In a David vs. Goliath mismatch, flying insects can wreak havoc on the efficiency of wind power turbines, a new study shows.
Wind power is one of the fastest-growing alternative sources of electricity in industrialized nations, including the United States. However, power generation at even the most advanced wind farms can fluctuate mysteriously by as much as 25 percent.
European scientists point to an unlikely culprit: bugs.
Bees, butterflies, gnats, locusts, dragonflies.
Thousands of insects fly to their deaths against the big blades that span 150 feet and spin like a giant blender.
Rather than being pureed into oblivion, the bugs stick where they splat, much as they do against the windshield of a car.
Over time, researchers say, the dead insects form a ragged crust on the blades leading edges. Thats the angled edge that initially bites into the air and steers the air smoothly over the blade surface.
Even a millimeter or two of bug crust generates sufficient aerodynamic drag to ruin the turbines efficiency, they conclude in a study published in Thursdays issue of the journal Nature.
The stalling behavior of the blades depends on the degree of contamination on the leading edges, report Gustave P. Corten of the Energy Centre of the Netherlands and Herman F. Veldkamp of NEG Micon, a Danish turbine manufacturer.
The researchers tested their bug theories by measuring the power outputs of smooth, clean turbine blades versus blades whose leading edges had been artificially roughened to simulate bug buildup.
As wind speeds increased, the power disparity widened between the smooth and the roughened blades.
Roughened blades still performed acceptably in low wind because the angle of the air flow is different, they said.
Energy researchers who did not participate in the study said it confirms what they had observed at wind farms.
For now, operators must stop turbines and pressure-wash hundreds of blades. That only compounds the power losses the bugs already caused.
Engineers are designing bug-free turbines using nonstick surfaces and different blade angles, said David Simms of the National Wind Technology Center near Boulder, Colo.
The problem has always been trying to make the turbines inexpensive because we are competing with conventional sources of energy, Simms said. Coal and oil are really cheap.
In the United States, an additional 2,000 megawatts of wind power should be added this year, according to the American Wind Energy Association. One-third of the new capacity is being built in oil-rich Texas.
One wind farm typically generates 50 to 100 megawatts, about one-tenth of the output of a conventional generating plant. A megawatt is enough electricity to serve about 1,000 homes.
This years new farms should double the nations wind power output to 4,500 total megawatts, the association reports.
Wind power accounts for about 1 percent of the nations energy production, but its share is growing as wind power costs decline.
Worldwide, there are more than 35,000 wind turbines generating 12,000 megawatts per year, the AWEA reports.
Germany and other nations are building wind farms offshore to harness powerful sea breezes. Denmark plans to generate half of its power with wind turbines by 2040.
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