About Portable power

PORTABLE POWER That 10% low power warning on your phone or the red battery on your tablet are helpful reminders to plug in. But they’re also a sign of trouble when you’re in the woods, all the outlets in the airport waiting area are taken, or you forgot your charger. Having a lightweight, affordable portable solar panel that makes it convenient to recharge all those batteries is now a viable alternative, thanks to NASA. “We’ve had a lot of small business partners looking not just at advanced cell technology, but also at maintaining low costs,” says Mike Piszczor, chief of the Photovoltaic and Electrochemical Systems Branch at NASA’s Glenn Research Center in Cleveland. “For space applications, a typical cell that’s about 1.5 by 3 inches is $400–$500, and that’s because they go through flight qualification in addition to the manufacturing process used. It saves in the long run, because even with that very expensive cell technology, it’s so efficient that it saves in overall system cost.” The price for these cells has remained steady, Piszczor says. The traditional space focus on efficiency and high reliability means there’s little incentive for the technology or the cost to change. So the agency has been generating that incentive to benefit the space program and consumers. Most solar cells rated for use in space have a conversion efficiency of about 30%, meaning about a third of the sunlight that strikes the cell is turned into electrical energy. Commercial solar cells are typically 15 to 20% efficient. The greater the efficiency, the smaller the solar cell area that is needed. This frees up space and saves weight for other critical items. The companies that make these cells are developing a new method for growing highly efficient inverted metamorphic multijunction (IMM) solar cells. These cells, which use layers of multiple semiconductors to capture more of the solar spectrum, are grown on a surface—or substrate—of gallium arsenide. A process for reusing the substrate could ultimately result in less expensive but more flexible and lightweight solar cells (See Cosmic Neighborhood). A lightweight, flexible, space-qualified solar cell with a substantially reduced price would make it more likely for NASA to achieve the goal of developing solar arrays capable of producing up to several hundred kilowatts. Currently, each of the solar arrays on the space station can produce about 30 kilowatts in full sunlight. “That’s where MicroLink comes in,” Piszczor says. “MicroLink has developed technology that is very similar to what the current space cell companies have, but what they do is reuse the substrate. In terms of solar cell price, for a typical state-of-the-art space cell, that’s about 40% of the cell material costs.” MicroLink Devices Inc., based in Niles, Illinois, has been awarded multiple Small Business Innovation Research contracts from NASA to focus on cost reduction and improved cell performance. Chris Youtsey, MicroLink’s director of fabrication, says, “Our work was really focused on developing this technology for terrestrial applicati Troops in desert regions already are using MicroLink Devices’ flexible, lightweight solar arrays as a source of portable, renewable energy. The panels attach to a backpack and are capable of charging military batteries, eliminating the need to carry extra ones. (Image Credit: MicroLink Devices In addition to off-Earth applications, the cells can be used in concentrator systems, “in which mirrors focus the light down on a very small cell, increasing the focus of light by maybe 500 or more times” than if the cells were placed individually, says Youtsey. The military is already benefiting from the company’s work. A solar array that troops carry when out on patrol uses MicroLink solar cells to collect sunlight and generate electricity to recharge batteries. This frees up space and saves weight for other critical items, such as food or water. In 2014, the magazines Popular Science and Popular Mechanics featured articles about these panels, with Popular Mechanics awarding the U.S. Naval Research Laboratory’s Marine Austere Patrolling System, developed by MicroLink, with its 2014 Breakthrough Award for Innovation. A similar panel, made in partnership with the Naval Research Laboratory and the Marine Corps Expeditionary Energy Office, was featured in a March 2014 issue of Information Week. Many of NASA’s spacecraft rely on solar power to function in space. Here technicians at Vandenberg Air Force Base install the solar array for NASA's Ionospheric Connection Explorer. The spacecraft is now studying the zone high in Earth's atmosphere where terrestrial weather meets space weather. These wearable solar panels provide power to charge batteries for troops’ devices in the field when it is needed. “The characteristics of our cells are attractive because they’re high efficiency, you can make a small panel that produces a lot of power, and they’re rugged because they’re flexible,” says Youtsey. MicroLink recently provided solar cells to be added to the wings of a remotely piloted drone, providing all the power needed for operation.