Thermal use of groundwater in Chur (Switzerland).

The city of Chur, in Switzerland, wants to evaluate the potential of the aquifer for heating and cooling purposes. Nowadays, 14 open systems (i.e., groundwater-source heat pumps) and 125 closed systems (ground-source heat pumps) operate in the area. Overall, 5.7 MW are extracted. Main questions are: “What’s the current status of the aquifer?”, “How vulnerable to new concessions is it?” and “Is the use of groundwater for heating and cooling purposes sustainable?”

To answer these questions, TK Consult AG has developed a transient, density-driven 3D hydrothermal model (see figure above). We have evaluated the current status by simulating first the “natural state” of the aquifer, i.e., in the absence of heat pumping and, second, the “forced state”, in the presence of heat pumps. The difference between the corresponding outputs is the thermal drawdown caused by the thermal use of groundwater.