Friday, February 27, 2004

What's goin on with the Solar Tower of Power?

most recent entry I found is 2 years old ....

Sun in the Forecast

The first commercial-scale solar power plants are up and
running. The price isn't competitive yet, but that goal is
getting closer all the time. A progress report
By Erika Check

April 8 issue - High in the Mojave Desert, 130
miles northeast of Los Angeles, lies a vast field
of mirrors. Crisscrossing rows of glass and
metal, glinting in the sunlight, cover a full
square mile of dirt. It's not some bizarre
fun-house experiment or a grotesque exhibit of
Hollywood vanity. It's a fully operational array
of power plants churning out an average of 180
megawatts of electricity, and offering a glimpse
of a world in which the grid's electricity comes
from the sun.

MOST PEOPLE THINK of solar power as a flat panel on every rooftop. But photovoltaic panels, which convert sunlight to electricity, have limitations. They work fine when the sun is strong, but when the clouds roll in you’d better have batteries to run the TV and dishwasher. And even on the sunniest days the panels aren’t very well suited for cities, where roof space is limited. For decades, engineers have been working on ways to catch the sun over a broad area, concentrating it and using it to produce electricity on the same scale as centralized coal, hydro or nuclear power plants—hundreds of megawatts at a time. Several pilot plants have been operating in California, some for decades, but so far they haven’t had enough volume to force costs down to competitive levels.
That may soon change. Spain is drawing up plans for a pioneering 15-megawatt plant. South Africa, Italy, Australia and India are expected to follow with much larger plants capable of generating more than 100 megawatts each. If at least some of these projects are completed, costs could come down from the current 15 cents a kilowatt-hour for the Mojave plant to 8 cents per kwh in the next eight to 10 years, says Bill Gould, project manager for energy systems at Nexant, a renewable-energy firm. That would go a long way toward closing the gap with gas and oil, which now cost as little as 4 cents per kwh. “The first plants will be expensive,” says Craig Tyner of Sandia National Laboratories. “But as we build them the costs will come down.
The Mojave plant, owned by Kramer Junction Company (KJC), is one of the world’s first commercial solar power plants, with five Solar Electric Generating Systems (SEGS) supplying electricity to southern California. The basic component of a SEGS plant is a row of parabolic mirrors that reflect sunlight onto a pipe filled with oil. The oil heats up and is used to produce steam, which turns an electrical turbine. Assemble a few dozen rows of these trough-mirrors, and you’ve got capacity to generate 30 megawatts of power, enough for half a small town. The 180 megawatts from the five SEGS plants came in handy during California’s energy crisis last summer, when oil and gas prices shot up to 50 cents per kwh. “Suddenly, we were quite the deal,” says Scott Frier, KJC’s general manager. The problem with trough technology, though, is that the oil loses its heat too quickly. When the sun goes down, so does the power. SEGS require supplementary generators that run on natural gas at night and when it gets cloudy.
Within the next two years an international consortium, including the Spanish company Ghersa and Saint-Gobain of France, will break ground on a new plant called Solar Tres. Its design uses molten salt instead of oil. Since salt holds more heat longer than oil, it can drive turbines through the night. The technology has been demonstrated in a 10-megawatt pilot plant in the Mojave Desert. Concentric rings of mirrors direct sunlight up to a tank of molten salt. When the stuff is hot enough, some goes straight to a generator to produce steam, while the rest is stored for use at night. The 15-megawatt Solar Tres plant would be the first long-term commercial power production project that uses the tower design. Since the electricity is expected to be costly—close to 20 cents per kwh—the Spanish government plans to subsidize the plant.
The next big thing—dish systems—is already in the works. The building block of such a plant is a parabolic mirror, shaped like a satellite dish, that reflects sunlight onto a small generator suspended in front. The heat drives a turbine. Demonstration projects for dish systems are slated to go up later this year in both Arizona and South Africa. Theoretically a dish configuration would produce more energy per acre than other solar concentrating plants—that is, if engineers could figure out a good way of linking many dishes together.
Although the United States still sponsors most solar research, the biggest potential market is in dry, equatorial climates. Italy is spending .120 million to study how best to mine the Mediterranean sun. The World Bank has putting up $50 million for hybrid plants that use solar trough technology and natural gas in Egypt, India, Mexico and Morocco. What would really give solar plants a kick in the pants is a rise in oil and gas prices and a shortage of fossil fuels. Should that happen, it’s a safe bet the sun will still be shining.

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