Stationary and non-stationary deconvolution to recover long-term transfer functions

Abstract

To design a ground heat exchanger, simulations are frequently used. One way to perform simulations is to use the well-known g-functions to obtain the ground temperature. These functions are usually obtained by analytical or numerical models, which limits the precision or takes long simulation time. Recent advances show that the short-term g-functions can also be retrieved by a deconvolution algorithm. However, the known deconvolution algorithm is only validated for a set of operating parameters and duration of less than 10 days. A first objective of this article is to demonstrate that longer g-functions can be retrieved with such an algorithm. Then, a second objective is to extend the application of the deconvolution to consider time varying operating parameters throughout a ground heat exchanger's operation. To achieve those objectives, the deconvolution will be first applied to various numerical year-long simulations of a ground source heat pump system with stationary conditions. Then, an extended multi-signal deconvolution will be applied to a non-stationary thermal response test of 30 days. Both tests show adequate temperature reconstruction with RMSE of less than 0.05 °C and 0.2 °C for the first and second scenarios respectively.