Earth nations plan to expand across the solar system sooner or later. First, there will be a human settlement on the Moon. Then we’ll likely go to Mars. These missions will need a lot of energy to survive. How will they get it? Solar panels top the list of possible options.
Getting electricity on Moon
How will we get electricity for all of our needs in space? Wind, hydroelectric power — all these are out of the question. Fossil fuels are not an option either — it’s hard to bring them from Earth and hard to use them, given that the Moon doesn’t have an atmosphere. The three most viable options of getting electricity on the Moon are thermoelectric generators, nuclear reactors and solar power.
Since there is no atmosphere, the Moon experiences extreme swings in temperature. The lunar equator reaches a boiling 250 degrees Fahrenheit at daytime. At night the temperature drops to minus 208 degrees Fahrenheit. Scientists work out methods that will exploit this to generate electricity. In particular, they plan to make use of Seebeck effect.
Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances.
A thermoelectric generator will consist of semiconductor material. When one side of the TEG is exposed to a higher temperature, and the other side is exposed to a lower temperature, the difference will create current. Electrons will flow from the hot side to the cold side.
Another option on the table is nuclear reactors. They don’t depend on night and day cycles and can provide a lot of power for a long time. Two forms that scientists consider for lunar missions are Radioisotope Thermoelectric Generators (RTGs) and fission reactors.
NASA's moonshot plans involve making human settlements by 2040
RTGs convert heat generated by the radioactive decay of isotopes into electricity using thermoelectric materials. They have already been used in the Mars rovers. RTGs are reliable and provide constant power output for an extended period. They are not very efficient though and it would be hard to power a standalone lunar settlement with an RTG only.
Fission reactors are what’s inside of Earth’s nuclear plants. To be useful for lunar missions, they would need to be compact and modular. The U.K. tech giant Rolls-Royce is already working on one: the prototype is 3.3 feet wide and 10 feet long. It will take about 6 years to prepare it for a debut space trip.
What are the problems with nuclear energy in space? Any nuclear reactor is expensive. Fission reactors in particular require stringent safety measures. Besides, scientists don’t know what to do with nuclear waste yet.
Most moon missions use solar energy as a power source. This includes both Russia's Lunokhod rovers from the 1970s and recent China and India missions. For example, the 2023 Indian rover Chandrayaan-3 was powered by solar energy.
In fact, the first solar panels were designed to use in space and later became popular as a power source on Earth. The type of cells used is called p-type and it is designed to withstand space conditions well but is not necessarily the best option for Earth. That’s why n-type solar cells have become much more popular in recent years.
Solar panels are a cheap and straightforward option. Their weight was a concern in the past but scientists have developed lightweight prototypes. For example, In 2017 engineers at the California Institute of Technology presented solar tiles that weighed just 280 grams per square meter. That’s more than 20 times smaller than the average weight of a standard home solar panel which amounts to 10-20 kilograms per square meter.
The problems? Solar panels depend on sunlight. Regolith and dust can accumulate on these panels, reducing their efficiency. The panels deteriorate under UL from the sun and will last for about two decades at best before they have to be replaced. In contrast, nuclear fuel can be stored on the Moon for centuries.
Powering Earth with solar panels in space: From fiction to blueprints
Can we build a space station with solar panels, harvest solar energy in space and send it to Earth? Technically — yes. Is it a good idea? Not quite yet.
The biggest issue with taking anything to space is weight. The more your starship weighs, the more expensive it is going to be to launch it into space. However, the astronauts possibly won’t have to bring solar panels from Earth at all. Instead, they’ll be able to make PV panels right then and there.
cost of bringing a pound of cargo to low Earth orbit in 2018 using Falcon Heavy
Jeff Bezos' private spaceflight company Blue Origin reported in February 2023 that it has made big progress in making solar cells with materials from the lunar surface — regolith. Regolith looks like gray dirt and dust, it’s sticky and smells like gunpowder. Blue Origin engineers simulate regolith with earth dirt and gravel.
The process that the team uses is called Blue Alchemist. Engineers melt the regolith and then extract iron, silicon and aluminum out of it by passing an electric current through the molten material. Then they use the materials to make solar panels, protective glass and wiring. The byproduct is oxygen which you can use for life support or making rocket fuel.
Would solar panels work on Mars? Most definitely; in fact, that’s what Martian robots currently use. Scientists believe that solar power could provide all the energy needed for an extended mission to Mars. The reasons are mostly the same: we’ll need something that is reliable, lasts long, lightweight and preferably non-radioactive. The panels could be installed across the equator to maximize the irradiance levels.
There are more issues with using solar panels on Mars though. The big one is the dusty atmosphere. Red dust might significantly lower solar production. It’s unlikely that the first settlements will have enough workforce to constantly clean the arrays.
NASA robot lander InSight Mission landed on Mars in November 2018. The lander kept track of Martian seismic events and studied the Martian weather. The mission ended in December 2022 when NASA declared that “solar panels finally succumbed to the dust deposition that prevented them from generating power”.
Another problem with Mars solar panels is lower irradiance levels. On Moon, there are places that are illuminated almost 100% of the time. The night on Mars, on the other hand, lasts almost as long as the night on Earth. This means that the settlers will have to figure out how to build an energy store to couple it with PV systems.
NASA Artemis bets on solar power
When exactly we are about to see solar panels on the Moon and Mars in action? The biggest project that is coming up is probably Artemis.
The first mission Artemis 1 was already successfully launched in October 2022. It included the launch of the Orion spacecraft with robots and mannequins aboard. We will have a crew on board in 2024. What everyone is most excited about is a return to the Moon: Artemis 3 is planned to be the first crewed lunar landing. NASA has already declared that the crew will use solar panels to power the needs of an expedition. The launch is scheduled for no earlier than December 2025.
Andrey had been a news editor and freelance writer for a number of medias before joining A1SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.