Harvesting solar power in space and sending it back to Earth

Re:Harvesting solar power in space and sending it back to Earth by Gravityloss on Thursday August 29, 2013 @06:50AM (#6295169)

Quite unintuitively, you can't really focus light from the sun to a long distance, since the sun is not a point source.

Basically, you can't exceed the power per steradian of the sun with mirrors. So you would have to fill a large portion of the receiving end's sky to transmit any real power. Which means the mirrors would have to be really close (like they are in heliostats) or if they're far away, they would have to be really huge.

Does not work.

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Re:Harvesting solar power in space and sending it back to Earth by schiffern on Thursday August 29, 2013 @06:10PM (#6298949)

>Basically, you can't exceed the power per steradian of the sun with mirrors.

This is something I've wondered about. It seems like one should be able to make a counterexample by focusing an enormous area on a tiny one. Is it just because due to "fuzzy focus," the concentrated focus volume unavoidably grows as the mirror size grows?

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