A Bright New Perspective: Sunshine Could Power the U.S.

With growing concern over climate change, alternatives to coal and natural gas combustion have never looked better. Many fast-growing metropolises who happen to be heavy on electricity consumption, such as Las Vegas, Los Angeles and Phoenix are located conveniently in sunny areas and are becoming increasingly interested in solar thermal technology. In fact, the first plant to be built in decades started providing 64 megawatts of electricity to the neon lights of Vegas this summer.

With few clouds, the American Southwest sun pours more than eight kilowatt-hours* per square meter of its energy onto the landscape. Vast parabolic mirrors in the heart of California's Mojave Desert concentrate this solar energy to heat a specialized oil to around 750 degrees Fahrenheit (400 degrees Celsius). This hot oil then transfers its heat to water, vaporizing it. The resulting steam turns a turbine to produce electricity. In all, nine such mirror fields, known as concentrating solar power plants, can supply more than 350 megawatts of electricity yearly.

However, physicist David Mills, chief scientific officer and founder of Palo Alto, Calif.–based solar-thermal company Ausra, has much bigger plans than just powering the southwest. He says that by concentrating the sun's power, we could provide all of the electricity needs of the U.S., including a switch to electric cars feeding off the grid. "Within 18 months, with storage, we will not only reduce [the] cost of [solar-thermal] electricity but also satisfy the requirements for a modern society," Mills claims. "Supplying [electricity] 24 hours a day and effectively replacing the function of coal or gas."

The company is positive that it can do this at a cost of just 10 cents per kilowatt-hour, similar to the price of electricity from burning natural gas in California—especially if a cost was imposed for the emission of carbon dioxide, the leading greenhouse gas, which the state's Public Utilities Commission is considering doing.

Ausra will rely on a different kind of concentrating solar power plant to deliver this grand development. French physicist Augustin Fresnel showed in the 19th century that a large lens, like the parabolic troughs of the existing solar-thermal plants, can be broken down into smaller sections that deliver the same focus. Mills' design applies this by using a compact linear Fresnel reflector, which allows for greater ground coverage, lower weight and greater durability than precision-shaped parabolic mirrors. They’re not fragile like some other solar technologies.
"You can drop stones on it and they bounce off," Mills says. "We would be able to build these in Florida in the hurricane zone."

This Fresnel solar thermal plant eliminates the need for super hot oil by directly heating water to a lower temperature of roughly 535 degrees F (280 degrees C) at a higher pressure, about 50 bars, or 50 times atmospheric pressure. Then, it uses the resultant steam to turn the same low-temperature turbines as those employed in nuclear reactors.

The amount of electricity produced is simply a function of sunlight and the number of mirrors. "We're moving from 80- to 100-megawatt designs to 700 megawatts and above," says John O'Donnell, Ausra's executive vice president.

Mills and his colleagues presented their calculations in a paper presented recently at the Solar Energy Society World Congress in Beijing. They say that solar-thermal power plants could match the electricity needs of both California and Texas. And, by combining a system that would meet the needs of California and Texas, solar-thermal plants could supply 96 percent of the national electricity demand. "The entire energy use of 2006, the current technology including storage would use a patch of land 92 miles by 92 miles," O'Donnell says. "Ten percent of the [Bureau of Land Management] land in Nevada is enough."

Ausra is planning to announce several partnerships by the end of the year and has already acquired the land to build one such solar-thermal plant at an undisclosed location in southern California. If its storage system works and proves cost-effective, Ausra might just help usher in a solar revolution.

"We have the ability to transition to a zero-carbon electricity future without moving the electricity price around," O'Donnell says. "That hasn't been part of anybodys conventional wisdom."

Posted by Rebecca Sato

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http://www.dailygalaxy.com/my_weblog/2007/09/british-green-e.html

Related blog posts:

http://blogs.business2.com/greenwombat/2007/09/solar-nation--2.html,
http://www.treehugger.com/files/2006/11/can_solar_power.php,
http://climate.weather.com/blog/9_13402.html

Story Link:
http://www.sciam.com/article.cfm?chanId=sa013&articleId=1FC8E87E-E7F2-99DF-3253ADDFDBEC8

Comments

[John Sawyer]

The best way to achieve solar power for all, is for everyone who owns a home, and every business, to mount a solar power collector on its roof, and batteries inside the building for when the sun isn't shining. No need to rely on the grid most of the time, though it should still be there for people unable or not willing to install a solar collector. A decent collector still costs several thousand dollars, but that will come down, especially the more people who install them, and some states and utilities will help pay for the cost.

In other words, people need to start installing these, instead of waiting for some other solution to come along. We don't rely on a "hot water grid" for our hot water, do we? We have water heaters in our buildings, not at some distance.

Though the home solar power industry is growing quite fast, I'm still puzzled at the fact that one can drive up and down the streets of expensive neighborhoods, even ones populated by people who care about these things, and not see one solar collector. If you live in such a home, can you tell me why you haven't done this yet?