A Comparative Study On Energy Consuming Of Hybrid Ground-source Heat Pump Systems

Ground Source Heat Pump System (GSHPS) is drawing more and more attention for its environmental-friendly and energy saving. After the hybrid ground-source heat pump system (HGSHPS) was brought up, it broke the application limitation of conventional GSHPS. The HGSHPS is divided into two kinds: one is the cooling tower cooling-assisted ground source heat pump system (CAGSHPS), the other is the solar-assisted ground source heat pump system (SAGSHPS). The CAGSHPS is used in the regions where the cooling load plays a dominant role, such as hot summer and cold winter regions, the SAGSHPS is mostly used in cold northern regions. However, in areas with hot summer and cold winter, the SAGSHPS can save more energy in winter than it runs in summer. Further researches about the energy-saving potential of SAGSHPS in winter should be carried.In this paper, aiming at Wuhan a new system named heating priority hybrid ground-source heat pump system (HPHGSHPS) is put forward. The system's running mode can be described as: in summer, cooling tower is used as the system's auxiliary cooling source; in autumn and winter, heat from solar energy collector is saved in underground soil; in spring, cooling tower is used to decrease the underground soil temperature .This mode can enhance heat exchange between underground heat exchanger and underground soil in winter and it also can guarantee heat exchange between underground heat exchanger and underground soil in summer. In this paper, simulations about HPHGSHPS and CAGSHPS running two years are conducted. And as a comparison, simulation about traditional air-conditioning system running a summer season is conducted. Based on the simulation dates, the energy consumption of the two hybrid ground-source heat pump systems is analyzed. The corresponding temperature distribution in underground soil is also presented. The main conclusions are summed as follows:(1) In summer, the HGSHPS is more energy efficient than the traditional air-conditioning system which use cooling tower as cooling source.(2) The heat unbalance eases in some degree when use the cooling-assisted system, and the HPHGSHPS aggravates the heat unbalance in underground soil. (3) In winter, the HPHGSHPS can save energy for 28.6% compared to the CAGSHPS 's energy consumption. However, the HPHGSHPS consumes more energy than the CAGSHPS in summer. Therefore, the annual energy-saving effect of the HPHGSHPS is not obvious. For better energy-saving, the heat balance in underground soil must be taken into consideration and it is necessary to optimize the on-off control of cooling tower or solar energy collector according to the climate and system's efficiency.