Sensitivity analysis of proton exchange membrane fuel cells based on fixed frequency impedance

Abstract

Durability is a major constraint to the commercialization of proton exchange membrane fuel cells (PEMFC). An accurate evaluation of the internal state of the fuel cell is necessary to develop a reasonable control strategy. Impedance is one of the important parameters to characterize the internal state of the fuel cell. Making full use of the impedance parameter is of great importance to extend the fuel cell life. The internal sensitivity of the fuel cell is investigated when the reaction parameters are altered. The characteristic frequency is determined to be 2000Hz by the correspondence between the electrochemical impedance spectroscopy and the equivalent circuit model. This frequency is also where the ohmic internal resistance is located. At different current densities, the cooling water temperature and the air stoichiometric ratio are varied. By measuring the variation of the impedance, the change of state inside the stack can be known. The optimal external parameters of the stack reaction can be determined. This study has important implications for making full use of impedance as a characterization parameter and for more rational control of fuel cell systems. Fixed frequency impedance will play an auxiliary role in water and heat management.