Sun

Photovoltaic means the direct conversion of light into electricity by the use of a semiconductor like silicone. Already known for more than a half century and used in a lot of special applications (satellites, etc.) installations of photo- voltaic systems are experiencing a boom in the countries where governmental support in the from of feed-in tariffs are in place. Today commercial solar power plants in the MW size are installed, especially in several European countries. In rural areas solar home systems can provide a solution for power supply to houses distant from the grid. These systems consist of solar panel (s) combined with a rechargeable battery and a charger/inverter.

In solar thermal power plants the heat energy of the solar radiation is used to heat up melted salt or other liquid to finally drive conventional steam or gas turbine power plants. In the last century several designs have been tested and the technology has matured. The highest temperatures are obtained in the solar tower power plant, where a field of mirrors concentrates the radiation to a central tower, where the radiation is heating a thermal fluid or gas which drives a turbine.

In parabolic trough power plants an absorber tube is located in the focal line of a parabolic mirror. Temperatures of 400 °C have been obtained and several prototype plants have been operated successfully. Both types of plants have power capacities of several hundred Megawatts and could be operated in hybrid mode together with a second heat source, e.g. natural gas. More: http://en.wikipedia.org/wiki/Solar_energy or http://www.ises.org/ises.nsf