HOW CSP works

Back to Concentrating Solar Power

The diagram, below, shows the main components of a parabolic trough type of CSP plant.

How CSP plant works FPL Energy

Each of the 'solar collectors' is a trough-shaped mirror (with a parabolic cross-section) that tracks the sun and focuses the light on to a tube containing 'heat transfer fluid'—which is normally some kind of oil. The hot oil passes through a 'solar superheater' and 'steam generator' where the heat boils water and creates superheated steam. The steam drives the turbine, the turbine drives the generator and that feeds electricity into the electricity transmission grid.

Steam that comes out of the turbine is still quite hot. It is fed through a condenser where it is cooled down by cooling water from a cooling tower. The cooled water is fed back into the steam generator and solar superheater to create superheated steam again, and this is fed back into the turbine to generate more electricity.

If there is not enough sun, superheated steam may be created using a 'supplementary natural gas boiler' (see CSP: generating electricity without the sun).

Although this is not shown in the diagram, some CSP plants can store solar heat in melted salts (eg nitrates of sodium or potassium) so that electricity generation may continue at night or on cloudy days (see CSP: generating electricity without the sun).

Although this is not shown in the diagram, some CSP plants use sea water for cooling instead of a cooling tower. This has the effect of raising the temperature of the sea water so that, if a vacuum is applied, it gives off water vapour. The water vapour may be condensed to make fresh water—a very useful bonus in arid regions (see CSP and the desalination of sea water).

A more detailed description of how CSP plants work may be seen in the Quarterly of the Royal Academy of Engineering (Ingenia), vol 18, February/March 2004, pp 43-50. There is a companion article in the Quarterly of the Royal Academy of Engineering (Ingenia) vol 19, May/June 2004, pp 35-42.