Now showing 1 - 2 of 2
  • Publication
    Metadata only
    Development of a controller for voltage stabilisation in fuel cells using an electric field modifier (EFM) electrode
    (IET, 2024) ;
    Costa Castelló, Ramon
    ;
    Serra, Maria
    ;
    The present work expands on the idea of the electric field modifier (EFM) as a control electrode in the membrane of a fuel cell (FC). Through electrochemical impedance spectroscopy (EIS) measurements it is shown experimentally that an EFM-electrode made of a gold mesh can be integrated into a fuel cell, without disrupting its function. Using the measured impedance spectra and a distribution of relaxation times (DRT)-approach a suitable equivalent circuit (EQC)-model is derived for the measured cell with the integrated EFM. Further measurements show that the EFM can mainly be regarded as a double layer (dl)-capacitor inside of the membrane. This capacitor, in conjunction with a specially designed H∞ -controller are used in a simulation to stabilise the cell voltage, while a square wave current is drawn from the cell, to represent a direct connection of the FC with an inverter. The system is shown to have excellent disturbance rejection.
  • Publication
    Metadata only
    Short-circuit behavior of a PEM fuel cell stack under various operating conditions
    Optimized grid integration of proton exchange membrane fuel cells in various possible applications requires a suitable protection system. For this reason, this paper examines the transient behavior of a fuel cell stack after an external electrical shortening. In order to show the influence of operating parameters on the short-circuit behavior, various experiments with changed anode and cathode humidity, cell temperature and anode and cathode stoichiometry are carried out. With this, manufacturers can estimate the short-circuit magnitude of their stacks and recommend a suitable plant protection system. It could be shown that the peak short-circuit current depends on the operating point as well as the operating conditions. For the steady-state short-circuit current, the gas stoichiometry has an impact on the deliverable current. For all other operating conditions the steady-state short-circuit current is approximately twice the recommended maximum operating current. Furthermore, a method to estimate the effective fuel cell stack capacity out of the transient short-circuit current is presented.