Concentrated solar power (CSP) technologies convert sunlight to heat energy. Much like conventional power plants, CSP technologies then use heat energy to generate electricity. There are three main types of commercialized CSP plants, which primarily differ in how they concentrate and convert sunlight to heat energy:
- Trough systems use large, parabolic reflectors to concentrate sunlight on pipes often filled with oil running along the center. The heated oil is then used to superheat steam to power a conventional turbine that generates electricity.
- Power tower systems that use large flat mirrors (heliostats) to track the sun and focus sunlight on a central tower at concentrations exceeding 100 times the normal sunlight. The heated air or molten salt in the tower transports the heat to superheat steam to power a conventional turbine that generates electricity.
- Dish systems are typically smaller and use mirrored dishes to concentrate sunlight. The heat energy is converted into kinetic (motive) energy to drive an electricity generator, such as a Stirling engine or open Brayton gas turbine. Thermoelectric devices can also be used to convert the heat directly into electric current.