Article 31308 of alt.solar.thermal: Path: news.misty.com!not-for-mail From: nicksanspam@ece.villanova.edu Newsgroups: alt.solar.thermal Subject: Re: poor man's trombe wall Date: 21 Sep 2008 04:36:49 -0400 Organization: Villanova University Lines: 45 Message-ID: References: <8cb951f7-2d4d-479f-bc33-8bf24c2c5ad6@z11g2000prl.googlegroups.com> <48d58d31$0$33226$815e3792@news.qwest.net> NNTP-Posting-Host: acadia.ece.villanova.edu X-Trace: max.inside.misty.com 1221986211 27187 153.104.44.130 (21 Sep 2008 08:36:51 GMT) X-Complaints-To: abuse@misty.com NNTP-Posting-Date: Sun, 21 Sep 2008 08:36:51 +0000 (UTC) Xref: news.misty.com alt.solar.thermal:31308 vmpolesov@gmail.com wrote: >I am interested in passive solar. I am a renter. I have approx 7 m^2 >of south-facing windows in one room. ... 75 ft^2. >... I am thinking of conducting an experiment by putting some landscaping >blocks, painted black, near the window. They might store overnight heat. Does the room get very cold by morning, after an average day? >I know this is not the same thing as a trombe wall because it will not be >large enough to have convective airflow, but there are the same basic >concepts at work. Inefficient ones. Trombe walls lose lots of heat back through the glazing at night. >Will this have any effect at all or should I find something else to >waste my time on? It might be more interesting to turn some of the windows into air heaters that lose little heat at night by pushing in a tight-fitting piece of dark- painted foil-foamboard insulation with an air gap at the top. Or make a "heat storage counter" a 4'x2'x30" tall box with insulation on 4 sides and a 4'x30" glazed south wall (eg discarded windows) south of a light-colored floor with lots of 2-liter water or soda bottles inside the box stacked in a horizontal hexagonal pattern. Water can store 2-3X more heat by volume than masonry (about 4.4 Btu/F for a 4" diam x 1' tall 2-liter bottle, vs 5 Btu/F for an 8"x8"x16" hollow concrete block), and glazing can make the box warmer than the room temp, so the water can store more heat. In December in Seattle, 420 Btu/ft^2 of sun hits a south wall. If a window passes 80% of that and each of N layers of box glazing passes 90% of that and adds R1 to the box and 336x0.9^N = 24h(T-70)1ft^2/N, with lots of water in a 70 F room, the box temp T = 70+14N0.9^N on an average day, eg 82.6, 92.7, 100.6, and 106.7 F with N = 1 to 4 layers of glazing. Nick