29/05/2015
Thermal Energy from Sun.
Thermal energy from the Sun is intercepted by a concentrator which focuses the energy on a heat absorber containing the working fluid, usually a synthetic oil, which is heated by the solar radiation to a high temperature typically 400° C. The system may use a binary cycle in which the heated oil is passed through a heat exchanger to raise steam which is used to drive a conventional turbine and generator in a separate circuit.
To maintain the thermal efficiency of the turbine, the working fluid leaving the heat exchanger should not be allowed to cool down. Solar plants are therefore supplemented by gas-fired boilers which generate about a quarter of the overall power output and maintain the temperature overnight.
Several such installations in modules of 80 MW are now operating and solar conversion efficiencies of between 15% and 23% have been achieved. Each module requires about 50 hectares of land and needs very precise engineering and control. Power costs are two to three times that of conventional sources.
