I live in Central Texas and want to heat a 12' W X 28' L X 4' 4" D exercise pool for year around use as economically as possible. I have the roof of a
24' X 45' RV barn located next to the pool that is available for solar collectors. The sides of the barn face North and South and have no shade. Can I maintain 84 degrees F in the winter using solar heat if I use a cover for the pool when it is not being used? Would I need a booster heat source for cold snaps? Thanks in advance for any information you can provide.
My neighbor is getting it done in SW Florida but he has about 125% of the pool surface worth of collector and it may be warmer here. You can certainly stretch the season. A local solar firm can give you the best answer since they do it there.
I think 84 would be wishful thinking for the dead of winter. I have a large bank of aluminum solar panels, in mid florida, in the coolest part of winter without cover water temp will hit 70 with solar on..but i'm close to the bay and get alot of breeze flowing across the pool surface. My solar is good for about a 8 or so degree boost, but without cover it naturally looses all that at night.
I'd be interested to hear from people with covers and solar in texas and florida to find out how much heat they save with cover. If it would hit 80+ I would get a cover in a heart beat. I just dont think @
70, if you get 8 degree boost from solar, then your cover holds it in, i think at night the shell will still loose too much heat to get even over 80...but i'm just guessing
I don't cover mine either and I can't do much better than ambient air temp. My neighbor does have his covered. That makes a huge difference. I was doing about 72 and he was doing 85. He does have a lot more collector than me and a smaller pool.
Sure. Is the pool itself shaded? NREL data imply January is the worst-case month for solar heating in Austin, when 940 Btu/ft^2 of sun falls on the ground and 1200 falls on a south wall on an average 48.8 F day with a 58.8 daily max temp. An R1 pool cover with 80% solar transmission would make
0.8x940 = 24h(T-48.8)1ft^2/R1, for a pool temp T = 81 F. An R2 cover with
3 layers of plastic film and 70% solar transmission would make T = 104.
A square foot of roof with a 4/12 (18.4 degree) slope would get 940cos(18.4) = 892 Btu/day of overhead sun + 1200sin(18.4) = 379 Btu of south sun, for a total of 1271. If 80% of that enters a solar collector glazing with 84 F water inside and the outdoor temp is (48.8+58.8)/2 = 53.8 for 6 hours, the net gain is 0.8x1271-6h(84-53.8)1ft^2/R1 = 836 Btu/day. A shaded pool with an R1 cover would lose 24h(84-48.8)12'x28'/R1 = 283.9K Btu/day. You might heat it with 283.9K/836 = 340 ft^2 of roof, about the same size as the pool.
So you might buy 2 $75 No. 441428 14'x28' clear vs blue solar pool covers from solarcovers.com (800) 433-4701 and put one on the roof over wires to keep it from gluing itself to the roof when there's no water beneath it.
Probably not, if you are willing to swim in 72 F water. On an average day, a square foot of pool would lose 24h(84-48.8)1ft^2/R1 = 845 Btu. Water weighs 62.33 lb/ft^3, so a 1ft^2x4'4" column of water weighs 270 pounds, and 1 pound of water stores 1 Btu/F, and the pool walls and bottom and earth add more thermal mass, so the pool might cool by less than 845/270 = 3 F on a cloudy day.
I don't recall the exact link, there is a calculator/form on the web for figuring the proper panels.
Place the panels on the South facing roof. When we put ours panels up I could only put them on the East facing side. I went with one extra panel than what was called for and we used 12' panels.
I will cover our pool in the next day or so; since it is cooling down. I have the solar thermostat set at 100 F, but it is dropping into the
60's at night so I loose any pool heat from the day. The cover is a thick solar type and can bring up the temps again in a few days.
Our water authority offers coupons for local merchants selling pool covers to help reduce water evaporation.
-- Oren
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