NASA Takes Solar Power From Earth to Space and Back Again

A remarkable 30-year partnership between NASA's Glenn Research Center and a solar panel developer has led to a technology that has transformed solar energy collection in space, and on Earth.

The product of that collaboration, the stretched lens array, uses a thin film lens to concentrate sunlight on a small area of high-efficiency photovoltaic solar cells. The technology significantly reduces the weight of the solar arrays that power spacecraft and space stations, and makes solar power on the ground much more affordable.

The stretched lens array was developed for use on the ground, then redesigned for use in space. A spinoff of the space technology is now being used back on the ground in an advanced solar panel that the commercial partner, Entech Solar of Fort Worth, Texas, plans to commercialize in 2012. Although the materials used for space and on the ground are different, the fundamental design is similar. In space, the primary need is to minimize mass, while the focus on the ground is to reduce cost. The stretched lens array, which won a 2012 FLC Award for Excellence in Technology Transfer, achieves both goals.

"The story of this technology is absolutely about the Entech-NASA partnership," said Roshanak Hakimzadeh, Deputy Chief Technologist at Glenn. "It was NASA's need for a smaller, lighter weight, inexpensive technology that drove the work and pushed the envelope to achieve these extraordinary results."

In the late 1970s and early 1980s, Entech Solar (then Entech, Inc.) developed a solar power concentrator for terrestrial applications that was spun into a concentrator for use in space in the late 1980s. Collaborative work among NASA, the Ballistic Missile Defense Organization, and Entech continued through the 1990s, culminating in a lens array that was used on NASA's New Millennium Deep Space 1 mission (1998-2001). That asteroid/comet rendezvous mission demonstrated the performance and long-term durability of the solar array design and laid the foundation for further improvements.

Prior to the Deep Space 1 success, the Glenn team, led by Mike Piszczor, devised innovative and creative ways to test the lens array for performance in space conditions. That included using NASA's Lear Jet for photovoltaic testing, and funding an array installation at 10,000 feet above sea level on Mt. Haleakala in Hawaii, to test the technology in a space-like solar spectrum.

The stretched lens array is unique among all solar array technologies in its range of benefits, which include very high efficiency, ultra-light mass density, high-voltage capability, and cost-effectiveness. Those capabilities are critical for many of NASA's planned space missions, including orbit maintenance for the International Space Station, and orbit raising and lowering of spacecraft for science missions around the Earth, moon and asteroids.

Glenn's collaboration with the space industry continues. Ad Astra Rocket Co., of Webster, Texas, is interested in using a version of the technology to support its advanced plasma propulsion system. The stretched lens array "is a spectacularly enabling technology for electric propulsion in space," said Tim Glover, Ad Astra's director of development.

Back on Earth, Entech Solar's new SolarVoltª panel recently received International Electrotechnical Commission certification, and is protected by a number of issued and pending patents. The company is completing manufacturing scale-up plans, both in-house and at key suppliers, that will create U.S.-based jobs as it implements its mass production plan for the ground-based system.

The SolarVolt has a number of potential applications, including use in utility-scale power plants, smart-grid systems, communications systems, industrial building power systems, and military power systems.

The SolarVolt has zero greenhouse gas emissions, and can generate power at a lower cost per kilowatt hour than many existing photovoltaic systems.

In journeying from Earth to space and back again, the stretched lens array has evolved into a powerful technology that will enable future NASA missions, further the commercial development of space, and help provide inexpensive renewable energy on the ground.