Concentrated solar thermal is again making the news, with the world’s largest parabolic trough array with thermal storage – opening for business in Arizona.

The 280MW Solana Solana Generating Station constructed by Spanish group Abengoa has six hours of molten storage capacity that will allow it to produce energy into the evening, and deliver output according to the needs of the customer.

“Solana is a monumental step forward in solar energy production,” said Don Brandt, the president of APS, the local utility. “This provides a huge boost toward our goal to make Arizona the solar capital of America.”

The opening of Solana is one of three major new projects that are coming on stream, as CSP begins to recover the ground lost, and projects ceded, to solar PV when that technology delivered massive cost reductions in recent years.

The 375MW Ivanpah project, the largest solar power tower in the world, has delivered to the grid for the first time and is due to start full operations within the next few months, as is the 110MW Crescent Dunes facility in Nevada, which will be the world’s largest solar power tower project with molten salt.

Also, the first commercial scale solar thermal plant with storage, the Gemasolar plant in Spain, recently marked its second anniversary by delivering electricity 24/7 for 36 consecutive days. On Thursday, Dr Keith Lovegrove, the head of solar thermal at Australia’s IT Power, said CSP with storage is ”virtually unbeatable” as a technology, and the costs are coming down quickly.

The Solana plant’s CSP technology produces electricity by collecting the sun’s heat to create steam that turns conventional turbines. It has 2,700 parabolic trough mirrors, which follow the sun to focus its heat on a pipe containing a heat transfer fluid.

This fluid, a synthetic oil, can reach a temperature of 735 degrees Fahrenheit. The heat transfer fluid then flows to steam boilers, where it heats water to create steam. The steam drives two 140MW turbines to produce electricity, much like a traditional power plant.

APS says that shat separates Solana from other solar power plants is the ability to store the heat from the sun up to six hours for electrical production at night. In addition to creating steam, the heat transfer fluid is used to heat molten salt in tanks adjacent to the steam boilers.

The thermal energy storage system includes six pairs of hot and cold tanks with a capacity of 125,000 metric tons of salt, and the molten salt is kept at a minimum temperature of 530 degrees Fahrenheit.

When the sun goes down, the heat transfer fluid can be heated by the molten salt to create steam by running it through the tanks instead of the field of parabolic mirrors.

APS says this means that Solana can deliver power whenever its customers need it most, including evenings.

The opening of Solana boosts the solar capacity operated by APS to more than 750MW. It as 1.1 million customers.

World's Largest Solar Thermal Plant With Storage Comes On-line