Solar Pool Heater

**daveob** · 07-Nov-11, 06:41 PM

Well, after 3 more mostly overcast days, the temp has still reached 25.5c Had the first swim of the season this afternoon - FANtastic. Will be watching the surrounding pools to see when they get to a similar temperature ( +25c ) so that I can calc the extra swim time that the solar coils have added to our pool. Will be doing the same at the end of the season. Last year we stopped when it dropped to 24c ( Yes, Wynn, we're wussies ). Am looking forward to seeing how much longer we can continue after the surrounding pools get to 24.

Also, my log so far is telling me that we gain 2c per (reasonable) day, but lose 1c every night. On an overcast day we might not gain anything, so the 1c loss overnight means that we go back a step.

Am seriously considering the solar blanket now, as it should reduce the overnight loss considerably, making the cumulative daily gains much higher.

**AndyD** · 07-Nov-11, 08:05 PM

I think even a cheap pool blanket would be a good investment for you. The industrial strength bubble wrap type don't cost a fortune and last 5 or 6 years if you treat them well.

**daveob** · 07-Jan-12, 10:48 PM

Project Update :

After enjoying the benefit of the first 4 coils and keeping a spreadsheet of the morning and afternoon temperatures for the last 2 months, we're quite happy with the 28 degrees temperature. We had 13 sunny and hot days in a row, and during this time, the temperature never got higher than 28 celcius. I think that this is the point where the heat going in equals the heat lost to the air and ground.

Anyway, after 2 cool and rainy days, I eventually added the 3 extra coils I wanted on New Years eve. This was for 2 reasons. Firstly, I already had the additional piping for the project, and secondly, we got 24 hours notice of visitors arriving from inland, and I knew that without the additional heat that the 3 extra coils would produce, we wouldn't be swimming for most of New Years Day.

This has increased the coil area to 41% of the pool surface.

Temperature increases since then have been as expected - on sunny days, depending on the amount of cloud about, water temp increases between 3,5 and 5,5 degrees celcius.

Also, since summer is in full swing, we're not losing as much heat overnight.

The pool is uncovered, and we live on a sea facing windy hill, so I think that if I get any higher than the current max of 31 celcius ( this afternoon ), then the heat loss ( to air and ground ) will probably start to cap the limit that the coils can heat to.

Yes, I know our new average of 29 celcius seems a bit warm, but the swim school that my kids go to is 31, and until this last week, my 3 year old daughter refused to get in our 'cold' water. Now I have to argue with her to get her out the water. That alone has made it all worthwhile.

My rough calculations show the energy being added to the pool is around 242,000 BTU per day.

**Dave A** · 08-Jan-12, 06:49 AM

How are you going for water loss?

**daveob** · 08-Jan-12, 09:00 AM

Hi Dave A

I've not noticed any change in the loss due to evaporation.

Not had to put the hose in the pool for over a year now.

I have made an extension to a downpipe that ends about 1 meter from the pool. When we get rain, I wait for enough water flow to wash the dust off the roof, then I add on the (push on) extension to divert the water to the pool. Have often topped-up 10-15 cm in one day. The extension also has a plate blocking the bottom half of the (almost horizontal) outlet, so any additional dust or debris stays in the pipe.

On the few occasions where I have filled the pool to the brim, I use it to do an extra long backwash ( 4 - 5 minutes ) which seems to help the sand filter.

**daveob** · 10-Jan-12, 03:00 PM

I think I may have created a monster here !!

Not only have the coils on the roof created a cooler entertainment area by absorbing the heat on the roof, but I had to shut it down at midday. Water temperature got to 32 degrees, which means it's now warmer in the water that out.

Calculated 500,000 BTU added during this morning alone.

I think I may have to throttle down the flow to avoid an uncomfortable and unhealthy pool.

On the plus side, I think that our swim season is going to be hugely increased into autumn and winter.

Having now completed the 'test' system, I'm looking for a way to market the recipe. Main component that I will be needing is the centre hub for the coils. Will be a disc of about 450mm diameter, with 6 holes into which bracing pipes would fit.

Any ideas on who I could approach ?

Would fibreglass be an option ? Would it withstand the UV exposure ?

**AndyD** · 10-Jan-12, 03:31 PM

Fibreglass lasts many years in sunlight.

How much more water are you losing through evaporation with the pool at 32 celsius?

**daveob** · 10-Jan-12, 03:49 PM

Originally Posted by AndyD

How much more water are you losing through evaporation with the pool at 32 celsius?

Not sure Andy. Today was the first time it hit that high, and I don't want it to be above 29 or 30, so I bypassed the coils to allow it to start cooling again.

I want to swim and cool down, not use it as a bath !

It usually loses between 1 and 2 degrees overnight depending on overnight temperatures and wind conditions, so should be back to the preferred level by the morning ( I hope ).

In the meantime I have invited the "doubt it would work well" mates for a braai tonight - they owe me a few beers now.

**AlexandroAlexandro** · 04-Mar-13, 05:54 PM

Sunlight heats up the elements involved, which snare the heat energy and channel it into heating the water. Me and my wife also looking forward to installing for home pool(16' x 4').I read out interesting and informative ideas.This will be helpful for me.Thanks everyone...