1 week Ago By Brandon Vigliarolo
You've perhaps heard of using Moon dirt for building roads and other structures for future lunar explorers. But a group of German scientists reckon they've found another use for the grey stuff: Turn it into glass and use it to assemble solar power cells right there on the Moon. Led by Dr Felix Lang of the University of Potsdam, the research team focused on two unavoidable truths about future lunar life: Settlers will need a lot of solar power, and shipping bulky, Earth-made panels to the Moon is a logistical and financial nightmare.
According to their paper published last week, the team's approach could cut the amount of solar panel material that needs to be hauled off Earth by up to 99 percent. All this while still offering radiation shielding and mechanical durability comparable to conventional panels, they claim. Not bad for Moon dust.
By heating a lunar regolith simulant to 1,550°C for three hours in a vacuum-sealed resistance furnace, the team produced a semi-transparent moonglass-a-like, which they then combined with halide perovskite material to create a functioning solar power cell. "The highlight of our study is that we can extract the glass we need for our solar cells directly from the lunar regolith without any processing," Lang told his university. "The process is also scalable so that the solar cells can be produced with little equipment and very little energy input.
" The highlight of our study is that we can extract the glass we need for our solar cells directly from the lunar regolith without any processing According to the paper, regolith from the Moon's highland regions - rich in anorthosite and low in iron oxide (FeO) - is ideal for this process, as it produces a clearer glass compared to the darker, iron-heavy lowland regolith (they used simulant material in the experiment, not actual Moon dirt, we repeat). While the smelting was done in Earth-based lab conditions, the researchers said the process could be replicated on the Moon with a solar furnace: Essentially a rig of mirrors or Fresnel lenses that concentrates lunar sunlight to reach the required melting temperatures. The perovskite layer used to make the solar cells has to be ultra thin - just 500 to 800 nanometres thick.
According to the researchers, scaling the process could theoretically allow a single kilogram of perovskite precursor material to produce up to 400 square-metres of solar cells. The solar cells Lang's team ended up building were just two millimetres thick, with the moonglass-a-like making up most of the bulk, along with the perovskite and a 100-nanometre layer of copper as the back electrode. While the feat is impressive to us, the power conversion efficiency (PCE) less so, reaching just 8.
5 percent under space-like conditions. That's low by commercial solar standards, and even lower than their glass-based control devices. Much of the reason for the lower PCE comes from the limited transparency of the moonglass - regolith from low-FeO regions still contains enough iron to darken the glass and reduce light transmission.
The team addressed this "parasitic absorption" by significantly reducing the glass thickness, which improved efficiency in lab simulations. A single 0.1mm moonglass layer enabled a simulated PCE of 21.
5 percent under laboratory conditions, the team noted. Transparent ultra-thin metal was also able to increase PCE, the team noted, but they admit simple, thicker designs are likely to be the most advantageous for early lunar deployment. Lang told The Register that silicon extracted from regolith could also be used to fabricate solar cells that "would outperform our approach, potentially without any material that needs to be shipped from Earth.
" Of course, production equipment would need to be shipped, and Lang said the equipment needed to extract high-purity silicon from moon dust would likely make the process impractical. Then there's the problem of radiation degradation. Typical solar cells used on space missions have a life expectancy problem due to ionizing radiation, which causes the glass to darken, leading to lower PCEs.
The simulated moonglass used in this experiment, however, showed impressive resistance to that effect - likely due to the same iron content that gives it its darker tint. Combine that seemingly radiation-resistant moonglass with the known radiation tolerance of perovskite solar cells, and you have a recipe for long(er) lasting lunar power, albeit maybe with a slight drop in efficiency. While it might resist radiation, there are still other concerns around perovskite that Lang told us could affect the lifespan of perovskite solar cells on the Moon - such as constant illumination speeding degradation and extreme temperature swings.
"There are still some questions regarding the stability of perovskites," Lang told us, while noting that the moonglass covering does a good job of eliminating some of the UV damage that perovskites can be susceptible to. "Considering radiation, we believe our perovskite and moonglass could survive more than ten years," Lang told us. "Considering near constant illumination, likely we would need some more research to match these ten years.
" Overall, our results pave the way for future moonsolar cells based on halide perovskites "Overall, our results pave the way for future moonsolar cells based on halide perovskites, an approach that, considering the facile perovskite and moonglass fabrication, outshines other proposed methods to produce solar cells on the Moon," the scientists said in their paper. Whether their method is ready for our next Moon missions - whenever those may ultimately be - is still up in the air, though Lang told us he's working toward getting funding for a demonstration mission, meaning the tech could find its way aboard a future Moon-bound rocket. For now, Lang and his colleagues are focusing on improving those PCE numbers.
"Simply a lower glass thickness is straight forward, and considering that glass can be prepared very thin, this is an interesting option," Lang told The Register . "Another strategy we are working on is a magnetic separation that would allow us to remove iron impurities to obtain more transparent moonglass without much effort." ®.
