The Energy Challenge - Turning Glare Into Watts

March 6, 2008
By MATTHEW L. WALD

BOULDER CITY, Nev. — At first, as he adjusted pumps and checked
temperatures, Aaron Boucher looked like any technician in the control
room of an electrical plant. Then he rushed to the window and scanned
the sky, to check his fuel supply.

Mr. Boucher was battling clouds, timing the operations of his power
plant to get the most out of patchy sunshine. It is a skill that may
soon be in greater demand, for the world appears to be on the verge of
a boom in a little-known but promising type of solar power.

It is not the kind that features shiny panels bolted to the roofs of
houses. This type involves covering acres of desert with mirrors that
focus intense sunlight on a fluid, heating it enough to make steam. The
steam turns a turbine and generates electricity.

The technology is not new, but it is suddenly in high demand. As prices
rise for fossil fuels and worries grow about their contribution to
global warming, solar thermal plants are being viewed as a renewable
power source with huge potential.

After a decade of no activity, two prototype solar thermal plants were
recently opened in the United States, with a capacity that could power
several big hotels, neon included, on the Las Vegas Strip, about 20
miles north of here. Another 10 power plants are in advanced planning
in California, Arizona and Nevada.

On sunny afternoons, those 10 plants would produce as much electricity
as three nuclear reactors, but they can be built in as little as two
years, compared with a decade or longer for a nuclear plant. Some of
the new plants will feature systems that allow them to store heat and
generate electricity for hours after sunset.

Aside from the ones in the United States, eight plants are under
construction in Spain, Algeria and Morocco. Another nine projects are
in various stages of planning in those countries as well as Israel,
Mexico, China, South Africa and Egypt, according to a count kept by
Frederick H. Morse, formerly in charge of solar energy at the Energy
Department and now a consultant.

Mr. Morse and others say that solar thermal plants could meet most of
the galloping growth in power demand in Phoenix, Las Vegas and the rest
of the southwestern United States. In fact, experts say enough sunshine
hits the deserts of the Southwest that such plants could theoretically
power the entire United States. But that is a far-off dream, since it
would require big new transmission cables.

The workability of solar thermal power was established in the 1980s,
when developers in California built a series of plants in the Mojave
Desert, eventually reaching 354 megawatts of capacity. A megawatt is
enough electricity to run 1,000 room air-conditioners at once.

The California plants grew more sophisticated and costs shrank as the
project progressed. But then the price of a competing fuel, natural
gas, collapsed in the 1990s and building new solar plants became
uneconomic.

Today, natural gas prices are much higher, and political opposition is
rising to construction of new coal-burning power plants. Many states,
including California, are imposing mandates for renewable energy. All
of that is reviving interest in solar thermal plants.

The power they produce is still relatively expensive. Industry experts
say the plant here produces power at a cost per kilowatt- hour of 15 to
20 cents. With a little more experience and some economies of scale,
that could fall to about 10 cents, according to a recent report by
Emerging Energy Research, a consulting firm in Cambridge, Mass. Newly
built coal-fired plants are expected to produce power at about 7 cents
per kilowatt-hour or more if carbon is taxed.

The solar plants receive a federal tax subsidy, like other types of
renewable energy, which makes the economics work for builders but also
feeds skepticism about the technology’s long-term potential. “Unless
there’s a subsidy involved, it doesn’t seem like a very attractive
technology,” said Revis James, a renewables expert at the Electric
Power Research Institute, a utility industry consortium.

Still, solar plants do tend to produce peak power during the hottest
part of the day, when demand is highest and electricity is costly, so
at certain times they are already competitive with plants using natural
gas. And they have an advantage over the other widely available form of
renewable power, wind turbines: they are more predictable.

With California utilities struggling to meet a state quota of 20
percent renewable power by 2010, the state has grown interested in
solar plants. Pacific Gas and Electric has committed to building
several plants and is expected to make announcements about new solar
plants soon.

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.