Efficiency Analysis Of Air-ground Compound Source Heat Pump System

In the hot summer and cold winter area,the annual cooling load of the building is far greater than the heating load as a result of its specific climatic conditions.The long-time operation of single ground source heat pump system would lead to heat released to the soil is far greater than the heat from the soil.Thus,the soil temperature increased year by year,working conditions of heat pump continuously deteriorated,the heat pump unit's performance coefficient decreased,and affecting the normal operation of the air conditioning system.The advanced air-ground compound source heat pump system can solve the soil thermal imbalance problem caused by single operation of soil source heat pump,and the COP(coefficient of performance)is increased.As for the project investors,COP as well as economic effect is considered.This paper takes a villa construction in Changsha as an object,using TRNSYS to simulate annual energy consumption of the air-ground compound source heat pump system and a single ground source heat pump system under continuous operation and intermittent operation.The initial investment,operation and maintenance costs of each scheme are calculated,using the dynamic annual cost method to make economic analysis of several schemes.And in this paper,the initial investment,the life cycle and the base discount rate are selected as the sensitivity factors,to investigate the sensitivity of various factors of the scheme to the annual value of the cost.The result shows that the economic effect of the advanced air –ground composite source heat pump system is better than that of a single ground source heat pump system in both continuous operation and intermittent operation mode,and pay back period is 6.2 years and 7.8 years,respectively.For both of the systems,the economic benefit of continuous operation mode is better than intermittent operation.Based on the sensitivity analysis of systems,we could conclude the initial investment has a greatest impact,the benchmark discount rate is second and the life cycle has the least impact on the annual cost.Besides,the annual cost increases as the growth of the benchmark discount rate and investment,decreases with the growth of the life cycle.