Thermal performance assessment of an energy lining for the Lyon-Turin base tunnel

The use of geothermal energy for heating and cooling purposes is an environmentallyfriendly and cost-effective alternative with the potential to replace fossil fuels and help to mitigate global warming as well. The paper illustrates the geothermal potential evaluation of a portion of the Lyon-Turin base tunnel considering the thermal activation of the tunnel concrete segmental lining. The international infrastructure will connect Italy to France, crossing the Alps and meeting uncommon climate conditions, reaching a peak temperature of 47  C, due to its significant rock overburden (up to 2500 m) under the Ambin massif. A thermo-hydraulic numerical model was used to simulate the heat exchange of the system and quantify the power achievable by thermally activating a 10 km-long section of the base tunnel. Sensitivity analyses were performed to investigate the influence of the heat carrier fluid and the air flow velocities as well as the inlet temperature on the heat exchange. Moreover, four different operational conditions were compared to allow for assessing the overall thermal performance of the energy lining in terms of heat exploited and of the capacity of cooling the tunnel.