Numerical study based on one-year monitoring data of groundwater-source heat pumps primarily for heating: a case in Tangshan, China

Thermal breakthrough is the main factor that affects the long-term efficiency of groundwater heat pump systems that predominantly for heating, particularly in northern China. A large water-source heat pump engineering project in Tangshan, China, is examined in this study. The project involves 18 pumping wells with a yield of 80 m3/h and 40 injection wells, covering a total planning area of 445,000 m2. In the third year, a groundwater monitoring system is installed in 23 wells to monitor the groundwater temperature. A hydrothermal coupling numerical model is established with the non-isothermal multiphase migration software TOUGH2. The model is analyzed by applying it to simulations. Simulation results are validated through a comparison with monitoring data. Results of the 10-year operation simulation show that the A3 and A4 well groups experience severe cold accumulation. Three optimization scenarios are thus presented to improve the groundwater temperature. Simulation results show that using the aquifer thermal energy storage method could fully meet the future requirements of heating during winter; however, the cost of this method is high. The optimization effect of alternating the pumping and the injection wells is insignificant. Adopting different pumping and injection layers can effectively control the water temperature decrease in the pumping wells; however, the breakthrough of cold plume should be prevented. The results of this study could provide a reference for the numerical prediction of large-scale water-source heat pump engineering projects in northern China.