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After almost three years of construction, $2 billion in funding, a controversial Department of Energy loan guarantee, and 2,000 jobs created, a large and unique solar farm about 70 miles southwest of Phoenix, Arizona, is now ready to produce power. This is Solana, developed by Spanish engineering powerhouse Abengoa, and it uses hundreds of parabolic-shaped mirrors that concentrate the suns rays to produce electricity as well as an industry first deployment of molten salt-based thermal energy storage technology.

Most of the solar farms that use these types of mirrors and lenses to concentrate sun light to produce heat and drive turbines, are turning to energy storage technologies to produce power when the sun goes down or behind a cloud. But Solana is the first one to actually start using it in the U.S. In contrast to this type of concentrating solar technology, solar panels convert the sun’s light directly into electricity.

At Solana, the energy storage technology uses tanks of molten salt that hold high amounts of heat for long periods of time. When the sun is out full blast, the solar farm produces a lot of heat and pumps some of that into the molten salt tanks. When the sun goes behind a cloud, or at night, the farm can turn to the energy storage tech to offer power for another six hours. One of the criticisms of solar tech is that it can’t provide continuous power the way that a coal or natural gas plant can, so energy storage tech is a way to make solar more competitive.

The power from Solana will be enough to provide electricity for 70,000 households, or 280 MW. Arizona’s largest utility Arizona Public Service (APS) will purchase all of the solar power from the farm.

The farm is using “parabolic trough” technology, which is a type of tech that has been used in a variety of solar farms throughout the years. The other option for these large concentrating solar farms is “power tower” technology which uses mirrors and lenses to focus light onto central towers. BrightSource uses this tech at its Ivanpah solar farm near Las Vegas.

The farm cost $2 billion to build and was part of the controversial loan guarantee program from the Department of Energy. Abengoa was awarded a $1.45 billion loan guarantee in 2010 — the largest for clean power out of that program. Loan guarantees are when the DOE commits to back up a loan if the company defaults.

Now that the farm is built and it’s on time, it’s an example of how the DOE loan program was instrumental in getting clean energy technology deployed. The program also supported BrightSource’s farm.