Tennessee Valley Authority, the largest public utility company in the U.S., agreed Thursday to buy up to 2,000 megawatts of electricity from renewable energy sources by 2011.

Some of the power is expected to enter into TVA's distribution system as soon as 2010, the Associated Press reported. TVA did not disclose information on which companies will provide the clean energy.

The quantity of renewable energy being sought is substantially more than what TVA will get from its second 1,200-megawatt reactor at the Watts Bar nuclear station which is valued at $2.5 billion and will be completed by 2013.

TVA's board approved the signing of these contracts on Thursday during the firm's board meeting.