Are solar-powered aircraft possible?

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Michael Whalley

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Are solar-powered aircraft possible?
« on: 01/12/2009 22:30:03 »
Michael Whalley  asked the Naked Scientists:
   
Hi there,

Recently I read about the NASA Helios - a pilot-less aircraft powered entirely by solar power.

If you could fly such an aircraft to an altitude higher than the clouds, could this aircraft fly forever using just the power of the Sun? And could it be scaled up to create an aircraft capable of carrying people and cargo long distances using no fuel at all?

Cheers

David from Northamptonshire

What do you think?

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Offline Karsten

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Are solar-powered aircraft possible?
« Reply #1 on: 02/12/2009 01:18:45 »
We are getting there.

Currently the record in air time is at 56 hours.

http://www.airforce-technology.com/projects/zephyr/
"During daylight hours the air vehicle is solar powered. The upper surface of the aircraft wings are covered by amorphous silicon arrays developed and supplied by United Solar Ovonic. At night the air vehicle is powered by lithium sulphur batteries, supplied by Sion Power, that are recharged during daylight hours by the solar power arrays."

Scale it up? There is one solar powered piloted plane I thought I saw in a museum in Munich Germany, I looked similar to this:
http://www.psfk.com/2009/03/sunseeker-ii-a-manned-solar-powered-aircraft.html
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Offline LeeE

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Are solar-powered aircraft possible?
« Reply #2 on: 02/12/2009 04:19:25 »
Quote
And could it be scaled up to create an aircraft capable of carrying people and cargo long distances using no fuel at all?

Nope.

Have a read of http://en.wikipedia.org/wiki/Helios_Prototype

You'll see that it flies at between 15 and 25 mph and the pictures show how fragile it was (especially the sequence that shows the final model breaking up).
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline techmind

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Are solar-powered aircraft possible?
« Reply #3 on: 03/12/2009 23:36:42 »
One way to answer this question is just to consider "energy".

What is the effective crusing power of (say) the pair of engines in a Boeing 737 (in kilowatts)?

(Wikipedia says the crusing thrust is about 21kN per engine... but how from that to power?)

What is the available solar energy if you covered the top-side of the plane in solar cells?
Solar energy being 700-1000watts per square metre, and solar cells being 12-18% efficient typically (research cells now approaching 40% efficiency but not commercially viable). What's the top-surface area of a 737 ?


Can anyone else fill in some figures?

I think the answer will show that airline travel in a form similar to what we are accustomed to is simply not possible (by a very large margin) with solar power alone.

(If only customers weighing 70kg and under were allowed, and no baggage ... then that might help, but even so I think it's a long way off, and the plane would have to look very different.)
« Last Edit: 03/12/2009 23:38:21 by techmind »
"It has been said that the primary function of schools is to impart enough facts to make children stop asking questions. Some, with whom the schools do not succeed, become scientists." - Schmidt-Nielsen "Memoirs of a curious scientist"

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Offline Karsten

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Are solar-powered aircraft possible?
« Reply #4 on: 04/12/2009 01:10:36 »
... and the plane would have to look very different.)

That makes me think...

Of course the above comments are considering heavier-than-air aircraft and maybe this was assumed in the original post as well. However, a lighter-than-air vehicle, such as an airship could be powered by solar power alone. It could be maneuvered with electric motors that are powered by solar cells covering the airship body. That would work nicely above the clouds. Batteries would be heavy though and reduce passenger capacity. It could even be filled with hydrogen created by solar power. Don't know about helium though. Don't know how it is made. 

Just a thought.
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