Article 30815 of alt.solar.thermal: Path: news.misty.com!not-for-mail From: nicksanspam@ece.villanova.edu Newsgroups: alt.solar.thermal Subject: A large pool heater Date: 13 Jul 2008 09:03:58 -0400 Organization: Villanova University Lines: 74 Message-ID: NNTP-Posting-Host: acadia.ece.villanova.edu X-Trace: max.inside.misty.com 1215950526 5512 153.104.44.130 (13 Jul 2008 12:02:06 GMT) X-Complaints-To: abuse@misty.com NNTP-Posting-Date: Sun, 13 Jul 2008 12:02:06 +0000 (UTC) Xref: news.misty.com alt.solar.thermal:30815 The local YMCA gas bill varies from $8K/month in the summer to $21K in the winter. A lot of that heats an indoor pool. They also have a 75'x100' flattish EPDM roof near the pool. We might cover the roof with 2 layers of 4-year UV polyethylene greenhouse film to heat the pool to 84 F and also preheat water for showers with a large pressurized plastic pipe coil in the surge tank. And heat the building, with an HVAC mod for better dehumidification with heat recovery. The roof pitch is about 1' in the 75' direction, so the lower film would always be covered with water if we glue 2x4s to the roof on 8' centers in the 100' direction with silicone caulk. The materials cost would include about $1500 for 2 75x100' rolls of film (replacing the upper one every 4 years) plus $350 for 350' of perimeter aluminum extrusions with stainless steel spring wires to fasten the film plus $250 for 1000' of 2x4s, plus about $50 for an 50 watt static inflation blower, and a few more dollars for some webbing straps above the upper film to avoid wind fatigue. Nick 10 PI=4*ATN(1) 20 PHI=PI*39.88/180'Phila north latitude (radians) 30 DATA 30.4,37.9,620,1000,33.0,41.0,870,1080 40 DATA 42.4,51.6,1200,1070,52.4,62.6,1520,950 50 DATA 62.9,73.1,1760,830,71.8,81.7,1940,790 60 DATA 76.7,86.1,1890,820,75.5,84.6,1710,940 70 DATA 68.2,77.6,1380,1070,56.4,66.3,1020,1150 80 DATA 46.4,66.3,680,990,35.8,43.4,530,900 90 GASBILL=8000'summer monthly gas bill ($) 100 PPTHERM=1.5'price per therm ($) 110 HTREFF=80'pool heater efficiency (%) 120 POOLHEAT=GASBILL/PPTHERM*100000!/30*HTREFF/100'pool heat (Btu/day) 130 GPM=100'heater water flow rate (gpm) 140 DT=POOLHEAT/GPM/60/8.33/6'heater dT with 6 hour solday 160 DCOST=2100'heater cost ($) 170 AREA=75*100'heater area (ft^2) 180 FOR MONTH=1 TO 12 190 READ TA,TP,HS,SS'avg temp,peak temp, horiz sun, south wall sun 200 TD=(TA+TP)/2'average daytime temp (F) 210 N=15+30.42*(MONTH-1)'day of year 220 DELTA=PI*(23.45*SIN(2*PI*(284+N)/365))/180'declination (radians) 230 ARG=-TAN(PHI)*TAN(DELTA) 240 ACOS=-ATN(ARG/SQR(1-ARG^2))+PI/2'arc cosine (radians) 250 DAYLEN=2/15*180*ACOS/PI'day length (hours) 260 SOLDAY=DAYLEN-3'solar collection day length (hours) 270 GAIN=AREA*(.9*HS-(84+DT/2-TD))'pool gain (Btu/day) 280 SOLARPC=100*GAIN/POOLHEAT'solar heating % 290 TGAIN=TGAIN+30.42*GAIN'yearly gain (Btu) 300 PRINT 500+MONTH;"'"POOLHEAT,GAIN;TAB(50);SOLARPC 310 NEXT MONTH 320 PRINT"600'heater area (ft^2):";AREA;" heater cost ($):";DCOST 330 SAVINGS=PPTHERM*TGAIN/100000!'annual solar savings 340 PAYBACK=DCOST/SAVINGS*365'simple payback time (days) 350 PRINT"601'savings ($/year):";SAVINGS;" payback (days):";PAYBACK month pool heat solar heat % solar 1 1.422222E+07 Btu/day 3633276 Btu/day 25.54647 2 1.422222E+07 5342151 37.562 3 1.422222E+07 7644651 53.75146 4 1.422222E+07 9883401 69.49266 5 1.422222E+07 1.158215E+07 81.437 6 1.422222E+07 1.286278E+07 90.4414 7 1.422222E+07 1.256015E+07 88.31356 8 1.422222E+07 1.133503E+07 79.6994 9 1.422222E+07 9053901 63.66024 10 1.422222E+07 6537276 45.96523 11 1.422222E+07 4204776 29.56483 12 1.422222E+07 3066651 21.56239 heater area (ft^2): 7500 heater cost ($): 2100 savings ($/year): 44583.33 payback (days): 17.19252 Nick