# Cheapest, easiest solar cell manufacturing methods on the Moon

Whipley Snidelash
TL;DR Summary
Would it be feasible to automate silicon solar cell manufacturing, assuming efficiency is not relevant, on the moon?
If I wanted to create a factory, possibly automated, on the moon using materials from the surface to create silicon solar cells how hard would it be? Considering the environment, the cheapest and simplest solar cell, regardless of efficiency, would be what to use because quantity and area of deployment would be almost unlimited. My understanding is that there is an abundance of silicon, aluminum and titanium on the surface.

Gold Member
Summary:: Would it be feasible to automate silicon solar cell manufacturing, assuming efficiency is not relevant, on the moon?

If I wanted to create a factory, possibly automated, on the moon using materials from the surface to create silicon solar cells how hard would it be? Considering the environment, the cheapest and simplest solar cell, regardless of efficiency, would be what to use because quantity and area of deployment would be almost unlimited. My understanding is that there is an abundance of silicon, aluminum and titanium on the surface.
I think it would be.

From wikipedia on "Self-replicating machine"; "The future development of such technology is an integral part of several plans involving the mining of moons and asteroid belts for ore and other materials, the creation of lunar factories, and even the construction of solar power satellites in space."

I think it would be fun to go through the process and figure out how long it would take to have such machines cover the entire moon with solar panels.

According to my always suspicous maths, if the replicants could each produce 1 offspring a day, then a 1 square meter seed panel and it's offspring could cover the moon in only 46 days.

Anyways, this would be a fun project.

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Late entry edit: Welcome to PhysicsForums!

Gold Member
Are we running out of sand, on Earth ?

Or you mean made off-planet for off-planet use (in which case yes, until we get around to mining asteroids). Making stuff on the Moon would save a small fortune, compared with all the gas it takes to lug stuff out of Earth's gravity well.

Whipley Snidelash
Yes, I mean creating solar power for use on the moon not exporting the panels here.

Whipley Snidelash
I’m not sure what Musk’s exact plans are but he should be looking at the moon to colonize first not Mars. The salvation of this planet could be the moon if anyone had brains enough to see it.

Summary:: Would it be feasible to automate silicon solar cell manufacturing, assuming efficiency is not relevant, on the moon?
Yes it is possible. But at what point does it become economic to manufacture locally rather than transport from the Earth to the Moon.
My understanding is that there is an abundance of silicon, aluminum and titanium on the surface.
The problem is that the elements required are present as oxides, and all mixed up. That will require separation, (probably mechanical and chemical) of the material, followed by electrolytic refining to very high purity. The pot-line would set solid for two weeks, then melt and operate for two weeks. The entire mining and refining process must be operated on the Moon.

On Earth we have higher purity materials that have been concentrated by geological and surface processes. Sorting through moon-dust will be more difficult without the greater volumes of air and water available on Earth.

How will you cool PV panels during the two week lunar day? Will you need a different semiconductor material to handle the higher temperatures, since there is no atmospheric cooling?

I expect you could do better at first with a solar thermal refinery using mirrors to melt and refine the lunar material. A ceramics industry would come before a high purity metals industry.

Whipley Snidelash
Well as soon as a field of these panels are deployed power won’t be a problem. I’m sure there will have to be an initial investment of materials from off planet but it shouldn’t take too long to become self-sufficient as far as materials and power ago

Gold Member
Well as soon as a field of these panels are deployed power won’t be a problem. I’m sure there will have to be an initial investment of materials from off planet but it shouldn’t take too long to become self-sufficient as far as materials and power ago
Ha! I just did about 3 minutes worth of research, and a bit more maths, and figured out some fun stuff:

1. Instead of my "46 day" initial scenario, it looks like it's going to take 78 years. This is based on the fact that it takes a solar panel about 2 years to generate enough electricity to make another solar panel.
2. A solar paneled moon would generate enough electricity, at todays rates, to generate $123 billion per hour. 3. It would generate 400 times more energy than we currently use here on Earth. Guessing it's the "78 years" that has investors not plopping money down on this idea. Whipley Snidelash Ha! I just did about 3 minutes worth of research, and a bit more maths, and figured out some fun stuff: 1. Instead of my "46 day" initial scenario, it looks like it's going to take 78 years. This is based on the fact that it takes a solar panel about 2 years to generate enough electricity to make another solar panel. 2. A solar paneled moon would generate enough electricity, at todays rates, to generate$123 billion per hour.
3. It would generate 400 times more energy than we currently use here on Earth.

Guessing it's the "78 years" that has investors not plopping money down on this idea.

That is great news, about what I expected, a tremendous amount of available power. But I don’t know where you get the 78 years from. Any colony using this kind of power would need some kind of a back up so there would be nuclear reactors and they would probably be used for power for the initial construction phase. I am also envisioning another use for the power from that solar grid that would use a lot of that power up. Also for a science fiction story I’m writing.

in case I didn’t mention it before and it’s not obvious, this would require a base on the moon first because people would have to be intimately involved with this operation, there is no way it could be completely automated.

The problem with PV on the Moon is that the Moon rotates relative to the Sun.
You can generate twice as much energy from PV in Earth orbit.

Whipley Snidelash
With one side of the moon facing the sun at all times and fields of panels covering a significant area on both sides of the moon Earth orbit PV isn’t even close.
There’s another aspect of this that I haven’t mentioned. These fields would be capable of incredible currents and voltages. This would all be connected by underground superconductors. It should already be cold enough there for buried high temperature superconductors to work in the moon environment.

Mentor
If I wanted to create a factory, possibly automated, on the moon using materials from the surface to create silicon solar cells how hard would it be?
Since you posted this in an engineering forum, not the science fiction forum, you can start by creating a flow chart that starts with lunar rock and ends with an installed solar power system. For a start, the flow chart will show a process for making silicon of the necessary purity, size, and shape. Then doping it, adding electrical connections, mounting it, interconnecting, and an installation system.

Assume a realistic power budget, say 10 kilowatts. Use that to size the entire process. Now calculate how much rock you need to mine per day, how many panels from that rock, and how much waste. Estimate the size and weight of each module. Is there a chance that the entire factory can mass less than about 1000 kg?

It's a big project, but once you get started, we will be able to help.

Whipley Snidelash
You can close this thread. All I wanted to know was the feasibility so that when I write the story the science won’t be BS. Why I put it in this forum. I don’t forsee me actually starting this project anytime soon. I have to become a trillionaire and get to the moon first.

With one side of the moon facing the sun at all times and fields of panels covering a significant area on both sides of the moon Earth orbit PV isn’t even close.
With a diurnal period of 29.53 days, the duty cycle of 50% is a significant inefficiency. How can that be overcome?

Temperature is bad for PV panel MTBF and efficiency. A solar array in space can be cooled by radiation from the back of the panel. That is not possible on the lunar surface.

There’s another aspect of this that I haven’t mentioned. These fields would be capable of incredible currents and voltages. This would all be connected by underground superconductors. It should already be cold enough there for buried high temperature superconductors to work in the moon environment.
Apollo 15 & 17 measurements at about 1 metre depth show stable 252 K, rising with depth.
https://www.lpi.usra.edu/wiki/lunaref/index.php/Thermal_Properties_of_the_Regolith#Subsurface_Temperature
It seems unlikely that superconductors, even buried in shaded surface will help transmit the power.
There are flux limits to the current in superconductors.

All I wanted to know was the feasibility so that when I write the story the science won’t be BS.
That is what we are doing. Fact checking your visionary imagination.

Young people read (science) fiction, then some go on to study, follow the idea and try to make it happen. Give them a chance.

Algr
The problem with PV on the Moon is that the Moon rotates relative to the Sun.
You can generate twice as much energy from PV in Earth orbit.

Presumably the advantage of building it on the moon is that the raw materials are there. Build it in space and you need a lot more rocket fuel. (Would Moon-to-Earth-orbit need less fuel then Earth-to-same-orbit?)

Gold Member
... I don’t know where you get the 78 years from.
Maths.
...there is no way it could be completely automated.
Then you shouldn't have asked if it was possible in your first post.

Whipley Snidelash said:
Would it be feasible to automate silicon solar cell manufacturing, assuming efficiency is not relevant, on the moon?

Whipley Snidelash
Excuse me, allow me to clarify, partially automated will do, I never said fully automated. The complexity of setting up a completely automated operation on the moon would be harder than just having people do it. Sorry, as an engineer I would’ve thought that was obvious, my mistake.

As far as superconductors go, the temperature a few feet under the ground is steady even in the sunlight and it’s below freezing there’s a good possibility that future research into high temp superconductors will reach that temperature considering they are shooting for room temperature. I will have to assume the existence of said superconductor when I write the story assuming the raw materials are either available on the moon or able to be transported to the moon via asteroid mining. I always expected something like this to span many decades to come to fruition even after it started.

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The lunar 252 K = –21°C, is at 1 metre depth.
It is 216 K = –57°C, at 30,000 feet ASL on Earth.
So when/if we get –50°C superconductors, we can have electric powered aircraft on Earth, surfing/levitating on the Earth's magnetic field. You can't do that on the Moon.

Room temperature superconductors would be a game changer for our economy.

Whipley Snidelash
I would say that the Earth's magnetic field is way too weak to use as a repulsion propulsion mechanism if that’s what you’re implying. A modern magnet small enough to fit in your hand is more powerful. The Earth's magnetic field can barely move a compass needle.

I mean creating solar power for use on the moon not exporting the panels here.
Solar panels might not be the best for a starting colony. To make mirrors, pipes and the most basic generators requires far less background than a semiconductor industry: can be done with machinery already required for building/extending a settlement.

At Earth we do have all the required industrial background available, so solar panels are cheap. But that background is enormous and not very practical to transfer/build up far away.

Whipley Snidelash
Whipley Snidelash
What are you saying? Are you trying to say that mirror farms might work better on the moon than solar panel farms? That’s an interesting thought that I hadn’t considered. Mirrors that require constant angle adjustment would be a problem though. Everything needs to be as static as possible. Moving things break.

Both solutions has their own merit, but thermal power plants may require less complicated/difficult background than a semiconductor industry: at least, at the beginning.

Whipley Snidelash
What are you saying? Are you trying to say that mirror farms might work better on the moon than solar panel farms?
Both are needed.
A mirror farm could produce ceramic bricks or molten rock from which rock wool can be extruded or drawn. Rock wool can make reinforcing bar or insulation, at less cost than refining aluminium, then rolling foil or structural sections.
There is plenty of basalt on the moon. Basalt fibre is three times stronger than steel, one third the weight, and does not rust. It is now available commercially as rebar.
https://en.wikipedia.org/wiki/Basalt_fiber

Rive and Whipley Snidelash