Energy Purchases from Wind Farms
As of October 2013, TVA has entered into nine contracts with nine wind farms for the purchase of 1,542 megawatts of energy.
The majority of the wind contracts are the result of a TVA request for proposals in December 2008. TVA also has a contract with Invenergy for 27 megawatts from Buffalo Mountain wind farm near Oak Ridge, TN.
EDP Renewables North America LLC
In September 2010, EDP Renewables North America LLC began supplying 115 megawatts from its Pioneer Prairie wind farm in Howard and Mitchell counties in Iowa. Beginning in January 2012, an additional 83 megawatts is being supplied from the same facility.
With that, TVA has contracted for all 198 megawatts of the facility's output, generated by 131 Vesta 1.65-megawatt turbines. An additional contract for 101 megawatts also began delivering energy in January 2012 from the Lost Lakes wind farm.
ENEL Green Power, LLC
In January 2012, ENEL Green Power, LLC began supplying 201 megawatts from its Caney River wind farm in Elk County, Kan. The power is generated by 111 Vesta turbines.
Iberdrola Renewables began supplying 300 megawatts from its Streator-Cayuga Ridge wind farm in Livingston County, Ill., in May 2010. The power is being generated by 150 Gamesa turbines.
TVA does not currently receive renewable energy from this facility, as its Renewable Energy Credits are not currently supplied to TVA. The facility's owner has the rights to the environmental attributes and may sell these attributes to other parties. When TVA exercises its contractual option or a Federal Renewable Energy Standard is enacted, TVA will have the right to the Renewable Energy Credits associated with the facility.
Invenergy LLC supplies 400 megawatts of wind energy:
- The Bishop Hill Wind Energy Center in Henry County, Ill., provides 200 megawatts generated by General Electric 1.5-megawatt SLE turbines. This facility began delivery in July of 2012.
- The California Ridge Wind Energy Center in Champaign County, Ill., supplies 200 megawatts from General Electric 1.6-megawatt turbines. Construction started in 2011, with generation beginning in December of 2012.
NextEra Energy Resources, LLC
NextEra Energy Resources, LLC supplies 315 megawatts of wind energy:
- The White Oak Energy Center in McLean County, Ill. provides 150 megawatts generated from 100 General Electric 1.5-MW SLE turbines. This facility began delivery in January of 2012.
- The Cimarron wind farm in Gray County, Kan., provides 165 megawatts generated by Siemens Power Generation SWT-2.3-93 2.3-megawatt wind turbines. Construction began in 2011 with generation beginning in late 2012.
A wind energy system transforms the kinetic energy of the wind into mechanical or electrical energy. The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor. Wind turbines being manufactured today have power ratings from 1 to 3 megawatts. These can be used as a single unit or grouped together to form large-scale wind farms.
The capacity factor, or productivity, of a wind turbine normally ranges from 25 percent to 40 percent, although higher capacity factors can be achieved during windy periods. The capacity factor is determined by comparing actual production with the amount of power that would have been produced if the turbine were able to operate at maximum output 100 percent of the time.