Plan of attack? Date: 20 Dec 1995 13:01:17 -0500 Organization: Villanova University Mike Andresen wrote: >I live in a single level 1700 ft2 home in Phoenix. With 1700 ft^2 of ceiling and 1700 ft^2 of walls, as you said, and perhaps 200 ft^2 of windows? >I have R=11 in the >ceiling, nothing in the block walls (R=3) and single pane windows (R=0.9). Let's see, if it's 68 F inside and 32 outside, how much heat is flowing through each part of the house each day? Roughly: Before After ceiling: 24(68-32)1700/R11 = 134 K Btu ---------------> 48 K walls: 24(68-32)1500/R3 = 432 K Btu (wow) 68 K windows: 24(68-32)200/R.9 = 192 K Btu 86 K air infiltration: 24(68-32)1700x8'x2/55 = 214 K Btu/day 112 K Total 972 K Btu 314 K How about putting 4" of Dri-Vit on the outside of the block walls, or the water-based equivalent system? That would leave the thermal mass of the block inside the house, and increase its time constant to about 3 days, so you could solar heat this Phoenix house with windows or some sort of low-thermal- mass sunspace... You might put some holes in the tops and bottoms of the walls inside the house to increase their heat transfer area. This would cost about $2/ft^2 for the materials, and make the walls about R19 instead of R3, reducing the heat loss to 68 K Btu/day, for a net savings of about 100 Btu/32F day/$ materials invested. You might make it look like adobe, carving and painting some little brown foam poles to stick out of the eaves. Another layer of glazing might cost another $/ft^2, making the windows R2, and reducing their loss by about half, to save about 500 Btu/$. >I am wondering if it is worth while to add another insulation layer in the >attic to make R=22 up there when the walls and windows are less than R=3? I think these things are only related by marginal economics. Adding some 25 cent/ft^2 R-19 fiberglass in the attic would reduce its loss to 48K Btu saving about 200 Btu/$. Adding another R11 would cost about 15 cents/ft^2, saving 250 Btu/$. Some 15 cent/ft^2 foil, 4' wide, would help more in the summer, but not so much in the winter. And plugging up holes in the house to reduce air filtration from 2 air changes per hour to 1 is labor intensive but rewarding. $20 worth of caulk might save 112K Btu, ie 5000 Btu/$. This becomes the largest heat leak, after the house is better insulated. If you do all these things, you can probably heat your house 100% with a low- thermal-mass sunspace with about 300 ft^2 of glazing. Say, a $400 commercial plastic film greenhouse, 8' tall, extending 36' along the south wall, with fresh red tomatoes and basil growing inside:-) Nick Article 4260 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.engr.heat-vent-ac Subject: Re: Electrically efficient oil burner available? Date: 22 Dec 1995 09:17:52 -0500 Organization: Villanova University Lines: 159 Message-ID: <4beemg$ghp@vu-vlsi.ee.vill.edu> References: <4ba2lk$pgv@dca.net> <4baqjp$48r@nn.fast.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Fred A wrote: >> amuller@dca.net (Alan Muller) writes: >> I'm concerned about the electrical consumption of my oil >> burner "gun," though I have yet to measure the consumption. >Nothing is free. If you had a gas or electric hydronic system you would >still have the circulator pump, and the zone valves. With gas you may >still have the vent damper, burner motor; and, or other accessories. >Electrical consumption for heating systems is a fact of life, and not >a big deal... It is for us energy misers :-) The sun is free, and plastic film backdraft dampers use no electricity. If the only electrical power used in your mostly passive solar heating system is to move two Honeywell MLS642LS dampers and D6161A1001 actuator motors, with limit switches so they only consume two watts when they are moving, that's pretty close to free :-) Solar closets in a nutshell: Important points: o Glass is a very poor insulator, compared to an insulated wall. o Trombe walls are very inefficient, because they store heat behind glass, and that heat leaks back out to the cold outdoors all night. o Low-thermal-mass sunspaces, eg those made with thin polycarbonate glazing, make better solar heaters than Trombe walls. We want an insulated wall between the sunspace and the house, and dampers in about 5% of the insulated wall, or perhaps fans (1-2 cfm/ft^2 of glazing) that move warm air from the sunspace into the house on sunny days. The sunspace fan or motorized damper should be in series with a cooling thermostat in the sunspace and a heating thermostat in the house. At night, the sunspace should get icy cold, leaving the heat stored inside the house, in the thermal mass of the house. o Water stores 3 times more heat than masonry by volume, with lower thermal resistance, so a box full of water containers can have 1/3 the volume of a rock bed, and lower airflow resistance as well, so it can transfer heat better by natural convection, or with minimal fan power, vs a rock bed. o It is good to have a separate heat battery, so we can charge it up to a high temperature on sunny days, and discharge it in a controllable way to heat the house to a constant temperature during a week of cloudy days. If we _live inside_ the heat battery, we cannot do that... o The heat battery should have some sealed containers of water, and the total surface area of the water containers should be 5-10 times that of the glazing. o Ohm's law for heatflow tells us how much heat we need for a house on an average day. U = hours x (Tin - Tout) (sum of A's over Rs) Beware of thermal bridges! o This tells us how much low-thermal mass sunspace glazing we need, since each square foot of sunspace glazing gathers about 1000 Btu or 300 watt-hours on an average day. o The daily heat loss also tells us how much water we need in the heat battery--enough for 5 days without sun, say (this needs further study.) A pound of water raised 1 degree F stores 1 Btu. o Solar closets can also heat water for houses, and serve as saunas or clothes-drying areas. Other points: o What's wrong with Trombe walls? (They are 25 times less efficient than low-thermal-mass sunspaces.) o What's wrong with direct gain houses? (Large temperature swings from day to night, steadily decreasing temperatures over a few days without sun, large backup heat requirement in cloudy climates, lack of privacy, excessive glare, can't put rugs on the floor, expensive masonry construction, no solar water heating, "optimal ratio of glass to floorspace" dilemma, etc.) o Temperature swings in a solar house (U delta t = C delta T, RC time constant) o What's wrong with "solar panels"? (Expensive, need pumps, antifreeze, heat exchangers, roof climbing--> broken bones, roof mounting-->inefficient, surrounded by cold air and wind, with back losses lost to ambient, vs back losses that heat the house, roof mounting-->leaks in roof penetrations and reroofing difficulties, roof mounting-->expensive rigid framework and installation labor, etc, etc.) o Efficiency vs. cost-effectiveness (Do you want a Mercedes or do you want transportation?) o What's wrong with PV? :-) (100 times less cost-effective than passive solar) o Ohm's law for heatflow (U = (hours)(Tin-Tout) x area/R-value) o Heat capacity and storage (Rocks, 22 Btu/ft^3/degree F Water, 62 Btu/ft^3/degree F Air, 0.02 Btu/ft^3/degree F A cubical solar closet L feet on a side has a time constant of L^2 days.) o Why water vs. rocks? (Cheaper, easier to move, lower thermal resistance, 3 times more heat capacity, lower airflow resistance.) o Why fans vs. blowers? (Blowers use hundreds of watts. Fans use 10s of watts.) o Is it wrong to waste solar energy? (No, if using a bit more sunspace glazing and a hotter sunspace lets one use a damper instead of a fan, and no, if it costs less to underinsulate the sunspace wall and open a house cooling damper during the day.) o Why dampers vs. fans? (Some motorized dampers only use 2 watts when moving, and zero watts in a fixed position. Using these with thermostats allows very accurate room temp control, with very little electrical power consumption.) o Convective loop heat flow (The amount of air in cfm that flows through a damper in an unrestricted chimney with height h feet and openings of Ad ft^2 at the top and bottom and a temperature difference of delta T from top to bottom is approximately Q=16.6 Ad sqrt(h*delta T). The amount of heat that moves through the dampers in Btu/hour is approximately U = Q delta t.) An example: 10 'ball park solar closet house design 20 TA=32'average December ambient temp 30 TCOLD=-10'coldest December ambient temp 40 SUN=1000'average amount of sun falling on sunspace glazing (Btu/ft^2/day) 50 DL=6'average number of hours of sun per day 60 TR=68'room temp 70 L=12'house length 80 W=8'house width 90 H=8'house height 100 AW=2*(L*W+L*H+W*H)'outside surface area 110 RW=23'R-value of outside surface of house 120 DHL=24*(TR-TA)*AW/RW'daily heat loss 130 DHLC=24*(TR-TCOLD)*AW/RW'heat loss on coldest day 140 AV=8*8/144'damper area (ft^2) 150 DF=AV*161.6*SQR(H)'damper factor 160 TSS=TR+(DHL/6/DF)^(2/3)'minimum ss temp to supply average daily heat 170 PRINT TSS;"F, minimum sunspace temp to supply average daily house heat 180 C=4000'pounds of water in solar closet 190 ATM=200'thermal mass surface area 200 RM=2/3'thermal mass surface R-value 210 LC=4'closet length 220 WC=4'closet width 230 HC=8'closet height 240 RC=20'R-value of solar closet surface 250 'find min solar closet temp ness to heat house on an average day w/o sun 260 TCM=TR+(DHL/24/DF)^(2/3) 270 PRINT TCM;"F, closet temp ness to heat house on an average day w/o sun" 280 'find min ss solar closet temp to provide heat for 5 days w/o sun 290 TCS=TCM+5*DHL/C 300 PRINT TCS;"F, min steady state solar closet temp for 5 day heat storage 310 'find avg closet cfm to keep house warm on coldest day w/o sun" 320 CFM=DHLC/24/(TCS-TR) 330 PRINT CFM;"cfm, avg closet airflow to heat house on coldest day w/o sun 340 'find average daily solar closet loss at that steady state temp 350 DCL=24*((TCS-TR)*(HC*WC+HC*LC)/RC+(TCS-TA)*(HC*WC+HC*LC)/RW) 360 AC=2*2'solar closet damper area 370 DFC=16.6*AC*SQR(H)'solar closet damper factor 380 TCP=TCS+(DCL/6/DFC)^(2/3) 390 PRINT TCP;"F, sunspace temp ness to make 5 day closet air temp" 400 'find min glazed area to make tcp, while providing heat and closet heat 410 AG=(DHL+DCL)/(SUN-DL*(TCP-TA)) 420 PRINT AG;"ft^2, min glazed area to make 5 day closet air temp" RUN 74.29121 F, minimum sunspace temp to supply average daily house heat 70.49667 F, closet temp ness to heat house on an average day w/o sun 94.53841 F, min steady state solar closet temp for 5 day heat storage 65.42774 cfm, avg closet airflow to heat house on coldest day w/o sun 97.65994 F, sunspace temp ness to make 5 day closet air temp 41.99063 ft^2, min glazed area to make 5 day closet air temp Article 44000 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy Subject: Re: Select a power source for my home state Date: 26 Dec 1995 18:28:58 -0500 Organization: Villanova University Lines: 19 Message-ID: <4bq0fq$7c4@vu-vlsi.ee.vill.edu> References: <4bktd1$2te@earth.laitram.com> <4bolme$6o8@newsbf02.news.aol.com> <4bot6j$43m@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu John McCarthy wrote: >Nick Pine includes: > > Does this include the cost of fuel disposal, > decommissioning, entombment, or Pinkerton guards to watch > over the site for 50,000 years? > >Why would you want Pinkerton guards? What precisely do you have in mind? Nuclear waste has a very long dangerous lifetime, no? And we don't really know how to keep it from running amok in the environment for even a hundred years yet... The oldest manmade structures on earth are what, 5000 years old? And they have had their problems, not all anticipated. Meanwhile, many of our governments and corporations seem to feel that 3 months is a very long time. It may be arrogant to presume that we know anything about how to contain nuclear waste on that time scale, no matter how good our designs. Nick, repeating an obvious truth, to people will not listen. Article 4247 of bit.listserv.geodesic: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.geodesic Subject: Re: Planck and christmas Date: 28 Dec 1995 09:18:10 -0500 Organization: Villanova University Lines: 242 Message-ID: <4bu8v2$em6@vu-vlsi.ee.vill.edu> References: <63225.tagdi@ruulch.let.ruu.nl> NNTP-Posting-Host: vu-vlsi.ee.vill.edu wrote: >>...not too many people, eg on Interstate 50 through southern Nevada and Utah. > just for remembrce sake, since i suffer amnisia sort of, if you go from >Chicago to San F i think you take 30 highway no, and if you go south > direction l.a you take ....?, 5 runs north to south.southward for spherical > perspective. >totally forgot, those are the days. OK, I'll go look at the road atlas in my car, out on the street on this cold sunny day in Brooklyn, with some leftover snow. Where are my shoes...? Looks like route 80 will get you from SF thru Reno, Salt Lake City, Cheyenne, Omaha, Chicago, Toledo, Cleveland, and all the way to New York City... Route 35 seems to be a large E-W bisector of our contintent, running from Thunder Bay, Ontario (where it calls itself route 81), down the northwestern edge of Lake Superior to Duluth, Minnesota, thence through Minnehopeless, Des Moines, Kansas City and Wichita (after a westwards arabesque), and on to Oklahoma City, Dallas, Waco, San Antonino, then (alias route 85) further on to Monterrey in Mexico, then on down through Mexico City to Acapulco... Where it is probably warmer now. >>>>A lot of farmers around me (I have more sheep and goats than people >>>>for neighbors) are actually very good mechanics, rebuilding their >>>>tractor engines every year, welding, etc. They could probably make >>>>a lot more money fixing cars. >> >>>. . that is why they have subsides, few billions around the second war. >> >>I think these guys are mostly unsubsidized. They farm for a hobby, >>after their full time job is over. One I knew was a telephone lineman. > > oh, i got it, it is the agribusiness that got the subsides. Yes, I think so. Individuals don't get much. $50/year for 5 acres? Depending on what you choose to not grow. But you have to have a track record of growing things first, before you can make money not growing things. >>> by the way do you have basic understanding of geometry or do you need >>> basic help. >> >>I need help. > > then i can send you lesson one soon, though i am self know very little > really, you do know nothing at all. i will feel very stupid >sending you a staff you know already. are you making fun of me, little >me. do you have Admonson Amy book. No, I really am mostly ignorant, and often confused by geometry, as in school mechanics problems ("How much Coriolis force will the ant feel on his left leg, as he tries to crawl east on the ball that the child is spinning around his head on a string at the equator?") I think this task will be nearly impossible, with only email text communication. Good. I don't have that book. >>Happy happy Christmas. > > i was suspended and time escaped... Christmas was like that for me too, with a 1 day flu and a 102 fever. > do you know Nick Consellatey a funny guy i know who have mention you to > me. oh that Nick is in a big cave similar in proportion to my cave. No, I don't know him... You guys live in caves? I have a some friends who lives in a solar cave, with an annual electric resistance backup heating bill of $58. They get ready for winter in late November, by closing some windows to make the temperature rise in their slow house from 70 F to 72 F, over two weeks. Suppose cavepersons had had glass... . ^ . | up . R10 earth at . south ==> 55 degrees F . . / g If the enterprising caveperson had insulated Rc / g the inside of the cavern with leaves and ------------------g W g mud, until, say, Rc = 10, and the daytime | .----- . temp of the cavern had been 65 degrees F | 20 x 20' cavern | . and the nighttime temp had been 55, and | 10' tall | . he or she had desired to warm the cave | | . for, say, 5 days without sun, with an --------Rf-------- . average sunnytime steady-state floor |vaulted -- stone | . temp of, say 90 F, and mammoth skins | ----- ----- | T . piled on top of the floor to make |--- floor ---| . a sunny day R-value of Rf (which . . . skins could be moved aside to . Rc . . . decrease the R-value of the floor . g during sunless times), how much Note that since .Rc g glass area, Ag, would have been the upper edge of the . g Ag needed, and what would Rf and glass is lower than the . g the average floor thickness T bottom of the floor, the floor .Aa g have had to have been, stays warm during sunless times, . g ignoring the clerestory because of this igloo-like heat trap. . g cave window, W? (How did the caveperson insulate around . g the edge of the floor?) g south ==> . The daily heatloss of the cavern would have been . . Lday = (8 hours)(1200 ft^2/R20)(65-55) ~ 5K Btu. 32 F outside temp . During sunny times, the sun would shine onto the . absorbing surface Aa, assumed equal to Ag, and some . heat would be lost thru Rc to the earth underneath... . . The daily net heat resulting from each square foot of . glass might have been on the order of . . Eg = 1000 - 8(90-32)/R1 - 8(90-55)/R20 . sun glass loss absorber back loss . = 500 Btu/ft^2/day . . So keeping the cavern warm might have required only about . 10 ft^2 of glass... A 3.16 x 3.16' single-glazed window, or . an early sliding-glass door... . . The mammoth-skin floor resistance would want to have been about . . Rf = (90-65)(400 ft^2)/(5000/8) = R-16. . . During sunless days, the skins would be moved around or a trapdoor . in the floor would have been opened to reduce this, to get more heat . out of the floor... . . Assuming the floor would have had a minimum R-value of 1, per square foot . (both sides), the required heat transfer rate would have been about 5000/8 . Btu/hour, from 800 ft^2 of floor, which leads to a minimum temperature . differential, after 5 days, of about 1 degree F. So if the masonry had held about 22 Btu/ft^3/degree F, the floor thickness might have wanted to be about T = (5 days)(5000 Btu/day)/((90-66)(22)(400 ft^2)) = .12' Hmmm. Ferro-cement... Other modern improvements might include making the whole thing above ground, including some bottles filled with water in the floor, making the absorbing surface a parabolic reflector, and making the floor a wall. >i try to read the rest. I have a solar calculator which i use very rarly >but it gives me the feeling i own free machine, if only we > can get a house like that we will be in our way to send politican > home to learn how to cook French food. When houses and fuel are free, the politicians will need retraining, eh? OK. Here's more... #include #include main() { /*ball park solar closet house design*/ double TA,TCOLD,SUN,DL,TR,L,W,H,AW,RW,DHL,DHLC,AV,DF,TSS,C,ATM,RTM,LC,WC,HC; double RC,TCM,TCS,CFM,DCL,AC,DFC,TCP,AG,UC,QC,EFF,DT,TBOT,TTOP,NTUF,CH,CC; double CFMSHM,CFMSHA,CFMCHA,CFMCHM,CFMSCA; TA=32; /*average December ambient temp (F)*/ TCOLD=-10; /*coldest December ambient temp (F)*/ SUN=1000; /*average amount of sun falling on sunspace glazing (Btu/ft^2/day)*/ DL=6; /* average number of hours of sun per day*/ TR=68; /*room temp (F)*/ L=12; /*house length (ft)*/ W=8; /*house width (ft)*/ H=8; /*house height (ft)*/ CH=2000; /*thermal mass of house (lb H2O)*/ AW=2*(L*W+L*H+W*H); /*outside surface area (ft^2)*/ RW=23; /*R-value of outside surface of house (ft^2-deg F-hr/Btu)*/ DHL=24*(TR-TA)*AW/RW; /*daily house heat loss (Btu)*/ DHLC=24*(TR-TCOLD)*AW/RW; /*heat loss on coldest day (Btu)*/ AV=1*2.; /*damper area (ft^2)*/ DF=AV*16.6*sqrt(H); /*damper factor*/ TSS=TR+pow(DHL/6./DF,2./3.); printf("%.1f%s\n",TSS," F, min sunspace temp to supply average daily heat"); CFMSHM=DHL/6./(TSS-TR); printf("%.1f%s\n",CFMSHM, " CFM, avg ss-house airflow on a day with min sun"); CC=4000; /*pounds of water in solar closet*/ ATM=200; /*thermal mass surface area (ft^2)*/ RTM=2./3.; /*thermal mass surface R-value (ft^2-deg F-hr/Btu)*/ NTUF=ATM/RTM; /*see 1993 ASHRAE HOF, p 3-4*/ LC=4; /*closet length (ft)*/ WC=4; /*closet width (ft)*/ HC=8; /*closet height (ft)*/ RC=20; /*R-value of solar closet surface (ft^2-deg F-hr/Btu)*/ TCM=TR+pow(DHL/24./DF,2./3.); printf("%.1f%s\n",TCM," F, min closet temp to heat house on avg day w/o sun"); TCS=TCM+5*DHL/CC; CFMCHM=DHL/24./(TCS-TR); printf("%.1f%s\n",CFMCHM," CFM, avg closet-house airflow after 5 day w/o sun"); printf("%.1f%s\n",TR-DHL/CH," F, min house temp at night, w/o closet heat"); printf("%.1f%s\n",TCS," F, min water temp to heat house 5 Days w/o sun"); /*find avg closet cfm to keep house warm on coldest day w/o sun*/ CFM=DHLC/24./(TCS-TR); printf("%.1f%s\n",CFM," CFM, avg c-h airflow on coldest day, at 5D clo temp"); /*find average daily solar closet loss (Btu) at that steady-state temp*/ DCL=24.*((TCS-TR)*(HC*WC+HC*LC)/RC+(TCS-TA)*(HC*WC+HC*LC)/RW); AC=1.*2.; /*solar closet damper area (ft^2)*/ DFC=16.6*AC*sqrt(H); /*solar closet damper factor*/ UC=DCL/DL; /*min clo gain/hour (Btu) on an average day, to maintain 5D temp*/ QC=pow(DFC*DFC*UC,1./3.); /*min clo airflow (CFM) to maintain 5D temp*/ EFF=exp(-NTUF/QC); /*heat exchanger efficacy for solar closet*/ DT=UC/QC; /*temp difference from top to bottom of closet (F)*/ TBOT=TCS+DT*EFF/(1-EFF); /*temp at bottom of closet (F)*/ TTOP=TBOT+DT; /*temp at top of closet (F)*/ printf("%.1f%s\n",TBOT," F, avg daytime steady-state temp at bottom of closet"); printf("%.1f%s\n",TTOP," F, avg daytime steady-state temp at top of closet"); CFMSHA=DHL/6./(TTOP-TR); printf("%.1f%s\n",CFMSHA," CFM, avg ss-house airflow on an average day"); CFMSCA=DCL/6./DT; printf("%.1f%s\n",CFMSCA," CFM, avg ss-closet airflow on an average day"); /*find min glazed area for min ss temp, while providing house and closet heat*/ AG=(DHL+DCL)/(SUN-DL*(TTOP-TA)); printf("%.1f%s\n",AG," ft^2, min glazed sunspace area for 5D storage"); } 78.5 F, min sunspace temp to supply average daily heat 304.6 CFM, avg ss-house airflow on a day with min sun 72.2 F, min closet temp to heat house on avg day w/o sun 28.4 CFM, avg closet-house airflow after 5 days w/o sun 58.4 F, min house temp at night, w/o closet heat 96.2 F, min water temp to heat house 5 Days w/o sun 61.5 CFM, avg c-h airflow on coldest day, at 5D clo temp 97.8 F, avg daytime steady-state temp at bottom of closet 102.9 F, avg daytime steady-state temp at top of closet 91.8 CFM, avg ss-house airflow on an average day 211.7 CFM, avg ss-closet airflow on an average day 44.7 ft^2, min glazed sunspace area for 5D storage Nick Article 3690 of sci.engr.lighting: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.engr.lighting Subject: Re: sulfur lighting Date: 30 Dec 1995 08:50:51 -0500 Organization: Villanova University Lines: 39 Message-ID: <4c3g3r$p2v@vu-vlsi.ee.vill.edu> References: <4btjn3$6lg@barad-dur.nas.com> <4bu3b0$pa8@news.infi.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Charles Troxell wrote: >Uh Oh, another indoor plant grower? They are everywhere :-) Ex-aerospace engineer Rudy Behrens of Aurora Farms at (610) 489-6256, 1547 N. Trooper Road/Norristown, PA 19403, has set up a 36' diameter galvanized steel building, painted white on the inside, with no windows, just 12 kW of overhead HPS and metal halide gro-lights, running 16-18 hours per day, to grow organic hydroponic bok choy, lettuce, herbs and tomatoes for local restaurants. (With all that electrical power, his well- sealed metal building only needs an R-value of about 4 to keep the plants warm in the winter.) He says it takes about 900 w-h to grow a head of lettuce from seed to maturity in 26 days, IF you fool the lettuce early on with appropriate light angles and intensities and day lengths to believe that it's June 30 on the Arctic circle. (How could we do this with natural sun?) He says this early plant training, just as the first two leaves appear from seed, programs the whole growth cycle, and he can produce 1200 heads a day, selling for $1 each. Sales may be the weak link here, but Rudy's launching an ad campaign. He doesn't grow low-light plants like those sold by de Reuters, et al, but traditional garden varieties, like Big Boy tomatoes. Rudy says low-light plants look good, but to make plants taste good you have to spend energy to make the higher complex tasty molecules. All of his electricity comes from a propane generator. He sells a smaller $5K system for use in cities and suburbs, with a 1 kW lamp, ideally set up in a garage with, say, a 5 kW Intelligen oil-fired cogenerator to run the lamp and provide heat and electricity for the attached house, while selling the excess electricity back to the power company and producing 100 heads of lettuce per day on a continuous basis, with no seasons. Rudy says the city dweller can pay off the system in 9 months, laboring one hour a day. He has 4 other working small vegetable factories now, in Lansdale, Trooper and Philadelphia, PA. He calls the group a co-op, and he finds the food customers. Nick Article 44849 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,alt.solar.thermal,alt.architecture.alternative,bit.listserv.geodesic,bit.listserv.Alternative.Energy,alt.home.repair,sci.engr.heat-vent-ac Subject: Solar closet questions and answers Date: 4 Jan 1996 08:47:27 -0500 Organization: Villanova University >1/ If you have the thermal mass under a house isn't it going to be bloody >hot in summer? Perhaps, but a) why put the thermal mass under a house? and b) ve haf ways to keep the sunspace from overheating in summer. Why not put the thermal mass, eg a solar closet, inside the house, sitting on the ground, behind the sunspace... Of course the house would have some thermal mass of its own too. In the summer the sunspace and solar closet might be quite cool, if they were aired out in the evenings, or shielded from the sun by some greenhouse shadecloth hanging outside of the glazing, etc. Or we might want to keep the solar closet hot to make hot water for the house or to let it serve as a thermal chimney at night, in order to ventilate the house when the outside air is cooler, and store "coolth" in the thermal mass of the house itself at night, then button up the house during the day, with no daytime ventilation to the outside. Keeping the sunspace hot in the summer might mean tilted vs vertical glazing, or a horizontal shiny reflector in front of it. >With any reasonable level of insulation it is still going to leak heat a bit. Sure, but the point is to design an overall system that will maintain a comfortable temperature. Vents, grapes, runner beans, clematis, and overhangs can all help keep the sunspace cool in the summer too. The heat that leaks into the house during the day can usually be vented out of the house at night. For example, suppose the house is 2,000 ft^2, two stories, ie about 30' x 30' x 16' tall, with average R30 walls and ceiling, and suppose it has gypsum drywalls, 1/2" thick, as the main thermal mass of the house, which have a thermal mass equivalent to about a half pound of water per square foot of wall, and suppose it is 90 F outside during the day and 70 F at night. If the house has the same sort of ventilation night and day, and no internal heat gain, it will average out the outdoor temperature swings, to have an average internal temperature of 80 F. What can we do to keep the house at 80 F max, 24 hours a day? This house has an exterior surface area of about 1,000 ft^2 for the ceiling and 500 ft^2 for each wall, a total of 3,000 ft^2, so A/R is 3,000/30 = 100, ie if the outside temp is 1 degree F warmer than the inside temp for an hour, the house will gain 100 Btu of heat. In this example, the heat that leaks into the house during the day through the walls and ceiling will be about 12(90-80)100 = 12,000 Btu, which could be removed with 2 hours of air conditioning with a 6,000 Btu/hour 1 kW window air conditioner, or removed by night ventilation... How much, using seat of the pants calculations? 1 Btu will heat 55 ft^3 of air 1 degree F, which means that 1 cfm of airflow with an air temp difference of 1 degree F will remove about 1 Btu/hour. We need to remove about 12,000 Btu in 12 hours, or 1,000 Btu/hour with a 10 F air temp difference, which means the fan (or solar closet induced ventilation) has to move an average of 100 cfm at night. A very small fan. Here's another rule of thumb for convection airflow induced by heat: if you have a space that is H feet tall, and the air at the bottom is Tb degrees F and the air at the top is Tt degrees F, and there are vent holes for airflow at the top and bottom of the space that have an area of Av ft^2 each, the amount of air that will flow through those holes in cfm will be approximately Q (cfm) = 16.6 Av sqrt(H(Tu-Tt)). So how big do the holes have to be to make 100 cfm of air flow at night, if the house is 80 F and the outdoor air is 70 F and the distance from the top to the bottom vent hole is 8'? Let's turn this equation around: Av = Q/(16.6 sqrt(H(Tu-Tt))) = 100/(16.6 sqrt(8'(80-70))) = 0.67 ft^2. About 100 in^2, not very big, 10" x 10"... Of course we want these holes to open up automatically at night and close during the day, eg with motorized dampers with thermostats or passive plastic film backdraft dampers that only allow air to flow into the house through the bottom hole and out of the house through the top hole. Suppose we used the solar closet as a "fan" to move this air. Suppose it were 120 F instead of 80 F? Then we have Av = 100/(16.6 sqrt(8(120-70))) = .3 ft^2, ie 43 in^2 or say, 10" x 4". The vents could be still smaller, or there would be more airflow for the same size vents. What does the thermal mass of the house have to do with this? The house has a thermal mass of about 1/2 pound of water per square foot of wall and ceiling, or 1/2 x 3,000 = 1,500 lb of water, ie 1,500 Btu/degree F of thermal mass, total. If we want the maximum temperature inside the house to be 80 F, with the conditions above, how cool do we have to get the walls of the house at night? We cool them off at night, and they heat up when the heat leaks into the house during the day... As the house heats up 1 degree F, the walls will absorb 1,500 Btu of heat. We decided that during the day, the house will absorb about 12,000 Btu of heat, which will raise its thermal mass temperature, ie its temperature, by 12,000/1,500 = 8 F, so to keep the house temp below 80 F at all times during the day, it has to have a maximum temperature of 72 F at dawn. If we added more thermal mass to the house, it could be warmer at dawn and still stay below 80 F during the whole day. Let's try that, say an extra layer of drywall, poof. Now we have 3,000 Btu/degree F, so the house only needs to be 76 F at dawn... In one solar closet house example, we suggested 20 55 gallon drums full of water for thermal mass. If this were used for house cooling, with the closet vented at night and completely shaded and insulated during the day, the thermal mass available for cooling would be about 10,000 pounds of water, so the closet could keep the house below 80 F during the day if its temp at dawn were roughly 80 F - 12,000/10,000 = 80 - 1.2 = 78.8 F. We would want to look at the heat transfer rate here too. >2/ Is there any way you could have the sunspace physically separated from >the thermal mass? You mean more separated? Sure. The easiest way is to put the thermal mass above the sunspace, as in the attic warmstores of Norman Saunders, PE, so hot air from the sunspace naturally flows up to the thermal mass and heats it during the day, and the heat stays trapped up there in the thermal mass like an igloo, with the entrance below the heated space, since warm air rises. But then you have to have a stronger attic or second floor to hold up the thermal mass, which tends to be heavy, and that can be a more dangerous situation in earthquake-prone parts of the world (altho it might make the house more fireproof, with some sort of sprinkler system, and provide a more natural water and hot water supply, starting with rainwater), and you have to somehow bring some warm air back down to the house to provide heat for the house when the house needs heat, which probably means using a fan, rather than natural convection, even tho natural convection can make this whole system work if it is on the ground floor, in principle. A vaulted stone ceiling with foam on the outside of the stone would be nice, with a ceiling fan to bring the heat down to the living space... A cathedral or Monolithic Dome... We could modify Notre dame. Foam the roof, add some ceiling fans, fill in the south buttresses with polycarbonate or polyethylene film glazing to make an inexpensive sunspace... We can also put the thermal mass on the same level as the sunspace, or underneath it, as in a low-thermal-mass solar attic, with the thermal mass in the basement. This usually requires a fan or a blower to make it work, but if the ducts that connect the low-thermal-mass sunspace and the high- thermal-mass heat battery are large enough in cross section, eg 2'x 2' across, large fans can be used instead of more power-hungry blowers, and the electrical fan power used can be reasonably small. >3/ Is there any way you could have the sunspace/thermal mass separated from >the house? Sure. But it is not easy to move heat over large distances. In the case of hot air, if the ducts are small in cross section, the air velocity and fan power need to be higher, and if the ducts are larger, they cost more and take up more space and leak more heat through their walls, even if those duct walls are insulated. It's easier to move hot water than hot air over a distance, but then you have energy efficiency and economic and complexity penalties in converting the hot air to and from hot water at each end. I suspect that putting a solar furnace out in the yard may not make much sense in todays's economics, if that's all the structure does, since oil is so cheap. But then, putting solar water heating panels or PV panels on the roof may not make much economic sense either... Chacun a son gout special. >4/ Would the air passing over the thermal mass and then into the house pick >up the smell of hot plastic? (Assuming water is being used for thermal mass >and said mass is stored in plastic containers.) I don't know. I doubt it, at these temperatures. >Could you use a heat exchanger to avoid this problem? I suppose so, but that sounds like a complication to be avoided. >5/ What about using phase change materials in the heat store? (Admittedly >more complex.) Last time I looked, they seemed to be expensive, vs water, and Glauber's salts need to be stirred up mechanically once in a while to keep working. They also had a limited temperature range over which they act, vs water. Suppose you did have some super material with a very high thermal mass per unit volume--how would you get solar heat into and out of it? You need surface area for that, eg thin layers of material eg wallboard or ceiling tiles, but then the heat battery is not compact, and it has little insulation, and you have to live inside the heat battery, so you can't charge it up to a high temp on a sunny day... I haven't looked at this lately. I like water for thermal mass, in sealed containers in one compact, well- insulated high-temperature space, with lots of insulation in the house, so the heat battery does not have to contain too much water. I also like the idea of combining a solar thermal store and a warm wastewater treatment system, eg in a few septic tanks. Septic tanks are very cheap where I live, about $600 for a 5' deep x 6' wide x 12' long, 1500 gallon septic tank with a sealed lid. It might make sense to stack a few of those up out in the yard, say a structure 12' high and 8' wide and 12' long, surrounded by 6" of fiberglass insulation on all 5 sides, all round, with glazing on the sun- facing side. This would do a dandy job of sewage treatment, since biological reaction rates double every time we raise the temperature of the system 10 degrees C, up to about 55 C. But how would you get the solar heat out of that structure into the house? Cover the underside of the ceiling with fin tube pipes? Bury some copper pipes in sand or cement between the two tanks stacked on top of each other? >6/ If you put the thermal mass in the attic, what sort of extra building >requirements to deal with added weight? Again, this isn't the way I'd build a house. I'd put the thermal mass on the ground, but... We would need stronger than normal ceiling joists to put it in the attic, eg prefabricated plywood or 2 x 4 trusses... Not too expensive, but different from the usual way of building houses. Stacking up 55 gallon drums full of water 2-high all over the attic floor makes for an attic floor loading of about 275 lbs/ft^2 vs a more normal, say, 50 lb/ft^2. If the attic floor joists were on 16" centers, supported every 12', we might have something like this, following Charlie Wing's book, _From the Walls In_ (p. 39, Little Brown, 1979): 1. f = 1,200 psi fiber stress in bending, for the wood (Eastern Hemlock) 2. w = 275 psf uniformly distributed load o.c. = 4/3 ft on-center spacing L = 12' clearspan 3. W = w x o.c. x L = 275 psf x 4/3 ft x 12 ft = 4400 pounds total uniformly distributed load 4. M = W x L/8 = 4400 x 12 ft x 12"/ft/8 = 79,200 in-lb bending moment 5. S = M/f = 79,200/1,200 = 66 in^3 minimum beam section modulus 6. Pick a joist thickness or breadth, say b = 1.5". Then the depth d needs to be at least d = sqrt(6S/b) = sqrt(66/1.5) = 16.2" I suppose that some sort of 16" deep trusses might work here, or we might hang the attic floor from the roof rafters with wood members or cables. I'm not a structural engineer, and I'd put all this weight on the ground, if for no other reason than that it would be easier to get the hot air out of the thermal mass into the house without using a fan... >7/ What about passing hot air from the house across pipes containing cold >water as a cooling mechanism? (Not quite on the topic but I thought I'd >throw it in.) Seems like that would work, with say, a fan coil unit and some 55 F well and 80 F air. For that matter, why not use a basement or crawl space floor? Blow up some cool air into the upper part of the house from near a basement floor, with a vapor barrier under the floor. How much basement floor area A do we need, in the above example? Roughly speaking, 1000 Btu/hr = A (80-55)/R1, if the basement floor is 55 F. A = 40 ft^2, 5'x 8', not much. >8/ Any idea how long a plastic container heated to 170F will last? No, perhaps a long time if the drum is not pressurised, but 170 F seems quite warm for a system like this. Radiation losses would limit the drum water temp to about 130 F at most I'd think, if the collector has no $elective $urface. >9/ Say you put the sunspace under a (north facing for SH) verandah. Does >this affect energy collection? (I'm thinking of incident sun angles and >whether or not we need an exposed upper face.) That should work fine. What matters in wintertime is mainly how much vertical glazing there is, since the sun is close to horizontal in the middle of the winter. Snow or a white surface in front can significantly increase the solar input of vertical glazing by reflecting more sun onto the glazing. This doesn't work so well with tilted glazing. >10/ What's the biggest space currently being heated by a sunspace/thermal >mass combination? I don't know... Do we count the new NREL visitor's center with its trombe wall? :-( >11/ Is anyone making them commercially? "Them," as in solar closet and sunspace kits? Not that I know of, but it sounds like a very good idea, especially if the whole shebang can go together like an erector set, and be shipped UPS (rolls of thin polycarbonate glazing come to mind), except for a few common materials that could be obtained locally. >12/ How to make the outside of the sunspace/thermal mass aesthetically >pleasing? Hire an architect, and watch him or her carefully, so that he doesn't make the aesthetics the end-all and be-all of this :-) A LOT of people are very good at making things aesthetically pleasing... >13/ Say you had one of those dinky little Air-303 wind-turbines. I guess you >could hook this up to a resistive element in the thermal mass area and shove >in some heat this way? Sure. But it wouldn't contribute that much heat compared to the solar heat from a small amount of glazing: if the Air-303 were putting out 375 watts, 24 hours a day (which would take a continuous 30 mph wind, vs about 150 watts at 20 mph or 30 watts at 10 mph), it would contribute 375 x 3.41 x 24 = 30,690 Btu/day of heat to the sunspace, about the same amount of net heat as 40 ft^2 of glazing, ie 5'x 8' of glazing, at a higher price and complexity. I'd rather use this electricity to make my meter run backwards, or charge some batteries if I lived out in the boonies. On the other hand, putting a small woodstove or paper trash-burning stove in the solar closet might make a lot of sense. >Now, as I understand it, essentially we are trapping heat by warming air in >a sunspace. Sort of. Not trapping heat, exactly, just warming some air with it. Then the warm air flows into the house to heat it, and the sunspace warm air keeps the glazing of the solar closet warm. The glazing of the solar closet is in the back wall of the sunspace, so that inner glazing is exposed to that sunspace warm air, and it loses less heat than if it were outdoors. The sun shines through the sunspace glazing, then through the solar closet glazing, to heat the air in the solar closet air heater, which air recirculates through the solar closet, heating the sealed containers of water inside the closet. Meanwhile, the sun has heated the sunspace air to a lower temp, and some of that air flows through the house to heat the house. There are 3 air loops 1) sunspace air flows through the house to heat the house on a sunny day, 2) the hotter solar closet air heater air flows behind its separate smaller glazing inside the warm sunspace through the solar closet to heat sealed containers of water on a sunny day, and 3) on a cloudy day, house air flows through the solar closet, where it is warmed by the containers of water and flows back out to keep the house warm. There is a 4th loop in a water heating system: warm water from an air-heated fin-tube pipe just under the ceiling of the solar closet (such as the pipe used in baseboard radiators in houses and offices) rises up to move through a conventional water heater ("geyser") on the floor above and then back down to be warmed up by the fin tube pipe again, in a closed loop of pipe. All of these loops can be driven by fans and pumps if desired, but in some ways it's more elegant (and expensive, initially) to design the system so that they don't need to use fans or pumps, just natural convection (warm water and warm air rise.) This is like sailing vs. powerboating, a matter of personal style or purity and perversity :-) It doesn't matter. Both should work fine... >This warmed air is then used to heat a thermal mass in an area >thermally decoupled from the sunspace other than by this warmed air transport. The sunspace air is used to heat the thermal mass of the house itself, when the sun is shining... Air to heat the solar closet comes out of the solar closet at the bottom, into the air heater cavity behind the solar closet glazing, then rises up and is heated by the sun, then goes back into the solar closet at the top of the solar closet glazing. >(By thermally decoupled I mean that the only way energy gets from >the sunspace to the thermal mass is by mass transport of warmed air. True. But the warm air in the sunspace is not the same as the warm air in the solar closet. Solar closet air moves behind the inner solar closet glazing. (We could build a system with only one glazing, but I think it would be more expensive in cloudy climates, and it would be less efficient, I think, and the total amount of glazing would have to be larger.) >This means we don't give a shit about what temp. our sunspace gets to at night >because we are not relying on it for energy storage Pretty much true. Unless there are plants therein, in which case we might want to controllably let some warm air leak back out of the house into the sunspace at night to keep the plants from freezing. But you are on the right track here. >and there is no means for energy to leak from the closet back into the >sunspace.) True. Except through the good insulation. >The thermal mass area - or closet - is well insulated. The solar closet has >connections to a house such that it can exchange energy into the house. True. Two openings, one at the top and one at the bottom, to allow warm air to flow out from the closet to the house at the top, and allow cooler house air to flow into the closet to replace it and be warmed by the sealed containers of water and flow out the top, back into the house. >14/ Where does the air entering the sunspace come from? From the house, eg from a return air register near the floor of the house that opens into the sunspace. Or from a basement window or the lower part of a partly open first floor window of the house, with a passive film backdraft damper that only lets air flow from the house to the sunspace. Warm air from the sunspace would flow back into the house through an upstairs opening or window fitted with a motorized damper or fan controlled by a two thermostats-- one to enable the fan to turn on when the sunspace is warm, and one to enable the fan to turn on when the house is cool. Both would have to be "on" to enable the fan to turn on, ie the fan would be in series with both thermostats, electrically. Controlling a motorized damper is only slightly more complicated. The kind that uses no power when it is in a fixed position has one set of wires to make it open more and another set of wires to make it close more. It might be controlled with three thermostats, or two thermostats and a relay. Two passive thermostatic dampers with bimetallic springs, in series, could also do this job, less accurately, but less expensively ($20) and more naturally, with no electricity needed for controlling the house temp. >15/ The physical barriers between the sunspace and closet only open when the >sunspace temperature is equal or higher than the temp. in the closet? The barriers from the house to the sunspace open when the house is too cool and the sunspace is warm enough. Once the house warms up or the sunspace cools, they close. The barriers between the solar closet and its air heater open whenever the temp in the air heater is warmer than the temp in the closet. This temp control is actually simpler--the "greedy algorithm"-- "make the solar closet as warm as possible--with no limit." Vs. only heating the house up to 68 F or 20 C. >16/ How reliable are the simple dampers you mention in several of the posts? The bimetallic spring thermostatic dampers (aka automatic foundation vents) are very reliable, but they begin to close at say, 60 F and they are not fully closed until say, 80 F, so they would make for fairly soft temperature control in a house. If you turn the springs over these dampers work in the more usual (opposite) sense, opening more as the air gets warmer, which would be useful in the sunspace, in series with the sunspace to house damper, working in the opposite sense, exposed to house air. Some motorized dampers are very reliable, with tiny 2 watt motors and expected lifetimes of 100,000 cycles, 300 years if they open and close once a day... Backdraft plastic film dampers are fairly reliable, but somewhat delicate. They should be inspected once every two or three months, it seems to me, to check to see that the plastic film is not ripped or folded and stuck to itself, stuck open, etc. The low temp plastic film dampers can be made from dry cleaner bags and metal screenwire. >17/ What constraints does relying on convection introduce? Warm air rises. So convection powered systems have to have everything more or less on the same level, eg ground level, or even better, the "heaters" should be below the things that are heated. An ideal solar house might have the house at the top, the thermal mass below that, and the sunspace glazing below that. The house should also have a cooling damper that automatically opens to the outside if the house begins to get too warm. This would waste some solar heat, and allow some ventilation, and allow using less insulation between the thermal mass and the house. >18/ Can these be got around with fans? Of course. It's not too hard to calculate what the fan characteristics have to be, in CFM and static pressure, and a fan-driven system will probably be more economical... One of my favorite fans is the Grainger 4C688 $60, 36 watt 10" 560 CFM fan with a stalled static pressure of 0.4" H20 and a max temp rating of 149 F. >19/ At what sunspace temp. will you be losing energy through the heat capture >section of the sunspace at the same rate that energy is entering. (Obviously >this depends on incident radiation.) Well, suppose you have say, 300 Btu/ft^2/hour of sun coming into the glazing, (a direct beam of full sun) and the outdoor temp is say, 32 F. Then if you are not taking out any energy from the sunspace to heat the solar closet or the house, Energy in = Energy out for the sunspace, and all of the sun that comes into the sunspace heats up the sunspace, which heats up the glazing, which heats up the outdoors again, so roughly speaking, ignoring radiation heat transfer, for 1 ft^2 of glazing with an R-value of 1 that transmits 100% of the sun that falls on it and blocks 100% of the longwave IR that tries to exit through the glass by radiation ("the greenhouse effect") 300 = (T-32)/R1, so T = 32 + 300/1 = 332. Pretty simple, huh? :-) Radiation losses will probably limit sunspace temps to less than 150 F, if no selective surface is used, since a 1 ft^2 black body at a temperature T (F) emits 0.174 x 10^-8 x (T+460)^4 Btu/hour by radiation. The outside world also radiates a little energy back at the sunspace. A 32 F outside world would radiate 0.174 x 10^-8 x (32+460)^4 = 102 Btu/hour towards the sunspace, so we have (counting only radiation heat transfer) 300 + 102 = 0.174 x 10^-8 x (T+460)^4 ==> T = 233 F. But I think the real world temperature will be lower. Altho we HAVE seen sunspace temps of 154 F in our test house, when we were actually using the sunspace to heat the house and solar closet... This is oversimplified. The glazing might pass 90% of the sun, with an R-value of 2/3, not 1, which depends on the temp itself, and there's another factor of 0.88 in the radiation formula above, for the emissivity of the glazing, and there is more solar energy coming in if there is snow on the ground, etc... But you get the idea. Hot :-) Nick Article 45064 of sci.energy: From: nick@bart.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,alt.solar.thermal,sci.engr.heat-vent-ac,alt.home.repair,alt.archicecture.alternative,bit.listserv.Alternative.Energy,bit.listserv.geodesic Subject: Re: Recovery of Solar Heat from Attic Date: 5 Jan 1996 18:07:58 -0500 Organization: Villanova University Lines: 67 Message-ID: <4ckb0e$gr@bart.ee.vill.edu> References: <4cjulr$200@lll-winken.llnl.gov> NNTP-Posting-Host: bart.ee.vill.edu Xref: news.ee.vill.edu sci.energy:45064 sci.engr.heat-vent-ac:4454 bit.listserv.Alternative.Energy:1056 bit.listserv.geodesic:4302 George Weinert wrote: >A few years ago, I read about a company that was going to build heat >exchangers to go into your attic space to recover heat during daylight >hours, and bring some portion of that heat into the living space of >your home... Perhaps this was Ed Palmer of Solar Attic, Inc. at 15548 95th Circle, Elk River, MN 55330-7728, (612) 441-3440/7174 fax/email SolarAttic@aol.com. Their system may be covered by US Patent No. 5,014,770, issued May 14, 1991, which may expire in 2008, or perhaps sooner. >I also seem to recall having read about a study done on a home in >Minnesota(?) which blew hot (warm?) attic air into the house any time >the attic rose above 68F(?). I seem to recall that the home had >significantly reduced utility bills, and that the payback time on the >equipment was rather short. I seem to recall a documented 25% savings, with a conventional roof. >I am interested in perhaps building and installing such a system in my home, >if it's actually cheap enough, reliable enough, and effective. It seems to me that a system like this can be cheap, reliable and effective, especially if your next steep-sloping south roof is made of clear thin single- layer Dynaglas or Replex corrugated polycarbonate plastic (not fiberglas), like mine. This material costs about $1/ft^2 and it is commonly used in commercial greenhouse roofs, and it has a 10 year guarantee against yellowing, and an expected mechanical lifetime of at least 25 years. Its lifetime can be extended and the attic made cooler in summer by covering it on the outside with a large sheet of 15 cent/ft^2, 80% greenhouse shadecloth. >Any construction details or pointers would also be greatly appreciated. Well, the plastic comes in standard lengths of 12' and a width slightly more than 4', so it can be overlapped 1 corrugation for support on 4' centers. And you want to keep warm house air out of the attic at night, to avoid heat loss and condensation. Which to me means a passive plastic film backdraft damper near the bottom of the supply duct, near the attic floor. The duct itself might be a polyethylene film tube, say 24" in diameter, bought from a commercial greenhouse supplier for about 30 cents per linear foot, with a large slow fan at the top pushing warm air down from near the roof peak into the house. The return duct might be a 2' x 2' piece of 1-2" foil-faced foam in the floor at the other end of the attic, with a hinge on one edge and a $50 Grainger 4Z451 reversible 115VAC gearmotor and some sort of spool attached to the shaft to wind up a 1/16" nylon string attached to a screw eye in a rafter, with a couple of limit switches. You might control this with one or two cooling thermostats in the attic and a heating thermostat in the house, in series with the fan, eg 2 or 3 Grainger 2E158 thermostats ($14.05 each.) >BTW, I live in the mild climate of the SF Bay Area, so I beleive my attic >actually does warm up significantly even on 'cold' days (mid 40's, brrr ;-) Seems like this should work pretty well there, especially in the spring and fall, even with a conventional roof. Some of my Phila area neighbors tell me their attic fans with thermostats turn on in the middle of the winter... A transparent roof should be able to collect at least the heat equivalent of about 1 gallon fo oil per year per square foot of vertical south-facing projection of the roof glazing. Or maybe you'd like a small nuclear engine in your attic :-) Good luck. Nick Article 4575 of sci.engr.heat-vent-ac: From: nick@old-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.engr.heat-vent-ac Subject: Re: Residential Heat Recovery Ventilator Date: 13 Jan 1996 07:36:57 -0500 Organization: Villanova University Still ruminating on the fact that air infiltration may make for half the heat loss in a superinsulated house, reducing heat storage time in the 10,000 lbs of hot water in a solar closet to 80 hours, if, say, the 2000 ft^2 house needs 200 Btu/hr-F in Phila... How does one accurately calculate the air infiltration loss of a house in the winter, vs just using the raw 50 Pascal blower door test data? 50 Pascals is 0.2" of water, corresponding to a 20 mph wind trying to blow cold air into every side of a house at the same time, or 20 times the stack effect pressure in a 2-story house with an indoor-outdoor temperature difference of 80 F. The NREL book says the average windspeed in Concord, NH, in December is 3.0 m/s <--> 6.3 mph <--> 0.02" H20. The average NREL windspeed in Phila is 4.2 m/s <--> 8.8 mph, but we have measured an average closer to 5 mph on the flat roof of our 4-story building, in between gusts that blow down trees :-) The very coldest times are often dead still, with no wind, at night. Part of the lesson here may be that superinsulated houses should have good trees for windbreaks, or be underground. I wrote of an Avis modular house: >The house has a remarkably low air infiltration rate of 0.0125 ACH, >based on a 50 Pascal air infiltration rate of 0.25 ACH. I divided the 50 Pascal spec by 20, following a rule of thumb in Nisson and Dutt's 1985 _Superinsulated Home_ book, which is the only place I've ever read about this. They were not very definite about this rule of thumb. Perhaps more is now known about this relationship? Page 43 of the book says: Note that the 50 Pascal leakage rate is obtained according to the _exaggerated interior-exterior pressure difference_ created by a blower door. By available methods of calculation, a 50 Pascal leakage rate of 3.0 acph translates into about 0.15 acph average leakage rate under _natural, everyday air pressure differences_. A leakage rate of 0.15 acph means that air leakage is very low. A 50 Pascal leakage rate of 1.0 acph translates into about 0.05 acph leakage rate under natural conditions. Page 221 says: Measuring the leakage at several pressure differences can be used to calculate another indicator of a house's leakage, it's equivalent leakage area (ELA)... An accurate prediction of the natural air infiltration equivalent to specific blower door measurements is far less useful for a superinsulated house than for a conventional house, because natural air infiltration in the former case is very small-- most of the air entering or leaving the envelope is accounted for in the controlled ventilating system. For this reason, even a crude formula relating pressurization leakage to natural air infiltration should suffice for a superinsulated house. Such a crude relationship is: typical winter natural average leakage at 50 Pascals (acph) air infiltration rate (acph) = ------------------------------------ 20 The natural air infiltration rate is roughly one twentieth of the leakage measured by the blower door at an inside-outside pressure difference of 50 Pascals. We call this the "divide by 20" formula. Artificial ventilation seems like less of a concern, because it can come from air-air heat exchangers or earth tubes. Jonathan Sawyer just posted some measured data from his earth tube + HRV system that indicates 95% efficiency in heating ventilation air... He used a 250' long x 1' diameter earth tube buried 6' in the ground, under a utility trench, with a measured airflow of 175 cfm at less than 0.1" H20 pressure drop. Perhaps this could have been done with a basement floor, and a downward duct from a basement window, and an upward duct from near the floor to the top of the house, with a fan, or two concentric tubes, as a counterflow air to air heat exchanger, which would also serve as AC in the summer, with airflow into the house in the outer tube only, powered by a sunspace or solar chimney. Nick Article 46567 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.architecture.alternative,alt.energy.renewable,sci.engr.heat-vent-ac,alt.home.repair,alt.solar.thermal,bit.listserv.geodesic Subject: Birdhouses and solar shelters Date: 23 Jan 1996 11:26:04 -0500 Organization: Villanova University Over the last couple of months, I've been watching a homeless person who has built himself a small homeless shelter under the 4' concrete overhang of a parking garage on Atlantic Avenue near Court Street in Brooklyn, next door to Saint Vincent's Family and Children's care center. A lot of homeless people in cities are mentally ill, and very suspicious, and not inclined to stay in city shelters, because city shelters are dangerous... Yesterday it was 32 F in Brooklyn and snowing. I wanted to take this man some hot food, but he didn't seem to be home when I stopped by. It's hard to tell when he's home... He lives in a sort of very small cave, like an animal. Will he get frostbite this week? Will he lose some fingers or toes? He and the center have something in common: they are both wasting solar energy. The center has a 60' tall x 40' wide south-facing plain brick wall, upon which the solar heat equivalent of approximately 24 gallons of oil fall every day in December. The south wall of this man's small shelter is a piece of plywood, 6' wide x 4' tall, with various blankets and quilts and sleeping bags stuffed around it to make a dark, concrete-walled cave under the parking garage. Now, there are lots of lean-to shelters on the Appalachian trail, some of them stocked with firewood, put there for the convenience of passing hikers, and we build birdhouses, don't we? Why not extend such charity to humans, and make some sort of urban shelters for people like this homeless man? Outdoor art, if you like, in urban parks... It seems to me that it wouldn't be difficult to put one $500 septic tank on top of another, with some foamboard on the outside, eg Dri-Vit, to make something like this human birdhouse: | 5' | | 12' | pffffffffff --- pppppppppppppppppppppppp p.........f p p p .f p p p .f 6' p p p .f p living space p p .f p p south p.........f --- p p p f.......f p..................... p p f. .f p . p p f. .f p rain . waste p p f.water.f 5' p water . water? p p f. .f p . p p f.......f p . p p fffffffff --- pppppppppppppppppppppppp Being in a city, this would have to be fairly bulletproof. Suppose p above is an 11' x 12' piece of easily-replaced polyethylene greenhouse film, with a few thin pieces of metal sewed into the edges to hold it tight against some magnets embedded in the south edges of the shelter. If the concrete tanks had walls that were 4" thick, the two tanks together would weigh about 4"/12" x (12'x16' + 5'x6'x2) x 150 lb/ft^3 x 2 = 25,200 pounds, with a thermal mass of approximately 0.16 x 25,200 = 4032 Btu/degree F. Filling the bottom tank with water would make the total thermal mass C = 4032 + 1500 gal x 8 lb/gal = 16,032 Btu/F. On an average December day where I live, about 1100 Btu/ft^2 falls on a south wall, so if the poly film has a solar transmission of 0.8, the amount of solar energy that gets into the structure would be about Ein = 11' x 12' x 0.8 = 116,000 Btu/day, And if the average outdoor temperature is 36 F and the average indoor temperature is T, and the poly film has an R-value of 0.8, then the amount of heat that leaves the structure in one day would be about Eout = 24 hours x (T-36) x 12' x 6'/R0.8 = 2,160 x (T-36). If the energy that enters the structure during an average day is equal to the energy that leaves the structure, ie Ein = Eout, then 2,160 x (T-36) = 116,200, so T = 36 + 116,200/2,160 = 86 F. That's a simplified calculation, but at least it seems there would be no danger of frostbite. How would the temperature change over a week without sun? Each day, the structure would lose Ed = 2,160 x (T-36) Btu, which would cool the thermal mass by Ed/C Btu, which would leave the thermal mass with a temperature of T - Ed/C: indoor heat temp Day temp (F) loss (Btu) loss (F) 1 86 108K 6.7 2 79.3 93K 5.8 3. 73.5 81K 5.0 4 68.4 70K 4.4 5 64.0 60K 3.8 6 60.2 52K 3.3 7 56.9 45K 2.8 Nick Article 47059 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.solar.thermal,sci.engr.heat-vent-ac,alt.energy.renewable,alt.home.repair,bit.listserv.geodesic,alt.architecture.alternative Subject: Yet another wide-eyed, theoretical speculation :-) Date: 29 Jan 1996 14:45:08 -0500 Organization: Villanova University This one in BASIC and metric, written for Norman Saunders, PE, whose PC is a Trash-80 :-) Nick 10 'ball park solar closet house design 20 ' 30 ' L ~10 m 40 ' ------------------------------- 50 ' | Rw ~6 | Ta ~2 C 60 ' | | 70 ' | Th ~20 C Rw| 80 ' | | 90 ' W | | 100 ' ~ 10m |Rw | 110 ' | Lc Rw | 120 ' | ------------| 130 ' | Rw Wc | Cc Atm | 140 ' ------------------------Acg----| 150 ' | Tss ~25 C | 160 ' ----------Asg------- 170 ' 180 TA=2'average December ambient temp (C) in Philadelphia 190 SUN=2.9'avg of sun falling on sunspace glazing (kWh/m^2/day) 195 GR=.2'ground reflectivity (fraction) 196 SUN=1000*(SUN+GR*SUN)'increased sun with ground reflection (Wh/m^2/day) 200 DL=6'average number of hours of sun per day 210 TH=20'house temp (C) 220 L=10'house length (m) 230 W=10'house width (m) 240 H=5'house height (m) 250 AW=2*(L*W+L*H+W*H)'outside surface area of house (m^2) 260 RW=6'average R-value of outside surface of house (m^2-deg C/W) 270 DHLC=24*(TH-TA)*AW/RW'daily conductive heat loss of house (Wh) 280 VH=L*W*H'house volume (m^3) 290 ACH =.2'average house air infiltration rate (air changes per hour) 300 DHLA=24*ACH*VH/3*(TH-TA)'daily infiltration heat loss of house (Wh) 310 KWH=100'miserly monthly electric consumption of house (kWh) 320 DHG=KWH*1000/30'daily internal heat gain of house (Wh) 330 DHL=DHLC+DHLA-DHG'daily total heat loss of house (Wh) 340 PRINT INT(DHLC/100+.5)/10, "(kWh), daily conductive heat loss of house" 350 PRINT INT(DHLA/100+.5)/10, "(kWh), daily infiltration heat loss of house" 360 PRINT INT(DHG/100+.5)/10, "(kWh), daily internal heat gain of house" 370 PRINT INT(DHL/100+.5)/10, "(kWh), daily net heat loss of house" 380 SHCFM=1'sunspace to house fan (m^3/s) 390 TSS=TH+DHL/DL/(SHCFM*1200)'average daytime sunspace temperature (C) 400 PRINT INT(TSS*10+.5)/10,"(C), average daytime sunspace temperature" 410 TSG=.92'solar transmission of sunspace glazing (fraction) 420 RSG=.16'R-value of sunspace glazing (m^2-deg C/W) 430 ASG=DHL/(SUN*TSG-DL*(TSS-TA)/RSG)'required sunspace area (m^2) 440 PRINT INT(ASG*10)/10, "(m^2), required sunspace area" 450 ND=24'number of 233 liter drums full of water in solar closet 460 CC=ND*.233'm^3 of water in solar closet 470 ATM=ND*2.32'total surface area of water containers (m^2) 480 RTM=.12'thermal mass surface R-value (m^2-deg C/W) 490 NTUF=ATM/RTM'see 1993 ASHRAE HOF, p 3-4 500 LC=4'closet length (m) 510 WC=2'closet depth (m) 520 HC=2'closet height (m) 530 AC=2*(LC*WC+LC*HC+WC*HC)'total surface area of solar closet (m^2) 540 ACG=2*3'closet air heater glazed area (m^2) 550 ANG=AC-ACG'total unglazed area of solar closet (m^2) 560 SCCFM=1'solar closet air heater fan (m^3/s) 570 'find closet water temp, after a long string of average days, with some sun 580 EIN=SUN*TSG*TSG*ACG'solar energy into air heater (Wh/day) 590 NUM=EIN+DL*TSS*ACG/RSG+(24-DL)*TA*ACG/RW+24*TH*ANG/RW'num. of Tw formula 600 DEN=6*ACG/RSG+18*ACG/RW+24*ANG/RW'denominator of Tw formula 610 TW=NUM/DEN'steady-state closet water temperature 620 EFF=EXP(-NTUF/(SCCFM*1200))'heat exchanger efficacy for closet 630 QC=EIN/DL-(TW-TSS)/RSG'net daytime heatflow into closet (W) 640 DT=QC/(SCCFM*1200)'daytime air temp diff from top to bottom of closet (C) 650 TBOT=TW+DT*EFF/(1-EFF)'temp at bottom of closet (C) 660 TTOP=TBOT+DT'temp at top of closet (C) 670 PRINT INT(10*TBOT+.5)/10,"(C), avg daytime air temp at bottom of closet" 680 PRINT INT(10*TW+.5)/10,"(C), steady-state closet water temperature" 690 PRINT INT(10*TTOP+.5)/10,"(C), avg daytime air temp at top of closet" 700 SCHCFM=1'solar closet-house fan (m^3/s) 710 TWM=TH+DHL/24/(SCHCFM*1200) 720 PRINT INT(10*TWM+.5)/10,"(C), min water temp to heat house on day w/o sun" 730 D=CC*1164*(TW-TWM)/DHL 740 PRINT INT(10*D+.5)/10,"(days), number of sunless days of thermal storage" 28.8 kWh, daily conductive heat loss of house 14.4 kWh, daily infiltration heat loss of house 3.3 kWh, daily internal heat gain of house 39.9 kWh, daily net heat loss of house 25.5 C, average daytime sunspace temperature 17.1 m^2, required sunspace area 73.8 C, avg daytime air temp at bottom of closet 69.1 C, steady-state closet water temperature 76 C, avg daytime air temp at top of closet 21.4 C, min closet water temp to heat house on day w/o sun 7.8 days, number of sunless days of thermal storage Article 4571 of bit.listserv.geodesic: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,sci.engr.heat-vent-ac,alt.solar.thermal,alt.home.repair,sci.energy Subject: Une serre pour Sylvain / A greenhouse for Sylvain Date: 9 Feb 1996 11:27:37 -0500 Organization: Villanova University Suppose Sylvain's Quebec greenhouse were a sort of quonset hut, a commercial plastic film structure, with curved galvanized pipes, that looks like this from the top: 100' . --------------------------------------- . | | | . . | An | solar | . . | terre noiratre | closet?| . . | . . . . . . . . . . . . . . . --------| 30' . 13' . | . | . . | As . white?| . . | . | . . --------------------------------------- East--> . . . . . . . . . . . shallow reflecting pool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . view from the top view from the east On an average December day in Montreal, the outdoor temperature is about 21 F and about 540 Btu/ft^2/day of sun falls on a south-facing wall. This is a not an easy climate for passive solar heating... The reflectors above will augment the sun by about 50%, so the amount of sun that falls on the south side of the greenhouse will be about 810 Btu/ft^2/day. The reflecting pool also keeps vegetation from growing on the south side, which would block the sun. It might be made from a single piece of EPDM rubber, 20' wide x 100' long, costing 30 cents/ft^2. If the glazing were glass, the pool would keep people with lawn mowers at some distance, but better still to avoid mowing at all... And the reflecting pool can collect and store rainwater for use in the greenhouse. How much heat does this greenhouse need to stay warm on an average day in December? Suppose it is a commercial greenhouse, made with curved galvanized pipes on 4' centers and two thin layers of polyethylene film, inflated with a very small blower. This would have a US R-value of 1.2. The curved surface is approximately the shape of a cylinder sliced in half lengthwise, so it has a total area of about PiDL/2 = Pi(30')100'/2 = 5,000 ft^2, divided into north and south roof/walls with An = As = 2,500 ft^2. Let's ignore the east and west endwalls and the floor for now. Suppose the temperature inside the greenhouse is 68 F, 24 hours a day. Then the amount of heat that is needed to keep it warm on an average December day is Eout = 24 (68-21) 5,000 ft^2/R1.2 = 4.7 million Btu/day. Equivalent to about 40 gallons of oil a day. That's one reason people don't build real houses out of plastic film. How much solar heat comes into this greenhouse on an average December day? According to page 64 of the $35 NRAES-33 Greenhouse Engineering book (3rd revision, August 1994, written by Robert A. Aldrich and John W. Bartok, Jr., published by the Northeast Regional Agricultural Engineering Service, 152 Riley-Robb Hall, Cooperative Extension, Ithaca, NY, 14853-5701, (607) 255-7654), poly film has a solar transmission of .92, so two layers should have a solar transmission of about .92 x .92 = .85, and the south- facing wall area of the greenhouse is about 13' high x 100' long, so the total solar energy that enters the greenhouse on an average December day in Montreal will be Ein = .85 x 810 Btu/ft^2/day x 1300 ft^2 = 891,000 Btu, about 20% of what is needed to keep this greenhouse warm... Hmmm. How about putting some insulation in the north wall? Suppose we somehow slip 3 1/2" of R13 foil-faced fiberglass insulation inside the double poly film pillow of the north wall, with the foil side facing into the greenhouse. That way, sun is reflected down from the north side, so the plants will grow fairly straight rather than always leaning towards the sun ("heliotropism.") We could paint the outside of the north plastic film white to make it last a long time. Then the daily heat requirement of the greenhouse becomes Eout = 24 (68-21) (2500/R1.2 + 2500/R13) = 1128 (2083 + 192) = 1128 (2275) = 2.6 million Btu/day, equivalent to about 22 gallons of oil a day. Better, but still about 3 times more than the available solar heat. Hmmm. Let's lower the temperature of the greenhouse at night, to, say 48 F. Then, if the December day is only 6 hours long, Eout = (6 (68-21) + 18 (48-21)) 2275 = (282 + 486) 2275 = 1.75 million Btu. Better, but still about twice as much heat as the sun will supply. Well, how about a beadwall? (Or perhaps a soap bubble wall?) If we screw on 1x2 wood strips to the inside and outside curves of the 1.66" galvanized pipes, and cover the strips with a layer of thin flat polycarbonate plastic on both sides ($5,000 worth, but it should last at least 10 years), with some butyl tape and a 1/2" x 1/8" aluminum cap strip on the outside, and fill the 3.17" cavity it with R3.5/inch polystyrene beads at night, that will give the south wall an R-value of 3.17 x 3.5 = 11 at night, so Eout = 6 (68-21) 2500/R1.2 = 588K Btu south wall, daytime + 18 (48-21) 2500/R11 = 110K Btu south wall, nightime + 6 (68-21) 2500/R13 = 54K Btu north wall, daytime + 18 (48-21) 2500/R13 = 93K Btu north wall, nightime, --------- = 845K Btu/day. OK. This is slightly less than the average solar input of 891K, so we can probably make this work. There is still a large heat loss through the south wall during the day, but this IS a greenhouse... If we somehow made it taller, we could collect more solar heat in the winter. Or perhaps we should leave the beadwall closed and turn on some grow-lights when the sun is dim, or before dawn or after dark in December, like Rudy Behrens does, ie 10 watts per square foot of high pressure sodium lights. This would add some backup heat. And in order to actually grow, vs just stay dormant in winter, plants need a longer day. With this sort of backup heat, we could probably keep this greenhouse at 68 F, 24 hours a day, which is desirable for some plants, like poinsettias. Keeping them warmer at night makes them round and bushy, vs thin and tall. Maybe this is the thing to do in Quebec, where hydroelectric power is not too expensive... BTW, I wonder if we could make this a bubble wall instead of a beadwall? Steve Baer says he's tried this with solar collectors, and bubbles transmit lots of light, in fact they even reduce the reflective losses from the glazing, by serving as an index matching fluid :-) so perhaps the bubble wall should stay in place during the day, too... But Steve also says the walls of the bubbles themselves are so thin that they don't block much radiation heat loss, so the bubbles wouldn't be great insulators for a solar collector, with a high temperature inside. But it seems to me that they might work well for a greenhouse, with a low temperature inside... Steve said someone else built a bubble wall beadwall, and published the results, and Steve was surprised at how good an insulator their bubbles were. A couple of possible problems with this approach are that the bubbles might collapse on themselves by gravity if the bubble column were more than a few feet tall, or that we might have to pump so much air and bubble water through the glazing that that mass flow would collect and transfer the heat from the inside glazing to the outside glazing, making the bubble wall a poor insulator, but Steve didn't think those would be serious problems. Perhaps the bubble wall thickness and insulating value, especially for radiation insulation, depends on the composition of the soapy water used to make them. There may be a happy medium, some nice combination of soap, detergent, glycerin, oils, dyes, etc., that will make for good shortwave solar transmission and poor longwave IR heat transmission, a good "greenhouse effect," or high-pass filtering effect, like glass. Perhaps the bubble liquid should have one composition by day and another by night. Transparent bubbles by day and opaque bubbles by night. That would not be hard to arrange. This would be an interesting science fair project, that would not require a lot of equipment to do. Making a bubble wall with polyethylene film might be a problem as far as the film life goes. Consider this quote from the CT Film application note on page I-8 of the 95-96 Stuppy Greenhouse catalog ((800) 877-5025): Soap or detergent should not be left on film. If film is washed with soap or detergent, it is recommended that immediately thereafter the film be well but carefully rinsed with water. Do not use soap containing "Pine Oil" or other solvents. Is this only a problem when the soapy liquid dries, or does the plastic degrade if it is always wet? I don't know. CT Film's sales engineer Warren Manning at (517) 423-675 may know, or he may know a chemist who knows. It would be very exciting (to me :-) if someone could make a good plastic film bubblewall. "Doing more with less," as Bucky Fuller used to say. "Pathologically frugal," my friends might say. A 4 mil thick x 32' wide x 100' long roll of polyethylene greenhouse film with a 3 year guarantee costs about $140, about 4 cents per square foot. It is recyclable, and if one uses alumimum extrusion clamps to attach it, only at the edges of the structure (this costs about 60 cents per linear foot), changing the plastic film every three years is not much harder than changing a bedsheet, on a calm day :-) BTW, Stuppy also sells a product called "Varishade 2," which turns white when it is dry and transparent when it is damp. This is a permanent product, meant to be painted on plastic films. That's another way to control solar intensity and heat losses. Poly film has almost no "greenhouse effect," unlike glass. It loses a lot of heat by longwave IR transmission (77%.) Beadwall inventor Dave Harrison suggests NOT making a beadwall out of poly film, because if the film rips or tears, the 660 ft^3 of beads that get loose may be very unpopular with the neighbors, altho they are biodegradable, as I recall. Perhaps one could make a good beadwall with a layer of polycarbonate film on the outside and a layer of polyethylene film on the inside... Anyhow, the beads cost on the order of $1/ft^3, and they would fill up 78 55 gallon drums at 8.4 ft^3 per drum, or a row along the south side, about 50 drums deep by 2 drums high, and one would need 50 vacuum cleaner motors to make all this work, if one followed the well-proven Beadwall design. They would want to be sequenced in operation, because altho they would only operate a few minutes per day, the motors use 7 Amps each... A more interesting but difficult to design alternative would have only one or two vacuum cleaner motors and some holes between the drums to make a common bead store. So, what would this finally look like? The greenhouse would be 6' off the ground, sitting on top of a row of drums stacked 2-high, on each of the long sides. The drums along the south side would be welded together and filled with beads, or perhaps a lot less bubble water, and the north side of the greenhouse would have a solar closet holding up the north benches, consisting of drums stacked 2-high and perhaps 1-deep, ie 100 drums full of water, which would have a layer of fiberglass insulation on the south side, then an airspace, then a 4' layer of polycarbonate outside of that. This might also be fed with a fan that brings down some warm air from an air heater above on a sunny day. The aisle down the middle of the greenhouse might be filled with an air duct made from 55 gallon drums welded together end to tend, laid sideways, with their tops and bottoms removed, with dirt and gravel on top to make a smooth and elevated walking surface, 4' below the benches. During the day, warm air from the peak of the greenhouse might be blown down and through this duct with one or two fans, to store that heat during the day. The north benches might as well be supported by 55 gallon drums as well, in a peninsular layout with another 200 drums, inside the bead drums. They would add some desirable thermal mass to the greenhouse, but they wouldn't store much heat, since they would be at the average greenhouse temperature. Surrounding them with a polyethylene skirt and blowing some warm air down from the peak of the greenhouse during the day would make them into a lower temperature solar closet. What would the average drumwater temperature have to be to store heat for 5 cloudy days in a row? We have 300 drums, ie about 150,000 pounds of water here (vs the 200 drums full of water that David Boyer and I put into his 2,000 ft^2 poinsettia greenhouse last fall, near Philadelphia), so the drums will store 150,000 Btu per degree F above the greenhouse temperature. With the beadwall closed, at 48 F, 24 hours a day, the greenhouse needs 24 hours (48-21) (2500/R11 + 2500/R13) = 272K Btu/day to stay warmish inside, so the average drumwater temperature has to be at least 48 + 5 x 272K/150K = 57 F. This seems very doable. The outer layer of drums on the north and south sides should be insulated, eg with 3 1/2" of fiberglass insulation, covered with poly film. The north insulation should be dark on the outside, with an airspace under the glazing. Nick Article 4611 of bit.listserv.geodesic: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.geodesic Subject: sailing and solar houses Date: 12 Feb 1996 05:48:30 -0500 Organization: Villanova University Lines: 198 Message-ID: <4fn5tu$bop@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Ian Woofenden writes, in medias res, to the alternative energy mailing list: >Nick, I know for me that the sheer volume puts me off at times. I feel the same way about press releases and legislative alerts... There should be some easy way to skip over things one is not interested in, in this sort of manual hypertext. I do try to lighten it up with humor, albeit obscurely. For those who don't know, a "facultative lagoon" is a low-energy sewage treatment structure, an aerobic-anerobic pond, perhaps with mechanical surface aerators, that accumulates sludge in the winter and decomposes it in the summer. No connection with universities, living or dead. >I was sorta hoping for a 25 words or fewer description of solar closets See below. >I think the best scientists are the ones who can boil something down >to its simplest form. Then and only then are they qualified to write >children's books on the subject. Norman Saunders seemed delighted with the part of our technical paper that described the solar closet as lying in wait, lurking, ready to spring into action on a cloudy day. He thought that read like a children's story. But some things can only be boiled down so far... It would be difficult to teach a child to design a TV. Most adults would find that a difficult task. Solar closets and sunspaces are a lot simpler than that. Designing a solar closet heating system is about as hard as designing a simple beam or a PV system. >>Perhaps a part of a deep eco/environmental commitment involves getting >>familiar with this high school physics and math. That's all it is... The >>physics is easy high school physics, and the math is easy high school math. > >Fair enough. I'm working on that. In the meantime, it might be worth noting >the overwhelming majority out there don't have that knowledge and ability. Well, if you want to do alternative energy, vs. just talk about it, I still think you have to understand this stuff. If you want to do it well, that is, ie if you want to put together good, automatic, efficient, cost-effective, low-maintenance, low-lifestyle-impact systems that people won't ask to have removed from their houses after a few years. Energy really IS a technical subject, one that people have been developing for hundreds of years, and if you turn your back on all that technical knowledge and basic physics and math, and fail to somehow embrace it, the resulting systems will suffer. The solution to ill-thought out, non-cost-effective systems is better thinking, not government subsidies, IMHO. You may have heard people say that almost anyone can design a system to solve a problem, but it takes a good engineer (not necessarily a person with an engineering degree) to come up with a cost-effective solution. >>there are no sines or cosines here, or waves, or apples >>falling to the earth, or planets moving in the sky, > >We have apples falling every fall, and the planets still move here. :) Yep. Nature does not need cosines. But people do, to understand nature. >...so far, I don't see the practical users of RE flocking to those >concentrator panels. That is partly because they are ignorant. No insult intended. >And lots of people like to get trackers for fun, Hmmm. Like sailing. Consider this quote from an ad in the February issue of the magazine "Sailing: the beauty of sail": You're hit by a squall and you're sailing in big, breaking seas. You don't want to round up to reef or lower your full batten mainsail. You just want it down. Now! With 100% reliability and no hassles. Is that possible? Yes, and only yes if you have a ball bearing batten car system. The problem with long battens is that they apply load on their cars from all directions. They push and pull and above all, they torque and twist. Slide systems, no matter how slippery, won't do the job. Recirculating ball bearings sliding in a "V" groove will roll regardless of the angle of load. Harken Battcar systems use only recirculating ball bearing batten cars and feature all new batten receptacles and headboards which are lighter, easy to remove and cost less. Insist on the system that is designed to keep your mainsail under your control. Under all conditions. On all points of sail. Not just on a sunny day at the dock. The choice is yours. Sailors have fun, but a lot of them are quite serious about it... There's a story later on in this magazine about a 40ish California couple and their 9-year old son and 7-year-old daughter who finally took their dream sailing vacation, a 5 year cruise around the world on a Compass 47 cutter, a 30,000 pound, long-fin-keel, performance cruiser, which was torn open by a freighter at 3 AM on November 24 "as a vicious northeast gale roared through the rigging," 30 miles at sea, northeast of New Zealand. "Only the wife [a civil engineer] survived, washed ashore 40 hours later. When she was found, suffering from exposure and severe back injuries, she was able to give the exact coordinates of where their boat was plowed under by the ship that had come suddenly out of the black night. Co-skipper Judy Sleavin was that kind of meticulous sailor." They practiced by going from San Diego to the Caribbean and back, through the Panama Canal, twice. In her last communication home, faxed from Tonga, _before_ they hit the 50 knot gale with 20' seas, Judy Sleavin told friends This life is by no means stressless. At times I'm more stressed than I ever thought I was capable of enduring. You guys probably laugh at this, but just think of taking your home through a small pass in the coral with a strong current and once you start the approach, there is no turning around to ditch out and meanwhile the kids are fighting over a stupid little insignificant plastic toy so loudly that you can't hear the other person calling out directions. That part of the world is known for fierce storms, "howlers and screamers," that circle around the world over water with few land interruptions. A few years ago I heard another sailor talk about sailing around the world without a compass. He had a 60' steel boat, and talked of a storm in the Tasman sea, that _pitchpoled_ the boat end for end, lengthwise, leaving it upside down with the mast sticking down in the water. He said "the boat was well buttoned-up," and, he went on calmly, "after a few minutes, she righted herself." I'd like to see more of that kind of spirit among solar house owners :-) But without the stress and fatalities. Needless to say, sailors are more interested in the performance of a boat than how it looks, altho many people find sailboats beautiful. Sailors don't worry if their boat looks different from their neighbor's boat, or looks like it wasn't built 100 years ago. They care about cost, and they care about performance. I met another courageous sailor in Annapolis, on his sailboat, all built of recycled aluminum, donated by Alcoa. It was a single-handed ocean racing yacht, built for a round-the-world race, beautiful in its way, built without any wood or fiberglass. Very strong and sleek and hi-tech and simple. No curtains or cushions below, just thick diamondplate decking below, with lots of heavy struts for strength, and a serious-looking fishing chair welded to the deck in front of a thick window looking forward, with a racing car seat belt, and a composting toilet welded to the deck a few feet away. Lots of electronics, Loran, radar, etc. With a generator to run the electronics and powerful pumps, but this boat had no propellor, just beautiful sails... The pumps were to move water fast through very large pipes from one side of the boat to the other, transferring the water between two 2' diameter 60' pipes on each side. The pipes also made the boat very strong. That was how he would balance the boat, since there was only only one crewman. On the longest passage, he said he would not sleep for two weeks. He was a licensed captain, like the Exxon Valdiz driver, as was his wife. Pat Hennin of the Shelter Institute (shelterint@aol.com) would probably call this a racing machine, as he calls solar houses solar machines. Are they beautiful? Chacun a sa machine. Third-world fishermen may dream of outboard motors, but for many people these days, sailing is something they do because they want to do it, not because they have to do it. Sailors enjoy harnessing natural forces to do something that can be done far more easily with fossil fuels. They enjoy the feelings of power and competence and getting something for nothing, in this old art which is somewhat mysterious and not easy to master, even without race competitions. Sailors do not like to use motors, even if they have one. But they almost always motor in and out of crowded harbors, because sailing into a crowded harbor is often extremely dangerous and difficult. A couple of years ago, a group of Sunday sailors on vacation in the British Virgin Islands watched a breathtaking sailing performance as a crack captain and crew sailed into the crowded harbor at Soper's hole in a moderate wind on a 60' boat, on their toes, skillfully and economically tacking and veering around many other expensive anchored boats, missing some by inches, until they dropped the sails at just the right time to allow the momentum to carry the boat into a slip and let the wind gently push their boat against the dock. They were nonchalant about this tour-de-force, as they tied up the boat to a round of applause from open-mouthed people standing nearby. This is a peculiar game, no? Trying to make a 100% solar house that uses no backup heat, or perhaps one that has no backup heating system. It is futile of course, because it can never be accomplished. No matter how fine the solar house, Mother Nature in her stochastic way will someday supply a combination of cloudy-degree-days, a new record that will exhaust her solar thermal storage capacity. It is clear to me that there is a happy economic compromise between the expected yearly backup energy required for a house (something related to the tail of a Gaussian distribution?) and the cost of building the house, but as they say, a boat is a hole in the water... >A solar closet is an insulated box filled with sealed containers of water, >with a solar air heater attached to one insulated side of the box. Oops, 26 words, but close :-) >OK, I get the basic idea. Do you have one of these up and running? Yes. I think I've said that about 83 times now. But it is fairly small, only 2' x 4' x 8' tall, and it doesn't have a water heater, altho it has a nice data logger and modem, and it isn't running at the moment because we are replacing the fans with 2 watt motorized dampers, to increase the COP. We are trying to lower the cost and beat the 50:1 COP ("98% solar power, 2% fan power") that John Christopher ((603) 756-4796) achieved in his much larger CSI building in Walpole, NH, in 1981, using DOE money. >When do we see the _Home Power_ or _Solar Today_ article? As soon as somebody builds something bigger :-) Nick Article 4626 of bit.listserv.geodesic: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.geodesic,sci.energy,alt.solar.thermal,alt.energy.renewable,sci.engr.heat-vent-ac Subject: Re: solar?, literacy, the zero, connection Date: 13 Feb 1996 11:43:26 -0500 Organization: Villanova University Lines: 103 Message-ID: <4fqf3e$833@vu-vlsi.ee.vill.edu> References: <51338.tagdi@ruulch.let.ruu.nl> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu bit.listserv.geodesic:4626 sci.energy:48275 sci.engr.heat-vent-ac:5158 >Hi Nick and the sun lovers, Hiya Tag, >what is the % heat loss from a glass window? % of what? That depends on the temperature inside and outside the window. I usually assume that a window with a single layer of glass has an R-value of 1 in US units, and use "Ohm's law for heatflow," U = (T1- T2)A/R, where U is in Btu/hour, the Ts are the temperatures on each side of the surface in degrees F, A is the area of the surface in ft^2, and R is the US R-value from one side to the other through the surface. So if it's 72 F inside and 32 F outside, and the window has one square foot of glass, U = (72 F - 32 F) 1 ft^2/R1 = 40 Btu/hour. If the sun is shining, about 300 Btu/ft^2/hour fall on the glass, as a maximum, or about 1,000 Btu/ft^2/day on a south wall in winter where I live, and I usually assume that all of that solar heat gets through the glass. If 300 goes in, and 40 goes out, the percent heat lost from the window is about 13%, and the solar collection efficiency is about 87%. Pretty good. If the temperature inside the window were 132 F, about 100 Btu/hour would be lost, and the solar collection efficiency would be 66%. Still pretty good. What would the temperature inside the glass be if the solar collection efficiency were 0%, with this simple model? Power in = power out... (Reality is more complicated.) You can do all this with watts and meters and degrees C too, BTW. >what is indices of reflection mean? That's index of refraction, or the refractive index of a material. That has to do with how fast light travels through a material. If light travels slowly through the material, people say the material has a high index of refraction, like glass. If light travels fast, as in air, the material has a low index. The lowest index is 1, in a vacuum, where light travels fast, about one foot per nanosecond, one way, or 10 microseconds per mile, round trip. Air is very close to 1. Glass and copper are close to 1.5, ie light and electricity travel about 2/3 as fast in glass and copper as in air. (Which slows down computers and makes lenses bend light.) Whenever electromagnetic waves (eg light) travel from a substance with one index to a substance with a different one, some of the light is reflected back at the interface. This is called a Fresnel loss or a reflection resulting from an impedance mismatch. The amount of reflction depends on the angle of the light striking the surface. Grazing angles make good reflections. If light hits perpendicularly on the surface of a material with index n, and the other surface is air, the fraction of light reflected at each surface is ((n-1)/(n+1)), squared, ie about 4% at each interface. Some plastics have lower indices, so there is less reflection, and glass can be treated with index matching coatings or etchings to reduce this reflection to almost zero, but that can be expensive. If a substance is very thin compared to a wavelength of light or heat, like a very thin soap bubble wall, it apparently doesn't reflect much light at all. Light that travels from a substance with index n1, and enters another with index n2, at an angle A1 from the perpendicular, enters the n2 medium with an angle from the perpendicular A2 such that n1/n2 = sin A2/sin A1. This is known as "Snell's law." (Some birds know this intuitively, as they dive for fish that look to be elsewhere.) Here is the last and most complicated part of the picture, how to predict how much energy will be reflected from a surface if the sun is not shining directly at it. For instance we might want to guess how much low-angle winter sun will be reflected from a shallow pond in the winter, onto a solar house. If light strikes a surface at angle A1 from the vertical, the fraction of energy reflected is r = (Rper + Rpar)/2, where Rper = (sin(A2-A1)/sin(A2+A1))^2, and Rpar = (tan(A2-A1)/tan(A2+A1))^2. >p.s it may be asking to much to ask those who send technical articles > to explain few words at end, i think it help the operative mind. Maybe that's a good idea. But then we wouldn't be techno-priests, would we? >2p.s m, there are 70 million who do not know how to write in the U.S Really? That's a lot... > should connection heppen in the beginning or in the end. Is this something to do with chickens and eggs? :-) Nick Article 5158 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.geodesic,sci.energy,alt.solar.thermal,alt.energy.renewable,sci.engr.heat-vent-ac Subject: Re: solar?, literacy, the zero, connection Date: 13 Feb 1996 11:43:26 -0500 Organization: Villanova University Lines: 103 Message-ID: <4fqf3e$833@vu-vlsi.ee.vill.edu> References: <51338.tagdi@ruulch.let.ruu.nl> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu bit.listserv.geodesic:4626 sci.energy:48275 sci.engr.heat-vent-ac:5158 >Hi Nick and the sun lovers, Hiya Tag, >what is the % heat loss from a glass window? % of what? That depends on the temperature inside and outside the window. I usually assume that a window with a single layer of glass has an R-value of 1 in US units, and use "Ohm's law for heatflow," U = (T1- T2)A/R, where U is in Btu/hour, the Ts are the temperatures on each side of the surface in degrees F, A is the area of the surface in ft^2, and R is the US R-value from one side to the other through the surface. So if it's 72 F inside and 32 F outside, and the window has one square foot of glass, U = (72 F - 32 F) 1 ft^2/R1 = 40 Btu/hour. If the sun is shining, about 300 Btu/ft^2/hour fall on the glass, as a maximum, or about 1,000 Btu/ft^2/day on a south wall in winter where I live, and I usually assume that all of that solar heat gets through the glass. If 300 goes in, and 40 goes out, the percent heat lost from the window is about 13%, and the solar collection efficiency is about 87%. Pretty good. If the temperature inside the window were 132 F, about 100 Btu/hour would be lost, and the solar collection efficiency would be 66%. Still pretty good. What would the temperature inside the glass be if the solar collection efficiency were 0%, with this simple model? Power in = power out... (Reality is more complicated.) You can do all this with watts and meters and degrees C too, BTW. >what is indices of reflection mean? That's index of refraction, or the refractive index of a material. That has to do with how fast light travels through a material. If light travels slowly through the material, people say the material has a high index of refraction, like glass. If light travels fast, as in air, the material has a low index. The lowest index is 1, in a vacuum, where light travels fast, about one foot per nanosecond, one way, or 10 microseconds per mile, round trip. Air is very close to 1. Glass and copper are close to 1.5, ie light and electricity travel about 2/3 as fast in glass and copper as in air. (Which slows down computers and makes lenses bend light.) Whenever electromagnetic waves (eg light) travel from a substance with one index to a substance with a different one, some of the light is reflected back at the interface. This is called a Fresnel loss or a reflection resulting from an impedance mismatch. The amount of reflction depends on the angle of the light striking the surface. Grazing angles make good reflections. If light hits perpendicularly on the surface of a material with index n, and the other surface is air, the fraction of light reflected at each surface is ((n-1)/(n+1)), squared, ie about 4% at each interface. Some plastics have lower indices, so there is less reflection, and glass can be treated with index matching coatings or etchings to reduce this reflection to almost zero, but that can be expensive. If a substance is very thin compared to a wavelength of light or heat, like a very thin soap bubble wall, it apparently doesn't reflect much light at all. Light that travels from a substance with index n1, and enters another with index n2, at an angle A1 from the perpendicular, enters the n2 medium with an angle from the perpendicular A2 such that n1/n2 = sin A2/sin A1. This is known as "Snell's law." (Some birds know this intuitively, as they dive for fish that look to be elsewhere.) Here is the last and most complicated part of the picture, how to predict how much energy will be reflected from a surface if the sun is not shining directly at it. For instance we might want to guess how much low-angle winter sun will be reflected from a shallow pond in the winter, onto a solar house. If light strikes a surface at angle A1 from the vertical, the fraction of energy reflected is r = (Rper + Rpar)/2, where Rper = (sin(A2-A1)/sin(A2+A1))^2, and Rpar = (tan(A2-A1)/tan(A2+A1))^2. >p.s it may be asking to much to ask those who send technical articles > to explain few words at end, i think it help the operative mind. Maybe that's a good idea. But then we wouldn't be techno-priests, would we? >2p.s m, there are 70 million who do not know how to write in the U.S Really? That's a lot... > should connection heppen in the beginning or in the end. Is this something to do with chickens and eggs? :-) Nick Article 49652 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,sci.engr.heat-vent-ac Subject: Re: Smart Vents Date: 14 Mar 1996 12:53:49 -0500 Organization: Villanova University Lines: 95 Message-ID: <4i9mfd$47v@vu-vlsi.ee.vill.edu> References: <4i7ih9$pdd@eplet.mira.net.au> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:49652 sci.engr.heat-vent-ac:5648 David Coote wrote: >One cheap form of AC in a house is provided by opening and closing doors >and windows depending on the temperature gradient between inside and outside. Sounds good, David. Baruch Givoni's new _Passive and Low Energy Cooling of Buildings_ talks about cooling the thermal mass of a house at night by ventilation and keeping it cool during the day with no inside-outside air exchange. To make this work well we want lots of ventilation, say 1 cfm per square foot of house. Suppose the house is 2,000 ft^2 with 3,000 ft^2 of R20 walls, and the daytime temp is 100 F, and the average temp in the house is T. Then during a 12 hour day, the house will gain 12(100-T)3,000/R20 = 180K - 1800 T Btu. If the house starts out at dawn at 70 F, and it has a thermal mass equivalent to say, 3000 lb of water, then during the day the house will absorb 180K-1800(70) = 54 K Btu, and since 1 Btu raises 1 lb of water 1 degree F, the house temp will rise by about 54K/3K = 18 F to 88 F. Let's try more thermal mass: suppose the house has masonry walls and ceiling with a thermal mass of 0.16 Btu/lb-F x 32 lb = 5 Btu/F for each 8" x 16" cement block, with R20 insulation outside. Then the walls and ceiling would have a thermal mass of about 6 x 3,000 = 18 K Btu/F, equivalent to about 18,000 pounds of water, so the temp rise would be 1/6 of the above, ie 70 F --> 73 F. That's better. The bottom and top rows of blocks might have holes in them from the inside of the house to allow house air to flow through them, increasing their heat exchange surface area. Now suppose the temp T of the thermal mass inside the house does not change at all from night to day. Suppose the night temp is 70 F and the fan is 2,000 cfm. Then during an 8 hour night, the fan would move roughly (8)(2,000)(T-70) Btu, ie 16KT - 1120K = 180K - 1800T. Solving for T, 17,800 T = 1300K, or T = 1300K/17,800 = 73.03 degrees F. Pretty cool. >If no-one's home all day the house is going to be stifling when >you get back from work. This idea is cool the house down well the night before, when the air is cooler than daytime air, and close up the house during the day and let the thermal mass of the house keep it cool. >What might be nice is a micro-processor controlled motorised vent system. >Enter the desired temperature at the system panel and let the system open >and close vents appropriately depending on internal and external temperatures. One might also use a differential thermostat to open the vents when it's cooler outside than in the house, eg a Heliotrope General ((800) 552-8838) DTT-94, which has a trade price of about $75, which would need an output relay to drive a three terminal damper, or a spring return damper. Honeywell probably makes something like this too. Or one might use a passive plastic film damper that opens itself at night, with a manual door behind it. If the house has high thermal mass and good insulation, its temperature will change slowly from day to day. This house with the masonry walls would have a natural "RC time constant" of R20/3,000 x 18K = 120 hours or 5 days. This is good for solar heating too. >The vents could be tucked away under eaves as their primary purpose is >not to let in light. They'd have to be placed so as not to let in rain. One might put them in an insulated attic floor, with reflective undersides, perhaps made of foil faced foamboard, and let them open in winter towards the sun, under a steep transparent roof, to admit light and heat. They might also act as return air dampers for solar warmed air blown down from the peak of the roof to the house in the winter. >Other considerations would include: reliability of the motors; Most damper motors, eg the $50 Honeywell 2 watt 6161B1000 actuator, have a lifetime of at least 100,000 cycles, ie 300 years at once per day. Large low-speed fans are also fairly energy-efficient. The 24 VAC version of this motor has mechanical stops and a 120 degree rotation, max, with a max torque of 45 in-lb. It has 3 terminals, a common one, one to make it go clockwise when 24 volts is applied, and one to make it go CCW. Honeywell (actually American Warming, now) make a nice D642LS "ultra-low leakage" damper that works with these, with a trade price of works with these, at a cost of $100 or so, but because of the price and the fact that it is made of metal with no insulation, I prefer making a little door out of foil faced foamboard. >how much vent area needed to get useful heat flows; The air that flows out of an A ft^2 hole in a wall h feet high, with a temp Ti (F) on the inside and a cooler temp To (F) on the outside is roughly Q = 16.6 A square root ((Ti = To) h) cfm. Q cfm of air flowing through a temperature difference of D degrees F carries about QD Btu/hour. >Anyone know of residential systems of this type? Seems like you can make up a system like this with standard Honeywell parts... >Any experience with these systems? The dampers and motors seem to work nicely. Nick Article 204 of pa.environment: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: pa.environment,sci.environment,alt.energy.renewable,alt.architecture.alternative Subject: Natural sewage treatment Date: 17 Mar 1996 16:04:39 -0500 Organization: Villanova University Lines: 120 Message-ID: <4ihup7$65@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu pa.environment:204 sci.environment:94936 I've been reading two works by Sherwood C. Reed, a Professional Engineer who lives and works in New Hampshire. US EPA Design Manual number 74, "Subsurface Flow Constructed Wetlands for Wastewater Treatment" is available for about $12 from the Small Flows Clearinghouse at West Virginia University at POB 6064, Morgantown, WV, 26506-6064, (304) 293-4191 or (800) 624-8301. This clearinghouse is largely government-supported, and I think they do a wonderful job. Here's a little quote: The proponents of subsurface inlet manifolds claim they are necessary to avoid the buildup of algal slimes on the rock surfaces and resulting clogging adjacent to a surface manifold. The disadvanatages of a subsurface manifold are the inabilitiy for future adjustment and the limited access for maintenance. In one case, a buried manifold became clogged with turtles which entered the piping system from the preliminary treatment lagoon and had to be removed. There is a lot of nice, simple math in this book, which explains how to build a natural wastewater treatment system for a home or community. You can tell what's inside _Natural Systems for Waste Management and Treatment_ by the cover, which cleverly has a small piece of gravel embedded therein, of a type that is used in the construction of artificial wetlands. McGraw Hill, 1995, second edition, ISBN 0-07-060982-9, 434 pages, about $55. The back cover says: Here is your chance to learn about biologically-based systems for handling waste that are fast becoming the technology of choice in communities and municipalities across the United States... the new edition of this classic reference will introduce you to low-cost, low-energy methods of processing waste and wastewater naturally... Here are some quotes: Serious interest in natural methods for waste treatment reemerged in the US following the passage of the Clean Water Act of 1972... The major initial response was to assume that the "zero-discharge" mandate of the law could be obtained via a combination of mechanical treatment units capable of Advanced Wastewater Treatment (AWT). In theory, any specified level of water quality can be achieved via a combination of mechanical operations, However the energy requirements and high cost of this approach soon became apparent, and a search for alternatives was commenced... ...as more and more systems were built... it was noticed that these natural systems... could usually be constructed and operated for less cost and with less energy... ...there were about 400 municipal land treatment systems using wastewater in the US in the early 70's. That number had grown to at least 1400 by the mid 1980's and is projected to pass 2000 by the year 2000. Stabilization ponds have been employed for treatment of wastewater for over 3000 years... The most common type is the facultative pond. Other terms commonly applied are oxidation pond, sewage lagoon, and photosynthetic pond. Anaerobic fermentation occurs in the lower layer and aerobic stabilization occurs in the upper layer... a continuous ice layer on a facultative pond will lower performance [but a partial ice layer on a cold day might make a very nice solar reflector--NP]... The occasional high concentration of suspended solids (SS) in the effluent... is the major disadvantage of pond systems. The solids are composed primarily of algae, not wastewater solids. Aquatic treatment is defined as the use of aquatic plants or animals as a component in a wastewater treatment system. In many parts of the world, wastewater is used for the production of fish... The floating aquatic plants with the greatest potential for wastewater treatment include water hyacinths, duckweeds, pennywort and water ferns... Hyacinths are one of the most productive photosynthetic plants in the world. It has been estimated that 10 plants could produce 600,000 more during an 8 month growing season and completely cover 0.4 ha (1 acre) of a natural freshwater surface. The rate can be even higher in wastewater ponds... The dense canopy of leaves shades the surface and prevents algal growth... The plant can survive and grow in anaerobic waters, since oxygen is transmitted from the leaves to the root mass. The attached biological growth on the root mass is similar to... rotating biological contactor (RBC) slimes. Bacteria, fungi, predators, filter feeders and detritovores have been reported in large numbers on and among the plant roots... An effective mosquito control method is to stock each basin with Gambusia or other small surface feeding fish that prey on the mosquito larvae... [Other species include goldfish, frogs, grass shrimp, blue tilapia and Japanese koi. The hyacinths are sometimes harvested and processed in a biogas digestor or used for animal feed...] ...duckweeds are the smallest and simplest of the flowering plants and have one of the fastest reproduction rates... Lemna sp. grown in wastewater effluent (at 27 C) doubles in frond numbers, and therefore area covered, every 4 days. [Not surprisingly, ducks like to eat duckweed, a lot--NP] ...duckweed can grow at least twice as fast as other vascular plants. The plant is essentially all metabolically active cells, with very little structural fiber... Duckweeds are more cold-tolerant than hyacinths, and are found throughout the world. In 1992 there were at least 15 operational wastewater treatment facilities designed specifically as duckweed systems... mosquito larvae will not be able to penetrate a fully developed duckweed mat, and are therefore not a problem... Duckweed, like hyacinth, contains about 95% water... duckweed contains at least twice as much protein, fat, nitrogen and phosphorous as hyacinth. Several nutritional studies have confirmed the value of duckweed as a food source for a variety of birds and amimals [footnote]... The harvested plants may be used directly in the wet state as poultry or animal feed. Composting... is also feasible. The aquatic animals that have been considered for use in wastewater treatment include Daphnia, brine shrimp, and a wide variety of fish, clams, oysters and lobsters... Except for the predatory fish and the lobsters, the primary function of the other species is the removal of the suspended solids or algae. Assumning that the animals are routinely harvested, this will in turn also improve nutrient removal... Fish activity is highly dependent on temperature, and most of the species... with the exception of catfish... require relatively warm water... The final lightly loaded cells in wastewater pond systems can be used for fish culture if a market for the harvested fish exists. At present, federal and state health regulations prevent the sale of such fish for direct human consumption, even though microbiological studies have not detected any contamination... major markets for this harvested material would be bait fish, pet food or fertilizer. I'm just starting to read the section on wetlands, including those enclosed by simple inexpensive commercial film greenhouses, and smaller on-site systems for houses. I'll post more about that later, along with a few BASIC programs that might help in designing these systems. Nick Article 5812 of sci.engr.heat-vent-ac: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: pipe insulation Date: 23 Mar 1996 08:17:40 -0500 Organization: Villanova University William Bahnfleth wrote: >>>The trick to doing the experimental verification, however, is maintaining >>>constant temperature at the inside surface of the insulation. That depends on what one wants to determine, no? "Is there a critical radius?" being a different question from "What is the R-value of a wire?" >>It seems to me that the temp throughout the wire would be fairly constant, >>given that copper has a much higher thermal conductivity than Teflon, etc. > >>>It might be better to do this with a copper pipes... > >>Sounds more complicated... I could see someone doing the first experiment >>in about 10 minutes, with a 20' piece of that wire, 10' of it stripped, >>strung across a room in a W, with a constant current going thru the whole >>wire and a meter to measure the voltage across each 10' section. > >What you're describing is most likely a constant heat flux condition at the >inside surface of the insulation rather than the constant inner surface >temperature condition, isn't it? I don't think it's either... >The volumetric heating due to current flow (it has to be the same >throughout the entire length of the wire, neglecting changes in R >due to temperature difference) Aha. No, I wouldn't neglect those changes at all. I would _use_ that change in electrical resistance to measure the temperatures of the wire sections, or to make the two sections have the same temperature (which may be more difficult) by measuring the voltage across each wire and dividing by the current (using "Ohm's law for heatflow," with different units :-), and the well-known fact that the electrical resistivity of copper wire is rho(T) = 1.8 x 10^-8 (1+3.9 x 10^-3(T-20)) ohm-m, where T is in degrees C. For instance AWG #30 wire has a diameter of 10 mils, (0.01"), so in SI units, the diameter is 2.54 x 10^-4 meters and the cross-sectional area is 5.07 x 10^-8 m^2, and the resistivity at 100 C is rho(100) = 1.8 x 10^-8 (1+3.9 x 10^-3(100-20)) = 2.36 x 10^-8 ohm-m, so a 30 gauge 1 ohm wire at 100 C would have a length L = R x A/rho(100) = 1.0 x 5.07 x 10^-8/2.36 x 10^-8 = 2.15 meters. The resistance of this wire at a 20 C room temp would be R(20) = R(100) x rho(20)/rho(100) = 1 x 1.8/2.36 = 0.763 ohms. EEs often measure the temperature of internal copper windings of motors and transformers by simply measuring their resistance or change in resistance. >...the one that's insulated would change in temperature to accomodate >the change in overall resistance. I guess the insulated wire would have a lower temperature in this case, in series with the dull bare wire, which would make for a lower electrical resistance and a lower electrical power dissipation, so it seems the effect we are looking to detect would be enhanced in this sort of experiment. >You can determine whether the resistance drops when insulation is added by >doing this experiment, but you still need to measure the surface temperature >of both the covered and uncovered sections of wire. It seems to me that that would be a more complicated and more difficult to control and less sensitive and different experiment... Nick (speaking ex-cathedra on matters electrical, for once :-) Nicholson L. Pine System design and consulting Pine Associates, Ltd. (610) 489-0545 821 Collegeville Road Fax: (610) 489-7057 Collegeville, PA 19426 Email: nick@ece.vill.edu Microprocessor hardware, memory, ASIC, and computer design. Telecommunication system design. Computer simulation and modeling. High performance, low cost, residential solar heating and cogeneration system design. BSEE, MSEE. Senior Member, IEEE. Registered US Patent Agent. Fluent in French. Article 226 of pa.environment: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Yet another solar heated swimming pool Date: 24 Mar 1996 13:53:02 -0500 Organization: Villanova University Lines: 152 Message-ID: <4j45me$jmk@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50021 bit.listserv.geodesic:5079 pa.environment:226 sci.environment:95677 sci.engr.heat-vent-ac:5838 So, I'm looking at the $450 15' diameter x 42" deep swimming pool in the 1993 Spring/Summer J C Penny catalog, which would contain about 619 cubic feet of water, ie about 5,000 gallons or 40,000 pounds of water... Solar pool heating is easy, compared to other kinds of solar heating, since temperatures are low, and there's a built-in thermal mass. What would it take to keep this pool warm all winter, or to make it into a huge outdoor hot tub, in the 5,500 F degree day climate where I live, near Philadelphia? The biggest problem with solar pool heating is the cover. "Solar pool covers" have low R-values, usually not more than R1, and they are tinted blue, which keeps the sun out :-) Suppose we somehow cover the pool with a fairly rigid R-20 cover, and keep it closed all the time, except when the pool is in use. The cover might be a 20' x 20' x 6" thick panel made with 2x6s on 4' centers, with 6" of fiberglass insulation inside, and 1/4" flakeboard or galvanized sheet metal on top, with some plastic-coated shiny aluminum foil on the bottom. Innovative Insulation in Arlington, Texas, sells some shiny tough foil for mobile home roofs in 4' wide rolls for about 50 cents/ft^2. The pool cover might be hinged with a pipe along the north edge, with a counterweight, so it could easily be tilted up to the south at about a 45 degree angle. This would reflect some winter sun into the pool and reduce the wind when the cover is open, but the main pool heating would come from a 4' high x 20' long piece of vertical plastic glazing along the south edge, with an air gap behind that and some dark-colored straw bales behind that, to act as a solar air heater. Suppose the pool were surrounded by straw bales, each 16" x 16" x 36", costing $2 each, eg 40 straw bales under the pool, and another 70 bales around all the sides of the pool, to make a 4' high wall around the pool, 6" taller than the pool, with an average R-value of 20 (?) The bales around the perimeter could be stacked up and mortared together like giant concrete blocks to make a deck for the pool with a wide flat edge, and the soft underside of the cover might deform and sit on the deck to make a good seal when it is closed. The straw bales under the pool itself could be spread apart to make 8 air ducts, each 6" wide x 16" deep, running from north to south along the ground, to allow solar-warmed air from the south glazing to travel across the top of the pool, under the cover, down the north back wall of the pool, between the pool and the bales, and under the pool from north to south. This might work with passive plastic film gravity backdraft air dampers in holes at the top and bottom of the straw bales behind the glazing, but a PV-powered (-:) fan would make it work better. The whole ground area should be covered with some sort of vapor barrier, eg poly film, to keep moisture out of the straw, and the tops of the ducts below the pool should have some bridging, eg 1/8" of newspaper with 3 layers of chicken wire on top of that, and an inch of sand mix cement over that. Let's ignore the heat loss from the ducts to the ground. A shallow reflecting pool made from a single piece of 10' wide EPDM rubber roofing material over a 6" earth berm around the edge would augment the sun when frozen and keep weeds from growing up in front of the glazing. It might look like this, not to scale: ^ (open) | cccccccccccccccccccc ccccccccccccccccccccHcccccCW gggggggggggggggggg g..................P _ gggggggggggggggggg <-- S g ppppppppppppppp P gggggggggggggggggg g pppp water pppp P 4' gDDDDDDDDDDDDDDDDg r ~~~~~~~~~~ g ppppppppppppppp P .........................rprrpprprprp ...................P............. |<--- 8' --->| |<--- 15' --->| P |<------ 18' ----->| key: rprprprp----ccccccccccccccccccccHcccccCW p cgsssssssssssssssssss . p is the pool r cgs ppp s . s is straw p EPDM cgs p-c- (D) -c-p HcccccCW g is glazing . rubber cgs (D) s . c is the cover . cgsp -c- (D) -c- pHcccccCW D are hot air ducts . 20' cgsp (D) ps . rp is a reflecting pool cgsp -c- (D) -c- pHcccccCW H is a hinge . cgs (D) s . P is a post . cgs p-c- (D) -c-p HcccccCW CW is a counterweight. cgs ppp s . . cgsssssssssssssssssss . rprprprp----ccccccccccccccccccccHcccccCW |<-- 8' -->|<--- 20' --->| Suppose that in winter, 1,000 Btu ft^2/day makes it into the single layer flat polycarbonate glazing, augmented 50% by the frozen reflecting pool on an average day in December. Then the solar energy input would be Ein = 1,000 x 1.5 x 4' x 20' = 120K Btu/day, Suppose that during 6 hours of sun on an average day in December, the outdoor temp is 36 F, and the pool has some sort of R0 cover that just prevents evaporation, and the air heater air and the pool water have the same temperature T. Then the energy that flows out of the pool during an average December day is Eout = 6 hours (T-36) 80 ft^2/R1 from the south glazing during the day + 18 hours (T-36) 80 ft^2/R20 from the south glazing at night + 24 hours (T-36) 400 ft^2/R20 up through the cover all day + 24 hours (T-36) 240 ft^2/R20 out through the ENW sides all day = (6x80/1 + 18x80/20 + 24x400/20 + 24x240/20) (T-36) = (480 + 72 + 480 + 288 ) (T-36) = 1320 (T-36), so if Ein = Eout for an average day, we have 1320 (T-36) = 120K or T = 36 + 120K/1320 = 126.9 degrees F. Looks good... :-) Suppose we keep the pool at 106 F, eg by allowing some of the average 30 gallons of rain per day that fall on the pool cover in PA to flow through the pool and into the reflecting pool, which would keep the pool cleaner with fewer chemicals. How much will the pool cool on a average December day with no sun? Eout = 24 hours (106-36) 80 ft^2/R20 from the south glazing all day + 24 hours (106-36) 400 ft^2/R20 up through the cover all day + 24 hours (106-36) 240 ft^2/R20 out through the ENW sides all day = (24x70x80/20 + 24x70x400/20 + 24x70x240/20) = 6,720 + 33,600 + 20,160 = 60,480 Btu. Since 1 pound of water loses 1 Btu when it cools 1 degree F, the pool temp after a day without sun would be roughly 106 - 60,480/40,000 = 104.5 F. How many 36 F days without sun would it take for the pool to reach 70 F? The pool has a thermal resistance of R = R20/720 ft^2, so its RC time constant is RC = R20/720x40,000 Btu/F = 1,111 hours or 46 days. With no sun at all, and the cover closed, the pool temperature should be about T = 36 + (106 - 36) exp(-t/46), over many days, so if T = 70, 34 = 60 exp(-t/46), or 0.57 = exp(-t/46), or t = - 46 ln(0.57) = 26 days. If it were 10 below zero outside for t days without any sun, the pool might just begin to form a thin layer of ice on top when 32 = -10 + (106-(-10)) exp(-t/46) ==> t = -46 ln(42/116) = 16.7 days. Freezing it solid from top to bottom would take another 144 Btu/lb x 40K lb = 5.76 million Btu, as the pool loses 36K Btu/day, not counting the thermal resistance of the ice layer, ie at least another 159 days with no sun, at minus 10 degrees F. Nick It's a snap to save energy in this country. As soon as more people become involved in the basic math of heat transfer and get a gut-level, as well as intellectual, grasp on how a house works, solution after solution will appear. Tom Smith Article 5855 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Re: Yet another solar heated swimming pool--a correction Date: 25 Mar 1996 07:25:14 -0500 Organization: Villanova University Lines: 43 Message-ID: <4j63ba$4e6@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50042 bit.listserv.geodesic:5086 pa.environment:228 sci.environment:95718 sci.engr.heat-vent-ac:5855 Seems like I have to go back and fix even the simplest things, even while they are still on paper, which is a good time to do that. Perhaps this post should have stewed for a couple of days before posting, but you know how it is when you get excited about an idea, especially after a dozen espressos :-) So here's the problem, in the following paragraph--not a large enough ratio of thermal mass surface area to glazing surface area, in this solar closet. That ratio should be 10:1 or so, to keep the temperature difference between the air heater air and the thermal mass low, in this system with thermal mass indirectly heated by warm air, and make the solar collection efficient, but the glazing here is 80 is ft^2, and it's really equivalent to 120 ft^2 of solar heat, with the reflecting pool, and the round pool sides are only 165 ft^2 and the pool bottom only has about 32 ft^2 of surface exposed to the sun- warmed air, so that ratio is only 2.5:1, as posted. Nobody noticed this, altho I did get some email from someone who said he "didn't do math," but we should cover the top with PV and water heating panels and use antifreeze and pumps and pipes buried in a radiant concrete floor slab under the pool :-) Please change the following paragraph: The straw bales under the pool itself could be spread apart to make 8 air ducts, each 6" wide x 16" deep, running from north to south along the ground, to allow solar-warmed air from the south glazing to travel across the top of the pool, under the cover, down the north back wall of the pool, between the pool and the bales, and under the pool from north to south. This might work with passive plastic film gravity backdraft air dampers in holes at the top and bottom of the straw bales behind the glazing, but a PV-powered (-:) fan would make it work better. The whole ground area should be covered with some sort of vapor barrier, eg poly film, to keep moisture out of the straw, and the tops of the ducts below the pool should have some bridging, eg 1/8" of newspaper with 3 layers of chicken wire on top of that, and an inch of sand mix cement over that. Let's ignore the heat loss from the ducts to the ground. Here's a fix: forget the newspaper, make the ducts a foot wide, use 30 instead of 40 straw bales under the pool and put in 100 concrete blocks with holes in them, standing on end between the ground and the chicken wire ferrocement, to act as fins to conduct heat up to the pool bottom. Each concrete block has a surface area of about 6 ft^2 exposed to the warm air, so this way, we have 80 ft^2 of glazing and about 200 + 6*100 ft^2 of thermal mass surface area to gather heat from the warm air, ie a nice 10:1 ratio. Nick Article 5861 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Re: Yet another solar heated swimming pool--enhancements Date: 25 Mar 1996 13:32:52 -0500 Organization: Villanova University Lines: 49 Message-ID: <4j6osk$a30@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <4j63ba$4e6@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50060 bit.listserv.geodesic:5090 pa.environment:229 sci.environment:95758 sci.engr.heat-vent-ac:5861 Nick Pine wrote: >The straw bales under the pool itself could be spread apart to make 8 air >ducts, each 6" wide x 16" deep, running from north to south... >Here's a fix: forget the newspaper, make the ducts a foot wide, use 30 instead >of 40 straw bales under the pool and put in 100 concrete blocks with holes in >them, standing on end between the ground and the chicken wire ferrocement, to >act as fins to conduct heat up to the pool bottom... Better yet, forget the ducts and cement blocks and ferrocement, just build the platform from strawbales and use a tiny pump and a 20' x 4' length of SolaRoll, the EPDM rubber swimming pool tube-mat collector, under the south edge vertical glazing. Better yet, forget the store-bought pool and put a treated wood 2x4 frame around the straw bales and line an 18' x 12' x 4' inner cavity with a single piece of 20' wide EPDM rubber, folded up like a Chinese takeout box, so it has no seams. Better yet, make the solar collector out of another single piece of EPDM rubber folded once into a 4' high x 12' long x 1" thick vertical V, with the sides and top sealed in a 2x4 sandwich with silicone caulk between the rubber sheets, a la Sven Tjernagel's 470 Pennsylvania site-built solar collectors, (some still going strong), but vertical vs slanted, and filled with water, vs a trickle down system, with some chicken wire under the north sides of the 2x4 to limit the rubber bulging, and some glazing screwed to the south sides of the 2x4s. Better yet, make an 20' wide x 16' long x 16' tall cube with 4 of these 20 x 8 x 8' boxes, using 2 16' long x 8' tall site-built EPDM collectors on the south face, 2 6 gpm pumps each having an 8' head capability, and 4 internal water cavities, each 16' long x 8' wide x 6' deep, to store 24,576 gallons of water at 130 F, ie 10 million Btu of solar heat for a nearby house for a whole cloudy winter. This might be nice under a 16' x 16' walkout deck, on the west side of a house... If one were going to drink the water, the inner tank liners might better be pond liner material, not EPDM, and the collectors might contain propylene glycol "edible antifreeze," with a heat exchanger inside the tanks. The pumps could be PV-powered of course. ("Bad move," says Sven Tjernagel :-) Nick It's a snap to save energy in this country. As soon as more people become involved in the basic math of heat transfer and get a gut-level, as well as intellectual, grasp on how a house works, solution after solution will appear. Tom Smith Article 50127 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy Subject: Re: Solar energy Date: 27 Mar 1996 05:27:18 -0500 Organization: Villanova University Lines: 63 Message-ID: <4jb566$avt@vu-vlsi.ee.vill.edu> References: NNTP-Posting-Host: vu-vlsi.ee.vill.edu Brain :-) Hendricks wrote: >Does anyone know how to calculate the solar intensity on a flat surface as >a function of frequency, date, solar time, environmental conditions? I don't think so, but you might try looking in the second (Wiley, 1991) edition of Duffie and Beckman's _Solar Engineering of Thermal Processes_. They have some statistical clues. >By environmental conditions I mean cloud cover, atmospheric density, and >anything els I have forgotten. Cloud cover is hard to predict, but easy to measure. You may have forgotten fog, rain and snow. Snow on the ground can make vertical collectors work a lot better. Fog is less helpful. You can find averages based on 30 years of historical data for 239 US cities in NREL's _Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors_, which may still be available free on paper or floppy disks from Steve Rubin at rubin@tcplink.nrel.gov (303) 275-4099 This info is also on their web page, I think, as well as "typical meteorological years," for those cities, ie hourly weather data for a typical year in each city. The raw data itself, or a good simulation thereof, is available on 3 $130 CD-ROMs (East, Midwest, and West) in hourly form for the last 30 years, from orders@ncdc.noaa.gov. >I am trying to write a program to evaluate different panel designs. "Solar panels" seem economically useless these days, especially if they are mounted on roofs in cold air and they use pumps and electrical energy to run the pumps and piping and antifreeze and tanks and heat exchangers, and cost $30/ft^2 for the panels alone, and only collect $1/ft^2/year of solar heat. PV economics is far worse, today, and likely to remain so, with oil companies making PVs and electrical utilities getting interested in PVs. Altho they CAN make microeconomic sense if you live far from the power lines or get a government subsidy, ie take money out of everyone elses' pockets to make your system "economical." On the other hand, the right kind of passive solar house heating makes good economic sense to me, at a cost of <$0.01/peak watt, today, with a LOWER first cost than conventional house construction, eg with some south "solar siding" or a steep south polycarbonate plastic roof, over rafters on 4' centers, with no shingles or sheathing, and a lot less labor... (I guess you could put some amorphous PVs under the rafters with a long galvanized water tank tucked up under the insulated peak of the roof, if you were wealthy, and so inclined to spend money.) >I have looked at the ashrae handbook of fundamentals and it doesn't make >sense to me. That's a fine book, but it's hard to predict the weather... Nick The fourteenth-century Byzantine saint Sabas pretended to be deaf, dumb and mad--a pretense that he kept up with great skill for 20 years. Yet he could not escape the danger of fame. On visiting Cyprus, he reacted to the attention given to him by large crowds by suddenly sitting down on a dung heap, where he spent the remainder of the day. The emperor of Constantinople sought to persuade him to accept the office of patriarch, but Sabas refused. He refused even to be ordained as a priest. When the emperor attempted to have him ordained by stealth, Sabas fled; keen to have the saint remain, the emperor had to chase after him, beg his forgiveness, and solemnly promise to make no further attempts to interfere with Sabas's saintly ways. from _Holy Madness_, by Georg Feuerstein Article 50130 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy Subject: Re: solar assist for hot water heater - would it work? Date: 27 Mar 1996 05:52:00 -0500 Organization: Villanova University Lines: 51 Message-ID: <4jb6kg$b2i@vu-vlsi.ee.vill.edu> References: <4jaf9c$qi2@cliff.island.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Lorne Collicutt wrote: >1. Is it possible to have a solar cell on your roof help lower >the $ of keeping water in your electric hot water tank hot? Sure. How about this? . clear corrugated . i T i . polycarbonate--> . . . . . <--PV panel . . . . Note this is IN the roof, not on the roof. To me, solar panels on the roof make no sense today, economically. Altho if they were up there anyway, one might add a 2:1 reflector under an extra layer of glazing, and trickle some water over them. But it seems better to use 4' x 12' polycarbonate "shingles" for the roof with Stanford Ovshinsky's new 5%-efficiency electroplated "PV shingles" in long strips UNDER the rafters, and put some insulation up in the ridge peak, with a long galvanized water tank up there under the insulation, with no insulation underneath the tank, so the tank is heated by solar hot air from the shingle-PV cavity, when the tank water temp is low, and when the tank is warm enough, some sort of damper with a bimetallic spring opens near the top of the cavity to let the PVs run cooler. In a cold climate, this steep south transparent roof could also make hot air for the house under the insulated attic floor, and perhaps some daylighting. And it would cost less than a conventional roof. >2. Are the purchase and installation costs and headaches worth the $? No. It's much more cost-effective to replace the PVs with some dark-colored insulation board, today. Of course, one could heat water with PV elecricity, while throwing away 90% of the rest of sun's power as heat :-) Nick The fourteenth-century Byzantine saint Sabas pretended to be deaf, dumb and mad--a pretense that he kept up with great skill for 20 years. Yet he could not escape the danger of fame. On visiting Cyprus, he reacted to the attention given to him by large crowds by suddenly sitting down on a dung heap, where he spent the remainder of the day. The emperor of Constantinople sought to persuade him to accept the office of patriarch, but Sabas refused. He refused even to be ordained as a priest. When the emperor attempted to have him ordained by stealth, Sabas fled; keen to have the saint remain, the emperor had to chase after him, beg his forgiveness, and solemnly promise to make no further attempts to interfere with Sabas's saintly ways. from _Holy Madness_, by Georg Feuerstein Article 5907 of sci.engr.heat-vent-ac: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,alt.solar.thermal Subject: Strawbale/EPDM solar heat storage Date: 28 Mar 1996 16:44:01 -0500 Organization: Villanova University >...Better yet, make a 16' wide x 16' long x 16' tall cube with 4 of these >16 x 8 x 8' boxes, using 2 16' long x 8' tall site-built EPDM collectors on >the south face, 2 6 gpm pumps each having an 8' head capability, and 4 >internal water cavities, each about 13' long x 6' wide x 6' deep, to store >15,000 gallons of water at 130 F, ie 6 million Btu of usable solar heat for >a nearby solar house for a cloudy month. This might be nice under a 16' x 16' >walkout deck, on the west side of a house, or as a house foundation... Still thinking about how to build this, and how well it would work. Suppose the bale walls were R40, and the average temp in December were 36 F, and the average sun on a south wall were 1,000 Btu ft^2/day, augmented 50% by ground reflection. Then our 16' cube with water at temp T inside might receive about Ein = 16' x 16' x 1,000 x 1.5 = 384K Btu/day, and lose, over an average day, Eout = 6 hr (T-36) 256 ft^2/R1 from the south wall, daytime + 18 hr (T-36) 256 ft^2/R40 from the south wall, at night + 24 hr (T-36) 256 ft^2 x 4/R40 from ENW walls and roof, all day = (1536 + 115.2 + 614.4) (T-36) = 2265.6 (T-36), so if Ein = Eout, T = 36 + 384K/2265.6 = 205.5 F. This looks good, but it probably won't get that warm without a selective surface in the solar collector. On the other hand, iron oxide is a somewhat selective surface... We might start out with a straw bale box. My neighbor Ray Lehman sells rye straw bales about 16" wide x 16" deep x 3' long for $1.75 each, delivered, and rodents are not fond of rye straw, from what I hear. He also has some 4' tall and 4' wide and 8' long bales... Each of the 4 cube modules would be 16' wide x 8' deep (or 8" deeper, since the internal wall of the completed cube would only be 1 bale wide) x 8' tall, and one bale thick all round. The bottom would be about 5 bales long x 6 bales deep, ie 30 bales, the south wall would be 5 bales long x 5 bales high, another 25 bales, and the east and west walls would each be about 3 bales long x 5 bales high, 85 bales total, at a cost of about $150. Now we need an EPDM rubber liner, something like this: | 30' | EPDM comes in 20' wide rolls. --- . . . . The liner might cost 28 cents 2'. 6' . 14' . 6' . 2' per square foot, ie another $150 ..U.....L.............L.....U.. or so. It would be folded up . . . . like a Chinese takeout box 19' . . 7'. . inside the straw box, so it . . . . would have no seams. The points ..U.....L.............L.....U.. marked L here would be the . . 6'. . bottom 4 inside corners of the --- . . . . straw box. The rubber would fold over along a NW crease at points U to lay flat on the upper edge of the bale sides... The EW upper edges of the rubber would be clamped in a 2x4 sandwich along the top edge of the NW walls. The liner might want to be a vinyl swimming pool liner, not EPDM, if this is potable, eg rainwater. (BTW, this ascii sketch makes more sense if seen in a non-proportional font, eg courier on a Mac.) This sides of the box need some reinforcement to hold back the water pressure. The sideways water pressure at the bottom of the box would be about 60 pounds per square foot, diminishing to 0 psf at the top, so an 8' vertical wall stud on 4' centers would have a total load of 960 pounds, distributed towards the bottom of the stud. Using simple uniform load beam formulas, we might design the studs with L = 8' span, f = 1000 psi, max fiber stress in bending, w = 30 psf uniform load, oc = 4' on center spacing, W = w x oc x L = 960 pounds total load, M = W x L x 12/8 = 11520 in-lb bending moment, S = M/f = 11520/1000 = 11.5 in^3 section modulus, b = 1.5" beam width, and d = sqrt(6S/b) = 2.76" beam depth, so a 2 x 4 may work... Something also needs to keep the box from becoming a circle, as we look at it from above, eg some some perimeter sill plates, perhaps with a dacron rope crossing the box NS in the middle at ground level on top of the vapor barrier, connecting the plates. Now, how do we make the vertical EPDM rubber collectors? Perhaps fold a 16' long piece of 20' EPDM rubber in half, to make a U with a 16' crease at the bottom, leaving 2' of rubber sticking out on one long side, to overlap the north top edge of the bale wall. Then assemble the wall, screwing 2 horizontal 16+' long pieces of 4' wide, 26 gauge sheet metal to the insides of the studs, leaving a 3" bulge in each 4' cavity, and attach the outer top edge of the rubber to the top edge of the 16' long x 8' high stud wall, and tilt it up. Then caulk the EW vertical edges of the rubber bladder on the inside, attach a pipe to the top and bottom edges, and squeeze them together in a wood sandwich, somehow attaching the sheet metal firmly as well, so that when the wall is tilted up, and the top edges of the bladder are also sealed in a sandwich, the rubber bladder will contain an inch of water from south to north when filled, and attach a single layer of polyethylene plastic to the north sides of the 2x4s. The bottom edge of the tank might look something like this: glazing |metal epdm ^ ^ ^ g |me e g |meeeeee g-----|m----- straw | 2x4 |m 2x4 | -| |m |- =| | B O |m L T | | - |m |- | |m | ........................... ----- ----- ............................... How thick would the metal sheet have to be? A 1" strip near the bottom would have to support a side load of about 8' * .43 psi/ft x 48", or 160 pounds, over a 4' distance. If it were made of 40K psi steel, with an intentional 3" bulge in the middle, the left and right sides of the strip would each have a tension of about 24/3" x 160/2 = 640 pounds, so the metal would have to be about 640/40K = 0.016" thick, ie 1/64th of an inch thick. It would have to be carefully attached to the 2 x 4 sandwich, with lots of screws and washers... The inner horizontal layer of this tank might have a large piece of EPDM rubber covering the whole straw structure, from outside edge to outside edge in both directions, with the rubber drooping about a foot down into the tank to rest on top of the water. One might then put top support floor joists on the tank walls on 2' centers, on top of that rubber, the kind that look like this: | ~8' | --- ................................ ~1' . . --- ...................... | ~7' |, with some plywood or OSB on top of that to hold up the tank above. The second story walls would take about 55 more bales. The top tank roof might have the space around these floor joists filled with polystyrene beads. Yes there are a few more details here :-) If this box were also used for sewage treatment, it might have only a single layer of rubber covering the north side of the straw, with a small aerobic wastewaterfall leaking over the 14' north side of the tank, to trickle down the rubber, which would take a little more pump power. We could also use more details about some good way to heat the water directly with sun-warmed air, with some sort of fins under the water tank, to remove the heat from the air and conduct it to the water via some sort of thermally-conductive surface under the rubber, eg ferrocement over some chicken wire and straw, or a corrugated iron layer with a layer of concrete poured on top, so we don't have to build this EPDM solar collector. Nick When we play tennis or walk down stairs, we are actually solving whole pages of differential equations, quickly, easily, and without thinking about it, using the analogue computer which we keep in our minds. What we find difficult about mathematics is the formal, symbolic presentation of the subject by pedagogues with a taste for dogma, sadism and incomprehensible squiggles. from _Structures: Or Why Things Don't Fall Down_ by J. E. Gordon, a Da Capo Press paperback Article 48 of alt.energy.renewable: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.geodesic,sci.energy,alt.photovoltaic Subject: Re: Tracking houses Date: 31 Mar 1996 05:25:54 -0500 Organization: Villanova University James Fischer again condescends: > The astute student would have asked about the wind. Perhaps you didn't see this at the end: >With the right combination of strong and elastic ropes and >mass and damping, vulnerability should not be a problem. > A PV array (or a PC treehouse), if suspended by cables, would be > thrown off by the wind. True. But how much and how often? Being thrown off by 10 degrees once in a while may make little difference. This is a numerical question. > Even the commerical-grade tracking solar > panel racks have problems with the wind. A PV panel acts like > an airfoil. This is why successful PV installations have polar > mounts (a "polar mount" is a pole that points at the north star > for those who might not know the term), massive counterweights, > and lots of concrete to anchor them. Even then, the darned > things tend to "drift" in the wind. Contrary to what you say, the ones that use motors tend to be more stable this way, not less, than Steve Baer's passive trackers, which will steadily point with an offset sun angle in a steady wind. > A better approach (but using some electricity) is a "seeker" > toy, which uses 5 (or more) CDS cells, each at the bottom > of a short tube. The CDS cells should be arranged like this: > > 0 > OOO > O This is 50's technology, James. Today people use CCD arrays and microcomputers that know what time of day it is. > I love junkyards! We can tell. > To be 100% honest, I would hold off on buying ANY solar panels > for the next 2 years (unless you MUST have them now). I have > been sent a small test sample of what will soon be the ultimate > PV material: > > - You shingle the south side of your roof with it > - You buy it in rolls > - It is cheap - nearly as cheap as shingles in the > sort of quantities that would be appropriate. > > When one can make one's entire roof into a solar panel, optimization > hacks like "tracking" become a moot point. Yeah yeah yeah, the big pricethrough is "just around the corner..." Or is it? I wonder, given the email below, posted with Pali's permission. Date: Thu, 28 Mar 1996 15:02:03 -0500 To: nick@ece.vill.edu (Nick Pine) From: "Dr. P. Singh" Nick: I have a couple of corrections to make to your statements about my PV research and Ovshinsky's panels. I am working on electroplated solar cells on transparent substrates. The electroplating process is a low temperature process (60 C) and so could potentially be used on plastic substrates with a transparent conducting oxide (such as tin oxide or indium tin oxide) as the transparent contact. This would allow potentially low cost devices to be manufactured since the process and materials costs could both be very low. The transparent substrate would also allow heat to pass through so that the use of these devices in a hybrid electrical/thermal system would be a great idea. It also makes a lot of sense to use these types of PV cells in a hybrid solar collector with a heat exchanger because that would allow the cells to operate a little more efficiently !! I will keep you informed as to how the research is going but don't hold your breath - after all it is research and may take a few years to get to a point before it is commercially viable. In terms of Ovshinsky's cells, these are amorphous silicon alloys that are made by a plasma assisted chemical vapor deposition process. Those big chambers that you have seen that look like a newpaper press are in fact evacuated chambers in which gases of SiH4, GeH4, CH4, PH3 (phosphine), AsH3(arsine) and B2H6 (diborane) flow. An RF plasma is used to break down these gases and the Silicon, germanium, carbon, hydrogen and dopant components are driven to the stainless steel substrate by the capacitive DC self-bias between anode and cathode capacitor plates. The multiple chambers are used to deposit individual layers of a device that may have as many as 10-12 layers !! This is not an inherently cheap process in small scale production (<10MW/yr.) and so the selling price of $4.50 a peak Watt is about the production price of these cells. (USSC is very secretive about its books and so the exact production price is erally not known but Solarex's Thin Film Division makes a similar product and they are selling the cells for more than it costs to make them). As far as I am aware only the Solarex polycrystalline silicon cell division is making money as a solar cell manufacturer and they are selling at about $3.50 a peak Watt for large orders. There is a joint venture between Enron Corp. and Amoco (Solarex's parent company) to make a 10 MW/yr. thin film PV manufacturing facility in Virginia. Until now the amorphous silicon community has said that the cost of amorphous silicon PV will drop dramatically (down to less than $1/Wp) if they could take advantage of economies of scale and produce at least 10MWp/yr. Enron has called their bluff and so let's see what happens !! Keep posted. In the meantime Solarex's polycrystalline silicon cell division is ramping up to increase their production capacity three-fold and Siemens Solar (what used to be ARCO Solar) is also increasing production. So there is a growing market for PV but primarily for remote applications in developing countries. I agree that we should start any solar home design with trying to meet the heating load of a house through good passive solar design (after insulating the house as well as possible) and then look to fund PV to supply the necessary but small electric load (if economically justified). I'm still looking for students for solar home projects - I'll let you know if I get any bites. Best regards, Pali Singh Article 253 of pa.environment: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Two views on sunspace design Date: 2 Apr 1996 10:37:40 -0500 Organization: Villanova University It is hard to think of any other system that supplies so much heat (to an existing house) at such low cost... One could shorten the warm-up time of the enclosure and increase the amount of heat delivered to the rooms by making the enclosure virtually massless--by greatly reducing its dynamic thermal capacity. This can be done by spreading a 2-inch-thick layer of lightweight insulation on the floor and north wall of the enclosure and then installing a thin black sheet over the insulation. Then, practically no heat is delivered to the massive components of floor or wall; practically all of the heat is promptly transferred to the air. And since the thermal capacity of the 100 or 200 lb. of air in the room is equal to that of one fourth as great a mass of water (about 25 to 50 lb. of water), the air will heat up very rapidly. I estimate that its temperature will rise about 40 F. degrees in about two minutes, after the sun comes out from behind a heavy cloud cover. At the end of the day, little heat will be "left on base" in the collector floor or north wall and, accordingly, the enclosure will cool off very rapidly. New Inventions in Low Cost Solar Heating-- 100 Daring Schemes Tried and Untried by William A. Shurcliff, PhD Brick House Publishing, 1979, 293 pages, $12 A sunspace has extensive south-facing glass, so sufficient thermal mass is important. Without it, the sunspace is liable to be uncomfortably hot during the day, and too cold for plants or people at night. However, the temperature in the sunspace can vary more than in the house itself, so about three square feet of four inch thick thermal mass for each square foot of sunspace glazing should be adequate... The sunspace floor is a good location for thermal mass. The mass floors should be dark in color. No more than 15-25% of the floor slab should be covered with rugs or plants... Another good location for thermal mass is the common wall (the wall separating the sunspace from the rest of the house)... Water in various types of containers is another form of energy storage often used in sunspaces. Passive Solar Design Guidelines-- Guidelines for Homebuilders for Philadelphia, Pennsylvania Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates Current edition, 88 pages, $50 So, which is the most energy-efficient sunspace in a partly cloudy climate like Philadelphia? Shurcliff's plastic film sunspace, wearing the green uniform in this contest, might cost about $2/ft^2 and begin an average December day at 36 F, and like the PSIC sunspace, it would receive about 1000 Btu/ft^2/day over the average day. Let's assume that both sunspaces have a perfectly insulated wall between them and the house, to avoid the thermal disaster of a poorly insulated Trombe wall in a partly cloudy climate. (Trombe walls can't even get to the starting line in this race.) And that there is no air infiltration from the outside in either case. Shurcliff's sunspace air would be circulated through the house with some dampers or fans, keeping the sunspace at 80 F, say, while the house remains at 70 F. With single glazing, about 900 Btu/ft^2 of sun might enter the sunspace during the day, and the amount of heat lost through a square foot of Shurcliff's sunspace over a typical 6 hour December day would be about 6 hr (80-36)/R1 = 264 Btu/ft^2/day, for a net gain of 636 Btu/ft^2, ie his $2/ft^2 sunspace would be about 64% efficient, as a solar collector. As an auxiliary living space, it could be heated up instantly on some starry night for a party, by moving some warm air from the house into the sunspace. A PSIC sunspace, wearing the brown uniform, would perform better with double glazing. He might cost $10/ft^2. Say his thermal mass is poured concrete, 4" thick, with an official PSIC heat capacity of 8.8 Btu/ft^2, and say it absorbs 100% of the sun that falls on it, vs the official PSIC solar absorptance of bare concrete of 0.65 (table K, page 57.) Then about 800 Btu/ft^2/day of sun will enter the double glazing and be absorbed by the concrete, and the concrete surface will warm up the sunspace air, and that warm air can be used to heat the house when the sunspace temperature is more than 80 F. Suppose the concrete loses no heat at all to the soil below (I'm giving quite a few handicaps to the PSIC sunspace in this efficiency race.) Suppose the PSIC sunspace starts out the day at temperature T, and the concrete charges up in the sun to a maximum temperature of T + dT, and returns to temperature T at dawn, on an average day in December. How can we calculate T and dT? We have an equivalent electrical circuit that looks something like this: Ts sunspace temperature | R2 | S 36 F ---------wwww-----------------|-------------------- 70 F outdoors glazing | open switch to heat house | w w R0.5 concrete - sunspace air resistance 800 Btu/ft^2 w per day | | --- | | | ----|-->|------|--Tc concrete temperature | --- | sun current w source w R0.4 concrete bulk thermal resistance w | ------- 8.8 Btu/F thermal mass of concrete ------- | | --- - Let's simplify this, by assuming the thermal mass of the concrete is infinite, vs 8.8 Btu/ft^2/F. Lots of concrete, or a water wall, or something that has so much thermal mass that the temperature inside the sunspace never changes at all from day to night or day to day over a long string of average December days, with some sun. This is an optimal sunspace with more than "adequate" or "sufficient" thermal mass by official PSIC standard guidelines. Let's also assume that the two small resistors have a value of zero, ie let's assume the the R0.4 bulk thermal resistance of the concrete, that makes the surface heat up more than the inside, while the sun is warming it up, and makes it harder to get heat out of the inside of the concrete and into the sunspace air, and the R0.5 concrete-sunspace air resistance, are both R0 conductors. What will Tc be in that simplified case? The sun shines into the sunspace during the day and adds 800 Btu to our concrete capacitor, and over 24 hours, 24(Tc-36)1ft^2/R2 = 12 Tc - 432 Btu flow out of the capacitor. If Ein = Eout (providing no heat for the attached house), then Tc = (800+432)/12 = 103 F. Pretty nice, but this sunspace is not providing any heat for the house, just keeping itself warm on an average day, and losing lots of heat on a cloudy day. Suppose we allow some heat to flow from the sunspace into the house, ie close the switch, ie turn on the fan or open the damper between the sunspace and the house often enough to limit the maximum sunspace temp to 80 F instead of 103 F. Then the heat loss to the outside world over the course of a day is 24(80-36)1 ft^2/R2 = 528 Btu, and the rest of the heat that enters the double glazing, ie 800 - 528 = 272 Btu/ft^2/day goes into heating the house, so the solar collection efficiency of this $10/ft^2 sunspace in terms of useful heat provided for the attached house is 27%. As an auxiliary living space, the temperature of this sunspace is largely out of our control. It takes a long time and a lot of house heat to warm it up on an evening or cloudy day, and after we leave the space, it stays warm for a long time, giving up precious house heat to the outside world. How curious that by carefully following the current official guidelines of the Passive Solar Industries Council, we can reduce the performance of Shurcliff's low-thermal-mass sunspace from 64% to 27%, while increasing the price from $2/ft^2 to $10/ft^2, unimproving the cost-effectiveness of the sunspace by a factor of 12, even with all these PSIC-slanted assumptions... Here's a quote from the Acknowlegements section of the PSIC guidelines: _Passive Solar Design Strategies: Guidelines for Home Builders_ represents over three years of effort by a unique group of organizations and individuals. The challenge of creating an effective design tool that could be customized for the specific needs of builders in cities and towns all over the U. S. called for the talents and experience of specialists in many different areas of expertise. _Passive Solar Design Strategies_ is based on research sponsored by the United States Department of Energy (DOE) Solar Buildings Program, and carried out by the Los Alamos National Laboratory, the National Renewable Energy Laboratory (NREL)... and the Florida Solar Energy Center (FSEC.) The National Association of Home Builders (NAHB) Standing Committee on Energy has provided invaluable advice and assistance during the development of the Guidelines. Valuable information was drawn from the 14 country International Energy Agency (IEA) Solar Heating and Cooling program, Task VII on Passive and Hybrid Solar Low Energy Buildings... Although all the members of PSIC, especially the Technical Committee, contributed to the financial and technical support of the Guidelines, several contributed far beyond the call of duty. Stephen Szoke, Director of National Accounts, National Concrete Masonry Association, Chairman of PSIC's Board of Directors during the development of the Guildlines; and James Tann, Brick Institute of America, Region 4, Chairman of PSIC's Technical Committee during the development of these guidelines... gave unstintingly of their time, their expertise, and their enthusiasm. Nick Article 5976 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.engr.heat-vent-ac Subject: Re: GOOD SOURCE OF ENERGY Date: 3 Apr 1996 03:35:03 -0500 Organization: Villanova University Lines: 36 Message-ID: <4jtd7n$m3f@vu-vlsi.ee.vill.edu> References: <4js9nj$43d@pegasus.odyssee.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Mel Lopes wrote: >During the last 8 months I have been measuring the temperature of >the sewer across from my street. Gee Mel, what an interesting hobby :-) I built a small sewage treatment plant in my front yard a couple of years ago, with some trash cans and air pumps and heaters and metering pumps, and a sand filter and ferric chloride drip. I didn't have a real sewer to play with... >For reasons not clear to me during the winter the temperature was >consistently more than 20 degrees c (68 f) That I can understand. Showers, dishwashers, laundry... Condensed steam? >and during the summer about 8 degrees C ( 47 f for our american friends ) That seems strange. Perhaps the St. Lawrence river flows through your sewers during the summer? >Un ideal source for a heat pump. Oui. Si on peut eviter la corrosion et l'isolation des ordures. >Is anyone else interested on this subject ? It sounds like a great idea, but it seems simpler to pump in some Montreal city water, cool it a bit in the winter, in a special tank with a water-water heat exchanger (?), so there is little danger of contamination, and pump it back out to the street... Perhaps you could get permission to do this on an experimental basis. Nick "La science a besoin d'air puree'" Article 81 of alt.energy.renewable: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,sci.energy,alt.solar.thermal,alt.solar.photovoltaic,pa.environment,alt.architecture.alternative,alt.home.repair Subject: Re: solar water heater sources Date: 4 Apr 1996 06:59:17 -0500 Organization: Villanova University Lines: 213 Message-ID: <4k0dil$9ob@vu-vlsi.ee.vill.edu> References: <4jv558$90q@its.hooked.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu alt.energy.renewable:81 sci.energy:50324 alt.solar.thermal:13 pa.environment:257 alt.architecture.alternative:110 alt.home.repair:664 Hla Tin wrote: >If anybody knows the sources for 50 gallon solar water heaters >please let me know. I have a need for these for a developing country. >I am located in California and would prefer a Calif. source. How about combining PV and water heating? . clear corrugated . i T i . polycarbonate--> . . . . . <--PV panel . . . . In other words, use 4' x 12' Dynaglas polycarbonate "shingles" from SPS in San Jose, CA (408) 997-6100 or Replex (800) 726-5151 for the roof with Stanford Ovshinsky's new 5%-efficiency "PV shingles" in long strips UNDER the rafters, and put some insulation up in the ridge peak, with an 8' long x 6" diameter galvanized steel or PVC pipe water tank up there under the insulation, with no insulation underneath the tank, so the tank is heated by solar hot air from the shingle-PV cavity, or say, 2 GPM of water trickling over the 6 m^2 (?) of PVs, collecting in a small gutter and being pumped back up to the tank, with a tiny PV-powered pump, when the tank water temp is low, with some sort of damper with a bimetallic spring that opens near the top of the cavity to let the PVs run cooler, when the tank is warm enough, eg the $11 AFV-1B automatic foundation vent made by Leslie-Locke of Atlanta (gee, what a run-on sentence :-) Except for the PV part, this is cheaper than conventional roof construction, and in a cold climate, it could provide daylighting and space heat for the house beneath, if a reflective motorized return air damper in the insulated attic floor, hinged on the north side, tilted up to the south and a fan blew air down from the attic peak through one of the PV cavities, in sunny times. Ovshinsky shingles are made in California, and make about 50 w/m^2 in peak sun at 25 C, according to engineer Jim Young at United Solar (800) 397-2083, who says this only decreases to 45 w/m^2 at 60 C. He says the current retail price of their least expensive product is about $4.50/peak watt. Nick PS: I would guess these shingles won't get cheaper quickly, from this email dialog with Villanova University's Professor Singh, posted with permission. Date: Fri, 29 Mar 1996 10:08:16 -0500 To: nick@ece.vill.edu (Nick Pine) From: "Dr. P. Singh" Subject: Re: inexpensive PVs... Nick: I am glad to see that you are getting some opportunities to contribute to a few solar home designs. I have still not found a student group to work on the solar shed - as soon as I do we'll follow up on that project. >He didn't mention that it was that complex, and I'd gotten the impression >somehow that the substrate was ordinary cheap mild steel... Ovshinsky's panels used to use a Japanese steel because they could not find an American steel manufacturer that made steel with a smooth enough morphology to make good devices !! The process is complicated because the amorphous silicon needs to have a low enough density of impurities and defects in order to make devices. The amorphous silicon solar panels actually start off as 8-10% efficiency and drop down to 5% because of optical generation of defects in the amorphous silicon material. In research, non-degraded 10% amorphous silicon cells have been demonstrated but I don't think that they have reached production yet. It is actually quite difficult to make solar cells that are 10% efficient - especially over large areas. Imagine making square feet of solar panels that are low in defects and impurities - it's not easy !! The only company electrodepositing solar panels is BP Solar in England. I'm not sure of the status of their production. I hope that this information is useful to help you understand a little more about PV processing. Please feel free to disseminate this information to whomever you wish - but I would like you to mention me as the source in case others wish to contact me for more information (especially on my research work). Hope we see some Sun again soon - it's quite dreary outside today. Pali At 04:08 PM 3/28/96 -0500, you wrote: Hi Pali, > I have a couple of corrections to make to your statements about my >PV research and Ovshinsky's panels. Thank you. >I am working on electroplated solar cells on transparent substrates. Sorry, I guess I missed that when you explained to me what you were doing. >The electroplating process is a low temperature process (60 C) and so could >potentially be used on plastic substrates with a transparent conducting >oxide (such as tin oxide or indium tin oxide) as the transparent contact. >This would allow potentially low cost devices to be manufactured since the >process and materials costs could both be very low. The transparent substrate >would also allow heat to pass through so that the use of these devices in >a hybrid electrical/thermal system would be a great idea. It also makes >a lot of sense to use these types of PV cells in a hybrid solar collector >with a heat exchanger because that would allow the cells to operate a >little more efficiently !! I do recall your mentioning that a little company in Maryland was actually producing these... Ovshinsky PVs make 50 w/m^2 in peak sun at 20 C, and 45 w at 60 C. I wonder about the efficiency of your plated cells might be at 40-60 C, ie water heating temps... Or will that damage them? In Ovshinsky's case, the PVs would absorb 90% of the sun as heat, which might heat air or water directly, but in your case, I guess that 90% would shine on through the cell to strike a dark surface, perhaps behind another transparent layer with an air gap on each side, so your cells would run cooler in this application, I guess. >I will keep you informed as to how the research is going but don't hold >your breath - after all it is research and may take a few years to get to >a point before it is commercially viable. Sure... Altho you seem to be more interested in coming up with a practical product than many other scientists and professors... I'd be happy to post some edited version of this email of yours to our AE list, about 500 amateurs worldwide, and a few professionals, with your permission, anon if you like. Most of the info they get about PVs comes from fairly slanted advertising and press releases. > In terms of Ovshinsky's cells, these are amorphous silicon alloys >that are made by a plasma assisted chemical vapor deposition process. Those >big chambers that you have seen that look like a newpaper press are in fact >evacuated chambers in which gases of SiH4, GeH4, CH4, PH3 (phosphine), >AsH3(arsine) and B2H6 (diborane) flow. An RF plasma is used to break down >these gases and the Silicon, germanium, carbon, hydrogen and dopant >components are driven to the stainless steel substrate by the capacitive DC >self-bias between anode and cathode capacitor plates. He didn't mention that it was that complex, and I'd gotten the impression somehow that the substrate was ordinary cheap mild steel... >The multiple chambers are used to deposit individual layers of a device >that may have as many as 10-12 layers !! This is not an inherently cheap >process in small scale production (<10MW/yr.) and so the selling price of >$4.50 a peak Watt is about the production price of these cells. I wonder why this has to be so complicated, if they are only aiming at 5% efficiency? These things are basically just large area PN junctions with carefully non-shading top electrode, no? Not CMOS microprocessors... >(USSC is very secretive about its books and so the exact production price >is generally not known Jim Young of USSC gave me that "retail price." I assumed these things cost them a lot less to make, at 5% efficiency, and that USSC was charging what the market will bear, and making lots of money competing against crystalline cells, where mounting area is not a big factor. John Page also mentioned that Ovshinsky seemed to leave out some details in his talk. >but Solarex's >Thin Film Division makes a similar product and they are selling the cells >for more than it costs to make them). As far as I am aware only the Solarex >polycrystalline silicon cell division is making money as a solar cell >manufacturer and they are selling at about $3.50 a peak Watt for large >orders. There is a joint venture between Enron Corp. and Amoco (Solarex's >parent company) to make a 10 MW/yr. thin film PV manufacturing facility in >Virginia. Until now the amorphous silicon community has said that the cost >of amorphous silicon PV will drop dramatically (down to less than $1/Wp) if >they could take advantage of economies of scale and produce at least 10MWp/yr. Seems like they have been saying that for 30 years :-) I read a paper by Ovshinsky in Physics Review in about 1966... >Enron has called their bluff and so let's see what happens !! Keep posted. OK... >In the meantime Solarex's polycrystalline silicon cell division is >ramping up to increase their production capacity three-fold and Siemens >Solar (what used to be ARCO Solar) is also increasing production. So there >is a growing market for PV but primarily for remote applications in >developing countries. The figure I heard is that 80% of our PV production goes overseas, a lot of that to the 2 vbillion people in the world who have no elecrcity at all. Just mud and tin huts with dry cells and candles, I guess. > I agree that we should start any solar home design with trying to >meet the heating load of a house through good passive solar design (after >insulating the house as well as possible) and then look to fund PV to supply >the necessary but small electric load (if economically justified). Good. Would you still like a solar shed in your yard? > I'm still looking for students for solar homes projects - I'll let >you know if I get any bites. Thanks. I'm going to try to show up for the second day of the current senior project talks. Dr. K sent me a schedule. Meanwhile, I'm helping design a 100% solar house in Lebanon, PA, and it looks like I might be helping design another in Seattle, where they have no sun :-), and my episcopal friend Father Jim Evans from Phoenixville, who has built about 500 low income houses in this area over the last 10 years or so, some with his own hands, says he'd like me to help figure out how to make cheaper electricity for people in St Kitts, which has lots of wind, 16 mph average in some places, and some dormant volcanos with geothermal potential. He's building a conference center surrounded by 50 new vacation homes, which may want solar water heaters in the roofs, combined with PVs? Nick Article 270 of pa.environment: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Exploring solar wetland structures Date: 7 Apr 1996 08:54:30 -0400 Organization: Villanova University Lines: 477 Message-ID: <4k8du6$6jq@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <4jjcc1$q0c@vu-vlsi.ee.vill.edu> <4jrhk4$7nn@vu-vlsi.ee.vill.edu> <4k5qqh$o8@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Summary: (Chickens for Christ? :-) Xref: news.ee.vill.edu sci.energy:50388 alt.energy.renewable:108 bit.listserv.geodesic:5152 alt.architecture.alternative:127 pa.environment:270 sci.environment:97084 alt.home.repair:846 sci.engr.heat-vent-ac:6025 alt.solar.thermal:27 Were Jesus alive on Easter Sunday, 5 years ago, would He have condoned the Gulf War, or might He have said that blood, like oil, should not be wasted? Would he have worried with Donald Hodel, a former DOE Secretary, that we are 'sleepwalking into a disaster'? Hodel predicts a major oil crisis within a few years, while Irwin Stelzer of the American Enterprise Institute, says that the next oil shock "will make those of the 1970's seem trivial by comparison," and Shell Oil's planners believe that "renewables may make up a third of the supply of new electricity within three decades even if electricity from fossil fuels continues to decline in cost. (From "Mideast Oil Forever?" by Romm and Curtis, Atlantic Monthly, April 1996, Boston, (617) 536-9500). These are moot questions, if "faith without works is dead." Israelis hardly need solar heat, but they use it in the Rankine cycle power plant in the Dead Sea, making 5 Megawatts of electricity with 170 F brine drawn from the bottoms of 62 acres of solar ponds, unlike our largest 0.83 acre solar pond in El Paso, Texas, which makes heat for a food canning plant. When last we met, gentile readers :-) I miscalculated the average winter water temperature in a greenhouse heating system: >With the skating rink, we might have Ein = 1000 (256) 1.5 = 384K/day, so >the sunspace air temperature would be Ta = 43 + 246K/1536 = 160 F during Oops, I should have written Ta = 43 + 246K/1536 = 43 + 160 = 203 F... This would be a hot sauna, almost boiling. We could fix this "problem" by filling the sunspace with bricks, as the PSIC priesthood recommend, or we could just let it be, as a heretical high-performance, inexpensive sunspace. >the day, and the water temperature would be Tw = (160 - 60)/0.714 = 140 F. This should have been Tw = (203 - 84)/0.714 = 167 F. Close to that Dead Sea solar pond power plant temperature. Hmmm... Here is a better diagram of the greenhouse site, as improved: ..................... . . . . . chicken coop . 12' N . . | 16' | . . . . . . . . ................. --- ..................... <- 30' -> . . . 20' . . . . . . . . . . . . . . . . . . | (Does this picture suggest . . . enclosing the 30 x 66' space?) W . . . 32' E .30' . . . . . . . | . . . . . . . . . . .................. . . . straw wall . . . . . . . . . . . . . .......................glass...... --- 4' . solar wall 203 F . ..................................................... . | 32' | . . . . reflecting pool . 16'. made from a single roll of 20' wide . . EPDM rubber roofing material . . . . <-- 50' --> . ..................................................... . S . (with an air-inflated roof, . like a tennis court?) . ..................... 36 F . . --- . . ..................... ..... ~4' . . . . . --- . chicken coop . . . c c . . . 8' . solar wall . T c c . ~5' . . . B i p p i B . .. . B w p p w B . .............................................................................. My favorite structure on this property is the 12' x 20' dilapdated chicken coop, with the long dimension running EW, the right way to orient a solar structure. It has a roof that slopes up 2' from the north to the south along the 12' dimension. Part of the building was probably used for plant propagation, since there is a bench on the south side behind some windows, with an old green 4" x 6" box on the wall marked "Mist-a-Matic," made by E C Geiger of North Wales, PA. How can we solar heat the chicken coop? Perhaps surround it with strawbales? A strawbale and mortar wall all around it, and strawbales on the roof, with a layer of EPDM rubber over the straw? The chicken coop is interesting inside, mostly wood, but the outside is covered with ugly warped green asphalt shingles, many about to fall off. We might want to hire a team of Professional Structural Engineers to certify beyond all reasonable doubt with elaborate studies and tests, ie their own high-priced chicken manure, that this chicken coop would not collapse in a tragic heap of straw and feathers, but assuming that were not a problem... ...we'd have a box with R-40ish walls, about 12' deep by 20' wide (EW) by 8' tall, with about 64 ft^2 of R2 (?) doors and windows. The building envelope would have a total area of about 2(12x20+12x8+20x8)=864 ft^2, with a strawbale thermal conductance of 800ft^2/R40 = 20 and a window, etc thermal conductance of 64ft^2/R2 = 32, ie a total thermal conductance of 52 Btu/hr per degree F. Note that the windows and doors are less than a tenth of the wall area, but they account for more than half of the thermal loss of the structure. To keep the chicken coop at 76 F inside for 24 hours a day, on an average 36 F December day in Philadelphia, we would need 24 hr (76F-36F) 52 = 50K Btu. About a half-gallon of oil, or 75 ft^2 of solar air heater area. Suppose we add a low-thermal-mass lean-to sunspace to the south wall, eg 20' x 9' of south-facing polycarbonate glazing, with the bottom edge buried in the ground 4' in front of the chicken coop, with a 4' reflective/shading overhang at the top of the sunspace, at a steeper slope than the roof. That might look something like this from the east: . . straw g Du . . . s . . s g t . . t r . ~8' . r a . . a g w . . w Dl . .............g................................................. g | 12' | The single layer polycarbonate might be Dynaglas corrugated sheets, about 4' wide x 12' long, distributed by SPS at (408) 997-6100, and sold by greenhouse suppliers like E C Geiger at (800) 4 GEIGER, or geigerintl@hortnet.com, with web site http://www.hortnet.com, or D & L Growers at (800) 732-3509, or Stuppy Greenhouse Manufacturing, Inc., at (800) 877-5025. Dynaglas and similar products made by Replex Plastics and GE cost just over a dollar per square foot, require support on 4' centers, and have a 10 year guarantee against loss of light transmission and an expected mechanical lifetime of over 25 years. GE's application note on page I-18 of the Stuppy catalog says "For added strength and rodent control, sheets at ground level may be buried 4" to 6"." Some landscaping timbers staked to the ground with 4' of #4 rebar might be a suitable foundation, and the glazing wall studs might be 2x4s on 4' centers north of a mid-height 2x4 purlin. How much thermal mass would would we need to keep this building at 76 F inside, 24 hours a day, during a very cloudy December, eg for 20 days in a row, at 36 F outside, with no sun? About 20 x 50K = 1 million Btu. Suppose our thermal mass were water inside a solar closet, and after a long string of average December, with some sun, the water had a temperature of 130 F. Then a 55 gallon drum full of water would store about 55 gal x 8 lb/gal x (130F-80F) = 25,000 Btu of usable heat. How many drums do we need in this solar closet? 1 million/25K = 40 drums. How much space would they require? Each drum is just under 3' high x 2' in diameter, so we might line up 6 of them in a row from north to south along the east side of the coop. If the drums were stacked two-high, each 2' x 12' slice of the building could store about 12 drums, and there would be an insulated wall running NS between the solar closet and the plant propagation area. The drums would fill up the 8' x 12' area where the chickens lived. This is 40% of the floor space in this building, but that fraction might decrease to less than 2% of the floor space of a new 2,000 ft^2 building with, say, 5 days, vs 20 days of thermal storage. Large buildings with small surface to volume ratios are easy to solar heat. What will the water temperature in the solar closet be, after a string of average December days, eg days with 6 hours of sun at an average daytime outdoor temperature of 43 F, and an average outdoor 24 hour temperature of 36 F, and an average 1000 Btu/ft^2 of sun that falls on the sunspace? This isn't hard to estimate, so why spoil the fun? As Tom Smith said in 1980, "It's a snap to save energy in this country. As soon as more people become involved in the basic math of heat transfer and get a gut-level, as well as intellectual, grasp on how a house works, solution after solution will appear." Here are some hints: The solar closet might have its own air heater, with an inner glazing as a part of the house wall between the sunspace glazing and the inside of the house. In this case, that inner glazing might be 8' tall x 8' wide, so that approximately 64K Btu/day enter the solar closet. One way to calculate how warm the water would be after a long string of average days is to figure out how much net energy the sunspace collects on an average day, and how much is needed to keep the coop warm, and how much is leftover. The leftover energy can go into heating the water inside the solar closet, which can be very well-sealed with insulation all round during the night, and never used for house heating on an average day, if the house contains sufficient thermal mass of its own... At this point we might have a solar heated greenhouse with an 8' solar wall running 16' west to help keep it warm, and a solar heated chicken coop in the other corner of that 30 x 50' rectangle. They would both lose heat to the outdoor air through two sides of their structures. We might extend the solar wall and build more straw walls and put a lightweight air-supported roof over the 30 x 58' rectangle between the SW corner of the chicken coop and the ridge of the greenhouse, like this: straw ..................... .s . .t . straw N .r chicken coop . 12' | 16' | Aa A..........................................A .w . straw wall ................. --- A...................A........................... A . . . 20' | <- 30' -> . . . . s . . . . . t . . . . . r . 38' x 66' membrane cover . . . . a . . . . . w . | . . . . . W . . . 32' E . w .26' . . . . a . . . . . l . | . . . . l . . . . . . . . . . A........................................... . . . straw wall . . . A....................................................glAss...... --- . 4' solar wall . A..............................................................A.......... . . reflecting pool . 16' made from a single roll of 20' wide . EPDM rubber roofing material . . <-- 100' --> . <......................................................................... . S . air-inflated cover? . ....A..................................................A --- . . . ..... ~4' . . . . --- . chicken coop . . c c . . . 9' tall solar wall . T c c . ~5' . . B i p p i B . . B w p p w B . .............................................................................. The cover might attach along lines with corners marked A above. It could be rectangular in shape, as seen from above, and curved as seen from the east or south. It might be made in a north and a south section, and the main part, the north section, perhaps 2/3 of the cover, might be opaque and roughly parabolic in the NS profile and reflective underneath to help keep heat inside the structure, and to bounce and concentrate winter sun down into an indoor pond, as in Howard Reichmuth, PE's very successful full-size Ecotope concentrating greenhouse built 20 years ago, in cloudy Seattle, which has half the winter sun of Philadelphia and a fourth of New Mexico's. We also want to avoid summer overheating with this opaque north section, while the steep-sloping south section would be more transparent to let in light, and let in the heat of the winter sun. The cover might rise 18' above the wall at the highest point, with an average south-facing height of 9' above the straw wall, to admit a daily average total winter sun heat of Ein = 18' x 66' x 1000 Btu/ft^2/day x 1.5 = 1.8 million Btu, ie 522 kWh, with a peak sun power input of about 157 kW or 210 horsepower. The main heat loss from this enclosure would be through the cover, with somewhat less heat lost through the greenhouse. Ignoring the greenhouse and walls for the moment, what would the average R-value for the 1500 ft^2 cover have to be to keep the inside 66 F for 24 hours a day in December? Ein = 1.8 million Btu = 24 (66-36) 1500 ft^2/Rcover ==> Rcover = 1.7. We might use an R1 clear plastic for the south part, and something like the Ludvig Svensson aluminized environmental screen (R3.2?) for the north half, described on page E-5 of the current Stuppy catalog this way: "The permeable closed-structure construction allows the transfer of humidity to prevent condensation, while providing a light-controlled environment for your crops." This material costs 32 cents/ft^2, with additional small fabrication charges for sewing custom sized pieces out of standard 10-14' widths, adding tapes and grommets and hooks, etc, as specified. A less expensive possibility for the north section is Klerk's K-white Tri-Layer Greenhouse Film, a "strong EVA copolymer resin for excellent durability," treated with UV inhibitors and filled with titanium dioxide white pigment to give a 45% light transmission. This material costs 7.8 cents/ft^2, and it has a 3 year guarantee. It might last longer with no southern exposure. It comes in rolls up to 50' wide, 6 mils thick. I would guess it is recyclable. In either case, it seems prudent to have a few flagpoles and wires underneath in case the fabric rips or pressure is lost, and some ropes attached to some points overhead to control wind flapping. A more permanent solution would be a Monolithic Dome cap (800) 608-0001, costing about $20/ft^2, put up as a turnkey shell, with 2" of reinforced concrete under 3" of polyurethane foam, all sprayed on from the inside under the inflated airform. The thermal mass and conductivity of the concrete inside the foam insulation would make this an excellent solar structure. One might reduce the cost by leaving out the concrete or using thin ferrocement instead, on a geodesic framework faced with wire mesh. How large a thermal mass would we need to keep this enclosure at 66 F for 5 days without sun when the outdoor air temperature is 36 F? Suppose the thermal pond has a temperature of 100 F, with an 16' x 40' area, and the cover has an average R-value of 2. Then the enclosure will lose about 24 (66-36) 1500/2 = 540K Btu/day, or about 2.7 million Btu over 5 days. If the pond can keep the enclosure at 66 F until the water reaches 70 F, and each cubic foot of pond water stores 62 Btu when heated 1 degree F, and the pond has a depth of D feet, 62 x 16 x 40 x D (100F-70F) = 2.7 million Btu, so D = 2.3'. It would be interesting to observe the organisms that evolve over time in this indoor wetland, vs the one outdoors... We would need a smaller or cooler thermal storage pond if the roof were better insulated. One way to accomplish this is to use a tensile structure with the profile shown below, from the east: . . . . . . . . . .16'. ........... . . . . . . . chicken . pond . . . coop . ......................................................................... This might look like a 16' x 66' transparent wall from the south, perhaps with a sag in the middle. The main roof, the ie north slope, might be made with 4' wide chicken wire strips running north and south, joined with galvanized metal strips that sandwich the chicken wire. The wire web might be covered with 1/2" of cement, and it might have a layer of fluffy plant material on top, eg composted water hyacinths, with a synthetic waterproof breathable fabric layer tied on over that. The pole supports at the SE and SW corners might be telephone poles wrapped with ferrocement, ie a layer of chicken wire with some cement on top to strengthen and weatherproof them. This taller south wall would benefit from a wider frozen reflecting pond in the NS direction, since winter sun only reaches a height of 26 degrees above the horizon in this area, and tan(26) = 0.43, ie the sun from a mirror 37' wide in the NS direction would just strike the top of the 16' solar wall at noon on 12/21. So we might make the reflecting pond 38' wide using 2 strips of EPDM rubber roofing material, perhaps with an EW standing seam in the middle. We might use that pond for sewage treatment... US EPA Design Manual number 74, "Subsurface Flow Constructed Wetlands for Wastewater Treatment," written by Sherwood C. Reed, PE, is available for about $12 from the Small Flows Clearinghouse at West Virginia University at POB 6064, Morgantown, WV, 26506-6064, (304) 293-4191 or (800) 624-8301. Here's a quote: The proponents of subsurface inlet manifolds claim they are necessary to avoid the buildup of algal slimes on the rock surfaces and resulting clogging adjacent to a surface manifold. The disadvanatages of a subsurface manifold are the inability for future adjustment and the limited access for maintenance. In one case, a buried manifold became clogged with turtles which entered the piping system from the preliminary treatment lagoon and had to be removed. There is a lot of nice, simple math in this manual, which explains how to build a natural wastewater treatment system for a home or community. The manual doesn't say where the frogs came from :-) Reed's book _Natural Systems for Waste Management and Treatment_ describes how to build ponds, lagoons and artificial wetlands, and predict their performance. McGraw Hill, 1995, second edition, ISBN 0-07-060982-9, 434 pages, about $55. The back cover says: Here is your chance to learn about biologically-based systems for handling waste that are fast becoming the technology of choice in communities and municipalities across the United States... the new edition of this classic reference will introduce you to low-cost, low-energy methods of processing waste and wastewater naturally... Here are some quotes: Serious interest in natural methods for waste treatment reemerged in the US following the passage of the Clean Water Act of 1972... The major initial response was to assume that the "zero-discharge" mandate of the law could be obtained via a combination of mechanical treatment units capable of Advanced Wastewater Treatment (AWT). In theory, any specified level of water quality can be achieved via a combination of mechanical operations, However the energy requirements and high cost of this approach soon became apparent, and a search for alternatives was commenced... ...as more and more systems were built... it was noticed that these natural systems... could usually be constructed and operated for less cost and with less energy... ...there were about 400 municipal land treatment systems using wastewater in the US in the early 70's. That number had grown to at least 1400 by the mid 1980's and is projected to pass 2000 by the year 2000. Stabilization ponds have been employed for treatment of wastewater for over 3000 years... The most common type is the facultative pond. Other terms commonly applied are oxidation pond, sewage lagoon, and photosynthetic pond. Anaerobic fermentation occurs in the lower layer and aerobic stabilization occurs in the upper layer... a continuous ice layer on a facultative pond will lower performance [but a partial ice layer on a cold day might make a very nice solar reflector--NP]... The occasional high concentration of suspended solids (SS) in the effluent... is the major disadvantage of pond systems. The solids are composed primarily of algae, not wastewater solids. Aquatic treatment is defined as the use of aquatic plants or animals as a component in a wastewater treatment system. In many parts of the world, wastewater is used for the production of fish... The floating aquatic plants with the greatest potential for wastewater treatment include water hyacinths, duckweeds, pennywort and water ferns... Hyacinths are one of the most productive photosynthetic plants in the world. It has been estimated that 10 plants could produce 600,000 more during an 8 month growing season and completely cover 0.4 ha (1 acre) of a natural freshwater surface. The rate can be even higher in wastewater ponds... The dense canopy of leaves shades the surface and prevents algal growth... The plant can survive and grow in anaerobic waters, since oxygen is transmitted from the leaves to the root mass. The attached biological growth on the root mass is similar to... rotating biological contactor (RBC) slimes. Bacteria, fungi, predators, filter feeders and detritovores have been reported in large numbers on and among the plant roots... An effective mosquito control method is to stock each basin with Gambusia or other small surface feeding fish that prey on the mosquito larvae... [Other species include goldfish, frogs, grass shrimp, blue tilapia and Japanese koi. The hyacinths are sometimes harvested and processed in a biogas digestor or used for animal feed...] ...duckweeds are the smallest and simplest of the flowering plants and have one of the fastest reproduction rates... Lemna sp. grown in wastewater effluent (at 27 C) doubles in frond numbers, and therefore area covered, every 4 days. [Not surprisingly, ducks like to eat duckweed, a lot--NP] ...duckweed can grow at least twice as fast as other vascular plants. The plant is essentially all metabolically active cells, with very little structural fiber... Duckweeds are more cold-tolerant than hyacinths, and are found throughout the world. In 1992 there were at least 15 operational wastewater treatment facilities designed specifically as duckweed systems... mosquito larvae will not be able to penetrate a fully developed duckweed mat, and are therefore not a problem... Duckweed, like hyacinth, contains about 95% water... duckweed contains at least twice as much protein, fat, nitrogen and phosphorous as hyacinth. Several nutritional studies have confirmed the value of duckweed as a food source for a variety of birds and amimals [footnote]... The harvested plants may be used directly in the wet state as poultry or animal feed. Composting... is also feasible. Pond systems in colder climates can be designed for the seasonal use of duckweed to significantly improve performance durign the normal algal growth season... Duckweed plants form a "winter bud" at the onset of cold weather. This "winter bud" has a high specific gravity and sinks to the bottom of the pond, where it remains all winter [under the reflective ice layer--NP.] In the following spring they float and repopulate the pond... The aquatic animals that have been considered for use in wastewater treatment include Daphnia, brine shrimp, and a wide variety of fish, clams, oysters and lobsters... Except for the predatory fish and the lobsters, the primary function of the other species is the removal of the suspended solids or algae. Assuming that the animals are routinely harvested, this will in turn also improve nutrient removal... Fish activity is highly dependent on temperature, and most of the species... with the exception of catfish... require relatively warm water... The final lightly loaded cells in wastewater pond systems can be used for fish culture if a market for the harvested fish exists. At present, federal and state health regulations prevent the sale of such fish for direct human consumption, even though microbiological studies have not detected any contamination... major markets for this harvested material would be bait fish, pet food or fertilizer. Nick Article 6064 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal,misc.consumers.frugal-living Subject: A solar cabin Date: 10 Apr 1996 08:22:02 -0400 Organization: Villanova University Lines: 172 Message-ID: <4kg95a$faa@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <4j6osk$a30@vu-vlsi.ee.vill.edu> <4jjcc1$q0c@vu-vlsi.ee.vill.edu> <4jrhk4$7nn@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50491 alt.energy.renewable:146 bit.listserv.geodesic:5177 alt.architecture.alternative:154 pa.environment:277 sci.environment:97388 alt.home.repair:1054 sci.engr.heat-vent-ac:6064 alt.solar.thermal:38 misc.consumers.frugal-living:16483 A friend writes: >I am interested in your solar closet for home heating and water heating. Good... >I have a vacation cabin in East Tennessee that I will eventually retire to. Well, I see from the NREL _Solar Radiation Data Manual for Buildings_ (http://rredc.nrel.gov) that Knoxville gets 940 Btu/ft^2/day of sun on a south wall on an average day in December, the average 24 hour outdoor temperature is 40 F, and the average daytime temp is 50 F. Sounds like a pretty good climate for solar heating... Microclimate could matter a lot near the Smokies. I camped outdoors on Mt LaConte once, with a bear huffing and puffing around my sleeping bag at 3 AM :-) Is there a lot of fog around your cabin? Are there lots of bears? What's the south wall look like? Is it shaded much by trees, etc.? Do you have a south porch you could enclose, or could you add a lean-to sunspace? With a reflecting pond in front of the sunspace? >It is 970 square feet and is presently heated by two 110VAC in the wall >strip heaters and a wood stove. Can you guess how much fuel it might use per year if it were occupied all the time? A cord of wood is something like 100 gallons of oil or 3000 kWh of electrical energy or 100 ft^2 of south glazing over a winter. How well is the cabin insulated? Can you make it fairly airtight? A square cabin that size might have about 1000 ft^2 of ceiling and 1000 ft^2 of walls. With R11 insulation (fiberglass in a 2x4 wall), the thermal conductance might be about 2000 ft^2/R11 = 180 Btu/hr/degree F, so on an average 40 F day in December it would need about 24 hours (70F - 40 F) 180 = 130 K Btu/day to keep it at 70 F inside. Water heating for 3 showers a day, each lasting 10 minutes at 3 gpm, would need another 3 x 10 min x 3 gpm x 8 lb/gal x (110F - 60F) = 36K Btu/day, so the house total might be 170K Btu/day, not counting internal heat gain from electrical consumption. Where you are, a square foot of sunspace with no reflecting pond might gain 865 Btu/day and lose 6 hours (80F - 50F) 1 ft^2/R1 = 180 Btu/day, for a net gain of 700 Btu/ft^2/day, so to provide a total of 170K Btu/day, you might need 170K/700 = 240 ft^2 of sunspace, ie a sunspace running the length of the south wall, 30' long x 8' tall. It might be some very clear single-layer polycarbonate glazing that comes in rolls 4' wide, attached to 8' 2x4s or 12' 2 x 6s leaning against the cabin wall. Or a steep south polycarbonate roof. Or... some very clear long lasting mylar film (eventually), starting out now with polyethylene film, which costs about 4 cents/ft^2, and has a 3 year guarantee and comes in very wide rolls and can be replaced like a large bedsheet and recycled every three years, less often perhaps if the sunspace is covered with greenhouse shadecloth in the summer. This might be a curved sunspace, with the film stretched over galvanized pipes. It could be very large and inexpensive, less than $1 per square foot. How does that sound? Behind or inside that, you might store heat for 5 days without sun in a small insulated room, ie a solar closet storing 5 days x 170K = 850K Btu of heat. A gallon of water at 130 F stores useful house heat until the water reaches 80 F or so, ie (130-80) 8 lb/gal = 400 Btu of house heat. So you might have 850K/400 = 2000 gallons of water in your solar closet, in the form of 40 55 gallon plastic drums stacked up 2 high and 2 deep in a row 20' long, ie a solar closet that is roughly 4' deep x 20' long x 8' tall. Or you might use 400 5 gallon plastic pails with lids, sitting on shelves made from cement blocks and boards. If it turns out you don't need that much thermal mass, you could put something else on the shelves. For water heating, it might be good to have two sections of closet at different temperatures, with the hotter section better-insulated and used as a last resort for house heating, and the cooler one containing the section of fin-tube pipe loop with the cold water input. You might have an electric water heater in the closet with a small circulating pump, or a small fan powered by a PV panel in the sunspace, drawing air down from the ceiling and pushing it out the bottom of a 4' wide, 4" thick duct built onto an inside wall, past 8' of fin-tube along the duct bottom, in a U-shape. A better place for an electric water heater (whose heating element almost never turns on) might be on the floor above, so it could use a natural warm water convection loop. I wonder if you have any sort of attic above the south wall, or you would like to make a small sunspace up there... The solar closet glazing inside the sunspace glazing might have an area of 8' x 20', a little more than half of the sunspace glazing. An ASCII picture from above: <-- old | new --> 30' 4' ........................................... . . . . . . . . . . . refl . . .SC . surf? . . . . . . . . .20' . . . . . . . . .30' South --> . existing cabin . . SS . . . . . . . ..... . reflective . . . surface? . . . . . . . . . 12' . ........................................... . . . . <-- old | new --> Or perhaps like this? | 8' | 8' | 8-16'? straw wall? -- ................. . . . . s . s. . t . t. refl . . | r . SC r. surf? . 16' a . a. . | w .......w. . . ? . ?. s . . sauna . u . reflective ............................... n . surface? . South --> . 30' . s . . . p . . . a . . 30' 16'. c . . . . e . . . . . . . . existing cabin ......... . . . . . . 8' . . These pictures make more . . sense when viewed in a . . non-proportional font . . like courier... . . ............................... If your existing cabin has little thermal mass, you might want to add some, because it would be nice (but not necessary) if the cabin could get through an average December night with no help from the solar closet. Is 55F at night OK? Starting at 75 F at dusk, your cabin might need 18/24 x 130K = 100K Btu to keep warm until dawn, ie 100K Btu = (75-65) M, where M is the number of pounds of water in the house, so here, M = 5000. That's a lot of water... 10 more 55 gallon drums sprinkled around the house, or another 110 5 gallon pails here and there :-) Perhaps the solar closet should provide some overnight heat in this case, or the cabin should have more insulation. At any rate, you see how this works. The sunspace and solar closet and cabin thermal mass could be smaller if the cabin were better insulated. Half the size with R22 insulation, a third as big with R40, I guess. Surround the cabin with strawbale/mortar walls? >If you are interested in designing a solar >closet for my cabin please let me know what you would charge. Hey, I just did it, free :-) Let me know how it works! Would you like me to help you build it in May, August or September? Send me a sketch if you like, or let me know if you would like to talk about modifications or if you have questions. I could check out a specific design with a simulation using 30 years of Knoxville hourly weather data, if a certain physics student or professor would get that data off a CD-ROM. We would really like to see this technique tried out on a larger scale than our 2x4x8' outdoor test box... Nick Nicholson L. Pine System design and consulting Pine Associates, Ltd. (610) 489-0545 821 Collegeville Road Fax: (610) 489-7057 Collegeville, PA 19426 Email: nick@ece.vill.edu Microprocessor hardware, memory, ASIC, and computer design. Telecommunication system design. Computer simulation and modeling. High performance, low cost, residential solar heating and cogeneration system design. BSEE, MSEE. Senior Member, IEEE. Registered US Patent Agent. Fluent in French. Article 280 of pa.environment: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: A bubble wall? Date: 12 Apr 1996 04:17:08 -0400 Organization: Villanova University Lines: 77 Message-ID: <4kl3i4$rv2@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <4jjcc1$q0c@vu-vlsi.ee.vill.edu> <4jrhk4$7nn@vu-vlsi.ee.vill.edu> <4k5qqh$o8@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Summary: a simple math problem, and a good science fair project... Xref: news.ee.vill.edu sci.energy:50559 alt.energy.renewable:169 bit.listserv.geodesic:5202 alt.architecture.alternative:179 pa.environment:280 sci.environment:97561 alt.home.repair:1160 sci.engr.heat-vent-ac:6094 alt.solar.thermal:41 Certain standard works like the PSIC Guidelines for Passive Solar House Design teach inefficient passive solar house design. But to me the principles of efficient passive solar house design aren't hard to learn. UNlearning is often the hard part. A couple of days ago, I explained most of them in 2 hours to a smart 13 year old, working thru 7 pages of simple equations and examples together. I had asked her if she had studied algebra in school yet (she was reading a physics text as I walked up to her at a science fair), and she said "no, but I know all that" :-) And she did. There was also a 12 year old doing bubble experiments. She discovered that if she doped her standard bubble mix (1/2 cup green Dawn, 3 Tbs glycerin, and 2 quarts of water) by adding 1/4 tsp of lemon juice, the bubbles lasted 111 seconds at 80 F and 506 sec at 45 F, vs 309 sec and 185 sec for the standard solution. 1/4 tsp of maple syrup changed this to 431 and 345 sec. She also tried adding jello, perfume, and another dozen substances... Her parting thought was quite serious: "Dust is the enemy of bubbles." So, led by this little child, let's all buy some glycerin, and try to invent a bubble wall, eg two pieces of single-layer polycarbonate plastic with butyl tape over a plastic 1x3" frame that can be filled between with bubbles at night that emerge from a PVC pipe with a few holes immersed in a soapy solution at the bottom, connected to a small aquarium air pump with a timer? This could be very useful in a passive solar house, like Beadwall. Simple movable insulation. During the day, the sun shines in on some thermal mass, and at night the glazing fills up with bubbles, keeping the heat in. Commercial greenhouses use two huge layers of UV-treated polyethylene film inflated to form an air pillow 4" thick. A tiny 50 watt blower can inflate a 1 acre greenhouse. Would bubblewalls work with poly film pillows? Bubbles tend to last longer in cold humid condtions. A layer of frozen bubbles inside an outside glazing might be very good insulation on a very cold night. Perhaps there is an optimal bubble size for insulation. Too small, and convection losses might be small, but conduction losses and air pump power and water transport thermal losses might be large. Too big, and convection losses go up. Steve Baer tried making solar collectors with bubblewalls years ago, but he let the sun shine though the bubbles during the day, vs leaving the bubblewall cavity empty. He found that the walls of his bubbles were too thin to block IR re-radiation, altho he read later that others had had more success. A bubblewall that is empty during the day could be filled at night with bubbles with thicker or more opaque walls, made with some viscous opaque solution, perhaps containing some green dye. I guess we have to let a little air leak out of the top of the glazing cavity, but we would want to break the bubbles at the top and let the water run back down through the cavity. Ohm's law for heatflow is a good start: the amount of heat Q in Btu/hour that flows through a wall with area A ft^2 and R-value R and temps Ti (F) on one side and To on the other, is Q = (Ti-To)A/R. Here's one bubble wall test setup, a 2' cube divided in half by a bubble wall that might have an R-value of 2 when empty and 12 when full. We might make the cube out of 2" Styrofoam with an R-value of 10. One side could be kept at 32 F with some melting ice at the top, with some foam on top and around the ice tray, and the other side could be kept at 132 F with a thermostat and a light bulb, with a piece of aluminum foil to shade the bubblewall from the bulb. How much ice water might we collect in an hour with the bubblewall empty and full of bubbles? What might we get for readings in each case if we hook up the light bulb to a kWh meter? It's nice to have two ways to check the heatflow through the bubble wall. ......................... 70 F room . ice .. . . ......................... . . .. . . . To .. Ti . R10 . 2' 2' . 32 F .. 132 F . . . .. light . . . .. bulb . . ......................... 2' 1' 1' ^ |___ bubble wall It takes 144 Btu to melt a pound of ice, and there are 3410 Btu in a kWh. Nick Article 287 of pa.environment: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic, alt.architecture.alternative,sci.environment,alt.home.repair, sci.engr.heat-vent-ac,alt.solar.thermal,misc.consumers.frugal-living Subject: A tensile roof? Date: 14 Apr 1996 11:47:11 -0400 Organization: Villanova University paul milligan wrote: > nick@vu-vlsi.ee.vill.edu (Nick Pine) wrote: >~~>A quote from _The Unbelievable Bubble Book_, by John Cassidy... >~~> >~~> Once the World's Leading Fizzicist, Dr. Aristid V. Grosse, for many years >~~> the director of the Research Institute at Temple University, spent his >~~> youth in the study of high-energy particle physics. He worked on the >~~> Manhattan Project... published numerous scientific papers and to all >~~> appearances, pursued a dignified... distinguished, scientific career... > Nick, I think you should take a sabbatical, and do a long involved >study that features Dr. Grosse standing in front of one of your collectors. Hey, I don't work at Villanova... I'm always on sabbatical :-) And I don't do "collectors." OK, OK, OK, that bubble roof might not be very practical for the location near the high school, because some students might find it amusing to pop the roof with their knives in fits of pique. So maybe we should cover it with some burlap and chicken wire and 1/2" of cement, and replace the telephone pole posts and beams underneath with 2 x 4s to hold up the plastic film ceiling over the shadecloth. But that lets out daylighting thru the ceiling.... Hmmm. Let's take another more fundamental look. We don't really want sun shining thru the ceiling in summertime, but we do want light and heat coming in thru the south wall in the winter, and we would still like to try to take advantage of the spirit of section 1610.2 of the 1993 BOCA code, which defines a "continuously heated greenhouse" as a production or retail greenhouse with a constantly maintained interior temperature of 50 F or more during winter months... the greenhouse roof material shall have a thermal resistance (R) less than 2.0... Which we'd interpret to mean that one can turn off the bubble pump and reduce the R-value when it is snowing, thus melting the snow with stored solar heat, which is similar to the practice of local commercial growers, who deflate their poly film greenhouse pillows when it snows to reduce their R-value from 1.2 to 0.8. Section 1610.4 of the code goes on to say "The flat-roof snow load on continuously heated greenhouses shall be calculated using the following formula..." which comes out to be 12 psf where I live... And it further drones on: Retail greenhouse: A greenhouse occupied for growing large numbers of flowers and plants and having general public access for the purposes of viewing and purchasing the various products. Included in this category are greenhouses occupied for educational purposes. So how about looking again at something like that tensile structure with the profile shown below, from the east: . . . . . . ferrocement . . . .16'. poly film bubble ceiling . ........... .-24'. . . . . . . chicken . pond . .<- 38' . ->. coop . ............................................p ~~~~~~~~~ p................ thermal storage pond-> ppppppppppp This might look like a 16' x 66' transparent wall from the south. The roof might be made with 4' wide chicken wire strips running north and south, wired together and joined with pressure-treated 2x4s that sandwich the chicken wire, like this: ......... . NS 2x4. ......... -- 1/2" cement -- ccccccccc cccccccccc chicken wire bbbbbbbbb bbbbbbbbbbbb burlap pppppppppppppppppppppppp poly film or EPDM ......... . NS 2x4. ......... .............................................................. 2 x 4 on edge, running EW .............................................................. . spacer. . . . . . . ......... steel cable Let's see. How big does the steel cable have to be? If the roof has a nice slump in the middle, and the distance from top to cable is, say, 6', we need roughly 20 psf x 32 x 4'/2 = T 4'/32', where T is the cable tension, so T = 10240 pounds. A 10K/50K diameter steel cable every 4'? That's not bad, but there will be a lot of force trying to collapse the north and south walls inwards... This would work better with a few posts in the middle, as before. Then we can reduce the height of the south roof peak to 16', vs 24'. We don't need THAT much solar heat. Recall that we only needed a roof R-value of 1.7 with bubbles in place to make this work. So the roof might look like this in slightly more detail, with different dimensions: 48' r.r.r.r.r.r.r.r.r.r.r.r.r . 32' P ppp P ppp P ppp P P . 16' PpppppppPpppppppPpppppppP PpppppppPppppppp. P P P P P P P 8' .....P.......P.......P.......P... ...P.......P.......P...... PsssssssPsssssss. p is the poly film ceiling here, . . . made in 3 16' x 32' pillows, . . . sloped slightly upwards from . . . north to south, with the bubble PsssssssPsssssss. pipes along the north edge. . . . . . . The poly film would attach along . . . struts s, which would be in PsssssssPsssssss. compression to keep the roof . . . from collapsing. . . . . . . PsssssssPsssssss. There would be a layer of greenhouse shadecloth under the poly film and ropes on 4' centers under that. Struts s might look like this from the south: poly film poly film poly film poly film ww ww aluminum extrusion clamps 30% greenhouse shadecloth ......... . NS 2x4. (on 16' centers) ......... . 2 . <--EW rope . x . EW rope --> ...NS rope... . 4 . ... NS rope... ..... | 4' | There, is that better, Paul? Nick Article 200 of alt.energy.renewable: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.solar.thermal,alt.solar.photovoltaic,alt.architecture.alternative,sci.engr.lighting,bit.listserv.geodesic,sci.engr.heat-vent-ac Subject: Re: Optical concentration of solar energy Date: 15 Apr 1996 07:07:30 -0400 Organization: Villanova University Keywords: solar energy, magnifying lens, concentration. David Jones wrote: >...does anyone know of a source for a magnifying lens to concentrate sunlight >in a straight line, instead of the usual circular form. Edmund Scientific and 3M sell cylindrical lens material, but for a large area, perhaps a linear parabolic reflector would be less expensive, eg this solar greenhouse and water heater that might be built quickly for less than $1,000 in materials to provide winter space heating and domestic hot water and fresh vegetables and flowers for a nearby home or the urban building or swimming pool underneath a flat roof. . --- . . . . <- S. . 12' . y . (32' long) . | z / .| / . / . / x <...........................f............. --- water trench->. . ..... The reflective sheathing might be screwed to 16' kerfed 2 x 4s bent into a 4.5:1 concentrating parabolic shape, with the reflective surface inside the greenhouse. This reflector would have a focus at about f=2.68' (y^2 = 4fx). Howard Reichmuth, PE, designed the Ecotope greenhouse, a similar structure built 20 years ago near Seattle. He's built several steam generators with concentration ratios of 5 or 6. His advice: "Don't stand in the focus. I almost melted a pair of boots." US Patent number 4,129,120, expired 12/12/95, inventor Norman Saunders, PE, describes an efficient concentrating steam generator using a flat transparent boiler with a dark grate inside, just under the water surface. Copies of US patents can be obtained for $3 each from the Superintendent of Patents and Trademarks, Washington, DC 20231. > The idea is to use for domestic heating and/or energy generation a >linear shaped lens to concentrate solar energy on a pipe where the focus >of the lens corresponds to the shape of a pipe ie. a line of focused >sunlight instead of a spot. Duffie and Beckman's _Solar Engineering of Thermal Processes_, 2nd edition, Wiley, 1991, covers the design of these and other _non-focusing_ Winston CPCs, concentrators which accept all light coming from within a certain beamwidth... >I would guess this to be a cheap item to produce if someone is doing it... Richard Komp is doing it at SunWatt, RR 1, Box 7751, Jonesport ME 04606, 207-967-5945. His hybrid 2:1 concentrating solar panels produce 150 Watts of electric power and 1600 Watts of water heating power simultaneously, rounding up half the usual number of photovoltaic suspects. > I live in Texas and have an abundance of sunlight for most of the >year, so would like to experiment with saving energy and money. Hey, c'mon over to the Renewable and Alternative Energy Conference in Abilene from 4/22-23, where I'll be holding forth on solar closets and sunspaces for house and water heating. The cost is only $40 to cover meals. Call Johnnie Lou Avery at 915-235-7332, or send her a check at Texas State Technical College, 300 College Drive, Sweetwater, TX 79556. Or come to Roland Winston's concentrator workshop in Philadelphia on 5/3, from 10:30-3 PM. $50/person by 4/22, ($15 for students, not including lunch.) Send your checks or Faxes with credit card numbers to Kathleen DeLuca at The Franklin Institute, Benjamin Franklin Parkway at 20th Street, Phila, PA 19103-1194, Fax 215-448-1364. Mike Nicklas, AIA, Bill Marshall, NREL, Robert Bickmire, Institute for Energy Conversion and Morton H. Lerner, Engineering Consultant will also be there. Nick Article 292 of pa.environment: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal,misc.consumers.frugal-living,sci.engr.lighting Subject: A lightweight plywood/bubble daylighting roof? (Attn: Hayden Cochran) Date: 15 Apr 1996 09:19:37 -0400 Organization: Villanova University Lines: 120 Message-ID: <4ktid9$514@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <4ko4ig$dpf@vu-vlsi.ee.vill.edu> <4kpf7m$o3o_001@nando.net> <4kr6lv$n9e@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50638 alt.energy.renewable:202 bit.listserv.geodesic:5241 alt.architecture.alternative:209 pa.environment:292 sci.environment:97855 alt.home.repair:1403 sci.engr.heat-vent-ac:6138 alt.solar.thermal:51 misc.consumers.frugal-living:17032 sci.engr.lighting:4652 Nick Pine wrote: >paul milligan wrote: >> nick@vu-vlsi.ee.vill.edu (Nick Pine) wrote: >>~>A quote from _The Unbelievable Bubble Book_, by John Cassidy... >>~> >>~> Once the World's Leading Fizzicist, Dr. Aristid V. Grosse, for many years >>~> the director of the Research Institute at Temple University, spent his >>~> youth in the study of high-energy particle physics... >> Nick, I think you should take a sabbatical, and do a long involved >>study that features Dr. Grosse standing in front of one of your collectors. Well, maybe you don't like all that chicken wire. How about this? Still trying to take advantage of the spirit of section 1610.2 of the 1993 BOCA code, which defines a "continuously heated greenhouse" as a production or retail greenhouse with a constantly maintained interior temperature of 50 F or more during winter months... the greenhouse roof material shall have a thermal resistance (R) less than 2.0... . . . . . . . <-- plywood or OSB under EPDM rubber . . . .20'. poly film bubble ceiling . ........... . . . . . . . . chicken . pond . .<- 38' . ->. coop . ............................................p ~~~~~~~~~ p................ thermal storage pond-> ppppppppppp In more detail, with different dimensions: 48' . r.r.r.r.r.r.r.r.r.r.r.r.r . 32' P ppp P ppp P ppp P P . 20' PpppppppPpppppppPpppppppP <--S PpppppppPppppppp. P P P P P P P 8' .....P.......P.......P.......P... pond.P.......P.......P...... PsssssssPsssssssP p is the poly film ceiling here, . E E E . made in 3 16' x 32' pillows, . W W W . sloped slightly upwards from . B B B . north to south, with the bubble PsssssssPsssssssP pipes along the north edge. . E E E . . W W W . The poly film would attach along . B B B . struts s... PsssssssPsssssssP . E E E . EWB are the East West Beams. . W W W . . B B B . r might be 2x4 rafters. PsssssssPsssssssP The roof might weigh about 15 psf, with 12 lb of snow load and 3 lb of dead load. If the plywood or Oriented Strand Board roof has rafters on 2' centers with 8' spans we might have f=1200 psi, W=8x2x15=240 lb, M=WL/8 =240x8x12/8=2880 in-lb, S=M/f=2.4 in^3, b=1.5" and d=sqr(6S/b)=3.09", so we might use 2x4s as rafters. The EWBs need to hold up 32x48x15x15/5/3=1536 pounds over their 16' span, so if M=1536x16x12/8=36864 in-lb, S=30.72 in^3, b=3" ==> d=7.8", so we might use 2 2x10s for EWBs, or a couple of 2x6s with a downwards king post and a wire. Suppose we use diagonal tension supports like this, as seen from the east: 20'P P \ EWB P K EWB P t K / P \ EWB P \ K t P t K / P P K / P \ K t P 8'P..............K...............P................K/.............P P P P P P P P P P pond.P..............................P...............................P... P P P | 32' | If the kingposts K were 6' long, the diagonals t might have an approximate tension T such that 1536/2 = 6T/8 ==> T=1024 lb. Some twangy wires with good attachments... Each post P would have a load of about 32x48x15/12=1920 lb. Suppose they are Eastern Spruce 4x4s with Cp=750 psi and E=1,200,000 psi. Then L/d=8'x12"/3.5" =27<50, C=1920/(3.5"x3.5")=157 psi ...NS rope... . 4 . ... NS rope... ..... | 4' | The struts would only be holding up poly film pillows filled with 1-2' of bubbles. The pillows would act as solar collectors for some of the 960x1.3x20x66'= 1.65 million Btu or 483 kWh/day average sun that would fall on the south wall of the Perkiomen Valley wetlands structure in December. The peak solar power would be about 160 kW. Some of that heat would be stored in the thermal pond, with a little warm water pumped back up through the collapsed pillows infrequently, to melt the snow off the roof. The roof could be painted white underneath, or covered with 4' wide builder's foil under the rafters, with an operable vent door to the rafter cavity, and another to the outside. Nick Article 50755 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,alt.solar.thermal,alt.solar.photovoltaic,sci.engr.heat-vent-ac Subject: Re: Search for solar-energy-storing Date: 19 Apr 1996 07:25:36 -0400 Organization: Villanova University Lines: 86 Message-ID: <4l7t7g$j2b@vu-vlsi.ee.vill.edu> References: <4knnl1$de4@vu-vlsi.ee.vill.edu> <4krpb7$20l@mtinsc01-mgt.ops.worldnet.att.net> <4ku5hd$a30@tracy.protocom.com> <4l6svo$an@ns1.netone.com> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50755 alt.energy.renewable:262 alt.solar.thermal:66 alt.solar.photovoltaic:53 sci.engr.heat-vent-ac:6206 Jonathan sawyer wrote: >"Duane C. Johnson" wrote: >>Well if common sense is used it is neither cost effective nor efficient. Economies of scale and past subsidies may influence prices more than common sense at the moment. These prices depend on biased advertising and ignorant consumers. Perhaps a lot more $4/watt PVs are being produced than rooftop water heating solar panels now, and maybe that's a good thing. There are more efficient and cheaper ways to heat water, eg some commonsensical $4/ft^2 bare swimming pool tube mat heaters or a $2/ft^2 site built EPDM rubber collector or low-priced Big Fins in a sunspace. >What about PV's running a heat pump? Dumb idea. But smarter than running electric resistance heaters or electric clothes dryers with PVs... >In my house I have a geothermal heatpump heating a 3000 gal water tank which, >in turn, heats the house through slab heating. How about heating the house via a low-thermal-mass plastic-glazed sunspace with a low-power fan or motorized damper in series with two thermostats on a day with some sun? >COP of the heat pump is over 5.0 (50 deg to 90 deg). The COP of John Christoper's 1981 CSI HQ building in New Hampshire is about 50 ("2% fan power, 98% sun power.") Improve that with sealed containers of water in the "rock bed" and motorized dampers vs fans or blowers and it might have a COP of 500:1 at a lower initial cost. A motorized damper costs about $100 and uses 2 watts when moving, 0 watts when not moving (most of the time.) >Powering this with a 15% efficient photovoltaic panels will produce over >75% "heat" efficiency AND the colder it gets the more heat you produce!. Do I have this right? 1 joule of sun falls on the PVs, 0.15 emerge from the PVs, 0.15 go into the battery, 0.15 come out of the battery, 0.15 come out of the inverter, 0.75 come out of the heat pump, 0.75 go into the water tank, and 0.75 come out of the water tank, all with no additional input of energy, at a system cost of $10/delivered watt of house heat? Now suppose we put the PVs in a sunspace and the 85% of the sun's heat that is normally wasted with PVs ends up heating the sunspace air which flows into the house and heats the house. This would raise the system efficiency considerably, no? And you and your friends could sit in the sunspace and play cards and admire your PVs on a winter day with some sun, and revel in how independent and creative you are. Now omit the PVs, and the cost drops dramatically, while the system efficiency remains about the same, on a day with some sun. Now add a little insulated room containing enough sealed containers of water to store heat for a week without sun, with 10' of fin-tube pipe near the ceiling of the little room and a water heater in a warm-water convection loop on the floor above, and the system efficency rises again. Add a little more floorspace to the room, and you have a sauna with free heat and a place to dry clothes. Now omit the 3000 gallon tank, plumbing, slab plumbing, pumps, heat pump, etc, and the cost nosedives again. Before long, you may end up with a simple, practical heating system, unless you are in love with PVs and heat pumps. >Of course you also get free electricity in the summer. "Free," after that little matter of buying the PVs, batteries, inverters, etc, etc.. >I am in the process of installing PV panels for such an operation. I priced >the system cost of PVs and thermal panels and found the PV's to be only >50% higher on a square foot basis. Water heating solar panels are no bargain at $30/ft^2. Polycarbonate plastic "solar siding" or a roof or a sunspace that lasts 20 years at $1/ft^2 is. Polyethylene film that costs 4 cents/ft^2 and lasts 3 years before it needs recycling, while producing $3/ft^2 worth of heat is definitely a bargain. PVs are not a bargain, altho putting them in a sunspace or adding an extra layer of glazing and trickling some water over their faces before the water goes back to your 3000 gallon tank might be a good idea. Stanford Ovshinsky's amorphous PVs produce 50 peak Watt/m^2 at 20 C and 45 pW/m^2 at 60 C, at a cost of about $4/pW. Nick Article 6219 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.engr.heat-vent-ac,alt.energy.renewable Subject: Heating your house with wabbits Date: 20 Apr 1996 05:52:54 -0400 Organization: Villanova University Lines: 29 Message-ID: <4lac5m$3q0@vu-vlsi.ee.vill.edu> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Summary: Bunny thermal units Xref: news.ee.vill.edu sci.engr.heat-vent-ac:6219 alt.energy.renewable:287 One often-overlooked house heating technique is rabbits. Put enough of them in a well-insulated room, and they can keep it pretty warm... Page 9.12 of the 1993 ASHRAE Handbook of Fundamentals says that a 5.41 lb normally active rabbit makes 39.22 Btu/hour of sensible heat (and another 19.31 Btu/hour of latent heat, ie water vapor), so if the room were say, 12 x 12 x 8' tall, with R20 walls and floor and ceiling and no windows or air leaks, having a surface area of 2(12x12+12x8+12x8) = 672 ft^2 and a thermal conductivity of 672/20 = 33.6 Btu/hr/F, and it were 76 F inside and 36 F outside, one would need 1344 Btu/hr to keep it warm, ie 1344/39.22 = 34.27 bunnies weighing 5.41 pounds each, making 7.25 Btu/hr/lb of heat. The ASHRAE HOF also says that a 6.61 lb cat puts out 45.57 Btu/hr, so one would only require 29.49 cats, at 6.89 Btu/hr/lb, to heat this room. Or 1210.81 mice making 1.11 Btu/hr, weighing 0.046 lb, ie 24.13 Btu/hr/lb. Heat output might exceed normally active levels, if one co-deployed both species. Larger creatures make less heat per pound, as varmint volumes increase faster than surface area. People only make about 1 Btu/hr/lb, even without fur. Off to Texas, Nick There are 89 institutions of higher learning in the Philadelphia area. What is the correct collective term for such aggregations? Would they be metaphorical facultative lagoons, which accumulate sludge in winter, and decompose it in summer? Or... "a constipation of colleges"? Article 17606 of misc.consumers.frugal-living: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: misc.consumers.frugal-living,bit.listserv.geodesic,alt.architecture.alternative Subject: Re: Frugal food for family Date: 20 Apr 1996 07:59:46 -0400 Organization: Villanova University Lines: 41 Message-ID: <4lajji$43s@vu-vlsi.ee.vill.edu> References: <1996Mar30.161702.26561@galileo.cc.rochester.edu> <4kr1il$rpt@news.mainelink.net> <4l696c$5ek@dfw-ixnews3.ix.netcom.com> <4l9v45$413@hermes.rdrop.com> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu misc.consumers.frugal-living:17606 bit.listserv.geodesic:5317 alt.architecture.alternative:273 Laurel Halbany wrote: >hstrynut@ix.netcom.com (Monica L. Tittle) wrote: >>In addition to all of the wonderful suggestions given here, you could >>also concider giving up meat. Or combine meat eating with house heating? One often-overlooked house heating technique is wabbits. Put enough of them in a well-insulated room, and they can keep it pretty warm... Page 9.12 of the 1993 ASHRAE Handbook of Fundamentals says that a 5.41 lb normally active rabbit makes 39.22 Btu/hour of sensible heat (and another 19.31 Btu/hour of latent heat, ie water vapor), so if the room were say, 12 x 12 x 8' tall, with R20 walls and floor and ceiling and no windows or air leaks, having a surface area of 2(12x12+12x8+12x8) = 672 ft^2 and a thermal conductivity of 672/20 = 33.6 Btu/hr/F, and it were 76 F inside and 36 F outside, one would need 1344 Btu/hr to keep it warm, ie 1344/39.22 = 34.27 bunnies weighing 5.41 pounds each, making 7.25 Btu/hr/lb of heat. The ASHRAE HOF also says that a 6.61 lb cat puts out 45.57 Btu/hr, so one would only require 29.49 cats, at 6.89 Btu/hr/lb, to heat this room. Or 1210.81 mice making 1.11 Btu/hr, weighing 0.046 lb, ie 24.13 Btu/hr/lb. Heat output might exceed normally active levels, if one co-deployed both species. Larger creatures make less heat per pound, as varmint volumes grow faster than surfaces. People only make about 1 Btu/hr/lb, even without fur. Larger houses with smaller surface to volume ratios would need proportionally smaller floorspace for their thermal menageries. A walkout basement seems like a good place to keep chickens, or cows, as the Swiss do, with a vapor barrier under the first floor. Off to Abilene... Nick There are 89 institutions of higher learning in the Philadelphia area. What is the correct collective term for such aggregations? Might one call them facultative lagoons, which accumulate sludge in winter, and decompose it in summer? Or "constipations of colleges"? Article 50926 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Re: A bubble wall? Date: 25 Apr 1996 15:13:10 -0400 Organization: Villanova University Lines: 37 Message-ID: <4lois6$gsm@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <317BCCC0.4539@ucs.orst.edu> <4lmfa7$1u9@vu-vlsi.ee.vill.edu> <317FBBA5.5FA0@matforsk.nlh.no> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50926 alt.energy.renewable:365 bit.listserv.geodesic:5400 alt.architecture.alternative:327 pa.environment:343 sci.environment:99097 alt.home.repair:2253 sci.engr.heat-vent-ac:6319 alt.solar.thermal:84 Andreas Haffner wrote: >Nick Pine wrote: >> David Davis wrote: >> >I have to agree with George. Logic tells me you have provided numerous >> >small wet paths for energy transfer via the bubble walls. Before the >> >bubbles transfer relied on convection in the air in the space. >> >> A lot of little convection paths in series will have more thermal resistance >> than one big one... >Misunderstanding here, I think: Perhaps so... >Before you had one large convection path Right... >With the bubbles you have many small convection paths and additionally many >*conduction* paths. That may not be so bad... Water has a US R-value of about 0.25 ft^2-hr/Btu per inch, as I recall, eg for downward heat conduction. So what would we have as the simple aggregate conductive thermal resistance owing to the water films, from one side of a wall to the other, if the 4" wall space were filled with a regular matrix of 1/4" cubical bubbles with a 0.0001" (approx 12 micron, on the order of an 80 F black body IR wavelength) wall thickness, ie if the wall cross section were 2500 parts air and 1 part water in each direction? A 2500 x 2500 foot wall would have the equivalent of a 1 ft^2 thermally conductive water shunt 4" thick with a US thermal resistance of 1, so the wall would have an effective thermal conductance of 1/(2500^2 ft^2) or an R-value of 6,250,000. Not bad :-) This is more easily investigated by experiment. We need a few more serious 12 year old scientists... Nick Article 50929 of sci.energy: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Re: A bubble wall? Date: 25 Apr 1996 15:39:09 -0400 Organization: Villanova University Lines: 61 Message-ID: <4lokct$hcq@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <4l5b9h$2b1@vu-vlsi.ee.vill.edu> <317D1EF0.436D@getnet.com> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50929 alt.energy.renewable:366 bit.listserv.geodesic:5401 alt.architecture.alternative:328 pa.environment:344 sci.environment:99100 alt.home.repair:2254 sci.engr.heat-vent-ac:6320 alt.solar.thermal:85 Brad Lindsay wrote: >Nick Pine wrote: >> Albrecht Kadlec wrote: >> >nick@vu-vlsi.ee.vill.edu (Nick Pine) writes: >> >I always care about radiation losses last: >> >conduction and convection losses come first. >>Nick, I just stumbled across your thoughts on heat movement through walls... Good... >"radiation is my last concern"...???? That was Albrecht's thought, not mine. It looks like the >> >'s above somehow got out of sync. >Maybe in your part of the country. Definitely. We are more concerned about heating than cooling here, and for that, R-values work pretty well up to some temperature like 200 F. >Here in Phoenix, we have been building test houses since 1986. What we >have found is radiation the primary source of heat movement. This was >proven in our last house using no insulation, only a reflective film >(radiant barrier) in the walls. The 2400 sq ft home consumed $56.00 in >electricity in the month of August! Sounds nice, but why so much? How about ventilating your adobe house at night or building a tower with a few 55 gallon drums full of water behind your frame house, with some south glazing on top? In the summer, allow the sun to heat up the top drums during the day and vent the whole tower at night with cooler night air, using the top as a solar chimney with stored heat from the day. Allow this cool night air to circulate into the house as well. Close the outer vents during the day. Putting a wet mesh over the lower vent would further lower the night temp on an average August day, swamp-cooler-style. And pumping some water up from a shallow pond in the ceiling above the cool drums to a shallow pond on the roof would allow additional radiative cooling on clear still nights when the roof pond could be up to 20 F cooler than the air temp, owing to night-sky radiation. You might use one window AC for dehumidification. And solar heat all the water drums in the winter. >A comparable home would use $300+ with standard insulation products which >focus on limiting conductive and convective heat movement. Sounds better and cheaper :-) Nick Nicholson L. Pine System design and consulting Pine Associates, Ltd. (610) 489-0545 821 Collegeville Road Fax: (610) 489-7057 Collegeville, PA 19426 Email: nick@ece.vill.edu Microprocessor hardware, memory, ASIC, and computer design. Telecommunication system design. Computer simulation and modeling. High performance, low cost, residential solar heating and cogeneration system design. BSEE, MSEE. Senior Member, IEEE. Registered US Patent Agent. Fluent in French. Article 5410 of bit.listserv.geodesic: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.geodesic Subject: Re: Precast Concrete Date: 26 Apr 1996 05:00:37 -0400 Organization: Villanova University Lines: 32 Message-ID: <4lq3bl$qdn@vu-vlsi.ee.vill.edu> References: <199604260409.XAA26219@id1.texhoma.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu darryl parker wrote: >Now lets say that PVC pipe was manufactured in the shape of an arch so that >none of the the molecules were being stretched to maintain that shape. Now >what would happen if you cut that pipe? Would it spring outwardly? No... The cut pipe might not move at all, unless pushed sideways. Recall Gaudi's Sagrada Familia church made with large rocks in non-vertical columns, with no mortar, because the angles and weights were correct. He made upside-down catenary-shaped models with weights and string to find the correct angles. An arch needs to develop at least 4 hinge points before it can collapse. Many modern arches are deliberately built with 3. See the delightful $14.95 Da Capo paperback book, _Structures: Why Things Don't Fall Down_, by J E Gordon ("When we play tennis or walk down stairs, we are actually solving whole pages of differential equations, quickly, easily, and without thinking about it, using the analogue computer which we keep in our minds. What we find difficult about mathematics is the formal, symbolic presentation of the subject by pedagogues with a taste for dogma, sadism and incomprehensible squiggles.") >I agree, the base of a dome is indeed under tension... Engineers... do >concentrate the bulk of their reinforcement in the "base ring"... They >seem to view this ring as receiving the bulk of the tensile forces. If the dome is a hemisphere, there is NO tension or compression in the circle on the ground, just downward force. A shallower dome pushes outward at its base, so it needs some sort of ring to contain the dome at the base, like a rotated arch. This could be a tension ring, or it could be a collection of buttresslike foundations, like the ends of an arched bridge. Nick Article 6344 of sci.engr.heat-vent-ac: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,alt.solar.thermal Subject: Another swamp thang Date: 26 Apr 1996 21:27:22 -0400 Organization: Villanova University Ah'm just back from Texas. "Why do aggies think all wise men are firemen? Because they say they have come from afar." :-) Texas is two-dimensional, with more wind in the north and sun in the west. The SE corner is more humid, with warm nights in August. The NW corner is more desertlike, with cool summer nights. Texans are starting to realize that they now use more energy per capita than anyone else on earth, as net energy importers, consuming more energy than they export. These days, Texans can make $3,000 per acre per year growing cabbages and onions, vs $2,000 per acre wind farming or $1,600 per acre pumping oil. One man says "Ah have mah very own backyard gas well, 30,000 cubic feet per day at 180 pounds per square inch. It shore is nice to be warm in the winter. Ah just use it for heat. All ah do is add stinkum. Gotta do that or you'll blow yourself up. Not worth hookin' up to a pipeline, since they're run by thieves." In Abilene, electricity comes from natural gas. One frugal Abilene house uses $100/month in winter for gas heat and $100/month in summer for air-conditioning. It has 6 window air conditioners. Can the owners use less fossil fuel? Perhaps describing a particular system to help this house will help others see how this might be done more generally, as well as in other particular ways for different houses in different situations. This house needs 200 Btu/hr/degree F of heating or cooling. With an indoor max temp of 80 F on a 24 hour average 84 F July day with an average daily high of 95 F it might need 12 hr(95 F - 80 F) 200 = 36K Btu of cooling. The average minimum nightime temperature in Abilene in July is 74 F, with a relative humidity of 71%, ie a wet bulb temp of about 67 F. Suppose we store 5 days of cooling load at this temp, allowing a thermal mass C to rise from 67 to 77 F: 36K x 5 = 180K Btu = 10 x C, requires C = 18K lb of water, so we might use 36 500 lb 55 gallon drums full of water for cooling. Let's use 42 cool drums, and put another 28 on top, behind some south glazing, to make a solar chimney to move some night air up around the cool drums. Used plastic drums cost about $2 each in Abilene. Straw bales for walls should be about the same price, and chickenwire/fiberglass ferrocement costs about 20 cents/square foot. December days in Abilene have an average 24 hour outdoor temp of 46 F and an average daytime temp of 57 F, with 1400 Btu/ft^2 of south wall sun. On such a day this house needs about 24 hrs(68F-46F)200=100K Btu to keep warm. Water heating might require another 50K Btu/day. How much low-thermal-mass sunspace glazing is needed to keep this house at 68 F on an average December day? Let's assume that 100% of the of sun that falls on the sunspace glazing passes into the sunspace, which has a temperature of 87 F during an average 6 hour day, when the outdoor temp is 57 F. A shallow low-thermal-mass sunspace would lose about 6 hr (87-57) = 180 Btu/ft^2 when the sun is shining, and lose no heat at night, for a net gain of about 1200 Btu/ft^2/day, so keeping the house warm would require a minimum of about 100K/1.2K = 83 ft^2 of "solar siding," or an 8' tall x 12' wide x 4' deep sunspace, or an 8' tall x 16' long x 8' deep sunspace. The sunspace glazing could be smaller if the ground in front had a reflecting pond or a white surface. To avoid heat gain in the summer we might use a 4' overhang, some operable vent doors, and some greenhouse shadecloth hanging inside in the winter and outside over the glazing in summer. How warm would our 70 drums full of water have to be to store enough heat for 5 days without sun? Storing 5 x 150K Btu with a heat capacity C = 70 x 500 = 35,000 Btu/degree F and a minimum usable drumwater temp of about 80 F, means the fully-charged drumwater temp for this heat battery should be at least T = 80 F + 750K Btu/35K Btu/F = 101 F. night pool Suppose our swamp thing looks like this: .......... --- (from the east) g D hot. vent door . g Drums. <--south . . g....... . . cool . 16' . . . vent . Drums. . sun . house . D D . pond? . space . vent . D D . vent door ...................................................................... 8' (from the top) ........ . D D . The upper solar closet part of this structure . D D . might have 8' x 16' of south glazing, with 2 . D D . layers of drums stacked vertically. The lower . D D . 16' part might have 3 layers of vertically-stacked . D D . drums with 14 drums in each layer. There might . D D . be a shallow EPDM rubber pond on the bottom, . D D . another pond between the upper an lower parts, ........ another just under the roof, and another on top of the roof, with straw bales underneath. The floor of this drum structure might be the lower EPDM rubber pond, a few inches deep. We would need to pay attention to fire ants and termites in Abilene, as well as rodents, where the straw bales touch the ground. It seems to me that a rubble foundation wall with strawbales laid on top, surrounded by a half- inch of ferrocement would take care of all that. Here's a quote from page 468 of Aden B. and Marjorie P. Meinel's 1977 book, _Applied Solar Energy_: In our home solar heating system we used water as the thermal storage medium for an air-transfer unit, the water being contained in 1000 one-gallon polyethylene bottles stacked so that air could flow between them. They worked satisfactorily until some desert pack rats invaded the storage bin, making nests of the insulation and chewing holes in the water bottles. What will the drum temperature be after a string of average December days? With an average roof reflectivity of 60% (some aluminum paint) we might have a solar input of about 1400 x 1.6 x 128 ft^2 = 287K Btu/day. If we stored this heat all over inside the structure, we would lose heat through the 128 ft^2 of R1 south glazing during the day, and the 128 ft^2 of R30 wall behind the glazing and the other 768 ft^2 of R30 straw bale walls at night. If the energy that flows into the drum structure, Ein, equals the energy that flows out of the structure on an average day, then we have Ein = 287K, and Eout = 6 hr (T-46) 128 ft^2/R1 south glazing, day +18 hr (T-46) 128 ft^2/R30 " " night +24 hr (T-46) 768 ft^2/R30 remainder of structure, 24 hours = (T-46)(768+76.8+614.4) = 1460(T-46) = 287K = Ein, so T = 46 + 287K/1460 = 242.7 F. Of course the water won't really get that hot, because it will boil at 212 F, and radiation loss will limit the temperature sooner than that. Suffice it to say the water temp in December should be greater than 101 F, even though the structure is only half-glazed on the south side. Moving the structure away from the house so it is no longer shaded below and glazing the whole south side would make it collect more solar heat. The purpose of the EPDM rubber pond on the ground is to help transfer heat downwards from the glazed area above. We need to transfer about 80 K Btu/day from the upper drums to the lower ones, and we might do this by pumping some water up from the ground level pond to the pond under the ceiling at the top of the structure. How much water? 80K Btu/24 hours = 3.4K Btu/hour. If the upper pond water were 10 F warmer than the lower pond water, we would need to move 340 pounds of water per hour or 5.6 pounds of water per minute or 0.7 gallons per minute from the lower pond to the upper one, ie 16', which we could do with a perfect 0.003 horsepower immersion pump in the lower pond, requiring 2 watts of electrical power if it were 100% efficient. The ceiling pond might also be used to extract winter heat for the house, especially if the 55 gallon drums below had a thermal conductor like sand between their tops and bottoms. If the ceiling pond water were 10 F cooler than the drumwater, the maximum heat transfer rate via the ceiling pond might be something like 10 F (70 drums x 25 ft^2/drum) x 1.5 Btu/hr-ft^2-F = 26K Btu/hour, corresponding to an outdoor temp of 68 - 26K/200 = -63 F for this house. A fan below the ceiling pond would increase the heat transfer rate. The house might use a fan coil unit or auto radiator to transfer the heat from the ceiling pond water to the house air. Domestic hot water could be supplied via a simple concentric pipe heat exchanger located beneath the existing water heater in the house, upstream of the fan coil unit in the same circulation loop. The heat transfer rate from the house to the lower pond in the summer would also depend on the lower pond-drumwater temperature difference. If the house were 80 F, and the floor pond water were 77 F, and the outdoor temperature 95 F, the house would need 3K Btu/hour of cooling, which might come from a few $139 all-copper 2' x 2' SHW 2347 duct heat exchangers made by Magicaire, which transfer 45K Btu/hour between 125 F water and 68 F air at 1400 cfm, with a 0.1" H20 pressure drop, attached to the suction side of a few $11 window fans. How many of these fan coil units would we need to cool the house, at 95 F? At a temperature difference of 3 F, each one should transfer 45K x 3/(125-68) = 2368 Btu/hour, so one or two should be enough, especially if the house still has one window air conditioner for dehumidification. There are still a few details to work out here. Direct heat transfer from the drums to the house air via vents would be more efficient, but that might involve Legionnaire's disease or swampy smells. In the summer, we need to remove 36K Btu/day from the lower drums on an average night, by letting some 67 F moist air flow over them, drawn in by a fan, or a vacuum created by the solar chimney above (perhaps with help from a windscoop using the average 10.3 mph wind in Abilene in July.) A solar chimney with height H feet between unobstructed top and bottom vent openings each having area Av square feet, with a temperature difference of DT degrees from top to bottom will have an approximate airflow Q in cfm of Q = 16.6 Av square root (H DT). For instance, if the vents have an area of 8 ft^2 and the height is 8' and the temperature at the top of the chimney is 100 F and the temperature at the bottom is 80 F, the chimney will have an airflow of about Q = 16.6 (8 ft^2) square root (8' (100 F - 80 F)) = 1680 cfm. Suppose we make our vent doors 8 square feet, eg 8' long x 1' wide. The warm part of our chimney is 8' tall. What does the temperature difference DT between the outside air and the solar closet have to be to remove 36K Btu from the drums overnight, assuming the drums below are a perfect heat exchanger? An airstream of Q cfm with a temperature difference DT moves about DT Q Btu/hour of heat, so overnight we need DT Q cfm x 60 m/hr = 36K Btu, ie DT (16.6) (8) square root (8 DT) (60) = 36K Btu, or DT^(3/2) 1358 = 36K, or DT = (36K/1358)^(2/3) = 8.9 F. This shouldn't be too hard to manage, since with the roof reflector the summer solar input should be about the same as the winter input, which made for almost a 200 F temperature rise above ambient... The roof pond might be used for further summer cooling, by pumping some water up from the pond above the cool drums through the roof pond on a clear night with no wind. Baruch Gavoni's _Passive and Low-Energy Cooling of Buildings_ book says that under these circumstances, rooftop temperatures can be up to 10 C below outdoor air temperatures, owing to night sky radiation, even with no evaporation of water. Nick Article 79 of alt.solar.photovoltaic: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.solar.photovoltaic,alt.energy.renewable,sci.engr.heat-vent-ac,alt.solar.thermal Subject: Re: Solar on the Road... Date: 27 Apr 1996 09:14:02 -0400 Organization: Villanova University Lines: 26 Message-ID: <4lt6iq$frm@vu-vlsi.ee.vill.edu> References: <4lst3c$83k@news.wco.com> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu sci.energy:50995 alt.solar.photovoltaic:79 alt.energy.renewable:392 sci.engr.heat-vent-ac:6356 alt.solar.thermal:90 Donald Kulha wrote: > I've been working on a somewhat interesting project lately... Sounds nice :-) >The maximum daily power production has been about 1400w so far... I guess you mean 1400 W-h? Are you wasting the rest of the 8,000-10,000 W-h of sun that falls on the photovoltaic panels on the roof of your van as heat? > The main use of the system will be to power computers, lights, a fan, >my coffee grinder, a stereo, a deskjet 660 and misc other stuff when I >work with friends on our CD-ROM. The system also powers a CB, a >2-meter/440mhz Kenwood transceiver, a TNC, a cell phone and charges >various sized small nicads for radios, flashlights, a shaver, etc. You don't mention how you keep the van warm inside or make hot water. Perhaps the fan could be a solar chimney. Or you might trickle a little water over those PV panels, under another layer of single polycarbonate glazing. Or hook up a small model-sized jet engine powered by Freon, a mini-version of the Ormat turbine generators used to make 5 million watts of electrical power from 63 acres of solar salt ponds in the dead sea, starting from 170 F brine. Nick Article 355 of pa.environment: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.energy.renewable,bit.listserv.geodesic,alt.architecture.alternative,pa.environment,sci.environment,alt.home.repair,sci.engr.heat-vent-ac,alt.solar.thermal,sci.engr.lighting Subject: Re: A bubble wall? Date: 29 Apr 1996 11:03:39 -0400 Organization: Villanova University Lines: 200 Message-ID: <4m2lob$d4e@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <4l5b9h$2b1@vu-vlsi.ee.vill.edu> <317D1EF0.436D@getnet.com> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Keywords: science project Xref: news.ee.vill.edu sci.energy:51040 alt.energy.renewable:414 bit.listserv.geodesic:5443 alt.architecture.alternative:361 pa.environment:355 sci.environment:99421 alt.home.repair:2524 sci.engr.heat-vent-ac:6403 alt.solar.thermal:98 sci.engr.lighting:4780 Still thinking about my 12 year old friend who added 1/4 tsp of lemon juice to her standard bubble mix (1/2 cup green Dawn, 3 Tbs glycerin, 2 quarts H2O) to make the bubbles last 111 seconds at 80 F and 506 sec at 45 F, vs 309 sec and 185 sec; 1/4 tsp of maple syrup instead made this 431 and 345 sec. What is a good bubble solution for blocking longwave IR radiation from a house window? What is that IR wavelength? Black bodies radiate heat at many wavelengths. Planck's law describes a curve with a peak for this, ie at wavelength lambda, a blackbody with temperature T (Kelvin) radiates with an intensity E(lambda) = C1/(lambda^5[exp(C2/(lambda T))-1]), where C1 = 3.74 x 10^-16 m^2W and C2 = 0.0144 mK. Wein's displacement law says where the peak is: the wavelength corresponding to the maximum intensity of blackbody radiation is Lmax = 2898/T microns. 80 F is about 27 C or 300 K, so the wavelength with max intensity at 80 F is about 10 microns or 0.0004 inches, ie just less than half a thousandth of an inch. How can we measure a bubble thickness like that? What makes bubble walls thick? Compared to the intensity at this wavelength, this blackbody radiates at some other wavelength L with a relative intensity of approximately Irel = (Lmax/L)^5 x exp(C2/(Lmax T)-1)/exp(C2/(L T)-1). L: 1 micron 10^5 120.5 / 7 x 10^20 = 1.7 x 10^-14 5 microns 32 120.5 / 14765 = 0.26 10 microns 1 120.5 / 120.5 = 1 20 microns 0.031 120.5 / 10 = 0.38 50 microns 0.00032 120.5 / 1.61 = 0.024 It looks like thicker bubble walls are better, up to the point where the bubble wall itself begins to be a sideways path between the two glazings. If the bubble wall were 10 times thicker than the longest interesting wavelength, (as people think about transmission lines), it might be 500 microns or 0.020" thick, which seems very thick for a bubble. A wall 4" thick filled with 0.2" bubbles like that would have a 10% water cross section, so we might think of such a 10' x 10' wall as having a 1' x 1' thermal shunt made of water with a thermal conductance of 1 Btu/hr. If that were the only thermal path, that wall would have an R-value of 100... Perhaps a bubble with a given wall thickness is a better insulator at higher temperatures with shorter wavelengths. Water has an index of refraction of about 4/3, so each air-water interface with a sufficiently thick layer of water compared to a wavelength would have a Fresnel loss of about ((4/3-1)/(4/3+1))^2 = 1/7^2 = 2%. A 4" thick wall with 20 clear 0.2" bubbles in series might have an attenuation of 1.02^20 = 1.5 for IR radiation. Not much... We may need smaller bubbles than that, perhaps with thinner walls and some dye. Let's see, an 80 F room loses about (80-30)/R2 = 25 Btu/hr/ft^2 of heat on a 30 F day through an ordinary double glazed window. Two layers of poly film with little greenhouse effect (IR blocking) have an R-value of about 1.2... And a 1 ft^2 80 F blackbody with no glazing radiates 0.174E-8(460+80)^4 = 148 Btu/hr, while the 30 F world radiates 100 Btu/hr back at it, so it loses 48 Btu/hr by radiation, ie the R-value owing to radiation is about 1 (50/48.) An attenuation of 10, ie 1.02^N=10 makes N=ln(10)/ln(1.02)=114 0.035" diam. bubbles across a 4" wall, at 28 bubbles per inch... How big are the bubbles that come out of an airstone in an aquarium? What happens if we remove the fish and fill the aquarium with some interesting soaps and IR dyes (?) and warm water, and glue some foamboard on the sides (or start with a styrofoam cooler) and put a glass lid on the top and measure how fast the water cools with two thermometers and a clock... Suppose our cooler is 1' tall x 1' wide x 2' long with a 1' x 2' glass lid, and the sides are 1" thick R4 white beadboard, coffeecup foam, with a thermal conductance of Coth = 8 ft^2/R4 = 2 Btu/hr-F. This situation might be like a bubblewall ceiling under a clear polycarbonate roof, with natural daylighting and vertical heatflow. Without the bubbles, we might have a thermal conductance of Coth + 2 ft^2/R1 = 4 Btu/hr-degree F. With bubbles, the conductance might decrease to Coth + 2/Rx, close to 2 if Rx is large. So if we filled the cooler it with 8" of 130 F water, ie 80 pounds of hot water, we might expect the box with no bubbles to lose (130-70)4 = 240 Btu to a 70 F room in an hour, reducing the water temp to 130-240/80 = 127 F. The box might be 124 F after 2 hours or 70+(130-70)exp(-4/20) = 119 F after 4 hours, since the RC time constant of the box would be about 1/4*80 = 20 hours with no bubbles. (After the first hour, the water is cooler, so it loses less heat in the next hour, so the temperature drops less in the next hour, etc.) If we measure a water temperature of Tb (F) after 20 hours, with bubbles, and Tnb without bubbles, what is Rx? T = 70+(130-70)exp(-20/RC), so RC = -20/ln((T-70)/60) = R x 80, so R = -1/(4 ln((T-70)/60). Suppose we measured Tnb = 92 F and Tb = 106 F. Then Rnb = -1/(4 ln((920-70)/60) = 0.24918 F-hr/Btu and Rb = 0.48940, so 1/Rnb-1/Rb = (Coth+2/R1)-(Coth+2/Rx) = 2 - 2/Rx, so Rx = 2/(2+1/Rb-1/Rnb) = 2/(2+2.0433-4.0132) = R33. Dr. Aristid Grosse made bubbles that lasted more than a year, as did Belgian physicist Joseph Plateau in the 1800s. Dr. Grosse's principles of bubble health and long life are: 1. Dust is the enemy of bubbles. 2. Carbon dioxide poisons bubbles (better bubbles are blown by non-humans), and 3. Bubbles love cold. They also like humidity. Glycerin helps bubbles fight humidity. Maybe we don't need it inside a glazing cavity with 100% humidity. Perhaps this should be a closed system, to avoid building up dust. Something like this? ---------------------------- | ---------------------- | sand filter?--> | | <-- | | <--bubbles | | | | | | ---------- | | | | | - air | --> | | | -- | | pump ---- | | | ---- ---------- | | | <--water |w| | | |wwww| <--water level | | | -- | | | ---- | | | water return-> | | | --------------------- | ---------------------------- Let's all try to invent an insulating bubble wall, perhaps starting with two pieces of glass or single-layer polycarbonate plastic with butyl tape or caulk over a plastic 1x3" or foamboard frame that can be filled between with bubbles at night emerging from an aquarium airstone immersed in a soapy solution at the bottom. This could really be useful in a passive solar house or a greenhouse, like Beadwall. Simple, elegant, movable insulation. During the day, the sun shines in on some thermal mass, and at night the glazing fills up with bubbles, keeping the heat in. Commercial greenhouses use two huge layers of UV-treated polyethylene film inflated to form an air pillow 4" thick. A tiny 50 watt blower can inflate a 1 acre greenhouse. Would bubblewalls work with poly film pillows? Bubbles tend to last longer in cold humid conditions. A layer of frozen bubbles inside an outside glazing might be very good insulation on a very cold night. Perhaps there is an optimal bubble size for insulation. Too small, and convection losses might be small, but conduction losses and air pump power and water transport thermal losses might be large. Too big, and convection losses go up. Ohm's law for heatflow is a good starting point here: the amount of heat Q in Btu/hour that flows through a wall with area A ft^2 and R-value R and temps Ti (F) on one side and To on the other, is Q = (Ti-To)A/R. Here's another bubble wall test setup, a 2' cube divided in half by a bubble wall that might have an R-value of 2 when empty and 20 when full. We might make the cube out of 2" Styrofoam with an R-value of 10. One side could be kept at 32 F with some melting ice at the top, with some foam on top and around the window screen ice tray, and the other side could be kept at 132 F with a thermostat and a light bulb, with a piece of aluminum foil to shade the bubblewall from the bulb. How much ice water might we collect in an hour with the bubblewall empty and full of bubbles? This might be a more accurate way to measure the R-value than the aquarium way, especially since house windows are usually vertical, with lower heat losses. What might we get for readings in each case if we hook up the light bulb to a kWh meter? It's nice to have two ways to check the heatflow through the bubble wall. ......................... 70 F room . ice .. . . ......................... . . .. . . . To .. Ti . R10 . 2' 2' . 32 F .. 132 F . . . .. light . . . .. bulb . . ......................... 2' 1' 1' ^ |___ bubble wall It takes 144 Btu to melt a pound of ice, and there are 3410 Btu in a kWh. Here is the following electrical circuit analog: Iir 32 F 132 F Ier --> | <-- | --> 70 F ---wwww---*---wwww---*---wwww--- 70 F R10/12 | Rx/4 | R10/12 = 0.83 | | = 0.83 | | --- ^ --- Ui --- | --- | Ue | --- --- - - Where Ui and Ue are flows of ice and electrical energy (Ui flows down, in this picture.) What would Ui and Ue be if Rx were 2 without bubbles and 20 with bubbles? In either case, Iir = (70-32)x12 ft^2/R10 ft^2 = 45.6 Btu/hr flows into the ice from the room, and Ier = (132-70)x12 ft^2/R10 = 74.4 Btu/hr flows out of the light bulb into the room. If Rx = 2, an additional (132-32)x 4 ft^2/R2 = 200 Btu/hr flows out of the light bulb into the ice, and if Rx = 20, only 20 Btu/hr more flows that way. The total ice and electrical energy flows would be Rx = 2 (no bubbles) Rx = 20 (bubbles) Ui 245.6 Btu/hr (27.3 oz ice water/hr) 65.6 (7.3 oz ice water/hr) Ue 274.4 Btu/hr (80.5 watts) 94.4 Btu/hr (27.7 watts) Nick Article 476 of alt.energy.renewable: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,sci.energy,alt.solar.thermal,alt.architecture.alternative,pa.environment,sci.engr.heat-vent-ac,alt.home.repair Subject: Re: A bubble wall? Date: 4 May 1996 09:11:26 -0400 Organization: Villanova University Lines: 106 Message-ID: <4mfl1u$ng3@vu-vlsi.ee.vill.edu> References: <4j45me$jmk@vu-vlsi.ee.vill.edu> <317D1EF0.436D@getnet.com> <4m2lob$d4e@vu-vlsi.ee.vill.edu> <168632949wnr@tfc-bham.demon.co.uk> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Xref: news.ee.vill.edu alt.energy.renewable:476 sci.energy:51219 alt.solar.thermal:104 alt.architecture.alternative:406 pa.environment:365 sci.engr.heat-vent-ac:6521 alt.home.repair:3007 C:WINSOCKKA9QSPOOLMAIL wrote: >> Black bodies radiate heat at many wavelengths. Planck's law describes >> a curve with a peak for this, ie at wavelength lambda, a blackbody with >> temperature T (Kelvin) radiates with an intensity >> >> E(lambda) = C1/(lambda^5[exp(C2/(lambda T))-1]), where >> >> C1 = 3.74 x 10^-16 m^2W and >> C2 = 0.0144 mK. >Something that has been bugging me for the last week, and I can't believe >I stumbled upon it on the Net - how exactly do you calculate >[exp(C2/(lambda T))]? I use the "e-to-the-X" button on my $20 Casio fx-991H calculator, which takes the base of natural logs, e = 2.718... to the Xth power. For instance, exp(1) is 2.71828..., exp(2) is 7.389... If T is 300 Kelvin and lambda is 10 microns, ie 10 x 10^-6 meters, exp(C2/(lambda T)) = exp(0.0144/(10^-5 x 300)) = exp(4.8) = 121.5104... >I've been attempting to learn about solar radiation from first principles >from my copy of 'Solar Engineering of Thermal Processes' by Duffie and >Beckman That is not an easy thing to do. I hope you are using the second edition, 1991, I often have trouble following that good book, with BS and MS degrees in electrical engineering. >Many thanks if you can help the mathamatically challenged :-( Glad to try, altho it seems to me that we only need arithmetic to do solar space heating, with at most high-school algebra. Another common and more easily-understood application of exponentials is in calculating how fast a house or some other thermal mass with insulation around it cools... A thermal mass C surrounded by a thermal resistance R has a natural RC "time constant" with a dimension of time, eg in hours. If we heat the thermal mass up to some temperature DT above the surrounding temperature Ta, RC is the time it will take to the temperature difference DT to decrease to 1/e th, ie about 1/3 of its original value. For instance, an 8' cube of water surrounded by (US) R-20 insulation has C = 62 x 8^3 = 31K pounds of water with a thermal mass of 31K Btu/degree F, and a thermal resistance R = 20/(8x8x6) = 0.052 F-hr/Btu, so it has an RC time constant of RC = 32K x 0.052 = 1653 hours or 68.9 days. So if we heat the water up to an initial temperature T(0) = 100 F and sit the cube in a Ta = 70 F room, the water temperature T(D) after D days will be T(D) = Ta + (T(0)-Ta) exp(-D/(RC), so after 10 days, the water temperature would be T(10) = 70 + (100-70) exp(-10/68.9) = 70 + 30 exp(-0.145) = 95.9 F. After 68.9 days, the temperature would be T(68.9) = 70 + 30 exp(-1) = 70 + 11 = 81 F. After a year, the temperature would be T(365) = 70 + 30 exp(-5.3) = 70.15 F. If we made this a 16' cube with R40 insulation, we would have RC = 62 x 16^3 x R40/(16^2 x 6) = 6613 hours or 276 days, so after a year the water temperature would be T(365) = 70 + 30 exp(-365/276) = 78 F. If this cube were outside in 30 F air for a year, the water temp would be T(365) = 30 + (100-30) exp(-365/276) = 38 F. If we added an solar air heater with R1 glazing over one insulated side of our 8' cube, with some simple plastic flap dampers to let the warm air into the cube during the day and keep out the cold air at night, and collected 8' x 8' x 1000 Btu/ft^2 of heat over 6 hours every day (an average December day in Philadelphia), and waited a year, ie 5 time constants, the water would forget its original temperature, and if the average outdoor temperature over the year were 55 F, the water would have a more or less constant temperature T such that the energy that flowed into the cube every day would equal the energy that flowed out of the cube: 64K Btu/day = 6(T-55)64 ft^2/R1 air heater side, day + 18(T-55)64 ft^2/R20 air heater side, night + 24(T-55)64x6 ft^2/R20 other sides, 24 hours a day, ie 64 K = (T-55)(384+57.6+460.8) = 902.4(T-55), so T = 55 + 71 = 126 F. This might be an interesting outdoor exhibit at a science museum or some unusual outdoor art at a college, a monolith moving even more slowly than a very large Foucault pendulum, reminding us that solar energy really can work in partly cloudy climates, if well-applied. We might fill up this 8' cube with 18 55-gallon plastic drums full of water, each 3' tall and 2' in diameter, in two 3x3 drum layers, with about 300 2-liter plastic soda bottles tucked around in the spaces among them, inside a few 2x4s and $100 worth of 6 1/2" fiberglass insulation, or strawbale/mortar walls, with a "truth window" exposing a large thermometer inside. I have the drums... Nick Article 19010 of misc.consumers.frugal-living: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: misc.consumers.frugal-living Subject: Re: Gallon Milk Jugs & Two Liter Pop Bottles Date: 8 May 1996 05:29:51 -0400 Organization: Villanova University Lines: 8 Message-ID: <4mppif$a60@vu-vlsi.ee.vill.edu> References: <4ml9mk$l4@mercury.IntNet.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu Two liter soda bottles might be an interesting way to store heat in a solar house or solar closet. Fill them with water and cast them into hexagonal or triangular blocks of 7 or 10, using molds with 10% fiber or ferrocement, leaving the tops exposed, to make furniture, room dividers, bookcases, etc? Nick Article 445 of alt.architecture.alternative: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,sci.energy,sci.engr.heat-vent-ac,alt.solar.thermal,alt.home.repair,pa.environment,sci.environment Subject: Re: Seek Passive Solar Design FAQ/Guide Date: 8 May 1996 12:41:11 -0400 Organization: Villanova University Summary: ignorance is bliss Keywords: arrogance, greed, politics, physics, advertising William R Stewart wrote: >george p swanton wrote: >> >> Can anyone offer a pointer to a set of formulae for glazing/ >> mass/temperature/etc calculations involved in passive solar >> design? I am interested primarily in direct gain residential >> space heating applications. > >These calculations are somewhat complex, if you are considering passive >solar as your main heat source. The Passive Solar Industries Council >has a complete book and software program for this engineering problem. > > Passive Solar Industries Council > 1511 K St., #600 > Washington, DC 20005 > (202) 628-7400 Yeah, the brick people :-) Give them a call if you want to fill up your sunspace with thermal mass and cripple the performance, while raising the price dramatically :-) Or if you want your "main heat source" to provide less than half the heat for your house. Two views on sunspace design: It is hard to think of any other system that supplies so much heat (to an existing house) at such low cost... One could shorten the warm-up time of the enclosure and increase the amount of heat delivered to the rooms by making the enclosure virtually massless--by greatly reducing its dynamic thermal capacity. This can be done by spreading a 2-inch-thick layer of lightweight insulation on the floor and north wall of the enclosure and then installing a thin black sheet over the insulation. Then, practically no heat is delivered to the massive components of floor or wall; practically all of the heat is promptly transferred to the air. And since the thermal capacity of the 100 or 200 lb. of air in the room is equal to that of one fourth as great a mass of water (about 25 to 50 lb. of water), the air will heat up very rapidly. I estimate that its temperature will rise about 40 F. degrees in about two minutes, after the sun comes out from behind a heavy cloud cover. At the end of the day, little heat will be "left on base" in the collector floor or north wall and, accordingly, the enclosure will cool off very rapidly. New Inventions in Low Cost Solar Heating-- 100 Daring Schemes Tried and Untried by William A. Shurcliff, PhD, Physics, Harvard Brick House Publishing, 1979, 293 pages, $12 A sunspace has extensive south-facing glass, so sufficient thermal mass is important. Without it, the sunspace is liable to be uncomfortably hot during the day, and too cold for plants or people at night. However, the temperature in the sunspace can vary more than in the house itself, so about three square feet of four inch thick thermal mass for each square foot of sunspace glazing should be adequate... The sunspace floor is a good location for thermal mass. The mass floors should be dark in color. No more than 15-25% of the floor slab should be covered with rugs or plants... Another good location for thermal mass is the common wall (the wall separating the sunspace from the rest of the house)... Water in various types of containers is another form of energy storage often used in sunspaces. Passive Solar Design Guidelines-- Guidelines for Homebuilders for Philadelphia, Pennsylvania Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates Current (1995) edition, 88 pages, $50 So, which is the most energy-efficient sunspace in a partly cloudy climate like Philadelphia? Shurcliff's plastic film sunspace, wearing the green uniform in this contest, might cost about $1/ft^2, and on an average December day at 36 F, it would receive about 1000 Btu/ft^2 of sun, like the PSIC sunspace. Let's assume that both sunspaces have a perfectly insulated wall between them and the house, to avoid the thermal disaster of a poorly insulated Trombe wall in a partly cloudy climate, and let's assume there is no air infiltration from the outside in either case. The sunspace air would be circulated through the house with some dampers or fans, keeping the sunspace at 80 F, say, while the house remains at 70 F. With single glazing, about 900 Btu/ft^2 of sun might enter the sunspace during the day, and the amount of heat lost through a square foot of Shurcliff's sunspace over a typical day would be about 6 hr (80-36)/R1 = 264 Btu/ft^2/day, for a net gain of 636 Btu/ft^2, ie his $1/ft^2 sunspace would be about 64% efficient, as a solar collector. A 16' x 32' sunspace like this costing $500, along with a solar closet containing 20 55 gallon drums full of water, could provide all of the heat and hot water needed for an attached 32 x 32' two-story house with an average R20 envelope. As an auxiliary living space, it could be heated up instantly on some starry night for a party, by moving some warm air from the house into the sunspace. This sunspace might have a single layer of mylar glazing made by Bayer or Dow chemical, distributed by Replex or Armin Plastics, stretched over some curved galvanized pipes, with their curved ends tucked under the south eave of a two story house. The film might be attached with aluminum extrusion clamps around the perimeter of the sunspace, with a landscaping timber foundation, staked to the ground with 4' of #4 rebar. The sunspace might have a layer of green colored greenhouse shadecloth hanging inside to help absorb the sun. Opening some vents and hanging the shadecloth over the outside in summertime would keep the sunspace and house cooler, and prolong the life of the glazing. The sunspace might have a crushed stone floor over black polyethylene film, with a shallow reflecting pond in front, made from a single layer of EPDM rubber draped over a low perimeter earth berm. A transparent motorized damper in a first floor window would allow house air to flow into the sunspace, if the sunspace were warmer than 80 F and the house were cooler than 70 F, and a second floor window fan with a one-way plastic film damper would move air from the sunspace into the house when the house needed heat, with the first floor damper open. The fan would also operate on windy days and nights, perhaps with the downstairs damper closed, to create a slight vacuum inside the sunspace, to avoid plastic film fatigue. The PSIC sunspace, wearing the brown uniform, would perform better with double glazing. It might cost $10/ft^2, with a 4" concrete thermal mass with an official PSIC heat capacity of 8.8 Btu//f-ft^2. Say the concrete absorbs 100% of the sun that falls on it, vs the official PSIC solar absorptance of 0.65 (table K, page 57.) Then about 800 Btu/ft^2/day of sun will enter the double glazing and be absorbed by the concrete, and the concrete surface will warm up the sunspace air, and that warm air can be used to heat the house when the sunspace temperature is more than 80 F. Suppose the concrete loses no heat at all to the soil below (I'm giving quite a few handicaps to the PSIC sunspace in this efficiency race.) The concrete might start the day at temperature T, and charges up in the sun to a max temperature of T + dT, and return to temperature T at dawn. How can we calculate T and dT? The equivalent electrical circuit looks something like this: Ts sunspace temperature | R2 | D 36 F ---------wwww-----------------|-------------------- 70 F outdoors glazing | open damper to heat house w w R0.5 concrete - sunspace air resistance 800 Btu/ft^2 w per day | | --- | | | ----|-->|------|--Tc concrete temperature | --- | sun current w source w R0.4 concrete bulk thermal resistance w | ------- 26.4 Btu/F thermal mass of concrete ------- | --- - Let's simplify this by assuming the thermal mass of the concrete is infinite, vs 8.8 Btu/F-ft^2. Lots of concrete, or a water wall, or something with so much thermal mass that the temperature inside the sunspace never changes at all from day to night over a long string of average December days, with some sun. This is an optimal sunspace with more than "adequate" or "sufficient" thermal mass by official PSIC standards. Let's also assume that the two small resistors have a value of zero, ie let's ignore the R0.4 bulk thermal resistance of the concrete, that makes the surface heat up more than the inside, while the sun is warming it up, and makes it harder to get heat out of the inside of the concrete and into the sunspace air, and the R0.5 concrete-sunspace air resistance, by assuming both are R0 conductors. What will Tc be in that simplified case? The sun shines into the sunspace during the day and adds 800 Btu to our concrete capacitor, and over 24 hours, 24(Tc-36)1ft^2/R2 = 12 Tc - 432 Btu flow out of the capacitor. If Ein = Eout (providing no heat for the attached house), then Tc = (800+432)/12 = 103 F. Pretty nice, but this sunspace is not providing any heat for the house, just keeping itself warm on an average day, and losing lots of heat on a cloudy day. Suppose we allow some heat to flow from the sunspace into the house, ie close the switch, ie turn on the fan or open the damper between the sunspace and the house often enough to limit the maximum sunspace temp to 80 F instead of 103 F. Then the heat loss to the outside world over the course of a day is 24(80-36)1 ft^2/R2 = 528 Btu, and the rest of the heat that enters the double glazing, ie 800 - 528 = 272 Btu/ft^2/day goes into heating the house, so the solar collection efficiency of this $10/ft^2 sunspace in terms of useful heat provided for the attached house is 27%. As an auxiliary living space, the temperature of this sunspace is largely out of our control. It takes a long time and a lot of house heat to warm it up on an evening or cloudy day, and after we leave the space, it stays warm for a long time, giving up precious house heat to the outside world. How curious that by carefully following the current official guidelines of the Passive Solar Industries Council, we can reduce the performance of Shurcliff's low-thermal-mass sunspace from 64% to 27%, while increasing the price from $1/ft^2 to $10/ft^2, unimproving the cost-effectiveness of the sunspace by a factor of 12, even with all these PSIC-slanted assumptions... Here's a quote from the Acknowlegements section of the PSIC guidelines: _Passive Solar Design Strategies: Guidelines for Home Builders_ represents over three years of effort by a unique group of organizations and individuals. The challenge of creating an effective design tool that could be customized for the specific needs of builders in cities and t towns all over the U. S. called for the talents and experience of specialists in many different areas of expertise. _Passive Solar Design Strategies_ is based on research sponsored by the United States Department of Energy (DOE) Solar Buildings Program, and carried out by the Los Alamos National Laboratory, the National Renewable Energy Laboratory (NREL)... and the Florida Solar Energy Center (FSEC.) The National Association of Home Builders (NAHB) Standing Committee on Energy has provided invaluable advice and assistance during the development of the Guidelines. Valuable information was drawn from the 14 country International Energy Agency (IEA) Solar Heating and Cooling program, Task VII on Passive and Hybrid Solar Low Energy Buildings... Although all the members of PSIC, especially the Technical Committee, contributed to the financial and technical support of the Guidelines, several contributed far beyond the call of duty. Stephen Szoke, Director of National Accounts, National Concrete Masonry Association, Chairman of PSIC's Board of Directors during the development of the Guildlines; and James Tann, Brick Institute of America, Region 4, Chairman of PSIC's Technical Committee during the development of these guidelines... gave unstintingly of their time, their expertise, and their enthusiasm. >Some of the variables involved in such a design include; >What is the heat loss rate of your structure? Yes, that's a good thing to know... "Ohm's law for heatflow"... Note glass is a very poor insulator... A 30 x 30' x 2 story house with R20 walls and ceiling might have a thermal conductance of 2000 ft^2/R20 = 100 Btu/hr-F. Make 10% of the wall area windows by adding 200 ft^2 of R2 glass and this doubles to 200 Btu/hr per degree F--unless the glass is in a thermally isolated sunspace, in which case the thermal conductance and heat loss of the house go down, not up... >What is the solar insolation in your area and when does it occur? Also good to know, eg the amount of sun that falls on a south wall on a December day, as well as the average temperature in December. If your house stores heat for several days, these averages are good enough for design. You don't need to know much more detailed weather data. (Altho it is very nice to be able to simulate the performance of a house design easily, hour by hour, over the last 30 years, if you want to do that, with the NREL/NOAA CD-ROM data.) >http://solstice.crest.org/renewables/solrad/index.html Joe McCabe, PE, lives there :-) >What are your backup systems (eg, masonry fireplace, ground-source >heat-pump, etc)? Ideally none. This is how some people define a "solar house," ie one with no other form of heat... Simple, no? Such a house can be easily designed with some high school physics and algebra, as licensed Professional Engineer Norman Saunders has been doing in cold, cloudy New England since 1944. Or... you can follow the orthodox Passive Solar Industries guidelines above, which say that no matter how hard you try, you can't provide more than 41% of the heat needed for a house in the (warmer, sunnier) Phildelphia area using the sun, if you fill up your sunspaces with bricks, that is :-) * * * Here's the scoop. The way to do this is simple. Start by finding 3 numbers: 1. Find the heat loss for your house, eg 200 Btu/hr per degree F. 2. Find the average temperature in December where you live, eg 36 F. 3. Find the average amount of sun that falls on a south wall in December where you live, eg 1000 Btu/ft^2/day, using NREL's numbers for Philadelphia, assuming a little more ground reflection. Size a low-thermal-mass sunspace to provide 100% of the heat for the house on an average December day, with some sun. There are several steps here: 4. Find how much heat your house needs on an average December day. If it needs, say, 200 Btu/hr/degree F, using "Ohm's law for heatflow," on an average 36 F day, it will need 24 hours (70-36) 200 = 163K Btu/day to stay at 70 F inside. 5. Find how much net heat a square foot of low-thermal-mass sunspace can gather on an average day where you live. Suppose the sunspace takes in 1000 Btu/ft^2/day with R1 single glazing. Then if we let the sunspace temperature rise to, say, 80 F during an average 6 hour December day, so it can provide warm air to heat the 70 F house, the loss will be about 6 hours (80-36)1 ft^2/R1 = 264 Btu, for a net gain of 736 Btu/ft^2/day. 6. Size the sunspace glazing. In this case, we need 163K Btu/day divided by 736 Btu/ft^2/day, ie 221 ft^2 of low-thermal-mass sunspace. This might be a lean-to sunspace 16' tall and 16' wide and 8' deep, made with 5, 20' long curved galvanized pipes on 4' centers, costing $35 each, with some clear mylar film costing 10 cents/ft^2 stretched over the pipes and a "foundation" consisting of railroad ties ("landscape timbers") spiked to the ground with 4' of rebar, with a floor made of black poly film covered with round pebbles. Or it might be an "expensive" sunspace made with $80 worth of 2x6s with some clear single layer polycarbonate plastic costing $1/ft^2, or one might just use the clear polycarbonate plastic instead of vinyl siding on the south side of the house, as "solar siding." 7. Size the thermal mass in a solar closet or pure attic warmstore to provide heat for the house for a week or so without sun. For 5 days, say, we need to store 163K Btu/day x 5 days = 815K Btu of heat. If we use 55 gallon drums full of water starting at 130 F, and cooling to 80 F over 5 days, each storing 25K Btu of heat, we need 815K/25K = 32 of them, each 3' tall by 2' in diameter, tucked away somewhere, receiving the sun thru an inner layer of glazing on the back wall of the sunspace, with some insulation behind that glazing to make a passive air heater. 8. Other options: add a water heater and 10' of fin tube pipe inside the solar closet or warmstore to make domestic hot water, using a little more glazing, or add a sauna, or a place to dry clothes... * * * There, that wasn't hard, was it? That's how to design an inexpensive 100% solar house, with no backup heating system, that also makes hot water, just like Norman Saunders has been doing since 1944... There are a few more little details to check, but this isn't rocket science, or even college physics. It's somewhere between figuring out a restaurant tip and doing a simple beam strength calcualtion, as architects know how to do. >Do you plan to use a Trombe wall, free-standing thermal mass, floor mass, etc? Ah yes, you might use a Trombe wall, invented by Felix Trombe in 1964 (and patented by Edward Morse of Salem, MA, in 1881) or a picture window in the living room, with a masonry floor in front of that... A "direct loss" house, like the one architect George F. Keck called a "solar house" in 1934 :-) A few years ago, I spent some time explaining to a local architect, a more technical person than most, who had taken a few engineering courses on the way to architecting, that a "Trombe wall" with some insulation on the outside and some passive plastic film dampers to the inside of the house, that opened up during the day, was probably a lot more efficient at collecting and keeping solar heat in the house than a plain old "traditional" Trombe wall, with masonry right behind the glass, with no insulation. Here's what I said: A "Trombe wall" with insulation on the outside, and 1 square foot of South- facing single-glazed area and an R-value of 20, will receive about 1000 Btu/day of heat on an average 32F December day, where I live. If the room behind it has a constant temp of 70F, and the sun shines 6 hours a day, on the average, the energy that leaks out of the glass will be about 6 hours x (70F-32F) x 1 ft^2/R1 = 228 Btu during the day, and 18 hours x (70-32) x 1 ft^2/R20 = 34 Btu at night, a net gain of 1000 -228 -34 = 738 Btu/day. Simple, no? (750 Btu, net, with double glazing, which passes less sun.) A standard unvented Trombe wall (Table IV-14b of Mazria's book says vented ones don't work much better) with a very large uninsulated thermal mass right behind the glass and an R-value of, say 2 (roughly 1' of masonry), would have an average temperature at the outside wall surface of about 32F + R1 x (70F-32F)/(R2+R1) = 45F, if there were no sun. If you add a heatflow of 1000 Btu/day of sun to that model, falling on the outside of the wall, the outside wall surface will have an average temperature of about 45F + 1000/24 x (R=2/3) = 72.4F, which contributes 24 hours x (72.4F- 70F) x 1 ft^2/R2 = 29 Btu/day to the room behind the wall. So the "improved Trombe wall" above, (actually an air heater with the thermal storage inside the house) is more than ***25 times*** as efficient (738/29) at collecting and keeping heat in the room behind it, than the usual Trombe wall. This is somewhat oversimplified, of course... And do you know what the architect said? "I agree with you completely, but if you do that, you will violate the integrity of the traditional Trombe wall, which has a magical, wonderful way of *flywheeling*, and transporting the heat through the wall, so it is available at the other side *precisely* when it is needed, the next morning!" And he went on and on about this conceptual delight, this conceit, completely ignoring numerical performance... :-) Trombe walls are also thermal disasters during long strings of cloudy days. When the sun goes in for a week or two, they lose their stored heat in less than a day, and then leak house heat badly, dramatically raising backup heat or other solar thermal storage requirements. I'm amazed that so many people, even in these newgroups, are still so interested in Trombe walls, or their passive solar equivalents, like direct gain houses or high-thermal mass sunspaces. A lot of people are apparently still willing to settle for high-cost, low-performance passive solar house heating techniques, that get them a 30% yearly savings in backup space heating costs over a 20 year payback period, vs. warmstores, solar closets, sunspaces and transparent siding, which really can save close to 100% of the space heating energy needed for a house AND provide close to 100% of the hot water needed for a house, as well. >You'll find water is far and away the highest-capacity, non-phase change >storage medium, in the form of freestanding tanks... Agreed. >How do you plan to provide for effective daylighting while preventing glare? How about skylights with reflective south-facing sunscoops over the top? Or a transparent steep south roof with some reflective motorized dampers in the insulated attic floor, or a bubble-ceiling? >I'm presently looking for windows that block UV radiation... You would want to look for windows made out of glass, or polycarbonate plastic with a UV light transmission of less than 1%... >but are not low-E (because of the amount of infrared radiation they block). You seem to be seriously confused, Will. For solar heating, blocking IR is GOOD, as is passing visible light... Window glass and polycarbonate plastic pass 85% of the solar radiation between 380 and 2,000 nanometers (the sun being like a 10,000 degree F black body) and block more than 98% of the IR re-radiation between 4,000 and 10,000 nanometers from an 80 F room. This "greenhouse effect" has been around long before ozone concerns. >UV will fade furniture Something fades furniture next to south-facing windows... Is it the visible light or the heat or the tiny amoutn of UV that gets through the glass? At any rate, an intelligently-designed solar home (not yours, apparently) will not have a lot of glass opening into the living space. >and increase skin cancer likelihood. I doubt you would ever get skin cancer with glass between you and the sun. >I am in the middle of a similar design effort myself, and a utilizing the >designs of a modular home manufacturer that has participated with DOE >on this subject (see Solar Today, Sept/Oct 1995). Kurt Smith at Avis? :-) He should know how to design better solar houses by now... DOE also sponsored the Passive Solar Industry Council Guidelines. Perhaps we should abolish them, if they continue to do more harm than good. >If anybody has any additional info, I'd be interested as well. I'm trying to help you... Nick Nicholson L. Pine System design and consulting Pine Associates, Ltd. (610) 489-0545 821 Collegeville Road Fax: (610) 489-7057 Collegeville, PA 19426 Email: nick@ece.vill.edu Computer simulation and modeling. High performance, low cost, residential solar heating and cogeneration system design. BSEE, MSEE. Senior Member, IEEE. Registered US Patent Agent. Fluent in French. Article 383 of pa.environment: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.architecture.alternative,alt.energy.renewable,sci.energy,sci.engr.heat-vent-ac,alt.solar.thermal,alt.home.repair,sci.environment Subject: Re: Seek Passive Solar Design FAQ/Guide Followup-To: misc.test Date: 9 May 1996 14:55:07 -0400 Organization: Villanova University Summary: another pie for your face? :-) William R Stewart wrote: >Nick Pine wrote: >> William R Stewart wrote: >> >... if you are considering passive solar as your main heat source. >> >The Passive Solar Industries Council has a complete book and software >> >program for this engineering problem. >> > >> > Passive Solar Industries Council >> > 1511 K St., #600 >> > Washington, DC 20005 >> > (202) 628-7400 >> >> Yeah, the brick people :-) Give them a call if you want to fill up your >> sunspace with thermal mass and cripple the performance, while raising >> the price dramatically :-) > >Thermal storage does not 'cripple' the performance of a sunspace, I disagree. This basic high school physics is now well-understood, being over 300 years old, invented by Newton and others. In rhetoric, an assertion demands no more than a counterassertion. I've gone beyond that already. You have my numbers. Where are your numbers, Will? >it simply evens out the temperature swings. That it does, but that's not all it does. It also stores lots of solar heat during the day, most of which radiates back out thru the sunspace glazing at night, since that is a poor insulator. Again, this is simple physics. >Brick is only one of several materials that can be utilized, >including even water. Less delightful for the brick people, no doubt :-) >> Or if you want your "main heat source" to >> provide less than half the heat for your house. > >You would have to provide the figures to support your assertion, I'm confused here, Will. Or perhaps you are. I said that there are a number of houses in the US that are 100% solar heated, with no backup heating systems at all, some of which have long track records, in cloudier, colder places than Philadelphia. I also said that if you carefully follow the orthodox PSIC "Passive Solar Design Strategies: Guidelines for Home Builders," you will end up with a house in the Philadelphia area that is no more than 41% solar heated (see the 13th line on the right hand side of the table on page 31 of those guidelines.) This PSIC target seems surprisingly low, given all these solar houses with no other form of heat. >...I have seen passive solar homes where solar provided in excess of >85% of the heating requirements. So have I. But they were not built using those rotten PSIC guidelines. >[199th repost of solar closet deleted] Perhaps you should read it and understand it once, Will, instead of just deleting it over and over... :-) >> Two views on sunspace design: >> >> It is hard to think of any other system that supplies so much heat >> (to an existing house) at such low cost... >> >> One could shorten the warm-up time of the enclosure and increase >> the amount of heat delivered to the rooms by making the enclosure >> virtually massless--by greatly reducing its dynamic thermal capacity. > >So that energy isn't stored for the evening and night hours? Correct. No heat lost via the sunspace at night, because the heat is stored elsewhere. This is Bill Shurcliff, PhD, physics, talking... >> This can be done by spreading a 2-inch-thick layer of lightweight >> insulation on the floor and north wall of the enclosure and then >> installing a thin black sheet over the insulation. Then, practically >> no heat is delivered to the massive components of floor or wall; >> practically all of the heat is promptly transferred to the air. >> And since the thermal capacity of the 100 or 200 lb. of air in >> the room is equal to that of one fourth as great a mass of water >> (about 25 to 50 lb. of water), the air will heat up very rapidly. >> I estimate that its temperature will rise about 40 F. degrees in about >> two minutes, after the sun comes out from behind a heavy cloud cover. >> At the end of the day, little heat will be "left on base" in the >> collector floor or north wall and, accordingly, the enclosure will >> cool off very rapidly. > >I fail to see the advantage of such a system; >what do you do for heat at night? A solar closet, an attic warmstore, a rock bin, massy house walls, an indoor pool, concrete furniture, a 5 year supply of Diet Coke, etc. >> A sunspace has extensive south-facing glass, so sufficient thermal mass >> is important. Without it, the sunspace is liable to be uncomfortably hot >> during the day, and too cold for plants or people at night. > >Just the opposite of what you state above. Right. I'm quoting the PSIC brick people here, not Bill Shurcliff, PhD, physics, Harvard prof and author of a dozen or so well-respected books on solar heating. Bill Shurcliff does not sell bricks :-) >> However, the temperature in the sunspace can vary more than in the >> house itself, so about three square feet of four inch thick thermal >> mass for each square foot of sunspace glazing should be adequate... > >How did you arrive at that size? I didn't. The brick and concrete people did. I found this pearl of wisdom on page 27 of my Philadelphia PSIC Guidelines. >And what material would you use for the thermal mass, as energy >capacities vary widely? I would use sealed containers of water myself, but I would not put them in a sunspace. I'd keep them somewhere inside the house, ideally above room temperature inside a solar closet, where they wouldn't lose all of their heat overnight or during a week without sun to the outside world thru the glazing, which is a good heat conductor. I'd let the sunspace itself get icy cold very quickly at night, so it loses little heat. >> The sunspace floor is a good location for thermal mass. The mass floors >> should be dark in color. > >Like brick? :-) Sure, if you sell bricks :-) >> No more than 15-25% of the floor slab should be >> covered with rugs or plants... Another good location for thermal mass >> is the common wall (the wall separating the sunspace from the rest of >> the house)... Water in various types of containers is another form of >> energy storage often used in sunspaces. > >Yes, a water wall is an effective thermal storage device. It is indeed, if it has insulation between itself and the outside world. >> So, which is the most energy-efficient sunspace in a partly cloudy climate >> like Philadelphia? >> Shurcliff's plastic film sunspace, wearing the green uniform in this >> contest, might cost about $1/ft^2, and on an average December day at 36 F, >> it would receive about 1000 Btu/ft^2 of sun, like the PSIC sunspace. Let's >> assume that both sunspaces have a perfectly insulated wall between them and >> the house, to avoid the thermal disaster of a poorly insulated Trombe wall >> in a partly cloudy climate, and let's assume there is no air infiltration >> from the outside in either case. > >Two major assumptions that are unacceptable in a real world situation, >especially the lack of air infiltration. OK, put in an imperfectly insulated wall, say R20, and some air infiltration, eg 2 air changes per hour. The results hardly change at all. Trust me, I know what I'm doing. I won't bore you with those details. >That would negate the benefits of an air storage attempt in a sunspace. Nobody's trying to store heat in air... (?) >> >Some of the variables involved in such a design include; >> >> >What is the heat loss rate of your structure? >> >> Yes, that's a good thing to know... "Ohm's law for heatflow"... Note glass >> is a very poor insulator... A 30 x 30' x 2 story house with R20 walls and >> ceiling might have a thermal conductance of 2000 ft^2/R20 = 100 Btu/hr-F. >> Make 10% of the wall area windows by adding 200 ft^2 of R2 glass and this >> doubles to 200 Btu/hr per degree F--unless the glass is in a thermally >> isolated sunspace, in which case the thermal conductance and heat loss >> of the house go down, not up... > >Try using R4 windows with window quilts for even more night insolation. R4 is poor, compared to a wall. And try using the word "insolation" for sun, and "insulation" for heatflow. And recall that people don't use manual movable insulation for long. They get tired of operating it. Nobody seems to have come up with good, simple, cheap, automatically-movable window insulation, after all these years. For one thing, it's not easy to seal the edges. >And the sunspace you refer to with mylar windows will have less than an >R1 rating, so energy retention in the sunspace, including air infiltration, >will be negligent. For starters, I guess you mean "negligible" instead of "negligent" (as in "The great American colonial composer William Billings was said to be 'a man of uncommon negligence,' since he spent a lot of time in the gutters of Portsmouth.") More substantively, air infiltration should be minimal in a sunspace made with a very large piece of plastic film, and I assume that by "energy retention" you mean something having to do with solar collection efficiency, not heat storage... I can't find very complete information about the thermal resistance of Mylar (polyester) film in my greenhouse engineering book, perhaps because it has not been used for a long time in greenhouses, but it does say that Mylar has an IR transmittance of 30%, vs 50% at the same temp for R0.8 polyethyene film, so it must be at least R0.8. So instead of a loss of 6 hr (80-36)1 ft^2/R1 = 264 Btu/ft^2 for a 74% solar collection efficiency of a single-layer glass sunspace in the Phildaelphia area, we might have a loss of 330 Btu/ft^2/day and a solar collection efficiency of 67%, so we would need a few more square feet of sunspace glazing. No big deal, at 10 cents/ft^2 (?) >> >What is the solar insolation in your area and when does it occur? >> >> Also good to know, eg the amount of sun that falls on a south wall on a >> December day, as well as the average temperature in December. If your >> house stores heat for several days, these averages are good enough for >> design. > >This is a little over-general, as passive solar mistakes >have borne out in the past. I disagree. I've posted some detailed computer simulations that prove this. Perhaps you would like me to email you a 262,980 line solar simulation for such a house using hourly NREL data for the last 30 years. >> >What are your backup systems (eg, masonry fireplace, ground-source >> >heat-pump, etc)? >> >> Ideally none. This is how some people define a "solar house," ie one with >> no other form of heat... Simple, no? Such a house can be easily designed >> with some high school physics and algebra, as licensed Professional Engineer >> Norman Saunders has been doing in cold, cloudy New England since 1944. > >Again, the specifics of the weather play an important role, because >if you have 6 days of cloudy or rainy weather in January, then you will >freeze without supplementary heating of some form. I don't think you will freeze, but you might have to put on a sweater every 35 years or so, the way Norman Saunders, PE, calculates these events, on a statistical basis, like 100 year floods... Of course one can never build a "100% solar house," as you say, because no matter how much thermal storage a house has, Mother Nature will eventually supply a string of cold cloudy days that exhaust it, and the house temp may dip to 67 or 66 F (horrors!) despite our best laid plans. My best laid plans might include a simple solar house simulation based on hourly local NREL/NOAA data for the last 30 years. It seems to me that most people would be happy over the next 30 years if their house would not have needed any backup heat for the last 30 years... >> Here's the scoop. The way to do this is simple. Start by finding 3 numbers: >> >> 1. Find the heat loss for your house, eg 200 Btu/hr per degree F. > >A fairly well-insulated house. True. And why not. As Steve Baer says, the greatest discovery of solar investigators has been that if you use lots and lots of insulation, a house will need very little heat, from the sun or any other source. However, insulation does cost money, and it doesn't make hot water. Perhaps future houses will have more glazing and thermal mass and less insulation. Perhaps not. Perhaps they will have backup heating systems, perhaps not. This is a matter of economics, inter alia. But, there will always be purists, sailors who like to sail boats without motors, and heroic natural homeowners... >> 2. Find the average temperature in December where you live, eg 36 F. >> 3. Find the average amount of sun that falls on a south wall in December >> where you live, eg 1000 Btu/ft^2/day, using NREL's numbers for >> Philadelphia, assuming a little more ground reflection. > >From http://solstice.crest.org/cgi-bin/solrad , we get 2.9 kWh/m2/day >for a vertical wall surface in Philedelphia in December. Fine. >Out of "Principles of Solar Engineering", Kreith/Kreider, we find for 40o >north latitude; Dec 21, we find 702 BTUH/ft2 for an ideal day, with no >overcast or other insolation impediment. That sounds more like an average day, not an ideal day, especially since you mention the latitude. Your 2.9 kWh/m^2/day NREL number (919 Btu/ft^2/day) with a built-in 0.2 ground reflectivity is probably more accurate for an average day... Either one can be improved with something more reflective lying on the ground in front, eg snow or ice with a 0.6 reflectivity. . >> Size a low-thermal-mass sunspace to provide 100% of the heat for the house >> on an average December day, with some sun. There are several steps here: >> 4. Find how much heat your house needs on an average December day. If it >> needs, say, 200 Btu/hr/degree F, using "Ohm's law for heatflow," on >> an average 36 F day, it will need 24 hours (70-36) 200 = 163K Btu/day >> to stay at 70 F inside. > >> 5. Find how much net heat a square foot of low-thermal-mass sunspace can >> gather on an average day where you live. Suppose the sunspace takes >> in 1000 Btu/ft^2/day with R1 single glazing. Then if we let the sunspace >> temperature rise to, say, 80 F during an average 6 hour December day, >> so it can provide warm air to heat the 70 F house, the loss will be about >> 6 hours (80-36)1 ft^2/R1 = 264 Btu, for a net gain of 736 Btu/ft^2/day. > >What is the surface area of the sunspace? I had in mind a fairly shallow sunspace, perhaps some south "solar siding." >It wouldn't be identical to the floor square footage, True. It would be quite a bit larger. Making a 16' tall x 12' long lean-to sunspace 8' deep instead of 8" deep adds another 128 ft^2 or so of endwall losses, so if the original sunspace were designed to collect (1000-264)x16x12' =141K Btu/day, the 8' deep one would want to collect enough sun with the south facing glazing area A so that (1000-264)A=128*264+141K Btu/day, making A about 238 ft^2, ie we might use a 16' x 16' sunspace. >I would estimate you would have roughly 3 times the surface area to floor >space ratio, at a minimum. Let's check that: (16x16'+128')/16x8' = 3. Exactly :-) >That makes an enormous difference in your calculations. No, this is just one of those little refinements I mentioned before. Using a deeper sunspace than solar siding requires a little more glazed area. >And don't forget air infiltration. OK, I won't forget that. Should we forget internal heat generation? >> There are a few more little details to check, but this isn't rocket science, >> or even college physics. > >You need to construct one, collect data, and provide empirical results. Like the one with the electronic data logger inside that has been up on the roof of the local college since November 4? No, I don't need to do that. >> ...you might use a Trombe wall, invented by Felix Trombe in 1964 (and >> patented by Edward Morse of Salem, MA, in 1881) or a picture window in the >> living room, with a masonry floor in front of that... A "direct loss" house, >> like the one architect George F. Keck called a "solar house" in 1934 :-) > >You are making specious claims. I disagree. Trombe walls are even poorer performers than sunspaces full of bricks, since they have little thermal resistance. At least you can put an insulated wall between your living space and your brick sunspace, so most of your backup heat stays in the house during a cloudy week. You have my numbers. Which number is incorrect? Where are your numbers? Most people don't even need numbers to see this. >Trombe wall effectiveness has been proven with empirical data. They work pretty well in the Southwest, in places with less than 5 cloudy days per year, but even there, people call these "direct loss houses" :-) In cloudier climates, they are thermal disasters. >>And the architect said, "I agree with you completely, but if you do that, >>you will violate the integrity of the traditional Trombe wall, which has >>a magical, wonderful way of *flywheeling*, and transporting the heat >>through the wall, so it is available at the other side *precisely* when >>it is needed, the next morning!" And he went on and on about this conceptual >>delight, this conceit, completely ignoring numerical performance... :-) > >Perhaps you should have listened to his argument for a change. I did listen... >> I'm amazed that so many people, even in these newgroups, are still so >> interested in Trombe walls, or their passive solar equivalents, like >> direct gain houses or high-thermal mass sunspaces. > >What you have described is a direct gain air collector with no thermal mass >for storage. Perhaps you didn't have time to read this carefully. >>A lot of people are apparently still willing to settle for high-cost, >>low-performance passive solar house heating techniques, that get them a >>30% yearly savings in backup space heating costs over a 20 year payback >>period, vs. warmstores, solar closets, sunspaces and transparent siding, >>which really can save close to 100% of the space heating energy needed for >>a house AND provide close to 100% of the hot water needed for a house... >You make these claims yet provide no empirical data to back them up. I have some data. Norman Sauders has lots of data, and many people with firmer grasps on simple high school physics can understand how well this works without building a thing. >>>How do you plan to provide for effective daylighting while preventing glare? >> >>How about skylights with reflective south-facing sunscoops over the top? > >What are the R-values? How many lumens do they provide? Perhaps you have heard people say "Asking questions is the mark of a fool"? :-) >What do you do when you have day lighting requirement in the basement >and 1st floor of a two-story building? I don't know. What do you do? Windows, transparent floors, light pipes, a walkout basement? >> >I'm presently looking for windows that block UV radiation... >> >but are not low-E (because of the amount of infrared radiation they block). >> >> You seem to be seriously confused, Will. For solar heating, blocking IR is >> GOOD, as is passing visible light... > >I don't want to block incoming infrared, which the low-E glazings do. It is nice to pass solar IR, from 0.78 - 3 microns. It is not nice to pass 80 F IR re-radiation at 3 microns and over... One way to do this is to use plain old glass in a low-thermal-mass sunspace. Another is to use inexpensive single layer polycarbonate glazing. Polyethylene film is not good at blocking either kind of IR. >> >UV will fade furniture >> Something fades furniture next to south-facing windows... Is it the visible >> light or the heat or the tiny amoutn of UV that gets through the glass? >> At any rate, an intelligently-designed solar home (not yours, apparently) >> will not have a lot of glass opening into the living space. >You imply that I am not intelligent... Let's just say that you don't seem to understand how to design an inexpensive, energy-efficient solar house, and you have been bamboozled by PSIC. That's OK. Ignorance is no crime, save when combined with arrogance, stupidity, rudeness, direspect, stubborness, short-sightedness and superficial orthodox thinking. Perhaps you should take up religion, or law. Still trying to help... Cheers, Nick Article 603 of alt.energy.renewable: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.energy,alt.architecture.alternative,alt.solar.thermal,bit.listserv.geodesic Subject: Re: Solar Heating, Empirical Measu(r)ements & Experience Date: 15 May 1996 13:01:12 -0400 Organization: Villanova University Summary: pretty long winded Keywords: sunspaces, bubblewalls, research, design, development William R Stewart wrote: >I would recommend talking to a number of different energy consultants. Me too. I usually start by asking "Are you familiar with Ohm's law?" That filters out more than half of the "energy consultants" I've met, but asking this question is sometimes embarrassing all around... Here's another litmus test for an energy expert: what will the average water temperature be inside a 4' cube full of water surrounded by 5 R20 foam walls, sitting outside in December, when the air has an average 24 hour temperature of 36 F and the sun puts 1,000 Btu/ft^2/day of heat into the R1 glazed side of the box? And how will that change over time if we shade the sunny wall? Anyone care to answer that question? I'll offer a $10 reward to the first person who answers it correctly. >Nick does have a lot of theories, though he considers many of his untried >pet theories to be far superior to anything anyone else has ever conceived. It's hard to know how to dissect that sentence :-) It looks like an insult. And untrue. Most of this stuff was conceived a long, long, long time ago. New weather data, new arrangements of systems and new materials and controls make it ever more practical and cost-effective and efficient now, but that isn't the main problem... Yes, I'm smarter than most people ("References please"--I belong to Mensa) and I know a lot more about physics, and I've thought a lot more and in more depth about solar heating and have more engineering degrees than many house designers, backyard crackpots and armchair a.e.r posters who like to talk about alt.energy but haven't done any at all, or PV hobbyists who have learned how to screw a system together but don't know Ohm's law either, and I do think _some_ of "my solar theories" are the cat's pajamas, especially the ones that seem to make sense with my simple understanding of physics, and the ones that really do work... the ones we've been trying out now in a 2' x 4' x 8' tall structure with an electronic data logger and modem inside, in the real Pennsylvania winter outdoors on the roof of the physics building at Ursinus college in Collegeville, PA since November 4... and physics prof Paul Bashus and I have managed to hornswoggle our solar theories on paper past the technical review committees of two international conferences in the last year, as well as a number of PhDs, who have accepted our solar closet paper for presentation at the Unesco-sponsored World Renewable Energy Congress in Denver from June 16-21 (Jessica_White@NREL.GOV--the registration fee increases from $340-740 after today, May 15), whose steering committee alone has people from 130 countries, and I've talked and run sessions on solar heating and cooling techniques at several US conferences, but. . . serious scientists and engineers consider solar closets and sunspaces "trivial physics" and "unoriginal research." Many scientists are out collecting funding to improve the solar collection efficiency of some system from 16 to 17% by adding another $10/ft^2 to the cost of something that already costs $30/ft^2. This kind of solar house heating technology has been around since Edward Morse invented the "Trombe Wall" in 1881, at least, and it's understood by many people who know what they are talking about, and a lot more who don't. Solar house heating just hasn't been done well yet, outside of the Southwest, on an significant scale, partly because the field is peopled by ignorant hucksters, partly because we are still waiting for the government to help make that happen... But this is lumberyard and hardware store science, not stuff for theses and Nobel prizes and NREL grants. It's waiting for bold entrepreneurs. And more expensive energy prices, or people who care more about the environment, or government regulations that make not caring more expensive... Many heating and cooling engineers are working on heating and cooling systems for skyscrapers, or heat pumps, where the money is today. I've only been doing this full-time for 2 years now, after 25 years of electrical engineering, and I'm still learning. Some things seem like good ideas on paper but really do have to be tried out, and improved somehow for some applications, or proved to be impractical for others, like bubblewalls. Some things don't need to be tested much, like low-thermal-mass sunspaces, and some things do, like bubblewalls. It's important to know the difference. Bubblewalls are the subject of an old Swedish patent (I wish I had a copy.) The original application was storefront windows. They have been tried in this country over the years by people like John Groh, a New York grower (?) and Dr. Merrill Jenson at U Arizona and Dr. Otho Wells at U New Hampshire, who concluded in 1977 that bubblewalls were not practical night insulation for commercial plastic film greenhouses simply because those greenhouses need to be put together so roughly and quickly in the field by unskilled people (so as not to raise their basic cost of 50 cents per square foot :-) that leaks in such a system could not be avoided. Everyday leaks in plumbing, plastic film connections, etc. These are real problems, and I don't mean to minimize them, but they are also application-specific, and not hard to solve. Dr. Wells says that windows in solar houses may be a different situation, since they can be made more carefully... He also says he only got a US R-value of 1.5 or so out of his 3"-6" thick poly film pillows, so it seems we need to improve the bubbles themselves somehow, make them smaller and longer lasting, with thicker walls perhaps, or go work on something else. Dr. Aristid V. Gross of Temple U and the blind Belgian physicist Joseph Plateau (1801-1883) both made bubbles that lasted over a year... Dr. Wells was using an open system, more dustprone than a closed one, making bubbles at the top of a 25' x 196' double poly film greenhouse to fill the double poly film walls all round. He put slits in the plastic film, some with sewn-in zippers (he said sewing zippers into poly film isn't easy), to let some air out at the endwalls. He found he had to make more bubbles every 2-4 hours, to keep the walls full of bubbles. Dr. Jenson experimented with a photosensor to do this automatically, and also tried adding dyes to the bubble solution, which were diluted so much in bubble from that they had little effect. Another way to keep the glazing cavities full is to keep a layer of bubbles moving slowly from bottom to top in a continuous fashion. Another is to use temperature sensors to measure the R-value. Dr. Wells said the small bubbles tended to settle out quickly and become liquid again at the bottom... Another problem: Dr. Wells mentions that the bubble distribution was not uniform--big bubbles and open spots, thermal shunts with no bubbles, up to 1-2' in diameter would often develop. This might happen less if bubbles move continuously up from the bottom instead of intermittently down from the top of the cavity. Dr. Wells used a basic solution of 3% type E dust reduction foam (a better choice might have been firefighting foam) from Mine Safety Supply in Pittsburgh (now Mine Safety Appliances at (412) 776-7700?) with 1% propylene glycol as antifreeze, because when the bubbles freeze inside the outside layer of poly film, they break, and the R-value goes down and their friction against passing bubbles goes up, and he didn't want water frozen in pipes either. Can we make frozen bubbles that don't break? Yes. That's been done, often, in public at the San Francisco Exploratorium by Dr. Ilan Chabay, called "one of the world's foremost authorities on frozen bubbles," in John Cassidy's _Unbelievable Bubble Book_ for children (Klutz Press, 1987.) Has Dr. Wells ever talked with Dr. Chabray or Dr. Grosse? I don't think any physicist would call bubbles trivial physics. Child's play maybe, but not trivial :-) We need more child-like physicists. There is at lot of work to do in this alt.energy field, and a lot of it, like preventing leaks or finding the right soapy solution is not that technically difficult. There isn't a lot of funding, but there's a lot of work to do, a lot of opportunity for serious backyard builders and high school science fair students to do interesting things that may later become good, cost-effective, reliable, simple socially-useful techniques and products, given some common sense and education and patience and a lack of greed and shortsightedness. Some things need to be tested and developed a lot, others are no-brainers, if we start thinking from scratch. Not everyone wants to live in an experimental bubblewall house, but lots of people like sunspaces. There's a huge gap between commercial plastic film greenhouses costing for 50 cents per square foot and residential sunspaces costing $50-150 per square foot. Who will fill it? NREL? No... There's another gap between serious scientists who say all this is trivial well-understood physics, while they collect their salaries working on more and more exotic research, and alt.energy.renewable experts who say it won't work, it's been tried before, Trombe walls are the cat's pajamas, etc, etc. Bullshit! >I would have to say that distributing the energy evenly to where it is >desired is yet the most important half. Many houses have been built >where some rooms overheated while others grew cold. Distributing the >heat to zones at specific times during the day is an interesting challenge. Sure, that's important, but let's collect the heat to begin with, Will, and then worry about that problem. Or wear a sweater in one room and take it off in another. That's HVAC. Air pushers, ducts and fans and blowers and zone controls, to move warm air out of our sunspace or solar closet around the house. Not too hard in a new house, and harder in a retrofit, unless we can mix the warm air into a big room or dump it into a return grate somewhere, somehow. That's a lot better understood than solar heating. Straightforward everyday cranking, for someone who knows how to do it. Nick It's a snap to save energy in this country. As soon as more people become involved in the basic math of heat transfer and get a gut-level, as well as intellectual, grasp on how a house works, solution after solution will appear. Tom Smith Article 51820 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,alt.architecture.alternative, alt.solar.thermal,bit.listserv.geodesic,sci.engr.heat-vent-ac Subject: Re: R-value conversions (was: Solar Heating, Empirical Measu(r)ements & Experience) Date: 16 May 1996 04:52:30 -0400 Organization: Villanova University David Hoadley wrote: >nick@vu-vlsi.ee.vill.edu (Nick Pine) writes: Here's another litmus test for an energy expert: what will the average water temperature be inside a 4' cube full of water surrounded by 5 R20 foam walls, sitting outside in December, when the air has an average 24 hour temperature of 36 F and the sun puts 1,000 Btu/ft^2/day of heat into the R1 glazed side of the box? And how will that change over time if we shade the sunny wall? Anyone care to answer that question? I'll offer a $10 reward to the first person who answers it correctly. Still no numerical answers, 16 hours after this posting. Perhaps $10 is insufficient bait to catch an energy consultant, or they are out of season? Or perhaps it should be rephrased in international units: Here's another litmus test for an energy expert: what will the average water temperature be inside a 1 m cube full of water surrounded by 5 R5 foam walls, sitting outside in December, when the air has an average 24 hour temperature of 2 C and the sun puts 3 kWh/m^2 per day of heat into the R0.175 glazed side of the box? And how will that change over time if we shade the sunny wall? Anyone care to answer that question? I'll offer a $10 reward to the first person who answers it correctly. >This brings me to another point (thus the change of topic title). When I >first started reading these groups I was rather taken aback by the high >R-values people mention. Here in Australia, they are generally in the >range R-1.5 to R-3 or 4 for (say) fibreglass insulation. R30 house walls are pretty good walls in the US. Perhaps a good new Australian or French or British house has R5 walls, made with straw bales and mortar, 40 cm thick? A 1 bale wall? >The units are, naturally, degC.m^2/W. Of course Mother Nature thinks in meters and C, not feet and F :-) The natural thing about a Btu (the amount of energy in a kitchen match) is that it takes eggsactly 1 to raise 1 pound of water or 55 ft^3 of air 1 degree F. It takes about 100 Btus to make a cup of coffee. Chickens make about 5 Btu/hr/lb of sensible heat. A typical 5.41 lb bunny makes 40. 1 cfm of air flowing with a temperature difference of 1 F moves about 1 Btu/hour, a single pane window is about R1, and 2 layers are R2. A pound of water takes 144 (1 gross) Btus to freeze at 32 F, which is close to the average air temperature in December where I live, and it takes about 1000 Btu to boil away a pound of water at 212 F. A south wall in December receives about 1,000 Btu/ft^2/day of sun where I live, 300 Btu/hour/ft^2 peak. The thermal conductance of an airfilm with air moving at V mph is about 2 + V/2 Btu/hr-ft^2-F for rough surfaces. A black body at T degrees F radiates 0.174x 10^-8(460+T)^4 Btu/hr-ft^2. US hardware stores sell rolls of 6" fiberglass insulation stamped R19 in big letters (R10 with 2% moisture, R0 in a good wind) for 25 cents/ft^2, and R10 foamboard 2" thick costs about 50 cents/ft^2. What is natural in metric? Water freezes at 0 C and boils at 100 C, and it takes about 1 kWh to heat 1 m^3 of water or 3,000 m^3 of air 1 C. A cup of coffee takes about 30 Watt-hours. People make about 100 Watts, rabbits 5 W/kg. 1 m^3/sec of air flowing with a temperature difference of 1 C moves about 1 kW of heat. It's a little harder to remember that 1 layer of glass with an airspace has metric R0.175, and 2 layers have R0.35. It takes about 100 kWh to freeze a cubic meter of water and 663 kWh to evaporate one. The ratio of evaporative to convective power loss at a wet surface with temperature Tp in Ta air is about (Tp-Ta)/(Pwp-Pa)/2, independent of windspeed, where Pwp and Pa are vapor pressures in mm Hg. A south facing wall in December receives about 3 kWh/m^2/day of sun where I live, with a peak of 1 kW/m^2, and the thermal conductance of an airfilm with air moving at V m/s is about 10 + 2V W/m^2-C for rough surfaces, eg 100 W/m^2 in a 5 m/s wind for a 25 C surface on a 20 C night. How much more if the surface is wet, and the air has 50% RH? How much more if the sky is clear? Do French hardware stores sell R2 foamboard 5 cm thick for about about 30 FF/m^2? Why does the Lord permit such Suffering on Earth, if He is Omnipotent? >I was surprised to find that American ones are expressed in British Thermal >Units (which I had thought went out with the ark)... Now that Britain and Australia use Watts and meters, we are thinking of calling these American thermal units, or perhaps Bunny thermal units. >So I tried to work out a conversion factor. Can someone confirm it for me? > > Is it true that 1 watt = 3.412 BTU/hr? If so, have I got it right that > R-1 (International) degC.m^2/W = R-5.678 (US) degF.hr.ft^2/BTU? I think so. Or would those be degrees K, in that particular alphabetical procession? Nick When we play tennis or walk downstairs we are actually solving whole pages of differential equations, quickly, easily and without thinking about it, using the analogue computer which we keep in our minds. What we find difficult about mathematics is the formal, symbolic presentation of the subject by pedagogues with a taste for dogma, sadism and incomprehensible squiggles. From _Structures: Why Things Don't Fall Down_, by J. E. Gordon Article 51829 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.solar.thermal,alt.energy.renewable, alt.architecture.alternative,bit.listserv.geodesic, sci.engr.heat-vent-ac Subject: "Energy consultants" Date: 16 May 1996 10:34:14 -0400 Organization: Villanova University Summary: Ohm vs. Ommmm, or redesigning direct loss houses Keywords: long again William R Stewart wrote: >Nick Pine wrote: >> William R Stewart wrote: >> >> ...I usually start by asking "Are you familiar with Ohm's law?" >> That filters out more than half of the "energy consultants" I've met, >> but asking this question is sometimes embarrassing all around... > >Because that is an electrical term, as opposed to a thermodynamic term. Many people learn Ohm's law in high school, Will... I think an energy expert should be familiar with Ohm's law. To far too many people these days, "energy" = "electrical energy." >Appropriate if you are talking to a PV consultant, but confusing otherwise. Yes, Ohm's law is confusing to certain "energy consultants" :-) >You are simply trying to make other people translate your way of thinking as >an EE. Why not speak in thermodynamic terms, like the rest of the industry? Perhaps we should ask 'em about enthalpy? :-) >>Here's another litmus test for an energy expert: what will the average water >>temperature be inside a 4' cube full of water surrounded by 5 R20 foam walls, >>sitting outside in December, when the air has an average 24 hour temperature >>of 36 F and the sun puts 1,000 Btu/ft^2/day of heat into the R1 glazed side >>of the box? And how will that change over time if we shade the sunny wall? >>Anyone care to answer that question? I'll offer a $10 reward to the first >>person who answers it correctly. > >You don't give enough data in order to answer your question, and your question >is not clearly stated. I think there is too much data above, and the question is reasonably clear. >However, for the sake of fun, I'll make some assumptions. Good :-) This is the first numerical answer I've seen... >Assumptions; >1. The water starts out at 36oF. >2. Thermal conduction is the only heat transfer mechanism, aside from >the energy provided by the sun. Good. Although R-values include convection and radiation. >3. There are no losses incurred by the R1 glazing on the 1000 Btu/ft^2/day. The glazing is perfectly transparent? Fine. >4. There are no data points for how much energy is provided on an hour-by-hour >basis, so I will assume an even amount of sun over a 10 hour period. OK. (I don't think that matters here, but...) >Weight of water: >Let's just call it 4000 lbs. OK. >Thermal resistance of cube: >4x4 = 16 ft^2/side value of R1 area >16x5 = 80 ft^2 of R20 surface >R1 total = 1/16 = 0.0625 >R20 total = 1/4 = 0.25 >R total = 0.0625 x 0.25/(0.0625 + 0.25) = 0.05 >U = 1/0.05 =20 Btu/hr-oF Excellent! >Thermal energy input > >1000 Btus/day-ft^2 * 16 ft^2 / 10 hrs/day input > = 1600 Btus/hr while the sun is shining. Um, OK... >The water in the cube would rise to a steady state temperature of >36 +80 = 116 oF if the energy input were continuous. Perhaps, but recall the problem: >>the sun puts 1,000 Btu/ft^2/day of heat into the R1 glazed side of the box. >>And how will that change over time if we shade the sunny wall? >When shaded, the water in the cube would fall over time to 36oF. Well, yes... >A complete answer with specific times would require calculus, if specific >times was what you were looking for. Yes, that was what I was looking for. More than the obvious... Finding the form of the answer requires calculus, but Newton did that once, a long long time ago. Finding the answer just requires plugging some numbers into a simple formula, if you know the formula. >Approximations could be made, but the answer would not be 'correct'. Approximations using arithmetic would be fine... That's easy to do. >Let's just approximate the time it takes the water to rise 1 oF without >considering the negligible loss through the cube walls. OK (?) >4000 lbs of water would require 2.5 hours of 1600 btu/hr energy input, again >without considering the loss through the cube walls. True, but why are you talking about heating rather than cooling? * * * Sorry. No $10. Would you like to try again? * * * At this point, Mr Stewart changes the subject: >Now, if you; > -moved the water inside to the interior sunspace of a 68oF house, > -made the glazing 7'x10 (4 in the entire house on the south side) ie 280 ft^2 of south glazing? > -used a flatter 4"x4'x10' water wall (4 in the entire house), 4" away > from the glazing inside the house, ie about 400 pounds of water? 4" away from the glazing? Transparent water? Hmmm :-) I guess you won't be able to see very clearly out of those windows, but they will let in some light... > -used an R4 glazing when the sun was shining, With how much solar transmittance, at what cost, and what happens when the argon leaks out? Some of these $40/ft^2 high-R windows have low solar transmittance, on the order of 50%. Hmmm, 280 ft^2 x $40/ft^2 = $11,200. > and an extra R8 window cover when the sun wasn't shining, How would you do that? Movable insulation, at $10/ft^2, installed? Will you move it twice a day religiously? Will it leak any air around the edges? >then you would have a direct, passive solar design that retained the sun's >heat energy in the building interior and released it slowly into the >interior at night Right. Another "direct loss" house :-) >Care to try the math? Sure. I like this arithmetic. Let me get a cup of coffee... Now I'm back, 200 Btu later. I've had this espresso machine for about 3 months now. I guess if some people like me find it fun to wiggle the valves on an espresso machine with all the steam and noise and watch the milk temp rise with a thermometer twice a day, others might find it fun to move window insulation all over a house twice a day, for three months... Or, maybe you only move the window insulation on a cloudy winter day--but no, you want to do it at night too... or you might leave some windows covered all winter, like Pat Hennin or Malcolm Wells, in semi-hibernation, huddled in cold dark rooms. >assume another 60 ft^2 of window at R4 during the day, adding > another R8 at the other 14 hours. OK. That's a long winter day... >Assume R24 walls and R38 ceiling. OK. Let's assume that includes the 2x6's, etc, that act as thermal shunts, ie the equivalent thermal resistance of the entire wall is R24. This is not just a wall with layers of insulation with R-values that add up to R24 (which might have a much lower R-value), and the insulation is installed properly with no gaps, etc. Are you sure about all that? >Assume a two story, 24'x 48' floorspace house with 8' ceilings. OK. I guess you mean the footprint on the ground is 24 x 48? So the house volume is 24 x 48 x 16 = 18432 ft^3. >Assume an outside temperature of 36 oF OK. (The average will be warmer during daylight, which is good.) >Assume 0.25 air changes per hour (optional). OK. That's 0.25 x 18432 ft^3/hr = 4608 ft^3/hr or 77 cfm :-) I'll assume (I almost said "guess") this is leakage thru walls, etc, without an air-air heat exchanger... Will the finished house have a blower door testing spec? May we also assume you use a frugal 500 kWh/month of electricity, ie an average of about 700 Watts? (Steve Baer only uses 80 kWh/mo :-) This is equivalent to 700 x 3.41 = 2387 Btu/hr. Let's add the heat from two 300 Btu/hr people inside the house for 16 hours a day, and one 150 Btu/hr dog and a 50 Btu/hour cat, full-time. Total internal energy generation: 2387(24)+600(16)+200(24) = 72K/day. >Assume 100 Btu/hr/ft^2 insolation over 10 hours every day. OK. >Make an assumption about the thermal storage of the rest of the interior >items/material. How about 1 lb of water/ft^2 of walls and ceiling? (1/2" drywall has the equivalent of 1/2 lb of water/ft^2, so you may need some concrete furniture..) I'll make some other assumptions, too. I guess we'd want to know the thermal resistance of this house for starters. So let's add up the thermal conductances U = Sum(Ai/Ri) and find the reciprocal 1/U... We have 340 ft^2 of windows, R4 during a 10 hour day (Uday = 340/4 = 85) and R8 during a 14 hour night (Unight = 340/8 = 43), with an average daily Uwindow = (10xUday+14xUnight)/24 = 60. Uwalls = (2(24+48)x16-340)/R24 = 82, and Uceiling = 24x48/R38 = 30. And Uinf = 77 Btu/hr-F. So U = 60+30+77 = 167 Btu/hr-F and R = 0.006, over 24 hours. At night the U value would be lower, after you devotedly travel around the house and painstakingly put up your night insulation on every window, making sure the edges are ever so carefully sealed, akin to some little twice-daily religious experience... Unight = 43+30+77 = 150 Btu/hr-F. What will the steady state energy flow be for this house after a long string of average December days, with an average amount of sun? The energy Ein that flows into this house in a day might be 280 ft^2 windows x 50% transmission x 1000 Btu/ft^2/day = 140K + internal energy generation = 72K total Ein = 212K. And the energy Eout that flows out of the house might be 24 hours x (68-36) x 167 = 128 K Btu/day. So, after a long string of perfectly average December days, Ein-Eout = 84K Btu/day, if you keep the house at an average of 68 F during the day... This might make a fine New Mexico house. If you let the house temperature float over this time, you might have an average house temp T such that 24 (T-36) 167 = 212K, or T = 89 F. Colder at night, warmer during the day. Very toasty. Now, thermal mass: the house has about 3500 ft^2 of walls and ceilings with a thermal mass equivalent to 3,500 pounds of water and another 400 pounds of actual water. Let's call this 4,000 Btu/hr-F. So if you make the temp of the house, say, 80 F at dusk, at the end of an average day, with some sun, after a long string of December days, each with 1000 Btu/ft^2/day of sun, during the night the house will lose approximately 14 hours (80-36) 150 = 100K Btu, which might come from the 4,000 Btu/F of thermal mass cooling plus 14/24 hours x 72K = 42K of internal energy generation, ie the temperature of the house might drop to 80 - (100K-42K)/4K = 65 F at dawn. So yes, this 56%-electrically-heated house with all of the movable window insulation looks marginally comfortable after a long string of average winter December days, each with an average amount of sun. But what do you do if the next day is cloudy, or the day after that, or during a cloudy week in January, when the temperature outside is -10 F? You will have to use backup heat... Or, gasp, wear a sweater. With no sun and no backup heat, and with all the windows boarded up on the inside, 24 hours a day, just using the internal electrical energy consumption (and the people and livestock) after a day or so, Ein = 72K Btu/day and Eout = 24(T-36) 150 ==> T = 56 F inside. Not bad. Quite warm by Inuit standards. More dogs and cats would help. How much backup heat will you need in an average year? One way to answer that question is to go find some TMY2 data somewhere on the web (references, please :-) for a Typical Meteorological Year for this house location, and do a very simple simulation using that data and formulas like the ones above. Another is to do the same thing in more of a worst-case manner, ie more reliably using hourly data for the last 30 years from an NREL/NOAA CD-ROM. Then one might change the design until it is a "solar house," in the sense that it would not have needed any other form of heat over the last 30 years, according to the simulation, at which point, many people would opt to eliminate the backup heating system, saving some space and money... Here's an alternative design to try out in that simulation: Eliminate half the south windows and all the movable window insulation, to eliminate the daily labor and lower the price by $10K or so and lower the overall U value to about 140 Btu/hr-F, and make a little more privacy if that matters, and add on a 2-story, $5000, 16' wide x 8' deep lean-to sunspace with an 10' tall x 13' long x 5' deep solar closet containing 36 55 gallon drums, inside the sunspace, south of the house and adjoining the house wall. Each square foot of sunspace would supply about 1000 Btu - 6hr (80-36)/R1 = 700 Btu/day of heat for the house, ie about 180K of heat, vs the 120K-72K = 48K/day the improved house would require on an average day, via a $200 motorized damper at the top of the sunspace that uses 2 Watts of electrical energy when moving (rarely) and 0 watts (mostly) in a fixed position to let warm air flow into the house as needed, controlled by two thermostats. The solar closet would contain about 18,000 Btu/F of thermal mass, vs. 4,000 Btu/F, to keep the house at whatever temperature _you_ wanted, independent of weather, overnight, or on a cloudy day. Assuming the water starts out at 130 F after a long string of December days, with some sun, the solar closet would store about 25K Btu of heat in each drum, enough to keep the house at 68 F for about 25Kx36/48K = 19 days without any sun at 36 F, or 3.3 days without any sun at -10 F. We might improve that by making the solar closet bigger. After 3 or 4 days without sun at -10 F, with all the windows boarded up on the inside, and no backup heat, how can we estimate the temperature T inside the house we started with, before the improvements? 24(T-(-10))150 = 72K, so T = -10 + 72K/(24x150) = -10 + 20 = 10 F. It might take longer than 3 or 4 days to get to that temp, since the pipes and water walls would release about 400,000 Btu while freezing at 32 F, as the house temperature plunged. On the other hand, the people might move out sooner, depriving the house of their heat... Were you planning to have hot water in this house? How were you planning to do that? You might put a water heater on the second floor with some Big Fins in the sunspace or 10-20' of fin-tube pipe near the ceiling of the solar closet (less expensive), with a warm water thermosyphon loop through the water heater, to supply a frugal hot water house load of 50K Btu/day... About heat distribution... >> ...wear a sweater in one room and take it off in another? > >I try to look at the whole picture. A solar closet might gather the energy, >but distributing it is another matter altogether. > >>That's HVAC. Air pushers, ducts and fans and blowers and zone controls, >>to move warm air out of our sunspace or solar closet around the house. > >You now no longer have a passive system, but now require temperature >regulation, ducting, electrical loads, etc. One might compare this to an oil fired hot air furnace that uses 800 watts of electrical power when running, while consuming 38 kW (1 gph) of oil power and delivering 35 kW to the house. That's a fossil COP of 44. Some old and inefficient and expensive active solar systems have renewable COPs of 50. For instance, CSI's air/rockbed system in New Hampshire, built in 1982, uses "2% fan power, 98% solar power." A better way to compare heating systems might be their yearly heating bills, including the electrical power to run the heating system. I think one can build a solar house that consumes no more than 50 watts average, for the heating system, with no backup heating fuel, and no backup heating system. A 560 cfm fan ("References please"--Dayton fan 4C688, page 2964, Grainger catalog 386, 1650 rpm, 10" diameter, max temp rating 149F, $60.75) moving air from a solar closet into a house with 0.05" static pressure (as measured in our experimental structure) can move about 5600 Btu/hr into this house with a temp difference of 10 F, ie 134K Btu/day, while dissipating at most 36 Watts of electrical power. >Some people prefer the passive method, and it is not your perogative >to tell them that they are wrong in preferring that. Oh sure it is, and it seems kind to tell people, if their passive houses are such miserable and expensive performers. And as Newton Ellison and others say, this passive/active dichotomy isn't very useful. I'd say what matters more these days is money, comfort, reliability, cost and maintenance. Sailboats are passive devices using powerful natural forces and often smart low-power controls. Their captains care a lot about cost and performance... Would you hang an outboard motor on your America's Cup boat? Nick Article 620 of alt.energy.renewable: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,alt.solar.thermal,sci.energy Subject: Re: Passive solar heating for pool? Date: 16 May 1996 11:59:59 -0400 Organization: Villanova University Lines: 44 Message-ID: <4nfjdv$g2q@vu-vlsi.ee.vill.edu> References: NNTP-Posting-Host: vu-vlsi.ee.vill.edu Keywords: solar heating swimming pool Xref: news.ee.vill.edu alt.energy.renewable:620 alt.solar.thermal:140 sci.energy:51834 Shane Peterson wrote: >I have a friend who is looking for information on passive solar >heating designs for a kid's swimming pool. Sounds interesting... Solar pool heating should be very easy, with low water temps and all that built-in storage... >Specifics: Pool size is about 3700gal eg 462 ft^3 of water in a circular pool, 3' deep, 14' diam, 154 ft^2 cover? > Location is western Washington near Olympia SP (sun power) Daily air temperature Pool temp Hmmm. Jan 450 Btu/ft^2/day 38 F average 44 F max 83 F Feb 640 ( > of vert, 41 F 50 F 94 F Mar 880 horizontal) 44 F 54 F 105 F Oct 810 50 F 61 F 131 F Nov 490 43 F 50 F 92 F Dec 390 38 F 44 F 77 F > Cost should be kept low, construction of > heating panel would be done by the owners. The main thing is to have a good cover. Suppose it's R10 foil-faced foam, 2" thick, 16 x 16, hinged along the north edge, with a counterweight, and you have R10 foamboard around the perimeter, and you use an R1 floating transparent cover and open and close the rigid reflective cover every day when the sun is shining, except in October... Air temp Ta and water temp Tw make a daily heat loss Eout of roughly 6 hr (Tw-Ta) 154/R1 cover open + 18 hr (Tw-Ta) 154/R10 cover closed + 24 hr (Tw-Ta) 132/R10 sides = (924+277+317)(Tw-Ta) = =1518(Tw-Ta) = 154 SP = Ein ==> Tw ~= Ta + SP/10 (see table above.) Nick Article 51888 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.solar.thermal,alt.energy.renewable,alt.architecture.alternative,bit.listserv.geodesic,sci.engr.heat-vent-ac Subject: Re: Sample solar problems Date: 17 May 1996 09:59:02 -0400 Organization: Villanova University William R Stewart wrote: >Nick Pine wrote: >> William R Stewart wrote: >> >Nick Pine wrote: >>Here's another litmus test for an energy expert: what will the average water >>temperature be inside a 4' cube full of water surrounded by 5 R20 foam walls, >>sitting outside in December, when the air has an average 24 hour temperature >>of 36 F and the sun puts 1,000 Btu/ft^2/day of heat into the R1 glazed side >>of the box? And how will that change over time if we shade the sunny wall? >>Anyone care to answer that question? I'll offer a $10 reward to the first >>person who answers it correctly. By the way, I have only seen 3 numerical answers to this simple question so far. Two people got part 1 correct, and one has almost solved part 2 using simple arithmetic, but there's still a chance for the right person to earn $10 in 2 minutes with a couple of back of the envelope calculations... This might also be a rare opportunity for someone else to get paid to learn. Paul Erdos used to do this sort of thing with much harder math problems. He would offer a $100 prize for the solution to some long-standing research problem, and some grad student who might already be interested in the problem would get more interested and work for 3 months, day and night, and solve the problem, and pocket the money, and publish a paper, and feel very happy, and the science of mathematics would be advanced :-) Erdos offered different rewards for different problems, depending on how difficult they were, from $10 problems that took a few weeks to $1,000 problems that might take 10 years to solve, or might take a lifetime... >> >The water in the cube would rise to a steady state temperature of >> >36 +80 = 116 oF if the energy input were continuous. >> Perhaps, but recall the problem: >>>>the sun puts 1,000 Btu/ft^2/day of heat into the glazed side of the box. >>>>And how will that change over time if we shade the sunny wall? >>>When shaded, the water in the cube would fall over time to 36oF. >I showed how it would change over time. You owe me ten bucks, Nick :-) Nope. That answer is insufficient and superficial. I'm the judge. >> >A complete answer with specific times would require calculus, if specific >> >times was what you were looking for. >Otherwise, simple arithmetic would give the wrong answer, as this is obviously >not a linear relationship. >> Yes, that was what I was looking for. More than the obvious... Finding the >> form of the answer requires calculus, but Newton did that once, a long long >> time ago. Finding the answer just requires plugging some numbers into a >> simple formula, if you know the formula. >Present the formula and we will see if it produces the correct answer, or even >a very close answer. Nice try :-) How will "we" know that? The formula IS most of the answer... Or an approximate arithmetic equivalent... >>>4000 lbs of water would require 2.5 hours of 1600 btu/hr energy input, again >>>without considering the loss through the cube walls. >So here is an answer with a specific time; what's your beef? It has nothing to do with the problem. >> At this point, Mr Stewart changes the subject: >> >Now, if you; >> > -moved the water inside to the interior sunspace of a 68oF house, >> > -made the glazing 7'x10 (4 in the entire house on the south side) >> ie 280 ft^2 of south glazing? >> > -used a flatter 4"x4'x10' water wall (4 in the entire house), 4" away >> > from the glazing inside the house, >> ie about 400 pounds of water? 4" away from the glazing? Transparent >> water? Hmmm :-) I guess you won't be able to see very clearly out of >> those windows, but they will let in some light... >> > -used an R4 glazing when the sun was shining, >> With how much solar transmittance, at what cost, and what happens when the >> argon leaks out? Some of these $40/ft^2 high-R windows have low solar >> transmittance, on the order of 50%. Hmmm, 280 ft^2 x $40/ft^2 = $11,200. >You must be thinking of R8 windows; Where do you get your figures? I don't remember. Anderson, Pella? Popular Science? Perhaps that's R8. What brand of windows will you be using and how much do they cost? >I'm not going with low-E due to insolation losses. Good. I wonder what happened to your UV concerns. >> > and an extra R8 window cover when the sun wasn't shining, >> How would you do that? Movable insulation, at $10/ft^2, installed? >Again, where do you get your prices? The Shelter Institute. What will you pay? References, please. >>Will you move it twice a day religiously? >Just like you close your windows when it gets to cool at night. I hardly ever touch my windows. >>Will it leak any air around the edges? >Probably, but certainly much less than an outdoor thin film sunspace. I don't think so, if the sunspace is made from a continuous single piece of plastic film, 16 x 20'. And sunspace leakiness only matters 6 hours a day. >> >then you would have a direct, passive solar design that retained the sun's >> >heat energy in the building interior and released it slowly into the >> >interior at night >> Right. Another "direct loss" house :-) >Er, do you have a house that does not lose heat when it is cold outside? No. But this is a numerical thing, and the less the better at night, and direct gain houses leak lots of heat to the outdoors at night and during a week without sun thru their low thermal resistance glazing between the living area and the outdoors. >> >Care to try the math? >> Sure. I like this arithmetic. Let me get a cup of coffee... Now I'm back, >> 200 Btu later. I've had this espresso machine for about 3 months now. I >> guess if some people like me find it fun to wiggle the valves on an espresso >> machine with all the steam and noise and watch the milk temp rise with a >> thermometer twice a day, others might find it fun to move window insulation >> all over a house twice a day, for three months... Or, maybe you only move >> the window insulation on a cloudy winter day--but no, you want to do it at >> night too... or you might leave some windows covered all winter, like Pat >> Hennin or Malcolm Wells, in semi-hibernation, huddled in cold dark rooms. >> >assume another 60 ft^2 of window at R4 during the day, adding >> > another R8 at the other 14 hours. >You forgot to add R8, you only added R4 Oops. Would you describe this R8 window insulation, Will? Who makes it, how much the material costs, how much installation costs, what the materials are, how it is operated, and how the edge air leaks affect the R8 rating? >> >Assume 0.25 air changes per hour (optional). >> OK. That's 0.25 x 18432 ft^3/hr = 4608 ft^3/hr or 77 cfm :-) I'll assume >> (I almost said "guess") this is leakage thru walls, etc, without an air-air >> heat exchanger... Will the finished house have a blower door testing spec? >Yes, and the top limit will be 0.25 air changes; I expect alot less. Will the house be pressure tested when finished and guaranteed to have less than 5 ACH at 50 Pascals, consistent with natural air infiltration of < 0.25 ACH, using the usual rule of dividing the pressure test spec by 20? The best Avis homes informally tested by Penn State, as I recall from a go-around with Kurt Smith, Lyle Rawlings and Marc Rosenbaum, came out at 2.9 ACH at 50 Pa. >> May we also assume you use a frugal 500 kWh/month of electricity, ie an >> average of about 700 Watts? >Why does this matter? I will be using a 2kW photovoltaic system. Marc points out that many superinsulated houses are more electrically heated than solar heated. No, that doesn't matter much. Money matters, of course. Eg the yearly backup heating bill, and the non-recurring cost. >> (Steve Baer only uses 80 kWh/mo :-) >How much do you use, coffee and all? About 600 kWh/month. Mostly for my refrigerator, electric water heater and PC. I just bought a laptop, which should reduce this. >> I guess we'd want to know the thermal resistance of this house for starters. >> So let's add up the thermal conductances U = Sum(Ai/Ri) and find >> the reciprocal 1/U... >> We have 340 ft^2 of windows, >4 sets of 10' x 7' windows = 2800 ft^2 Let's see. 4 x 10 x 7 = 280. I just did that on my calculator to be sure. A 2,800 ft^2 window would be 5 stories tall and 50' wide. >>R4 during a 10 hour day (Uday = 340/4 = 85) >> and R8 during a 14 hour night >R12 at night; R4 + R8 My mistake. >(Unight = 340/8 = 43), with an average daily >> Uwindow = (10xUday+14xUnight)/24 = 60. >> Uwalls = (2(24+48)x16-340)/R24 = 82, and Uceiling = 24x48/R38 = 30. >> And Uinf = 77 Btu/hr-F. >> So U = 60+30+77 = 167 Btu/hr-F and R = 0.006, over 24 hours. >These numbers have to be revisited. Agreed. >> At night the U value would be lower, after you devotedly travel around >> the house and painstakingly put up your night insulation on every window, >> making sure the edges are ever so carefully sealed, akin to some little >> twice-daily religious experience... Unight = 43+30+77 = 150 Btu/hr-F. >> What will the steady state energy flow be for this house after a long >> string of average December days, with an average amount of sun? >> The energy Ein that flows into this house in a day might be >> 280 ft^2 windows :-) Hmm. A new way to measure energy :-) >That should be 2800 ft^2 I don't think so. > x 50% transmission >Try 75% That won't change the picture much. > x 1000 Btu/ft^2/day = 140K >> + internal energy generation = 72K >> total Ein = 212K. >> And the energy Eout that flows out of the house might be >> 24 hours x (68-36) x 167 = 128 K Btu/day. >Of course, these numbers must be revisited as well. Agreed. >>Now, thermal mass: the house has about 3,500 ft^2 of walls and ceilings with >>a thermal mass equivalent to 3,500 pounds of water and another 400 pounds >>of actual water. >10' x 4' x 4" is ~13 ft^3. Water is 62.4 lbs/ft^3. There are >four water walls. >The water will weigh close to 3250 lbs. My mistake again. >> Let's call this 4,000 Btu/hr-F. >You need to revisit this number as well. Somebody should. >> So if you make the temp of >> the house, say, 80 F at dusk, at the end of an average day, with some sun, >> after a long string of December days, each with 1000 Btu/ft^2/day of sun, >> during the night the house will lose approximately 14 hours (80-36) 150 = >> 100K Btu, which might come from the 4,000 Btu/F of thermal mass cooling plus >> 14/24 hours x 72K = 42K of internal energy generation, ie the temperature of >> the house might drop to 80 - (100K-42K)/4K = 65 F at dawn. >You have so many corrections to make before you hit this paragraph that I am >reluctant to mention the ones within. Oh go ahead, mention them. >You have not yet tried to establish the temperature of the water in the >water walls. Oh no. I did that. >Your assumption seems to be 1 oF, though there is no evidence >of how you tried to calculate this. That's pretty cold. That doesn't make any sense to me at all. I don't understand what you are saying at all here Will. And I didn't assume anything like that. I assumed the water walls were the same temperature as the air and everything else in the house. >> How much backup heat will you need in an average year? >My wife wants a fireplace, so I will likely go with a masonry firestove, >often referred to as a Finnish or Russian fireplace, with outside combustion >air. How much backup heat will you need in an average year? >> Were you planning to have hot water in this house? How were you planning >> to do that? >Solar hot water, most likely active. How much will that cost to buy and operate, and how much backup heat will you need for the hot water? >> A better way to compare heating systems >> might be their yearly heating bills, including the electrical power to run >> the heating system. >The model I am planning on building (2250 ft^2) required $168 worth of heat for an entire >winter. Reference "Solar Today", Sept/Oct 1995, article on manufactured house. Sounds nice. As Steve Baer says, the greatest discovery of solar investigators may have been that lots of insulation is good :-) >> >Some people prefer the passive method, and it is not your perogative >> >to tell them that they are wrong in preferring that. >> Oh sure it is, and it seems kind to tell people, if their passive houses are >> such miserable and expensive performers. >Try the numbers again, then we'll talk. It's your house, Will. Try the numbers again yourself, if you like. I'll be happy to look at them. Cheers, Nick Article 51896 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.solar.thermal,alt.energy.renewable, alt.architecture.alternative,sci.engr.heat-vent-ac Subject: Re: "Energy consultants" Date: 17 May 1996 12:28:37 -0400 Organization: Villanova University Peter Skelton wrote: >OK I'll buy the idea that an energy consultant should be able to do >cookbook thermal transfer, it makes sense. What else should he know? Interesting question... >Candidates: > >Predictive cost economics >Cost benefit analysis Sure. Interest formulas, sinking funds, IRR, etc. >Funding and programs I guess so... Not my interest, but... >Available materails, equipment and sources Sure. >gas ducting >fluid piping I guess so. Know a few details, and leave the rest to plumbers, etc? ("Please make the ducts bigger, so we can use less powerful blowers.") >barrier design and construction details >building codes >etc etc. Yes... >Clearly no single person can have everything at his fingertips. Most >professions admit specialization (accounting, engineering and medicine >for example). Professionals, even when qualified, tend to limit their >activities to their areas of competence. Our family doctor in Sarnia >would do minor surgery in his office but sent us to specialists for >respiratory problems like asthma. The fellow we have here does the oposite. Pediatricians can do brain surgery in my state, if they want to some afternoon. And EE PEs can design bridges. It's legal... >One of my customers is an architect. He has designed a circulating >pump that runs off the system energy in a heating loop and controls >itself. He's also designed some interesting heat exchangers. Could he >validly call himself an energy consultant? I think so. So do I :-) >Another acquaintance designs power grids for industry. He is >definitely an energy consultant - all he does is show industry how to >move energy around. He doesn't need to know thermodynamics. I have a feeling he might be familiar with Ohm's law... >There's an energy consulting firm active here that works out cost >justification for cogeneration. They know where to get money and how, >what sorts of industry can use the waste heat, land management. . . . >There might not be a thermodynamically competent person in the place, >they can afford to hire someone like Stone & Webster when they want, >but they are definitely consultants in energy. Yes, but... What we are talking about here is not "thermodynamics" in my book. When somebody uses that term I think Carnot and Rankine and Maxwell and Enthalpy and calculus with difficult integrals. For solar house heating, I think Ohm and arithmetic. With a few old dusty formulae from Newton. Newton's law of cooling, aka Ohm's law for heatflow. And a single simple exponential formula, at best. >To define what an energy consultant is we would have to list >everything one might do and then decide what size of subset a person >would have to master to qualify. It is a dounting task. Somebody offers a credential like that... as a "certified energy manager"? I guess one would want to know some legal and bureaucratic stuff too, like OSHA. The US patent bar exam has a lot of questions like If you appeal a decision related to a notice of infringement in the District Court, for the third time within 7 months, and another party or parties appeal to the assistant patent commissioner or his designated assistant by the third Tuesday in an even numbered month, how many days do you have to file an appeal to that action, and with whom? >All that being said, I can imagine many situations where the simple >test posted might sort the wheat from the chaff. Me too. Nick Nicholson L. Pine System design and consulting Pine Associates, Ltd. (610) 489-0545 821 Collegeville Road Fax: (610) 489-7057 Collegeville, PA 19426 Email: nick@ece.vill.edu Microprocessor hardware, memory, ASIC, and computer design. Telecommunication system design. Computer simulation and modeling. High performance, low cost, residential solar heating and cogeneration system design. BSEE, MSEE. Senior Member, IEEE. Registered US Patent Agent. Fluent in French. Article 51897 of sci.energy: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: alt.energy.renewable,alt.solar.thermal,sci.engr.heat-vent-ac Subject: Re: R-value conversions (was: Solar Heating, Empirical Measu(r)ements & Experience) Date: 17 May 1996 12:46:29 -0400 Organization: Villanova University Alan Braggins wrote: >> nick@vu-vlsi.ee.vill.edu (Nick Pine) writes: [someone else wrote...] >> > Is it true that 1 watt = 3.412 BTU/hr? If so, have I got it right that >> > R-1 (International) degC.m^2/W = R-5.678 (US) degF.hr.ft^2/BTU? >> >> I think so. Let me try this step by step, with a calculator. A 1 m x 1 m wall with a metric R-value of 1 will pass 1 Watt of heat if the temperature difference is 1 C. So a 10.76 ft^2 wall will pass 3.41 Btu/hr of heat if the temperature difference is 1.8 F. OK? So that wall will pass 3.41/1.8 Btu/hr with a temperature difference if 1 F. And a 1 ft^2 wall like that will pass 3.41/1.8/10.76 = 0.176 Btu/hr. (Numerically the same as the metric R-value of an R1 window...) So that wall has a US R-value of 5.68. >% /usr/bin/units >you have: kelvin m2 / watt >you want: rankine hour ft2 / btu > * 1.752557e+00 > >you have: m2 / watt >you want: hour ft2 / btu > * 3.154603e+00 > >Either I'm wrong about Rankine being to Fahrenheit as Kelvin is to >Celsius, I'm misunderstanding units output, or you have used 9/5 >where you should have used 5/9. I've never used that unix function, altho it looks useful. Anyone know the name of the one that turns tabs into spaces? >> Or would those be degrees K, in that particular alphabetical procession? > >For temperature _differences_, Kelvin is the same as degrees Centigrade. But you must call it by the right name, no? :-) Nick Article 5598 of bit.listserv.geodesic: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: bit.listserv.geodesic Subject: Re: Solar Heating, Empirical and Otherwise Date: 17 May 1996 12:49:53 -0400 Organization: Villanova University Lines: 10 Message-ID: <4nianh$so9@vu-vlsi.ee.vill.edu> References: <199605162145.RAA26975@crucible.inmind.com> NNTP-Posting-Host: vu-vlsi.ee.vill.edu James Fischer wrote: > Nick Pine said: > >>Hey it's not a moderated list/newsgroup. I can post anything I want >there... Gee, James, I wrote that to you by email, and you never asked me about posting it... Nick Article 152 of alt.solar.thermal: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: Re: Seek Passive Solar Design FAQ/Guide Date: 18 May 1996 08:47:32 -0400 Organization: Villanova University William R Stewart wrote: >gcp wrote: >> William R Stewart wrote: >> >Nick Pine wrote: >> >> William R Stewart wrote: >> [etc - snip!] Good snip. >> >> One could shorten the warm-up time of the enclosure and increase >> >> the amount of heat delivered to the rooms by making the enclosure >> >> virtually massless--by greatly reducing its dynamic thermal capacity. >> (sounds like a solar panel to me :-) > >Yep. But they are also very expensive, and normally live on the roof, which makes them fundamentally different from these inexpensive sunspaces. These panels are often heavy boxes added on to houses, mounted on brackets, shipped from afar at great expense and manufactured in relatively small quantities, with ducts and plumbing that go through the house roof, and pumps and blowers that eat lots of electrical energy every year. (Yes, that electrical energy can come from PVs, altho they are very expensive now and usually waste 90% of the sun that falls on them, the very same solar energy we are trying to collect with the add-on boxes :-) Some solar air heating panels have low thermal mass. Water heating panels have more thermal mass. I saw a new rooftop-type water heating panel for sale for about $40/ft^2 with lots of intentional thermal mass. It was about 4x8x1' thick, and contained 30 gallons of water, a batch heater with no insulation between the water and the absorber plate and the glazing as far as I could tell. They also had a 50 gallon model... Brick sunspaces have LOTS of thermal mass behind glass with no night insulation, as do many Trombe walls and direct gain houses. This is a very inefficient way to heat a house in a partly cloudy climate, because the thermal mass stores lots of solar heat during the day, and most of that solar heat disappears through the glazing at night. During a week without sun, an isolated sunspace can just get cold, even if it is full of bricks, which is OK. But a Trombe wall or a direct gain house with south glazing in the living space will lose a lot of backup house heat to the outside world through the relatively low thermal resistance of the glazing. >> There is a philosophical difference here that boils down to whether >> you want the sunspace to be part of the living space. >> If you like sunspaces, fine! > >Thank you! I've been trying to get the point across that some people >have their own preferences. Of course people have preferences and that's fine. But let's recognize that that's a lifestyle choice involving a compromise with aesthetics and money and fossil or wood fuel consumption. Let's not drag in false physics. A low-thermal-mass sunspace could be a commercial plastic film greenhouse adjacent to a house, costing 50 cents/ft^2, put up by 1 person in one day, more like a tent than a building. The glazing might be poly film costing 5 cents/ft^2, with a 3 year guarantee, changed every 3 years in an hour, and recycled. Or it might be clear mylar glazing, slightly more expensive and longer lasting, if this inexpensive sunspace leans against a house wall. Or it might be flat very clear polycarbonate glazing, costing $1/ft^2, with a 10+ year solar lifetime, that comes in rolls 49" wide, so it might be simply attached to 2x6s on 4' centers in a simple lean-to sunspace that forms the weather south wall of a house. And to me, a "low-thermal-mass sunspace" can also be $1/ft^2 clear plastic "solar siding," ie a sunspace 2" thick, that takes the place of, say, vinyl siding on the south wall of a house, with no sheathing underneath and only 3 1/2" of insulation in a 2x6 wall. This costs _less_ than normal house construction (no sheathing, less labor), and it collects solar energy. Another way to make a low-thermal-mass sunspace is to make the steep south roof of a house with the same single-layer corrugated polycarbonate plastic, with an insulated attic floor. Again lower first cost than normal construction (no shingles, no tarpaper, no sheathing, and 4' x 12' panels that attach with a few hex head screws) and it can collect solar energy, with a low power fan that blows warm air from the peak of the attic down a large cheap uninsulated duct (eg a poly film tube duct that costs 50 cents per linear foot), into the house when the sun is shining. House air might return to the attic through a $200 2' x 2' motorized damper that lets daylight into the house when it is open. The value of such daylight might be $200/year of electrical power savings, vs the fluorescent equivalent, if it is well distributed inside the house, as well as the aesthetic value of daylighting. >> I am going to suggest that a dedicated sunspace need not be part of >> the design for space heating. I agree. >> If you design your house to be superinsulated, it has been shown that, >> even for houses orientated to minimise passive solar gain, addittional >> energy costs for space heating can be made insignificant. Absolutely true. But at what price? >> With windows available now (R-10+) and orientation to make best use of >> winter sun I think it is possible to reduce space heating costs to >> zero in an otherwise normal house. I agree, IF you are willing to live with very few windows. >> These houses cost little more than a normal house Whoa!!! >> Then the main effort needed is to reduce lighting and water heating costs. True. And how do you reduce water heating costs? Superinsulation doesn't heat water. Can we try to look at more of the whole picture here, and make new houses that have these functions as beautiful integral parts, rather than adding on kludgey afterthoughts, box after box after box, more expensively? >> On the latter a recent design here in the UK (Scotland in particular) >> has aimed at reducing cost rather than increasing efficiency of a >> solar panel. What a strange and excellent idea :-) >Some of the low-E windows I have seen lately have been close to what >Nick had mentioned; one was SC=.59 and another 'heat mirror' SC=.41 They are also more expensive... Cheers, Nick Article 6918 of sci.engr.heat-vent-ac: Path: news.ee.vill.edu!not-for-mail From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Newsgroups: sci.engr.heat-vent-ac Subject: Re: MAKE BIG MONEY FAST!!! Date: 18 May 1996 09:57:14 -0400 Organization: Villanova University Lines: 274 Message-ID: <4nkkvq$62m@vu-vlsi.ee.vill.edu> References: <4ncj4l$9a7@ns2.ptd.net> <4nd4nn$97u@vu-vlsi.ee.vill.edu> <4nism2$jq0_001@nando.net> NNTP-Posting-Host: vu-vlsi.ee.vill.edu paul "ex-mensa" milligan writes: >~>>Nick does have a lot of theories, though he considers many of his untried >~>>pet theories to be far superior to anything anyone else has ever conceived. >~> >~>It's hard to know how to dissect that sentence :-) It looks like an insult. > > Good catch, Nick ! :-) Thank you. I've been working on my human interface lately. I had an old prof at school who was not modest. Fred Jelinek, PhD. I've heard he's now directing the work of 150 PhDs at IBM, who are working hard on a voice typewriter. You know. You talk. It types. He wore loud clothes and often stood up at conferences and asked questions in his very loud Polish accent. He would begin by shouting: THERE ARE VERY FEW PEOPLE ON EARTH WHO ARE SMART ENOUGH TO UNDERSTAND THIS SUBJECT, AND ***I*** AM ONE OF THEM....... Hey, it worked for him... >~>Yes, I'm smarter than most people ("References please"--I belong to Mensa) > > Down, boy. I quit Mensa because it was incredibly boring. :-) I just go sailing with 'em. Sometimes they aren't boring. They can be irritating instead. Less violent than Jerry perhaps. I wonder if we can make a deal? I stop offering him money, and he stops trying to kill me. This might make more sense to me when I take an abnormal pysch course in the fall... >~>I do think _some_ of "my solar theories" are the cat's pajamas, especially > > Could you send me about three pair, Nick ? I don't have any cat's pajamas. How about one of them astronomer's pajamas that plug into the wall, with foil all over the outside? Meanwhile, over in alt.solar.thermal... William R Stewart wrote: >gcp wrote: >> William R Stewart wrote: >> >Nick Pine wrote: >> >> William R Stewart wrote: >> [etc - snip!] Good snip. >> >> One could shorten the warm-up time of the enclosure and increase >> >> the amount of heat delivered to the rooms by making the enclosure >> >> virtually massless--by greatly reducing its dynamic thermal capacity. >> (sounds like a solar panel to me :-) > >Yep. But they are also very expensive, and normally live on the roof, which makes them fundamentally different from these inexpensive sunspaces. These panels are often heavy boxes added on to houses, mounted on brackets, shipped from afar at great expense and manufactured in relatively small quantities, with ducts and plumbing that go through the house roof, and pumps and blowers that eat lots of electrical energy every year. (Yes, that electrical energy can come from PVs, altho they are very expensive now and usually waste 90% of the sun that falls on them, the very same solar energy we are trying to collect with the add-on boxes :-) Some solar air heating panels have low thermal mass. Water heating panels have more thermal mass. I saw a new rooftop-type water heating panel for sale in Texas for about $40/ft^2 with lots of intentional thermal mass. It was about 4x8x1' thick, and contained 30 gallons of water, a batch heater with no insulation between the water and the absorber plate and the glazing as far as I could tell. They also had a 50 gallon model... Brick sunspaces have LOTS of thermal mass behind glass with no night insulation, as do many Trombe walls and direct gain houses. This is a very inefficient way to heat a house in a partly cloudy climate, because the thermal mass stores lots of solar heat during the day, and most of that solar heat disappears through the glazing at night. During a week without sun, an isolated sunspace can just get cold, even if it is full of bricks, which is OK. But a Trombe wall or a direct gain house with south glazing in the living space will lose a lot of backup house heat to the outside world through the relatively low thermal resistance of the glazing. >> There is a philosophical difference here that boils down to whether >> you want the sunspace to be part of the living space. >> If you like sunspaces, fine! > >Thank you! I've been trying to get the point across that some people >have their own preferences. Of course people have preferences and that's fine. But let's recognize that that's a lifestyle choice involving a compromise with aesthetics and money and fossil or wood fuel consumption. Let's not drag in false physics. A low-thermal-mass sunspace could be a commercial plastic film greenhouse adjacent to a house, costing 50 cents/ft^2, put up by 1 person in one day, more like a tent than a building. The glazing might be poly film costing 5 cents/ft^2, with a 3 year guarantee, changed every 3 years in an hour, and recycled. Or it might be clear mylar glazing, slightly more expensive and longer lasting, if this inexpensive sunspace leans against a house wall. Or it might be flat very clear polycarbonate glazing, costing $1/ft^2, with a 10+ year solar lifetime, that comes in rolls 49" wide, so it might be simply attached to 2x6s on 4' centers in a simple lean-to sunspace that forms the weather south wall of a house. And to me, a "low-thermal-mass sunspace" can also be $1/ft^2 clear plastic "solar siding," ie a sunspace 2" thick, that takes the place of, say, vinyl siding on the south wall of a house, with no sheathing underneath and only 3 1/2" of insulation in a 2x6 wall. This costs _less_ than normal house construction (no sheathing, less labor), and it collects solar energy. Another way to make a low-thermal-mass sunspace is to make the steep south roof of a house with the same single-layer corrugated polycarbonate plastic, with an insulated attic floor. Again lower first cost than normal construction (no shingles, no tarpaper, no sheathing, and 4' x 12' panels that attach with a few hex head screws) and it can collect solar energy, with a low power fan that blows warm air from the peak of the attic down a large cheap uninsulated duct (eg a poly film tube duct that costs 50 cents per linear foot), into the house when the sun is shining. House air might return to the attic through a $200 2' x 2' motorized damper that lets daylight into the house when it is open. The value of such daylight might be $200/year of electrical power savings, vs the fluorescent equivalent, if it is well distributed inside the house, as well as the aesthetic value of daylighting. >> I am going to suggest that a dedicated sunspace need not be part of >> the design for space heating. I agree. >> If you design your house to be superinsulated, it has been shown that, >> even for houses orientated to minimise passive solar gain, addittional >> energy costs for space heating can be made insignificant. Absolutely true. But at what price? >> With windows available now (R-10+) and orientation to make best use of >> winter sun I think it is possible to reduce space heating costs to >> zero in an otherwise normal house. I agree, IF you are willing to live with very few windows. >> These houses cost little more than a normal house Whoa!!!!! >> Then the main effort needed is to reduce lighting and water heating costs. True. And how do you reduce water heating costs? Superinsulation doesn't heat water. Can we try to look at more of the whole picture here, and make new houses that have these functions as beautiful integral parts, rather than adding on kludgey afterthoughts, box after box after box, more expensively? >> On the latter a recent design here in the UK (Scotland in particular) >> has aimed at reducing cost rather than increasing efficiency of a >> solar panel. What a strange and excellent idea :-) >Some of the low-E windows I have seen lately have been close to what >Nick had mentioned; one was SC=.59 and another 'heat mirror' SC=.41 They are also more expensive. . . . . . When will someone start building or selling modular sunspaces and solar closets? I'd REALLY like to see this tried out on a larger scale than our little outdoor test structure that's been going with a data logger and modem inside since November 4. I think it's very easy to make solar hot water this way too... The Vegetable Factory seems to be doing a good job of selling $50/ft^2 sunspaces with little emphasis on solar collection. They are doing such a good job that they have developed a very arrogant marketing style, charging big bucks for slim catalogs, refusing to sell through dealers, and hanging up on customers. They also sell electric heaters with their sunspace kits, and most of their elderly affluent customers use them as heated living space with R2 walls... There's a huge difference between the cost of their product and commercial plastic film greenhouses for 50 cents/ft^2 for the materials (Stuppy catalog price) and very low site labor. The labor standard for putting up a 30' x 100' greenhouse in a field, from scratch, is 3 people, 1 day. These are more like tents than houses. Physics prof Paul Bashus and I are beginning to do some more experiments with good instrumentation on insulating double poly film greenhouse walls with soap bubbles. John Groh's old U Arizona paper shows that tiny soap bubbles are as good as fiberglass (R20 at 50 F mean temp, for a 6" layer of foam.) Colder bubbles have higher thermal resistance :-) Unless they break when they freeze... Prof Otho Wells of U New Hampshire was the last person to study this in 1977, and he concluded that it wasn't practical for commercial plastic film greenhouses simply because the care and labor needed to prevent leaks in plumbing and at the plastic film edges would raise the price of the greenhouse to a lot higher than $1/ft^2. In theory, you pump up the bubbles at night with a very small blower and blow the foam out of the glazing cavity back into a small drum (~200X smaller volume) full of soapy liquid during the day. This would take longer if they were frozen. A quarter teaspoon of green Dawn in 10 gallons of water makes a nice 4" foam with tiny bubbles on top of an aquarium with a tiny pump and an airstone. I thought it was cold here in Phila with 5,500 degree days. Duluth with 10K DD might seem balmy to my Russian scientist friend Valerie Kotelnikov, who says his kids got to stay home from school a lot this winter when the temperature _averaged_ -49 F for 5 weeks. We will both be taking a housebuilding course this summer. Valerie is the Academic Secretary of the Tuvinian Institute, Siberian Branch, Russian Academy of Sciences, and he was surprised and worried that he will have to bring a hammer for this 3 week course :-) He barely speaks English, but he has several patents on renewable energy. His specialty is thermodynamics. Siberian houses are mostly insulated with thick walls of sawdust, and they have district hot water heating, which often fails to work. My NREL book says Duluth has an average of 780 Btu/ft^2/day of sun falling on a south wall in December when the average temp is 13 F and the average daytime high is 20 F. That includes a ground refectivity of 20%. If we assume there is snow on the ground or a shallow frozen reflecting pool in front of the sunspace, eg a skating rink made from a 20' wide piece of EPDM rubber roofing material costing 28 cents/ft^2 over a 1' earth berm, that becomes 1040 Btu/day. (The reflectivity of ice is about 60%, water 6%, snow > 60%) An R1.2 double poly or mylar film sunspace would collect 880 Btu/ft^2/day and lose about 6 hr(80-20)/R1.2 = 300 Btu/day while supplying 80 F air to a house, ie 580 Btu/ft^2 on an average December day. If a two story house is, say 30' x 30', with average R25 walls and ceiling and a natural 0.5 ACH, in Duluth, it would have about 3,000 ft^2 of exterior surface area and 16K ft^3 of volume with an natural air exchange rate of 130 cfm, and an overall thermal conductance of about 250 Btu/hr-F, so on an average December day it would need 24(68-13)250 = 330K Btu to stay 68 F inside. Wow... If the house uses 500 kWh of electricity per month, this becomes 260K. Still wow... Which might be supplied by a 450 ft^2 poly film sunspace, eg a sunspace 16' tall and 28' long, almost the entire south side of the house. Or it might come from a slightly smaller R2 sunspace made from two layers of single polycarbonate glazing 6" apart supported on 2x6s 4' on centers as a lean-to sunspace, or a wall with some clear corrugated polycarbonate "solar siding" instead of vinyl siding or a clear plastic steep south roof over an insulated attic floor. It seems simple to get the heat out of the attic with a fan near the peak blowing warm air down into the house thru a poly film tube when the sun is shining, with a return duct in the attic floor, eg a $50 2 watt Honeywell damper actuator attached to a 2' x 2' piece of foil faced foam that lets some daylight into the house when it's open. Move that same house to Abilene, Texas, with 1400 Btu/ft^2/day of sun and an average December temp of 46 F, and an average daytime high of 57 F, and the house will only need 24(68-46)250 = 132K of heat to stay warm, 72K of which might be supplied by a few incandescent light bulbs, leaving 60K, which might be supplied by a sunspace 8' tall x 4' wide with one layer of glazing, with a white surface in front of it, on the front side of the house. Will people there ever disfigure their houses that way? What would the neighbors think? Could one just say "Faith without works is dead"? :-) How many cloudy days in a row does Duluth have in December? Storing 260Kx5days takes 52 55 gallon drums full of 130 F water falling to 80 F, or 3 1500 gal 6' x 12' x 5' tall septic tanks, which might double as the foundation of a house and excellent thermophilic septic pretreatment in a walk-out basement with a glazed south wall... A subversive thought: electric utilities have nice blower door testing and certification programs for houses, but they have to be elecrically-heated houses... But electric heat has a very low first cost, and it isn't expensive if it is hardly ever used....... If a new house is well-sited, and it has an electric resistance hot air furnace, and it just happens to have a large south wall with few windows facing away from the street, it might be an interesting intentional solar retrofit project... After a few of these retrofits the utilities might to catch on and exclude such houses from their blower door testing program, but lots of people do blower door testing, and electric utilities catch on so slowly... Gotta go, Nick Article 216 of vill.computers: From: nick@vu-vlsi.ee.vill.edu (Nick Pine) Subject: MAKE BIG MONEY FAST!!! Date: 19 May 1996 23:15:54 -0400 Organization: Villanova University Here's another litmus test for an energy expert: what will the average water temperature be inside a 4' cube full of water surrounded by 5 R20 foam walls, sitting outside in December, when the air has an average 24 hour temperature of 36 F and the sun puts 1,000 Btu/ft^2/day of heat into the R1 glazed side of the box? And how will that change over time if we shade the sunny wall? Anyone care to answer that question? I'll offer a $10 reward to the first person who answers it correctly. Still only 3 numerical answers to this simple question so far. Two people got part 1 correct, and one has almost solved part 2 using simple arithmetic, but there's still a chance for the right person to earn $10 in 2 minutes with a couple of back of the envelope calculations... This might also be a rare opportunity for someone else to get paid to learn :-) Here's a big hint: If a "solar house" has a heat loss of 150 Btu/hr-F and a the