The Tennessee Valley Authority is looking to buy up to 2,000 megawatts of renewable energy capacity by 2011.

The nation's largest public utility issued a request for proposals Tuesday to buy enough clean energy from the wind, sun and other renewable sources to supply about 978,000 homes in three years. It would be like adding two new nuclear reactors to the TVA system.

The possible energy sources also could include hydropower, geothermal, ocean, tidal, biomass and other biologically derived fuels, not necessarily produced in the Tennessee Valley.

"We know that there are producers, individuals or entities, out there that would be able to respond," TVA spokesman John Moulton said. "We just want to put this request out and find out what kind of market there is."

Knoxville-based TVA supplies electricity to about 8.8 million consumers in Tennessee, Alabama, Kentucky, Mississippi, Georgia, North Carolina and Virginia.

About 60 percent of that power now comes from coal-fired plants. The agency's goal is to get more than half of its total 35,000-megawatt generation capacity from zero or low carbon-emitting sources, such as nuclear and renewable energy, by 2020.

"We have supported for a long time TVA diversifying its mix by encouraging renewable energy," said Stephen Smith, executive director of the Southern Alliance for Clean Energy. "So this is an important first step. We believe there are a number of really good opportunities in the service territory."

TVA's announcement comes as neighboring investor-owned utilities make their own moves to renewable energy - Florida Power & Light broke ground Tuesday on the first of three solar power projects, Duke Energy Corp. is planning up to 12 wood-electricity power plants and Georgia Power is seeking regulatory approval to convert a coal-fired unit to wood.

TVA is not limiting its search for renewable generation to its 80,000-square-mile territory, though that has been its preference in the past to help both the environment and the economy.

TVA developed the first successful wind farm in the Southeast on Buffalo Mountain, about a half hour from Knoxville, in 2001. The agency's Green Power Switch program sells blocks of renewable energy to consumers for a small premium produced by the 18-turbine wind farm, a handful of demonstration-scale solar collectors and a methane-recovery operation.

Together, those sources generate about 50 megawatts. TVA gets most of its 3,836 megawatts of purely renewable energy from its 29 hydroelectric dams.

Buying 2,000 more renewable, non-nuclear megawatts would be a huge contribution, but may not be enough for TVA to meet tougher clean-air standards under the incoming administration of President Barack Obama, Smith said.

Moulton said TVA's renewables' solicitation is not tied to any clean-air deadlines or a specific budget.

The agency wants up to 1,000 megawatts of renewable generation delivered by June 1, increasing to 1,500 megawatts a year later and to 2,000 megawatts by June 1, 2011.

TVA is targeting individual companies capable of producing at least 1 megawatt of renewable, clean energy that would be willing to sign a power supply contract from 1 to 20 years.