Otter Tail Power Company has selected a 1MW/6MWh Eos zinc battery for its first energy storage project, replacing the flow-battery technology originally envisaged for the state-funded demonstration.
The six-megawatt-hour Eos Z3 system will be installed at the University of Minnesota Morris and is expected to be commissioned in 2027. Otter Tail Power will own and operate the battery, which will connect directly to its distribution network.
The project received a $2.408 million appropriation from Minnesota’s Environment and Natural Resources Trust Fund in 2021. Its original work plan specified a flow battery and listed a further $2.5 million contribution from Otter Tail Power, covering 90% of the planned battery purchase.
The final project instead uses Eos’s static, aqueous zinc technology. Unlike a flow battery, the Z3 system does not require pumps to circulate electrolyte. It is non-flammable and designed to operate between -20°C and 50°C without heating, ventilation and air-conditioning equipment.
“It is important to us that we test battery technologies that are well suited to our northern climate without requiring extensive thermal management,” said Bryan Herrmann, vice chancellor for finance and facilities at UMN Morris.
The battery will charge from Otter Tail Power’s grid, including when surplus electricity generated by the university’s wind turbines and solar arrays is being exported. It can then discharge when electricity is needed most.
Earlier project work identified load levelling and peak shaving as the system’s initial applications. Otter Tail Power has also examined using the battery in the Midcontinent Independent System Operator market for ancillary services and energy arbitrage.
The Minnesota Public Utilities Commission approved Otter Tail Power’s investment in March 2026.
“The project will provide an opportunity for utility and university partners to evaluate emerging storage solutions under actual operating conditions,” said Jason Grenier, marketing manager at Otter Tail Power. “As Otter Tail Power’s first battery energy storage project, it also creates opportunities to learn how energy storage technologies may operate within our electric system over time.”
OATI’s GridMind software will control and optimise charging and discharging. Burns & McDonnell is providing engineering support for the installation.
UMN Morris will receive dedicated research periods during the battery’s anticipated 20-year operating life. Researchers will study its performance under different operating scenarios and assess how comparable long-duration systems could support small communities.
The campus generates more than 60% of its daily electricity requirements from on-site wind and solar resources. It also operates lithium-ion and thermal energy storage systems and an agrivoltaics installation.
Diagram: the battery will charge from Otter Tail Power’s distribution grid, including at times when excess electricity generated by UMN Morris wind and solar resources flows onto the grid. The stored energy can then be discharged back to the grid when electricity is needed most. During designated testing periods throughout the year, UMN Morris will also use the battery to study how energy storage can support campus energy needs.
Credit: UMN Morris
