From: utzoo!decvax!pur-ee!CSvax:Physics:piner
Newsgroups: net.space
Title: solar power on the moon.
Article-I.D.: pur-phy.483
Posted: Sat Sep 18 16:40:01 1982
Received: Wed Sep 22 07:57:18 1982

There has been some debate on solar power going on, and I
would like to add my two cents worth. There are several methods
of getting useful energy from sun light on the moon. I 
will discuss only two.
1) Solar cells.
  These cells produce electrical power directly when exposed to
light. Very nice, but there are problems. Well, on the moon
those problems are much easier to overcome. First, directing
the cells towards the sun. The sun moves much more slowly 
across the "sky" than on earth. The mass of the cells is the
same, but the weight is much less. So their support system
can be built much lighter than would be required on earth.
Hence, incredibly small motors can do the task. Indeed,
motors may not be needed at all. Since there is no atmosphere
very large temperature gradients are possible due to the
solar radiation. Mechanical systems using bimetal strips
can be designed to point the cells at any source of radiant
heat. Thus no energy is used and the alignment is automatic.
A side note, some cars use bimetal strips on the engines.
On my car, a bimetal strip is linked to the choke and
mounted on the manifold. When the manifold gets hot, the
strip changes shape and pulls the choke off. Such systems
are simple, cheap, and require no logic (other than that
used by the designer). Furthermore, since there is no
atmosphere, you get the full power of the sun as soon
as it comes over the horizon. On earth, the best you can
do is about 25 percent and that is only at noon. The
other problem is storage. I did some simple calculations
and found that the moon has a circumference of 6800 miles.
If we are talking about putting a lot of people on the
moon, say 100 million or so, one could justify building
a superconducting power line around the moon. Bury the
cables deep, and they could be kept cold for a fraction
of the cost required on earth, and you only lose power
during elcipses. Such a project is a large one, but
no bigger than current earth bound projects such as
the Siberian pipe line. This brings me to my second
proposal.
2) Thermoelectric power.
The temperature difference from one side of the moon to
the other is huge. If you build a thermalcouple around
it's circumference electrical power could be generated
directly on a continuous basis. Such a system is
incredibly simple. A lot of wire, and not much else.
Such systems can be used on a local basis too, one
side in light, the other side in shade. But then you
only have power during light. An only for a fixed
system. In any case, if we are talking about a large
number of peole on the moon, then solar power is
the way to go. The first colony however will probably
have to depend on nuclear power, because you have to
start somewhere, and nuclear power plants have fairly
high energy densities, in other words, if you have to
ship fuel to the moon, nuclear is the cheapest. If you
want to generate power from what the moon has to offer,
solar is the best bet.