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re: newbie solar pointers???
13 dec 2003
offgridman@cs.com wrote:
>i bet nick can tell you how to do a bubble wall that will work.
two plastic film covers with a trough at the bottom with a 10% detergent
solution and a 2" pipe full of holes and a shop vac blower that fills
the space between the plastic films with bubbles with 1000x the solution
volume at night, with an insect screen in an air return at the top that
pushes on a microswitch to turn off the vac when bubbles appear at the
air return. the vac would run for a few seconds each hour to make more
bubbles, as they collapse over time...
>scott wrote:
>> ...my wife wants a heated greenhouse. the problem is we live in indiana.
>> in the winter, it can get down to -10 at times. ughh.
nrel says 510 btu/ft^2 falls on the ground and 770 fall on a south wall on
an average 30.9 f december day with an average max of 38.5 in indianapolis.
>> with normal space heaters/etc.. it would cost a fortune to do this and
>> to be honest i would feel a little bad wasting all that energy to keep
>> some plants warm.
you might just keep them from freezing at night and on cloudy days.
>> so, i came up with an idea to minimize the energy usage. i've seen
>> solar panels used before to heat water for pools. so, i have this crazy
>> idea to pump water through the solar panels and then through a copper
>> pipe maze in the floor and then back to the panels. the floor would be
>> made up of pea gravel so it would be a kind of hot water/steam system.
>>
>> haven't really figured out what to do at night though. :(
>>
>> what do you think, carzy?
carzy. foam insulation is better. a 16'x24' greenhouse with 800 ft^2
of r20 foamed surface would have a thermal conductance g = 40 btu/h-f.
if it's 70 f on an average december day and 40 f after 5 cloudy 30.9 f
days, it needs rc = -5x24/ln((40-30.9)/(70-30.9)) = 82 hours = c/g, so
c = 82x40 = 3293 btu/f, eg 7 dark plastic water drums under benches
near the south wall.
nick
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