Solar thermal power plants use solar radiation to generate heat. This heat is in turn utilised to generate electrical energy using a turbine and generator. A common feature of these power plants is that sunlight is concentrated via arrays of mirrors. In the focal point or “caustic line” of these mirrors is a radiation collector – called a receiver, which heats a gas or liquid in a primary circuit. If a liquid heat transport medium is utilised, its heat is used to generate steam in a secondary circuit, which then drives a steam turbine with a generator – just like in other thermal power plants.
Solar thermal power plants can be easily combined with heat storage systems. Mathematically, the solar potential in equatorial latitudes can cover the world’s electricity requirements many times over.
To capture the solar heat, it is distinguished between solar towers and parabolic troughs. Solar tower power plants consist of a large number of freely movable reflector surfaces that are oriented in accordance with the position of the sun so that they focus light on the receiver in the tower. The currently most cost-effective technology for generating solar power is provided by parabolic trough power plants. Here the sunlight is only concentrated two-dimensionally – the temperatures achievable in the primary circuit are therefore considerably lower. However, the mirrors only have to track the position of the sun along one axis, which simplifies the mechanics and the control system.