Hybrid Power-driven Heat Pump: Sizing Of Two Kinds Of Power And Operation Strategy

In order to improve the utilization efficiency of natural gas in building cooling and heating,a hybrid power heat pump(HPHP)system driven by gas engine and motor is proposed after analyzing the advantages and disadvantages of gas engine heat pump(GEHP).The prototype of HPHP is developed and its performance is tested and simulated.The design method and control strategy of HPHP is investigated and its adaptability in different climate and different kinds of buildings is investigated.The main contributions as follows:(1)A HPHP system driven by gas engine and motor is proposed by integrating the advantages of GEHP in heating and that of the electric heat pump(EHP)in cooling.There're two main configurations of HPHP system.One is the seasonal switching type in which the HPHP system runs gas engine in winter and electrical motor in summer respectively;the other is the combined driving type in which the HPHP system is driven by the gas engine or/and electrical motor according to the requirement and performance.The prototype of HPHP system driven by the combination of gas engine and motor is developed with mechanical transmission.The test indicates that the HPHP system can operate stably and efficiently.(2)The performance test platform of HPHP system is built,and the performance of gas engine,GEHP system and the HPHP system driven by both gas engine and motor under different rotational speed,evaporator inlet temperature and motor load rate are tested.A steady-state performance simulation model of HPHP system is established,and the accuracy of the simulation results is validated by the test data.(3)The design method of HPHP system which matches the design cooling and heating loads of the building is established,and the design method with minimum components of HPHP system and the extended selection method based on it are put forward.With the support of optimization control strategy,the optimal design of HPHP in Beijing is further obtained by performance simulation:the selection of refrigerant cycle is determined according to the EHP,and the rated output power of the gas engine accounts for 60% to 70% of the power requirement of the compressor under the design condition.(4)The indexes of the energy utilization efficiency and critical gaselectricity price ratio of the HPHP system are put forward,and the control strategy to achieve the lowest energy consumption and the lowest operation cost for the selected HPHP system is established.As for the adaptability of HPHP system in different areas and different kinds of buildings,the results show that the energy saving ratio of HPHP system in Shenyang is about 9% compared to EHP system and GEHP system,and the annual operation cost of HPHP system can be saved by more than 30% for commercial buildings with peak and off-peak electricity prices compared to the EHP system in Shenyang and GEHP system in Nanjing.According to the conclusions above,the HPHP system is a kind of equipment with great potential in energy saving and operation cost saving by flexible control strategy.It will play an important role in achieving clean heating and building energy efficiency in the future.