How, and How Not, to Heat a Swimming Pool Using the Sun
Soundtrack or no soundtrack, who’d have thought that watching water boil could be so interesting? There’s something endearingly geeky about the folks at Green Power Science – from their impressive demonstrations of flash cooking using Fresnel lenses, or their mad scientist solar conversions of giant satellite dishes, through to their somewhat off-the-wall DIY solar space heater using old campaign signs. And if their hits on YouTube are anything to go by, they’re getting quite a following. In this latest episode, Dan Rojas explores whether it is possible to heat a pool using a Fresnel lense – for those who can’t watch video online, click below the fold for the answer, as well as some links to further cool DIY solar projects.
Essentially, the simple answer is that it’s not possible to heat water with a Fresnel lens directly, because light passes through water. But as Dan demonstrates, by placing a dark object within water, you can focus sunlight with the lens onto that object to act as a heat sink. Dan goes on to explain that you may well be better off simply painting the floor, or parts of the floor, of your pool black – as long as this area is the same size as the Fresnel lens, it will generate the same amount of heat.