Performance Analysis And Optimization Of FCV Based On HT-PEMFC

With the global energy crisis and environmental pollution continuing to intensify,new energy vehicles are receiving more and more attention and research because of its advantages of zero emissions and low energy consumption.As an important carrier of hydrogen energy utilization,the fuel cell has the advantages of high energy density,zero-emission,high efficiency and high adaptability,and has a good development prospect in new energy vehicles.At present,the type of fuel cell used in fuel cell vehicle(FCV)is usually a low-temperature proton exchange membrane fuel cell(LT-PEMFC).Compared with the LT-PEMFC operating temperature of 40-100 °C,the high-temperature proton exchange membrane fuel cell(HT-PEMFC)with an operating temperature of 120-180 °C has better carbon monoxide tolerance,simpler water and heat management,faster electrode reaction kinetics,and higher quality waste heat.In this paper,according to the dynamics requirements of FCV,a vehicle power system based on HT-PEMFC is designed,and the dynamics and economy of FCV with the application of the HT-PEMFC system are simulated and studied.The main research and conclusions of this paper are as follows:(1)Based on the internal mechanism and reaction process of HT-PEMFC,an irreversible thermodynamic model of HT-PEMFC single cell is established.Combined with the current research models on the internal irreversibility of HT-PEMFC,finite-time thermodynamic evaluation indexes such as the power density,energy efficiency,exergy efficiency,environmental destruction factor,exergetic sustainability index and ecological coefficient of performance are derived.The results show that increasing the operating temperature,hydrogen pressure,oxygen pressure and relative humidity is beneficial to reduce the exergy destruction factor and environmental destruction index of HT-PEMFC single cell,thus improving the HT-PEMFC single cell output power,efficiency,exergetic sustainability index and ecological coefficient of performance.(2)According to the dynamic requirements of FCV,the HT-PEMFC concept system for vehicles is proposed,which includes the Methanol Steam Reforming(MSR)subsystem for hydrogen supply and the Organic Rankine Cycle(ORC)subsystem for recovering the waste heat from the power stack to generate power.The number of single cells in fuel cell stacks is determined based on the proposed irreversible thermodynamic model of a HT-PEMFC single cell;Simulation studies of the MSR subsystem showed that the methanol conversion and hydrogen yield to equilibrium improved with increasing reaction temperature and the molar ratio of water to methanol;The effect of different organic working fluids on the performance of the ORC subsystem is studied,and R245 fa is preferably selected as the organic working fluids of the system.(3)An evaluation model of the thermodynamic,economic and environmental performance of the vehicular HT-PEMFCC concept system is developed,and the effects of the main fuel cell operating parameters(current density,operating temperature,inlet pressure and inlet stoichiometry)on the system performance are studied.The results show that the net output power of the system is higher in the high current density range,but the levelized energy cost of the system and the carbon mass specific emissions of the system will be relatively higher.Higher operating temperatures and anode pressures are favorable to the system performance output.The increase of cathode pressure,cathode stoichiometry and anode stoichiometry will reduce the output power of the system.Therefore,on the basis of ensuring sufficient gas reaction in the fuel cell stack,the cathode pressure and inlet gas stoichiometry should be decreased as much as possible to reduce the power consumption of the ancillary equipment and improve the system performance.In addition,the HTPEMFC system is optimized using the NSGA-II algorithm,and the Pareto optimal curve and the optimal set of operating parameters are obtained.Compared to the unoptimized system,the net system output at point C(the final optimum point)is increased by 11.94 k W,and the levelized cost of energy and carbon mass specific emission are reduced by 6.47% and 6.10%,respectively.(4)According to the FCV configuration and power performance requirements of this paper,the key components of the power system are selected and the parameters are matched.The FCV model is built in ADVISOR software,and the output performance of the proposed HT-PEMFC system is imported into the vehicle model.According to the operation conditions and usage scenarios of FCV,the power following control strategy and four driving cycle conditions are selected for simulation testing.The simulation results show that the FCV model based on HT-PEMFC meets the power performance requirements.In addition,the optimized HT-PEMFC is used in the hybrid drive mode to show better dynamics and economy under different driving cycle conditions.When the fuel cell is driven alone,the optimized HT-PEMFC system consumes the least amount of hydrogen in four drive cycle conditions.In summary,this paper presents a conceptual system based on HT-PEMFC for automotive applications from the thermodynamic model of HT-PEMFC single cell.Parametric analysis and performance optimization of the system thermodynamic model are performed to obtain key operating parameters that are beneficial to the system performance output.The simulation results show that the adjustment of HT-PEMFC system structure layout and the optimization of system operation parameters can effectively improve the fuel cell system output performance,thus enhancing the dynamics and economy of FCV.The research thinking and method can provide certain references for future research related to FCV performance optimization.