Solar Pool Heaters, pros and cons.

[wawwie60]

I live in Southern New England and use my above-ground pool from early May until the first week in October. That being said, I am the only one using the pool in May, early June, and September. My wife and kids will not get in if it is too cold.

All other heating choices are out of the question do to availability, access, price, or other limitation.

I meet all the criteria for using a solar heater. I have the space and the sun shines on my yard all day.

What I want to know is this:
1. Are solar heaters reliable?
2. Do they perform as advertised?
3. Are they durable? If a baseball or football lands on it, will it break?
4. Do I need as many panels as they claim? For my pool Fafco says I need 3, 4x20 panels. Can I use just 2?
5. Any additional information is welcome from experienced users.

Please do not give me any information about solar blankets. I understand about these already.

 

[JohnT]

What I want to know is this:
1. Are solar heaters reliable?
2. Do they perform as advertised?
3. Are they durable? If a baseball or football lands on it, will it break?
4. Do I need as many panels as they claim? For my pool Fafco says I need 3, 4x20 panels. Can I use just 2?
5. Any additional information is welcome from experienced users.

1.Very
2.Yes
3. In the summer time, yes. The panels are very flexible. In extremely cold weather, ???, but probably.
4. Even one panel will make your water warmer. The panel calculators make a lot of assumptions, most of which assume you live in a warmer climate than New England. My recommendation is to use as many as you can fit. Also consider an automated controller to maximize gain and minimize losses when it becomes cloudy.
5. A solar blanket is important with solar heat to maximize the benefit, since you can't crank the heat up to make up for a cool cloudy day like you can with gas.

 

[mas985]

Ditto to John's answers.

Also, you will probably here a lot of opinions on what size panels you need. This is because everyone's situation is somewhat unique. The panel size required is dependent on several things including;

Length of extended swim season - how many extra weeks
Heat gain required during season - Heat gain is directly proportional to panel size.
Panel alignment - south pointing and perpendicular to the sun (mid-day) during the coldest months is optimum
Panel placement - roof or ground
Local weather during the extended swim season
Solar cover - will you be using one?

If you are just looking for a modest heat gain during the normal swim season then you probably will need much less panel area (e.g. < 50%) than if you are looking for a large heat gain and an extended swim season (75%-100%).

I decided early on that I wanted as much heat gain as possible so I filled up my south facing roof with as many panels as I could fit. This ended up being about 80% of the surface area of the pool. I am glad I did this since I can get 15-20 degrees of heat gain for the water during some of the most challenging weeks when the water temp would normally be in the low 70s. Because of the large panel area, I can heat the water above 80 degrees in only a few days and be ready for a warm weekend. So I have extended the swim season a couple of months on each end although because the air temp is too low, some of those days I don't like to swim. I also enjoy mostly 90 degree water during the 3 months of the summer.

There are some issues with having solar that you should be aware of. Water evaporation increases because the water can be much warmer than the air. Also, if you don't use a solar cover, you will experience large temperature swings which is related to the evaporation. I have the solar turn off at 90 degrees and because our nights get very cool even in the summer, I can lose up to 8 degrees overnight. The panels have no problem getting back up to 90 degrees in less than 6 hours but with a cover, I can reduce the heat loss to less than 4 degrees so the panels can get back up to 90 degrees in half the time. So a solar cover can help retain the temperature as well as reduce evaporation.

Weather can also have an impact as to how long you can actually extend the swim season. Panels will only raise the pool temperature to the temperature the panels get to in the sun. This can be as little as a few degrees above the shade air temp on windy days. So if 82 degrees is your threshold of water temp pain, then you probably will not be swimming much when the air temp is below 70 which most people would not do anyway.

Having said all that and given your location and how much you want to extend the swim season, I would probably recommend a panel size closer to the larger end of the range rather than the smaller end. That way your are likely to get the results you are looking for. However, given you have an above ground pool, I assume you are putting these on the ground. If so, then it is easier to add panels if you need them later on so you can experiment some.

 

[chem geek]

Solar panels are great and I couldn't live without mine (without paying a LOT for gas heat). You mentioned pros and cons so let me give you a con most people don't think about. Solar panels require decent flow rates (about 4 GPM per panel for the Fafco one's you mention) for efficiency so if you have a lot of panels that can result in a high GPM which will require a larger pump speed and correspondingly higher energy costs. I have 12 panels with 48 GPM needing 1500 Watts from the pump whereas at 26 GPM the pump only needs 275 Watts (my panels are on a long roof with multiple roof hips so are somewhat inefficient in pipe runs). Nevertheless, this extra energy cost is far less than the cost of gas heat (and is ecologically more conscious as well).

Richard

 

[kirbinster]

Solar panels are great, but they may not do what you aim for. The will provide much more heat in the summer than at the extremes of the season. Since you goal is to heat the water early in the year and keep it warm late in the year I think you may not be happy with the results. I have 2 of the Fafco panels for my 20x40 IG pool and they provide all the heat I need in late June, July and early August. Out side that time I have to run my heatpump as well to provide enough heat. And that is with a solar cover in place.

 

[tphaggerty]

I'm in NY, north of the city so I think our locals are similar. Ditto to everything above EXCEPT - go MORE if you can afford it. Why? Adding panels is much more expensive than having more initially (think of the installation cost as relatively fixed, having the installer come back is twice the cost). Actual panel costs are a relatively small part of the overall budget.

Two, not mentioned yet is RECOVERY TIME. Properly plumbed, more panels will heat the pool more quickly. A good summer rain around here can drop the pool temp 5 degrees or so easily. More panels get the heat back in the pool quickly. I added additional panels just for this reason.

I have to disagree somewhat with kirbinster. I am able to get in my pool in May at over 80 degrees 2 weeks after opening (that covers early) and normally swim until mid to late October with the water still in the low 80's (that covers late for around here). October is tough anyway due to the leaves more than losing heat.

I have somewhere around 80% coverage on an east facing roof for my 20x40 pool. I'm pretty close to maxed out on flow rate - but I love it! You have to have a pool cover (again, because of recovery, you will lose 4 to 6 degrees at night without a cover during September). If you have the room, I vote to add panels.

 

[kirbinster]

tphaggerty - yours works because you have so many panels. Most systems are sized at 50% of surface area - and that won't work in the fringe months. Sounds like 80% solves that problem, but most people don't have that surface area available to mount panels.

 

[salinda]

In my case, my variable speed pump has to run at a high speed for many hours a day for my solar to recover from the overnight cool downs. Our energy costs are very high--$0.35/kwh in my bracket. I spent a lot on the solar and I already had a gas heater. If I did a better cost analysis, I would have realized that I should just use the heater more with a shorter pumping cycle. The payback turns out to be years in my case, even in sunny California.

I'm not sure it helps the environment too much either because of the increased energy costs associated with the longer pumping periods at higher speeds (or requiring a booster or larger pump in other installations).

You have to do your own analysis on your own pool with your energy bills right beside you, of course.

 

[mas985]

Salinda,

Most solar systems do fine with 40-60 GPM flow rates so full speed should not be necessary. Have you tried to reduce the RPM to save energy? The benefit of reduced RPM is quite significant in a VS pump.

 

[salinda]

I have some mats and some coils in my system. Unfortunately, the coils have a much larger diameter tube and require higher flow. They also have higher dynamic head loss than the mats. Too bad. If I had it to do again, I never would have installed this "hybrid" system.