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Discovery of fast winds breathes life into the corpus of climate and energy solutions

Can we light up the world and fuel our vehicles without polluting the environment? The answer may be blowing in the wind.

It's not enough to set up hundreds of turbines at a blustery site to create a "wind farm" and hope that consistent gusts will generate electricity. It's necessary to know where fast winds blow and how best to harness them since the amount of power generated increases with wind speed and turbine blade diameter.

In the first study to clock winds at the hub height of newer turbines (262 feet versus 164 feet for older turbines), Stanford researchers found that 24 percent of U.S. wind monitoring sites experience gusts fast enough to generate power as cheaply as coal or natural gas plants. Co-authors Cristina L. Archer and Mark Z. Jacobson report their findings in the May 13 online issue of the Journal of Geophysical Research (Atmospheres).

Since the wind isn't always blowing, its reliability has been a barrier to its exploitation as an energy source. But wind's intermittence would no longer be a problem if wind farms were networked to reduce the effect of unproductive days at individual sites, the researchers say. Linking at least eight wind farms virtually eliminates the chance of a windless hour during the year.

"If we want to address global warming, urban air pollution, acid deposition, health and mortality problems, and the resulting public health costs associated with fossil fuel sources, we need to reduce substantially the burning of fossil fuels," says Jacobson, an associate professor of civil and environmental engineering. "Global warming, which is already occurring according to the short- and long-term climate record, cannot be reversed during our lifetimes unless large reductions in carbon emissions occur immediately. The large expansion of wind energy is the most practical method at this time of addressing this issue."

Finding that one-quarter of the nation is suitable for wind power production is extremely important, says Archer, who is Jacobson's graduate student. "It's like finding that 24 percent of the nation has a free, safe and pollution-free oil that is just waiting to be extracted for use. If wind power is used to generate hydrogen for fuel-cell vehicles, this country could reduce its dependence on foreign oil."


Power without pollution

While wind's potential appears enormous, a lot of fast wind had never been mapped. So its potential is even greater than previously realized. The researchers discovered fast winds in the United States along the southeastern and southern coasts. Offshore and nearshore, where there's less friction to slow winds, 37 percent of sites experienced speedy gusts.

Since more than half of the U.S. population resides along coasts, coastal wind farms could reduce transmission costs -- a concern when electricity is generated far from where it will be used. Many wind farms are located in the sparsely populated Great Plains, for example. North Dakota alone is theoretically capable of producing enough wind power to meet more than one-third of U.S. electricity demand, according to the American Wind Energy Association.

The direct cost per kilowatt-hour of power generated by winds of at least 14 miles per hour is 2.9 to 3.9 cents, according to a 2001 article in Science by Jacobson and Gilbert Masters, an emeritus professor (teaching) of civil and environmental engineering. That cost competes with that of power produced at new plants utilizing coal (3.5 to 4 cents) or natural gas (3.3 to 3.6 cents). Mighty winds might breathe clean, renewable power into the grid, which in 1999 relied on coal (51 percent) and natural gas (15 percent) to generate 66 percent of U.S. electric power.

Burning of coal and natural gas emits carbon dioxide, methane, sulfur dioxide, oxides of nitrogen, carbon monoxide, ammonia, soot and other pollutants. These emissions cause global climate change, smog, acid rain and haze. In addition, coal mining harms the environment through stripping of land, pollution of water and emission of mercury.

Coal also contributes to cardiovascular and respiratory diseases, notably black lung disease. Every year the Federal Black Lung Program provides almost $460 million in monetary and medical benefits to former coal workers and their survivors, according to the Department of Labor.

In contrast, wind causes no pollution past the turbine manufacturing and scrapping process. Yet wind produced only 0.12 percent of U.S. electric power in 1999, according to the Energy Information Administration, which provides official energy statistics from the U.S. government.

Wind could reliably provide at bare minimum 30 percent of the country's power, Jacobson says, with backup from a mixture of sources including hydroelectric power. If 30 percent of America's electric power needs were met by wind, Jacobson says the United States would be able to get rid of 60 percent of its coal dependence.

"Previously, we calculated that if you wanted to satisfy the Kyoto protocol, you could replace 60 percent of the coal-fired power plants in the United States with about 225,000 1.5-megawatt turbines over an area of about 194 square kilometers," says Jacobson. "That's using 1999 statistics. Today, 3.2- to 3.6-megawatt turbines are in use and 4.6 megawatt turbines are being tested. With turbines of these sizes, only one-half to one-third the number of turbines is needed to produce the same energy."

Wind currently provides 20 percent of electric power in Denmark and almost 5 percent in Germany. In the United States, it generates as much electricity as used annually by about a million average American households.

With the restructuring of the U.S. utility industry, consumers may have the option to pick clean, renewable energy sources. Several federal restructuring bills, as well as laws passed in at least 12 states, require that power producers generate part of their electricity from renewable sources.

While wind farms supply clean energy, some environmentalists argue that turbine blades kill birds. That's less of a problem, Jacobson says, with today's larger, slower-turning blades, which birds have an easier time circumnavigating compared with the smaller, faster-turning blades of yesterday's systems.

Additionally, some criticize the aesthetics of wind turbines. "I'm not sure why it is OK to look at a power plant facility, a skyscraper or a house and not a wind turbine," Jacobson says. "Once it is understood that the turbine is replacing a power plant and cleaning the air, objections should decrease. Turbines far enough offshore, in particular, should not be objectionable."


Mapping the wind

Through the web, Archer and Jacobson obtained hourly surface wind data from the National Climatic Data Center and wind profile data from the Forecast System Laboratory. Collecting data throughout the United States for the year 2000, they aimed to map fast winds at the hub height of a new wind turbine, 262 feet.

Easier said than done.

"The problem we were facing was that we found thousands of stations reporting winds at the surface [33 feet above ground], but very few had data at [262 feet]," Archer explains. "We needed a robust method to derive [262-feet] wind speed from [33-feet] wind speed."

They took data from 1,327 surface stations and 87 soundings -- profiles that give wind speeds at different heights. In a sounding, a wind speed along a plotted curve can be interpolated and a wind speed outside the curve can be extrapolated. Using a "least square error approach" to minimize the error between observed and extrapolated values, they came up with the most accurate measurements to date of wind speeds at the hub height of modern turbines.

Whither, wind power?

Ultimately, Jacobson envisions, wind may help power an emerging "hydrogen economy." Wind would generate electricity that would be fed into the power grid. That electricity would be transmitted to hydrogen-generation plants to split water into oxygen and hydrogen via electrolysis. The generated hydrogen could power motor vehicles at hydrogen filling stations or in hydrogen batteries.

"If you use wind to generate hydrogen, then wind, in the limit, could theoretically replace all oil, coal and natural gas combustion, solving many problems," he says. "Because hydrogen stores the energy generated by wind, wind intermittency is no longer a barrier to its widespread implementation."

Since coal and natural gas are subsidized to a greater extent than wind, they do not pay their true costs to society, Jacobson says. "These fuels are still competitive with wind in price and have no incentive to go out of business. What is needed are strong carbon, sulfur and nitrogen taxes on these industries that reflect their true cost to the United States and the general public. Today, grandfathered, old coal power plants do not even need to meet Clean-Air Act Amendment emission requirements. Once taxes that reflect the real cost of fossil energy are implemented, the economic benefit of wind will become apparent."

Jacobson advocates a large, Apollo-like wind-energy program to jumpstart large-scale use. An effort of that magnitude is warranted to lessen global climate change, he says. "You really need to do something right away, and there is a way to do it with wind if you put your mind to it, because there are plenty of wind resources in the United States. But it requires a huge infrastructure change and mindset change."

In addition to being clean and plentiful, wind also may bolster national security, since it's a distributed energy source. "It's not like a nuclear or coal power plant where you can target a single location," Jacobson says. "Turbines are distributed. You'd essentially have to destroy individual turbines separately."


By Dawn Levy

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