Energy diaphragm walls for Turin metro: The increasing need for renewable sources of energy for heating and cooling of buildings and infrastructures makes energy geostructures an innovative and interesting technology, which is rapidly spreading all around the world. The application of this technology to section 1 of the Line 2 of Metro Torino (Italy), currently under design, is here investigated. The objective is to quantify, by means of Finite Element Thermo-Hydraulic simulations, the heat that could be extracted from and injected into the ground by the geothermal activation of the diaphragm walls and base slab of the tunnels.