National Aeronautics and Space Administration

Glenn Research Center

Sheila Bailey

Synergy of Photovoltaic from Space to Terrestrial Applications

July 10th, 2009, Glenn Research Center – Cleveland, OH

Dr. Sheila Bailey gave a talk on solar power on July 10th, 2009, as part of the intern speaker series at Glenn Research Center. She began with a brief history of solar cells, noting that they were first built at Bell Labs. The technology struggled to find an application until NASA’s Vanguard 1 satellite used it in its mission. NASA’s need for power in space gave solar cells their first real market, and solar power was able to grow as a technology.

Dr. Bailey talked about the need for solar power to sustain the energy demands of humans. Human energy consumption is predicted to continue to grow exponentially, but energy output from conventional fossil fuel sources is getting close to peaking. To continue to be able to meet the demand for cheap power, humans will need to find a new sustainable energy source. Dr. Bailey believes that solar power can provide the necessary power to meet growing human consumption.

Dr. Bailey then talked about the similarities and differences between terrestrial and extraterrestrial space power. The end goal for terrestrial solar power is the lowest cost of energy. The solar industry is working toward the goal of reaching grid cost parity with conventional power sources. Space solar power has different goals than terrestrial solar power. In space, the goal is to maximize power while minimizing mass and volume requirements; the actual cost of the cell itself is dominated by launch costs.

Thus, efficiency of the solar cell becomes much more important than for terrestrial applications. Unlike on earth, the sunlight in orbit is not refracted by the atmosphere, and thus more power can be gained per unit area. On the other hand, in-space solar cells have to deal with the harsh environment and be protected against radiation.

NASA’s role in advancing solar cell technology is an important niche to define. Because so much has already been accomplished with silicon solar cells, NASA is instead concentrating on more radical concepts. Dr. Bailey’s lab has been concentrating mainly on III-V solar technology. However, the lab has also been exploring possibilities in the emerging organic and thin film solar markets.

Dr. Bailey concluded her talk by saying that multi-junction solar cells are the immediate future of space technology, using quantum dot technology to increase performance while being more robust to the effects of radiation. After the talk ended, Dr. Bailey joined the Glenn Academy for lunch, while discussing her life and development as a researcher, NASA’s role in renewable energy technology, and changes she would like to see come to NASA.

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