A Simulation Study on a New Hybrid GCHP System in Hong Kong

Ground-coupled heat pump (GCHP) systems have gained popularity for space air-conditioning in buildings. A significant barrier to wider application of this technology in cooling-dominated buildings is the higher initial cost of ground heat exchanger (GHE) installation due to the imbalanced annual loads. The common alternative to reduce initial cost is the hybrid ground-coupled heat pump (HyGCHP) system with cooling tower. In this research, a new HyGCHP system with domestic hot water (DHW) supply was proposed. This system equipped with a desuperheater and an inclined GHE can supply space cooling and heating as well as DHW. The objective of the inclined boreholes is to reduce the land plot size required for the GHE installation in densely populated areas. A comprehensive simulation model has been developed including the inclined GHE and the heat pump. The simulation results show that the inclined boreholes can improve the heat transfer efficiency on the limited ground area compared to the vertical boreholes. The case study indicates that the HyGCHP system has higher energy performance efficiency than that of the conventional GCHP systems whilst it can significantly reduce the initial cost of the GHE installation due to more balanced annual heating and cooling loads of the GHE. The study also demonstrates that the HyGCHP with DHW supply is suitable to warm climates, like Hong Kong.