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From: dietz@SLB-DOLL.CSNET (Paul Dietz)
Newsgroups: net.space
Subject: Solar energy
Message-ID: <8603121751.AA04350@s1-b.arpa>
Date: Wed, 12-Mar-86 11:38:14 EST
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Posted: Wed Mar 12 11:38:14 1986
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> A few tidbits I've picked up on solar energy, taken from "The
> Health Hazards of NOT Going Nuclear", by Petr Beckman.
> At best, the concentration of solar energy is 1 kilowatt per
> square meter.  Current solar technology is about 10% efficient,
> theoritical maximum efficiency is 22%.  Allowing a 50% spacing
> between solar collectors to allow for repair and shadows, and you
> have a solar power plant 50 square miles big to generate 1000
> megawatts of power.  I'm quite sure that even if a fusion reactor
> needs an Astrodome to fit in, that it will not span 50 square miles.

Some corrections:

(1) One kilowatt per square meter is for *ground based* solar power
(at noon). Power satellites would transmit microwaves that could be
converted to electricity much more efficiently, so less land would be
used (and the rectifying antennas would be made of mesh so crops or
animals could be grown/grazed underneath).  Even without powersats,
ground based light collectors can be made more effective with orbital
mirrors (but the spot size of the reflection is large, so this doesn't
work on a small scale).

(2) The best current solar cells are much better than 10% efficient (but
are expensive), and solar-thermal systems (in which concentrated sunlight
heats a fluid that drives a heat engine) can be as efficient as
conventional power plants.  The 22% efficiency is for silicon cells, I
think; GaAs cells can be more efficient.

The problem with nuclear power now seems to be the extra capital investment
needed to build a nuclear plant offsets the savings in fuel costs, and
the complexity of nuclear plants makes them unreliable.