When the phreatic level allows it, the geothermal heat exchange between the probe and the ground takes place in an open system, from where water is extracted and reinjected into the aquifer (once the geothermal energy is removed/introduced). This reduces the cost of installation but requires the presence of a water well in the ground, as well as special permits from the competent authorities.
In this system, boreholes up to 150 m deep are drilled for the introduction of geothermal probes into the ground, thanks to which heat energy will be exchanged between the subsoil and the heat-carrying fluid present inside the probes.
In this case, shallow trenches (max. 15 meters) are dug in which heat is exchanged. This option requires a large area of land to carry out the transmission of geothermal energy for use in the air conditioning of the house.
This is the option par excellence if an architectural integration of geothermal energy with the home is to be achieved. It consists, in new construction buildings, in the introduction of heat collectors in the foundation piles, thus saving costs derived from the execution of additional boreholes exclusively for geothermal use.