Study on the Long-Term Performance and Efficiency of Single-Well Circulation Coupled Groundwater Heat Pump System Based on Field Test

Ke Zhu,Yifan Zeng,Xiaoxiu Liu,Qiang Wu,Kun Tu,Shengheng Xu

doi:10.3389/feart.2021.772977

Abstract

Although buildings are often heated and cooled by single-well circulation coupled groundwater heat pump systems, few studies have evaluated the long-term performance of these systems. Therefore, the present study investigated the performance of these systems by analyzing the efficiency and energy consumption using 4 years of operating data. The results indicate that the coefficient of performance (COP) of the system gradually decreases because of thermal breakthrough or an accumulation of cold. In addition, the sealing clapboards could effectively slow down thermal breakthrough. In addition, compared with the heating period, the COP of the heat pump unit (HPU) and system increases, and its energy consumption decreases in the cooling period. It was also found that partial heat loss occurs when water from the single-well circulation outlet penetrates the main pipeline. Moreover, the heat-exchange efficiency of a single HPU exceeds that of multiple HPUs, and the COP of a HPU decreases during operation with increasing indoor temperature. Accordingly, we improved the performance of system by increasing the underground heat storage. Herein, we focus on optimizing the system design during long-term operation, which includes taking steps such as lengthening the sealing clapboards, using insulated pipes, discharging the remaining water and adding intelligent control devices.

Highlights

In the context of the global energy and environmental crisis, groundwater heat-pump (GWHP) systems have been extensively implemented to use shallow geothermal energy sources for heating or cooling of residential and commercial buildings (Li et al, 2013)
We report on a 4 year field test of an single-well circulation (SWC) coupled GWHP system conducted in Beijing, China
Based on data measured over 4 years, we studied the factors that reduce the SWC system efficiency and increase energy consumption to evaluate the long-term performance of this

Summary

Introduction

In the context of the global energy and environmental crisis, groundwater heat-pump (GWHP) systems have been extensively implemented to use shallow geothermal energy sources for heating or cooling of residential and commercial buildings (Li et al, 2013). The lower pumping zone is filled with groundwater into which is placed a submersible pump connected to a suction pipe. Pumping groundwater exchanges heat via the heat-pump units (HPUs). The middle sealing zone contains clapboards to prevent the heat-exchanged groundwater from entering the pumping well. The system offers the advantages of lower initial investment and operational costs, a smaller footprint, and a diminished on groundwater quality (Song et al, 2019a), which has led to the wide use of these systems in practical engineering

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Results

Conclusion