Is a "passive" solar heat coil worth it?

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gb99

LifeTime Supporter
Jun 15, 2013
137
Boston, MA
I have a heat pump that works well - when I turn it on. Since our yard surrounding the pool gets a lot of southern exposure, I'm thinking about installing a couple of these black solar pipe heaters in line with the return jets. My thinking is that the black pipes would passively capture solar heat and inject warmth into the pool throughout the day. I would install them out of the way so they don't become eyesores. What does TFP think? Any negatives to consider? Thanks.

pool-solar-collectors.jpg
 
Should be a neat experiment. Usually you need the solar collector surface area to be pretty close to the surface area of the pool to be effective but there’s no reason a few land based coils couldn’t give you a little boost.

How do you intend to pump water into the coils and control the flow rate?

You typically want the flow rate to be such that you’re getting a few degrees temperature difference between the intake and the output. I’m sure all the solar heating owners can give you lots of good pointers.

Maybe you can build a small gantry to hold the panels at the right angle to get maximum sun exposure and keep them off the ground.
 
gb99 said:
I have a heat pump that works well - when I turn it on. Since our yard surrounding the pool gets a lot of southern exposure, I'm thinking about installing a couple of these black solar pipe heaters in line with the return jets. My thinking is that the black pipes would passively capture solar heat and inject warmth into the pool throughout the day. I would install them out of the way so they don't become eyesores. What does TFP think? Any negatives to consider? Thanks.

pool-solar-collectors.jpg
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Have never seen one of these in action, but they were designed to do what you are trying using coiled garden hose.
www.belugapool.com

Solar Pool Heater | Beluga Pool Solutions

The Beluga Solar Pool heating Device is revolutionary new solar pool heater that heats your pool with a garden hose. Our device simply attaches to your existing pools’ filtration system to divert a small stream of water into a garden hose collecting heat and returning the water back to the pool.
www.belugapool.com www.belugapool.com
 
I'm interested in what others have to say about these contraptions.

We bought our house with inground pool, closing in December. So ever since, I've been dreaming of being able to use it! It was like I got an awesome Christmas gift, but the batteries weren't available for months!
One of the things I've been dreaming about is building some kind of solar powered heater. Lots and lots of youtube videos of people building them with black irrigation pipe and pumping the water through it.
I'm just not sure how effective it would really be with 30,000 gallons...
 
superdave5599 said:
I'm interested in what others have to say about these contraptions.

We bought our house with inground pool, closing in December. So ever since, I've been dreaming of being able to use it! It was like I got an awesome Christmas gift, but the batteries weren't available for months!
One of the things I've been dreaming about is building some kind of solar powered heater. Lots and lots of youtube videos of people building them with black irrigation pipe and pumping the water through it.
I'm just not sure how effective it would really be with 30,000 gallons...
Click to expand...

That’s basically what Heliocol solar water heaters are. It’s very common in these parts to see those up on roof tops. My neighbor installed an array last year and her pool is 85°F right now while my pool is only in the mid 60’s. As with any solar heating panels, you need surface area for it to be effective. Generally you need about the square foot area as the surface are of your pool. And if you want to retain any of the heat you add during the day, you need a solar cover on the pool.
 
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Woah, that is a lot of square footage! I was thinking about building an array that would just lean against the inside of the north wall of the fence, so it would face the south.

Luckily, that hose isn't super expensive.
 
superdave5599 said:
Woah, that is a lot of square footage! I was thinking about building an array that would just lean against the inside of the north wall of the fence, so it would face the south.

Luckily, that hose isn't super expensive.
Click to expand...

This is what I plan on doing with Heliocol or similar solar panels. I will maybe go with 50% of the surface square footage of the pool.
 
I had not thought about using the pool's pump to circulate water through the heater. I figured I'd have to use a sump pump.

But that Beluga jet hookup seems like an interesting option. What is the risk of damaging the main pump by using it to pump water though a largeish solar array?
 
The problem is f you have more than one return then adding additional head loss to a return will just cause water to flow out of the others preferentially. You would have to cap off or restrict the other returns to force the water into the longer garden hose line. At some point the system pressure will go up and the flow will be reduced.

Using a smaller sump pump rates for the intended head loss of the setup would probably work better.
 
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I have a roof mounted solar panel array. By mid day my water temperature is 90. It is fed by diverting some of the return flow from the filter through the solar array. Again the area of solar panels is about the same as the surface area of the pool.
 

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I keep wasting a lot of time at work thinking about this project! ha ha

I'm curious if there is any real information/data (or, I suppose, great educated guesses) on whether a long coil coil heats more or less efficiently than a manifold system, where cold water goes in one manifold, passes through a series of parallel pipes at the same time, and exits through a second manifold?

If a coil is decently efficient, I also wonder about how much more or less efficient it would be if, say, I were to keep the coil of black hose basically as they come (looped together in a bundle) vs. if I were to build a flat platform to lay it out neatly on? The first option would certainly take up significantly less room than the second. I'm sure the second would be more efficient at exchanging heat into the water, but I wonder *how* much more efficient? Perhaps if I enclosed it in a plexiglass box?
 
The reason people do a flat coil vs leaving it like in the bundle is surface area. If you leave it in the compact coil the outer portion of the coil will receive the radiant heat then the inner coils, not exposed to the radiant heat, will act as radiant cooling negating most if not all of the benefit.
 
superdave5599 said:
I keep wasting a lot of time at work thinking about this project! ha ha

I'm curious if there is any real information/data (or, I suppose, great educated guesses) on whether a long coil coil heats more or less efficiently than a manifold system, where cold water goes in one manifold, passes through a series of parallel pipes at the same time, and exits through a second manifold?

If a coil is decently efficient, I also wonder about how much more or less efficient it would be if, say, I were to keep the coil of black hose basically as they come (looped together in a bundle) vs. if I were to build a flat platform to lay it out neatly on? The first option would certainly take up significantly less room than the second. I'm sure the second would be more efficient at exchanging heat into the water, but I wonder *how* much more efficient? Perhaps if I enclosed it in a plexiglass box?
Click to expand...

Did you read through the Wiki article on it ?

Solar Pool Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com

From the section on DIY coils-

One of the biggest mistakes DIYers make is to use one very long tube coiled up.
Click to expand...
 
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