Ausra

Areva, the giant French nuclear company, has bought Ausra, a small manufacturer of solar thermal systems that can be used for electricity production or industrial steam.

“We are expanding our carbon-free portfolio,’’ said Anil Srivastava, a senior executive vice president at Areva. The company also builds wind turbines and biomass plants. “Because of our nuclear knowledge, we know how to design and build plants,’’ he said.

Ausra, based in Mountain View, Calif., makes curved mirrors that focus the sun’s heat on a black pipe running down the middle. Inside the pipe, a working fluid is heated and then used to make steam, which drives a conventional steam turbine to make electricity.

Depending on design details, the steam can be stored so that production can be scheduled at the time when the electricity would be most valuable, improving the economic viability of the project.

Ausra had hung out the “for sale” sign some months ago.

The company has a five megawatt demonstration plant near Bakersfield, Calif., and a factory in Las Vegas that makes the mirrors. In New South Wales, Australia, it has a solar array that feeds steam into an existing coal-fired power plant, reducing the need to burn coal during the day. Capital costs in that plant are small, and the investment is repaid by savings in coal, according to Ausra. It has also sold steam systems to industrial companies.

Ausra’s chairman and chief executive, Robert E. Fishman, said the company’s product was selling in California because of the state’s requirement that utilities get a large fraction of their power from renewable sources. But the goal, he said, was to reach “grid parity,” and Areva, with its manufacturing expertise, would help Ausra do that.

Ausra’s cost of production, in cents per kilowatt-hour, is “in the low- to mid-teens.’’ Nationally, the average cost of a kilowatt-hour is about 11 cents, but it is higher in some locations in peak periods.

In addition, Areva will offer buyers long-term assurance of technical support, the two men said.

The solar thermal industry, said Mr. Srivastava, is good at “making large sensational announcements” about new projects, but then “doing very little to build those power plants.’’ Areva wants to be the world’s largest solar thermal producer, he said, and has the engineering and commercial skills to push the projects along.

Ausra is privately held and the sale price was not disclosed.