Hi all, I have a small (12x14, about 5200 gal) in-ground, gunite pool that's on the north side of the house, where it gets very little sunlight during the winter months. As I live in is South Florida, it basically means that the pool is a comfortable temperature (between high 70s and low 90s in the peak of summer) for most of the year, but I'd really like it to be comfortable year-round. I haven't measured it, but I'd guess that in the dead of "winter" it probably drops to the high 60s or low 70s, mimicking the air temperature in the Jan-March timeframe. Electric heat pumps are popular around here, but my understanding based on a proposal I got about a year ago is one would add about $100-$150/month for electricity during the months I'd use it. I have gas, but would need to run a larger diameter pipe to service a gas pool heater. And in both cases I'd be worried about longevity, as I live pretty close to the intracoastal/ocean. Things made of steel and left outdoors don't last very long in these parts. I've thus started looking at solar options. My pump is underneath a large section of flat roof that gets unobstructed sunlight all day long, and I think that my 1.1HP motor should have enough oomph to push the water up the 9-10' needed to reach it, and my rough calculations suggest that somewhere in the realm of 80-160 sq. ft. of solar heater should be sufficient to warm the pool, but I was hoping that someone with more experience and expertise might be able to chime in. Will solar heating be effective (and cost-effective) in my setup? I really have a hard time justifying my pool contractor's recommendation for a pricey electric heat pump (quoted $5500 installed) with unknown life-cycle and high monthly costs just to use my pool a bit more in the winter. Thoughts are greatly appreciated!
Thoughts on a solar (other other) heater setup in South Florida
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When it comes to solar heat there is a question of realistic expectations, think of solar heat as a sailboat an a heat pump as a power boat. With a sailboat you only get to move when the wind allows and only easily in certain directions, with a power boat you get to go when and where you want as fast as you want. With solar heat this means that your pool temperature will drop when you have that full week of dreary cloudy weather, and that the most heat will be available in the peak of summer when you least need it.
Now to put that in practical terms, the issue with solar is declining benefit during the winter, as you have 3 things working against you at once, you have cooler and cooler weather, you have shorter days so less potential total solar heat, and you have less intense sunlight. Now I could go into all sorts of details here, but I have generally found any time I can get into my car after it has been parked outside in the sun and it is hot in the car I also get effective solar heating for my pool. Having said that a good rule of thumb for solar heating size is that your panels should be sized at 75-100% of the size of your pool. Mine are sized at 75% with an indoor pool, and I wish there were 100%, but I am out of effective roof top space, for me this allows a late March through mid November swim season with water temperature over 80 degrees.
Ike
Now to put that in practical terms, the issue with solar is declining benefit during the winter, as you have 3 things working against you at once, you have cooler and cooler weather, you have shorter days so less potential total solar heat, and you have less intense sunlight. Now I could go into all sorts of details here, but I have generally found any time I can get into my car after it has been parked outside in the sun and it is hot in the car I also get effective solar heating for my pool. Having said that a good rule of thumb for solar heating size is that your panels should be sized at 75-100% of the size of your pool. Mine are sized at 75% with an indoor pool, and I wish there were 100%, but I am out of effective roof top space, for me this allows a late March through mid November swim season with water temperature over 80 degrees.
Ike
Welcome to TFP!
Solar panels will get you most of the way on heating your pool. You can add a small heat pump to supplement as needed. An 8 mil solar cover will help a lot to hold in the heat at night.
Solar panels will get you most of the way on heating your pool. You can add a small heat pump to supplement as needed. An 8 mil solar cover will help a lot to hold in the heat at night.
Thanks for the thoughts. Since I have roughly 170-180 sq.ft of surface area, and most of the rooftop solar membranes I've seen are generally 80 sq.ft., it seems like I would have to run either three or four of those units in parallel. Is there significant backpressure from having so many additional (linear) feet of pipe attached to the filtration system? Also, with regard to supplementation with an electric heat pump, do you have a suggestion for a make/model? I'd obviously want something on the smaller side, especially since I don't have a huge amount of additional slab space. Finally -- and I know there are a million variables -- what kind of temperature boost I can reasonably expect from purely solar heating on this scale? If it's 65 deg during the day, going down to, say, 50 or 55 at night during the coldest part of our "winter", could I reach 80F with no supplementation (keeping in mind that in the winter the pool is almost completely shaded)? Thanks again!
For roof top you should be looking at higher quality panels which usually measure 4x10 or 4x12 ft. there are exception though.
p.s. oopps sent send accidentally...
As to your question about back pressure it should be minimal in a well designed panel, the same goes for the plumbing system. Overall the biggest concern I would have with solar install in your area is meeting Florida installation code which is very strict on solar installs due to liability concerns with hurricanes. Which probably means this should not be a DIY project which it otherwise could be in most locations.
Your last question about performance is a hard one to answer, but in general I would say that if you used a solar cover to retain heat at night that using solar heat alone you could easily maintain 80F water with temperatures at 65 during the day if it were not too windy. Wind can rob heat from solar panels, so again that if you get into your car and it is warm / hot inside after it has been parked in the sun analogy works fairly well here.
Ike
p.s. we have a board member that occasionally posts that works for a south florida pool solar company, he does not post here often, but from what I have seen provides good information, I don't mean this to be an endorsement, just a potential lead: Trouble Free Pool he is on the other coast though, so not sure if they do installs in your area or not. It looks like his last post was about 3 weeks ago his business is Fafco Solar Energy Solutions - Solar Energy for all SWFL not to be confused with Home - FAFCO
He may at least be able to refer you to someone reputable in your area.
p.s. oopps sent send accidentally...
As to your question about back pressure it should be minimal in a well designed panel, the same goes for the plumbing system. Overall the biggest concern I would have with solar install in your area is meeting Florida installation code which is very strict on solar installs due to liability concerns with hurricanes. Which probably means this should not be a DIY project which it otherwise could be in most locations.
Your last question about performance is a hard one to answer, but in general I would say that if you used a solar cover to retain heat at night that using solar heat alone you could easily maintain 80F water with temperatures at 65 during the day if it were not too windy. Wind can rob heat from solar panels, so again that if you get into your car and it is warm / hot inside after it has been parked in the sun analogy works fairly well here.
Ike
p.s. we have a board member that occasionally posts that works for a south florida pool solar company, he does not post here often, but from what I have seen provides good information, I don't mean this to be an endorsement, just a potential lead: Trouble Free Pool he is on the other coast though, so not sure if they do installs in your area or not. It looks like his last post was about 3 weeks ago his business is Fafco Solar Energy Solutions - Solar Energy for all SWFL not to be confused with Home - FAFCO
He may at least be able to refer you to someone reputable in your area.
Thanks for the follow-up, it has been extremely helpful. I already knew this wasn't going to be a strictly DIY project, as our insurance company made it clear that any rooftop installation will impact our already ridiculous windstorm mitigation premium. Right now I'm just trying to decide on my best option: (1) running a new, larger-diameter gas line and adding a natural gas heater, (2) using the 240V service that's already next to my filter and adding a heatpump, (3) but adding some PV panels to the roof to offset the guilt I'll generate for using gas or electricity to do something as impractical as heating my pool, (4) adding solar heating and including the additional windstorm premiums (the solar PV has premium adjustments as well, of course), or (5) sucking it up and buying wetsuits for the kids if they really complain 
Knowing your location and the realistic expectations you have, I think solar might be "just right" for you.
1. The pool is small enough to cover easily......that's VERY important.
2. You have adequate roof space to get about 160 sq feet which will be plenty adequate
3. You don't live in Minnesota or the Yukon (big help)
4. I also think your pump (if it's full-rated) is adequate for the task.
I think you have an ideal set-up and i would get a solar guy out to help price it out.
1. The pool is small enough to cover easily......that's VERY important.
2. You have adequate roof space to get about 160 sq feet which will be plenty adequate
3. You don't live in Minnesota or the Yukon (big help)
4. I also think your pump (if it's full-rated) is adequate for the task.
I think you have an ideal set-up and i would get a solar guy out to help price it out.
