The Azimuth Project
Concentrated solar power



Concentrated solar power uses lenses or mirrors to concentrate sunlight, producing heat which drives a heat engine, usually a steam turbine, connected to a generator. This is a different energy conversion process than photovoltaic solar power, where solar radiation is directly converted to electricity without the use of, for example, an electric generator driven by a steam turbine. One should also distinguish between solar power — that is, ways of turning solar radiation into electrical power — and other uses of solar energy, e.g. heating household water.

For examples of concentrated solar power plants, already operational or planned, see our articles:


For an example of concentrated solar power created in a cheap and efficient way that circumvents the cost of creating doubly curved surfaces (so-called “parabolic discs”) see

Google is interested in concentrated solar power.


Nine units of SEGS (Solar Electricity Generating) plants built mid eighties through early nineties, in the Southern California deserts have been reliably generating a total of ~350 megawatts ever since.

With the recent permitting of other large scale CSP power plants also in California, more upgraded parabolic mirrors collector arrays will be used with a projected optical efficiency of 83%. See for example the Blythe solar power project recently approved by California Energy Commission, which will consist of four identical 250 megawatt power plants. This plant, built by and developed by Solar Millennium LLC and called the Blythe Solar Power Project (units 1 and 2), will be the largest solar power plant ever to be built at a single location:

The annual average solar to electric efficiency of the concentrated solar power plants is still lower than the conventional fossil-fuel fired power plants, but as technology improves, this efficiency figure may change.



Commercial Use

Concentrated solar power can be used to generate hot water as well as electricity, perhaps boosting overall efficiency. Two firms that do this are Cogenra and Zenith:

Zenith claims they get 75% overall efficiency.


Shrinking the cost for solar power, CNET News, May 2007 says:

Conventionally generated electricity ranges between 5 and 18 cents per kilowatt hour (the amount of money to get a kilowatt of power for an hour) but in most places it’s below 10 cents, according to the Energy Information Agency. Solar thermal costs around 15 to 17 cents a kilowatt hour, according to statistics from Schott, a German company that makes solar thermal equipment.

A solar thermal plant would need a facility to store the heat harvested in the day by its sunlight-concentrating mirrors so that the heat could be used to generate electricity at night. “You need the kind of system that can run in the evening,” Morse said. At some sites, such as Nevada Solar One, excess heat is stored in molten salt and released at night to run the turbine.

The plant, ideally, should be capable of generating about 300 megawatts of electricity. Those plants can churn out electricity at about 13 cents a kilowatt.

That’s still a relatively high price, so utilities would need to group two, three or more 300-megawatt plants together to share operational resources, Morse said. “They could share control rooms or spare parts,” he said. That would knock the price closer to 11 cents a kilowatt hour.

Surveys and Research

The ability of CSP to store energy in the form of molten salt may make it easier to blend intermittent sources like PV solar and wind power into the grid. The idea is that CSP can provide ‘dispatchable power’, filling the gaps left by these other intermittent sources:


Continuous power from solar energy was first demonstrated at the Department of Energy’s (DOE) Solar Two project in the late 1990s. I recently interviewed Bill Gould, CTO of CSP company Solar Reserve. Solar Reserve is now working to commercialize the molten salt thermal storage and solar receiver technology demonstrated at Solar Two, where Bill Gould served as project manager.

According to Gould, DOE’s intent at the Solar Two project was to demonstrate dispatchable power, not baseload power. Dispatchable power is power that can be called on when needed, in contrast to baseload power, which is essentially always on.

  • A study by the Fraunhofer Society with the title “Middle East and North Africa Region, Assessment of the Local Manufacturing Potential for Concentrated Solar Power (CSP) Projects” can be downloaded for free as a PDF

category: energy