re: whacky low-tech "solar wall" idea/s???
26 feb 2003
>> >basically i bought some cheap black fabric and hung that on the exterior
>> >of the wall...
>> what kind of fabric? black aluminum window screen works. home depot sells
>> 4'x25' rolls for $25.
>my fabric was just cheap poly stuff from k-mart about 55" wide, sold
>by the yard for making clothes, etc...
greenhouse shadecloth might work behind a polyethylene cover which limits
the collector temp to about 110 f. window screen seems safer, at about the
>...as a collector substance i thought fabric would be best... wouldn't
>black fabric that is relatively "solid" (not much space in between
>threads) better than black screen in terms of total amount of black
maybe, but less porous fabrics require more fan power, and after air
and sun pass through the fabric, they lose little heat to the glazing.
>the polycarbonate is an interesting option, particularly if the
>difference in efficiency is significant. but cost-wise it comes out
>about equal doesn't it? a 16x10 collection surface is $320 for the
>polycarb, or $32/year assuming it lasts 10 years...
>...the polycarb would be more permanent, although it would have to be covered
that would keep the house cooler and make the polycarb last longer, but
it should be fine uncovered with a few vents to the outdoors at top and
bottom. an alternative is to put some fin-tube near the top of the wall
warmer for year-round water heating, with no vents.
>> greenhouse poly film has uv inhibitors and a 4-year guarantee...
>how much does the greenhouse poly run?
about 5 cents/ft^2, which makes the yearly cost about 1 cent/ft^2,
vs 20 cents for polycarbonate.