Microgrids Are Shifting From Unique to Mainstream

A new initiative offered by Duke Energy, and recently approved by the State of North Carolina Utilities Commission, may be a template for things to come with other utilities that are tasked with serving remote locations in their service territories.

Last week, the Commission approved a solar+storage microgrid that would help Duke maintain reliable power for the town of Hot Springs, N.C., which is currently served by a single 10-mile transmission line that passes through the Pisgah National Forest's mountainous terrain in the western part of the state. The result of the tenuous line is frequent outages, many of which are lengthy in nature.

The project, the first utility-scale solar+storage undertaking for Duke, will include a 2-megawatt (MW) solar array and a 4-MW lithium-ion battery. While the Hot Springs microgrid will be capable of "islanding,” or running independent of Duke's grid during grid-related outages, it can also, while it is grid-tied, provide essential reliability services, such as frequency and voltage regulation, ramping support, and capacity during system peaks.

"Though it is not clear that the Hot Springs Microgrid is the most cost-effective way to address reliability and service quality issues at Hot Springs, the overall public convenience and necessity would be served by granting the certificate," the Commission said.

The Commission approved the plan for another reason. It believes the completed project could provide significant information on whether storage technologies in general can be integrated into the state's electric grid on a more widespread basis. The Commission noted that system benefits from the Hot Springs Microgrid are material, "but are difficult to quantify accurately without real world experience in [Duke's] service territory." It added that "this experience and data collection and analysis will be beneficial in future cost-benefit analyses of projects with that proposed to include an energy storage component."

Duke subsequently announced it plans to roll out even more storage on its system, with plans to spend $500 million on battery storage in the next 15 years.

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