The 500-megawatt Hidden Hills Solar Electric Generating System would be built in two 250-megawatt phases on 5.12 square miles of privately owned Mojave Desert land in California.

BrightSource Energy, the California startup that is building the first large-scale solar thermal power plant to break ground in the United States in 20 years, filed a license application with California regulators to build a second huge solar complex that features new technology.

The 500-megawatt Hidden Hills Solar Electric Generating System would be built in two 250-megawatt phases on 5.12 square miles of privately owned Mojave Desert land in California’s Inyo County on the Nevada border. The site is 45 miles west of Las Vegas and north of BrightSource Energy’s Ivanpah facility now under construction on the California side of the border.
The project is the first to seek approval from the California Energy Commission since regulators rushed to approve nine large solar thermal power plants last year so their developers could qualify for billions of dollars in federal loan guarantees. The loan guarantee program is set to sunset on Sept. 30 and Hidden Hills will test financiers’ appetite for such projects absent such a subsidy.
BrightSource, which is backed by French energy giant Alstom, Morgan Stanley, Google, Chevron and NRG Energy, filed for a $250 million initial public offering in April and has signed contracts to deliver 2,610 megawatts of electricity to utilities Pacific Gas & Electric and Southern California Edison.
The company deploys vast fields of mirrors called heliostats to focus the sun’s rays on a water-filled boiler that sits atop a tower. The resulting steam drives an electricity-generating turbine.
In a sign that solar technology is unlikely to stand still for long in the race to bring more efficient power plants online, BrightSource has increased the height of its “power tower” at the Hidden Hills project to 750 feet from the 459-foot height of those being built at Ivanpah. Each tower at Hidden Hills would be surrounded by a field of 85,000 heliostats.
“The new, higher, 750-foot solar power tower allows the heliostat rows to be placed closer together, with the mirrors at a steeper angle,” the company stated in its license application. “This substantially reduces mirror shading and allows more heliostats to be placed per acre. More megawatts can be generated per acre and the design is more efficient overall.”
BrightSource on Wednesday announced it would incorporate molten salt storage in its power plants to extend their operating hours past sunset. No mention of such a system was made in the Hidden Hills application but its addition would most likely depend on a request from the utility that purchases the complex’s electricity.
The company has set out an ambitious construction schedule, stating that it anticipates ground would be broken by the third quarter of 2012 and Hidden Hills would begin generating electricity in 2015. In contrast, it took more than three years for state and federal regulators to approve the Ivanpah project, which is being built on land managed by the Interior Department.
BrightSource will largely avoid the feds involvement by building on land leased from a private owner. The company also apparently hopes to sidestep disputes over the impact of its power plants on the imperiled desert tortoise, a controversy that has dogged the Ivanpah project. According to its license application for Hidden Hills, initial surveys found only two desert tortoises on the project site.
A traditional BrightSource’s LPT power tower solar thermal system uses a field of software-controlled mirrors called heliostats to reflect the sun’s energy to a boiler atop a tower to produce high temperature and high pressure steam. The steam is used to turn a conventional steam turbine to produce electricity. In a BrightSource SolarPLUSTM plant, the steam is directed to a heat exchanger, where molten salts are further heated to a higher temperature, thus efficiently storing the heat energy for future use. Later, when the energy in storage is needed, the heat stored in the molten salts is used to generate steam to run the steam turbine.

BrightSource Energy, Inc. designs, develops and sells solar thermal power systems that deliver reliable clean energy to utilities and industrial companies. The company has contracted to sell approximately 2.6 gigawatts of power to be generated using its proprietary solar thermal technology.