Solar-thermal power has never seemed as technologically smart as photovoltaic technology. After all, a Neanderthal man could warm himself in the sun, but it took Einstein to explain the photoelectric effect.
But these days the idea of using sunlight to heat fluids to generate electricity is suddenly looking like a bright idea. At least 10 solar-thermal power plants are being developed for installation in the United States, and another 17 are under construction or being planned in Algeria, China, Egypt, Israel, Mexico, Morocco, South Africa, and Spain. With a typical plant generating somewhere between 50 and 500 megawatts, that's a lot of clean power due to come online. (New photovoltaic installations worldwide totaled a record 2826 MW in 2007, according to Solarbuzz.)
There are lots of ways to build a solar-thermal system, parabolic troughs or dishes being the most familiar. But a former Australian academic, David Mills, founder of the solar-thermal firm Ausra, in Palo Alto, Calif., thinks he has a better idea, and at least one major utility--Pacific Gas & Electric, in San Francisco--agrees. In November, the utility signed an agreement to purchase power generated by a 2.6-square-kilometer 177-MW power plant Ausra is building in the Nevada desert. Ausra says it has many more such deals in the works.
Mills's design, called the Compact Linear Fresnel Reflector, uses much less land than others. The mirrors appear to be solid but are actually made up of many smaller, movable reflectors, each with a slight curve. The system uses nearly flat mirrors at ground level that focus the sun's light onto water-filled steel tubes. When the water boils, it directly drives a steam turbine to generate electricity. Typical solar-thermal systems use heat transfer; water- or oil-filled tubes pass the heat to another system, which then boils water to drive steam turbines.ï»'
”I have a favorable opinion of [Ausra's] technology, largely because of the relative simplicity of manufacturing flat mirrors compared with parabolic mirrors. Also, because the mirrors are closer to the ground, they are less subject to wind loads,” says Michael Locascio, a senior analyst with Lux Research, in New York City.
Last April Ausra powered up the production line at a 12 000-square-meter manufacturing plant in Nevada. It's the first facility in the United States dedicated to producing the components of solar-thermal systems, including reflectors, towers, and specially insulated steel tubes. The new factory can build enough equipment to fill more than 10 km2 with solar-thermal collectors annually, enough to produce 700 MW of power or to power 50 000 homes. Eventually, Mills expects Ausra to sell equipment to others; for now, Ausra will consume the output.
Ausra sounds like a young company on the fast track, and in a way it is. It got its first round of venture capital financing last year--US $43 million. But in another way, Ausra's been slowly building for decades. Mills has been working with solar energy since the 1970s. Back then he was a principal research fellow at the University of Sydney, doing work in optics. There he started a research program to develop advanced coatings for evacuated-tube solar collectors, cleverly constructed glass tubes that let solar energy in but don't let heat out. Today his tubes are widely used in water heaters in China.
In 2006, John O'Donnell, a serial technology entrepreneur, contacted Mills. At first Mills told him, basically, to get lost. But O'Donnell was persistent, and in October of that year, he convinced Mills to come to California for a meeting with venture capitalists. Just three months later, Mills left the house in Sydney where he'd lived for more than 20 years and moved to Palo Alto; his wife and children followed a month later.
These days he heads up R&D for Ausra; until recently he ran the company's engineering efforts as well. ”I'm 61,” he says. ”It's a bit late in life to do a start-up, but when you work at something all your life, you do hope something comes of it and that you can influence change.”