Solar Heating

[Shirker]

Last year I got a solar cover to help keep the water temp up. But I'm not satisfied with the mid to high 80's from last year. I am considering getting about 80 square feet of solar water panels. I found a calculator online that said I need between 400 and 500 square feet for my sized pool (16x32) but the calculator provided zero quantitive information about what that amount of panels would accomplish. Is it reasonable to expect an extra 5 degrees with just 80 square feet? I doubt temp is a linear function of square feet, right? So what expectations should I have when comparing 80 square feet to 400 square feet? I'm trying to figure out how much I'm willing to pay and how much yard or roof space I can dedicate to this.

I would be grateful if any of you would be willing to share your experiences. I would also appreciate pictures of your setup and plumbing.

 

[ajw22]

I think @mas985 has a spreadsheet for that.

 

[Shirker]

I think @mas985 has a spreadsheet for that.

Nice! I do like spreadsheets!

 

[ajw22]

See the Pool Heat Transfer Tools linked to in....

Hydraulics 101 - Have you lost your head?

Edit - Before reading this article, you may want to first familiarize yourself with this Pool School article on Pump Basics Hydraulics 101 - Hydraulics, Pipes and Filters When building my pool, I did a significant amount of research on swimming pool plumbing and water hydraulics. I also found...

www.troublefreepool.com

 

[mas985]

I have two different ones (see signature).

The "Heat Txfr" tab is more involved but takes into account pretty much everything.

The "Solar Heat Gain" tab is more simplistic to give rough order of magnitude gains.

But I can tell you right now that 80 sq-ft isn't going to give you much in a 19k pool. Less than 1F per day depending on heat loss.

 

[newtonfb]

I have two different ones (see signature).

The "Heat Txfr" tab is more involved but takes into account pretty much everything.

The "Solar Heat Gain" tab is more simplistic to give rough order of magnitude gains.

But I can tell you right now that 80 sq-ft isn't going to give you much in a 19k pool. Less than 1F per day depending on heat loss.

What about 192sq ft in the same same pool? I only have room on my roof for that (4 4x12 sheets)unfortunately. The only thing stopping me from buying the panels are if its worth it. If I can get 3 or more deg a day I'll do it but if its not going to do much at all I'll just save my money.

 

[Dirk]

If it helps: I'm in Central California, and have a 12K pool with about 400 sq.ft. of solar panels. That probably gets me 5-10°, depending on time of year and wind and other factors. I wish my system was twice as big. But only in terms of heat gain, not in terms of added cost to pump through that. So all things considered, 400 is about right for my pool. Would I do it again? Yes, sometimes that 5-10 doesn't really matter, but for many times it's the difference between wanting to get in or not. For most times it's just nicer to swim in a warmer pool.

I was able to install my system myself, for about $3K, which, over 20 years, is about $30 a month (for the five months of our swim season). I can afford a dollar a day to make my pool nicer to swim in. Natural gas? Not so much. I have a gas heater that I have never turned on. I expect that would be more like $10 a day, probably more.

But I can tell you right now that 80 sq-ft isn't going to give you much in a 19k pool. Less than 1F per day depending on heat loss.

I'd have to agree with Mark's assessment...

Assuming you'll want something automated, you're going to spend a lot just to get the pipes up to the roof and the actuator and the controller and the wiring, for only a very measly heat bump.

Why are you limited to 80 sq ft? I have a lot of roof, but I wanted to save the prime real estate for PV solar (electricity). The solar installer that sold me the materials assured me that putting the pool panels on the north-facing roof would be fine, so that opened up all the square footage I needed. He explained that the sun angle on solar heater panels is no where near as critical as it is for PV solar, plus, since I'm only heating the pool in the summer months, when the sun is almost directly overhead, I don't need to worry about how low the sun gets in the south during the rest of the year. So maybe you have more room up top than you think you do?

 

[Dirk]

Or you could put some on the roof, and some elsewhere in your yard? On the ground, or you could build that patio cover you've always wanted and put some of the panels on that. They don't have to be in a contiguous span...

 

[mas985]

What about 192sq ft in the same same pool? I only have room on my roof for that (4 4x12 sheets)unfortunately. The only thing stopping me from buying the panels are if its worth it. If I can get 3 or more deg a day I'll do it but if its not going to do much at all I'll just save my money.

2.4x the area is 2.4x the temp rise per day. Over successive days there is some additive benefit but usually not more than 2x-4x a single day depending on the weather. So you potentially could expect a single day temp rise of about 2.3F and a multi-day rise 4.6F-9F. Much more if you use a solar cover.