Salting away renewable energy for future use

One of the biggest challenges in the solar energy field is how to store electricity from the sun. One solution may be no farther than your salt shaker.

SolarReserve, a California company, is pioneering a technology that uses molten salt as a medium for long-term energy storage.

10,347 mirrors surrounding tall tower with illuminated top chamber (Courtesy of SolarReserve)
Mirrors track the sun, directing its energy to the receiver atop the Crescent Dunes tower. (Courtesy photo)

The company’s Crescent Dunes solar power plant in Tonopah, Nevada, completed in 2015, is the first commercial plant in the United States to use this sophisticated storage technology.

The plant’s 110-megawatt capacity can power 75,000 homes and run for 10 hours from storage. That means overnight.

“The climate deal unveiled in Paris has the potential to catalyze a global energy transformation. It will further accelerate implementation of renewables around the world, including within emerging markets such as Africa, Latin America and Asia,” said SolarReserve chief executive Kevin Smith.

“Our proven U.S.-developed energy-storage technology deployed at the Crescent Dunes facility is already being used as a blueprint for projects in these emerging markets,” he added.

Infographic showing electricity-generation process (Courtesy of SolarReserve)
Sunlight heats salt to power steam generators to produce electricity. (Courtesy photo)

How does it work?

Mirrors that track the sun — 10,000 of them — reflect sunlight onto a receiver set atop a 195-meter tower. Liquid salt is piped through the heated receiver. The molten salt flows into an insulated thermal storage tank. As electricity is needed, the molten salt moves through a steam-generation system where water is heated to produce high-pressure steam. The steam drives a turbine that generates electricity. It works whether the sun is shining or not.

Shiny metal storage tank (Courtesy of SolarReserve)
A huge tank at Crescent Dunes stores salt used to extend electricity storage capacity. (Courtesy photo)

The steam-generation process is identical to those used to produce electricity from gas, coal or nuclear power plants, but it is 100 percent renewable, without harmful greenhouse gas emissions.

“So far, in the industry, that’s the state of the art — molten salt storage,” University of South Florida solar power expert Yogi Goswami told the Los Angeles Times.

The molten salt storage technology deployed by SolarReserve resulted from decades of design and testing by U.S. aerospace companies Rockwell International, Rocketdyne, Boeing, Pratt & Whitney and Aerojet.

Bright sunlight reflecting from top of tall tower surrounded by mirrors (Courtesy of SolarReserve)
South Africa’s Redstone solar thermal power plant will look like this artist’s rendering when it’s completed in 2018. (Courtesy photo)

SolarReserve has advanced projects that use molten salt storage underway in other countries, in partnership with governments and private energy providers. Its Redstone thermal power project in South Africa’s Northern Cape province is slated for completion in 2018. Another project is being built in Chile. And the company recently sealed a deal with Shenhua Group to build 1,000 megawatts of advanced solar energy installations in China.