Operation analysis and performance prediction for a GSHP system compounded with domestic hot water (DHW) system

• Performance of a GSHP system was monitored and analyzed.
• A TRNSYS model of the studied GSHP system was established and validated.
• Long-term performance of the GSHP system was predicted with the model.
• The system performance deterioration could be compensated by combining a DHW system.

A ground-source heat pump (GSHP) system located in Chongqing, a cooling dominated region in China, was taken as an experimental system. In order to explore the operating characteristics of the GSHP system, the GSHP system was monitored with a data acquisition system. The measured data were analyzed, including the inlet/outlet water temperatures, power consumptions, EER/COP and also the ground temperature variations. The measured system EER of 2013 and 2014 are 3.01 and 2.91, respectively, while the system COP of 2013 is 2.59. A TRNSYS model was established based on the studied GSHP system. The accuracy of the model was validated by the comparison between the measured and the simulated outlet water temperatures, and also the ground temperatures. The model was then used to predict the long-term performance of the GSHP system. It has been found that after 20-years running of the system, the heat accumulation under the ground and the deterioration of system efficiency aggravate: the ground temperature would rise up to 30.5 °C from the initial value of 20 °C, while the ASPF value would descend to 2.72 from the initial value of 3.12. As a remedy for the problem, the domestic hot water (DHW) system was supposed to be operated in the following years, and the simulation showed that the operation of DHW system could effectively reduce the ground temperature and improve the system performance.