h a l f b a k e r yOn the one hand, true. On the other hand, bollocks.
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Fan run by bicycle (or electric fan if available) sits on hot
road or sand and fills the balloon.
[link]
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I get why you'd want to use air from the hot road
to fill a balloon, but why sand? |
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Also, you might not need the fan. Just hold the
balloon open over the hot road and wait. A fan
would pull air in faster than it can be heated, and
you'd wind up with a tepid balloon. |
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I like the idea. It would be quite fun to take an
enormously large sheet of transparent plastic,
weight it at the edges, and lay it on a road before
the sun came up. |
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Traffic would be an issue. |
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Collecting the hot air would also be an issue. You could make a (slightly raised) hole in the centre of [Max]'s sheet of plastic, from which the air would issue, and squat the balloon over it. Or provide an inverted funnel of film beneath the balloon to act as a scoop; that way you could periodically refuel by hovering over a road. |
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Logic suggests that, short of a large expanse of plastic covering the road (like a solar tower with only a stub of a tower), you will only be able to harvest energy from an area about equal to that of the balloon; this would then be less effective than a solar hot air balloon, which can collect heat continuously, rather than only prior to take-off or at very low altitudes. It might therefore be best as a booster for a solar balloon. |
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correcting according to [spider mother]'s suggestion. |
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Max's anno is because originally the idea read:
Use air from top of boiling road or sand to fill balloon. |
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Why fill a balloon with sand? Good question. |
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I don't think traffic would be a problem. You can
always find a large empty parking lot or unused dead
end road outside town during the heat of day. |
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I have been sterilising a patch of ground using black plastic covered with sheets of glass, with a small air gap between glass and plastic. I've measured the temperature of the plastic at about 98ºC, when the general air temperature was only in the high 20s; and I didn't even bother getting everything nicely flat and sealed at the edges. That's easily hot enough to float a hot air balloon. Moral: this idea seems feasible. |
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