Numerical Investigation of Intermittent Soil Precooling Operation Strategies for Ground Source Heat Pumps in Winter

To investigate the effects of intermittent pump operation on soil precooling performance and relative circulation pump energy consumption (pump operating time is used as a proxy since identical pumps are adopted across all cases), a numerical model based on one-dimensional transient heat conduction theory is established. The simulation consists of a 130-day precooling phase followed by a 90-day natural recovery period. Four cases with different pump on-time ratios are compared to reveal the variation trends of soil cooling effect and circulation pump energy consumption. The results show that a higher daily pump on-time ratio can effectively improve soil precooling performance, yet it brings increased pump energy consumption with obvious diminishing marginal benefit. High on-time ratio cases achieve superior cooling performance but low energy efficiency, while low on-time ratio cases reduce pump energy consumption but lead to insufficient soil precooling and limited cold storage capacity. No universally optimal ratio exists. Suitable cases can be flexibly selected according to practical cold-storage demand and energy-consumption constraints. This study provides a theoretical reference for the design of intermittent soil precooling schemes.