Hybrid ground source heat pump system capable of year‐round heating and its application in liquid natural gas vaporization

Abstract

One of the challenges in using a ground source heat pump (GSHP) system is the long-term increase or decrease in underground temperature due to an imbalance between heat extraction and injection. To eliminate this imbalance, we proposed a hybrid GSHP (HGSHP) system combined with air–water heat exchangers (AWHEs) capable of year-round heating and applied it to the hot water supply for liquid natural gas (LNG) vaporization in a satellite station. In this paper, the authors demonstrate the year-round heating capability of the HGSHP system and the energy conservation benefits of installing the HGSHP system for LNG vaporization. First, a field experimental apparatus was constructed for a gas vaporization system with the HGSHP; thereafter, an experimental proof of gas vaporization was obtained. The experimental results showed that it was possible to stably vaporize liquid nitrogen that was used instead of LNG by supplying hot water at 25°C. Additionally, in the gas vaporization experiment with the HGSHP system in the summer season, the SCOP measured was over ten. A calculation model for the AWHE was then established using the field test data; thereafter, a simulation tool for the HGSHP system was developed by combining it with one for the GSHP system. The simulation results indicated that the average surface temperature of all GHEs in the HGSHP system decreases from first year to second year. However, the average surface temperature of all GHEs stabilizes at a reduced level after the third year. These results indicate that the HGSHP system can operate long-term for year-round heating because the average surface temperature stabilize in the long-term.