Backers: Solar plant generates at night

Oct. 7, 2011 at 6:02 AM
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FUENTES DE ANDALUCIA, Spain, Oct. 7 (UPI) -- A new type of solar energy power plant that keeps working at night was inaugurated in Spain this week by its Spanish and Abu Dhabi backers.

Called Gemasolar, the $325 million "concentrated solar power" plant was launched Wednesday in a ribbon-cutting ceremony near Seville. The event was attended by King Juan Carlos I of Spain and Sheik Mohammed bin Zayed Al Nahyan, the crown prince of Abu Dhabi.

Built by a joint venture between Abu Dhabi's Masdar energy company and the Spanish engineering and construction firm Sener, the power plant was hailed by the two leaders as technological breakthrough because of a first-of-its-kind design that uses molten salt to keep turbines humming after sunset.

"During the day we capture the energy of the sun and we store that energy into a tank," Sener mechanical engineer Santiago Arias told CNN. "Then, whenever we want, regardless if it is day or night, we convert that energy into electricity."

The joint venture, Torresol Energy, has designed the generator to concentrate the reflected heat of an array of 2,650 large mirrors onto a receiver atop a 450-foot central tower. The sunlight heats it up to a temperature of 930 degrees Fahrenheit – much hotter than current solar generators.

Its makers say it can do this because it uses molten salt rather than oil to transfer the heat and produce pressurized steam in the turbine, thus significantly increasing the plant's efficiency.

Because the salt retains the heat up to 15 hours, it can power the turbine long after sunset.

Torresol says the plant has a capacity of 19.9 megawatts, enough to supply electricity to 27,500 households in southern Spain, and can operate for a total of 6,450 hours per year at full capacity. The plant is expected to save more than 30,000 tons of carbon dioxide emissions per year.

Torresol officials predicted the facility, which began operation in May, will reach 70 percent of its capacity next year, producing power at a rate they contend will be competitive with fossil fuel-burning power plants.

"Electricity production is much higher in summer than winter but of course it's designed to work all year round," Arias told French broadcaster EuroNews.

The technology is indeed cutting-edge and promising but pricey, said Judith Cherni, a researcher at the Center for Energy Policy and Technology at Imperial College in London.

In an article for the online journal International Business Times, Cherni praised use of energy-storing salts and the high capacity of the plant. But, she added, there are "a few issues" with its costs and size -- its vast array of mirrors take up 450 acres.

"At a cost of ($325 million), the replication of the Gemasolar system elsewhere in the world, particularly in Europe, may be a challenge," she wrote. "It remains to be seen whether further finance can be obtained before full validation of the technology is achieved, which may indeed require exposure to all types of weather and seasons."

The average cost per watt delivered is high compared to wind and geothermal energy, she noted, but only slightly more expensive than more traditional forms of solar energy.

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