Water trapped in abandoned mine tunnels could be used in a geothermal system efficiently and with minimal emissions. That could lower energy costs, support new development, and attract business. Water trapped underground in the mines is cooler in summer and warmer in winter than the temperature above ground. Taking advantage of that temperature difference, heat pumps could use the water from the mines to provide heating and cooling to buildings.
news.uvic.ca/2025/clean-energy-found-in-old-coal-mines/