Innovating Hetrojunction PV Technology in Space
Experts predict that by 2050 we're going to have global broadband internet satellite networks, in-orbit manufacturing, space tourism, asteroid mining and lunar and Mars bases.
More than a gigawatt of solar energy will be needed to power these activities, or the equivalent of 3.125 million photovoltaic panels. However, because it is currently the most expensive component on a satellite, scientists are looking for ways to make solar energy in space affordable — and to keep solar power systems from degrading so quickly in the extremely harsh environment of space.
A gloved hand holds a flexible solar cell in a lab (pictured above). Arizona State University postdoctoral researcher Stanislau “Stas” Herasimenka’s startup company, Regher Solar, is developing a thin solar cell to better withstand the harsh environment of outer space.
Regher Solar believes it has the solution to provide cost-effective and efficient, next-generation solar power for space applications.
Silicon heterojunction technology uses a low-temperature method to deposit layers of amorphous silicon with a high concentration of atomic hydrogen onto a crystalline silicon wafer. This method creates a solar cell that's more efficient at converting sunlight into electricity than conventional solar cells, which are manufactured using standard high-temperature methods.
Pioneered in the 1990s, silicon heterojunction technology is not new, but it's not widely used in the commercial solar energy industry. However, it holds great promise for the future of solar energy.
In conventional solar cells, the current manufacturing efficiency is up to 21.5 percent. Herasimenka believes silicon heterojunction solar cell technology can be manufactured to attain 23 to 24 percent efficiency without increasing the cost of production.
While that would seem to be a small step, it's actually the next giant leap the solar power industry is looking to achieve. Seeing this as an opportunity to apply his graduate research, Herasimenka founded solar cell technology startup Regher Solar with solar industry expert Michael Reginevich.
Stuart Bowden, an associate research professor of electrical and energy engineering in the Ira A. Fulton Schools of Engineering, praised Herasimenka's work both as a doctoral student and a postdoctoral scholar to create commercial-grade silicon heterojunction solar technology.
"When I came to ASU in 2009, Stas was our first student to complete an experimental thesis, and his passion for solar was critical to kick-start the lab," said Bowden, Herasimenka's doctoral research adviser.
"He did extensive theoretical modeling work but he was also the one who pushed on making his research commercial. Stas has really embraced the entrepreneurial spirit at ASU and it’s great he has the support to take his lab work out into the world,” Bowden added.
Space: The solar frontier
It’s very complicated for a novel solar technology to enter the market. The current cost of a commercial solar panel is about 30 cents per watt.
At this point in its development, silicon heterojunction solar cell technology is too expensive for the terrestrial market but may be very attractive to aerospace companies.
The current leading technology of solar energy in space is in the form of tandem solar cells, which are more efficient than terrestrial solar cells (28 to 32 percent efficiency), but they cost orders of magnitude more at $100 to $500 per watt. In comparison, Regher Solar's silicon heterojunction technology is a great deal at $1 per watt cost even with the loss of about 7 percent efficiency.
Not only is the price right, Herasimenka and his Regher Solar team have ideas in mind to make solar cells that are more resistant to the harsh environment of space that theoretically could also increase their end-of-life efficiency.
Their research caught the attention of Albuquerque, New Mexico-based SolAero Technologies and the Air Force Research Laboratory's Small Business Innovation Research (SBIR) grant program, which seeks to fund technology to implement a space transport that could shuttle spacecraft from low Earth orbit to higher orbits. The area through which the transporter would operate is also where radiation is most damaging to spacecraft solar cells.
