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power & industrial
Arizona Utility Aims High for Solar Array
280-MW plant would be largest of its kind, but tax credits are key to advancement
By Thomas F. Armistead
Solana project will require investment tax credit to work.
Abengoa Solar
Solana project will require investment tax credit to work.
An Arizona utility is reaching for the sun with an agreement to purchase all the output of a new 280-MW concentrating solar powerplant scheduled to begin operation in 2011. The Solana Generating Station, to be built 70 miles southwest of Phoenix, will be larger than any solar powerplant operating in the world today, the utility’s officials say.

Spain-based Abengoa Solar Inc. will build, own and operate the facility, and Phoenix-based Arizona Public Service Co. will purchase its electricity for 30 years. Total revenue will be around $4 billion, say Abengoa officials.

Engineering, procurement and construction will be performed by Spain-based Abener with collaboration by Abencs, St. Louis, a contractor controlled by Abengoa. The construction schedule is about 18 months, says Fred Morse, Abengoa’s Washington, D.C.-based senior adviser for U.S. operations. He declined to reveal construction costs.

The plant will operate with Abengoa’s proprietary parabolic-trough-mirror design, with mirrors from a manufacturing plant that Abengoa will build in the U.S. at a site to be selected, Morse says. Abengoa has been doing its own research and development on concentrating solar power (CSP) for two decades, he adds.

Updated Design

Curved mirrors in a trough shape track the sun and concentrate its thermal energy on a receiver pipe that carries a heat-transfer fluid. The trough assembly for this plant will be about 450 ft long, Morse says. Heated to about 700°F in the collector array, the Therminol fluid will circulate to a heat exchanger, where it will turn water into steam to drive a turbine. Salt heated by another heat exchanger will be stored in a tank. At night or other times when the sun is not shining, the salt will be used instead of Therminol to perform the steam flash conversion.

The 13.8-MW Solar Electric Generating System 1 (SEGS 1) plant constructed in the Mojave Desert first demonstrated the technology in 1985. A second SEGS plant, 30-MW SEGS 2, has been in continuous operation since 1986, according to Israel-based Solel, the successor to original developer LUZ Industries.

Array will be 450 ft long.
Abengoa Solar
Array will be 450 ft long.

Solana “will look the same as SEGS to the naked eye,” says Morse, but it will be technically improved over the earlier model. The receiver tube will offer higher performance, for example, and the structure will be lighter and less costly, he says. “We’ve also learned how to do it so you have less field assembly,” he adds.

The Solana project will cover about 1,900 acres at Gila Bend, Ariz., and will create about 1,500 construction jobs, according to Abengoa officials.

Arizona Public Service now provides 131.5 MW of renewable energy, and is pursuing the state’s Renewable Energy Standard goal of obtaining 15% of the total electricity sold from renewable sources by 2025. The Solana project will help, but only if Congress extends the 30% investment tax credit, now scheduled to expire in December, says Morse (see story, p. 7). “That takes 30% of the capital cost off the top,” he explains. “The project dies without that credit.”

Concentrating Consortium

In pursuit of the goal, Arizona Public Service also built the first CSP project in the U.S. in 20 years, a 1-MW project at Red Rock, Ariz., says Steven Gotfried, APS spokesman. The utility also is coordinating a multistate consortium of energy service providers requesting proposals for a utility-scale concentrating solar powerplant.

"The Solana Generating Station will be the largest of its type now operating anywhere in the world."

The Southwest Energy Service Provider’s Consortium for Solar Development issued the RFP in December for 250 MW of CSP power to be located in either Arizona or Nevada. The group’s members include Arizona Electric Power Cooperative, Salt River Project, Southern California Public Power Authority, Tucson Electric Power and Xcel Energy. Proposals are due March 19. Gotfried declined comment on the amount of interest shown by developers.




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