Solar Power Satellites

--- bobunf wrote:
> I estimated that the total energy cost for all of
> this would be about
> 39 megawatts (1300 watts/m2 * 10^7 meters of solar
> arrays * 30% solar
> cell efficiency * 1%).

I have seen this assumption a few times before, not
just from bobunf - that a solar power satellite would
be using photovoltaic arrays. This is incorrect.

The bulk of a solar power satellite would most likely
be a sheet of aluminum foil. Inflatable ribs would
hold that sheet in a paraboloid shape. This giant
reflector would focus sunlight onto a boiler, which
would heat a working fluid, and thus drive a
turbine/generator combination. This would be a Carnot
cycle heat engine. The hot side could get arbitrarily
hot, the cold side would be in the shadow of the
reflector, and thus not much more than the 3 Kelvin
cosmic background. If the hot side is a mere 300
Kelvin, then the efficiency of the system would be 99%
(less frictional losses).

Ed