BrightSource Energy announced last week that the Ivanpah Solar Electric Generating System (ISEGS) produced its first energy output when one of three stations was synchronized to the power grid for the first time. NRG Energy, BrightSource Energy, and Google are equity investors in the plant; the Department of Energy has provided loan guarantees.
“Given the magnitude and complexity of Ivanpah, it was very important that we successfully complete this milestone showing all systems were on track,” said Tom Doyle, president of NRG Solar. “We couldn’t be more excited about achieving ‘first sync,’ and we share this success with our project partners, BrightSource and Google, as well as Bechtel, which is responsible for engineering, procurement, construction and commissioning on the project.”
Located in California’s Mojave Desert, Ivanpah spans 3,500 acres of public land. BrightSource said that when fully operational, the 392-MW (377-MW net) plant will generate enough electricity to power 140,000 homes annually.
BrightSource’s system uses proprietary software to control thousands of tracking mirrors, or heliostats, to concentrate sunlight onto a water-filled boiler that sits atop a tower. The steam produced drives a conventional turbine to produce electricity.
BrightSource said Ivanpah’s three power-tower units will nearly double the amount of commercial solar thermal energy capacity now operating in the United States.
Because solar-thermal—or or concentrated solar power (CSP)—plants produce heat rather than directly producing electricity (as photovoltaic plants do), they can store energy in heat form—a much cheaper option that storing PV-produced energy in batteries for use when the sun goes down. Josh Dzieza writing in the Daily Beast points out that Ivanpah does not include such storage, but a plant under construction in Arizona does. The Abengoa Solar Solana plant will store in molten salt sufficient heat to generate electricity for six hours. The company says that its parabolic mirror technology allows its molten salt loop to operate at 500°C.
Kevin Bullis in MIT Technology Review questions the economics of the Ivanpah project. He writes, “From one perspective, things don’t look good. When you calculate the amount of power the plant is likely to produce over its lifetime, the cost per kilowatt-hour is likely to be much higher than for fossil-fuel power. It’s even likely to be higher than the cost of power from solar panels, thanks to the fast drop in solar-panel prices in recent years. If costs don’t come down—and decreasing the costs of mirrors and steam turbines is hard to do—solar thermal power might prove to be a dead end.”
He acknowledges, however, the benefits of the energy-storage capabilities of CSP plants, writing, “If the US decides to abandon fossil fuels in a bid to slow climate change, solar thermal might prove to be one of the most practical ways to make up for the intermittency of solar panels and wind turbines.”