Driving factors of the thermal efficiency of ground source heat pump systems with vertical boreholes in Chongqing by experiments

Abstract Over the past years, the technology of Ground-coupled Heat Pump (GCHP) has been utilized in many countries due to its capabilities in providing sustainable heating and cooling. Previous studies in this field have shown that the thermal efficiency of GCHP is closely related to the properties of soil. However, the way in which the system should operate to provide the highest possible energy efficiency considering the thermal characteristics of the soil, needs further investigation. Therefore, the aim of this research is to investigate the factors that influence the energy performance of heat pump system, and to identify the key factors that contribute to the high energy performance of the system. This has been achieved through a series of experimental studies and on-site monitoring and data analysis for GCHP with vertical ground source heat exchanger in Chongqing, China. A set of experiments were set up to assess the influence of variations in the fluid temperature entering the ground heat exchanger, buried depth and operation mode on the energy performance of the GCHP system. The outcomes of this study have shown that, the operation mode and the depth of buried tube have more influence than other factors, intermittent operation mode and 60 m buried tube depth are preferred to choose firstly. Higher inlet temperature, lower inflow velocity and casing/double-U type pipes will help to enhance the energy efficiency of GCHP.