Need opinions on solar heating possibilities

[CarlD]

If you have a lot of sun, it's EASILY do-able!

I use my pool as an example: It's a 16x40 AG with a flat 5 1/2' deepend--about 20,000 gallons and like the old redwood pools--more like a vinyl IG than an AG--it's a FantaSea. My deck is the solar panel--it's 2' wide and surrounds the pool so it's 44'x20' (880 ft-sq)less 40'x16' (640 ft-sq), leaving 240 ft-sq of panel. That is the equivalent of three 20'x4' panels. Yesterday, despite weeks of rain, our pool FINALLY reached 86--and with lots of sun it will go higher--we've had it in the mid-to high 90's.

And my panels are about 1/3 the surface area of the pool and are NOT as efficient as totally dedicated panels as they are decking and brown, not black with lots of tiny tubules. (But they keep the deck cool as an added bonus!)

So I'm thinking that 4 20x4 panels will give you 320 ft-square of dedicated panel. If you get lots of sun it will be MORE than enough. I think 3 will be adequate as well--and it's all virtually free heat.

But you have to have sunshine--without sun it doesn't work at all...as this NASTIEST of springs has shown us.

[wilcfr]

Thanks Carl. I have great sun, but only enough room for 4 4X8 panels which would give me about 128 sq ft, I'm not sure if that is going to be enough.

[CarlD]

Thanks Carl. I have great sun, but only enough room for 4 4X8 panels which would give me about 128 sq ft, I'm not sure if that is going to be enough.

Well, that's if you want ALL the panels on the roof. If you have long, hot, clear days it will add a good bit of heat--even if you have a heat pump it will run more efficiently.

[chem geek]

If your pool is exposed to sunlight, then about 60% of the sun's energy gets absorbed by the water (assuming white plaster; it's higher if you have dark vinyl). With an average pool depth of 4.5 feet, this would be a heating of around 0.7ºF per hour.

Your panels are about half the square footage of the pool, but would be around 80% efficient, so would be expected to be additional heating at around 0.5ºF per hour.

However, if the pool is uncovered, then heat loss from evaporation can be substantial with a 1/4" loss representing almost 5ºF. This means that using a pool cover makes a BIG difference in how much you can heat your pool. If you use a pool cover and solar panels, you get the most benefit.

This post of mine shows that with an opaque thin safety cover and solar panels that are around 80% of the pool surface area, I'm able to get at least a 25ºF water temperature above the average air temperature in the summer (avg. temp now around 60-65ºF and the pool is 87-90ºF). If you used a clear bubble-type solar cover, you could probably get a 30ºF water temperature above the average air temperature, or maybe even more. If you don't use a pool cover, then I would guess that you will only have a 15ºF increase in temp., maybe 20ºF, and it would depend a lot on your humidity and wind.

Carl, do you use a pool cover?

Richard

[wilcfr]

We have an solid color safety cover on the pool. We keep it closed early in the season. During mid summer we tend to leave it open 24/7 because it seems to help with some alkalinity problems we used to have. Of course this summer due to global warming we have had to run the heater everyday except 5 since mid May and keep the cover closed just to keep the pool swimmable. Do the clear solar cover really work that well. I know when we keep the cover closed when the temps are up the pool can get up to 90+ in a day or two with no assistance.

[CarlD]

Yes, solar covers work, and clear ones work best. It's just like a greenhouse. The thicker ones let the light in just as well, but insulate a bit better.

My problem is the expensive thick clear ones only last the same three years as the thinner blue ones that cost 1/3 as much. Yes they work better, but not THAT much better.

It's fairly futile to attempt to solar heat your pool without a solar cover, any solar cover unless you get, as Richard says, SO much panel that it's almost the surface area of the pool. But with a solar cover, 1/3 the surface of the pool (like mine) can be very effective.

As long as you have sunshine, that is....................

[wilcfr]

Ah there is the rub. This year has been a very cool, raining cloudy year so far. Our heat pump has been working a lot to keep the temps up. Solar would have been worthless this year.