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Solar & Alternative Energy

Video: Concentrating photovoltaics inspired by telescope design

Renowned telescope designer Roger Angel has turned his attention and telescope mirror technology to concentrating photovoltaics.
12 July 2011, SPIE Newsroom. DOI: 10.1117/2.3201107.02

Roger Angel is Regents Professor of Astronomy and Optical Sciences at the University of Arizona, where he directs the Steward Observatory Mirror Lab. He is also the founder and CEO of REhnu LLC, a company that is commercializing a new technology for concentrating solar. Angel is a member of the National Academy of Sciences and a Fellow of the Royal Society of London. His work in developing the new generation of large astronomical telescopes was recognized by a MacArthur fellowship and the 2010 Kavli Prize in Astrophysics. As a result of the latter, he was a guest at the White House in June 2011.

In concentrating photovoltaics (CPV), sunlight is optically concentrated onto very small PV cells. Concentrator cells of exceptionally high efficiency are already manufactured commercially at very low cost per unit of power generated. The remaining challenge to reach the goal of $1/watt installed cost is to devise the supporting optomechanical system that can be manufactured and installed at low cost, to track the sun, concentrate the light on the cells and keep them cool.

A farm will consist of many identical 20-kW tracking units. Each unit, assembled on-site from prefab-ricated steel and glass members, will carry eight square dish reflectors in a balanced, lightweight spaceframe structure. Soccer ball-sized packages at each focus will generate 2.5 kW from triple junction cells arrayed about a 5-inch ball lens. The design ensures evenly distributed, steady illumination of cells, needed for highest efficiency, and good tolerance to pointing errors despite very high (1000x) optical concentration.

Angel's record of innovation in optics includes a new method to grind and polish glass mirrors now used at the Mirror Lab to make the world's largest and most aspheric telescope mirrors; novel methods to test aspheric optical surfaces, including solar reflectors; and a design and cost study for a million square-mile space sunshade to cool the Earth. He has designed telescopes to image and search for primitive life on Earth-like planets orbiting nearby stars and first used optical fibers in astronomy to obtain astronomical spectra, now a widely used technique. He received his B.A. and PhD in physics from Oxford University and an M.S. from Caltech.