Electric utilities are are trying photovoltaics, a process by which solar energy is converted directly to electricity. Electricity can be produced directly from solar energy using photovoltaic devices or indirectly from steam generators using solar thermal collectors to heat a working fluid. There were 24 solar electric units operating in the US at the end of 1998, with more on the way. Most of these are in California, though Nevada, Arizona, Texas, and Virginia have them, too. A photovoltaic cell is a nonmechanical device usually made from silicon alloys.
Sunlight is composed of photons, or particles of solar energy.
These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons provide energy to generate electricity. Special treatment of the material surface during manufacturing makes the front surface of the cell more receptive to free electrons, so the electrons naturally migrate to the surface. When the electrons leave their position, holes are formed.