Temperature fields induced by geothermal devices

Efficient and sustainable exploitation of low-enthalpy geothermal energy relies on accurate representations of heat transfer processes in the subsurface. An analytical model, which provides such a representation by predicting the dynamics of thermal fields induced by shallow GHEs (ground heat exchangers), is derived. The model accounts for atmospheric temperature fluctuations at the ground surface, an arbitrary geometry of GHEs operating in time-varying heating/cooling modes, and anisotropy and uncertain spatio-temporal variability of thermal conductivity of the ambient soil. To validate the model, its predictions of a thermal field generated by a shallow flat-panel GHEs are compared with experimental data. This comparison demonstrates the model's ability to provide accurate fit-free predictions of soil-temperature fields generated by GHEs. The analysis presented shows that a single horizontal GHE may affect soil temperature by several degrees at distances on the order of 1 m. The volume of influence is expressed in terms of soil thermal properties. Such modeling predictions are invaluable for screening of potential sites and optimal design of geothermal systems consisting of multiple GHEs.