WorldWide Drilling Resource

30 SEPTEMBER 2015 WorldWide Drilling Resource ® Using Mine Water for Geothermal Systems Adapted from Information by Michigan Technological University There are millions of miles of old mining tunnels under mining communities across the United States. These abandoned tunnels are often viewed as a dangerous legacy, but the water in these mines could actually be a major geothermal resource. Student researchers at Michigan Technological University have put together the first comprehensive guidebook to help communities explore the possibility of using mine water for geothermal heating and cooling. Despite the great potential for this resource, there are less than 30 active mine water geothermal systems in the world. One of those systems is at Michigan Tech’s Keweenaw Research Center (KRC) just north of Houghton, Michigan. Michigan Tech graduate student Edward Louie spearheaded the project as part of his master’s degree work in energy policy. “With mine water, you can draw lots of heat from it without it cooling down.” The mine water in the Keweenaw stays around 53-55ºF (11-12ºC) year-round - temperatures ideal for a geothermal heating and cooling system. Deciding whether to use an open- or closed-loop geothermal system depends on the location and quality of the mine water. In the Keweenaw, where pure copper was mined, the water is relatively clean. In other areas, mine water containing heavy metals and acid can corrode equipment. So, Louie and his team outline several open- and closed-loop systems in the guidebook. Closed-loop systems help protect equipment from corrosive mine water by exchanging heat outside a loop of corrosion- resistant pipes placed inside the mineshaft. The mine water itself is never pumped. In open-loop systems, mine water is pumped through a metal heat exchanger. The advantage is increased efficiency and less piping, but the mine water has to be clean enough to not corrode the equipment. At KRC, mine water is piped from 300 feet below the surface and circulated through a heat exchanger. The mine water cools or heats a closed-loop system within the building. A water-glycol mixture circulates and runs through 18 heat pumps throughout the center’s main building. Jay Meldrum, director of the Keweenaw Research Center hopes to expand geothermal on the site and is planning a new, smaller system in a separate build- ing. “We hope to use geothermal as an educational resource,” he explained. “It’s also an area we want to continue doing research in.” With so few active systems, KRC is a unique resource for people in the area. Tapping into mine water is also a tribute to the area’s rich mining history, according to Richelle Winkler, a sociology and demography researcher at Michigan Tech who works with Louie and Meldrum. “Using the mine water for geothermal energy creates an opportunity to recast community identity,” Winkler stated, “which both celebrates the mining heritage and promotes progress forward in an environmentally sustainable way.” With so much room for expansion, the Keweenaw could become a hub for mine water geothermal. Through the guidebook, Louie, Winkler, and their collaborators could help shape a widespread environmental problem into a solution and resource.