What is a microgrid?
A microgrid is a small electric system that combines local energy resources and control technologies to provide power to a defined area. Microgrids typically remain connected to the main grid, but they can operate independently.
The controller serves as the lynchpin of the microgrid; it can activate demand response components, as well as control generation and storage resources to balance the system’s load with the resources available.
A microgrid can improve system reliability by generating their own power to avoid prolonged and rotating blackouts during and after storm events. In addition, microgrids:
- Connect to the main grid to supplement and diversify power resources
- Serve as a resource that can be called on during times of peak demand
- Provide a learning opportunity that will help discover future uses for microgrids and their components
- Help reduce power supply costs by providing an alternative source of power generation and storage
North Carolina’s electric cooperatives have five active microgrids:
The Ocracoke Island microgrid, located on North Carolina’s Outer Banks, began operation in February 2017. North Carolina’s Electric Cooperatives developed and installed the microgrid in partnership with local cooperative Tideland EMC.
Source: The Sanford School of Public Policy at Duke University
Ocracoke Island’s remote location leaves it vulnerable during weather events and isolated from central power generation sources. The microgrid will support better power reliability for the island, serve as a resource that can be called on during times of peak demand and allow for the testing of system components to discover future uses.
The microgrid components include a controller, solar panels, battery storage, internet-connected smart thermostats, water heater controls and a diesel generator.
Butler Farms Microgrid
The Butler Farms microgrid, located in Lillington, NC, is a microgrid project that integrates components owned by North Carolina’s Electric Cooperatives with resources owned by the farm and seeks to incorporate alternative energy sources, including biogas, solar and battery storage. The farm has existing generation used to support its power needs during times when service has been interrupted, and it also sells power produced from renewable sources, including swine waste and solar, to its electric cooperative, South River EMC. The microgrid became operational in February 2018.
The goal of this project is to learn more about how a microgrid located on a member’s property can be incorporated into the electric cooperatives’ distribution system, and it also serves as a case study for the ways agribusiness and utilities can work together to develop solutions that are mutually beneficial and support both industries, as well as quality of life in North Carolina’s communities.
Components of this microgrid include the controller, solar panels, a Samsung battery, biogas generation and a diesel generator. The microgrid is also being used as an educational resource for local students and teachers.
Located in the eastern North Carolina community of Shallotte and developed in partnership with developer The Adams Group and local electric cooperative Brunswick Electric, Heron’s Nest is the state’s first residential microgrid.
Once fully operational, the site’s 30-plus homes will be equipped with solar panels, demand response water heaters, demand response ecobee programmable thermostats and an option for electric vehicle charging. Energy efficient and sustainable features are incorporated throughout building materials. A portion of the neighborhood is dedicated to a larger community solar array with battery storage.
The community is made up of interconnected loads and resources connected to the main electric grid. On a typical day, residents will obtain power from the main grid, supplemented by power from their solar panels and the community solar array. However, should the connection to the main grid become unavailable — after a storm, for example–the residents will benefit from continued solar power as well as the battery backup system. In addition, the demand response thermostats and water heaters can be controlled by the local electric cooperative to make more power available to the system during that time, as well as during periods of high demand.
Eagle Chase is another residential microgrid being developed by North Carolina’s Electric Cooperatives in Youngsville, NC in partnership with builder Winslow Homes and local electric cooperative Wake Electric, with the goal of providing enhanced electric service reliability and resiliency, as well as reducing peak electricity costs. The microgrid will be able to support the neighborhood for up to 36 hours during outages, and will also remain connected to the main grid during normal operations to provide power diversity and increased reliability.
The Eagle Chase microgrid will include a single 300-kilowatt propane powered electric generator and a 1 megawatt-hour/500 kW Tesla PowerPack battery system. North Carolina’s Electric Cooperatives will own the battery and the microgrid controller that brings the various components together. The microgrid will also integrate smart water heater controls for each home that will help reduce peak demand for power. Wake Electric is offering a rebate for the installation of electric water heaters in each house, and the garage of each home will also be pre-wired for electric vehicle charging.
Rose Acre Farms
North Carolina’s Electric Cooperatives partnered with Hyde County egg producer Rose Acre Farms and its local electric cooperative, Tideland EMC, to develop an innovative agricultural microgrid designed to deliver a variety of benefits to the farm and surrounding community, including enhanced environmental sustainability, reliability and power grid resilience.
The microgrid, which includes a 2 MW solar array, 2.5 MW battery energy storage system and backup diesel generation, typically remains connected to the main grid, adding diversity to traditional power resources. However, the microgrid can also operate in “island mode” during a grid outage to ensure uninterrupted egg production.
The connected battery allows the energy produced by the solar arrays to be stored and then dispatched to the grid when needed, providing for greater resilience and flexibility during times of peak demand or a loss of power to Rose Acre Farms. The on-site solar production is expected to offset about one-third of the total energy consumed by the farm.