A study of the effects of four cont

A study of the effects of four controlling and operating parameters on dynamic gas supply during the load-up process for a PEM fuel cell is presented based on experimental data. The dynamic behaviors of current output and voltage responses are observed and transient gas supply, even starvation in the flow field is analyzed. The results indicate that increasing the amplitude of load-up would both improve concentration over-potential and the possibility of gas starvations in channels when a constant flow rate has been set for the cathode. A higher load-up rate provides a longer sustaining period of the aiming current as gas starvation takes place, but brings about an increase of the concentration over-potentials of cell voltages while no starvations appear. With a higher operating pressure, the dynamic performance could be improved and gas starvations are also relieved under an insufficient gas supply during the load-up process. The possibility of gas starvation and the concentration over-potential during the load-up process both decrease with the initial current level increasing while the same current step changing amplitude is applied and constant cathode stoichiometric ratios are fixed. All the rules of dynamic electric performance and gas supply during load-up process deduced from the experiments will be helpful for optimizing the controlling and operating strategies of PEM fuel cells on vehicles.