The switch has been flipped on a massive solar array field near Phoenix, producing up to 280 megawatts of electricity - enough to power 70,000 households.

Arizona's largest public utility, Arizona Public Service (APS), will purchase all of the electricity produced by the solar plant for 30 years through a power purchase agreement with Abengoa Solar, the company that built the array.

The solar array, financed in part by a Department of Energy loan guarantee, is the county's first large-scale solar plant with thermal energy storage system. Through the use of molten salt thermal energy storage the plant can continue to produce steam to drive the turbine and provide electricity for six hours without the concurrent use of the solar field.

The Solana solar array field covers three square miles with about 3,200 mirrored parabolic trough collectors. Each collector is about 25 feet wide, 500 feet long, and 10 feet high.

The Solana solar plant will generate enough clean energy to power 70,000 households and will prevent about half a million tons of CO2 from being emitted into the atmosphere per year, according to Abengoa Solar. Solana received a federal loan guarantee of $1.45 billion to build the plant.

The construction of the plant created more than 2,000 jobs and a national supply chain that spans 165 companies in 29 states.

The Solana solar power plant

The energy storage system is seen as a turning point for renewable energy, as it is a tangible demonstration that solar energy can be stored and dispatched on demand.

Construction of the Solana solar array, which is about 70 miles southwest of Phoenix, began in 2010 and had a final cost of $2 billion.

A video showing how the plant was constructed and generates solar power.

Abengoa Solar described the array as the world´s largest parabolic trough plant. The solar arrays use parabolic shaped mirrors mounted on moving structures that track the sun and concentrate its heat. That heat is used to heat water into steam, which is then used to power a conventional steam turbine. Being able to store the power allows the plant to continue distributing energy when the sun goes down or is blocked by poor weather.

"These six hours will satisfy Arizona's peak electricity demands during the summer evenings and early night time hours," Abengoa Solar said in a statement. "Dispatchability also eliminates intermittency issues that other renewables, such as wind and photovoltaics, contend with, providing stability to the grid and thus increasing the value of the energy generated by [the plant]."

The parabolic mirrors of the plant.

Abengoa Solar has two commercial solar power towers, 13 50MW trough plants, a solar-gas combined-cycle plant and five photo-voltaic plants in commercial operation worldwide. Abengoa has concentrated solar power plants under construction in the U.S., South Africa, Spain, and the United Arab Emirates, with a total capacity of 810 megawatts.

Lucas Mearian covers storage, disaster recovery and business continuity, financial services infrastructure and health care IT for Computerworld. Follow Lucas on Twitter at @lucasmearian or subscribe to Lucas's RSS feed . His e-mail address is lmearian@computerworld.com.

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