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As weather events and increased demand strain the electric grid, North Carolina Electric Membership Corp. is offering a new resilience strategy for co-ops everywhere: standardized and scalable microgrids.
“Our microgrid-at-scale program is where we have a consistent design, consistent footprint and a consistent templated control scheme," says Tim Gubitz, director, energy services and technology at the Raleigh-based generation and transmission cooperative. “We're working to simplify microgrids and provide a design that we can take to a cooperative, based on our microgrid experiences and all of our knowledge, to help them."
NCEMC owns and operates five microgrids of various capacity and components that it developed in partnership with member co-ops in different pockets of the state. Its most recent residential microgrid, Eagle Chase, emerged as the G&T's proof of concept for the scalable microgrid template.
“We built a system and then realized it had more capabilities than we were utilizing, and so now we're able to take that benefit to more member-consumers," says Lee Ragsdale, NCEMC senior vice president, strategic projects.
Nestled in a growing neighborhood 20 miles northeast of Raleigh, the Eagle Chase microgrid has a 300-kilowatt generator fueled by propane and owned by Wake Electric, a member of NCEMC. The microgrid also has a 1-megawatt-hour/500-kW Tesla PowerPack battery system owned by NCEMC.
In 2020, the G&T worked with Wake Electric to build the microgrid to serve 30 homes. Two summers later, a storm knocked a tree into power lines and plunged almost 20% of the Wake Forest-based co-op's territory into darkness, but spared those served by the Eagle Chase microgrid. This discovery prompted NCEMC to explore how to expand that resilience and deliver it in the most consistent, cost-effective way to every co-op.
“We wanted to take Eagle Chase and scale that up because we saw the value it offered to Wake Electric's members and we had that initial design approach," says Gubitz.
NCEMC took its plans for a microgrid template to the National Laboratory of the Rockies, where a team of experts with powerful computers created a laboratory environment for the North Carolina co-ops to develop and test microgrid technologies and hardware.
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The lab's “control hardware in the loop" system enabled the G&T to see how the Eagle Chase microgrid could expand its service from 30 homes to more than 300 by adding three reclosers and a new sequence of operations while running its batteries and generators.
Within eight months, NCEMC and Wake Electric's scalable microgrid was put to a real-world test.
An outage-causing incident last fall triggered the microgrid, but it failed to automatically expand beyond the neighborhood. Gubitz and Bryan Oakley, Wake Electric's substation engineering manager, used the national lab to test changes to the microgrid's automation, leading to a solution they were able to deploy within 48 hours.
“Prior to our partnership with the National Laboratory of the Rockies, that would have taken substantially more time and included field testing, and it would have been a much more challenging process," says Ragsdale. “Their capability at the lab allows us to be much nimbler with our deployment of microgrids now and in the future."
With that, he says, NCEMC can ensure its microgrid designs are an asset to share with co-ops at large.
“The important thing is that simplified approach and that consistent approach allow us to build at scale," says Gubitz. “It makes it more economical, more efficient and easier to manage."
In addition to another layer of resiliency, microgrid assets can be used as distributed energy resources to serve all member-consumers when demand and prices increase.
Eagle Chase has been needed strictly for resilience on rare occasions, but the G&T calls on it “multiple times a month for the portfolio benefit that goes to all members," says Ragsdale.
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“We are working with our member co-ops to find new ways to add value to their members through the deployment of these microgrid assets. Paired with our traditional generation, these microgrids are an important part of our overall efforts to uphold reliability and affordability for co-op members in the state."
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NCEMC's microgrid assets total 6.5 megawatts, or about 1% of its 600 MW available DR and DER. As new large loads like data centers come onto the system, the co-op sees a role for microgrids in its “all-of-the-above" generation resource strategy.
“To the extent that it makes sense to have resources like this at the edge of the grid to help supplement traditional generation as we grow, it's a great part of the solution," says Ragsdale.
