For decades, scientists have aimed to create the perfect solar panel design for the benefit of all of us here on Earth. Now, research suggests that these supercharged panels could also be a boon much further away from home.
In a new study, a team of German scientists strapped four different perovskite and organic solar cells to a rocket and shot it up into low-Earth orbit (LOE) to see how solar panels perform in non-terrestrial conditions. The flight only lasted seven-minutes but the researchers were able to collect some promising indications of how these panels adjusted to the change.
These panels showed no real dip in functionality and even demonstrated the ability to work in low-light conditions better than their heavier, inorganic counterparts. Researchers believe that these capabilities could make them prime candidates for the future of deep space travel.
These findings were published Wednesday in the journal Joule.
In the paper, the researcher team explains that the history of solar cell-powered space flight and experimentation has been, at best, lacking. The year 1959 saw the launch of the first solar-powered rocket, Explorer 6; in more recent decades tests on solar panels in space have been done using stratospheric balloons to float up near the Earth's stratosphere. This isn't exactly the same as achieving actual orbital heights.
As a result, it's difficult for scientists to extrapolate how some of the current research could be applied to deep space missions. To get a little closer to this reality, this research team shot their solar cells around 149 miles into the sky.
How does it work — The rocket carrying a selection of four ultra-thin solar cells lifted off from Sweden in June 2019 for a quick seven-minute spin around the LOE block. The solar cells on board (or rather, attached outside to the payload) were a mix of perovskite and organic solar cells.
The authors write that these cells were so thin and light (2.2 lbs each) that they could generate enough electricity to power 300 standard light bulbs.
But, while these solar panels may be impressive on Earth, seeing if they maintained their effectiveness in space was the name of the game.
After a successful launch and landing, in which the solar cells survived resultant physical stress, the team analyzed some promising data from the solar panels' adventures. In addition to maintaining their efficiency in the LOE environment, the team also found that the panels were able to operate in low-light environments where the only light source was light scattered off Earth.
The authors write that this finding not only shows performance beyond current technology but also suggests potential for deep space missions in the future which may have low-light conditions.
"This is a good hint and confirms that the technology can go into what is called deep space missions, where you would send them far out in space, far away from the sun, where standard solar cells wouldn't work in," says the study's senior author and researcher at the Technical University of Munich, Peter Müller-Buschbaum.
While not proven by this particular research study, previous research has also demonstrated that space (which is inherently a lot dryer than Earth) may actually be good for perovskite solar cells, which commonly face environmental degradation problems on Earth.
What's next — While these solar cells show a lot of promise when it comes to powering deep space missions in a lightweight and cheap way, there are also many other factors to consider before these cells can be slapped on the next stellar probe. First, the authors say that tests of longer durations will be necessary to see how well these panels might hold up for a long-haul flight (like these deep space missions would be.) Unfortunately, seven-minutes doesn't quite cut it.
Another thing that future research will need to consider is the effects of the outer space environment (i.e. solar and cosmic particle radiation, ultra-high vacuum pressure, and huge temperature differences.) With more commercial spacecraft taking off all the time, hopefully, this data can be collected in the not-so-distant future.
Abstract: Perovskite and organic solar cells possess a revolutionary potential for space applications. The thin-film solar cells can be processed onto thin polymer foils that enable an exceptional specific power,i.e., obtainable electric power per mass, being superior to their inorganic counterparts. However, research toward space applications was mainly restricted to terrestrial conditions so far. Here, we report the launch of perovskite and organic solar cells of different architectures on a suborbital rocket flight. This is an in situ demonstration of their functionality and power generation under space conditions. We measured solar cell current-voltage characteristics in variable illumination states due to different rocket orientations during flight. Under strong solar irradiance, the solar cells perform efficiently, and they even produce power with weak diffuse light reflected from Earth’s surface. These results highlight both the suitability for near-Earth applications as well as the potential for deep-space missions for these innovative technologies.