New York Times

Thousands of acres of once fertile farmland here in the San Joaquin Valley have been removed from agricultural production, largely because it is contaminated by salt buildup from years of irrigation.

But large swaths of those dry fields could have a valuable new use in their future — making electricity.

Early last year, Elon Musk, the chief executive of Tesla Motors, strode into a giant hangar outside Los Angeles, in fitted jeans, leather boots and a designer jacket. With electronic dance music blaring, he whipped a black cover off a shiny silver car: a prototype of the Model S, an all-electric sedan.

J. R. Ewing returned to the small screen on Tuesday, and the boys down at the Cattlemen’s Club just might need a double bourbon when they hear what he has to say.

Larry Hagman, the actor who played the scheming Texas oilman on the long-running (1978-1991) television show “Dallas,” is reprising his role as J. R. in an advertising campaign to promote solar energy and SolarWorld, a German photovoltaic module maker.

BMW lifted the veil this week on its planned battery-powered car, in an indication that it is serious about building a new class of vehicle and delivering substantial numbers to showrooms by 2013.

BMW, the German carmaker, created Project i in late 2007 with the goal of building a car for urban areas where more than half the world’s people live. But, as with many corporate green projects, it was sometimes hard to tell whether the effort was sincere or just a way to generate sustainability credentials.

Nissan’s chief executive, Carlos Ghosn, said Tuesday that the company had already received 19,000 orders in the United States and Japan for the electric car that it would start selling at year-end.

More than six months before the car, the Nissan Leaf, arrives at dealerships, the preorders mean that the car is sold out for this year and that the company might stop taking reservations, Mr. Ghosn said during a visit to the Detroit Economic Club.

Mahindra & Mahindra, one of India’s largest automakers, said Wednesday that it would acquire a controlling stake in Reva, an electric car pioneer based in Bangalore that has been looking for deep-pocket partners to invest in its technology.

Mahindra, a conglomerate based in Mumbai that makes tractors, sport utility vehicles and trucks, said it would buy 55.2 percent of Reva by purchasing shares from the founders for an undisclosed price and by investing 450 million rupees, or $10 million, in cash in the company.

For years, many of China’s best and brightest left for the United States, where high-tech industry was more cutting-edge. But Mark R. Pinto is moving in the opposite direction.

Mr. Pinto is the first chief technology officer of a major American tech company to move to China. The company, Applied Materials, is one of Silicon Valley’s most prominent firms. It supplied equipment used to perfect the first computer chips. Today, it is the world’s biggest supplier of the equipment used to make semiconductors, solar panels and flat-panel displays.

Two years ago, this gritty mining city hosted a brief 21st-century gold rush. Long famous for coal, Puertollano discovered another energy source it had overlooked: the relentless, scorching sun.

Armed with generous incentives from the Spanish government to jump-start a national solar energy industry, the city set out to replace its failing coal economy by attracting solar companies, with a campaign slogan: “The Sun Moves Us.”

Gherardo Corsini, director of electric vehicle implementation at General Motors’ Opel/Vauxhall unit, made his way Sunday to Geneva from Germany more quietly than most. He was at the wheel of a prototype of the Opel Ampera.

“Getting lots of curious looks at the rest area,” one of Mr. Corsini’s passengers, Dietmar Thate, manager of social media for Opel, tweeted after the car made a short stop Sunday.

It was primarily a symbolic gesture. Way back in 1979, in the midst of an energy crisis, Jimmy Carter had solar panels installed on the roof of the White House. They were used to heat water for some White House staffers.

“A generation from now,” said Mr. Carter, “this solar heater can either be a curiosity, a museum piece, an example of a road not taken, or it can be a small part of one of the greatest and most exciting adventures ever undertaken by the American people, harnessing the power of the sun to enrich our lives as we move away from our crippling dependence on foreign oil.”