Stack and Individual Cell Impedance

Numerous studies have been conducted on AC impedance in single cells. From a practical point of view, stack experiments provide more interesting data because a single cell is rarely used in real-world applications. With AC impedance it is possible to separate the impedances of each cell of the stack, to understand the gas distribution within the stack, and to detect a failure in the stack. 

Diard et al. [37] studied the impedance of a commercial 10 W four-cell stack with individual cell geometric areas of 24 cm2 (8x3 cm2). The stack was operated on H2/02 at 80°C, and the experiments were performed with equal flow rates of 20 mL/min and pressures of Pu = 0.5 bar and P0 = 0.2 bar at the stack inlet. The 

ZnOO 2vto A(.v) + Zw(.s ) where, v is the Laplace complex variable. 

Idc = 3 A and dr = 10 mA [37], (Reproduced by permission of ECS—The Electrochemical Society, and the authors, from Diard JP, Glandut N, Le-Gorrec B, Montella C. Impedance measurement of each cell of a 10 W PEMFC stack under load.) 

Zstack is the sum of the cell impedances plus the impedance of the wire connected to the unipolar plate of the first cell, Zn  

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