Microgrid protects Chattanooga fire and police services

  • June 7, 2023
  • Steve Rogerson

Chattanooga utility EPB has installed a microgrid at the police and fire department administrative headquarters to generate and provide power in an emergency.

It is able to sustain operations round the clock with enough energy for the fire and police functions to respond to the needs of the community indefinitely.

Functions served by the microgrid include swat team, homicide, fire station, radio control centre, city camera surveillance, and other critical communications infrastructure. Fortunately, there has been no need to use the microgrid in an emergency, although tests take place regularly.

“EPB is a national leader in smart grid technologies, and we’re fortunate to have their level of experience locally to protect our essential services in a sustainable manner that reduces cost and waste and ensures our first responders’ ability to protect our city at all times,” said Chattanooga mayor Tim Kelly.

EPB’s smart grid provides two pathways for power to reach the police services centre and fire department administrative headquarters, so the new microgrid will serve as the third line of defence should widespread outages affect Chattanooga.

“Facing an outage in an emergency is a place none of us want to be, especially as first responders,” said Chattanooga fire chief Phil Hyman. “From the Easter 2020 tornadoes to this spring’s windstorms, we’ve seen how changing weather impacts our safety, and this microgrid will prepare us to be resilient in any event.”

To ensure power resiliency, EPB also relocated a power pole from the front to the back of the building to avoid damage from possible wrecks in the future on the busy Amnicola Highway corridor.

“Our technology depends on electricity, so it’s essential we don’t lose it,” said Chattanooga police chief Celeste Murphy. “It’s a relief to know we won’t have to worry about how we’ll access power should we lose connection to the smart grid.”

The microgrid includes two main generation and storage systems that reduce costs and allow both the city and EPB to recoup their investments more quickly:

  • Generation: The city purchased a 200kW diesel generator and 155kW of solar panels installed on the roof; these were installed behind the meter and reduce the amount of energy consumed at the location, lowering its monthly bill by roughly a fifth.
  • Storage: EPB invested in a 500kW battery to support the microgrid and other grid services; the battery is installed in front of the meter so it can be used to shave peak load during extremely hot or cold weather, reducing TVAs peak demand charge to EPB and keeping energy costs lower for local residents and businesses. EPB does not shave peak load if severe weather is in the forecast; batteries are charged to capacity so they are prepared for an emergency.

Because using energy storage reliably reduces peak demand charges, EPB’s investment should pay for itself within six to seven years and will continue to provide value well beyond the cost of purchasing and installation.

“EPB is committed to establishing microgrids like this throughout our community because they further improve the resiliency of Chattanooga’s power grid,” said EPB CEO David Wade. “This project is a great example of how we’re using microgrid technology to enhance EPB’s local energy mix while providing customised energy solutions to address the specific needs of customers in different areas.”

EPB’s smart grid has 1200 smart switches, sensors and other devices on a 14,500km fibre optic backbone to reroute power automatically when a disruption is detected. EPB continues to expand the local energy mix with distributed energy resources across its 960km service region to improve power resiliency and business continuity for critical community resources and reduce costs for customers through peak demand management. Several projects are being planned, particularly in rural areas that take additional time to reach should the smart grid be unable to reroute power.