Research On Optimal Control Method Of Air-source Heat Pump Air-conditioning System Based On Indoor Thermal Comfort

Air-source heat pump unit is widely used in small and medium-sized buildings as a kind of air conditioner with easy installation,low initial investment and high efficiency.Taking into account the cost,most of these units use fixed-frequency compressor,and cycle on and off depending on return water temperature to satisfy the building load.Due to frequent fluctuations in the water temperature during operation,how to give full play to the energy-saving potential of variable water temperature control is a worthy subject.In this paper,the air-source heat pump air-conditioning system of Sino-Italy green energy laboratory in Shanghai Jiaotong University is taken as the research object and a variable water temperature optimal control method based on indoor thermal comfort is proposed.The main work is as follows:The dynamic simulation model of the air-source heat pump air-conditioning system is established,including building model,air-source heat pump unit model,fan coil model and system control logic.The accuracy of the model is validated by the experimental data.The results show that the error of system simulation result is no more than 14%.Based on this model,the influence of the return water temperature on the energy consumption and indoor thermal comfort is studied.The results show that,in cooling condition,the system energy consumption decreases by 2.9%and the system COP increases by 2.55%with 1~oC increase of return water temperature.In heating condition,the system energy consumption decreases by 3.6%and the system COP increases by 2.4%with 1~oC decrease of return water temperature.However,with the decrease of energy consumption,PMV dissatisfaction rate increases significantly throughout the day.The calculation method of optimal return water temperature set point is put forward,and value is obtained in the whole year.The simulation results show that the use of the set point can ensure that the indoor PMV does not exceed 2%of the set value,while the annual energy consumption is 11%lower than the traditional control method.Based on the data of optimal return water temperature set point,a BP(Back Propagation)neural network model is established to predict the optimal return water temperature,and the prediction results of the neural network model are validated.The results show that the forecast error is no more than 10%.The optimized air-source heating pump air-conditioning system is applied to Chongqing,Wuhan and Shanghai.The annual system energy consumption and indoor thermal comfort are simulated.The results show that the indoor PMV in the whole year does not exceed 2%of set value,and the annual energy consumption of the three regions compared to traditional control methods were reduced by 10.6%,9.8%and 9.8%,which means significant energy savings.