Quantifying the permissible technical groundwater heat pump potential and its uncertainty through aquifer clustering and spatial packing

Abstract Quantifying the permissible technical groundwater heat pump (GWHP) use potential is important for informing policy decisions. This study introduces a transferable and efficient methodology to quantify the permissible technical GWHP use potential and its uncertainty using existing hydrogeological data. The methodology is applied to the deep aquifer in the Baar-Zug-Steinhausen area (Canton of Zug, Switzerland). To address the computational demands of strategies based on 3D numerical groundwater flow and heat transport simulations, the aquifer is classified into distinct hydrogeological “clusters”. This clustering is based on key hydrogeological parameters such as aquifer thickness, permeability, and hydraulic gradient. For each cluster, groundwater flow and heat transport are simulated for a single GWHP doublet in 3D box models with homogeneous properties and a constant hydraulic gradient. Small, medium, and large demands, including both balanced and unbalanced energy load profiles are considered. Thermal and hydraulic influence zones are delineated using 0.1 K isotherms and Darcy flow deviation from natural conditions. A spatial packing algorithm is then applied to place the influence zones within their cluster such that they are aligned with hydraulic gradient direction and treating them as non-overlapping hard boundaries. The permissible technical GWHP use potential is defined by the total number of GWHPs that can be accommodated within each cluster without interference. Uncertainty on the permissible technical potential is quantified through additional simulations. This approach also underscores the importance of quantifying and communicating the range of possible permissible technical heat use potentials to stakeholders, guiding future development towards optimized and environmentally sound groundwater heat use.