Photovoltaics is the science of turning light into electrical energy. This method of creating electrical energy from light, involving solar cells, can be performed successfully both on Earth and in space.
NASA’s Glenn Research Center in Cleveland has been a leader in photovoltaics research since the 1960s. Today, this expertise includes researching, developing, designing, fabricating, calibrating and testing solar cells, as well as inventing new solar cells and discovering new ways of using solar cells.
From powering spacecraft to providing heat for a home, photovoltaics are an important aspect of the evolving field of alternative energy.
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Photovoltaics is a method of turning light into electricity. The photons that exist in light, such as the sun, are absorbed by a solar cell and converted into electrical energy. This electrical energy can be used to provide heat in a home or power for a spacecraft. Almost all new spacecraft contain some photovoltaic element."NASA has experts in different areas of photovoltaics at different centers," says Michael Piszczor, Photovoltaics branch chief at NASA's Glenn Research Center. "The primary focus on photovoltaics at Glenn is on research and development. Our job is to take the long range view and ask, what will NASA need 5, 10, 20 years down the road?"
This photovoltaics research and development includes design and fabrication of different types of cells, calibration and extensive testing of the cells, and discovering innovative ways of implementing cells for use on current and future NASA missions.
The Photovoltaics Branch at NASA's Glenn Research Center performs some research that isn't tied to a specific mission or program, but that could benefit countless future missions. The Photovoltaics Branch also performs research that supports specific NASA missions, such as the Solar Probe Plus. The Solar Probe Plus is a collaboration between NASA and the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. The mission intends to use photovoltaics to travel close to, and learn more about, the sun.
"We run the range from near term projects, involving solar cell testing, to midterm projects where programs are just starting, to research not tied to any program yet. We have efforts in all of those areas - that's how we support NASA, with our expertise," says Michael Piszczor, Photovoltaics branch chief at Glenn.
"We work very closely with the aerospace industry, and many other government agencies," says Michael Piszczor, Photovoltaics branch chief at NASA’s Glenn Research Center. "The Photovoltaics area is a close-knit group, especially in the area of space applications."
Glenn frequently works with the United States Air Force Research Laboratory, the United States Naval Research Lab and the Department of Energy on collaborations and joint projects involving photovoltaics.
NASA, including Glenn, has provided technology that has been space qualified for use by the military and commercial industry, such as is used on satellites. In addition to bringing support to those organizations, NASA explores even further to see what else photovoltaics can be used to achieve.
Glenn researchers work on solar cells that can withstand the extreme heat of the sun and the extreme cold of Jupiter. The Photovoltaics Branch also explores how cells can withstand radiation and harsh environments, and imagines new ways that solar cells can be used to revolutionize aeronautics.
"As we help and support the photovoltaics aerospace community, we support NASA as well," Piszczor says. "We collaborate on a daily basis."
The Photovoltaics Branch at NASA's Glenn Research Center was formed in 1961, when the center was still called NASA Lewis Research Center. Glenn’s expertise in solar power has expanded and grown in the decades since. Throughout the 1960s, the photovoltaics team at Glenn began developing its expertise in researching and developing technology to harness solar power for use in spaceflight.
In the 1970s, research into spaceflight solar power continued, and research into terrestrial (based on Earth) solar power began at Glenn. Glenn partnered with the Department of Energy and its predecessor, the Energy Research and Development Administration, on the testing and design of solar power. Several new technologies were developed during the ‘70s. Glenn led efforts to test photovoltaics in terrestrial settings. During the '70s, a Glenn team travelled to the remote village of Tangaye, Upper Volta in Africa. They installed a photovoltaics system that powered a water pump, grain grinder, lights, refrigeration and communications systems. After this successful mission, a Glenn team created the world's first solar-power village—the village of the Papago Tribe in Schuchuli, Ariz. In total, Glenn developed 57 photovoltaics systems at 27 different locations in the United States and in developing countries.
Throughout the 1980s and 1990s, Glenn researchers worked extensively on power systems for spacecraft, including the photovoltaic arrays used on the International Space Station. Research continued into the new millennium into different ways of using solar cells, making the cells smaller and more efficient, and discovering how best to calibrate and test the cells. Since the 1960s and continuing today, Glenn provides essential photovoltaics expertise to NASA, other governmental agencies and the country at large.
Solar cells that will be used in space have many special criteria—they must be durable, dependable and lightweight. NASA's Glenn Research Center investigates how to best use solar cells in space, and discovers new types of cells.
Glenn's Photovoltaics Lab includes reactors which are smaller versions of the reactors that industrial solar cell manufacturers use. That way, research can be done on the cells using the same sort of equipment that is used by the aerospace community.
Glenn's facilities include a calibration lab, where solar cells are carefully examined and measured under a variety of conditions. Glenn also operates a Learjet 25, and solar cells are flown on this airplane to about 50,000 feet above Earth. At this height, the light that reaches the solar cell is nearly the same as the light that reaches solar cells in space. This solar cell is then considered calibrated to space conditions, and is essential as a tool for measuring other solar cells. Many commercial entities depend on Glenn's calibration lab to test their cells, as they know the lab offers accurate, impartial expertise.
In addition to the research and calibration of solar cells, Glenn is also working to incorporate nanotechnology into photovoltaics—making solar cells for space even lighter and more efficient. Creating more efficient solar cells is part of Glenn research, along with developing more efficient solar arrays. Glenn is also investigating thermal photovoltaics (deriving electrical energy from heat), which would be useful on missions far from Earth.
"We have a lot of diverse technical expertise," says Michael Piszczor, Photovoltaics branch chief at Glenn.
"A lot of the expertise that we have at Glenn is directly applicable to the terrestrial environment," says Michael Piszczor, Photovoltaics branch chief at NASA’s Glenn Research Center.
While the prime focus of the Glenn Photovoltaics Branch is on solar cells for space, many other projects have been undertaken with companies through Space Act Agreements. One such collaboration involves vertical multijunction silicone cells, which were developed by a former NASA engineer. The cells are currently being tested in concentrators at Glenn, with the concentrators serving as test beds.
Glenn is also working with Alpha Micron, Inc. of Kent, Ohio on a project involving liquid crystal and window darkening. Glenn is working to help make the project self-powering through use of solar cell technology.
Glenn has also worked with a company that is developing solar cells that create electricity from indoor lights. The calibration and testing capabilities that Glenn offers are hugely helpful to companies who wish to explore land-based solar cells.
Much of Glenn’s space solar cell expertise is relevant to the terrestrial realm, and much of the technology can be used or adapted for use on Earth.
Information about the Photovoltaics Branch at GlennNASA Science: How Do Photovoltaics Work?
Illustrated information from NASA explaining how photovoltaics work.National Renewable Energy Laboratory
Information on photovoltaics and solar thermal systems.GreenCityBlueLake
Information from the GreenCityBlueLake Institute of the Cleveland Museum of Natural History.Florida Solar Energy Center
Information on terrestrial photovoltaics and residential applicationsPhotovoltaics Education Network
Technical and educational information explaining how solar cells workPrinciples of Semiconductor Device
Technical and educational information about semiconductorsDynamic Periodic Table
An accessible and interactive periodic table called the Dynamic Periodic Table.Photovoltaics Fact Sheet (PDF)