Question:
Last year I made a reflector(polished stainless) to focus on 4-4'alum.
>tubes 1-1/2 dia welded top and bottom to a 2" manifold type arrangement.
>I painted the tubes flat black. Any help on these ? would be great
Answer:
OK. Each square foot of "solar collector" can gather about 740x0.9 = 666 Btu
per day (note evil portent) and might lose about 6hr(90-27)1ft^2/R1 = 378 Btu
per day for a net collection of about 288 Btu/day. Suppose your rigid thermal
cover is held up by an inflated top that is 12' above the pool in the middle
and 24' across, with a south-facing area of 12^2xpi/2 = 226 ft^2, so it can
collect about 226x288 = 65K Btu/day of mostly horizontal sun, which is only
about 25 degrees above the horizon at noon on 12/21 in Chicago...
You have about 780 ft^2 of pool surface, ignoring the bottom for now, since
the soil is warmer and has a higher thermal resistance than air. Keeping a
square foot of exterior pool surface at 90 F when it's 27 F outside takes
about 24(90-27)1ft^2/R = 1512 Btu/day, so we need 1512x780/R = 65K, so we
need (US) R = 1.18 million/65K = 18, eg 4" of Styrofoam at R5 per inch, as
a rigid floating cover, and slipped between the liner and the sidewall.
