Solar thermal power (electricity) generation systems collect and concentrate sunlight to produce the high temperature heat needed to operate conventional steam-cycle plants to generate electricity.  A good primer on this is available from the U.S. Energy Information Administration ( at

A more detailed description is available on Wikipedia at

The technology seems simple, but the details are complex.  Large systems are needed to produce electrical energy at competitive costs. High temperatures increase the efficiency, but result in high pressures for the fluid that is used, and fluids that can be toxic. 

Since these systems use various means to concentrate the sunlight on a receiving surface, require a means to keep the sun focused on the receiving area and they need direct sunshine.

Many of these large systems have had difficulty the anticipated energy and/or have had operational problems. One large and expensive system in Arizona has been in the news: Underachieving Solana Solar Plant Keeps Polluting Arizona's Air