Solar power, or solar energy, uses energy from the sun directly, such as heating and lighting for homes and offices, or indirectly, such as the conversion of sunlight into electricity. The four main distinct solar technologies are: solar heating, solar lighting, photovoltaics (PV) and concentrating solar power (CSP).
Today, both CPV and CSP have reached a high degree of competitiveness. The biggest drawback of CPV is that electricity can only be produced during sunshine. With CSP, on the other hand, it is possible to accumulate and store the solar energy during sunshine and produce electricity on demand. This is a major advantage ideally offering the same dispatchability characteristics of traditional fossil-fuel based plants.
However, CPV stands out for its ease of implementation and high conversion efficiency of solar energy into electricity even in small to medium size installations. Efficiency which is likely to increase considerably in coming years as a result of continuos progress in the technology of multi-junction cells.
Parabolic trough systems produce heat or electricity by using large arrays of mirrors to concentrate the sun’s thermal energy onto a line, the receiver. The solar radiation heats up a heat transport fluid (HTF) within the receiver tube. The hot HTF usually feeds an energy storage accumulator. A classical steam cycle uses the stored energy in order to produce power in a steam turbine-generator package. 50MW is nowadays a classical size of CSP plants in Europe. In the USA plant sizes of 200 - 400MW are not uncommon.
In the case of CPV, the receiver consists of a series of multi-junction, high efficiency solar cells placed on a ad hoc structure which directly transforms solar energy into electricity. Installations size can vary from a few hundred of kilowatts to hundreds of MW when deployed systematically on a large scale.
Since concentrating solar systems require direct-beam sunlight and their performance is directly proportional to solar irradiation, the technology is best suited to areas of the world with the most sun as shown in the picture below.