Although it may not be apparent from looking at it, the roof of this building at Aquinas College in Grand Rapids, Michigan, functions as a solar power plant. The building-integrated photovoltaic (PV) roofing material that makes this possible was produced by United Solar Systems Corporation, which uses a process that deposits amorphous-silicon semiconductor material on a continuous roll of stainless-steel sheet metal. This technology earned United Solar, the National Renewable Energy Laboratory, and the National Thin Film Photovoltaics Partnership Program a prestigious R&D 100 award in 1998. (Photo credit: United Solar Systems Corporation, Troy, MI.)