The performance analysis of ground source heat pump using spiral coil energy piles with seepage in different climates of cold regions

Ground source heat pump (GSHP) is an energy saving and efficient air conditioning technology. Energy piles group is an economic and efficient ground heat exchanger of the system to extract heat in winter and inject heat in summer for space heating and cooling of the buildings. However, for heating dominant buildings in cold regions, the annual soil thermal imbalance causes the cold accumulation in soil and heating deficiency of the building. To simulate the system performance, the system model is established, involving the model of energy piles group with seepage, the heat pump model, the water pump model, and the building model. An office building is selected as the objective and applied in three typical cities (Harbin, Changchun, and Shenyang) of cold regions in China for simulation. The summer in Harbin, Changchun, and Shenyang is not hot. Harbin has the coldest winter and its minimum monthly average air temperature is -18.8ºC. The building loads in different cities are simulated by transient software. The maximum monthly heating loads are -120.91 MWh in Harbin, -111.91 MWh in Changchun and -98.63 MWh in Shenyang. The soil thermal condition, the COP of heat pump and heating effect in the buildings of different cities are analysed. In Harbin, Changchun and Shenyang, the annually accumulated soil heat extraction decreases from -314.06 MWh, -303.74 MWh and -247.15 MWh in the first year to -223.70 MWh, -226.97 MWh and -229.47 MWh in the tenth year; the minimum COP decreases from 2.61, 2.85 and 3.46 in the first year to 1.99, 2.13 and 2.88 in the tenth year; the maximum heating deficiency is 51.9 kW, 44.4kW and 4.9kW in the tenth year. This work contributes to the performance prediction of GSHP system using spiral coil energy pile in different climates of cold regions.