Duke adds hydro to clean energy mix

Charlotte-based Duke, the state's biggest power company, registered four small hydroelectric plants, including two in North Carolina, with the N.C. Utilities Commission. Even though the hydro plants are decades old, they count toward Duke's green energy targets under an exception in state law.

The registration will allow Duke to claim renewable credits for the clean electricity generated at those facilities towards meeting the state's renewables mandate. A 2000 state law requires that 12.5 percent of all retail electricity sold by utilities in this state come from renewables, such as solar power, and from energy conservation projects.

Most of the renewable resources tapped in this state have been solar energy farms, but they've also included biomass such as burning agricultural waste and landfill methane gas to generate power.

The 2007 law requiring more renewables says that green energy facilities in existence before January 1, 2007 don't count towards the state mandate. That would disqualify Duke Energy's existing hydroelectric capacity of 617.5 megawatts and Progress Energy's capacity of 228 megawatts, many of which were built before World War II.

Existing facilities don't count under the law because power companies could meet their state mandates with hydroelectric dams built nearly a century ago.

However, the state's energy law includes an exception for existing hydroelectric power plants that have a capacity of 10 megawatts or less.

The exception allowed Duke to register four small facilities — two in this state and two in South Carolina — ranging in capacity from 1.8 megawatts to 9.6 megawatts.

Duke's Tuxedo Hydro Station in Henderson County, dating back to the 1940s, generates 6.4 megawatts. The Mission Hydro Station, built in 1920 in Cherokee County, has a capacity of 1.8 megawatts.

They're not the first hydroelectric plants to qualify as renewable facilities in this state. A year ago, Northbrook Carolina Hydro, based in Arizona, registered a 5.5 megawatt hydro plant it owns in Polk County.

The Northbrook facility is free to sell wholesale electricity to another power company, rural electric cooperative or municipal power agency. Northbrook can sell the renewable energy certificates from its hydro plant to any entity interested in buying the credits to meet state renewables mandates or corporate sustainability goals.