Fixing the division between Solar Water Pasteurization (heat) and Solar Water Disinfection (UV)
by Vinay Gupta • September 5, 2007 • Hexayurt • 0 Comments
Here it is.
Now, what this is, you see, is a tube that looks a lot like a fluorescent light tube.
But, actually, it’s double walled. The inside wall is black, the outside wall is clear, and there’s a vacuum between the two. It’s a big flask, but clear rather than being either silvered or made of stainless steel.
Here’s how it works.
Energy from the sun falls as photons. They pass straight through the clear glass outside tube, then hit the black surface, and get turned into heat – vibrating atoms. The vibrating atoms can’t pass their vibration on to neighboring atoms because of the vacuum. there are simple no atoms to vibrate.
So the heat that fell from the sky is now trapped inside of the tube, and it can’t get out, except by black body radiation – some infrared is emitted by the tube.
But if the tube was surrounded by a partial reflector, which concentrated the sun, and also reflected back that heat, this might be an absurdly efficient energy collection device.
So, that’s the tube as it stands.
Here is the refinement for water purification purposes.
Now, here’s the kicker. Glass can be adjusted in many aspects. One of them is the amount of UV light which will pass through the glass. So if somebody can make a glass which absorbs visible light but lets UV light straight through, it should now be possible to create a highly efficient solar water purification system which combines the UV purification of SODIS and the pasteurization of Solar Water Pasteurization.
Now, glass is delicate, and this sounds expensive, but it might be one of those things which produced by the mile of product is fairly cheap. And these units would last until broken.
Interesting. Heeger’s solar panels may make all this academic (think UV leds in a world with nearly-free electrical power anywhere there is daylight) but that does not mean this is not worth thinking about.