I have made my own solar heater out of black hose. I’m happy to say The water return is quite warm! Now I’m wondering the best placement of the return hose. Should I leave it hanging on the side of the pool so the water is dropping in? Should I submerge it close to the inlet to help circulation? Should I submerge it near the top of the waterline or at the bottom of the pool? Thanks!
DIY solar heater
- Thread starter Crispychewy
- Start date
Honestly, it really doesn't matter how you do it because that hose is not going to add very much heat to your pool. Solar heating is all about square footage of exposure to the Sun. And you want a heat a lot of water a couple of degrees not a little bit of water a lot.
But if it were to work, what positioning of the hose might be best? I’m hopeful it’ll work. I have about 300 ft of tubing and it’s laying flat on a field with lots of sun exposure. I also have a solar blanket. Also my pool is only about 2600 gal.
Well with those details, it might actually help you a little since your pool is small and you're using a fair amount of hose. I think they cover actually will help you more.
In any case it really doesn't make any difference where you return the warm water into the pool because it is all going into the pool
In any case it really doesn't make any difference where you return the warm water into the pool because it is all going into the pool
- Nov 12, 2017
- 11,858
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
jblizzle is right on both counts. It's a common misconception that the hotter the water is coming out of your heating system the better. This notion is used incorrectly by those with fancy "pro" systems as well as DIYers. It's about the volume of warmer water more so than the temperature. A properly tuned solar heater will only raise water temp running through it by a few degrees, because the goal is to warm a lot of water by a little bit, not warm a little bit of water by a whole bunch.
And as long as your pool is properly circulating, it won't matter where you introduce your heated water. On the other hand, if you're throttling back the flow to get the water as hot as possible in the hose, before you put it into your pool, then it also won't matter much where you introduce it, because without good circulation, it won't do much no matter where it comes into your pool.
To maximize your heater's efficiency, push enough water through it so that it is really pushing the water around in your pool, but feels just barely warmer coming out of the hose than the pool water. Totally counterintuitive, right? But that's how it works...
And as long as your pool is properly circulating, it won't matter where you introduce your heated water. On the other hand, if you're throttling back the flow to get the water as hot as possible in the hose, before you put it into your pool, then it also won't matter much where you introduce it, because without good circulation, it won't do much no matter where it comes into your pool.
To maximize your heater's efficiency, push enough water through it so that it is really pushing the water around in your pool, but feels just barely warmer coming out of the hose than the pool water. Totally counterintuitive, right? But that's how it works...
What size is the hose? If 0.5 inch then 300ft is about 12.5 square feet of area. That's not much compared to your pool's solar collector area. Ninety percent of the temperature increase during the day will be from the pool not the hose.
Since its not going to do much for your pool suggest running it hot and putting in a spot where people can sit in front to warm up.
Tsudduth
0
So is there some kind of calculation one can do to figure out the volume and/or temperature that needs to come out of the solar heater to be effective? I made one last season out of 100 ft of black 1/2" irrigation hose. I put it on my roof for maximum exposure. I also built a diverter that takes some of the return water and sends it through the solar heater. I would like to know how to calculate the anticipated heat gain over time with my setup.
Yes, it can all be calculated based on first principles of physics. There are many ways to do it.
Maybe the simplest approach is something like the following:
1) Given max energy from the sun per square meter (10.8 Sq ft) = 1000 watts per hour.
2) Calculate area of you solar panel and then scale sun's energy by that size.
In your case 100 feet of 0.5 inches = 4 Sq feet.
Therfore if perfectly efficient your panel would produce (4 / 10.8) * 1000 = 370 watts per hour at peak sun.
3) Calculate how many watts hours required to raise your pool by 1°C.
It takes 1.162 watt hours (wh) to raise 1 liter by 1 degree C. Scale for your pool size.
For example a 4000 liter pool would require 4648 watts per hour to rise 1°C. So your panel producing 370 watts per hour would rise this pool 0.08°C per hour.
4) Run water through your solar panel fast enough to limit temperature rise to 1-2°C. This will extract most of the heat from your panel into the pool.
That's the idea and would give you best case results.
In real life there are other factors to consider to get an accurate result.
1) Your solar panel won't be 100% efficient. It depends on the design, wind, water temp, air temp etc. Commercial ones vary between 50-90%. The irrigation hose idea is typicalky towards the lower end.
2) And 1000 watts/m2 only occurs for a few hours around solar noon in the middle of summer. The energy falls off earlier and later in the year and earlier or later in the day. You can look up solar insolation tables for your location to get accurate numbers.
3) Also your pool is a solar panel too and will be heating up on its own without the 100 ft of hose. People often attribute heat gain to their solar panel when it really was all from the pool.
You can use the formulas above to calculate how much heat the pool is capturing from the sun. Just assume it is a solar panel with size equal to the surface area of the pool (round pool = pi * radius^2). Using a bubble cover my pool seems about 70% efficient.
4) And of course there are heat losses from the pool that will subtract from your calculated temperature rise. How much heat loss is complex and depends heavily on pool type, location and weather.
Maybe the simplest approach is something like the following:
1) Given max energy from the sun per square meter (10.8 Sq ft) = 1000 watts per hour.
2) Calculate area of you solar panel and then scale sun's energy by that size.
In your case 100 feet of 0.5 inches = 4 Sq feet.
Therfore if perfectly efficient your panel would produce (4 / 10.8) * 1000 = 370 watts per hour at peak sun.
3) Calculate how many watts hours required to raise your pool by 1°C.
It takes 1.162 watt hours (wh) to raise 1 liter by 1 degree C. Scale for your pool size.
For example a 4000 liter pool would require 4648 watts per hour to rise 1°C. So your panel producing 370 watts per hour would rise this pool 0.08°C per hour.
4) Run water through your solar panel fast enough to limit temperature rise to 1-2°C. This will extract most of the heat from your panel into the pool.
That's the idea and would give you best case results.
In real life there are other factors to consider to get an accurate result.
1) Your solar panel won't be 100% efficient. It depends on the design, wind, water temp, air temp etc. Commercial ones vary between 50-90%. The irrigation hose idea is typicalky towards the lower end.
2) And 1000 watts/m2 only occurs for a few hours around solar noon in the middle of summer. The energy falls off earlier and later in the year and earlier or later in the day. You can look up solar insolation tables for your location to get accurate numbers.
3) Also your pool is a solar panel too and will be heating up on its own without the 100 ft of hose. People often attribute heat gain to their solar panel when it really was all from the pool.
You can use the formulas above to calculate how much heat the pool is capturing from the sun. Just assume it is a solar panel with size equal to the surface area of the pool (round pool = pi * radius^2). Using a bubble cover my pool seems about 70% efficient.
4) And of course there are heat losses from the pool that will subtract from your calculated temperature rise. How much heat loss is complex and depends heavily on pool type, location and weather.
- Nov 12, 2017
- 11,858
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Not to put too fine a point on it... I get maybe 5-8° out of eight of the biggest, best solar panels money can buy, sun all day long, in Central California, pumping 40 gallons a minute through them. That's about 70 tons of water I move up to my roof and back, every day. You're not going to fool the laws of physics with a single strand of some drip tubing...
Better to spend your DIY time on placing and removing a solar cover. Or spend some money on a few cheapie panels and connect those up to your pool.
I believe the irrigation tubing pool heater to be a myth perpetuated by a few that don't have any idea how to perform the necessary experiments to accurately measure what heat they are actually generating. Sorry...
Better to spend your DIY time on placing and removing a solar cover. Or spend some money on a few cheapie panels and connect those up to your pool.
I believe the irrigation tubing pool heater to be a myth perpetuated by a few that don't have any idea how to perform the necessary experiments to accurately measure what heat they are actually generating. Sorry...
Always makes me wonder.. Sure it may defy the laws of physics depending on how you figure it out. But i have seen nurmorus posts on DIY setups that work and work well but yet people are always told it will not work.. I had one and could get easily 5 deg temp rise in my pool during the day. Only reason im no longer using it is the pool does not get enough use to have the pump running every day all day
Mine works! Obviously not as well as a gas or electric heater...but I’ve had it for 2 days and my pool temp has gone up by 2 degrees Celsius. Not a huge diff but for basically no money using old hoses and wrapping it with electrical tape while watching Netflix, it’s not bad.
Also I think the thing about the physics is water had a high heat capacity so when you heat it and cover it with a solar cover to insulate it, it keeps the heat and even though it takes forever it gets warmer little by little as the slightly warmer water gets cycled through again. But the days have to be consistently hot otherwise it will cool down solar blanket or no. I know people say it doesn’t work but I can’t be imagining it.
- Nov 12, 2017
- 11,858
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
If your pool's temperature feels more comfortable to you after you fabricated a way to to use some length of drip tubing to heat some amount of your pool's water, then that's all that matters.
Well, if you think it is helping, by all means keep running it ... does not really hurt anything.
Assuming your pool is 12' diameter ... that is 113 sqft surface exposed to the sun.
300' of 3/4" hose is 18.75 sqft ... so perhaps you are adding about 10% more heat to the pool than you would have without the hose.
Using info from Poolzzz's earlier post:
2600 gallons = 9900 Liters + 1.162 W-hr/LC * 2 C = 23,000 watt-hrs were required to raise your pool by 2 degrees (not counting losses to the environment, especially at night)
I will generously say you have 20 sqft of hose and using the maximum sun output of 1000 W / 10.8 sqft would mean at theoretical maximum the hose can add 20 / 10.8 * 1000 = 1,852 Watt-hr ... in reality due to efficiency and non-peak sun output, it would be significantly less than that.
And your pool itself would capture 113 / 10.8 * 1000 = 10,462 Watt-hr
I will say you are correct that a cover will help maintain a LOT of the heat that would have been lost to evaporation.
I did BTU calculations a few years back when I first played with a DIY panel. 200' of 1/2" poly irrigation line was putting out between 5000 -6000 BTU/hr. The low end of that was running a diverter from the standard Intex 500gph pump. The high end was after the upgrade to the 1000gph system running through the same diverter. I have met run number this year since relocating the solar panel.
Considering it was an hour of my time and $25 of tubing for total one time investment, there is a temperature gain from the panel.
I also have some diy floating solar "rings" which are basically hula hoops with black plastic spanning their area to float on the pool surface. All these with the natural gain on the 12' round pool area. I see about 10 degree F gain daily. Cloudy days we see 3-4 degrees daily. Easily lose 5-8 degrees overnight even with a pool cover.
All of this was merely an academic exercise to give me something "fun to do" on a day off. If it brings my pool water from 75 to 80 degrees, this is worth it to me. Granted a small water volume is MUCH easier to heat.
Considering it was an hour of my time and $25 of tubing for total one time investment, there is a temperature gain from the panel.
I also have some diy floating solar "rings" which are basically hula hoops with black plastic spanning their area to float on the pool surface. All these with the natural gain on the 12' round pool area. I see about 10 degree F gain daily. Cloudy days we see 3-4 degrees daily. Easily lose 5-8 degrees overnight even with a pool cover.
All of this was merely an academic exercise to give me something "fun to do" on a day off. If it brings my pool water from 75 to 80 degrees, this is worth it to me. Granted a small water volume is MUCH easier to heat.
Last edited:
I saw the solar ring idea! I’m wondering why no one makes black solar blankets. Why are they always blue?
I am going to guess aesthetics
- - - Updated - - -
Although there is a discussion that could be had as to whether a clear or black cover would be the best. A clear cover will allow the sun to penetrate into the the water and adding heat through out. A black one will absorb the heat at only the top which will likely result in some energy reflecting/radiating back off of the cover.
But, then we would get back into the physics ... and this thread is not about physics
- - - Updated - - -
Although there is a discussion that could be had as to whether a clear or black cover would be the best. A clear cover will allow the sun to penetrate into the the water and adding heat through out. A black one will absorb the heat at only the top which will likely result in some energy reflecting/radiating back off of the cover.
But, then we would get back into the physics ... and this thread is not about physics
What were the BTU numbers based on?
If based on appropriate measurements then they could give us a good data point for the efficiency of these devices. We'd need to know a few more things though. Were the BTU numbers the average over X hours or the results at peak sun (solar noon)? Also was that middle of summer? Was the tubing stretched out on the ground?
If I assume the BTU was measured at peak sun in middle of summer your "solar panel" was around 30% efficient at the high end numbers.