Figure 1

Schematic representation of a GWHP thermogeological system. Groundwater at a certain temperature T 1 is pumped from an abstraction well or borehole, then led to a heat transfer unit to extract the energy, and finally re-injected back into the aquifer via an injection well. An equivalent amount of groundwater is re-injected into the aquifer to that pumped out of it; only the groundwater temperature changes by the factor ΔT (figure courtesy of Golder Associates (UK) Ltd.).