In February 2017, the North Carolina Electric Membership Corporation (NCEMC) and Tideland EMC launched a microgrid project on Ocracoke Island in the Outer Banks. The microgrid was the first in North Carolina electric cooperative territory, but it wouldn’t be the last.
Microgrids are independent electric systems that use local energy resources and control technologies to help power a defined area. They provide a number of benefits that make them a key player in the smart grid of the future. They can increase grid reliability and resiliency, ease periods of peak demand, test system components and future technologies, and act as an alternative source of generation and storage to reduce power supply costs.
For North Carolina’s electric cooperatives, which provide reliable, safe and affordable energy services to more than 2.5 million people in the state, microgrids represent another way to better use grid resources and serve their members. NCEMC’s interest in the technology began a few years ago, with the generation and transmission cooperative wanting to explore how different technologies and resources could be harnessed together with the electric distribution system. Ocracoke Island, which is served by a single submarine transmission line and susceptible to severe weather events, was a natural fit.
The result was a microgrid containing a diesel generator, Tesla batteries, a rooftop solar array atop the diesel plant, connected thermostats and water heaters for demand response, and a controller that makes everything go. The system’s combination of supply-side and demand-side components provides significant flexibility, allowing new capacity to mesh with reduced load in a balancing act. “It was sort of a living laboratory,” described Jim Musilek, director of grid modernization at NCEMC, “and we went through and we tested several use cases, and we were able to see where the lessons learned and challenges were.”
Using the local resources of the microgrid reduces Ocracoke’s reliance on the larger grid, and while the microgrid cannot replace the grid’s infrastructure, it can improve performance and speed recovery during a loss of power.
It also helps that there has been substantial excitement surrounding the technology. “The people on the island were extremely supportive of it,” said Heidi Smith, manager of marketing and corporate communications at Tideland EMC. “They were really proud to be the first microgrid.”
The Ocracoke system faced a real test when a construction company severed a transmission cable and caused a weeklong outage in July 2017, which was devastating for a region that relies heavily on summer tourism. Thousands of visitors had to evacuate, but residents of the island actually had power, and the microgrid had a role to play. The demand response capabilities of the water heaters and thermostats helped reduce load on certain circuits, and the solar plus storage combination performed as expected.
It is the controller, though – which is customized for each application – that is the key piece of the microgrid puzzle. “The components are relatively easy to acquire and place out in the field,” explained Musilek. “The real challenge is getting them all to work together in a way that optimizes their collective value and benefits the grid.”
As NCEMC was studying the effects of its first microgrid, it was working to get another online, this time a first-of-its-kind biogas system in Lillington, North Carolina. The project is a collaboration between NCEMC, South River EMC and Butler Farms, a local hog farm. “This pilot is an investment in the potential benefits of future microgrid applications for our members,” stated Cathy O’Dell, vice president of member services and public relations at South River EMC. “We are excited to gather information and determine all the benefits that can be gleaned from the project.”
The Butler Farms microgrid has another added benefit: It demonstrates the promising potential for collaboration between two of North Carolina’s most vital industries: energy and agriculture.
“We wanted to do something that was at the crossroads of agriculture and electrification because we’re a rural electric cooperative. Rural agricultural communities are a huge part of our service territory,” Musilek noted. “So Butler Farms was the perfect opportunity for us.”
Tom Butler, the farm’s owner, was all for the idea. “Tom Butler is a great partner. He is passionate about being a good steward of the environment and committed to helping to improve the image of hog farming across North Carolina,” described O’Dell.
The Butler Farms system includes three components owned by the farm – a biogas generator using the farm’s swine waste, a diesel generator and a solar array – and two owned by NCEMC – a battery storage system and the ever-so-important controller. This unique joint ownership could act as a model for future integrations of member-owned and cooperative-owned resources that benefit the entire membership.
South River EMC and NCEMC also added reclosers to the distribution grid, which are devices that allow parts of a grid to be isolated from each other. In other words, as is the case on Ocracoke Island, the Butler Farms system can operate independently of the grid in a state known as island mode. This functionality could be particularly important when an outage occurs. Currently, the microgrid would be able to provide power to nearly 30 homes, though that number could grow in the future. “South River EMC’s service is highly reliable, but if there were an outage for whatever reason, those homes would continue to be served,” Musilek said.
With their versatility and grid-enhancing capabilities, microgrids will play a critical role for North Carolina’s electric cooperatives. The systems in Ocracoke and Lillington help diversify the power grid, improve reliability and resiliency, and provide a learning opportunity for future demonstrations. NCEMC continues to work with its member cooperatives to explore and develop other avenues for the technology. “We’re looking at a couple of different projects right now that we think we may be able to do something where it benefits the member consumer and benefits the co-op as well,” said Musilek.
In a related early-stage pilot, NCEMC is partnering with Brunswick EMC and a local developer on an effort that will build homes equipped with solar panels and connected thermostats and water heaters. Battery storage is also being explored. “This neighborhood, through its own solar generation, the battery and demand response, could essentially be self-sufficient for a prolonged period,” explained Musilek.
The energy world is moving quickly, and advanced technologies are becoming more viable. “That’s why we started trying to do this work a couple of years ago,” Musilek said. Indeed, with microgrids, North Carolina’s electric cooperatives are on the cutting edge, ready to meet new challenges that come their way.