Duke Energy plans to connect microgrid to its distribution grid

Duke Energy Carolinas is planning to connect the Mount Holly experimental microgrid as the first connection to its distribution grid.

The microgrid will be used to regulate voltage as well as improve power quality on the Rankin Substation circuit in Mount Holly. The microgrid will also serve to smooth power production from a 1.2 megawatt rooftop solar project Duke installed at the nearby National Gypsum plant in 2010.

According to the Charlotte Business Journal, the plan to connect the Mount Holly lab to the grid was disclosed in a filing this week with the North Carolina Utilities Commission. It includes the plans to build additional battery storage at the site which will likely be completed in the first half of next year. [Microgrid to “transform” DER and energy storage markets]

The Journal adds that Duke has two other specialised microgrid projects right now — one operating at its McAlpine Substation in South Charlotte and one it is building at Mount Sterling in the Great Smoky Mountains National Park.

The McAlpine microgrid serves a Charlotte fire station adjacent to the substation, which is being used to test whether such micro-grids can be effective in maintaining emergency services during power outages. The Mount Sterling project is designed to provide power just to a single, remote fire tower in the park. The Mount Holly micro-grid will be the first that performs services on the grid generally.

Duke is reported to be testing battery technology and its interaction with solar at the Rankin substation since 2012. In 2015, it established a micro-grid at the site using a 100KW solar installation and a 250KW battery.

Mount Holly research site

Duke Energy used the Mount Holly microgrid, kept off line from the full distribution grid, as a research site to test how to get the storage and power source to interact with grid control equipment and a variety of electronic devices through an “internet of things” connection. [New York offers up $10m for microgrids and DER]

Jonathan Rhyne, a Duke engineer told the North Carolina Utilities Commission, “Duke Energy is working with a select group of vendor partners who share a common goal to standardize the way grid technologies integrate.

“This ‘Coalition of the Willing’ is focused on all aspects from communication to grid control.”

The pilot uses an open-source system to allow secure communication among devices operating on different information technology platforms.

The microgrid was designed to consume all the energy produced in its system at the Mount Holly site. Duke is now planning to connect the microgrid to its distribution system to export electricity from the onsite solar installation and battery system to the grid. Also, it will use the battery system to regulate and improve the power quality of the nearby solar installation and perform additional grid services.

The utility intends to install a second storage battery at the site next month. Along with the inverter and other storage system equipment the additional 650KW battery and storage system will cost about $400,000.