Solar Panel Heaters

pmsmith2032

Well-known member
Jan 11, 2011
163
Northern Illinois
Has anyone had success with solar panel heaters? If so, where are you located, what size pool do you have, how many panels and what brand do you have, and how much improvement have you seen? I am thinking about buying one/some but I'm not sure where I'm going to put them. Thanks!
 

mattsmith321

Bronze Supporter
Jul 20, 2017
40
Austin
I bought the Smartpool S601P SunHeater Solar Heating System for In Ground Pool for ours and attached it to the Superior Pump 91330 1/3 HP Thermoplastic Submersible Utility Pump with 10-Foot Cord. Then I used 200' or so of 1/2 in. (0.700 O.D.) x 100 ft. Poly Drip Tubing. The panels are fastened to the house roof. I did not fit it into the main pool filter pump primarily because I didn't want to go through the effort but mainly because we are in Austin, TX. It is nice to throw the pump in the pool for a bit to get it warmed up but it really isn't necessary once late May rolls around. I originally bought it because I tried opening the pool around spring break in March. It isn't uncommon to have 90° days in late March and early April so there was some pressure to open the pool early in previous years. However, there is a pecan tree right above the pool and it drops its tassles/catkins in late April / early May which was a pain to deal with. Given that it ended up not being used much early on, the new rule is that the pool opens up Mother's Day weekend. I just took the tarp off last night. The water temp is 74°. We are in for some cooler than normal days so I think I will see about firing it up for a bit.
 

mattsmith321

Bronze Supporter
Jul 20, 2017
40
Austin
To add some additional unscientific details as measured with my polar bear pool thermometer:
  • As mentioned, water temp is 74° right now
  • I put the pump in and have let the water run through the heater for 20 mins now.
  • It is currently 73° here in Austin and I would say it is about 95% sunny. There is an oh-so slight thin layer of cloud floating around.
  • The inbound water temp after running through the heater is 83-84°.
  • Pump is outputting about 3 gallons per minute (180 gallons per hour) with a lift of about 10-12'.
  • Maximum sun exposure is probably around six hours from 11am until about 5pm.
  • Pool is around 8400 gallons.
  • So 180 gallons per hour for six hours per day would run around 1080 gallons per day.
  • Rounding things a little bit, at that rate, I should be able to increase the temp of the pool by about 1° per day.
  • Sunday and Monday look sunny as well. I'll see if I can remember to check in and see how it is doing.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,045
Pleasanton, CA
Pool Size
20000
Surface
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200' of 1/2" poly is only 8 sq-ft of panel size. The sun in your location, assuming no clouds, produces about 2400 BTU/sq-ft/day on a flat plane which would be about 19200 BTU/day. However, most solar panels are only about 80% efficient so that drops to about 15360 BTU/day. For 8500 gallons, that is 0.22F temperature rise. So I think your estimate is overly optimistic. The sun does not generate that much heat to raise it 1 deg/day.

In the heat of the day, the output of the sun is 310 BTU/sq-ft/hr or 41 BTU/min or 33 BTU/min out of the panel. At 3 GPM, that would be about a 1.3F rise from inlet to outlet. So your flow rate may be much smaller through the panels than you think it is.
 
Last edited:

mattsmith321

Bronze Supporter
Jul 20, 2017
40
Austin
200' of 1/2" poly is only 8 sq-ft of panel size.
Apologies if it wasn't clear in my initial post. The 200' of 1/2" poly is the run from my pump in the pool up to the SmartPool SunHeater "solar panels" on the roof. It is comprised of two panels, each about 2' wide by 20' long. Each panel sends the water through dozens (not going up to count them) of tiny tubes. 80 square feet total per the product description. Regardless of what the actual rise is (1/4° vs ~1° per day), I won't need it very long here before the pool is plenty warm. But yes, if you live somewhere cooler, have a much larger pool or get less sun, it would make sense to break out a calculator and do the real math for your situation.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,045
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
Thanks for the clarification. Now it all makes sense.

But if you have 80 sq-ft of panels, then your flow rate through them really should be at least 8 GPM (0.1 GPM/sqft). With only 3 GPM, you will be losing a lot of heat due to the temperature rise in the panels. Generally, you want to target a inlet to outlet temperature rise of less than 5F to maintain efficiency. I suspect the 1/2" poly is really restricting your flow to the panels.
 

mattsmith321

Bronze Supporter
Jul 20, 2017
40
Austin
Yes, the 1/2" poly is definitely a restriction. The pump is designed to handle 1-1/4" out and can in theory push that 22gpm up 15' in the air based on the chart in the manual. However, in my case it was less about achieving maximum efficiency (and the study to understand what it is) and more about how to cheaply and easily implement a solution that worked to meet the request ("Can't we get a heater to warm it up?"). The 1/2" poly drip irrigation tubing was the cheapest and easiest way to solve the 100' run each way in my case.
 

mattsmith321

Bronze Supporter
Jul 20, 2017
40
Austin
Of course, it dropped down to about 55° here last night so I lost most of my gains from yesterday since I have an above ground pool...
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,045
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
Yes, the 1/2" poly is definitely a restriction. The pump is designed to handle 1-1/4" out and can in theory push that 22gpm up 15' in the air based on the chart in the manual.
That is just static head. You have to add in the dynamic head as well which reduces the flow rate further. Probably much more than the lift. I think you are lucky to get 3 GPM.
 

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jbilliel

Active member
May 5, 2020
37
Connecticut
I am putting in a 27' round above-ground and live in CT. I bought a solar cover, but I know that won't be enough... I have been looking at solar for a week straight and the one thing I am struggling with is the run of pipe and up the first story to get the water to where the panels would be placed. It will be over 100 ft to the house and back when including the piping up the roof, etc. I am getting a 1.5hp pump installed, but worried it may not be enough hp.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,045
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
For a number of years, I ran solar on a two story house with a 1/2 HP pump. The pump isn't the issue. It is the plumbing that matters.
 

Mike0893

Bronze Supporter
Oct 7, 2019
27
San Martin, CA
I installed a solar heating system for our pool over the off season. It has 672 sf of panel surface area. That is about 83% of pool surface area. We just started using it last month. It’s great. Temp here today was 77 and the pool reached 84. I have a 2 hp pump and the panels are 225 feet away with a 10 foot rise. It wasn’t cheap but you only pay once. From now on warm water.
 

jbilliel

Active member
May 5, 2020
37
Connecticut
I am asking the pool installer, but it appears that all above grounds are typically plumbed with 1.5". What size pipe are you running Mike?
 

Mike0893

Bronze Supporter
Oct 7, 2019
27
San Martin, CA
All my pipe is 2 inch. I get about 63 gpm. I had a proposal giving to me by a solar installer and they wanted to install 2.5 inch pipe so that the system would achieve 70gpm. That wasn’t necessary.
 

mattsmith321

Bronze Supporter
Jul 20, 2017
40
Austin
Why are you using a seperate pump and not have it plumbed into your pool pump system?
Primarily because it wasn't right for my situation: Limited funds, relatively temporary installation, lack of real need for real heat here, first time pool person, etc. Maybe someday in our next location...
 
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