Renewable Energy Sources Latest trends in research and development of renewable energy sources.

There are four main types of Concentrated Solar Power plants. Parabolic trough technology is the most widespread, accounting for 22 out of the 25 commercial CSP operations in the European Union at the end of 2011. It uses cylindrical-trough shaped mirrors to concentrate the sun’s rays onto an absorber tube containing a heat-transfer fluid.The remaining three commercial plants are tower plants. They use heliostats — huge, almost flat mirrors with a surface area of over 100 m2 arranged in their hundreds to concentrate the sun’s rays on a point at the top of a tower. All of them are in Spain: P510 (commissioned in 2006), P520 (commissioned in 2008) and Gemasolar (commissioned in 2011).

Europe is also working with Fresnel linear collector technology, which is a variant on parabolic trough technology, in that instead of using parabolic trough mirrors, deploys sets of small flat mirrors arranged in parallel, longitudinally. It also differs in that the absorber tube that concentrates the rays is stationary while the mirrors incline to follow the sun’s course. In Europe, the first commercial power plant to use this technology, Puerto Errado II, was commissioned in January 2012 and has a 30-MW capacity. These three types of power plant can be equipped with heat storage systems that use molten salts or phase-changing materials. The stored heat enables the power plant to continue producing electricity after sundown or during rare periods of cloud cover. The fourth, Dish Stirling technology, does not produce steam to turn a turbine, but uses at rough-shaped mirror concentrator to deflect the sun’s light on a receptor at the focal point of the dish. The device, which follows the sun’s light, can heat gas (helium or hydrogen) to temperatures in excess of 600C that drive a Stirling motor to produce electricity. In Spain a small demonstration plant based on Dish Stirling technology was commissioned in Casa de los Pinos.