Abengoa’s Solana solar thermal plant, the world’s largest parabolic trough concentrating solar power (CSP) plant and the first in the U.S. with thermal energy storage, began commercial operations on Monday.

The 280-MW plant, near Gila Bend in Arizona about 70 miles southwest of Phoenix, employs molten salt to store about six hours of thermal energy at full power, allowing the facility to continue operating during periods of peak evening demand. The addition of thermal storage also allows the facility to smooth out any intermittency in generation as a result of cloudy periods during the day.

The three-square mile facility employs 2,700 parabolic trough mirrors and a pair of 140-MW steam turbines. Heated oil from the mirrors is used to heat molten salt in six pairs of hot and cold tanks with a capacity of 125,000 metric tons.

Solana will sell all its power to Arizona Public Service, the state’s largest utility, through a 30-year power purchase agreement. The facility cost approximately $2 billion to build, and was financed in part with a $1.45 billion loan guarantee from the Department of Energy (DOE).

Abengoa currently has 1,223 MW of CSP in operation worldwide, and is also building a 280-MW CSP plant near Barstow, California. The Mojave Solar Project, due to come online next year, also received a DOE loan guarantee, this one for $1.2 billion, but will not employ molten salt storage.

—Thomas W. Overton, gas technology editor (@thomas_overton, @POWERmagazine)