Solar cells and the space travels

On 20th July 1969 the Apollo 11 mission brought the first man to the moon successfully, but not without risk. Just before landing the vehicle turned out to experience an early low fuel warning, and had little left in the reservoir to actually sustain another minute of flight. Luckily it landed right on time!

Indeed, space is a vast environment with no electrical outlet nor gas station, where power storage thus becomes utterly important to human missions.

On Earth, renewable energy sources nowadays are looked at in order to decrease fossil fuel usage and CO2 emissions. The sun is an important source of energy that allows to produce electricity via the photoelectric effect when sunlight is absorbed by solar cells.

Solar cells have also been looked at for space applications on spacecrafts and satellites. These solar cells need to be able to withstand excessive heat and cold plus constant shower of solar radiation. For these reasons, NASA has put a lot of research in developing resistant and efficient panels.

This development started in 1964 when NASA launched a solar powered satellite called Nimbus 1 into space for meteorological research, that comprised a 470 watt photovoltaic array on so-called “solar paddles”, followed by the first Orbiting Astronomical Observatory in 1966, powered by a one-kW array.

More recently in 1989, NASA partnered with Iowa Thin Film Technologies, Inc. (now PowerFilm, Inc.). to incorporate paper-thin solar cells onto flexible sheets that can be rolled up for storage.

Solar cell materials for space comprise silicon cells covered in thin glass, or multi-junctions made up of gallium arsenide. NASA is also the owner of patents on such solar research, including Patent US9418844B1 disclosing a type of multi-junction solar cell.

Research is actively ongoing to find more light absorbing materials, improve the flexibility or even face the material problems associated with dust and dirt.

It was for instance estimated that a tiny dust deposit of 2.8 grams of dust per 0.9 meters can reduce solar panel efficiency by as much as 40 percent! The first dirt-repelling coatings for solar panels were developed for use in space. For instance, NASA owns a patent US7999173B1 named “Dust removal from solar cells”.

I am convinced such research, which also helps for terrestrial applications and the global need for better renewable energies, should be encouraged nowadays.

As one can see, the moon and space may seem like far entities, but they were triggers for more research and development for improving our future and our planet.

This blog post is part of a series of 'Man on the Moon' articles to honour the 50th anniversary of the Apollo 11 moon landing.