Novel management strategies for optimizing shallow geothermal energy exploitation: A European urban experience perspective

The intensive exploitation of urban aquifers by shallow geothermal systems can affect the thermal balance of urban aquifers, thus reducing their renewability. This paper proposes a new management strategy for the sustainable use of shallow geothermal energy resources, based on imposing new constraints related to system exploitation regimes. To achieve this objective, a novel methodology was introduced for optimizing the operation of geothermal systems, by adjusting the flow rate and/or temperature change to maintain the existing thermal energy demand. The methodology was applied to a 1.8 million real operational data set from 24 shallow groundwater heat pump systems (GWHP), which are large and medium scale systems. The investigated GWHPs are located in five European cities. Two management alternatives for the optimization of geothermal energy resources use are presented in this work: (1) prioritizing higher flow rates over lower temperature changes, which tended to relatively decrease the discharge temperature by 1.48 degrees C on average, and (2) prioritizing higher temperature changes over lower flow rates, which tended to relatively decrease flow rates down to 8.09 L s-1 on average. The results show that GWHPs operating in European cities with the highest thermal power demand and flow rates achieved the highest flow rate reduction.