Duke Energy Corp. plans to invest $500 million to add nearly 300 MW of battery storage to its portfolio in the Carolinas over the next 15 years.

"Duke Energy is at the forefront of battery energy storage, and our investment could increase as we identify projects that deliver benefits to our customers," Robert Caldwell, president of Duke Energy Renewables Inc., said in an Oct. 10 news release.

Duke Energy subsidiaries Duke Energy Carolinas LLC, or DEC, and Duke Energy Progress LLC, or DEP, initially outlined the potential to deploy the battery storage projects in their integrated resource plans, or IRPs, filed in early September with the North Carolina Utilities Commission. The utilities file separate IRPs for North Carolina and South Carolina, but each plan analyzes the system as one utility across both states.

DEC's resource plan includes a placeholder for 150 MW of "grid-connected battery storage" and also outlines the utility's plans to complete about 260 MW of capacity uprates at its 1,360-MW Bad Creek Pumped Storage Project in South Carolina between 2020 and 2024.

Duke Energy noted that there is currently about 15 MW of battery storage capacity in North Carolina with "far less in South Carolina."

"As the grid operator, Duke Energy can maximize the versatility of storage beyond storing and dispatching of energy to include other customer and system benefits such as system balancing and deferral of traditional grid upgrades," the company said in the news release.

As an example of its clean energy and new technology investments, DEP on Oct. 8 filed an application with North Carolina regulators for a certificate of public convenience and necessity for a microgrid solar and battery storage facility in Madison County, N.C.

The Hot Springs microgrid project will consist of a 2-MW (AC) solar array and about 4 MW of lithium-based battery storage.

"The microgrid will provide a safe, cost-effective and reliable grid solution for serving the Hot Springs area, and provide energy and grid support to all customers," Duke Energy wrote in the news release. "The project will defer ongoing maintenance of an existing distribution power line that serves the remote town."

The microgrid is part of Duke Energy's more than $1 billion Western Carolinas Modernization Project under which DEP will seek approvals for at least 15 MW of new solar generation and a minimum of 5 MW of utility-scale electricity storage. As part of this plan, DEP also will retire the 384-MW Asheville coal plant in November 2019 and replace it with the 560-MW Asheville combined-cycle gas plant.

DEP added that its application is consistent with its 2018 IRP, which "calls for 80 MW of energy storage and approximately 1,000 MW of incremental solar installations over the next five years."