US wind farms kill about 7,000 birds a year, according to a recent study. Other studies of individual wind farms suggest a higher toll on bats and birds, who crash into towers, blades, power lines and other installations. Estimates from a single wind farm in Altamont, California showed as many as 1,300 birds of prey killed each year – or about three a day.
Such direct threats to wildlife, and concerns for habitats, have increasingly pitted conservationists against the renewable energy industry. A handful of wind power projects in the US have been shelved because of wildlife concerns.
But new radar technology now in use at the Peñascal wind farm in Texas claims to have found a balance between competing environmental concerns – taking action against global warming and protecting wildlife – by protecting migrating birds at times of peak danger.
The 202MW farm, operated by the Spanish firm, Iberdrola Renewables, is the first in the world to use radar systems to enable it to shut down automatically if bad weather hits in peak migration times.
The installation, which opened late last month, uses radar systems originally developed for Nasa and the US Air Force to detect approaching birds from as far as four miles away, analyse weather conditions, and then determine in real time whether they are in danger of flying into the rotating blades.
If they are, the turbines are programmed to shut down, restarting once the birds are safely on their way, said Gary Andrews, the chairman of DeTect, Inc, the Florida company that developed the technology.
The system spots the birds and assesses their altitude, numbers and the visibility. “With all these pieces coming together properly … the turbines will shut down,” said Andrews.
Conservationists however are sceptical of such an easy fix. They argue that wind farms should still be sited away from migration routes in the first place, and that the technology does nothing to solve the problem of installations that disturb bird and animal habitats and nesting grounds.
The Peñascal wind farm is located on the Central Flyway, a main route for migratory birds in the Americas.
Millions of birds funnel through the narrow air corridor during the semiannual migration. A study in the autumn of 2007 found 4,000 birds an hour passing overhead.
In ordinary circumstances, the birds would be thousands of feet above the wind farm, passing the turbines without incident. But that can change dramatically in a sudden storm.
A sudden cold snap, like the legendary Texan “Blue Northern”, can prove fatal for migrating birds, bringing strong head winds and fog. The birds, which typically fly at night, become disoriented and exhausted, elevating the risk they will lose altitude and crash into 400ft wind towers along their route, wildlife experts say.
Conservationists are reserving judgment. “The wind energy industry makes bold claims, and they need to prove them,” said Andrew Kasner, director of bird conservation for Audubon Texas.
– from guardian. 1 May 2009.