1. How a thermal geostructure works

1.1 Principles

Thermal geostructures are geotechnical structures (e.g. foundation piles, retaining structures, tunnels, etc.) which primarily perform a mechanical function. Equipped with heat exchanger tubes, these structures can also exchange energy with the surrounding environment to produce heating in winter and cooling in summer, via a geothermal heat pump (PACg) (figure 1 ). In some cases, particularly in early summer, a heat pump is not required, and the term freecooling is used.