Geological and mining factors influencing further use of abandoned coal mines – A multi-disciplinary workflow towards sustainable underground storage
Elisa Colas, Peter A. Kukla, Florian Amann, Stefan Back
Abstract
The repurposing of abandoned coal mines in Europe presents significant opportunities and challenges for sustainable underground spatial utilization, particularly for energy storage solutions. This study focuses on the geological and mining factors influencing the feasibility of converting these abandoned coal mines into underground storage reservoirs. The study explores various repurposing scenarios, including use as a lower reservoir for an Underground Pumped Storage Hydropower (UPSH) plant, a reservoir for Compressed Air Energy Storage (CAES), heat storage, or geothermal energy. The initial conditions of coal mines, characterized by heterogeneous rock mass properties and unfavourable permeability, present significant challenges to ensure long-term stability and suitability for reuse after closure. This study uses the Prosper-Haniel hard-coal mine in North Rhine-Westphalia, Germany as a case study for developing a comprehensive 3D geological model that integrates and visualizes stratigraphy, tectonic structures, and mining data. The 3D model can be readily used as a tool for informed decision-making by offering a detailed overview of available geological background data before further exploration. Based on the literature, scenario opportunities and challenges for UPSH, CAES, heat storage and geothermal production are evaluated from a geological perspective, and key requirements for each application are outlined. A decision tree is proposed to guide the decision-making process, considering the stability of the reservoir, plant efficiency, and compliance with local environmental and safety regulations. The integration of geological and mining data in the Prosper-Haniel subsurface provided a comprehensive assessment of the potential geological conditions of abandoned mines. The paper discusses and identifies key geological and mining datasets essential for conducting feasibility studies for UPSH, CAES, heat storage and geothermal production. The research underscores the necessity of interdisciplinary collaboration, advanced data analytics, and detailed cost-benefit analyses to fully harness the potential of abandoned coal mines as sustainable energy storage solutions. This study's findings contribute to the broader understanding of the complex interplay between geological conditions and the practical aspects of repurposing abandoned coal mines, aiming to support the transition towards a more resilient and sustainable energy infrastructure. • Abandoned coal mines in Europe offer potential for sustainable energy storage, including underground pumped storage power plants. • The initial conditions of these mines, with heterogeneous rock masses and low permeability, pose challenges for stability and tightness. • The research examines Germany's Prosper-Haniel coal mine, focusing on geology, mining factors, and a 3D model to visualize its repurposing. • The findings guide authorities and stakeholders, aiding decisions and supporting a transition to resilient, sustainable energy infrastructure.