Solar Heater

[bg458]

Quick question I was thinking of building one of those DIY solar heater and putting beside the pool. Then it dawned on me that my pool is in dirrect sunlight most of the day, so would I not be better of using a black pvc bond liner and just putting it in the bottom of the pool? Pros and cons? Thanks.

 

[jblizzle]

That would not add any extra heat. The heat from the sun hitting the water is already being absorbed by the pool. I do not think putting black under the water would have a huge impact.

Also realize that solar is about square footage exposed to the sun. It generally is cheaper in terms of $/sqft to buy a true solar panel than to try to build something with black poly pipe. There are a lot of panels for sale for AG pools (not that there really is a difference) on Ebay.

 

[Isaac-1]

I agree the economics simply is not there anymore for DIY solar heater construction, with commercial panels being as cheap as they are, particularly if bought online. I just bought 11 good brand name 4x12 panels complete with mounting hardware (all the roof top parts, I already had the ground level plumbing and controller) for right at $270 each delivered. Going with cheap panels that would still likely be better than anything you could make it could probably be done for under $200 each. Like Jason said it is all about coverage area with solar, the panels I bought each have 104 water channels inside the semi-rigid flat panel (the collectors look a bit like a corogated plastic yard sign, but beefier), that means to they are like having over 1200 feet of small diameter black tubing neatly laid out side by side on each panel all set up in parallel so you don't get excessive flow resistance, you just can't approach that in a DIY construction for the money.

DIY installation of commercial panels on the other hand can be very economical

 

[bg458]

I understand the economic benefits of a commercial solar panel. I still question why I would not get more heat with the black liner in the pool. If I put a black mat in the sun it gets quite a bit hotter than its surroundings and with the black pond liner under the water I would loss no heat to wind. Am I missing something?

 

[jblizzle]

Yeah, that most of the sun's heat will be absorbed in the water before it even gets to the liner. The black liner will likely help "some" after all darker pools are usually a little warmer than white plaster pools.

But I think solar panels would have a larger impact ... and using a cover at night would help a LOT.

 

[Isaac-1]

A black bottom on a pool would help some, but due to the nature of water the heat carrying infra red light gets absorbed in just the first few feet of water, so while there may still be some that makes it to the bottom of the shallow end, there would be little that would make it to the bottom of the deep end then get reflected back to the surface on a light color pool, or absorbed at the bottom on a dark pool, both ways would result in absorption of heat into the water. It has been a while since I studied this but I think something like 90% of IR light gets absorbed in the first 10 feet it travels through water. Assuming a 3 foot deep shallow end and you get up to 6 feet of water penetration (3 ft down and 3 ft back up) when the sun is straight over head, and even more any other time of day.

p.s. this absorption of light starting at the red end of the spectrum is what makes water look blue