How many degrees warmer do solar heaters get the water?

[FLSolDesignGroup]

How many degrees warmer do solar heaters get the water?

I noticed that this question was never really answered based on the OP's question. The answer depends on a lot of factors, and where in the country you are located. Here in Southwest Florida we have people that want to swim essentially year-round except for the coldest few weeks of the year. That means we shoot for a system that can heat pool water 10-12 degrees Fahrenheit above an unheated pool. To do that most commercial panels will need from 80-120% of the pool surface area depending on the panel and orientation. Some panels do better when you need the heat the most (in the winter months). Separated tube type panels lose more heat (or absorb less heat more accurately) in cool and windy conditions. They work best when the ambient temperature is hot (when you need heating the least). Panels oriented to the south or southwest are best.

It is a really location specific thing. You may live in Canada and swim 2 months a year and get 10 degrees of temperature rise with a solar pool heater, but that's because the ambient temperature is warm anyway and a wider variety of panel types may work. Where you want 11-12 months of swimming, orientation and panel selection may become more important.

I'm afraid there is no easy general answer without knowing where and when you want to heat your pool, and a local solar pool heating professional would be your best source to discuss your needs and realistic performance expectations.

It's also important to note that a pool cover will help retain heat overnight, and you will achieve higher overall temperatures. It's not uncommon here to get temperatures 15-17 degrees higher than an unheated pool with a properly sized system and diligent use of a cover. Uncovered pools will lose heat overnight and will take time to recover each day. The amount of heat lost is mostly a function of surface loss and the ambient air conditions above the pool surface.

[Spanjet]

On an average a properly designed solar hot water system may heat up your water upto 75 degrees C / 170F. On Some Summer days it would be couple of notches more, during some winter days it may not heat at all!

Good information, thanks!

[saniconenergy]

On an average a properly designed solar hot water system may heat up your water upto 75 degrees C / 170F. On Some Summer days it would be couple of notches more, during some winter days it may not heat at all!

[skeeter_ca]

I think you will need a bigger pump. More GPM and less temp rise is usually the normal. If you can push enough water through to only get a 2' rise in temp your end result should be a higher pool temp. In layman's terms.

skeeter

[Elsie]

Is 70' going in a solar panel and 78' going out typical?

Is 70' going in a solar panel and 78' going out typical? Is shortening from 500' to 200' going to increase that output 8'? Would we need a bigger pump (current is a 5gpm) to to push the multiple runs?

Thanks for all the good information!

[foo1bar]

I would recommend reducing your coils to 180' to 220' maximum per panel. You are probably maxing out on thermal absorption and not picking up any more heat. Reducing each coil to about 200' and having about 4-5 coils in parallel should help increase your pool temp.

skeeter

"maxing out on thermal absorption" is not true.

There are valid reasons to do shorter coils in parallel - but "maxing out" isn't one.
IF there were some reason that it'd "max out" when the water was 78, then if your pool was up to 78 even with multiple coils in parallel you wouldn't be able to heat it more.

Increased water volume throughput is a valid reason to go with shorter but in parallel.
And there is probably a benefit of more heat transfer because the water temp diffference is greater.
But saying it's "maxed out" is over-simplifying things to the point that what you're saying is wrong.

[foo1bar]

Really? My grandson said he'd seen videos of hoses 1,000' on top of roofs, 4 in parallel. I'll tell him he's watched the wrong ones and make 4 of 250' each in parallel and see the difference. Thanks for the correction.

Elsie

4 in parallel should give you a higher volume of throughput assuming the pump can do that.
You will want to try to match the flow rate through all 4, so if it were me, I'd make sure that the run that's fed in closest to the pump has it's output be farthest.
ex:

from pool >---------
             | | | |
             ----------> to pool

Otherwise 1 of the runs has fewer bends and less distance.

In general the more water you put through the pipes, the more energy you can extract, so 4x250 in parallel is probably better.
(the downside is that requires a manifold/tees - which are extra expense and are going to reduce the flow some.

Good luck.

[skeeter_ca]

Really? My grandson said he'd seen videos of hoses 1,000' on top of roofs, 4 in parallel. I'll tell him he's watched the wrong ones and make 4 of 250' each in parallel and see the difference. Thanks for the correction.

Elsie

Sure people have used long runs and gotten some heat to the pool but if you look at the most efficient ones they all run about 200' per coil in parallel. Just because they make a video doesn't mean they are operating the most efficient designs. A lot of the people that do that later say that the homemade ones don't work and you should stick to factory ones that actually work. But they don't follow the well layed out designs and modify them thinking they know better.

skeeter

[Elsie]

Really?

I would recommend reducing your coils to 180' to 220' maximum per panel. You are probably maxing out on thermal absorption and not picking up any more heat. Reducing each coil to about 200' and having about 4-5 coils in parallel should help increase your pool temp.

skeeter

Really? My grandson said he'd seen videos of hoses 1,000' on top of roofs, 4 in parallel. I'll tell him he's watched the wrong ones and make 4 of 250' each in parallel and see the difference. Thanks for the correction.

Elsie

[Mike90250]

It's really all about storing BTU's and not how hot the water from the heater is. If you slow the flow to get measurably warmer water out, you increase the thermal Delta, and increase the losses. If you only get .2 degrees warmer, there is much less loss, and the pool eventually warms up, not just the top layer.

[skeeter_ca]

I have 8x8 2x500' 1/2" black irrigation tubing. Water going in typically is 70'. Output is 78' normally, not always, and after it's been running a short time. Intial output is around 150'. The pump is a small 5 gpm type. The pool has 3,300 gallons. Over the course of daylight (my location is a rental property, I only get direct sunlight 5-6 hours), the pool will raise to 78', then cools off over night to repeat almost identically the next day. If I had the room, I'd do another 8x8' setup, thinking it would be a 16' raise over the same time period.

I had considered adding 1/2" 50' copper tubing. That 50' to me is free, anything after/over, I would have to pay for. Would it actually help? Or as some others suggest, use a pool cover...

I would recommend reducing your coils to 180' to 220' maximum per panel. You are probably maxing out on thermal absorption and not picking up any more heat. Reducing each coil to about 200' and having about 4-5 coils in parallel should help increase your pool temp.

skeeter

[Elsie]

I have 8x8 2x500' 1/2" black irrigation tubing.

I have 8x8 2x500' 1/2" black irrigation tubing. Water going in typically is 70'. Output is 78' normally, not always, and after it's been running a short time. Intial output is around 150'. The pump is a small 5 gpm type. The pool has 3,300 gallons. Over the course of daylight (my location is a rental property, I only get direct sunlight 5-6 hours), the pool will raise to 78', then cools off over night to repeat almost identically the next day. If I had the room, I'd do another 8x8' setup, thinking it would be a 16' raise over the same time period.

I had considered adding 1/2" 50' copper tubing. That 50' to me is free, anything after/over, I would have to pay for. Would it actually help? Or as some others suggest, use a pool cover...

[J.P.M.]

Our pools ate closer in size & location. My gas heater was able to heat the pool 2-3 degrees per hour back in December when water was 55-60 degrees. I don't know what it cost to run the gas heater since I only ran it a couple of times back in December when I also ran the central great in the house - I've only been in the house a year.

After a PV system is installed I may look into an electric pool heater.


What cost more, a few hours of running a pool pump at a much higher speed (I have a variable) or running a gas heater fir an hour or two a couple of times a month?

I'm not at all sure what your hydro costs are in Ontario, but I'd be very surprised if providing heat to a pool using electricity, even via a heat pump, could compete on a cost basis with CH4. Heating water with electricity is like cutting butter with a chain saw. Match the source to the task.

[MikeInRialto]

Live in Ontario.
Have a concrete pool 16'x32'x8' single depth.
Have 12'x24' of solar thermal panels fed from the pool filter pump.
Easily raise entire pool temperature 2F every day in the summer months.
Pool pump is run from 10AM to 4PM daily. The outlet temperature is typically 5F warmer than inlet.
By second week of June, pool is 84F and stays roughly that till first week of September.

Total cost under $3000 more than 10 years ago.
Little to no maintenance, fixed a leak a few years ago.

Panels look like this :
[ATTACH=CONFIG]6372[/ATTACH]

Our pools ate closer in size & location. My gas heater was able to heat the pool 2-3 degrees per hour back in December when water was 55-60 degrees. I don't know what it cost to run the gas heater since I only ran it a couple of times back in December when I also ran the central great in the house - I've only been in the house a year.

After a PV system is installed I may look into an electric pool heater.


What cost more, a few hours of running a pool pump at a much higher speed (I have a variable) or running a gas heater fir an hour or two a couple of times a month?

[SmartElectric]

Live in Ontario.
Have a concrete pool 16'x32'x8' single depth.
Have 12'x24' of solar thermal panels fed from the pool filter pump.
Easily raise entire pool temperature 2F every day in the summer months.
Pool pump is run from 10AM to 4PM daily. The outlet temperature is typically 5F warmer than inlet.
By second week of June, pool is 84F and stays roughly that till first week of September.

Total cost under $3000 more than 10 years ago.
Little to no maintenance, fixed a leak a few years ago.

Panels look like this :
maintain-pool-solar-panels-800x800.jpg