Solar Pool heater

[sodamo]

Pool is L shaped, about 39k gallons. Not looking to do a major heat, but my thinking is if I can achieve maybe 3 degrees or so above air temp then ought to be pleasant.
Not being in postcard Hawaii, our daytime temps average in 70's. Yearly low, a rare 59 and high of 81. Want to hook a solar heater loop into the pump line. This pump will be solar controlled - if sunny, should be pumping. First attempt at such a project so willing to listen and learn. Yes, a budget project .
So, I have some 1 inch black poly pipe. Used some pvc fittings to make the turns., fastened with SS clamps (not installed yet on near end) Need to anchor and neaten up, but here is start I got today.
Any suggests/advice/discussion welcome.



David Sent from my iPad Air using TractorByNet

 

[MossRoad]

Make sure all the pipe is UV rated or the sun will rot it.
It looks like you have a in and out manifold. Make sure your in and out are the same diameter as your pump.
Make sure you can drain it when not in use.
Standing water in the black pipes will get well above a temp to burn your skin in a very short time so be careful.
Also, that hot water in the pipes, if dumped on a lawn or landscaping, can kill it, so be aware.

Happy swimming! :thumbsup:

 

[Raspy]

To get the highest amount of energy into the pool, design the system to cool the solar array as effectively as possible. Parallel, not series, or a high flow rate, to get the minimum temperature rise through the pipe. Those black poly pipes will work if you have enough length in the sun. Don't put plastic over them for glazing or it will melt the pipe when sitting up there empty.

Where is your place? I used to live in Kona Paradise about 20 miles south of Kona.

 

[sodamo]

Thanks guys

This will be a direct connect to the pool plumbing, but I will include a TP relief valve just in case. Don't anticipate flowing directly onto grass or where someone might get scalded.

Was thinking about the parallel vs series as it looks like I have enough poly for a 2nd, slightly smaller array. I'm thinking the parallel would be better and thinking I might control each with own valves, meaning I could actually turn either one completely off if necessary. I did find it interesting in the redneck pool heater thread that faster flow was more efficient.

I know the poly is a low melt, so am leaving open. I do hope to incorporate a thermometer to monitor temp changes.

I do want to prevent flow at night or cool days to prevent the cooling effect. Need more incite/research there.

David Sent from my iPad Air using TractorByNet

 

[sodamo]

Raspy

Hamakua side, Ninole.

David Sent from my iPad Air using TractorByNet

 

[alchemysa]

Setting up a solar system is a lot more complicated than some people think. For efficiency the water should go into the bottom of the array so that it completely fills the pipes and displaces all the air. But that means a lot more pressure in the pipe so every joint will be tested. What did you have in mind in this regard?

 

[Jimbrown]

I don't think you have near enough pipe to make much difference. Here is mine there is 600 ft of poly. I think you would get more heat with a large manifold at each end rather than one long pipe.

 

[radioman]

the biggest issue is being able to time it right turning the pump on during day and off before sun goes down. I did a simalar thing by using a smaller submersible pump that connects to garden hose and I put all the hoses I got on the house roof leading to south side and back. I put the pump on a timer and it only rose water 2-5 degrees higher then it was, but not enough to be higher then air temps during the cooler days . So I abandoned this concept.

 

[muddstopper]

Why do you even need a pump. If you can locate the pipe in a manner that it is higher than the pool, ( your roof),you should be able to let water from the bottom of the pool flow into the bottom level of the pipe and the natural convection of the water rising in the pipe as it heats up should supply heated water back to the top of pool. No need for anything electrical and the water will only circulate if the water in the pool is cooler than the water in the pipe. If you use a check valve to prevent flow back to the pool from the bottom of the pipe, it wouldnt even need to be a closed system.

 

[Raspy]

Why do you even need a pump. If you can locate the pipe in a manner that it is higher than the pool, ( your roof),you should be able to let water from the bottom of the pool flow into the bottom level of the pipe and the natural convection of the water rising in the pipe as it heats up should supply heated water back to the top of pool. No need for anything electrical and the water will only circulate if the water in the pool is cooler than the water in the pipe. If you use a check valve to prevent flow back to the pool from the bottom of the pipe, it wouldnt even need to be a closed system.

This will not work at all.

 

[sodamo]

Will definitely be feeding from the bottom up with the connection being after the pool sand filter. At this point the only valves I anticipate are one to prevent back flow and the TP at top. No other restriction on the outflow, so minimal pressure unless considering where the outflow is in the pool. Joints have SS clamps and will just visually test for leaks.

David Sent from my iPad Air using TractorByNet

 

[sodamo]

I don't think you have near enough pipe to make much difference. Here is mine there is 600 ft of poly. I think you would get more heat with a large manifold at each end rather than one long pipe.

Very neat, impressive. I wanted to try the coils but just couldn't get them right. When I get the 2nd array that will give me over 1000 ft of poly.

David Sent from my iPad Air using TractorByNet

 

[sodamo]

the biggest issue is being able to time it right turning the pump on during day and off before sun goes down. I did a simalar thing by using a smaller submersible pump that connects to garden hose and I put all the hoses I got on the house roof leading to south side and back. I put the pump on a timer and it only rose water 2-5 degrees higher then it was, but not enough to be higher then air temps during the cooler days . So I abandoned this concept.

For starters, my pump has a solar controller. Right now it is hooked in via battery and is switch operated but will change to direct connection to panels and the auto function, but that will be a learning experience.

David Sent from my iPad Air using TractorByNet

 

[sodamo]

Why do you even need a pump. If you can locate the pipe in a manner that it is higher than the pool, ( your roof),you should be able to let water from the bottom of the pool flow into the bottom level of the pipe and the natural convection of the water rising in the pipe as it heats up should supply heated water back to the top of pool. No need for anything electrical and the water will only circulate if the water in the pool is cooler than the water in the pipe. If you use a check valve to prevent flow back to the pool from the bottom of the pipe, it wouldnt even need to be a closed system.

Don't think this would work in my given situation, height of roof and the existing plumbing I doubt I could pull a good siphon. I already have the pumps anyway.
David
Sent from my iPad Air using TractorByNet

 

[Raspy]

For starters, my pump has a solar controller. Right now it is hooked in via battery and is switch operated but will change to direct connection to panels and the auto function, but that will be a learning experience.

David Sent from my iPad Air using TractorByNet

Using a solar controller will always give more net energy gain so that's a good plan. Use an unglazed type pool sensor for the roof and a strap on one near the pump suction for the "storage" sensor. You won't need a TP unless you have valves on both the supply and return. But even then, that pipe is low pressure and the typical TP is much higher. Just leave it out, or put it at the bottom as there is no need to have it at the top.

 

[muddstopper]

This will not work at all.

Well, I know for a fact it will work on a smaller scale because I am doing so on a 40gal tank, with 30ft of 1/2 copper pipe. On a large scale, it should work, I just dont know how much pipe you would need to heat that much water.

 

[sodamo]

Well, I know for a fact it will work on a smaller scale because I am doing so on a 40gal tank, with 30ft of 1/2 copper pipe. On a large scale, it should work, I just dont know how much pipe you would need to heat that much water.

Yea, it should if circumstances are right. I had discussed this with an engineer friend a while back. Had I known when constructing the pool I could have incorporated a loop at ground level that would have been almost self regulating, but now it would be major work and expense.

David Sent from my iPad Air using TractorByNet

 

[Raspy]

Why do you even need a pump. If you can locate the pipe in a manner that it is higher than the pool, ( your roof),you should be able to let water from the bottom of the pool flow into the bottom level of the pipe and the natural convection of the water rising in the pipe as it heats up should supply heated water back to the top of pool. No need for anything electrical and the water will only circulate if the water in the pool is cooler than the water in the pipe. If you use a check valve to prevent flow back to the pool from the bottom of the pipe, it wouldnt even need to be a closed system.

This is called a thermosyphon system. It works IF the solar collector is BELOW the storage. Cold storage water is routed down to the bottom of the collector where the water heats, expands and rises to the top of the collector in vertically arranged interior riser pipes. The heated water then flows through a rising pipe back to the top of the storage. Both the outlet and inlet pipes, when used for a pool, must be below water line. The top of the collector must be no higher than the top of the storage for it to work well. There has to be a difference in temp for it to flow and it always tries to get the hottest water to the highest location. This is why the top of the collector must be below the storage. These kinds of systems require a large difference in temperature between the collector and the storage, in this case the collector (black pipe) and the pool. A large difference in temp means a lot of loss to the environment from the black pipe. So, by it's very design it is very inefficient because we want the collector to run as cool as possible. In your design you are giving up efficiency to save on electricity and by doing so are defeating the ability of the system to produce very much energy. It's a bad trade. A thermosyphon system requires glazed and insulated collectors.

There are two reasons why your design won't work in this case. The heat source is above the pool and the collectors are running too hot.

If the collector is placed above the storage, the water in the collector gets hot, but it cannot fall back to the storage because hot water rises. This system is sometimes called a batch system and the water from the high tank is forced down with water pressure when a faucet is turned on.

Pool heater sizing starts at about 50% of the area of the pool in collectors. Of course there are a lot of variables such as wind, pool shading, desired temp, pool cover or not, latitude, collector orientation and slope, etc

I'd like to see some pictures of your system. Can you post some?

 

[alchemysa]

I don't think a pumpless closed system will work with poly pipe. Gravity acting on the water at both ends will suck the pipe flat. And even with a pump thats something you have to consider when the pump is turned off.

 

[muddstopper]

I'd like to see some pictures of your system. Can you post some?

Yea, I'll take a few pic's, but its not assembled now. Not much to see. Just a barrel inside a green house with a small solar collector on the outside. Not even hooked up in the summer, only used to provide enough warmth to keep plants from freezing in the winter.

I have a similar setup in my basement to heat hot water. I used a hotwater heater and built a heat exchanger (S type zigzag) that is bolted to my wood stove. No pumps in it either. Water gets to 180*F.

I did a little off the top of my head math. Considering my system is only 40gal and I used 30ft of pipe, I am heating about 1.3 gal per ft of pipe. If the same type systems, and everything is realative, is used to heat the OP's 39000gal pool, then it would take about 30,000 ft of pipe. Not exactly cost effective. I dont even know what the differences are between using copper pipe and using plastic tubing, but would guess the copper would be a lot more efficient. Dont think anybody would want to buy 30,000 ft of copper pipe to heat a pool with.