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Equivalent Circuit Models for Polymer Electrolyte Fuel Cell Stacks in Parallel at Operational Loads

Wenhua H. Zhu1, Robert U. Payne2, Donald Cahela1, R. M. Nelms3, and Bruce J. Tatarchuk1. (1) Center for Microfibrous Materials Manufacturing, Department of Chemical Engineering, 230 Ross Hall, Auburn University, AL 36849, (2) Department of Chemical Engineering, Auburn University, 207 Ross Hall, Auburn, AL 36849, (3) Department of Electrical Engineering, Auburn University, 200 Broun Hall, Auburn, AL 36849

Two PEFC stacks were first tested individually at a level up to 1 kW stack power with and without the embedded control devices, and then ac impedance measurements were conducted after the system reached a steady state. The two stacks containing 47 MEA cells each were connected in parallel using room air and pure hydrogen fuel supply (purity > 99.99%). Next, ac impedance evaluations were conducted after the stacks reached a steady state at a certain power level. The equivalent circuit model of the PEFC system in testing is developed through the real time data and non-linear least squares fitting. Data interpretation for the simulated elements was given according to the physical phenomenon and electrochemical reactions. The two PEFC stacks were then tested for pulse capabilities at different current levels. The physical elements in the equivalent circuit model were further fitted into a PSpice tool for electronic pulse simulation. The tested data from the digital oscilloscope are in satisfactory agreement with the results from PSpice simulation.