Study of the dynamics of a four-module fuel cell stack to be integrated in a hybrid electric power plant of a utility vehicle

A four-module PEM fuel cell stack was electrochemically characterized prior to its incorporation to a hybrid power plant of an electrical utility vehicle. The 3 kW fuel cell stack, comprised of 4 units of 100 membrane electrode assemblies (MEAs) in an open-cathode and air-cooled configuration, was characterized in order to identify its optimum operational parameters. The open cathode configuration is a common approach to reduce parasitic loads and increase energy efficiency in fuel cells; however, the forced convection derives frequently to internal dehydration. Voltage reversal caused by lack of reactants, many times due to dehydration at the reaction sites (membrane-electrode interface) is a common failure source for this kind of configuration especially at high current demands. Therefore, water management becomes crucial for preventing fuel cell's performance decrease and permanent failure. Subsequently, a smart water management strategy had to be established prior to the power plant integration into the vehicle for the fuel cell's performance to be guaranteed during the vehicle duty cycle. For this purpose, a testing protocol was established for testing each module based on linear voltammetries, electrochemical impedance spectroscopy and thermal images in order to observe cell's voltage and resistance as indicators of internal hydration, reactants concentration, and heat distribution during the stack operation. Polarization curves were obtained for each module and from them, the point (voltage, current, temperature and air vent) for steady operation was identified as the recommended condition for nominal performance during the fuel cell operation in the hybrid power plant of the electrical vehicle.