Moon Base Power

If we ever establish a base on the moon, we are going to need power, and for the projects I have in mind we are going to quite a bit of power. There are numerous ways to generate electricity: steam engines driving generators, nuclear power and solar power using solar cells are some of the ways we use. Solar cells are a popular method for inner solar system space exploration. There is lots of sunlight and solar cells do not weight very much, relative to the amount of power they generate. Nuclear power has been used for some satellites, though it has fallen out of favor due to environmental concerns. It is still a viable choice for unmanned deep space probes. Steam driven power generation is used on Earth because we have an atmosphere that supplies the oxygen needed for the fires under the boilers (steam generators in modern power plant lingo). Burning fossil fuels on the moon is probably not going to work because there is no atmosphere. There probably isn't any fossil fuel either, but you never know. The moon might be made of coal instead of green cheese. Of course, if we do find coal or oil on the moon, we are going to have to reconsider the appelation "fossil fuel".

I do not like solar cells because they are exposed to all the hazards of space: radiation and impacts from micrometeorites. Because of this solar cells have a relatively short life span, ten years maybe in Earth orbit, considerably less on the moon. On the moon, you are outside of the protection provided by the Earth's magnetic fields.

I prefer the idea of a steam driven generator set. Sunlight would be concentrated by mirrors and directed to a steam generator. The steam would drive a turbine which would in turn drive a generator. Very well understood technology here on Earth.

The steam generator and the power plant would be located under ground for protection from radiation and meteors. Sunlight would be collected from a large bowl lined with mirrors and directed thru a tunnel, either horizontal or vertical, to the steam generator.

I envision using robotic machines to do the excavation and some of the installation of this power plant. If we could devise a way to make flat surfaces from medium size rocks, they could be used for crude mirrors. The flatter they could be made, the better. Slate would be nice, but I doubt we will find any on the moon. They could even be spray painted with a metallic silver for better reflectivity. Anything we can build on the moon from materials we find there is mass we do not have to boost from Earth. Mylar mirrors would not have much mass, not much more than paint, but their life expectancy would not be that great. So I like rocks.

Unless we build this power plant at one of the poles of the moon, it is going to be exposed to sunlight for two weeks and in darkness for two weeks. Building a power station at one of the poles that would be constantly exposed to the sun could be a bit of a trick, and that might not be the where we will need the power. So we should plan for two weeks of light and two weeks of darkness.

One way to maintain power during times of darkness would be to have several power plants installed at different longitudes around the moon. Cables could be run to connect the plants, and so power would be available at all times all around the moon, at least at the same latitude as the power plants. Unfortunately, we would need thousands of miles of cables, and cables would have to be shipped from Earth, at least to begin with, and that would be expensive.

Other ways would mean storing power someway. Batteries and flywheels are possibilities. Both are heavy. Using electricity to generate chemicals that could later be recombined (burned, perhaps) to generate energy is another way, though probably less efficient. And then there is always nuclear power, which has a whole slew of problems, but might on balance prove to be the simplest solution.

In any case, I still like the idea of a solar driven steam generator. On Earth a day is only 24 hours long, so such an installation has to have a method of tracking the sun as it moves across the sky. On the moon, a day is two weeks long. You still need a method of tracking the sun, but it does not have to be quite so quick. So I imagine robotic machines going from one rock mirror to the next, giving each one a little tweak to adjust its' angle. By the time it gets done with each of the several hundred mirrors, it will be time to start over. When the sun goes down, it will make one last pass to repoint the mirrors toward where the sun will be when it comes up in two weeks, and then it can go to sleep until the sun comes up again.