Simulation of Borehole Thermal Energy Storage with the Haar Wavelet Method

English Abstract:

In recent years, use of borehole thermal energy storage systems has become more frequent as these systems allow a significant reduction of the overall energy consumption of buildings located in cold climates. To predict the performances of a system, assess the influence of regional groundwater flow on the thermal storage or simply predict the ground temperature for a given input heat load signal, numerical simulations are usually performed. In this work, a thermal resistance and capacity model is used to simulate a borehole thermal energy storage system under the effect of heat advection driven by regional groundwater flow. The resulting model is a stiff ordinary differential equation system which can present numerical challenges for conventional implicit multistep or Runge-Kutta solvers. To speed up the solution of the problem, the Haar wavelet method is used in conjunction with a multistep segmentation approach which recalculates the step size at each iteration based on the local truncation error estimation given by the Adams-Bashforth method. The method presented in this conference is compared with commercial stiff solvers. Current results indicate that the proposed method is efficient in terms of memory usage and is always 2 to 10 times faster than state-of-the-art solvers.