Borehole Systems Heat from Earth

Closed loop, geothermal probes based systems are attractive solutions to answer the thermal demands of buildings because it does not depend in principle on resources such as ground waters, and because it suits most soils.

Principle

A geothermal system based on a field of vertical probes uses the heat of the ground to feed a building (whether for heating or cooling). The temperature of the ground is normally stable, sustained by the geothermal flow coming from the earth center towards the surface.

Vertical probes consist of PEHD pipes inserted into bore holes drilled in the ground, at a depth ranging most commonly from 30 to 100 meters. Probes can be also integrated into the foundations of the building. These probes perform a thermal heat exchange between the ground and the heat carrying fluid. The latter circulates in a closed circuit and transports calories between the ground (via probes) and the building. Calories (or frigories) are then extracted from the fluid by heat pumps into the building.

The amount of heat that can be extracted through the probes depends on their size on one hand, and on the geologic, hydrogeologic and thermal characteristics of the ground on the other hand.