Method of storing energy on the Moon

[Al_]

TL;DR

This article: https://phys.org/news/2026-01-lunar-nights-martian-storms-batteries.html says batteries are problematic in space. I propose a flywheel.

Batteries bad

The article linked above says batteries are problematic in space. I propose a flywheel, which is suited to the Lunar environment. 1) It is in vacuum already. 2) Magnetic suspension is less demanding in 1/6 gravity. 3) Superconductors need very low temperatures which are easily available 4) Craters provide ready-made disintegration safety containers 5) Local resources can be used to manufacture parts on the moon, e.g. spun basalt fiber has high tensile strength. 6) The device's performance will not degrade as quickly as a battery 7) It can store power for the duration of the Lunar night with minimal loss

 

[jrmichler]

Some points to consider before you get too excited:

1) Thermal cycling also kills motor/generators. I once headed a motor reliability project. The primary cause of failure was thermal cycling. If the energy storage is underground or inside a thermally insulated structure, thermal cycling will be minimal.

2) Estimate the cost to store a realistic amount of energy. A starting assumption is that you need to store enough to supply 100 kW for 3 weeks. That's 50 megawatt-hours. Calculate the mass and cost of batteries to store that much, then the mass and cost of a flywheel energy storage system. Note that the cost is the cost of a system installed and running on the moon. And that the mass is the system mass, not just the mass of the spinning rotor or battery cells.

3) Any concept that requires manufacturing on another planet must include the cost, energy requirements, and mass of the manufacturing plant that is shipped to that planet.

It is not a trivial problem.

 

[Rive]

Superconductors need very low temperatures which are easily available

One of the problems is thermal cycling. Superconductors are just about a different temperature window than batteries, but it's still a window.

Local resources can be used to manufacture parts on the moon, e.g. spun basalt fiber has high tensile strength.

I can assure you that local manufacturing of that kind of inertial mass would be a real nightmare.

I won't say that it's not possible or that there are no circumstances what would make this practical, but not in any close future.

 

[A.T.]

Local resources can be used to manufacture parts on the moon, e.g. spun basalt fiber has high tensile strength.

If you gonna start digging, then you can just as well bury batteries underground, to reduce the temperature variations and radiation that cause their problems.

 

[Baluncore]

5) Local resources can be used to manufacture parts on the moon, e.g. spun basalt fiber has high tensile strength.

Solar energy can make rock wool from basalt on the moon. Make a rock wool blanket that weighs in at about 10 psi. Inflate it with 80% N₂ and 20% O₂ gas to keep the blanket floating above the equipment. You then have thermal convection for cooling during the 350 hours of day, and warm batteries for the 350 hours of night. Your engineers can live in comfort, playing extraordinary cricket in the covered crater.

 

[Ken Fabian]

Making anything complex and technically demanding out of moon resources is going to require large pre-investments in infrastructure and equipment. A whole lot of pre-planning and testing too; few factories doing novel things in difficult conditions work perfectly first go.

Seems like in-situ resources are more of a longer term goal than an initial setup for a moon base - perhaps one of the goals would be to demonstrate at small, demo scales that mining, refining, manufacturing things out of local materials is possible. I'm not convinced that any significant dependence on local resource use will be feasible or economically viable; such a base would be much more a demonstration of Earth's abundance than a demonstration of the moon's economic potential.

For all that weeks of energy storage seems a lot I suspect batteries will do it a lot better than flywheels, you just need to accept that you need a lot. Without the in-situ materials would flywheel systems mean shipping lower mass than with batteries? I suspect not. Batteries can be shipped as modular components. Not sure flywheels can.

Any habitat intended for people will have controlled temperature and atmosphere and include room for batteries. Very high grade thermal insulation will likely mean cooling rather than heating is the issue, even during the long cold nights.

 

[Baluncore]

Very high grade thermal insulation will likely mean cooling rather than heating is the issue, even during the long cold nights.

The temperature, a couple of metres below the lunar surface, is stable between lunar days and nights, fortnights. That deeper temperature ranges from -20°C to -40°C (-4°F to -40°F) in equatorial and mid-latitude regions.

Batteries will need to be kept warm.
10 psi of rock wool overhead should be sufficient to keep the day-night temperature stable inside the habitat.

Heat can be removed from the living space by reducing the thermal carpet in the basement. By supporting an atmosphere, and circulating that through underground heat exchanging boreholes, there will be a greater capacity to dispose of heat, into a greater volume of the Moon rock.