Duke Energy Corp. , through its division that deals with renewable energy sources, has purchased a 20-megawatt solar project in northeastern North Carolina from Ecoplexus Inc. The Charlotte-based utility did not disclose financial details in its news release this week . The project, located in the Currituck County town of Shawboro, generates enough electricity to power 4,000 homes and has a 15-year agreement in place to sell that energy to Dominion North Carolina Power, a subsidiary of Richmond, Va.-based Dominion Resources Inc. .