Power for Settlements

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Power for Lunar Settlements

Here are some considerations for the power systems used in our lunar settlement stories.

Solar Power

The best available source for power on the Moon is the Sun. Solar is particularly inviting in the polar regions where mountain tops are available that have solar views 75% to 99% of the time. The sun light is not diminished by an atmosphere and is never blocked by clouds. It is harsh and unrelenting.

From the surface of the Moon, the Sun appears to move slowly across the sky making a full cycle every 29 days. On rare occasions it is eclipsed by the Earth for a few minutes.

At the poles, the Sun simply circles the sky very near the horizon. At its lowest point it may be blocked by mountain tops. Other times it may be blocked by local instillations such as other power collectors.

Near the lunar equator, the Sun is visible only one half the time. The 14 day lunar nights are a major problem for power generation and are a major factor in setting a polar location for the first lunar settlement.

Solar power can be captured either by focusing it on a target with a mirror or by using photovoltaic arrays. Either way, the tracking requirement is very easy compared to Earth.

Dumping Heat

One of the hardest things to do on the Moon is get rid of large amounts of waste heat. In any power generation system you must have both a source power and a sink for waste heat. This is basic thermodynamics and there is no way out of this requirement. Most space missions simply dump waste heat to deep space. On the surface of the Moon, this is not so simple. Half of your view is exposed to the cold of deep space, with the complication of a hot spot Sun and a warm spot Earth. The other have of your views sees the surface of the Moon itself. At the pole the average lunar surface temperature will be around 0 C and does not change drastically during the day. Here simple hear radiators can be used as they only need to avoid exposure to a slow moving Sun.

At the equator there is a completely different story. The surface of the Moon raises to about 200 C by mid lunar day. It will be very difficult to dump waste heat at this time, so it will be difficult to keep the living areas cool and do major industrial operations. Equatorial housing may need to be buried extra deep for thermal reasons.

Big Battery Power

There are at least three separate technologies promising a times-ten improvement in rechargeable batteries currently demonstrated in the laboratory. They are all based on some version of the super capacitor. The value of such a battery for electric cars on Earth alone will be in the hundreds of billions. The only problem is developing mass production techniques. The race is on.

By the time of our stories, it is reasonable to expect really good batteries will be available for use in space. These will give a lunar rover a range of at least 500 kilometers. They will also be able to power reasonable amounts of electronics and modest life support equipment through a 14 Earth day lunar night. They will not allow large industrial operations for this length of time.

Nuclear Power

During early stages of lunar exploration, some instruments can be powered by Radioisotope Power Generators (RPG). These devices provide only about 100 watts and are difficult to come by. The short lived radioisotopes needed to make them are manufactured at only a few places on Earth and only in small amounts.

In the long term it may be necessary to establish small nuclear power stations on the Moon, particularly in non-polar locations. These will mainly provide power during the long lunar night. Their daylight operation will be limited by their ability to dump waste heat. They will be expensive to build and difficult to maintain.

Story Power

In our stories, solar will be the major power source. RPGs can be used for small science stations. Big batteries may be used for electronics and life support.

Stories set some what farther in the future, may have nuclear power stations. It is reasonable to assume that if Helium 3 from the Moon is an important element of Earth side power generation, then small safe lunar nuclear power plants are a likely possibility.