Mapping of contact pressure distribution within PEFC: comparison between Tekscan sensors and Fuji films.

A not uniform pressure distribution in Polymer Electrolyte Membrane Fuel Cell (PEFC), such as in other kind of fuel cells, could introduce parasitic effect that may cause reduction in performances and/or a reduction of the cell/stack life. An insufficient clamping pressure may result in sealing problems, such as fuel leakage, internal crossover and high contact resistance between the gas diffusion layer (GDL) and the bipolar plates. On the other hand, a high clamping pressure may squeeze the relatively thin GDL and change its porosity and permeability, choking the flow of gases and making the migration of water difficult. In the last few years a number of papers aimed to determining the pressure distribution on the Membrane Electrode Assembly (MEA) and the effects of this pressure distribution on the cell performances in PEFC has been published. To compare model previsions with the experimental results an accurate measurement of the pressure distribution inside the cell is requested. To gain information about the actual pressure distribution inside the cell, pressure sensitive films are usually employed. These films supply colored images of maximum contact pressure reached on the MEA surface and, by calibration, allows the corresponding pressure values to be computed. Authors of this work proposed an alternative method based on piezoresistive sensor array, that allows maps of the pressure distribution inside the cell to be measured in real-time. The sensors matrix has about two thousands sensels, allows the acquisition of many maps each second and can be reused many times. In the present work the new experimental approach, previously described in another work [under submission to J. Pow. Sources], was applied to a PEFC single cell in comparison with conventional pressure sensitive films with the aims of highlighting advantages and drawbacks of each measurement system. The new experimental approach is able to supply the information needed in designing and modeling the clamping configuration of a fuel cell stack and, then, in its optimization to increasing stack performances and endurance.