Numerical study of an abandoned mine repurposed for CAES systems

Summary

Abstract

Balancing the supply and demand of energy is essential for ensuring grid stability and reducing dependence on fossil fuels. Among large-scale energy storage applications, Compressed Air Energy Storage (CAES) represents a promising solution due to its potential to integrate renewable sources efficiently. Repurposing existing underground infrastructure such as mine caverns, offers a cost-effective and less disruptive alternative compared to engineered cavities, taking advantage of pre-existing excavations characterized by high overburden and generally favourable rock mass conditions. However, besides these energy benefits, CAES implies a complex geotechnical challenge that requires an in-depth understanding of rock mass behaviour under cyclic loading. The potential reuse of underground spaces from a gold mine located in the Antioquia region, Colombia, is considered as a case study for CAES implementation. First, a brief review of CAES operating principles is presented, followed by a suitability assessment of the existing mine voids as storage reservoirs and the description of the mine’s extraction process, which conditioned the geometry and spatial distribution of the abandoned cavities. The rock mass is then characterized, and fatigue-induced degradation behaviour under cyclic loading is assessed to evaluate its influence on the mechanical response of the surrounding rock mass. A three-dimensional numerical model based on finite difference method is developed to simulate the geomechanical behavior of the rock mass under typical CAES operating conditions. The results suggest that the rock mass remains largely stable, with displacements reaching 2.81 mm and major principal stresses of 9.89 MPa, supporting the feasibility of CAES system in the abandoned underground mines investigated. This preliminary assessment does not account for coupled thermo-hydro-mechanical processes which may influence long-term system performance.