How practical is it to manufacture solar cells on the Moon? I understand there is a lot of silica there, and in theory if we could robotically make and deploy solar cells on the Moon, then we would (in time) have practically unbounded energy to use there.
Perovskites may prevent the need for such complex manufacturing facilities.
Perovskites are made of Calcium, Titanium, and Oxygen, all of which have been found in significant quantities (>1%) on moon rocks (source).
This source estimates the Moon's crust to be composed of 4-6% Calcium, 1-2% Titanium, and a whopping 60% Oxygen. (Silicon is estimated at 16% and Aluminum at 6%, for anyone interested in making mirrors.)
Also needed for Perovskites is an absorber material, usually (so far) either methylammonium lead trihalide or the same thing with tin in place of lead. Sourcing these must be considered as well at some point.
See Perovskite Solar Cells on Wikipedia as well, and this article, which mentions some other details. One drawback: Perovskite cells have had shorter lifespans than other cells. One interesting fact: They have some reliance on lead (Pb), which has made them unattractive for on-Earth applications, but may not matter as much in space.
There are parts that would be easy, and parts that would be quite difficult. Here is a video that shows you how solar cells are made on Earth.
Here's a few things you need:
- A very high efficiency clean room.
- Wafer manufacturing capabilities
- Etching equipment
- Diffusing equipment
- Metal inlaying
Bottom line is, this is very large and difficult equipment. It would probably not work very well. What are some alternatives? The best alternative would be to make mirrors, which in turn heat a substance, like water, and runs like any turbine engine runs. Wikipedia has a nice photo of one of these on Earth.
Mirrors, especially non-precision mirrors, would be relatively easy to manufacture on the moon. Aluminum and silicon are quite plentiful, the two key elements to making mirrors. The turbines might be difficult to manufacture on the Moon (I really don't know about this one), but they could be brought from Earth, reducing the weight significantly vs the solar panels that would be required to make this system work via direct transport from Earth.
Lunar Reources Inc. proposes to manufacture solar panels in situ by electrolyzing the lunar regolith to seperate the various components (metals, silicon, oxygen, etc.) and vacuum-depositing material on the surface. There's an article on Universe Today about their proposal to build a radio telescope of the far-side of the moon using this technique. Universe Today also has a podcast interview with their CTO Alex Ignatiev that goes into more detail regarding the production of solar cells specifically.
On Earth the factories that make silicon solar cells operate within a greater economy that offers ready access to energy, water, construction capability, specialist suppliers and services. Manufacturers don't exist and work in isolation or self-sufficiently in extreme environments.
Making solar cells on the moon appears to require something very different. It appears to require some kind of highly automated and wholly self contained solar cell manufacturing plant built of modular elements, that has to include associated mining, refining and processing and production of all the materials and consumables that complex and exacting solar cell manufacturing requires.
It appears beyond our current technological capabilities to make such an automated, self contained PV manufacturing plant, even one operating with full access to those specialist materials, consumables and services on Earth.