In the last major step before the world’s largest solar plant opens in California’s Mojave Desert, engineers at the Ivanpah solar farm, 40 miles south of Las Vegas, are testing the huge water boilers on top of the plant’s three 459-foot towers.
The $2.2 billion project is scheduled to start delivering electricity to the power grid by the end of the year, said Joseph Desmond, vice-president of marketing for Oakland’s BrightSource Energy, the plant’s developer. Ivanpah is owned by BrightSource, NRG Energy and Google, and is being built by Bechtel. The plant’s electricity will be purchased by Pacific Gas and Electric, in Northern California, and by Southern California Edison.
It will deliver 377 megawatts of power, enough electricity for 140,000 houses, said Desmond, and about the same output as a medium-sized natural gas-fired plant.
“This is a major milestone for renewable energy development in North America,” said Carl Zichella, senior policy analyst at the Natural Resources Defense Council, an environmental group in San Francisco. “A plant like this creates economies of scale that will reduce the costs in the future.”
Ivanpah, which received a $1.6 billion loan guarantee by the federal Department of Energy in 2011, is one of seven massive solar plants scheduled to open in California by 2014. In the works for years, together they’re part of the coming of age of big solar in the United States.
On Thursday, U.S. Sen. Edward Markey, D-Mass., introduced a bill to require every utility in America to produce 25 percent of its electricity from renewable sources by 2025. Environmentalists cheered the news, although similar bills in Congress have failed in recent years due to opposition from Republican leaders and from lawmakers who represent regions that do not have as much wind or sunshine as other areas and worry that such rules would increase monthly utility bills for consumers.
For the next two to three weeks, engineers at Ivanpah will painstakingly point tens of thousands of mirrors onto a boiler full of water on Unit 1. Their goal: to heat the steam inside to a searing 1,400 degrees Fahrenheit, said Tim Fisk, Ivanpah project director. That’s six times hotter than boiling water. The high-pressure steam powers a turbine, which in turn generates electricity. The “loading of the boiler,” as this step is known, is the last major step before Unit 1 can start delivering electricity to the grid. Afterward boilers on the plant’s other two units will undergo similar tests.
At each of the plant’s three units, 100,000 to 120,000 mirrors are arranged in a circular pattern around a tower as tall as a 45-story building, on top of which sits the boiler. The mirrors are controlled by computers, which move them during the day, sunflower-like, so that they’re always picking up the sun’s rays and sending them to the boiler, a 120-foot high black rectangle of steel tubes.
The technology is called concentrating solar thermal, and is different than the photovoltaic solar panels commonly used on rooftop installations, which transform the sun into electricity through a chemical reaction. Similar plants exist in Abu Dhabi and Spain.
Concentrating solar thermal technology offers the promise of getting around one of solar energy’s shortcomings. Because the sun only shines during the day, plants stop producing electricity at dusk. Concentrating solar thermal plants can be built to store heat in large vats full of molten salt, and can draw that heat to continue producing electricity for a few hours after sundown.
“When you add storage, you’re essentially making this a power plant just like a natural gas plant, meaning it has the ability to be flexible, controllable, and deliver power when it’s most valued and most needed onto the grid,” said Desmond.
Ivanpah doesn’t include storage, but the first U.S. plant with storage, the Solana solar farm, opened 70 miles southwest of Phoenix, in Gila Bend, Arizona, in September.
Despite the advantages of large solar plants in the desert, Ivanpah, which is located on about 3,500 acres of federal land owned by the Bureau of Land Management, ran into challenges. While the Mojave Desert is one of the best solar resources in the world and is located relatively near dense population centers like Los Angeles that need the electricity, parts of the desert are also home to endangered species.
“From the get-go, we knew that the Ivanpah project was located in an area that had fairly high density of desert tortoise in it,” said Ileene Anderson, a biologist with the Center for Biological Diversity, an environmental group in Los Angeles.
Worried that habitat disruption would impact desert tortoises, which are classified as “threatened” under the Endangered Species Act, the group testified against the project. After it was reduced in size, it obtained federal and state permits, and construction began in 2010.
Initial surveys had led BrightSource officials to believe that they’d find 30 tortoises on the site where they were building the plant. But rains created favorable conditions for tortoises, and resulted in the company finding 173 instead. The company transferred the tortoises to pens and later moved them back onto wild land. More than 50 additional tortoises have been born in captivity.
“If you take into account the care and monitoring of all the tortoises involved in the program, it works out to be about $55,000 per tortoise,” said Desmond.
The tension between protecting threatened species and pushing for large-scale solar plants in the desert put environmental groups at odds with each other during Ivanpah’s construction.
“There have been genuine local concerns about the location of some of the earlier projects that have led people to feel not so committed to some of the renewable energy options,” said Zichella. “There’s no such thing as an impact-free energy source. If we’re going to deal with climate change, we have to understand that. And if we can choose the locations for these facilities very carefully, we can avoid a lot of the biggest problems.”
Efforts are underway to find the best places for large renewable energy projects. The Interior Department has identified “solar energy zones” on public land in six southwestern states. These 300,000 acres are close to transmission lines and have fewer threatened species than other locations.
In California, government agencies and environmental groups are working to identify large tracts in the Mojave Desert suitable for both wind and solar plants. The plan would also set aside land for desert species. A full draft of the plan’s environmental review is expected this fall.
“We’re engaged in that process and very much looking forward to help crafting a good plan that allows for renewable energy development, as well as allowing for good, strong conservation to occur,” said Anderson.
Largest Solar Farms in the World
When it opens in the next few months, the Ivanpah solar farm will be the largest in the world, providing 370 megawatts - enough electricity for 140,000 homes. The largest now:
California Valley Solar Ranch
Charanka Solar Park
CPI Golmud Power Station
CPI Huanghe Hydropower Co.
Mesquite Solar 1
Additional reporting contributed by KQED Science radio reporter Lauren Sommer. Tortoise footage: Stephen M. Wessells, USGS.