Duke Energy is going off the grid.
The Charlotte electric company said Thursday that it plans to supply power to one of its customers, the National Park Service, with 100 percent renewable energy in a remote region that will be disconnected from the utility’s vast network of power plants, transmission lines and substations.
Duke is planning to install solar panels, with 24/7 battery backup, to power an emergency communications tower in the Great Smoky Mountains National Park. Once the “microgrid” demonstrates it’s self-sustaining over a six-month test, Duke will remove the 4-mile-long single overhead electrical line that connects the communications tower to the company’s power grid.
Duke’s motive is financial: Maintaining utility poles and overhead lines in remote and rugged terrain at an altitude of 5,840 feet is more expensive than switching to solar panels and batteries. The price tag of the planned microgrid is confidential, but Duke spokesman Randy Wheeless said it will be less than $1 million.
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“We’ve got a couple dozen poles going up a mountain to serve one customer,” Wheeless said. “In that terrain you’ve got to have helicopters to do O&M,” he said, referring to operations and maintenance.
The utility undertaking the project is Duke Energy Progress, Duke Energy’s Raleigh-based utility subsidiary. While most of western North Carolina is served by Duke Energy Carolinas, Progress serves Asheville and pockets in the west.
The company has maintained electrical service to the tower on Mount Sterling for about 50 years, Duke said in its filing Thursday with the N.C. Utilities Commission. While Duke has been experimenting with microgrids, this would be the first one that’s disconnected from the main grid.
The concept is known as “islanding” or “grid-defection,” said Matt Roberts, executive director of the Energy Storage Association in Washington. He said there are hundreds of microgrids around the country; typically they are capable of “islanding” during an emergency but have not severed their physical connection to the grid.
Duke plans to install a 10-kilowatt solar farm, which is about twice the size of a residential rooftop solar array, backed by a battery capable of running for 9.5 hours at 10 kilowatts. The communications tower provides an emergency link to park rangers.
In addition to the Utilities Commission, the project will require state and federal permits.