Development and validation of a computationally efficient hybrid model for temporal high‐resolution simulations of geothermal bore fields

This paper presents a hybrid simulation approach for 1U-, 2U- and coaxial single, and field of, borehole heat exchangers. We implement a novel combination of existing solutions for the simulation of heat transfer processes within the borehole and the surrounding ground. The heat transfer in the ground is modelled with a combination of analytically determined g-functions, the borehole models utilize thermal resistance capacity models and the finite volume method. Critically, we improve the computational efficiency of long-term simulations by sub-dividing the time scale into multiple periods, where the influence of past periods on future periods is calculated using the fast Fourier transform (FFT). The accuracy and efficiency of the proposed method is validated against single borehole numerical models and a 40 bore field case study. The method achieves computational times reductions of over 90% in some cases, with greater improvement as the simulation time increases.