Battery storage developer-operator Spearmint Energy has received a site permit for the 150MW/600MWh Midwater Energy Storage Project, in Freeborn County, Minnesota, US.
Announced 16 July, Spearmint received a site permit for the battery energy storage system (BESS) project from the Minnesota Public Utilities Commission (MPUC). It will be sited on 10 to 20 acres of privately owned land adjacent to the Glenworth Substation off Minnesota Highway 65 in Freeborn County.
Midwater is Spearmint’s second project to advance through Minnesota’s state permitting process, following the successful permitting of the company’s 150MW/600MWh Snowshoe Energy Storage Project in Olmsted County, in 2025, which was the first standalone battery storage project approved in the state.
According to documents filed with the MPUC by Spearmint, operating as Midwater BESS, LLC, the total installed capital cost for the BESS project will be approximately US$457 million. Operating costs are estimated at US$246 million over the project’s lifetime, including labour and materials.
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The preliminary design also incorporated a modular layout of enclosures based on Tesla’s Megapack 2XL lithium iron phosphate (LFP) BESS solution.
Last month, Spearmint secured a US$325 million expanded debt facility in partnership with Nuveen Energy Infrastructure Credit, Elda River Capital Management, Harrison Street Asset Management, and Aiga Capital Partners. The funds are expected to advance the company’s operating portfolio including the100MW/200MWh Tierra Seca, 100MW/200MWh Seven Flags, and the 150MW/300MWh Revolution BESS projects.
Prior to that, Spearmint secured approximately US$450 million in project financing to support Red Egret, a 300MW/600MWh BESS project currently under construction in Texas City, Texas.
In April, the MPUC approved a 200MW expansion of utility Xcel Energy’s Capacity*Connect virtual power plant (VPP) programme, designed to deploy a network of utility-owned, community-based BESS, aggregated into the VPP.
The programme and the MPUC’s decision were controversial, with several clean energy trade groups taking issue with its design. As approved the programme requires Xcel to provide regular status reports and undergo an independent review. The MPUC claimed this would allow it to maintain a high value for ratepayers and uphold the state’s commitment to a clean energy transition.
