The efficiency of heat engines increases with the temperature of the heat source. To achieve this solar thermal energy plants, solar radiation is concentrated by mirrors or lenses to obtain higher temperatures – a technique called Concentrated Solar Power (CSP). The practical effect of high efficiencies is to reduce the plant’s collector size and total land use per unit power generated,reducing the environment’s impact of a power plant as well as its expense. Since the CSP Plant generates heat first of all, it can store the heat before conversion to electricity. With current technology, storage of heat is much cheaper and more efficient than storage of electricity. In this way CSP plant can produce electricity day and night. If the CSP site has predictable solar radiation, then the CSP plant becomes a reliable power plant. The reliability can be further improved by installing a backup system that uses fossil energy. The backup system can reuse most of the CSP plant thus decreasing the cost of the backup system. If the mirrors or lenses in a CSP system do not move, then the focus of the mirrors or lenses changes because the Sun has different positions during the day. For this reason, CSP system requires a tracking system that follows the position of the Sun. The tracking system increases cost and complexity. With this in mind, different designs can be distinguished in how they concentrate the light and track the position of the Sun.