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Solar balloons are made out of black, sunlight absorbing material that gets warm in sunlight. The air inside the balloon therefore gets hot and the balloon rises.
I propose a giant balloon of this type, on the end of a tether wound round a drum. As the balloon rises, the drum will rotate and generate
electricity. When the tether runs out, a vent at the top of the balloon is opened and the balloon comes down again. Repeat until mechanical breadown.
Why is this better than a solar panel? Because it can cover a large area cheaply. Solar panels cost tens of thousands just for the roof of a house. The same money spent on mass produced solar ballon generators could cover many acres.
Solar balloon
http://pagesperso-o...olaire/en-index.htm
for those who haven't seen them before. [Bad Jim, Feb 12 2009]
Stirling engines
http://en.wikipedia...iki/Stirling_engine
clearing up a little confusion [Bad Jim, Feb 13 2009]
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Annotation:
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How will the tether rewind while the ballon deflates? Is some kind of spring involved? It might be easier to have multiple balloons on a giant, ferris-wheel-like arrangement. |
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Dealing with the valves might also be interesting. The ballons aren't going to deflate with a whoosh. |
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I was imagining a spring on the drum. The ferris wheel arrangement would have to be rather large which might drive the cost up. |
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I recognise that the balloons won't deflate very quickly, but it might also take 20 minutes or more for the sun to warm the balloon up. So I don't think deflation time will be a big factor. |
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This is effectively just an innefficient solar powered stirling engine. |
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How about you use an efficeint solar powered stirling engine, instead? |
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You could have two balloons connected via a pulley arrangement as counterweights to each other (or would "counterlifts" be a better word). This way the two can see-saw as one of them lifts and the other descends. The generator could be fitted to the axis of one of the pulleys. |
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In addition, the balloons could have one white and one black hemisphere, and be able to rotate to have one of them facing the sun. When the black hemisphere is facing the sun, the balloon is warming and the balloon lifts; when the white side is facing the sun, the balloon cools down, and starts descending. |
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Yes, it would be less efficient than a Stirling engine, and entirely unusable in windy conditions, but you would have two huge balloons bobbing up and down, and that's fun to look at. |
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//It might be easier to have multiple balloons on a giant, ferris-wheel-like arrangement// Sounds awfully like a Hullaballoon. |
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// Cheap yet effective // |
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-> not in the common meaning of 'low_$/high_Watt' but in the meaning of 'constructable at no cost from scrap material, to power an LED' [+] |
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//This is effectively just an inefficient solar powered stirling engine.// |
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No it isn't. A Stirling engine uses a fixed quantity of gas sealed within the unit. This balloon would let a little hot air escape at its' peak and reinflate on the way down. |
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//How about you use an efficient solar powered stirling engine, instead?// |
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In fact such things do exist. On the Wikipedia page for Stirling engines there is a picture of a solar reflector with a Stirling engine at its' focal point. I'm not sure how much they cost, but I suspect its still the same sort of price as for reflecting onto panels. |
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