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Published on November 24th, 2011 | by Andrew

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Minnesota Study Finds Promise in Using Abandoned Mesabi Iron Range Mines to Store Wind Energy



Photo courtesy Mining Artifacts

A study from the University of Minnesota-Duluth’s Natural Resources Research Institute (NRRI) finds the potential is there to re-purpose abandoned open pit iron ore mines in northeastern Minnesota’s Mesabi Iron Range to store energy from wind turbines and farms, according to a Midwest Energy News (MWEN) report. Doing so would not only enhance the competitiveness of wind power, it would make beneficial use of land that’s been severely degraded.

Wind energy has been growing fast in Minnesota, thanks to its geography, climate and impetus from the state’s Renewable Portfolio Standard (RPS), which requires that utilities and electric co-ops at least 25% of their electricity from qualifying renewable sources by 2025.

Being able to store wind energy at scale would be a major breakthrough. Wind power production is typically 25% of total rated capacity due to the intermittent nature of wind and the inability to store it when excess electricity is generated.

Wind power production typically picks up at night when wind energy is higher. Electricity demand is lower at night, however, and suppliers selling power into the grid at night typically receive significantly lower prices than they might if they could sell it during the day. Wholesale electricity prices in Texas, as well as other areas, actually dropped to zero due to high levels wind energy production recently.

A Relatively Simple, Clean & Highly Efficient Means of Storing Energy

Minnesota Power and Great River Energy, two Minnesota electric utilities that have signed large, long-term wind power purchasing agreements (PPAs), helped fund the NRRI study, which looked into the policy, topographical and environmental, as well as energy storage, aspects of hydroelectric pumped storage systems at abandoned open pit mines in the Mesabi Iron Range.

Hydroelectric pumped storage systems were first used in Italy and Switzerland in the 1890′s, Energy Journalism Fellow Dan Haugen writes for MWEN. Some 104 gigawatts (GW) of electricity capacity was stored in hydroelectric pumped storage systems worldwide in 2008, according to the US Energy Information Administration (EIA), with the US accounting for just over 22 GW, or around 21% of the total.

The system’s basic design requires a permanent reservoir of water at a lower elevation and a temporary holding pond at a higher elevation. In the case of storing energy from wind turbines and farms, the water would be pumped from the reservoir to the holding pond during the night and then released during the day, passing through a water turbine or turbines on their way back down to the reservoir during the day as required by electricity demand.

Hydroelectric pumped storage systems are highly efficient – 85% of the stored energy can typically be converted into usable power. They’re also relatively inexpensive to operate and maintain, and precise in their ability to deliver electrical power on demand.

They are costly to build, however. A 1,000-megawatt plant can cost around $2 billion to build. Using abandoned open pit mines that are already filled or partially filled with water would eliminate, or partly eliminate, one entire phase of construction, according to Haugen’s report. That would lower the up-front capital costs. A significant amount of capital would still need to be invested in equipment and drilling the system’s tunnels, one industry source told MWEN.

Cost and Other Considerations

Don Fosnacht, the study’s lead investigator and director of NRRI’s Center for Applied Research and Technology Development, told Haugen he thinks a 100-megawatt mining-pit system could be built be built for around $120 million, although that is just a rough estimate.

Environmental effects, along with the potential for abandoned iron ore mines to be reopened if iron ore prices continue to rise are also key considerations that the researchers and study sponsors need to evaluate in more detail before proceeding, however.

“It’s very difficult to manage [wind] without some kind of storage capability, and that’s where this type of project fits in,” Fosnacht was quoted as saying. On the Mesabi Iron Range, “the potential is certainly there, based on our study.”

 

“The Laurentian continental divide crosses the region, which slopes down from there several hundred feet to Lake Superior. Its topography is also pocked by just over 100 iron ore pits that were mined to varying degrees during the last century. Some are still used in taconite http://en.wikipedia.org/wiki/Taconite mining operations, but many are abandoned and have since filled with rain water,” Haugen writes.

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About the Author

I've been reporting and writing on a wide range of topics at the nexus of economics, technology, ecology/environment and society for some five years now. Whether in Asia-Pacific, Europe, the Americas, Africa or the Middle East, issues related to these broad topical areas pose tremendous opportunities, as well as challenges, and define the quality of our lives, as well as our relationship to the natural environment.



  • Anonymous

    How deep are these pits? Deep enough to provide adequate head? If you pump one dry is there enough change in elevation from the surface level of one adjacent?

    Or are they located along steeply sloped areas so that there is adequate fall from one to another?

    Germany is beginning to install pump-up in abandoned mines. Lots of head in a deep mine and often plenty of water. It requires only a reservoir at the surface large enough to hold the maximum number hours of water.

    It might be possible to find mines which have side tunnels at different depths and put the entire operation below ground.

  • Sean Hancock

    I am from the Mesabi Iron Range. All I have to say is the land is littered with water-filled abandoned iron ore mines. This idea makes sense.

  • Michael

    Really, Cleantechnica? This is just lazy.

    Energy storage capacity needs to be given in units that evaluate to a quantity of energy, not power. A number given in Joules would make sense, or even preferably megawatt-hours (MWh) or gigawatt-hours (GWh). To quote energy storage capacity in terms of megawatts or gigawatts alone? Nonsensical.

    A megawatt of power might be enough to light an incandescent bulb for thirty seconds or to power 500 homes for a day, all depending on how long that megawatt of power is applied.

    Without that knowledge, this article is useless.

    • Akbweb2

      Funny, the US EIA uses millions of kilowatts in its tables for hydroelectric pumped storage, and thats what’s used in the source article as well…Couldn’t find a copy of the original report.

      And lemme see a 100 MW capacity power plant turned on for one hour would produce 100 MWh of energy…The watt is a measure of instantaneous power. What’s the problem?

      This would render your comment as, well, useless…

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