Safe Energy  

Clean Energy for a Sustainable Future

Report on Wind Powering America technical workshop and Green Mountain Wind Farm

Louis Zeller October 24, 2000

The Green Mountain Wind Farm is located in southwestern Pennsylvania on the site of a former strip mine. The farm has eight wind powered electric turbines which generate a total of 10.4 megawatts, enough electric power for 2,500 homes.

On the day I visited Green Mountain, the wind was moderate and all but one turbine was operating. Arriving at the farm, I spotted the 200 foot tall towers from a distance. At the entrance our tour bus stopped at the visitor center which overlooks the rolling countryside, a barn and silo, fields of corn and hay, and eight wind machines. The serenity of the farm was accented by the majestic white rotors turning slowly in the breeze.

As I approached the rotor, I expected to hear a sound of a blade swishing through the air, a humming turbine, or some other noisy signature of the industrial age. But when the tour group reached the base of the structure, the loudest sound by far was from people around me speaking in normal conversation. I made an audio/video recording at the base of the tower which supports the rotor turning 100 feet overhead. No sound except the faint hum from a nearby transformer.

Green Mountain Energy Company purchases the electricity for its customers and power is distributed through the Somerset Rural Electric Cooperative. The site is leased from the owner who continues to live on the 500 acre farm. Over 90% of the farm continues to be used for agriculture. Green Mountain Energy initiated the project in 1998 and operation began May 1, 2000. The company selected this site 2,300 feet above sea level based on analysis of wind energy potential in the Appalachian-Allegheny Mountains with an eye toward minimal environmental impact and benefit to the local economy. Green Mountain Energy works in partnership with a British firm National Wind Power which owns and operates the generators. This arrangement shared credit risk and enabled them to complete the project in less than two years. The total development cost was about $10 million. Experts estimate that average annual wind energy potential in Pennsylvania is 38 billion kilowatt-hours.

The turbines need a minimum windspeed of 8 mph to generate electricity, achieve maximum output at 34 mph, and shut down when the wind exceeds 56 mph. The rotors turn at a steady rate, at either 12.7 or 19 rpm. The rotor speed is moderated by computerized controls which vary the load on the turbines so that stronger wind generates more power, not more speed. A computer also keeps each rotor pointed into the wind.

The environmental benefits of wind turbines include zero air and water emissions and no solid waste. Power generated annually at Green Mountain Wind Farm displaces fossil fuel electricity which would emit 35 tons of nitrogen oxides, 135 tons of sulfur dioxide, and 17,000 tons of carbon dioxide. This is equivalent to the pollution generated by 40 million vehicle miles, or the annual CO2 absorbed by 2 million trees.

Early wind turbine generators earned a reputation for being noisy neighbors. But modern units seem to have eliminated this problem. Normal conversation 3 feet away produces 55 decibel. Typical noise from a wind generator 500 feet away is 45 decibel. The worst-case assessment for a large 90 megawatt wind project with 60 turbines predicts a 40 decibel sound level one-half mile away, equivalent to a quiet room.

What is the impact on wildlife, particularly birds? The companies completed an avian risk assessment which indicated no potential risk to bird populations from the operation of the wind farm. They attribute this to improved blade design and the controlled speed of the rotors.

Cost of wind generated electricity has dropped from 40 cents/kilowatt-hour in 1979 to 4 to 6 cents/kilowatt-hour today. According to the Department of Energy, prices will continue to fall and by 2010 continued advances in technology will further reduce cost to about 2 to 3 cents/kilowatt-hour. Wind Powering America’s goal is to have 5% of American electricity generated by wind by 2020.

BREDL video clip BREDL video clip.
Panoramic view of wind turbines at Green Mountain Wind Farm. Play video clip.
BREDL video clip BREDL video clip.
Close-up of wind turbine at Green Mountain Wind Farm. Play video clip.

US Department of Energy Wind Powering America program

Green Mountain Energy

National Wind Power