Application of energy tunnels to an urban environment

Deep and shallow foundations, diaphragm walls, tunnel linings and anchors are being increasingly employed as energy geostructures in Europe and all around the world. Besides being constructed for their primary structural role, they are equipped to be able to exchange heat with the ground and supply thermal energy for heating and cooling of buildings and de-icing of infrastructures. This technology can play a fundamental role in the current challenge of addressing the increasing need for clean and renewable sources of energy. This paper investigates the possibility of thermal activation of a new section under construction of the Metro Torino line 1 (Italy) to heat and cool adjacent buildings. The design and optimization of the geothermal plant, the quantification of the exploitable heat and the assessment of the eventual consequences on the surrounding ground are here discussed. For this purpose, thermo-hydro finite element analyses, able to capture the key aspects of the problem, were conducted. A 3D model is devoted to study the efficiency of the system, reproducing one ring of the instrumented tunnel segmental lining, while a 2D large scale model of the Torino aquifer is conceived to investigate the sustainability of the technology in terms of effects on the surrounding environment. Based on the results of the computations, it can be anticipated that, thanks to the favorable underground water flow conditions in Torino, the system would allow 53 and 74 W per square meter of tunnel lining to be exchanged during winter and summer respectively.