Numerical Model for the Capacity Evaluation of Shallow Groundwater Heat Pumps in Beijing Plain, China

摘要

The groundwater heat pump (GWHP) system utilizes groundwater as alternative renewable and clean energy source for space heating and cooling, which is an open-loop system that withdraws water from a production well, passes it through a heat exchanger and discharges the water into an injection well. By utilizing the relatively stable temperature of groundwater, GWHP system can work with a higher coefficient of performance. It is necessary to evaluate the aquifer capacity for the proper design and application of GWHP. In this paper, a numerical method of underground heat transfer, energy balance method and thermal storage method were presented to calculate the load capacity of a unit area of shallow aquifer. The model results indicate that the numerical method, which is based on performance efficiency of groundwater heat pump, reflects the behavior of groundwater pumping and recharging processes, and better than energy balance method and thermal storage method, additionally it has the advantages of energy saving and environmental protect. The capacity is positively related to aquifer thickness. The final results show that it is easy for ground water recharging in alluvial and pluvial fan located at the piedmont, while load capacity is relatively smaller. In contrast, it is difficult for groundwater recharging in south-east plain where a larger load capacity is obtained.