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Pumped Hydro Energy Storage Final Report

November 5, 2011

Final Report: Pumped Hydro Energy Storage (PHES) Using Abandoned Mine Pits on the Mesabi Iron Range of Minnesota, November 2011

The report should provide a good background to next stage detailed evaluations.

Executive Summary

This study was commissioned to provide a first cut analysis of the potential for implementing Pump Hydro Energy Storage (PHES) using various water resources that exist on the Mesabi Iron Range (MIR) in Northeastern, MN. Energy storage is viewed as a critical enabler for continued adoption of intermittent power resources from wind and solar energy sources. An analysis team was established to study the possibilities of using this technology and for determining potential sites that could be studied in more detail to confirm the engineering feasibility for selected sites.

This study does not provide the necessary detail to fully evaluate the full capital and operating costs for implementation of the technology on the MIR. It provides a context for the parameters that must be part of an engineering feasibility study and provides necessary policy and environmental guidance for key issues and parameter that must be resolved in any future implementation scenario. The report should provide a good background to next stage detailed evaluations, and, in addition, the information developed by the team should be useful in evaluating the conditions for various sites that have been studied from a geotechnical perspective during the course of this investigation.   

This report provides specific information on the necessary requirements for siting a Pumped Hydro Energy Storage facility on the Mesabi Iron Range in northeastern Minnesota: • physical (site locations, amount of hydraulic head, reservoir size; geological, geotechnical);

  • mechanical (turbine size and other engineering requirements);  
  • environmental (groundwater flow, draw‐down zone, stakeholder views, laws and regulations, and water quality); and
  • policy (stakeholder views, current state and federal regulations, e.g., FERC, and electrical grid economics and policies).

All of the above data were evaluated by the by four qualified teams (Geotechnical, Facilities, Policy, and Environmental) from the: • Natural Resources Research Institute, University of Minnesota Duluth; • Department of Civil Engineering, University of Minnesota Duluth; • St. Anthony Fall Laboratory, University of Minnesota, Minneapolis; • Great River Energy; Maple Grove, MN; • Minnesota Power, Duluth, MN; and • In consultation with Barr Engineering.

In Chapter 2, the teams evaluated 18 of 45 sites within 17 geographical areas along the 110 mile length of the Mesabi Iron Range (MIR). Various site evaluation criteria were developed from relating 48 geographical information system (GIS) coverages that included physical constraints input from the Facilities Team that defined:

  • the amount of hydraulic head required (≥350ft.);
  • the minimum area of the lower reservoir (40 acres);
  • the area of the upper reservoir at 80 acres; and
  • water fluctuation in either reservoir could be no more than 15% (7.5% down or 7.5% up). xix

Using the above criteria to limit site selection, 12 additional “fatal flaw” criteria were used to rank the sites:  

  • Were the sites adjacent to current mining/blasting?;
  • Were faults/fractures present?;
  • Might water quality/hydrology be affected?;
  • Are there land acquisition problems, i.e., surface vs. mineral rights?;
  • Are there environmental concerns;
  • Is there local construction material available;
  • Are there site costs (infrastructure, etc.) that could be a problem?;
  • Are there possible regulatory issues?;
  • Are there safety issues related to a given site?;
  • Is there the potential for underground mining;
  • Are there existing upper and lower basins already available?; and
  • Are there existing underground mines?

Additionally, there are many other factors that can impact a “go” “no go” decision. For example, there are mineral rights to be considered, how long mining/blasting will go on in a specific area, other engineering concerns (water leakage/control, insulation of the entire PHES facility from future mining and blasting activities, and other environmental concerns (wetland destruction and replacements, multiple drainage systems, etc.), which also affect regulatory and policy issues, and Native American Treaty concerns.

The site evaluations also included the seven Barr Engineering PHES sites, i.e., Hill Annex, Keewatin, Hull Rust, Buhl, Missabe Mountain, Giants Ridge, and Hoyt Lakes‐Babbitt (Barr Engineering, 2010). Ten PHES scenarios were considered when evaluating the various sites:

1. Existing Pit Upper Reservoir to Existing Pit Lower Reservoir;

2. Existing Tailings Pond Upper Reservoir to Existing Pit Lower Reservoir;

3. Constructed Upper Reservoir to Existing Pit Lower Reservoir;

4. Constructed Upper Reservoir in Stockpile to Existing Pit Lower Reservoir;

5. Constructed Upper Reservoir to Existing Tailings Pond Lower Reservoir;

6. Constructed Upper Reservoir to Constructed Lower Reservoir;

7. Existing Pit Upper Reservoir to Excavated/Mined Underground Lower Reservoir;

8. Existing Tailings Pond Upper Reservoir to Excavated/Mined Underground Lower Reservoir;

9. Constructed Upper Reservoir in Tailings Basin to Excavated/Mined Underground Lower Reservoir; and

10. Existing Pit Upper Reservoir to Existing Underground Mine Lower Reservoir.

Read and download the full report: PDF iconPumpedHydroFullReport.