Building Interaction The Energy Balance

The goal of closed loop geothermal systems is to provide heating, cooling and domestic hot water for a building or a set of buildings. The demands can be combined or not: one application will favor heating only, another one mainly cooling, etc. In any case the energy demand is time and season dependent. The building relies on the geothermal system, which in turn extracts required calories from the ground through probes.

This demand is distributed over the total length of the buried probes. A thermal flow is then created in their surroundings. Its value depends on the length of the buried probes and on the thermal power actually required by the building.

The geological area around the probes is thus subjected to the geothermal flow on the one hand, and to the thermal flow created by the building on the other hand.

The balance between the geothermal flow and the building thermal flow determines the thermal stability of the ground. In case the thermal demand of the building is moderate the geothermal flow recharges probes environment. This provides the system with global stability. In case of imbalance, that is inadequate design of the installation (excessive demand by the building compared to the geothermal resource) the ground temperature may vary, either falling or (less frequently) rising. This imbalance may take several years.