Anthony Matonak said:
...If it takes a kilowatt to run the pumps to cool the panels and
you only get half a kilowatt extra out of the panels then why do it?
I can picture something like this on the ground, made from 17 18' pieces
of Unistrut, viewed in a fixed font:
|
. |
F| At dawn, in full sun, the panels might
Dynaglas . r| see about 0.9x0.9x0.9x800W/m^2x16'/6' =
corrugated e| 1555 W/m^2... 6 62"x32.5" 165 W Sharp
polycarb. . s| panels might produce 1539 watts, if
n| they are cooled by a few inches of water
. e| flowing through plastic film ducts on top.
18'purlin l| 16'
. | The floor would receive about 6x16x1555/10.76
r| -1539 = 12.3kW of net heat. Two Attwood V1250
. e| 24V 35W bilge pumps could move 42 gpm of
purlin f| water through the ducts, keeping the panels
. | about 12.3Kx3.41/(42x8x60) = 2 F above the
duct duct | 24-hour shaded-pool wet bulb temp.
. panel panel |
-----------------|------evap pool-----
| ~6' | ~8' | ~1'
......................................................
--------------------------------------
| | |
| | |
| P P | |
|-----------------| |
| V V | |
| | |
| P P | 10' wide |
|-----------------| EPDM rubber | 16'
| V V | |
| | |
| P P | |
|-----------------| |
| V V | |
| | |
| | |
--------------------------------------
With sun elevation theta, the panels would see approximately
800x0.9x0.9/3.28(6+16x0.9) = 1185(sin(theta)+2.4cos(theta)) = 3082 W/m^2
(3 suns max), when theta = 26.2 degrees, producing about 3051 watts
of electricity with about 83.4K Btu/h of net heat on the floor, so
the panels might be about 83.4K/(42x60x8) = 4.1 F warmer than
the 68.4 F (20.2 C) 24-hour wet bulb temp in Phila in July.
Nick
10 PI=4*ATN(1)
20 AXISELD=12'axis elevation above horizon (degrees)
30 AXISEL=PI*AXISELD/180'axis elevation above horizon (radians)
40 FL=6'focal length (feet)
50 HEIGHT=1.33'reflector height (feet)
60 N=9'number of strip reflectors
70 PRINT"strip #","bottom (ft)","top (ft)","spacer (in)","tilt (deg)"
80 PRINT
90 A=ATN(HEIGHT/FL)'initial est angle to focus (rad)
100 FOR STRIP=1 TO N'reflector strip # (from bottom)
110 TILT=(A-AXISEL)/2'reflector tilt from vertical (rad)
120 D=HEIGHT*SIN(TILT)'spacer (feet)
130 TH=TB+HEIGHT*COS(TILT)'upper strip edge height (feet)
140 AH=ATN(TH/(FL-D))'new estimate
150 IF ABS((A-AH)/A)>.001 THEN A=AH:GOTO 110'iterate to 0.1%
160 SPACER=12*D'spacer width behind top of strip (inches)
170 PRINT STRIP,TB,TH,SPACER,180*TILT/PI
180 TB=TH+D*TH/(FL-D)'next bottom edge height (feet)
190 NEXT STRIP
200 CONC=N*HEIGHT/FL'concentration ratio
210 OHB=100*D/FL'overhead sun blocking (%)
220 PRINT
230 PRINT"height=";TH,"conc=";CONC,"ohb=";OHB;"%"
strip # bottom (ft) top (ft) spacer (in) tilt (deg)
1 0 1.329988 0.069425 0.2492357
2 1.331271 2.653542 1.718152 6.180075
3 2.718412 4.021652 3.185456 11.51298
4 4.207816 5.485535 4.430827 16.11825
5 5.845247 7.095126 5.455744 19.98893
6 7.676832 8.899349 6.285437 23.19267
7 9.75055 10.94771 6.952877 25.82627
8 12.11791 13.29236 7.489846 27.98812
9 14.83565 15.99017 7.923422 29.76574
height= 15.99017 conc= 1.995 ohb= 11.00475 %