DIY Solar Panels

[Marvo]

I wanted to throw an idea out for comment before I run out and spend hard earned cash on a white elephant.

I've designed a home built solar heater for my fibreglass swimming pool. The intention is basically to extend the swimming season in spring and autumn by being able to raise the water temperature by maybe 5 or 6 degrees. The pool is positioned in an area where it only gets mid to late afternoon sun which is fine in the middle of summer, the water temp is generally around 20-24C but it gets pretty cold when the wind blows in spring and when the temperatures drop in autumn (April/May).

The pool is small (6mx4m and 1.5 deep on average) and there is a single storey granny flat with a flat roof about 8 meters away from it. I was going to mount the home made panel flat on the roof where it will get midday sun and it's also not too difficult to run pipework up there.

I was thinking of constructing the solar panel out of LDPE class6 25mm pipe. I was working on using 200meters to start with coiled into a flat spiral which would end up around 3-3.5 meters in diameter.

The water would be circulated by it's own pump because the normal pool pump that runs the filter system is 1kW and will prove expensive to run for long periods. I sourced a 200watt Speck Pump that fits the bill and should give around 4 cubes per hour with the panel height and pipework static losses taken into consideration.

I know it's not the most scientific design but there were so many variables that I ended up just winging it with something that will hopefully work and I can always add another home made panel if it's not very effective. The total cost of the whole project including pump, pipework insert fittings, stainless pipe clamps etc is around ZAR 1500 (110 UK Quids) so it's not too much of a gambol.

Does anyone think this system might work and would anyone venture an educated guess on how well?

*Edit* Thought it might be worth mentioning that I'm on the coast in Cape Town.

 

[Battlestar]

No expert but an idea to heat you pool up but have you considered building a solar water heater (many good designs shown on youtube and builditsolar website. Throw in a fresnel lens and you should easily be able to heat that pool up.

 

[Marvo]

Thanks for the suggestion. I actually hoped the scilence on this thread was an indication that there was nothing fundamentally wrong with my plan so I purchased 200m of pipework and a pump. I've also started preparing some 1.2 x 2.4m plywood boards to mount it on the roof with.

I'll take some progress pictures tomorrow when it's daylight and attach them.

 

[Gavin A]

That's a variation on a fairly standard swimming pool solar water heating set up for outdoor swimming pools, so it should work to some extent, though it's efficiency will drop off rapidly as the air temperature drops due to the total lack of insulation.

I'd definitely invest in at least a basic solar water heating controller to prevent the system running when the pipes cooler than the pool, but personally I'd go for a slightly better one that varies the pump speed to maintain a reasonable temperature difference though the collector.

 

[Worcester]

Have a look at what David Nicholson Cole has done here with the Surya Sunbox Charging the Earth - Solar! to maximise performance of a home made solar thermal heating system

 

[Marvo]

Thanks for the input. Wow, that guy went to town with his Surya sunbox, I'm working on a fraction of his budget but have the advantage of lunchtime temperatures between mid 20's to early 30's in spring and autumn and pretty much guaranteed sunshine most days. Hopefully the heat input of direct sunshine will be sufficient not to require the pipework collectors to be glass covered or insulated.

I also looked at solar controllers but again unfortunately nothing was within budget. I will probably just run the pump for 2-3 hours per day in the early afternoon and might put a standard thermostat in the mix to override if the water temp is already warm enough.