# solar heat

Any recommendations for a professional solar pool company in Northern Virginia?
Also - any good links for solar pool covers?
thanks
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Nice... 12' high x 40' long? With some windows near the top for shop light, with reflective lightshelves below and a reflective ceiling?

If the shop roof's thermal conductance is 34x54/R20 = 41 Btu/h-F and the 136' of non-collector wall has 12x136/R20 = 82, the total is 123.
And the shop is detatched from the home and the water heats the home and maybe water for showers, after an efficient greywater heat exchanger?

NREL says 460 Btu/ft^2 of solar energy falls on the ground and 810 falls on a south wall on an average 21.7 F December day with a 29.8 daily max and ground reflectance Rho = 0.2 in Madison, so the average daytime temp is about 26.
With Rho = 0.6, eg snow or white pebbles, the south wall would receive 810+0.5(0.6-0.2)460 = 902 Btu/ft^2. With a 70 F shop air temp, R1 Dynaglas (\$1/ft^2 corrugated greenhouse roofing in 4'x12' corrugated sheets with a 10 year guarantee) with 90% solar transmission might collect 0.9x902 = 812 Btu/ft^2 and lose 6h(70-26)1ft^2/R1 = 264, for a net gain of 548, ie 12x40x548 = 263K Btu/day.
If the shop is used 6h/day and it doesn't store much heat, it needs about 6h(70-26)123 = 32.5K Btu/day, which leaves 230.6K for the house, collected at 230.6K/6h = 38.4K Btu/h. A 2'-4' deep heater with shop air in the space between black fiberglass window screen with the top of the screen attached to the south edge of the heater ceiling and the bottom attached near the shop wall and 150 F air in the space under the heater ceiling might heat 150-38.4K/1600 = 126 F water with 320' of fin-tube pipe or 2 used 800 Btu/h-F auto radiators. Hot collector air might thermosyphon up through the radiators and back down a duct into the bottom of the collector, with a fan and a shop air temp thermostat and an occupancy sensor to keep the shop 70 F.

Have you been listening to crooked masonry salesmen? :-) The wall gets most of the low-angle winter sun, and thermal mass raises the cost and makes the "greenhouse" cool all the time, vs hot during the day and cold at night. If 12x40x812 = 389.8K Btu = 24h(T-21.7)x12x40/R1+6h(T-26)123, T = 54 F. Yuck! A cool shop, with no useful heat storage and no heat left for the house.
Nick
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R19 walls and an R60 roof and 102 ft^2 of R2 windows and 0.5 ACH of air leaks and a 34x54/R60 = 31 Btu/h-F roof conductance and 102/2 = 51 for windows with 136' of non-collector wall with (12.5x136-102)/R19 = 84 and 0.5x12.5x34x54/60 = 191 for 191 cfm of air leaks totals 357 Btu/h-F.

If the shop is used 6h/day and it doesn't store much heat, it needs about 6h(70-26)357 = 94.2K Btu/day, which leaves 168.8K for the house, collected at 168.8K/6h = 28.1K Btu/h. A 2'-4' deep heater with 70 F air in the space between black fiberglass window screen with 67% open area with the top of the screen attached to the south edge of the heater ceiling and the bottom attached near the shop wall and 150 F air in the space under the heater ceiling might heat 150-28.1K/1600 = 132 F water with 320' of fin-tube pipe or 2 used 800 Btu/h-F auto radiators. Hot collector air might thermosyphon up, travel through the radiators and then back down a duct into the bottom of the collector, with a fan and a shop temp thermostat and an occupancy sensor to keep the shop 70 F.

So at the top of the mesh we have 70 F air to keep the shop warm flowing north through the mesh fighting 150 F air that wants to naturally circulate south through the mesh, because its hot air column to the north of the mesh is lighter than the 70 F column of air next to the glazing. If the 70 F air weighs 0.075 lb/ft^3 and 140 F air weighs 0.075(460+70)/(460+150) = 0.065 lb/ft^3 and the heater is 12.5' high, the 150 air bouyancy force would be 12.5(0.075-0.065) = 0.0125 psf, or 0.0024 "Hg, within the range of a fan.
The shop needs 15.7K Btu/h, ie 15.7K/(150-70) = 200 cfm min, ie 0.4 cfm/ft^2 of mesh. If cfm = 27900Asqrt(dP) with A in ft^2 and dP in psf, each square foot of mesh needs an A = 0.4/(27900sqrt(0.0125)) = 0.00013 ft^2 hole, ie a 0.018 in^2 hole, ie a 0.15" hole. We might jab 1/4" holes with flaps using a pencil through dark Typar mesh on a 1' grid behind the window screen and use a smaller fan to move 10 cfm of 70 F air through the mesh when the flaps are closed and the 200+ cfm fan isn't running.
Nick
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