It’s the holy grail of renewable energy: power, even when the sun don’t shine, or the wind don’t blow. Some companies are hoping advances in battery capacity will provide the answer, others are looking to flywheels, or hydrostorage. But SolarReserve, an 18-month old start-up based in Santa Monica, uses a fundamentally simpler technology: hot, hot salt.
SolarReserve’s solar power technology uses thousands of mirrors, called heliostats, to focus the sun’s energy on a tower filled with salt. The solar energy heats the salt over 1000 degrees F., turning it into a liquid, which then boils water to run a steam turbine, generating electricity.
But that’s just the half of it: SolarReserve’s plant can store that molten salt and release it to run the turbine whenever it is most cost-effective to do so — including at night, when traditional solar power is unavailable. They can do this because of the amazing heat-retention qualities of salt: 98% or higher if stored properly.
Brought to You by Rocket Scientists
SolarReserve was founded by US Renewables Group, a private equity firm, using technology licensed from Rocketdyne, which was created after World War II to explore German V-2 rocket technology. The company’s President is Terry Murphy, a former employee of Rocketdyne, and a rocket scientist himself (the more correct term, by the way, is “aerospace engineer”).
In the 1980s and 1990s, Rocketdyne teamed up with the Department of Energy, and various California utilities to build a solar thermal plant in Barstow, California, called Solar One. Solar One was the first power plant in the country to use the heliostat-tower model to generate steam. The plant ran from 1982-1988 and then, after being upgraded with molten salt technology and redubbed Solar Two, from 1996 to 1999.
When natural gas prices plummeted, the project became less attractive, because gas-fired electricity is the standard competitor to solar power. Then the concept was revisited by Rocketdyne (and its parent company, United Technologies), because of the recent energy crunch and increased interest in renewables. Last September, SolarReserve received $140 million in financing, and it hopes to have a 300 MW plant up and running as early as 2013, somewhere in the Southwest. That plant will use approximately 17,000 heliostats aimed at a tower 600 feet tall.
SolarReserve’s proposed plant faces the same hurdles and controversies that many solar plants do, namely space and water. The plant’s field of heliostats requires about 2 square miles of flat land. And to run the steam turbine will require water — not exactly abundant in the deserts where SolarReserve hopes to build.
But these obstacles, because they are shared by so many solar power companies, are also the focus of government action, including a plan by the Bureau of Land Management fast-track permitting on thousands of square miles of federal land. If SolarReserve can deliver on its promise of low-cost, continuous renewable energy, they may be the company to beat in the solar thermal industry.