Modelling the performance of heat pump systems for single-family house applications

Abstract: Ground source heat pumps (GSHP) extracting the heat through borehole heat exchangers (BHEs) are an extremely efficient way to provide heating. Their performance is affected by the temperature of the thermal source: the ground; the higher it is the temperature of the ground, the higher their performance. As the demand of this heating technology increases, the amount of GSHP in densely populated areas is at risk of escalating notably. Consequently the study of thermal influence between neighbouring GSHPs is of paramount importance to properly design these systems in such areas. A comparison is made between the performance of an isolated house, and the same house as part of an area with high density of houses using identical GSHPs. The aim of the project is to study the long term consequences of exploiting the ground thermal source in an extensive manner, to analyse how the GSHP operation is affected in this specific case study, and present a methodology general enough to be implemented for different conditions. It is presented a methodology based on a parameter calibration model for the HP to analyse the performance along the years of a ground source heat pump system located in an area where there is a high density of identical installations. The model was tested to verify its accuracy when simulating the performance of the HP and was implemented for two case studies that emulate the conditions found in Sweden for residential heating. For the first case study, where a 6kW HP unit is simulated, the COP of the system decreased around 15% for the 25 studied years. In good agreement with this decline of the COP, an electricity consumption increase above 10% is faced. For the second case study, a heat pump unit double the size of the one employed for the first case is modelled. In this case, the drop for the COP is 16% and the electricity consumption growth is above 20%.