Solar power already is being used in forward operating and remote bases by the military to reduce weight and the need for fuel—transporting fuel is one of the deadliest jobs in the military. But now the National Renewable Energy Laboratory (NREL) is working with the military and soldiers to make solar more personal.
Using solar at forward-operating bases is a start, but using solar power in the field could be even more valuable to making soldiers more nimble and better able to engage in operations. Researchers at NREL are working to make solar power lighter and more flexible for soldiers, like Marines, whose packs can weigh upwards of 80 pounds and include 20 pounds of battery backups to power electronics each Marine carries. Last summer NREL partnered with the Office of Naval Research with $1.5 million in funds to explore making lightweight solar cells over the next three years, according to NREL’s Connie Komomua and Ernie Tucker.
This is leading to some new thinking in solar cell designs. For instance, many thin-film (micrometers-thick) solar cells using technologies like cadmium telluride (CdTe) or copper indium gallium selenide can be built on flexible substrates but have been less efficient than the silicon photovoltaic cells most used today.
“What if we could grow solar cells on the same heavy substrate we use in the standard high-efficiency, low-cost polycrystalline processes?” posited Matthew Reese, NREL staff scientist in PV research. Such devices could then be lifted off the heavier substrates and transferred to lighter-weight substrates.
There are some challenges to growing such PV devices on flexible substrates. "When you grow a CdTe cell, you need to grow it for highest efficiency on a transparent substrate," Reese explained. Also, "the order in which you grow the layers of a cell is critical. For CdTe, the substrate has to be transparent, and that limits choices.” He explained further that the since CdTe requires high temperatures to grow, plastics won't work as a suitable substrate.
Reese previously worked on research to create lightweight, lower-efficiency CdTe PV cells on flexible glass but even that can shatter. The Navy showed interest in that research but wanted higher efficiency cells.
"We thought for a little bit, and then it occurred to me,” Reese said. “We'd done this diagnostic test by delaminating CdTe cells," Reese said, referring to a way of lifting a cell off a substrate to remove it. "Maybe we really could have the best of both worlds. We could de-couple growth constraints from a package of choice. You could select whatever you wanted as the ideal package at the end," Reese said.
The Navy approved the approach and now the two are working together to develop low-cost, flexible, high-efficiency solar cells that can withstand the rigors of battle. If they’re successful in creating such a device, it could reduce the weight Marines and other soldiers have to carry, reduce the need for manned supply convoys, and could help energize drones. All of which could ease military burdens and save lives, Komomua and Tucker wrote.Tweet