Transient and Steady State Current Density
                                                Distribution Measurements in a Polymer Electrolyte
                                                Fuel Cell

During fuel cell operation the electrochemical activity often is not homogenous over the electrode area. This may be caused by an non-uniform water content in the membrane, an inhomogeneous temperature distribution, and reactant gradients in the cell. Consequently a variation of the current density over the cell area occurs which tends to result in inferior performance. For in situ measurements of the current density distribution in fuel cell stacks a segmented bipolar plate was developed. The segmented bipolar plate was first tested in single cells with stack endplates to verify the function of all components. The tests showed that the measurement tool works very reliable and accurate. The insight in an operating fuel cell stack via current density distribution measurement is very helpful to investigate interactions between cells. Results can be used to validate models and to optimise stack components, e.g. flow field and manifold design, as well as to detect the best stack operating conditions. By applying segmented bipolar plates as sensor plates for stack system controls an improved performance, safe operation and longer life cycles can be achieved. The developed segmented bipolar plates with integrated current sensors were used to assemble a short stack consisting of 3 cells; each of them having an active area of 25cm2 divided into 49 segments. The design of the bipolar plate proofed very suitable for easy assembling of single cells and stacks. First measurement results show that different current distributions can appear in the cells and these can vary from cell to cell, depending on the operating conditions of the stack. Electrical coupling between the cells was investigated and found to be only marginal for the assembly used.

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Effect of gas channel depth on current density distribution of polymer electrolyte fuel cell by numerical analysis including gas flow through gas diffusion layer

Journal of Power Sources ◽

10.1016/j.jpowsour.2005.08.004 ◽

2006 ◽

Vol 157 (1) ◽

pp. 136-152 ◽

Cited By ~ 33

Author(s):

Gen Inoue ◽

Yosuke Matsukuma ◽

Masaki Minemoto

Keyword(s):

Fuel Cell ◽

Numerical Analysis ◽

Current Density ◽

Gas Flow ◽

Current Density Distribution ◽

Gas Diffusion ◽

Polymer Electrolyte Fuel Cell ◽

Channel Depth ◽

Gas Channel ◽

Flow Through

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Analysis of Single PEM Fuel Cell Performances Based on Current Density Distribution Measurement

Journal of Fuel Cell Science and Technology ◽

10.1115/1.2173664 ◽

2005 ◽

Vol 3 (3) ◽

pp. 351-357 ◽

Cited By ~ 17

Author(s):

P. C. Ghosh ◽

T. Wüster ◽

H. Dohle ◽

N. Kimiaie ◽

J. Mergel ◽

...

Keyword(s):

Fuel Cell ◽

Density Distribution ◽

Current Density ◽

Operating Temperature ◽

Current Density Distribution ◽

Polymer Electrolyte Fuel Cells ◽

Operating Conditions ◽

Cathode Side ◽

Gas Pressures

A new in situ measurement method of mapping the current density distribution in polymer electrolyte fuel cells (PEFC) is used to analyze the performance of a fuel cell under different operating conditions. The present method is useful in investigating the current density distribution in a single cell as well as a stack, which carries the information about the local reactant activity over the electrode area. It was found that the current density close to the gas inlets is strongly influenced by the reactants' relative humidity. The performance close to the gas outlets is greatly influenced by the inlet gas pressures and the stoichiometry factors of the reactant gases, mainly on the cathode side. It was also observed that the performance of the fuel cell drops with the increase in operating temperature if the reactant gases are not sufficiently humidified.

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