Pacific Gas and Electric made its second deal of the week today, agreeing to buy 553 megawatts of solar power from Solel Solar Systems' planned Mojave Solar Park.

The solar thermal project will deliver enough power to supply 400,000 homes in northern and central California when it is fully operational.

The solar thermal park won't be ready until 2011. It's to cover up to 6,000 acres, or nine square miles, in the Mojave Desert, relying on 1.2 million mirrors and 317 miles of vacuum tubing.

Solel is to break ground on the project in mid 2009.

The plant is to use Solel's solar thermal parabolic trough technology, which has powered nine operating solar power plants in the Mojave Desert over the past 20 years (see Solel gets large new order for solar thermal receivers).

The nine plants currently generate 354 megawatts of electricity annually.

"If you use solar thermal, you are changing the name of the game. Thousands of megawatts can be built here in California, and even in peak time be used in the summertime," Solel chief executive officer Avi Brenmiller told Cleantech.com.

Financial terms of the deal were not disclosed, but Brenmiller says he can offer a better price and better efficiency with solar thermal over photovoltaic.

"The raw materials we are using—glass, metal, cement—are commodities. There are almost no limits to the amount we can use," he said.

The Mojave park will use parabolic mirrors to transfer heat to a fluid that is then used to run a steam powered turbine, which can produce electricity for the utility's power grid.

Some of the transmission infrastructure is already built. The electricity generated by Mojave Solar Park will use infrastructure originally made for the now dormant coal-fired Mojave Generation Station.

Although the Mojave park is big, it certainly won't be the last of its kind. Brenmiller expects additional contracts similar to the Mojave park, in the hundreds of megawatt sizes, in the next 6 months to 2 years.

"This is the largest, it's modular, but it's the largest we've built. This is scalable. With growth, cost goes down," he said.

And these projects are built to last.

Brenmiller said that the company's solar thermal parks, some already operating for the past 20 years, could continue to deliver energy for another 80 years.

PG&E has a 25-year contract for power from the Mojave park.

"The solar thermal project announced today is another major milestone in realizing our goal to supply 20 percent of our customers' energy needs with clean renewable energy," said Fong Wan, vice president of energy procurement at PG&E.

California has required that utilities derive at least 20 percent of their power from renewable sources by 2010.

In pursuit of that goal, yesterday PG&E signed a seperate 85 megawatt windpower contract with PPM Energy (see PG&E buying 85 MW of windpower from PPM).

The deal with Solel, along with a number of other recent contracts, would bring PG&E's renewable energy supply up to 18 percent, from 12 percent, of its total power offering.

In addition to the PPM wind agreement, PG&E has 7 megawatts of utility-scale solar projects with Cleantech America and GreenVolts (see GreenVolts lands agreement with PG&E), and a 25.5 megawatt contract with Western GeoPower for a new geothermal energy facility in California.