WASHINGTON -- While the basic principle may be the same, today's windmills can hardly be compared to models built in the 1980s when the first wind farms were developed and soon ran into problems.
The turbines today are much larger, taller, lighter and more durable. Complex computer technology and improved aerodynamic design also has increased efficiency.
Still, much remains to be learned. The challenge is to design turbines that can tame fluctuations of the wind to make power more reliable and constant.
"There's got to be a better windmill ..., more efficient technology, lower costs and more reliability," says Brian Smith, an engineer at the government's National Wind Technology Center in Golden, Colo., trying to develop the next generation of turbines.
It's not that windmills are unreliable, says Smith. When the wind blows, they perform 98 percent of the time. The wind is intermittent, however, and on average today's windmill produces only about one-third the electricity that it is capable of generating at peak wind conditions.
The principle of a wind turbine has changed little. It's still a rotor, a gearbox and generator and control systems.
But today's turbines are cheaper, easier to install and work more efficiently. They have cut the cost of generating electricity by wind from 38 cents a kilowatt-hour 20 years ago to 3 to 5 cents a kilowatt-hour today.
The new designs address some past environmental concerns. Turbines are now sleeker, more tubular, so that birds cannot perch on them. They are larger but also quieter.
"The machines built in the early 1980s were almost on the scale of a bicycle" compared to today's machines, says Benjamin Bell, vice president for commercial engineering at Enron Wind Corp.
Those windmills generated 100 kilowatts or less of power with rotors of 50 to 60 feet across. Today's windmills produce from 660 kilowatts to as much as 2,000 kilowatts with rotors equal to the wingspan of a Boeing 747.
The most vexing problem is achieving a constant flow of power from the unpredictable nature of wind that meets demand, but does not overload electrical grids with sudden voltage increases.
To do this, engineers have focused on designing turbines to generate power at lower wind speeds and continue functioning at higher gusts by partially shutting down to prevent voltage overloads or damage to the gearbox.
Enron has developed a variable wind speed turbine that reaches peak production of 1.5 megawatts at wind speed of 28 mph but also can produce electricity at winds of less than 8 mph, says Bell. When wind velocity exceeds ideal conditions, the blades pitch back to protect the equipment.
On the Net:
National Wind Technology Center: http://www.nrel.gov/wind/
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