Areva Solar is constructing a fourth 2.5-MW solar steam generator at its Kimberlina solar thermal plant in Bakersfield, CA, increasing both pressure and temperature in a modular demonstration of its Compact Linear Fresnel Reflector (CLFR) technology. The modular installation is a precursor to a 44-MW configuration to augment generation at the Kogan Creek coal-fired generator near Dalby, in Queensland, Australia, in a project that has received a $66 million commitment from the federal and state governments.

That installation, through a partnership with CS Energy, of Brisbane, will yield 334°C super-heated steam at 70 bar, and is expected to be the largest solar plant in the Southern Hemisphere.

"We can either boost a coal-fired plant's electricity production by five percent, or reduce the amount of coal they are using," says Robert Fishman, the CEO of Areva Solar, based in Mountain View, CA. "For stand-alone power plants, the last few percentage points of production is a big deal," he says. For combined-cycle gas-fired power stations, the CLFR can yield up to 250 Btu per kilowatt-hour heat rate improvement at peak boost, the company said.

According to William Conlon, the senior vice president of engineering at Areva Solar, the Areva system is 20% to 30% less expensive than a parabolic solar thermal process. Areva also has the capability to design its own custom boilers, and is the only solar steam boiler maker with an "S" stamp certification from the American Society of Mechanical Engineers to design steam boilers.

Areva bills its Kimberlina facility as the first of its kind in North America, and the first solar thermal plant to begin operation in California in nearly 20 years. Depending on the size of the installation, the new modular solar steam generator can be installed in a 6-month's time, Conlon said.

The Areva Solar Concentrating Solar Power (CSP) technology utilizes the Compact Linear Fresnel Reflector (CLFR) system.  Rows of solar reflectors focus sunlight onto boiler tubes in a linear receiver supported on towers above the reflector field.  The boiler tubes are housed in an enclosure with a tempered glass bottom and an insulated galvanized steel shell top cover.  The boiler tubes are coated with a selective coating to enhance both high solar energy absorption and low radiant heat loss.

Each reflector measures 16.1 x 2.25 meters and consists of five glass mirrors attached to a steel truss structure.  Six reflectors are coupled together in the north-south dimension to form an independently tracked row-segment; thirteen row-segments are mounted side-by side across the east-west width of each steam generator to form a segment.  There are four segments per solar boiler, which is approximately 390 meters long and 36 meters wide.  Each row of CLFR reflectors is driven by independently controlled motors to track the sun, or to rotate for convenient cleaning or “stowed” in a protective position.           

Steam from the Kimberlina solar steam generators is fed into an Elliott turbine previously installed at the site as a biomass plant now owned by Clean Energy Systems Energy and is currently selling electricity to Pacific Gas & Electric. Areva plans to increase total capacity of the Kimberlina facility to 24 MWt.

One notable advantage of the CLFR technology over other solar thermal systems is a smaller footprint. For a 200-MW plant, tower technology would require twice as much ground area as CLFR, and thin-film technology would require three times the footprint, the company indicates. This could be important for an installation at an existing industrial facility where open land is limited.

Prior to the Kogan Creek project, Areva installed the 9-MW Liddell thermal solar thermal station adjacent to Macquarie Generation's 2,000 MW power plant, near Muswellbrook, in New South Wales. Other installations are expected to follow the Kogan Creek project. "We can build about 700 MW of components per year, including support from our Las Vegas facility," said Conlon. The company thinks that the steam from its CLFR could be used in petrochemical, oil recovery, food, water desalination and mining sector applications.

Areva Solar purchased Ausra, based in Palo Alto, CA., in February 2010; Ausra built the first comprehensive U.S. solar thermal manufacturing plant, in Las Vegas, in 2008. Areva Solar is the global solar business unit of Areva, a Paris-based multinational involved in mining, uranium enrichment and reprocessing, nuclear power and other renewable energy sources including bioenergy, hydrogen, solar and wind. Publicly-traded Areva is owned 79 percent by the French government entity CEA, which is similar to the U.S. DOE.

Charles Thurston is a RenewableEnergyWorld.com contributor based in California.