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Old 04-24-2012
Frogwatch Frogwatch is offline
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Solar chimney

Here is an idea I will try to make for sailing. In hot weather with no shore power, staying on your boat can be miserable if there is no wind to allow a windscoop to be used. Any air flow thru the boat can make all the diff in whether you use her or not.
So, I want to build a "solar chimney" that will mount on a forward hatch. The bottom half will be either white fabric or even silvered reflective fabric and the top will be transparent material to pass the IR sunlight. Inside this upper part will also be a concentric black absorber. The top part would be raised using the forward halyard and it would have a conical cap to prevent rain from falling in it.
Sunlight will heat the air in this upper part causing it to rise producing a draft in the boat.
The trick will be to maximize the thermal differential between the top and bottom parts. Minimizing heating in the bottom is easy with silvery or white fabric. Getting good heating of the top part is harder. I'd probably make half of it silvered to reflect heat back into it while the front half is transparent. However, I am not sure I need the heat absorber to make maximum contact with the air to get good heating or if sunlight heating the air directly will do it.

I'll begin experimenting when I finish working on my super efficient solar still for making fresh water.
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