Heliostats track and focus sunlight directly onto BrightSource&39's Luz Power Tower solar boiler, which contains a steam turbine to generate electricity.

California will soon lay claim to having the world's largest commercial solar thermal energy project in the world.

BrightSource Energy and NRG Energy subsidiary NRG Solar announced today that they're partnering on a 392-megawatt solar thermal project called the Ivanpah Solar Electric Generating System.

All the other moving parts to make the plant a go also seem to be in place.

NRG Solar has signed a memorandum of understanding to partner with BrightSource, and plans to invest over $300 million in Ivanpah. Ivanpah has signed power of purchase agreements with Southern California Edison and Pacific Gas & Electric. The U.S. Department of Energy meanwhile has given a "conditional commitment" for a $1.375 billion loan guarantee. All necessary federal and state permits for the project have been granted.

The Ivanpah thermal solar project actually consists of three interconnected solar thermal plants located on federally protected desert land roughly 50 miles northwest of Needles, Calif., close to the Nevada border, according to the California Energy Commission. The power plants will use BrightSource's system of heliostats concentrating light onto a central Luz Power Tower, wherein a solar boiler atop a central tower contains a steam turbine that generates electricity.

The deal is part of the push on the part of the U.S. Department of Interior's Bureau of Land Management to approve public land for large-scale solar-energy development.

The Ivanpah project when complete will double commercial solar thermal production capacity in the U.S., according to BrightSource.

Of course, that's not hard to do considering the U.S. currently has little thermal solar energy capacity for the commercial market. While there are some hybrid natural gas and solar thermal plants, as well as solar thermal plants like the 50-megawatt Nevada Solar One, mega plants simply have not yet been built.

In August, for example, the 250-megawatt Beacon Solar Energy plant near the Mojave Desert was approved. Arizona also has the 280-megawatt Solana Generating Station set to be operational by 2012. There are also several other solar thermal mega plants with 250-, 500-, and even 1,000-megawatt capacities in various development stages.

And while the Ivanpah might be able to claim a commercial first, it's the U.S. Army that is likely to have the largest thermal solar plant in the world. It's building a 500-megawatt solar thermal plant for Fort Irwin, Calif., but construction is not set to begin until 2012.