Wind

2003 capacity additions
Cost overview
Cost factors
Recent costs
Where the wind blows
Wind power integration
Wind turbine technology
Wind power business models
Wind power information

The major manufacturers of wind turbines have converged around a standard design, with some variations from one manufacturer to another. The most popular turbines now on the market have a peak output of 1 to 1.5 megawatts, which is typically achieved at a wind speed of about 27 to 30 miles per hour. The capacity factor—a measure of actual annual power output to theoretical maximum output—for modern turbines ranges between 30 and 40 percent, compared with new coal and combined-cycle gas plants, which achieve average capacity factors of 80 percent and 60 percent respectively.

Variable speed turbines

A major technological innovation that has become a standard for the vast majority of new wind turbines on the market is the ability to adapt to the changeable force of the wind. The most notable benefit of these "variable wind speed turbines" is that they start generating power at lower wind speeds and increase power output as the speed (strength) of the wind increases. This results in greater overall power output than previous "constant-speed" turbines. These turbines also decrease system interconnection problems because they are able absorb short-term power fluctuations by using immediate storage of energy on the rotating drive train.

Optimum turbine size

Wind turbines and wind farms are getting much larger as the industry matures, and this trend is reducing the price of wind energy. The most popular turbines now on the market have a peak output of about 1.5 MW, about 50 percent higher than those most frequently installed a few years ago. Other catalysts for large installations are the minimal decline in overall plant output when individual turbines are down; a leveling effect on wind variability across the site; and the need to diversify a resource portfolio or to add capacity quickly. For example, the Bonneville Power Administration, the largest and most hydro-dependent power marketer in the Pacific Northwest, is moving aggressively into wind generation as a means of mitigating low-flow hydroelectric conditions.

The American Wind Energy Association believes that, for the time being, turbines will plateau at 1.5 to 2.0 MW, because efficiency improvements can still be gained on this size of turbine, and larger units will begin to encounter transportation obstacles. Nonetheless, GE Wind Energy (formerly Enron Wind), Vestas, and NEG Micon are all manufacturing turbines larger than 2 MW in size for land application.

The future of wind turbines is likely to bring continued improvements in efficiency, availability, and costs. Most of these improvements will come from many small changes in design, production, installation, and operation, that will continue enable turbines to get more power from lower wind speeds.

Turbine performance measures

For information on performance measures of wind turbines, see Wind Performance Characteristics the Danish Wind Industry Association's Energy Output from a Wind Turbine, which details the factors in determining a turbine's annual energy output.