Wisconsin Regulators Greenlight State’s Largest Solar Plant

April 15, 2022 by Stephanie Leonida

At 465 MW of total capacity, including 300 MW of solar generation and 165 MW of battery storage, the plant is set to become the state’s largest renewable energy resource.

With the adoption of solar energy gaining pace across Wisconsin, the state’s Public Service Commission (PSC) voted April 7 to approve construction of the 465 MW Koshkonong Solar Energy Center in Dane County, home to the state’s capital, Madison. 

The site’s total capacity is set to dwarf that of any other renewable project in the state, and once online it will provide enough energy to power 60,000 homes. Chicago-based developer Invenergy will spearhead site construction and future operation of the facility, slated for completion in 2024. 


Bringing Solar Power to Dane County

The Koshkonong Solar Energy Center is set for construction within a 6,384-acre swath of Dane County, between the towns of Christiana and Deerfield. Roughly 25 minutes from Madison, the patch consists primarily of agricultural land, interspersed with some grassland and upland forest. 


A map of the projected construction area. Image used courtesy of Invenergy 


Invenergy expects to begin building the site this fall, and will set aside 2,400 of those acres to host the center’s solar facilities, of which major components include: the PV panels, power converter units such as the inverter and transformer, 34.5 kV underground collector circuits spanning roughly 75 miles, a collector substation, a 345 kV generator tie line, and the 165 MW battery energy storage system (BESS).

Invenergy estimates the plant will inject roughly $200 million into the Dane County economy throughout its life. At peak construction, the plant will support an estimated 600 construction jobs, though the company intends to operate and maintain the completed facility with just five full-time employees. 


Furthering Local and State Climate Goals 

Once online, the Koshkonong Energy Center will represent a significant advance in both Dane County’s climate action plan and the state’s wider initiatives. The former, released in 2020, has the county targeting the deployment of 1200 MW of solar power by 2030, a quarter of which would be satisfied by the Koshkonong plant alone. 

According to data from the Solar Energy Industries Association (SEIA), Wisconsin had practically no solar generating capacity until 2017. But the state has seen a comparative explosion in recent years, with 2,697 MW of solar capacity either under development or recently online as of July 2021, according to RENEW Wisconsin, a nonprofit promoting renewable energy throughout the state. 


Wisconsin had practically no solar capacity until 2017. Image used courtesy of the SEIA 

In a written statement, RENEW Executive Director Heather Allen said the site, which will reduce CO2 emissions by an estimated 15 to 20 million tons across its lifespan, equivalent to removing 145,000 cars from the road, represents a “major milestone” for the region. 

In April last year, WE Energies and Wisconsin Public Service, the largest utilities in Milwaukee-based WEC Energy Group’s portfolio, submitted a proposal to the PSC to purchase the plant, together with Madison Gas and Electric (MGE), for $649 million. 

That move furthers recommendations laid out in a December 2020 report by the state’s climate task force, established by Governor Tony Evers in 2019, for utilities to reduce net carbon emissions by at least 60% below 2005 levels by 2030. A separate report from the PSC found that utilities are on pace to reduce aggregate emissions by 44% below 2005 levels by 2026. 


Invenergy Has Multiple Projects in Wisconsin 

In addition to the planned Koshkonong plant, Invenergy is the developer behind three other projects in Wisconsin. 

The company—which recently won on offshore wind lease in the New York Bight auction, covered by EE Power last month—completed first-phase development of the Badger Hollow solar farm, a 300 MW site in southwestern Wisconsin, late last year. Invenergy is also responsible for the proposed Paris and Darien farms, which have respective planned capacities of 200 and 250 MW. Together with Koshkonong, that makes for a combined 1,050 MW in the developer’s Wisconsin pipeline.  


Invenergy's Badger Hollow solar farm. Image used courtesy of Wisconsin Public Service


Invenergy has also been active further south. The company developed each of the three wind farms in Oklahoma’s North Central Energy Facilities project, the largest of which came online last month and is the single largest wind farm built at one time in North America. 


Feature image used courtesy of Thomas Coker/Unsplash