The following is an example of a homemade/DIY solar pool heating system located in Spain. Thank you to Fraser from Spain (otherwise known as Yucca from this overunity.com forum, Forum > 2nd "law" violations > Heat to electric energy conversion > OU Pool heater?) for allowing this information to be made available for others to benefit from. All of the following text is a report from Fraser.
I've built my own solar pool heater for 70 in parts, I've clocked it at 12KW in the hottest part of summer, and it always gives more than 1KW all year round. This heater gives my 60m3 pool a 2°C lift in the summer months here in Spain. It doesn't sound much but it prolongs our swimming season from three months to easily four months, adding two weeks to the shoulder periods of the swimming season. The design is great for hot tubs and manages to mantain 35+°C all year round on a 1m3 insulated tub.
The tube is 10mm black plastic irrigation pipe, good for 10 - 20 years in bright sunlight.
This is as good as free energy when you consider that <100 expediture gives you 10 years+ (more like 20 years) of free heat, or with this system approximately 100,000KWh of energy. At 5c per KWh, that's over 5000 worth.
I built this single unit mainly as a prototype/test. I'm running it every day and just keeping my eye on it for weaknessses etc. So far (2 years uptime) it's proven very robust. The black plastic irrigation pipe is VERY stable in UV; it's great stuff! I don't have an auxillary pump. As the following photo shows, I just put blue pipes from/to the heater coil across the inlet and outlet sides of the pump, thus a small percentage of pool flow gets diverted through the heater.
I am currently in the process of getting the stuff together for a solar hot water system, 5KW panel with 100l insulated storage for nightime use. These are great systems capable of easily delivering 60°C water all year round. and enable you to eliminate electric water heating costs. You need only a few car radiators from a scrapyard underneath a large sheet of glass in a frame and an insulated water tank. The tank sits above the panel and a circulating flow happens without a pump as the hot water rises into the tank which in turn forces the cooler water back round to the heating panel. I expect to be paying <100 in bits for this one too.
In order to get a decent amount of heating you'd have to find roof space for about 4 of these.
Sizing a DIY solar pool heating system
From the tests done by Filpumps on their DIY hose/tube solar pool heating system I was able to to put together this page on sizing a DIY solar system.