• Minnesota solar facility can be sustainability model


    MANKATO, Minnesota: The piece of land just east of Mankato was prairie for thousands of years. A century and a half ago it was plowed into farmland. Last year it was transformed to a massive solar array.

    And this spring, the parcel will become a first-of-its-kind research laboratory—studying ways to make harmonious neighbors of solar arrays, prairie plants, and agriculture.

    “We certainly are aiming to demonstrate this in practice as well as theory that solar developments can coexist with agriculture in a very effective way,” said Marcus Krembs, director of sustainability for Enel Green Power North America. “This is a really exciting project.”

    Enel, which constructed the array as part of its 150-megawatt Aurora solar project, recently reached a research agreement with US Department of Energy’s National Renewable Energy Laboratory. The joint study will examine best practices for vegetation selection and management at three Minnesota solar arrays in the 16-array Aurora project, including the 44-acre (17-hectare) Eastwood array midway between Mankato and Eagle Lake.

    With photovoltaic panels now covering thousands of acres of land in Minnesota alone, the results of the study are expected to be used by the state Department of Natural Resources (DNR) in refining requirements for plantings at solar arrays. The research will look at which plants work best for bees, butterflies and other pollinators; how different plant species impact the health of the soil; and what mix of plants can keep the air cooler within a solar array, which boosts the efficiency of solar panels.

    The Mankato site was chosen, along with arrays near Atwater and in Chisago County, to provide diversity in ecological and soil characteristics, Krembs said.

    At the Mankato array, three acres of land will be divided into plots with varying seed mixes of pollinator-friendly plants and differing planting techniques, said Jordan Macknick, an energy engineer and environmental analyst for the federal renewable energy lab.

    “Many different species will be planted, including flowers like the prairie coneflower and black-eyed susan, grasses like fowl bluegrass, and legumes like white prairie clover to put nitrogen back in the soil,” he said.

    Continuous monitoring

    The scientists will also be installing instrumentation to measure the microclimate just above the ground and any changes in the composition of the soil.

    “To fully capture not only what grows well, but also why, the team will be instrumenting the test area to monitor soil moisture and temperature, air temperature, and humidity, carbon uptake in the soil, and other factors that can affect plant growth,” Macknick said.

    Results will be compiled over the next three years and are expected to fill a gap in scientific literature on the topic while also helping the DNR develop more effective planting standards for the solar installations in Minnesota.

    Along with the scientific instrumentation, the researchers may be looking to partner with colleges and possibly citizen-scientists to, among other things, quantify how the different plantings are impacting the population of bees and other pollinators, Krembs said.

    If nothing else, area residents interested in ecology will probably be able to get a look at the research project—assuming they’re willing to sit through a short safety seminar and wear a hardhat.

    “We’re really excited about hosting tours,” Krembs said.

    The Mankato array—which was incorporated into city limits when it was developed—is about 1.5 miles east of the intersection of Highway 22 and Hoffman Road. The overall $290-million Aurora solar project began generating power for Xcel Energy last summer and can, on average, meet the electricity needs of 16,000 homes.


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