Green Power Switch News
Vol. 2, No. 2—Spring 2002

Straight from the mountaintop

TVA’s Buffalo Mountain Wind Farm is showing much promise as a member of the Green Power Switch generating lineup. The wind farm has generated 4.8 million kilowatt-hours since its fall 2000 start-up, somewhat less than projected but still a good showing for the plant’s initial shakedown period. Minor start-up problems have been addressed, and work has been completed on communications equipment that will allow better management and operational control.

Although initial output has been less than anticipated, the wind turbines have functioned extremely well and have been available for production 95 percent of the time since April 2001. Gusty wind conditions and delays in the delivery of replacement parts have been the primary causes of lost production.

Wind-speed variation at the site can be extreme, with wind speeds changing from less than 10 mph to more than 35 mph within a single second and bursts of up to 70 to 100 miles per hour. Under these conditions, sensors cause the wind turbines to go offline, and they have to be manually inspected before they can be returned to service.

Wind measurements continue to be recorded at the Buffalo Mountain site. Additional data will be gathered over the next several years to help improve the accuracy of long-term projections on wind resources in the region. Based on data from the first year of operations, the production output is expected to be 4.6 million kilowatt-hours of electricity each year.

Wind direction and velocity

The figure at right shows that the winds that generate power on Buffalo Mountain generally originate from a westerly direction. When the wind blows from the east, the velocity is greatly reduced and generation is negligible. Since the amount of energy produced is proportional to wind velocity to the cubed power, a slight increase in wind velocity significantly increases production.	Buffalo Mountain, Tennessee 50m Wind Rose Graph January - December 2001

The chart below illustrates the average monthly wind velocity at the Buffalo Mountain Wind Farm and the effect of wind velocity shear. Wind velocity increases with a rise in elevation, and a small increase in wind velocity creates a significant jump in power production. That’s the reason the taller 65-meter towers were chosen. Towers continue to be made taller as wind technology progresses.

Effect of Velocity Wind Shear