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re: frugal bucket invented
21 jul 2002
timeoday wrote:
>you can make a swimmin' pool in your pickup that way too! yeeehaw!
or a portable hot tub? nrel says phila gets 1890 btu/ft^2 of sun on
a horizontal surface on an average 76.7 july day. if a 4'x8' r1 solar
cover transmits 80% of that, we need 24h(105-77)g = 0.8x1890x32, so
g = 72 btu/h-f = 32ft^2/r1+56ft^2/r, ie we only need r1.4 walls and
bottom, eg a plywood box with an 8'x12' epdm liner, and some rags or
bags of leaves stuffed between the outside of the box and the inside
walls of the bed.
it might have a 4'x8' cover over the solar one that folds up
to make a reflector, heating 2 tons of 77 f water to 105 in
about (105-77)x4096/(0.8x1890x32) = 2.4 days.
at last, a use for my 1975 ford 250...
nick
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