Optimization of geothermal energy utilization by upscaling thermo-hydro-visco-mechanical soil processes

• Applicant: Dr.-Ing. Merita Tafili
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549595908

The global promotion of renewable energy aims to replace fossil fuels and reduce carbon dioxide emissions. With climate change, population growth, and increasing living standards, the demand for heating, cooling, and dehumidification continues to rise, leading to an increase in global energy needs. The increased demand for environmentally friendly energy has amplified interest in geothermal energy, a clean energy source abundant in the subsurface. Geothermal energy is increasingly being utilized through underground structures such as tunnels and diaphragm walls, with its integration into district heating networks proving particularly attractive. In contrast to other European countries, the potential of geothermal energy in Germany has long been underestimated. However, studies indicate that Germany's entire heat supply could be guaranteed by targeted utilization of domestic geothermal resources. Enhancing the ability to forecast the environmental consequences of utilizing shallow geothermal energy is crucial for optimizing its efficient use. Advanced numerical simulations, incorporating sophisticated models such as multiscale modelling techniques, are essential for this endeavour, especially in adequately capturing micromechanical processes. The objective of the proposed Emmy-Noether group is to develop a multiscale modelling technique for fine-grained soils under geothermal loading. A thermodynamically consistent constitutive model based on Granular Solid Hydrodynamic (GSH) theory will be developed and integrated into numerical prediction models. This hierarchical constitutive model will address the behaviour of fine-grained soils at the mesoscale under both monotonic and cyclic mechanical and thermal loads, as well as rate dependency. Realistic particle shapes and cohesive contact forces will be incorporated into Discrete Element Method (DEM) simulations to realistically simulate particle interactions at the microscale and quantify relevant micromechanical processes under thermo-hydro-mechanical loading. Insights from DEM investigations, including granular entropy and elastic potential, will inform the constitutive model. Subsequently, the model will be implemented into the Finite Element programs numgeo and Abaqus to evaluate its predictive accuracy and robustness, enabling the simulation of geothermal energy systems and their surroundings at the macro level. Extensions of the open-licence program numgeo will be necessary to consider temperature degrees of freedom and heat flows. This multiscale modelling approach to thermo-visco-mechanical soil processes aims to enhance the cost-effectiveness of geothermal energy utilization and improve understanding of potential consequences of soil temperature changes resulting from geothermal utilization.

• DFG Programme: Emmy Noether Independent Junior Research Groups