AC impedance characteristics of a 2 kW PEM fuel cell stack under different operating conditions and load changes

This paper mainly presents the AC impedance characteristics of a 2 kW PEMFC stack under different operating conditions and load changes. The AC impedances of the fuel cell stack are examined by a fuel cell impedance meter. Air stoichiometry, air humidity, and operation temperature are shown to have significant effects on the AC impedance of stack. When air stoichiometry decreases, the mass transfer resistance of stack increases obviously, but the influences on other resistances are very slight. The air humidity and operation temperature mainly influence the charge transfer resistance of stack. The influences of load changes on the AC impedance of stack are also investigated, and the results of which show that it is quite necessary to adjust the humidity of reactant gas according to the fuel cell load changes during fuel cell running. The AC impedance diagnosis of stack can provide some useful information for the running of fuel cell stack. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.