Duke Energy’s Green Microgrids Run Smoothly through Storm

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Two green microgrids operated by Duke Energy rode through a weakened Hurricane Irma with no hiccups, while customers experienced outages close by.

The first, the Mt. Sterling solar plus storage remote microgrid, serves a communications tower located on National Park Service property in the Great Smoky Mountains on Mt. Sterling, Haywood County, North Carolina.

Duke’s first microgrid that is a regulated asset, the Mt. Sterling microgrid ran smoothly when weakened Irma hit the region and tens of thousands of customers in nearby upstate South Carolina and western North Carolina experienced outages, said Randy Wheeless, Duke Energy spokesman.

“We had a lot of customer outages as weakened Irma ran through, but it was just another day at the office with Mt. Sterling,” he said.

Recent tests of the solar plus storage project showed that the project is running smoothly, said Jon Landy, Duke’s business development manager. The microgrid, which includes 10 kW of solar and 95 kWh of battery storage, is now the primary source of power for the communications tower at the National Park Service, said Landy. It replaced a 12.47 –kV grid-connected distribution feeder and operates independently of the grid.

The second green microgrid that sailed through a downgraded Irma was the McAlpine microgrid test site in Charlotte, N.C. It’s a fire station connected to a substation with a 50-kW solar array and 500-kW lithium-ion battery.

While the project is not a remote microgrid, like the Mt. Sterling project, it can be operated to provide grid benefits when tied to the grid and during outages can operate independently, said Wheeless.

“We’ve had a handful of outages that affected the fire station, and the microgrid kicked in. For all those firemen knew, there were no outages,” he said. This last happened when Hurricane Irma, weakened by the time it reached Duke Energy territory, hit Charlotte, he said.

“We’ve found that in Charlotte with the fire station, the green microgrid is viable, and at Mt. Sterling that viability is carried into a regulated asset,” he said.

Duke chose to use a zinc air battery from Fluidic Energy in the Mt. Sterling microgrid, said Landy.

“We chose that because of the energy capabilities. It can store and dispatch large amounts of energy as opposed to lithium ion and doesn’t have thermal runaway components like lithium ion. There are fewer chances to combust or catch on fire. This is an enhanced safety component that was critical for the location.” Because it’s hard to reach the location, the company wanted to make sure safety was a priority.

Duke Energy has another zinc air battery from Fluidic Energy that the company is studying as part of a research and development project in an internal test bed, Landy said.

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“It was helpful to test that battery before we deployed one in Mt. Sterling,” Landy said.

In addition to finding that the Mt. Sterling microgrid can withstand a mild hurricane, Duke learned about the benefits of engaging and partnering with its microgrid customers, said Landy.

Learn more about Duke’s microgrids at a special hurricane panel discussion during Microgrid 2017 in November.

“What was critical was our engagement with the customer, (the National Park Service). I don’t see this getting done as thoroughly and successfully without their engagement,” he said. The Park Service conducted the environmental due diligence and wanted to make sure the environmental impacts of the project were minimal, he said.

“The Park Service had a huge hand in the design of our project so it has the least amount of impact on the visitors who come to the park and trek the Appalachian Trail,” Landy said.

Duke is confident that the microgrid alone meets the needs of the National Park Service because the battery is large enough to provide electricity for a few days without solar energy.

With these two green microgrids, Duke hopes to showcase the viability of renewable energy-plus-storage projects for the grid and for Duke customers, said Landy.

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“We’re trying to understand and scale that type of system to where it will provide value to our grid and our customers, instead of pilot projects funded by grants and R & D funds. We want to show there are actual business cases for green microgrids,” he said.

Meanwhile, Duke recently announced that it intends to deploy more than 100 MW of energy storage projects over the next five years. Some will be stand-alone batteries intended to address certain issues on the grid or provide certain customer benefits. The company has not yet identified exactly what it will do with the storage, Landy said.

Track news about green microgrids by following Microgrid Knowledge on Twitter @MicrogridNews.

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