Solar thermal power

Solar thermal power systems are based on concentrating solar radiation to turn it into thermal energy and, in a conventional thermodynamic cycle, to generate electricity.

There are currently four technologies which are commercially available as concentration systems:

• Parabolic trough concentrators: these are made up of solar concentrators which track the sun along an axis and reflect its radiation to a receiver: a pipe through which a heat transfer fluid is pumped.

Commercially speaking, this is the most mature and frequently-used technology, although new developments concentrate on finding alternatives to synthetic oils as the heat transfer fluids to increase their efficiency.

• Central or power-tower systems: these comprise a field of heliostats which, by tracking the sun along two axes, reflect radiation onto a solar receiver at the top of a tower.

Although there are fewer power-towers at present, this technology is the one most likely to undergo technological development.

• Parabolic dish collectors: these are made up of a parabolic reflective surface which concentrates the sunlight at a single point, coupled to a Stirling engine to generate electricity.

These systems, initially designed for isolated applications, are finding acceptance in facilities connected to the grid, given their high level of performance and modularity.

• Fresnel linear reflectors: these use long, parallel lines of mirrors which concentrate the sun’s rays onto a fixed central receiver.

This is one of the less-developed kinds of reflector but, over the mid-term, they might be an alternative to parabolic trough systems, given their simplicity, reduced cost and better use of available land.