Monday, March 23, 2009

Researchers think they are close to solving a problem that has slowed progress in meeting America’s future electricity needs - The giant wind turbines that constitute one of the most promising alternative energy technologies also cause bats to explode.

The problem is troubling to nature lovers, who have complained bitterly and delayed projects. The small, airborne creatures help maintain an ecological balance and make neighborhoods more livable by eating large numbers of insects.

But when the creatures fly too close to the football-field-sized windmills that are springing up in wind farms from California to Massachusetts, they enter an area of reduced air pressure that causes their lungs to explode - a phenomenon known as barotrauma.

Now a solution is in sight. Researchers are testing a technique that they hope will prevent millions of bat deaths a year. They intend to start turning off the turbines when wind speeds are low and, coincidently, when bats are most likely to be nearby.

The method, if successful, would give a major boost to the wind industry and allow President Obama to get closer to the renewable energy future he wants.

“We are all really excited about this,” said Laurie Jodziewicz of the American Wind Energy Association. “The industry takes this issue very seriously.”

Wind turbines have long been known to mangle birds that collide with their massive rotor blades, but a bigger problem is the turbines´ devastating effect on bats.

Bats get caught in a vortex of low pressure created by the turbine blades, which can spin at more than 125 mph at the tip. The sudden pressure change causes internal hemorrhaging in the bats similar to the human affliction known as the bends.

“You can´t see very much on the outside,” said Tom Kunz, a bat researcher at Boston University describing the carcasses. But once you cut them open, you can see “hemorrhages on the lungs. They simply burst open.”

This is especially worrisome, researchers said, because bats have slow reproductive rates, so even small numbers of fatalities can cause lasting impacts on the bat population.

“Bats take a very important role in limiting insect populations, including pests,” Mr. Kunz said. “Once you remove a top predator, it creates a cascade effect on the rest of the organisms.”

A soon-to-be-released study conducted last year at two wind facilities owned by Iberdrola Renewables in Pennsylvania and West Virginia finds that shutting down the turbines during low wind periods can reduce fatalities by more than 90 percent.

Ed Arnett, the study´s coordinator, said the deaths occur almost exclusively when turbines are operating at night at low wind speeds. That is when bats are active and feeding because the wind is light enough for insects to fly.

One theory is that the bats think the turbines are large trees and inspect them as potential roosting places. Researchers also think insects are attracted to the white towers at night and may draw bats to the turbines as a feeding ground.

Environmentalists and industrial officials say there is a cost to cutting off the turbines at night. Andy Linehan, a bat specialist at Iberdrola Renewables, said that shutting down the turbines during last year´s experiment resulted in a 2 percent reduction in electricity generation.

Ms. Jodziewicz said, “Any kilowatts created are money in the pocket.

“Anything that reduces kilowatt hours from our projects is a concern. It is something that affects the bottom line of these companies.”

Industry officials said more testing is needed before any industrywide policy is introduced. Ms. Jodziewicz said she is optimistic about using Mr. Arnett´s technique to keep bat explosions to a minimum.

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