Study of a 5 kW PEMFC using experimental design and statistical analysis techniques

Within the framework of the French inter lab SPACT project (Fuel Cell Systems for Transportation Applications), the behavior of a 5 kW PEM fuel cell stack, fed by humidified hydrogen and compressed air, is investigated in a test platform at Belfort, France. A set of polarization curves are recorded, under various conditions of stack temperature, gas pressure, and stoichiometry rates, in order to obtain a kind of cartography, representing the static stack performance. Initially, the tests are defined considering experimental design techniques. In order to study the relative impacts of the physical factors on the fuel cell voltage, some polarization curve results are selected from the static tests available applying experimental design methodology. First, several analyses are used to estimate the impact of the stack temperature, gas pressure, and stoichiometry rate on the fuel cell voltage. Statistical sensitivity analyses (ANOVA) are used to compute, from the available data, the effects and respective contributions of the various physical factors on the stack voltage. The potential for the detection of any interactions between the different parameters is shown. Also, some graphic representations are used to display the results of the statistical analyses made for different current values of the polarization curves. Then, the experimental design method and its associated statistical tools are employed in order to identify the influence of the stack temperature and gas pressure on the fuel cell voltage. Moreover, it is shown how it is possible to reduce the number of experiments needed and how certain optimizations of the fuel cell operating parameters leading to higher performances can be achieved. The work presented aims at showing the suitability of the experimental design method for the characterization, analysis, and improvement of a complex system like a fuel cell generator. The future outlook is proposed in the final part of the paper. The methodologies developed for the analysis of the tests performed on the 5 kW stack could also be used to study different fuel cells and phenomena. For instance, the roles of additional physical parameters, linked with the gas humidification process, could be considered.