October 7, 2013 | By Barbara Vergetis Lundin


Arizona Public Service's (APS) 280 MW Solana Generating Station near Gila Bend is being hailed for its use of concentrated solar power (CSP) technology and thermal energy storage.

Solana is one of the largest power plants of its kind in the world, using CSP technology to produce electricity by collecting the sun's heat to create steam that turns conventional turbines. The process begins with 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 temperatures of 735 degrees Fahrenheit. The heat transfer fluid then flows to steam boilers, where it heats water to create steam. The steam drives two 140 MW turbines to produce electricity, much like a traditional power plant.

Unlike other solar-powered electrical plants, the Solana Generating Station keeps the sun's energy working after dark to produce electricity for APS customers across Arizona. It does this by using CSP and energy storage to capture the sun's heat and save it until it is needed most unlike more common photovoltaic technology that needs direct sunlight in order to produce electricity. The CSP technology enables Solana to produce electricity at full capacity for up to six hours after sunset, including the early evening hours when customer demand for power typically peaks. 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.

"Solana is a monumental step forward in solar energy production," said Don Brandt, APS president and CEO. "Solana delivers important value to APS customers by generating power when the sun isn't shining. It also increases our solar energy portfolio by nearly 50 percent. This provides a huge boost toward our goal to make Arizona the solar capital of America."

With the addition of Solana, APS will have 750 MW of solar power on its system by the end of 2013.

For more:
- see this brief

 

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