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

Abstract

This project focuses on developing an energy storage capability within Minnesota that will enable a larger build‐out of variable renewable generation sources. Currently, a significant challenge associated with the predominant renewable resource in our region (wind) is the variable and off‐peak nature of the energy generated. This feature of some renewable generation systems can, unfortunately, cause: (1) the need to build new fossil fuel generating facilities; (2) operation of existing fossil fuel generating facilities at inefficient levels; (3) transmission grid instability and unreliability; and (4) higher electricity rates. Energy storage is key to overcoming these problems. Currently, the only viable means of storing energy on a large scale are through pumped hydro energy storage (PHES), compressed air storage systems or liquid sodium sulfide battery systems. Fortunately, Minnesota has a unique and largely untapped resource for PHES in the form of idled taconite mines on the Mesabi Iron Range. The goal of this research project was to determine the potential viability, environmental sustainability and societal benefits of PHES as a vital, enabling technology for wind turbine‐based power generation. The intent of this research is to provide a clear roadmap for PHES development in Minnesota. The project is multifaceted and draws resources across the University System and from key industrial partners: Great River Energy and Minnesota Power. The results from the project provide vital information to decision makers on the potential of PHES and give guidance on how the technology can be implemented using the unique assets of the Minnesota Iron Ranges so that renewable mandates and green house gas reduction can be effectively accomplished. The results show that the topography and water resources exist at various sites that could allow a 100 to 200 MW facility to be constructed if the overall economic, mineral rights, and environmental issues associated with a given site can be properly managed. The report delves into the possibilities and outlines selection criteria that can be used for site selection. Other information is developed to compare the potential economic impact of implementation of the project within the constraints of the factors that can be monetized using the current policy environment. Finally, potential life cycle, regulatory, environmental, and permitting issues that are associated with implementation of the concept are discussed.