Islands present special challenges for utility companies, whether they are large like the Hawaiian Islands or small like Okracoke, a tiny spit of land that juts out into the Atlantic Ocean east of Cape Hatteras, North Carolina. They are also ideal for a microgrid — an electrical system that can generate, store, and distribute power even if it is disconnected from the central grid.
The U. S. Department of Energy defines a microgrid as “a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid and that connects and disconnects from such grid to enable it to operate in both grid-connected or island mode.”
North Carolina has a number of energy cooperatives throughout the state and they have come together to fund the creation of a microgrid on Okracoke Island. The lessons learned there will be applicable to any other co-op that decides to create a microgrid of their own. The effort is a cooperative venture between the North Carolina Electric Membership Corporation, which owns the island’s 3 megawatt diesel generator, and Tideland Electric Membership Corporation, which supplies the island’s electricity.
“This is a learning laboratory for Tideland,” said Heidi Jernigan Smith, company spokeswoman. “We’re exploring the potential for a microgrid.” She and other representatives of the company were on hand in early November to witness the installation of ten Tesla Powerpack grid storage batteries and a collection of solar panels. “We’re setting up here for the electricity of the future,” said NCEMC’s project manager, Bob Beadle. The microgrid on the island is the first in North Carolina.
When connected to the grid, the batteries are charged during periods of low demand and by the solar panels. The electricity they store is available to the grid when demand peaks and power is more expensive. They do not store enough electricity to power the whole island during an outage, but they assist when the generator needs to be started because the initial demand placed often exceeds its capacity.
For example, on a freezing day in March of 2015, power went off from Hatteras to Ocracoke due to ice on the power lines. Tideland tried to start the island’s generator but even in the winter with just year round residents on the island the electric usage exceeded the generator’s capacity. “The Tesla batteries could potentially help us get over that start-up load,” Smith said. “It will be interesting to learn what benefits can be derived from the various microgrid components over time.”
Since coastal environments are the most challenging for electric providers, Ocracoke presented the perfect experiment site, Smith says. Data collected from these items will help the co-ops, including Tideland, learn more about the role of new technologies in future electric service delivery. “This is new territory for everyone,” Smith says. “We’re gaining valuable information for the future.”
When and if power from the mainland goes out, Ocracoke will manage its limited power resources as a separate system independent of the central grid. Microgrids are part of the growing national trend away from large, centrally controlled power plants to local systems using more efficient, renewable energy resources.