Photovoltaics III: Concentrators: Focusing the sun´s rays, using cheap, long-lived optics, will be exploited in direct sunlight regions

Photovoltaic concentrating systems redirect sunlight falling on a surface to a smaller solar-cell surface. They concentrate the intensity of sunlight to many times — perhaps even hundreds of times — its normal value. Because such systems can generate a large amount of electricity with a relatively small cell area, they make it economical to use complex, high-efficiency cells. Moreover, concentrating systems can produce heat as well as electricity for very little extra cost.