Less than 9 miles square and on average 5 feet above sea level, Ocracoke Island in North Carolina’s Outer Banks was almost custom-made for one of the state’s first microgrids. The island is regularly hit by hurricanes and storm surges, and its only connection to the main electric grid is 6 miles of undersea cable.

“The vulnerability of the island’s connectivity to the main grid is always in question in hurricane season,” said Paul Spruill, CEO of Tideland EMC, the electric cooperative that provides power for the island’s 1,400 meters.

Ocracoke has relied on diesel generation since the early 2000s, but in 2015 the North Carolina Electric Membership Corp. (NCEMC), an umbrella group of the state’s 26 co-ops, in a partnership with Tideland, began exploring the possibility of using the island as a test site for a battery storage project. By 2017, the island was home to the NCEMC’s first microgrid, incorporating solar, energy storage and smart thermostats and water heaters to supply emergency power to Ocracoke’s homes, businesses and campsites.

The system’s 62 solar panels provide 15 kW of electricity, backed up with 1 MWh of battery storage, and can disconnect from the main grid to keep the power on in extreme weather or other emergency situations.

Ocracoke is just one example of how North Carolina’s electric cooperatives are outdistancing the state’s investor-owned utilities on microgrid deployment, as well as developing the advanced control systems for leveraging such distributed energy resources to improve overall grid reliability.

The island’s microgrid is one of three systems NCEMC has put online in recent years in partnership with its member co-ops. The group has also launched a new distribution operator (DO) system that serves as a single point of connection and coordination for the microgrids and other grid-edge DERs.

Located on the south coast of North Carolina, the Heron’s Nest microgrid is the state’s first residential project, with each of 30 homes equipped with a 3-kW solar system, smart thermostat and a water heater that can be used for demand response. Butler Farms, a hog farm, hosts the state’s first agricultural microgrid, combining solar and storage with a biogas facility that converts methane from hog waste into electricity.

The Ocracoke and Heron’s Nest microgrids have played a key role in the development of the DO system. NCEMC has partnered with North Carolina’s IOUs — Duke Energy and Dominion Energy — to test how the platform interacts with the grid during peak demand or in emergency situations. The tests demonstrated that using a platform with a single, coordinated contact point could optimize grid-edge resources such as microgrids to generate emergency power and alter load.

“As more microgrids and distributed energy resources are added throughout the grid, the key for electric cooperatives in North Carolina will be to coordinate those resources to work together smartly to meet the needs of the grid and of consumers,” said Lee Ragsdale, NCEMC’s senior vice president of energy delivery.

“The more you connect, the more reliable service is going to be,” said Badrul Chowdhury, a professor at the University of North Carolina, Charlotte, who is heading up a three-year, federally funded project to help develop an advanced microgrid control system.

One of 10 projects nationwide recently awarded grants from the Department of Energy, the project will build a digital “twin” of a microgrid under construction by Duke and use it to develop and test an outage prediction algorithm and simulate emergency situations.

“This project will be a national model for organizing a resilient grid in a state with climate challenges like North Carolina,” said Michael Mazzola, executive director of UNC Charlotte’s Energy Production and Infrastructure Center. With $3.6 million in funding from the DOE, the project is slated to kick off May 1.

Linking Grid-edge Resources

Like many states, North Carolina has become increasingly vulnerable to extreme weather, often intensified by climate change. Data from the North Carolina Department of Environmental Quality show that in the past decade, the state has sustained five extreme weather events each causing more than $1 billion in damages.

Hurricane Florence in 2018 resulted in $17 billion in damages statewide, including extensive damage to North Carolina’s multibillion-dollar agriculture industry. To respond to the ongoing threats of climate change, Gov. Roy Cooper has committed the state to cut carbon emissions from its electric power sector 70% below 2005 levels by 2030 and to be carbon neutral by 2050.

While often under the radar, North Carolina’s electric cooperatives are taking a leading role in the state’s energy transition. The co-ops serve 2.5 million members, and their combined service territories cover 45% of the state.

They are also nimble: smaller than IOUs, unregulated and able to tap into sources of low-interest financing. Across the country, co-ops are experimenting with new business models and new technologies.

The Butler Farm microgrid is a prime example of this small-scale innovation. Tom Butler, the owner, has been a hog farmer since 1995 and realized early on that managing the animals’ waste and the accompanying odors was going to be a challenge. With 8,000 hogs producing 6,000 tons of methane a year, Butler built a 185-kW biogas facility, completed in 2011.

He then began working with his local electric cooperative, South River EMC, and NCEMC to add 20 kW of solar panels to the farm, which, he said, made it a “perfect fit” when the co-op decided to build a microgrid. The system has 735 kWh of battery storage but could be expanded, Butler said.

Twenty-eight co-op members are connected to the microgrid, but the co-op plans to have 160 members connected once pandemic restrictions lift, he said. “South River is going to have as many members on the microgrid as they can,” Butler said. “We can add people as we add battery storage.”

The microgrids have also helped NCEMC test its new DO technology. Working with Dominion, NCEMC used the Ocracoke microgrid to either charge the battery to reduce power from the main grid or discharge the battery and adjust home thermostats and energy use to maintain balance in the system. The thermostats and water heaters at Ocracoke are managed over Wi-Fi by a central controller, so demand and load can be adjusted across the island.

“The microgrid has better enabled us to deliver emergency power and provide better delivery for when we need it,” Spruill said.

Additional demonstrations of the DO system involved a test with Duke and the Heron’s Nest microgrid and another using DERs at Blue Ridge Energy, a co-op in the northwest corner of the state, to test real-time system response to changing weather conditions. In addition to the residential solar systems, the Heron’s Nest microgrid also has a 75kW community solar array and 255 kWh of battery storage.

NCEMC has two more microgrids in development. Eagle Chase, another residential project located north of Raleigh, will be online by the end of March, bringing together propane generators, smart water heaters and 500kW, 1MWh of battery storage. A fifth microgrid with 2 MW of solar and 5 MWh of storage will be commissioned later this year on Rose Acre Farms, an egg production business.

Each project’s development is time-intensive, but Ragsdale expects the number of systems will rise as the price of solar and battery storage drops. “They can and will be part of the transition to clean energy in the state.”

The Critical Role of DER Networking

Coordinating those systems will be critical for grid resilience, said UNC’s Chowdhury, who is preparing to launch the DOE-funded project in partnership with the DEQ and Duke.

The project will test how well the algorithms the team creates can function on a networked microgrid system using a digital twin, a lab-created replica of conditions at Duke’s microgrid under construction in the town of Hot Springs.

A network of microgrids, seamlessly connected to balance generation and load, can strengthen grid resilience in cities after extreme storms, Chowdhury said.

Pockets of rooftop solar, battery storage or other DERs scattered across a city might not generate enough power individually, or depending on the weather, generate none at all, he said. Networking these resources could provide power to critical services such as a hospital, shelter or food bank and more equitably distribute electricity among residents.

“It’s usually the wealthy neighborhoods that have rooftop solar. Other parts [of a city] may be less affluent with not enough generation resource, even though there might be a critical load there,” Chowdhury said. “One of the ways we can address this is [to] bring in generation from an outside microgrid.”

The team will also develop an outage prediction test using an algorithm incorporating 10 years of Duke outage data to pinpoint vulnerable areas of the grid.

The outage prediction algorithm and other tests will be simulated in real-life scenarios using the digital twin system. Inputting weather and generation data from the real Hot Springs microgrid, the team will be able to simulate the exact situation at Hot Springs in the lab to see how the algorithms and networks respond.

Looking ahead, Chowdhury said that the research on microgrid networking is just beginning. “Now we are seeing microgrids for resilience purposes, but I think later it could be for just about anything.”