The Delaware Electric Cooperative and its 11 sister co-ops have signed an agreement to buy power from a planned land-based wind farm in Pennsylvania.

The Old Dominion Electric Cooperative has signed a 15-year agreement with AES Corp. for power from a planned wind farm straddling Tioga and Bradford counties in north-central Pennsylvania. It is named the Armenia Mountain Wind Energy Project.

The purchase includes half the power and half the renewable energy credits from the facility, which is expected to produce between 100 and 140 megawatts of power when the wind is blowing hardest, the company reported.

Delmarva Power will purchase the other half. Delmarva announced its involvement in this project last month.

The first 100-mw phase of the project is expected to be finished in November 2009. It's unclear when the rest of the project will be completed, if at all.

"You want to diversify your portfolio. This was a very good price. It will fit in with the overall cost of what we thought the power would be over the long term," said Jeb Hockman, spokesman for Old Dominion.

He declined to disclose the per-megawatt hour price, but expressed confidence the project would be built to its maximum planned size.

The cooperatives have not sought power from Bluewater Wind, the developer of a 200-megawatt offshore wind project planned off Rehoboth Beach. The costs of that project will be spread out to all customers who get their power from Delmarva transmission lines, regardless of whether they buy their electricity from Delmarva.

Delaware Electric Coop officials have said that offshore wind power is too expensive.

It would be in the co-ops' interest to consider offshore wind, said Jeremy Firestone, an associate professor at the University of Delaware, and a Bluewater supporter. Offshore wind turbines blow more consistently than on-shore wind farms at peak electricity demand times, Firestone said.

"It's a more valuable product," Firestone said. "The mere fact that it costs more is not the end of the question."

If the federal government taxes carbon emissions, the offshore wind power could be less expensive than burning coal, resulting in local fossil fuel burning plants being turned down, Firestone said. That can't happen if the wind farms are far away in another state, he said. Far-off wind farms also can't help relieve congestion on local transmission lines, he said.

Unlike Delmarva Power, the cooperatives have no state requirements to buy renewable power. Neither do the nine municipal electric utilities in Delaware, although they signed a contract last year for a small amount of power from the Bluewater project.

Old Dominion is made up of 12 member electric distribution cooperatives in Delaware, Maryland and Virginia.