Photos by Duke Energy on Flickr.

In the case of an outage from a storm or other event, the microgrid is estimated to keep the fire station running in isolation from the electrical grid for two days.

McAlpine Creek Demonstration Project

Charlotte, NC

To meet a growing interest in renewable backup power for critical facilities, such as police and fire stations, Duke Energy is testing a replicable microgrid model in a North Carolina neighborhood. Duke Energy’s McAlpine Creek Demonstration Project uses solar+storage to provide emergency power to Fire Station 24 in Charlotte, North Carolina, serving a neighborhood of about 14,000 residential and commercial customers. In the event of a grid outage, it is estimated that the clean, resilient microgrid will keep the station running in isolation from the electrical grid for two days.

Originally installed in 2009, the solar array at the fire station has a peak capacity of 50kW. A large 200kW/500kWh battery was installed several years later in 2012. The battery was initially installed for the purpose of smoothing electricity flowing onto to grid produced by the solar array. However, increased interest in microgrids from the military and communities looking for cleaner sources of backup power led Duke’s Emerging Technology Office to redevelop the system as an integrated solar+storage microgrid that could disconnect from the grid during disruptions to provide reliable emergency power to the fire station.

The equipment and software to create this resilient microgrid was installed in 2015, using mostly off-the-shelf pieces, so that the project could be easily replicated.  Successful testing of this new solar+storage microgrid design could lead Duke to offer it as a standard service to all of its municipal customers.

Two separate events in 2016 allowed Duke Energy to test the microgrid in real-world situations. First during a lightning storm in April and next during a hurricane in September, the microgrid detected grid instability and disconnected from the larger grid. The power did not go out in either case, but the simple threat of loss of power triggered the disconnection, and the microgrid was able to keep the fire station’s lights, computers, and communications gear running for about one minute, before reconnecting to the larger electrical grid. These tests showed that the microgrid was capable of detecting grid disturbances and switching to islanding, or off-grid, mode in just milliseconds without human intervention. Additionally, during a test of the microgrid in June of the same year, the microgrid ran in off-grid mode for 26 hours during a high energy demand day.

Installation Details

Year Commissioned: 2015

Services Provided: Backup power, Demand response, Ancillary services, Renewables integration

Supported Infrastructure: Fire station

Solar: 50kW

Storage: 200kW / 500kWh battery

Project Partners: Duke Energy