An investigation of the potential thermal energy of geothermal tunnels with focus on a case study in Stuttgart, Germany

© 2016 Taylor & Francis Group, London. Shallowsurface geothermal energy is an essential contribution to the base load of heating energy. The thermal activation of tunnels is an interesting alternative and an economically appropriate supplement of the present hybrid systems in the field of ground engineering. An essential difference between the tunnel absorber and structures such as activated piles and diaphragm wall elements is the use of heat fluxes from the earth, as well as from the inside of the tunnel. Due to this circumstance, the tunnel absorber is assigned to the group of the duo hybrid systems. The tunnel air temperature is essential for the heat flux inside the tunnel. Stuttgart Fasanenhof and Jenbach are two geothermal tunnel plants which have been delivering dependable measurement data of the subsoil temperature, the tunnel lining temperature and the tunnel air temperature since 2011. Based on the selected operation modes and case studies, the measurement results are analyzed and discussed. In addition, the possible geothermal potential of a geothermal tunnel plant is introduced.