OTTER TAIL POWER COMPANY
We're advancing two battery energy storage projects

Maintaining reliable, cost-effective electric service requires evaluating a range of technologies to meet customers' future energy needs. As part of that long-term planning, we're advancing two battery energy storage projects in Minnesota to strengthen system reliability, enhance operational flexibility, and evaluate how energy storage can complement existing resources and support the electric system. 

The projects include the planned Hoot Lake Battery Energy Storage System in Fergus Falls and a collaborative energy storage project with the University of Minnesota Morris.

Hoot Lake project
We plan to build the Hoot Lake Battery Energy Storage System near the Hoot Lake Solar site in Fergus Falls. Connected to the regional grid, the battery will store low-cost electricity from both our energy resources and other power sources available throughout the region. The stored energy can then be delivered when demand is high, helping support reliability and manage energy costs. 

"Our customers count on us every day for the electricity they use at home, at work, and in their communities," said Energy Supply Vice President Brad Tollerson. "Battery storage is one of the technologies we're evaluating as we look at how different resources can work together to reliably meet customers' energy needs." 

The project is in the planning phase and entering permitting and regulatory review. If approved, it would provide approximately 75 megawatts (MW) of capacity for up to four hours, enough electricity to serve tens of thousands of homes for several hours when demand on the grid is high. 

Current estimates show the system could generate approximately $800,000 to $1.2 million in annual property tax revenue while continuing energy infrastructure investment at a site that has supported power generation for more than a century. 

It'll use lithium iron phosphate (LFP) battery technology and include multiple safety measures, including continuous monitoring, temperature control and cooling systems, fire detection and suppression systems, and emergency response planning. 

If approved, construction could begin in 2027, with operation expected in late 2027 or early 2028. 

University of Minnesota project
We're partnering with the University of Minnesota Morris, OATI, and other industry partners on an energy storage project designed to evaluate emerging battery technology. 

It'll provide 1 MW of capacity for up to six hours of storage using a non-lithium battery manufactured by Eos Energy Enterprises. Unlike conventional lithium-ion batteries, this technology uses aqueous zinc chemistry with a water-based electrolyte, providing an opportunity to evaluate an alternative approach to long-duration energy storage. The battery is expected to be commissioned on campus in 2027. 

Under the partnership, we'll own and operate the battery as part of our electric system. The University of Minnesota Morris will have dedicated testing periods throughout the project's anticipated 20-year lifespan to conduct research and evaluate battery performance. The project also creates opportunities for faculty and students to study emerging energy storage firsthand. OATI's GridMind software will manage battery operations while engineering firm Burns & McDonnell will provide support. 

Exploring multiple paths to a reliable energy future
These projects will help us evaluate how different energy storage technologies can support reliability, integrate with other energy resources, and contribute to a diverse portfolio of resources that meet customers' future energy needs. 

"The University of Minnesota Morris has been an outstanding partner in bringing this project to life," said Retail Energy Solutions Manager Jason Grenier. "It gives utility and university partners an opportunity to evaluate non-lithium battery technology and provides valuable insight into how energy storage technologies may operate within our electric system over time." 

We'll continue sharing information and providing opportunities for public input as the Hoot Lake Battery Energy Storage System project moves through the permitting and regulatory process. To stay updated, visit otpco.com/BESS. 

Evaluating a range of resources and technologies helps us plan for changing energy needs while balancing reliability, affordability, and long-term value for the customers and communities we serve.