The 10,000 miles of underground tunnels beneath Butte have filled with water since the closure of the Berkeley Pit and, in 1982, the shut-off of groundwater pumps that had dewatered the underground in the past. These waters are typically regarded as a liability, but a new project at Montana Tech is viewing the watery mines of Butte as a potential asset.
American Recovery and Reinvestment Act of 2009 to develop a demonstration system for capturing geothermal energy from mine waters beneath Butte. The demonstration will involve the installation of a heat-pump system in Tech’s new Natural Resources Building. The system will provide geothermally-based climate control for the building, illustrating the feasibility of using mine waters in heat-pump systems.
The project utilizes some of the advantages of mine waters compared to other sources of groundwater. Easy access to mine waters already exists in the form of mine shafts, saving the costs of drilling wells. Butte mine waters are also unusually warm; the mine waters used in this project are consistently 78°F (25°C). Additionally, it takes a lot of water to fill 10,000 miles of tunnel, so there is plenty available for geothermal applications.
Estimates show that heating costs for the Natural Resources Building could be cut by more than half by preheating incoming air with mine waters. By reducing energy needs that would traditionally be met by burning fossil fuels, the project has the added benefit of promoting environmental sustainability by reducing emissions. The concept could also be extended to other regions where warm geothermal waters exist. In mining communities that lie in warmer climates than Butte, cooler mine waters could be used similarly, but for cooling rather than heating. The project is currently in its early phases. After a feasibility study is completed this year, if all goes as planned, construction could begin in 2011. If successful, the project could be applied to buildings throughout Butte.