Fuel cell operation under degraded working modes and study of diode by-pass circuit dedicated to multi-stack association

To make fuel cells commercially viable in the transportation sector, it now becomes crucial to develop some technical concepts that allow continuation of the operation of the multi-stack generator even if one stack fails. The present work addresses this problem, and the paper presents some studies related to the electrical behaviour of a polymer electrolyte fuel cell operated under fault condition and equipped with an anti-parallel diode used as a by-pass circuit. Some experimental results are obtained using a two cell stack placed in a set-up that reproduces the coupling in series of two fuel cell stacks. These results allow evaluation of the by-pass diode solutions in the case of fuel cell specific degraded working modes, such as the break of the gas reactant feed. The impacts of the starvation phenomenon on the stack performances are analysed and commented upon from the characterisation data obtained, in particular, by electrochemical impedance spectroscopy. Some extrapolation and extension of the first experimental investigations are done with the aim of preparing the next association of higher power stacks operated with their reverse diodes. The proposed experimental and modelling works show that the value of the stack impedance will have a key role in triggering the diode conduction.