The sun's energy is collected and concentrated by a dish-shaped surface onto an receiver that absorbs the energy and transfers it to the engine's working fluid. The engine converts the heat to mechanical power in a manner similar to conventional engines-that is, by compressing the working fluid when it is cold, heating the compressed working fluid, and then expanding it through a turbine or with a piston to produce work. The mechanical power is converted to electrical power by an electric generator or alternator. The ideal concentrator shape is parabolic, created either by a single reflective surface or multiple reflectors, or facets. Many options exist for receiver and engine type, including Stirling engine and Brayton receivers.
More capacity is possible by connecting dishes together.
These systems can be combined with natural gas and the resulting hybrid provides continuous power generation. This energy heats molten salt flowing through the receiver, and the salt's heat energy is then used to generate electricity in a conventional steam generator. The molten salt retains heat efficiently, so it can be stored for hours or even days before being used to generate electricity. Solar Two, a demonstration power tower located in the Mojave Desert in California, can generate about 10 megawatts of electricity. When power is needed from the plant, hot salt is pumped to a steam generating system that produces superheated steam to power a turbine and generator.