Geothermal heat recovery from abandoned mines: a systematic review of projects implemented worldwide and a methodology for screening new projects

Due to the increasing energy demand worldwide and the resulting rising costs of conventional fuels, alternative energy sources could play a significant role towards global energy sustainability. Geothermal near-surface systems based on heat pumps have already proved to be a feasible option for the heating and cooling of buildings, while offering low CO₂ footprint. In this study, the concept of using abandoned mines for geothermal heat recovery with either closed- or open-loop configurations is systematically reviewed based on 18 projects worldwide. Key engineering parameters such as temperature on depth, circulation flow rate, mine water quality, and end-users’ location and demand have been used to characterize and classify the different projects. The study shows that the projects significantly differ from one another, thus highlighting the attractive versatility of this geothermal concept. A key outcome of this work is the development of a systematic procedure to evaluate future projects, followed by an example of a preliminary system design for a synthetic case scenario in the Harz region in Germany. After China’s energy administration’s recent announcement that the country will close 1,725 small-scale coal mines over the course of 2014 and considering the alarming levels of air pollution in the country, the concept of geothermal heat recovery from abandoned mines could become even more significant in the near future.