How Microgrids can make the rural energy grid more resilient and sustainable

Running a farm like Rose Acres takes a lot of power.

In the six-county service area where Tideland EMC operates, the egg farm uses more power than any other customer to keep operations running non-stop and the 2.2 million hens on-site safe and healthy.

Access to lots of reliable energy is essential to the farm, which is why for the past two years, the farm has been producing much of its own power.

With 2MW of solar and 2.2MW of battery storage, the farm is home to one of the state’s largest microgrids.

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It’s a power source for the Tideland EMC grid that can “island off” in case of emergency. That means during an outage, the microgrid temporarily separates itself from the rest of the grid and the farm can run independently on the power it produces and stores. The solar would charge the batteries, the batteries would power the farm’s essential services. If the outage continued past what the solar system could provide, the farm’s backup diesel generators would kick in.

Before the microgrid, Rose Acres relied solely on a fleet of diesel generators for backup power. While some of them remain on site, the microgrid has dramatically reduced how often they’re used and in turn, reduced the farms’ emissions.

Lee Ragsdale is the senior vice president of the North Carolina Electric Cooperatives, which oversees Tideland EMC. He describes the concept as a way to improve the reliability of electricity and sustainability on the farm, while helping power its neighbors.

“By having resources located in the community that they serve, they improve the reliability and the resilience in that area,” Ragsdale said.

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When out of island mode, Ragsdale said the energy created on the farm is providing locally sourced power to the Tideland EMC portfolio but the 2 MW of solar and 2.5 MW of storage is a fraction of what the rest of the grid produces. That’s why when the microgrid does go into island mode, it doesn’t hurt the rest of the utility’s customers. In fact, Ragsdale said it allows Tideland EMC to focus on stabilizing the grid and restoring power to the rest of its customers, without having to worry about serving its largest one.

“It’s contributing to the greater grid at all times,” he said.

The Rose Acres microgrid is one of five N.C. Electric Cooperatives operates throughout the state. The others include another farm, two small residential microgrids, and the island of Ocracoke. All of them are either in areas that are remote or otherwise difficult to service in an emergency or, in the case of the farms, were 24/7 operations that wanted more sustainable electric resiliency measures.

The interest around energy resilience microgrids is growing with climate change and the threat of severe storms. Charlotte’s Fire Station 24 added an early, small-scale microgrid in 2015 and Duke Energy added an all-renewables microgrid in Hot Springs, N.C. last year.

Ragsdale said N.C. Electric Cooperatives is interested in expanding its resiliency projects like microgrids but there’s still a lot to learn from their current microgrids.

Two years in, Ragsdale said the microgrid has worked well for Rose Acres farm. It’s only had to island itself two or three times and the switch happens so quickly, engineers report it usually goes unnoticed as the farm continues its operations.

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