Solar Pool Heater

Rich Palmisano

Just a fiddler at heart...
Joined
Jun 17, 2020
Messages
16
Location
J'ville...Home of the Jaguars...
I constructed a DIY radiant heater using 3/4" PEX water tubing, standard metal framing, 2" rigid residential poly insulation and double pane insulated greenhouse glazing. The box itself weighs less than 30 lbs complete. The goal for the project was to create a a heater capable of producing hot water at in the 100-120 degrees F range, connect to heater to the discharge and return side of my pool pump and move approximately 1000 galllons of heated water a day into the pool.

The heater itself can get to 200 degrees inside in good sun, which is enough to damage the tubing so it needs to run with water flowing to prevent this. It can produce the hot water and it did! But being stationary, it only produced peak hot water for about 2-4 hours. So my goal of 1000 gallons a day was cut to about 150-300 gallons on a bright sunny day.

So...being small enough...

I beefed up the frame of the panel itself to be able to mount it on a tracker.

I built a DIY tracker to mount it on. The tracker is a simple 2-axis system with linear actuators, made from lumber, a couple bearings for the east west axis, all bolted and set on a 4x4 post mount anchored in concrete. It's rock solid. The tracker was a kit purchased on ebay, dual axis and actuators. A little difficult to program properly but it works very well. The system has a small 10w solar panel that feeds to a cheap MPPT....(not MPPT...this is a PWM) charge controller that keeps the small 12v 4AH SLA battery charged. The battery runs the tracker module and controls the actuators.

The challenge was, and may still be, a moving panel with water lines. I used a 1/2" flex connector to handle the east/west/north/south movements of the panel and it seems to be working well and not kinking the supply, though I am concerned with the longevity of that component with constant flexing of the tubing.

Photos included: Note that the collector is covered. Keeping the sun off the panel while plumbing work was being done to prevent pipe damage.
 

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grizzzman

Some say "Why" and some say "Why not?"
Joined
Sep 21, 2019
Messages
1,264
Nice job! I would suggest outer springs on the moving lines or better yet, have hydraulic lines made.
 

tellydad

New Member
Joined
Aug 9, 2020
Messages
4
I built two boxes, each with 150 feet of 1/2 inch pex coil, and a plexi cover to add heat to my pool.
problem is the head- I have a 25 foot vertical (only place for 4 plus hours of sun is on a roof), and i have a run of 75 feet to get to the boxes.
I got it running finally by using house water pressure to prime, then switched to my submersible pump 1/6 hp (tried running off my pool pump with no success- that was my goal)
Result: I get about 10 degrees (my return is long, and has to be insulated, I believe I will get about 20 degrees ultimately) but the flow is one gallon per minute. Not great. I was thinking about building a third box, and getting a stronger pump. What do you think?
 

Terrapin

Solar Enthusiast
Joined
Jan 4, 2021
Messages
315
Location
New England, USA
Self built trackers are so cool. Maybe a small independent system for pumping that water through o keep it cool is next.
 

Casper042

New Member
Joined
Jan 26, 2021
Messages
2
Location
Los Angeles
What MPPT are you using?
Does it have a Daylight only mode?

Also is there a trick to getting the glazed greenhouse glass for cheap? Might want to add some to mine to increase the thermals.

I built the full on ghetto version of this, with just some plywood pained black and then black landscaping drip line coiled up on top.
But I found last year when I first built it with a simple DC cutoff between the solar panel and the buck/boost, that the draw on the solar panel when the DC pump started would cause the solar to drop to something crazy like 8v and the DC cutoff would then kill the power assuming it was night.
Then the voltage would increase again and it would attempt to start again.
After several hundred cycles it would eventually get started and then run continuously, but doing this burned out the pump.

So this year, I added a simple 12v 5ah UPS Battery and a cheap PWM MPPT from Amazon.
Works sooo much better.

The problem now is, the MPPT only offers 3 schedules.
1) Run 24h continuous, and only shut off if the battery drops (it does each night)
2) Run Dusk to Dawn
3) Run Dusk+Delay to Dawn

What I really need is Mode 4
Run Dawn+Delay to Dusk.
This way my battery isn't going up and down every day but rather is only running when it's sunny.
Because running the pump in the dark of course makes no sense.
 
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