The Department of Energy on Monday conditionally offered California solar company BrightSource Energy more than $1.37 billion in loan guarantees to support construction and start-up of three utility-scale concentrated solar power plants (CSP) in the Mojave Desert of southeastern California.

The loans will be provided by the U.S. Treasury’s Federal Financing Bank and guaranteed by the DOE, but BrightSource won’t get them unless it meets financial and environmental requirements for the proposed three-plant Ivanpah complex.

Requirements include receiving permits from the California Energy Commission (CEC) and the federal Bureau of Land Management—both of which are reviewing the project. The bureau already placed Ivanpah and five other large-scale solar projects on a fast-track approval process, but approval is not guaranteed.

Pending local, state, and federal regulatory approval, the new plants will generate approximately 400 megawatts (MW) of electricity using the company’s proprietary technology. This output would nearly double the existing generation capacity of CSP facilities in the U.S., the DOE’s Office of Energy Efficiency and Renewable Energy (EERE) said.

The Ivanpah Solar Complex will be located on federally owned land near the Nevada border. BrightSource will employ solar power tower technology, which uses thousands of flat mirrors, or “heliostats,” to concentrate the sun’s heat onto a receiver mounted at the top of a tower.

Water pumped to the receiver is boiled into steam, which drives a turbine to produce electricity. Solar power towers allow the capture of a greater percentage of solar energy than other solar thermal technologies. The first Ivanpah plant is expected to begin construction in the second half of 2010 and come on line in 2012. Commercial operation for the second plant is slated for mid-2013, with the third plant following later that year.

The BrightSource loan guarantee is the sixth conditional commitment for a loan guarantee for clean and renewable energy projects entered into by the DOE’s Loan Guarantee Program.

The company had filed a proposal earlier this month to shrink the footprint of the Ivanpah Solar Complex and reduce its environmental impact. The alternative design—submitted to the CEC and BLM as part of Ivanpah’s final permit process—came in response to concerns by groups over the environmental and wildlife impacts of the project.

The proposed changes would reduce the footprint of the third Ivanpah plant by 23% and trim the overall project by about 12%, while avoiding the area identified by environmental groups as posing the greatest concern. The new plans call for dropping the number of solar towers in the third Ivanpah plant from five to one, which brings the overall total number of towers in the power plant to three. It also cuts the number of heliostats by about 40,000. If approved, these changes would lower the site’s total gross capacity from 440 MW to 392 MW.

Sources: DOE, EERE, BrightSource Energy