a b s t r a c tTo promote the utilization of ground-source heat pumps, a new methodology to calculate the lowtemperature geothermal potential (LTGP) of a region is presented. The methodology is applicable worldwide, and it considers both closed-and open-loop systems. This new approximation for closedloops calculates the admissible heat flux exchange with the ground according to an analytical solution of the heat transport equation in porous media. Open-loop systems are calculated as a function of a sustainable removable water flux and the temperature difference between groundwater and a referenced external body. The automated calculation in the setting of a GIS platform has allowed the performance of multilayered 3D mapping of the low-temperature geothermal potential for both types of exploitations considering all of the available information. An example of the application of the methodology in the Metropolitan Area of Barcelona (Spain) is also presented. Finally, a finite element analysis has been performed to quantify the accuracy of the method and the influence of heat advection processes in the LTGP.
The long-term sustainability of shallow geothermal systems in dense urbanized areas can be potentially compromised by the existence of thermal interfaces. Thermal interferences between systems have to be avoided to prevent the loss of system performance. Nevertheless, in this work we provide evidence of a positive feedback from thermal interferences in certain controlled situations. Two real groundwater heat pump systems were investigated using real exploitation data sets to estimate the thermal energy demand bias and, by extrapolation, to assess the nature of thermal interferences between the systems. To do that, thermal interferences were modelled by means of a calibrated and validated 3D city-scale numerical model reproducing groundwater flow and heat transport. Results obtained showed a 39% (522 MWh·yr−1) energy imbalance towards cooling for one of the systems, which generated a hot thermal plume towards the downgradient and second system investigated. The nested system in the hot thermal plume only used groundwater for heating, thus establishing a positive symbiotic relationship between them. Considering the energy balance of both systems together, a reduced 9% imbalance was found, hence ensuring the long-term sustainability and renewability of the shallow geothermal resource exploited. The nested geothermal systems described illustrate the possibilities of a new management strategy in shallow geothermal energy governance.
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