New research from the University of Minnesota Duluth says abandoned iron ore mine pits could be ideal places to store electricity generated by wind turbines.
Wind energy is booming in Minnesota as utilities gear up to meet a state mandate to produce 25 percent of their electricity from renewables by 2025.
But the problem with wind, explains Great River Energy's Vice President of Generation Rick Lancaster, is that it actually blows harder at night.
"That is not a time when we need a lot of electricity," he said. "People have gone to bed, businesses have shut down — we need electricity during the day."
A UMD study has identified 10 sites on the Iron Range for possible use of an old technology known as pumped-hydro storage.
Water in abandoned mine pits would be pumped uphill at night, and stored in a reservoir. Then it would be released to flow down through hydroelectric turbines during the day when electricity demand rises.