Dive Brief:
- EPB of Chattanooga has deployed five battery-based microgrids with 29 MW/58 MWh of combined capacity across two sites, the Tennessee public distribution utility said Tuesday.
- Two more battery-based microgrids will follow “very soon” as EPB works to harden its grid and reduce demand charges levied by the Tennessee Valley Authority, its bulk power supplier, Ryan Keel, EPB’s president of energy and communications, said in an interview. EPB has 45 MW/95 MWh of front-of-the-meter energy storage in service today, including the new microgrids, and another 45 MW it expects to deploy over the next 12 months, Keel said.
- Next year, EPB plans to deploy an advanced microgrid control platform developed by longtime partner Oak Ridge National Laboratory. The control platform will allow microgrid boundaries to expand or contract based on power demand and available supply, EPB said.
Dive Insight:
The microgrid project was supported by the U.S. Department of Energy’s Office of Electricity, EPB said. On Monday, Katie Jereza, assistant secretary for the office, appeared at events celebrating the microgrids and Oak Ridge’s new control system.
“Microgrids make electricity more dependable when it’s needed most and help reduce energy costs when demand spikes,” Jereza said in a statement.
The public utility’s service territory has about 200,000 customer meters and saw peak demand hit a new record of around 1,350 MW during a cold snap this January, Keel said. Its unique customer mix — spanning urban Chattanooga in the Tennessee River Valley and semi-rural areas in the city’s mountainous exurbs — makes it “almost a sort of hybrid of a municipal utility and a rural electric cooperative,” he said.
Keel said the two microgrid sites announced this week include 2-hour battery systems in urban Chattanooga. They, along with most other energy storage systems on EPB’s grid, will help offset monthly demand charges that can account for one-third of the utility’s total power purchase costs, he said.
That demand charge is set by the hour of each month with the highest demand, “so whenever that hour occurs, we have a financial incentive to reduce that peak with energy storage and other measures,” Keel said.
Under its agreement with TVA, energy storage does not count toward EPB’s self-generation limit of 5% of its own load, Keel said. EPB expects to have 100 MW to 150 MW of energy storage on its distribution system within “two to three years,” he added.
“It’s all front-of-meter from the customer’s perspective, but it’s all behind-the-meter when you’re talking about our relationship with TVA,” Keel said.
Though there’s always a risk that TVA’s posture toward energy storage could change, Keel sees that as relatively unlikely as the nation’s largest public utility grapples with surging power demand.
“The way we see it, this stuff only has increasing value to us and this area,” he said.
In addition to allowing microgrids to expand and contract as conditions change, Oak Ridge’s microgrid platform will enable “nested” microgrids that can provide critical support to EPB’s distribution system and improve reliability, the utility said.
Stephen Streiffer, Oak Ridge’s laboratory director, said in a statement that his organization’s work — and its relationships with utilities like EPB — will help mitigate the effects of extreme weather and other disruptions to the power system and the communities that depend on it.
“Microgrid innovations demonstrated through utility partnerships are enabling safeguards for critical infrastructure and community services in the face of disasters,” Streiffer said.
EPB is developing a smaller battery-based microgrid in a rural area near the end of a radial distribution line, Keel said. Its four-hour discharge capacity reflects the utility’s expectation that it will serve the resiliency needs of an area where power outages are more frequent, he said.
“This is more of an ‘end of our electric system’ residential setting where it will be used more frequently [and] isolated from the grid to serve customers,” Keel said.
The microgrids are part of a larger effort, supported by DOE, to improve grid reliability and resilience in the area.
In 2023, DOE said it would give EPB $32.3 million in matching funding to replace more than 1,300 utility poles, underground over 100 miles of power lines and deploy 15 MW of energy storage at six sites.
Keel said the utility’s work with Oak Ridge on energy storage began “years ago,” when battery technology was not as commercially viable as it is today.
“It has grown into this, but what Oak Ridge has done [in contributing] to our deployment today … goes back to our partnership over many years,” he said.
