Method of storing energy on the Moon

[some bloke]

If I were to try and create a system which guarantees power for a moon-base, I would look at building a rail system around the moon on which to transport solar panels.

The moon has an equatorial circumference of 10917km, and rotates once every 29.5 days, which equates to just under 15.5km/h, to have a carriage running around the equator and staying in the centre of daytime. There are over a million miles of train tracks on earth, so 11,000km (just under 7000 miles) is not an unachievable distance, especially if it can be made out of local materials. Alternatively, a road could be flattened on the surface, to give it something to run on which is relatively flat, and the panels could just roll on all-terrain tyres.

It wouldn't be difficult for a solar panel vehicle to power itself to 15.5km/h and still have energy to spare, especially on rails (As momentum would be constant, it only needs to overcome resistance once it's to speed - maglev would be ideal, but unlikely to come from local materials!)

Have the rail system able to send power back (like a model train in reverse) and the stationary colony can have power all day and all night without needing to store it.

(this would also be a good premise for sci-fi!)

 

[berkeman]

If I were to try and create a system which guarantees power for a moon-base, I would look at building a rail system around the moon on which to transport solar panels.

That's a clever idea, but you would probably need to build in some sort of redundancy and repair capability in order to deal with meteorite damage. Perhaps two parallel tracks separated by 50m or so, and the ability for each to power repair vehicles on the other track. That way when one track is damaged and that solar panel train/vehicle stalls, the repair vehicles can still get power from the other track.

I have no idea what the probabilities are for meteor impacts of different sizes versus time on the Moon, but I'm sure there are some papers that describe those probabilities.

https://www.google.com/search?q=moo...UZGJLMDhjUFN1Y00YADABGAcgyuLO-w9KCBABGAEgASgB

 

[some bloke]

That's a clever idea, but you would probably need to build in some sort of redundancy and repair capability in order to deal with meteorite damage. Perhaps two parallel tracks separated by 50m or so, and the ability for each to power repair vehicles on the other track. That way when one track is damaged and that solar panel train/vehicle stalls, the repair vehicles can still get power from the other track.

I have no idea what the probabilities are for meteor impacts of different sizes versus time on the Moon, but I'm sure there are some papers that describe those probabilities.

I believe that the moon doesn't get hit that often, I think (and I could be wrong) that it just doesn't have any way to recover from impact - no weather to erode, no life to grow. So we're seeing a complete history of when the moon got hit by rocks.

If there were significant risk of meteoric impacts, I would instead go for making a road system and having automated vehicles to follow it. Not sure how the power could be transferred though - maybe a cable system like trams use.

If the road were damaged, the solar vehicles could go around it using off-road capabilities, and then reconnect. Meteor damage to the cables might be a risk, but I don't know how much of one!

 

[Ken Fabian]

I suspect 2 tilt tracking solar farms on high ground (or 3 fixed) and cabling would require less materials, equipment, construction and maintenance than a railway. Very uneven terrrain, a lot of going around craters and boulder fields.

Cabling that long and able to work in the extremes of heat and cold presents major challenge. With 3 solar farms you could cut a third or more off the cabling - but not the railway if it is carrying the solar farm. The moving solar farm still needs cabling in addition. The more I think about it the more problems emerge.

1 solar farm locally with enough batteries would be easier (a relative term). A lot easier.

You would need an exceptionally profitable commercial reason - far beyond the need for powering a research base day and night - for a moon circling railroad to make any sense.

 

[Baluncore]

Cabling that long and able to work in the extremes of heat and cold presents major challenge. With 3 solar farms you could cut a third or more off the cabling - but not the railway if it is carrying the solar farm.

Yes, but not circling the lunar equator.
Lunar libration of about 10° would require the cable cover 190° longitude of the 80° line of latitude. That defines the optimum (latitude, longitude) of the three solar farms.
They are: A( 80°, -5° ), B( 80°, +5° ), C( 80°, 180° ).

The shortest power line connecting those three farms, all at a latitude of 80°, would be a radial network, having a Y shaped topology, with the long straight stem reaching over the pole, all meeting at a 120° angle close to the two closest farms.

Power at the pole would be convenient since that is where water is expected. The pole also gives maximum radiative cooling to keep electronics cool, and hopefully to keep the over-pole power line superconducting.

 

[sophiecentaur]

Or - of course, if you find a lava tube, that works better.

Shame but I'd guess that lava tubes would be very few and far between. Also, are we sure that they would form in the same way that they form under full gravity. Maybe volcanoes would be higher and that could make the flows very different and the lava could solidify quicker (or slower).

 

[Baluncore]

From time to time 'they' suggest projects for supplying Earth with energy from solar satellites. I always see downsides to that. But a similar system of orbiting solar satellites around the Moon could do the same job with some huge advantages; the Lunar Night is long but two or three equatorial satellites could maintain solar power input although probably not in synchronous orbits ( one month period).

The biggest advantage of lunar satellites would be the lack of an atmosphere, so the orbit could be very low. The orbital period could be a few minutes less than 2 hours. In an equatorial orbit, that would give plenty of opportunities to store and dump energy. One hour in the sunlight, one hour in the dark.

 

[Filip Larsen]

The biggest advantage of lunar satellites would be the lack of an atmosphere, so the orbit could be very low. The orbital period could be a few minutes less than 2 hours. In an equatorial orbit, that would give plenty of opportunities to store and dump energy.

Only a selected few inclinations in so-called frozen orbits (due to Lunar local mass concentrations) are considered long term stable, namely around inclination 27°, 50°, 76°, and 86°, so a low equatorial Lunar orbit will likely not be stable and require significant station keeping fuel. However, the near polar orbit should be fine in this regards and also have the added benefit of being in full Solar illumination for some days twice a month.

 

[sophiecentaur]

opportunities to store and dump energy.

Thing is, there's a massive constant supply of solar energy so storage may not actually be necessary. The bigger picture would need to be considered; I can safely say that the population and transport will always be much less than for an Earth situation.

You'd have to compare the cost of storing the energy (and where?- in orbit or on the ground) and just having more satellites to fill in the gaps (re-transmitting to the ground efficiently is also an issue). You'd need materials, however you do it but launching lunar satellites would be easier. Each satellite in a group could target ground stations in turn on the way round.