Owned by Juno Beach, Fla.-based FPL Energy, a sister company to Florida Power & Light Co., they are part of the national effort to develop diverse --- and more environmentally friendly --- sources of energy.

The problem is, they're killing thousands of bats a year.

"I can appreciate that we need other energy sources," said Jane Burch, who lives in neighboring Grant County, W.Va., where a large wind farm has been proposed. "But I don't like the look of them, and I don't want them behind my property, and I don't like what they do with the bat kills."

The first wind turbines to generate electricity were erected about 25 years ago in California. But wind power capacity more than doubled from 2000 to 2004, and now turbines are found in 31 states.

Though wind still generates less than 1 percent of the nation's electricity, the Department of Energy has set a goal of raising that to at least 5 percent by 2020. To reach that goal, the American Wind Energy Association estimates it will require an increase from about 16,000 turbines nationwide now to more than 78,000 turbines then.

About 600 of those turbines are planned for West Virginia and Pennsylvania. If they are built, more than 50,000 bats a year may be killed in those two states alone, said Merlin D. Tuttle, founder and president of Austin, Texas-based Bat Conservation International Inc.

He said there were no good estimates of how many bats would be killed nationwide if the association's projection of 78,000 turbines was reached, but he estimated it would be far higher than 50,000.

"They can't sustain that kind of kill rate," Tuttle said, noting that bats are among the slowest-reproducing mammals --- generally one pup each year, although some species have two to four.

"Bats are just as important by night as birds are by day," he said. Indeed, bats play an important ecological role by eating mosquitoes and such crop-destroying insects as moths, locusts and grasshoppers.

Contrary to popular belief, bats have quite good vision. That vision is enhanced by a radar-like system known as "echolocation" that helps them "see" in the dark and enables them to zero in on insects as small as a gnat.

A study conducted at FPL's Mountaineer Wind Energy Center here this year indicated that its 44 turbines may have caused between 1,300 and 2,000 bat deaths in a six-week period. That study was led by Edward B. Arnett, a scientist with Bat Conservation International, and financed largely by the American Wind Energy Association and its 700 member companies.

During the study, one of the turbines at Mountaineer was out of service. It was the only turbine where no bat fatalities were recorded during the entire period.

That led bat enthusiasts to conclude bats are not colliding with stationary blades, they're being hit by moving blades, said Dan Boone, a wildlife biologist from Bowie, Md., who has joined the fight against new windmill farms on forested mountaintops.

Experts don't know why the mortality rate seems to be so much higher at wind facilities in the Appalachian Mountains than it is elsewhere in the country.

A Government Accountability Office report in September showed that at wind farms outside the Appalachians, fewer than four bats were killed each year per turbine. But Arnett said the GAO report summarized studies that may have focused mainly on birds and underestimated bat kills.

It's also unclear precisely why bats are killed by windmills. Among the theories are that the windmills are located in the bats' migratory path; that bats may be attracted by the turbines' humming sound, their flashing lights to warn aircraft, or their tall masts suitable for roosting, or that the short range of the bats' echolocation system does not give them enough time to avoid the spinning blades.

The recent Mountaineer study has led to an impasse between bat conservationists and the wind power industry over what to do next.

Conservationists have called for further studies that would disengage some turbines on nights when the wind speed is low and bats and their prey are more likely to fly.

The wind power industry has rejected that suggestion. It has proposed studies of deterrent measures such as acoustics to discourage bats from approaching the turbines.

"We don't think it makes a whole lot of sense to be focusing on a solution that potentially could reduce the amount of power that is generated and potentially put stress on the machines," said Steve Stengel, an FPL Energy spokesman.

"We think there needs to be a great deal of effort put into finding ways for bats and wind turbines to coexist," he said.

The wind power industry echoes the views of FPL Energy, according to Tom Gray, deputy executive director of the American Wind Energy Association.

Because wind power companies have been trying to produce energy more cheaply, any proposal that would reduce generating capacity and drive up costs would give the industry "heartburn," Gray said.

Acoustical deterrent efforts are in the design stage and may be tested in the laboratory by early next year, Arnett said. If preliminary investigations show promise, field tests might take place next year. FPL Energy has offered to allow some of its facilities to be used for such tests.

But Arnett and Boone noted that acoustic efforts to rid houses of bats rarely work and said they did not believe sound deterrents would be effective in shielding turbines.