May 7--The Altamont windmills spin fast this time of year. So, too, spin the minds of scientists charged with weighing the pros and cons of wind energy.

A congressionally mandated study released last week says that as more states attempt to harness the wind, government should control more closely where windmills are allowed to sprout -- perhaps saving birds and bats from being chopped up by blades as bi as airplane wings. Wind energy has quadrupled since 2000, the study by the National Academy of Sciences says. Turbines can be found in 36 states; the larger windmills can produce enough energy in eight hours to power a household for one year. But there are consequences. The Altamont's 5,400 turbines kill more than 1,000 birds a year, according to some estimates, including golden eagles and hawks.

The hills of the Bay Area are home to the largest concentration of golden eagles in the world. There is no easy solution, the scientists said. The study, said to be the largest of its kind to date, presents no conclusion regarding what's more important: clean energy or wildlife. But it does allow regulators -- and the public -- to decide. Wind energy accounts for about 1 percent of the nation's power supply; that number could increase to anywhere from 2 percent to 7 percent by 2020, the scientists found. Theoretically, this means less reliance on power plants that emit greenhouse gases and contribute to global warming.

The scientists predict wind power will offset 4.5 percent of the carbon dioxide that those power plants otherwise would emit. "It's 100 percent clean, free and inexhaustible," said Randall Swisher, director of the American Wind Energy Association. He was not involved in the study. Rick Koebbe, president of Tracy-based PowerWorks, says the Altamont wind farm would save 98 lives over 20 years, and prevent 3,197 asthma attacks and 17,200 days of lost work productivity. And cleaner air is good for birds, too, said Koebbe, whose compa y is one of about a dozen operating Altamont windmills. In an experimental project, these companies turned their turbines off for two months during the past two years to see how birds would react.

They still smacked into the windmills, Koebbe said. "The environmental impact (of bird deaths) is far outweighed by the health benefits of this renewable resource," he said. The study released last week says there is no evidence that wind farms measurably harm bird populations nationwide, with one possible exception: the Altamont. That's because the birds killed here are raptors, predators with an important role in the ecos stem. In the 1980s, when the first Altamont windmills were built, there was little thought about birds. Even today, there are virtually no federal requirements on where wind farms should exist, the study says, although there are laws protecting eagles and oth r migratory birds.

"We don't expect the impacts ever to be zero," said Julia Levin, state policy director for California Audubon. "With smart, informed siting decisions, they can be much lower. ... I think everyone wants to avoid having another Altamont." A lawsuit over the bird deaths was settled in recent months; windmill operators must work to replace the smaller, older turbines with larger, more-efficient ones, though Koebbe said that effort is hampered by a number of factors, including a worldwide s ortage of turbines. Would tighter regulations have made a difference when the first Altamont windmills were built? It's not fair to guess, said Paul Risser, a University of Oklahoma researcher and director of the Smithsonian's National Museum of Natural History, who headed the recent study.

"But our guidelines would have asked whether siting a facility in an area where there are lots of raptors would in fact be a good decision," he said. A number of factors make it hard to determine if wind power is worth it. Studies are lacking on wind farm comparisons and turbine designs, the scientists say; and the policies of local and state governments vary across the country. Last week's study is important, Risser and others said. Areas in the Great Plains that are likely to see wind energy development in the coming years are also crossed by the flight paths of migratory birds. Contact reporter Alex Breitler at (209) 546-8295 or abreitler@recordnet.com.

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