In Phoenix on Feb. 21, the Arizona Public Service unit of Pinnacle West announced plans for a large plant to be built by a Spanish company, Abengoa, and finished in 2011. That one will store heat so that it can continue to produce power for up to six hours after sunset.
Donald E. Brandt, the chief executive of Pinnacle West, said the decision to build the new solar plant was as important as his company’s decision in 1973 to build the Palo Verde nuclear plant, the largest and most modern in the United States.
“The key is, the solar technology has advanced,” Mr. Brandt said. At 280 megawatts, “it’s a critical size; it’s a real power plant; it’s meaningful; it’s beyond the demonstration stage.”
Companies that build the plants have been working on improving the technology, raising efficiency and lowering costs. A battle among competing approaches is expected over the next few years.
The plant here, Nevada Solar One, built by a Spanish company, Acciona, is of a proven design. It uses a mirror in the shape of a parabola to focus light onto a black pipe with a heat-transfer fluid inside. The fluid is used to boil water into steam, which turns a generator that can produce 64 megawatts.
That is small compared with a plant running on coal or natural gas, but far bigger than a typical installation involving solar photovoltaic panels, the type of solar power most people are familiar with. That technology, while good for some uses, is far more expensive than solar thermal power.
Suppliers of thermal systems are gearing up for a boom. In Las Vegas, a company called Ausra is building a factory to make mirrors for one type of solar plant; it will double the world’s manufacturing capacity. A German company, Schott, is building a factory in Albuquerque that will make heat-collecting tubes.
The newest solar-thermal technology involves building a “power tower,” a tall structure flanked by thousands of mirrors, each of which pivots to focus light on the tower, heating fluid. That design can work even in places with weaker sunlight than a desert.
One of the big advantages of these plants is that they can be built with the capacity to store heat in what amounts to a giant Thermos. Experts say that will smooth production and make it easier to integrate the plants into the electrical grid.
If large numbers of plants are built, they will eventually pose some problems, even in the desert. They could take up immense amounts of land and damage the environment. Already, building a plant in California requires hiring a licensed tortoise wrangler to capture and relocate endangered desert tortoises.
“The one thing that’s eventually going to raise its head is desert biodiversity, and the land area itself,” said Terrence J. Collins, an environmental expert and professor at Carnegie Mellon University.
Building the plants in deserts poses another obvious problem: deserts are not exactly teeming with power lines. “Whatever you do, you’ve got to have the wiring,” Mr. Collins said.
Despite the difficulties, solar thermal plants have an other-worldly beauty as they run.
At Nevada Solar One the other day, Mr. Boucher, 30, ran the computerized control room. Dressed in a T-shirt, sneakers and a Boston Red Sox cap worn backwards, he looked a bit like a teenage gamer as he used a computer mouse to manipulate the plant.
He was trying to produce as much electricity as possible while saving heat to tide the plant over as clouds cast episodic shadows on the solar array. “I’ve been fighting it all day,” he said.
Outside, row after row of U-shaped mirrors, covering nearly a square mile, stretched across the desert. In the center of each U, where the force of the sun was magnified 70 times, ran a pipe painted black, and inside it flowed oil that warmed to hundreds of degrees as it collected the heat needed to run a generator.
The buzz in the control room, as Mr. Boucher worked, contrasted with the sanguine scene beyond the windows. Imperceptibly, in the dusty wind of the high desert, 182,000 mirrors moved from east to west, tracking the sun across the sky.