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re: solar air collectors? do they work? buy or make?
26 oct 2004
stuart gold wrote:
>i have converted my garage to an art studio.
say it's 16'x24'x8' tall, with a long south wall.
>after insulating the walls and ceiling...
how much? g = 1024/r btu/h-f.
>...i'm located in the foothills of the california sierra mts...
an easy climate. nrel says santa maria has 1390 btu/ft^2 of sun on
a south wall on an average 51.1 f january day, when your studio might
need 8h(65-51.1)g = 114k/r btu of heat.
>...right on the top of a ridge with a solid straight on southern exposure.
no shading... :-)
>i am have been thinking about using solar air heating...
how about thermosyphoning air panels on the south wall warming low-e
ceiling mass and a slow ceiling fan controlled by an occupancy sensor
and a room temp thermostat?
>1. will a solar collector supply most if not all the heat that i will need?
sure, if designed to do that. you need about 570k/r btu for 5 cloudy days...
>2. will i save any money if i build versus buy... ? looking
>mostly at the cleardome system ( http://www.cleardomesolar.com/ )
gary spent $2/ft^2. cleardome charges $895/(2'x8') = $55.94/ft^2.
then again, they are still selling indoor solar collectors :-)
help@prepusa.net wrote:
>check out www.hotboxsolar.com
wow, only $399/(2'x4') = $49.88/ft^2 :-)
>they sell a reasonably priced air heater...
looks like "they" is "you" :-)
>3. if i do decide to build, is glass or polycarbonate best for the top? =
i'd use a single layer of "dynaglas" corrugated polycarbonate.
this greenhouse roofing material comes in 4' wide sheets.
flat polycarbonate comes in 4'-wide rolls.
>4. for the adsorber plate tin is much cheaper than copper. what
>materials off the best bang for the buck?
your brown shingles behind a single layer of black window screen.
>5. many of the pre-built units have thermo switches that start a fan =
>when the air reaches 100 degrees.
grainger sells them, but i'd thermosyphon.
>...4' x 8' would be about the maximum size that i would want.
then again, you want 100% solar heating. you might have room for 4
4x8s among the windows. if 1 ft^2 collects 0.9x1390 = 1251 btu and
loses 6h(130-51.1)1ft^2/r1 = 473, the net gain is 778. there's a
tradeoff between polycarb ($1/ft^2), insulation ($0.34/ft^2 for "r7.2"
1" double-foil polyiso board) and ceiling mass ($5/4"x10' 55 btu/f
thinwall pvc pipe.)
if each of n $50 4x8 collectors can make 24.9k btu/day, the studio needs
r = 114k/(24.9kn) insulation and p = 570k/((130-80)55) ceiling heat store
pipes for cloudy days. if pipes cost $5 each and covering 1024 ft^2 of walls
and ceiling with r-value r insulation costs $0.34x1024r/7.2...
n cc r cr p cp total cost
1 50 4.58 221 45 225 $496
2 100 2.29 111 91 455 666
3 150 1.53 74 135 675 899
4 200 1.14 55 182 910 1165.
if the ceiling is 16'x24' of poly film ducts ($40) containing up to
5" of water over mylar film ($40) over welded wire fence ($40)...
n cc r cr cp total cost
1 50 4.58 221 120 $391
2 100 2.29 111 120 331
3 150 1.53 74 120 344
4 200 1.14 55 120 375.
nick
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