Revitalizing underground mines: unlocking the potential of thermal energy storage (MineATES)

Thermal Energy Storage (TES) has gained prominence as a viable solution for storing surplus heat and cold underground. While traditional TES systems primarily rely on natural aquifers, an emerging approach known as ”Mine Thermal Energy Storage“ (MTES) has garnered attention for repurposing former underground mines. Despite the promise of TES in both Aquifer Thermal Energy Storage (ATES) and MTES, several operational challenges persist, including clogging, scaling, corrosion, and energy loss across system boundaries. These challenges impact not only the geological matrix but also the integrity of technical infrastructure components such as pipes and heat exchangers. The “MineATES” research and development project, funded by the German Federal Ministry of Education and Research (BMBF), investigates the feasibility and limitations of employing water-filled cavities in underground mines for TES. The study primarily focuses on the ”Reiche Zeche“ silver mine, designated as a teaching and research site at the TU Bergakademie Freiberg in Freiberg, Germany. An in-situ “real-laboratory” is established there with the purpose of simulating the periodically varying heat exchange between mine water - here stored in an experimental basin and slowly flowed through with acid precipitation water (pH ~ 2 - 3) - and the surrounding Freiberg Gneiss rock. Comprehensive monitoring of hydrochemical parameters and molecular biological analyses complement multiple heating and cooling cycles within the mine. Furthermore, laboratory-scale column flow experiments and batch reactor tests mimic TES cycles, heating columns up to 60 ⁰C and cooling them down to 10 ⁰C (Figure 1). Comparative investigations include rock materials and mine waters from two other mines in Saxony, namely a former tin ore mine in Ehrenfriedersdorf and a former hard coal mine in Lugau/Oelsnitz. The overarching goal of all experiments is to ascertain the nature, extent, and location of potential chemical alterations during TES operations.