Solar Thermal Electricity, also known as Concentrating Solar Power (CSP) allows to convert sun radiations into thermal power, through collectors made of reflective mirrors, that concentrate sunbeams into an absorber. Collector and absorber form together the Sunbeams Collector. The third component is a system that moves the collector in order to chase the apparent motion of the sun.
Depending on the temperature that the fluid have to reach into the receiver pipe, and according to the usage of the produced energy, there are different types of heat-up liquids: from pressurized water for uses that need no more than 100° C, to mineral or synthetic oils for industrial thermal uses up to 400° C , and lastly, more than 600° C by using molten salts (sodium and potassium). This heat-transfer liquid is object of several studies and research, finalized to the improvement of its properties and its performance; in some cases it has been heated up to more than 1000° C.
With the exception of Dish Stirling technology, it is quite evident that, with the other collectors, solar radiation is not directly converted in energy, but it is collected first as thermal energy. By this way, energy can be easily stored in appropriate storage systems, and then exploited as thermal or transformed in electricity. The storage capability, or rather its dispatchability, proper to CSP systems, makes the employment of this technology more convenient, compared to the other renewable sources.
The collected thermal power, available also at high temperatures, can be destined to several industrial usages. Thermal energy can be converted in electricity through Rankine Cycles (by using steam or organic liquids). However, other thermal energy uses must be mentioned: heating fluids in the transforming industry; air-conditioning of wide spaces trough absorbing cooling generator systems; unsalted water and hydrogen production.
There are different CSP technologies according to the position of sunbeam collector and the absorber:
- Parabolic troughs
- Linear fresnel
- Dish stirling
- Tower systems
