Technicians install a blade on a horizontal axis wind turbine at the renovated National Wind Technology Center at Rocky Flats.
Photo by Warren Gretz courtesy of National Wind Technology Center at NREL (National Renewable Energy Laboratory).
As the price of electricity from the wind remains higher than that derived from fossil fuels, the National Renewable Energy Laboratory has begun a program to reduce the cost of wind to 2.5 cents per kilowatt-hour. They plan to reach this milestone -- which would allow wind to compete with no subsidies, by using larger turbines, higher towers and advanced electronics.
Already, some new wind machines are giants, with rotors roughly as long as the wings of a Boeing 747. By centering the rotors 110 to 200 feet above ground, newer models catch faster winds, and output per machine is approaching one megawatt.
Electronics will soon play a role in improving efficiency. In most existing wind machines, rotors must spin at a constant rate, because the rotation rate determines the number of hertz -- or cycles per second -- of the electricity. (In the United States, electricity on the grid oscillates 60 times per second -- 60 hertz.)
Even when the wind can spin the blades faster, they must continue rotating at the same stately pace, since faster rotation would generate the wrong hertz. That means generators can't extract the higher energy present in the faster wind. But some new models use an electronic power supply able to generate 60 hertz at various blade speeds, enabling them to harvest more wind.
Imperfect savior
Those giant spinning blades can also give birds a deadly whack. At least 40 golden eagles are killed by the 7,000 generators at the wind farm at Altamont Pass, Calif., each year, says Susan Hock of the National Renewable Energy Laboratory. She notes that the eagles like perching on the towers because "they make a great hunting place, there's mown grass down below [to alleviate fire danger], and the ground squirrels are easy to hunt."
One low-tech solution being adopted is tubular towers, which prevent the birds from getting a toehold. Other possible solutions include painting colors or patterns on the blades, and making noises that irritate birds.
Is wind totally benign? Not exactly. Big wind generators -- at least the older ones -- are noisy, particularly when many are grouped in a "wind farm." Noise has become an issue in Europe, where people live close to the turbines, but not in the United States, where turbines tend to be remote from population centers.
How many is too many?
The National Audubon Society has no position on bird deaths from wind generators since, according to press officer John Bianchi, the group's scientists felt they did not have "that big an impact on the total bird population in the United States."
Eagles, as well as other raptors and songbirds, are federally protected, and while the feds could shut down generators that kill too many of them, Hock observes that we sometimes decide to live with a certain level of bird deaths -- from automobiles, for example -- if the benefits seem to justify the loss.
Here's something that seems justified: car-size fuel cells that make electricity directly from gasoline.
With those studies remaining inconclusive, Hock says preventing bird deaths is "mostly a siting issue," since Altamont is a migratory route for raptors. She notes that other California wind farms are killing a few songbirds but not protected species. "Can you avoid putting them where there are a lot of endangered or threatened species?"
