Simulation of ground-coupled heat pump systems using a spectral approach

This paper presents a method using a spectral approach to simulate a hybrid ground-coupled heat pump system. At each time step, the algorithm computes the ground load based on the building load, the coefficient of performance and the capacity of the heat pumps (which are a function of the fluid temperature), and the equivalent borehole thermal resistance. To capture the nonlinearity between the fluid temperature and the ground load, an iterative process is used. Results show that the proposed method is efficient in predicting the number of operating heat pumps required to ensure that the fluid temperature always remains between the heat pumps operational temperature limits and that the total energy provided to the building never exceeds the total capacity of the heat pumps. The approach used solves the entire simulation duration in a single step. In the present case, an hourly simulation over a ten-year period is completed in less than 10 seconds.