Optical Rectenna

On 9/5/08, sailor.barsoom wrote:
(...)
> I just started reading about these today. If they can be made to
> work, they might be over 80% efficient at converting sunlight to
> electricity (similar efficiency to the microwave rectennas we all know
> and love).
>
> This beats the snot out of PV, which hovers around 30% and hits 40% in
> labs. This means a powersat could be smaller. And lighter?
(...)

Yes. Optical rectennas would be in the nanometer scale AFAIR, and thus
the collector surface could in principle be incredibly thin and light.
Perhaps an "optenna" powersat would be something like a umbrella with
the supporting beams holding in place a "sail" of optenna film.

Of course, as you said, if that works. Some preliminary tests with
optennas using infrared showed up efficiencies of just around 1%, so
in practice it may be difficult to achieve the high efficiencies
predicted by theory.