Energy Storage Concepts

Renewable Energy

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Arial view of a pumped hydro facility, one pond at a higher elevation and a second pond.

Minnesota has an $18 billion annual energy bill. As we move forward with renewable energy targets to address energy independence, greenhouse gas emissions and economic growth, energy storage will become increasingly important.

Once renewable energy (wind, solar, hydroelectric, biogas) assumes more than 30 percent of the energy portfolio (including fossil fuel-based energy generation), energy storage becomes critical to maintain grid viability. Power sources – other than base load power plants – are required…in this case, an energy storage capability coupled with the intermittent power source which can deliver electricity in a similar fasion as the base load plant. This would allow renewable sources to reliably supply electrical energy on a 24-hour basis.

NRRI has been working with many collaborators to develop concepts on how to use Minnesota’s assets as renewable energy storage facilities. There are three areas of focus:

Compressed Air Energy Storage

This concept uses excess renewable energy to compress air into a container and release through a turbine generator when power is required. NRRI and collaborators completed a study in 2016 concerning the use of Minnesota’s underground mine caverns as compressed air storage units. "Compressed Air Energy Storage in Northern Minnesota Using Underground Mine Workings and Above Ground Features." Read the full technical report: PDF iconcaes_final_report_2016.pdf

Pumped-Hydro Energy Storage

This concept essentially uses excess renewable energy to pump water to an elevated holding area (lake) and release to a lower lake through a turbine generator when power is required. NRRI and collaborators completed a study in November 2011 concerning the use of Minnesota mine pit lakes as pumped-hydro candidate sites. "Pumped Hydro Energy Storage Using Abandoned Mine Pits on the Mesabi Iron Range of Minnesota." Read the full technical report here.PDF iconphes_final_report_1.pdf

Hybrid Systems

NRRI has identified a hybrid, underwater compressed air energy storage system that uses water pressure to force air back through a turbine generator. Minnesota’s mine pits appear to be ideally suited to such a concept and NRRI is exploring the possibilities. In addition, for existing coal-based power plants near deep water locations, the repurposing of the electrical facilities may be possible by conversion of the facility to a compressed air energy storage facility using the hybrid CAES concept.