Numerical and experimental investigation of geothermal integration into tunnels

© 2017 19th ICSMGE Secretariat. All rights reserved. Renewable geothermal energy can be harvested through Ground Heat Exchangers (GHEs) using almost any engineering structure that is in contact with the ground, such as tunnels. The integration of geothermal loops into tunnels leads to a substantially large ground volume made available for geothermal exchange. The aim of this paper is to model and evaluate the integration of geothermal loops into tunnels to heat and cool targeted spaces and to provide insights into the heat transfer mechanisms and potential thermal interactions with existing nearby GHEs. A new 3D model is developed and solved numerically to simulate the thermo-hydro processes in the ground and the geothermal tunnel lining using the finite element package COMSOL Multiphysics. Numerical results are then validated against measured data from the Fasanenhof Tunnel (Stuttgart, Germany), where two sections of the tunnel have been equipped with geothermal loops. The efficiency of the system is investigated under selected possible scenarios. Numerical results together with full-scale measured data indicate that geothermal tunnels shows potential to exploit the available geothermal energy in the ground allowing heating and cooling spaces such as nearby buildings and stations.