Fan run by bicycle (or electric fan if available) sits on hot road or sand and fills the balloon.
-- pashute, Nov 06 2011

I get why you'd want to use air from the hot road to fill a balloon, but why sand?

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.

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.

Traffic would be an issue.
-- MaxwellBuchanan, Nov 06 2011


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.

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.
-- spidermother, Nov 06 2011


correcting according to [spider mother]'s suggestion.

Max's anno is because originally the idea read: Use air from top of boiling road or sand to fill balloon.

Why fill a balloon with sand? Good question.

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.
-- pashute, Nov 06 2011


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.
-- spidermother, Nov 06 2011



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