Mathematical model of a proton-exchange membrane (PEM) fuel cell

This work presents a mathematical modelling of a proton-exchange membrane fuel cell (PEMFC) system integrated with a resistive variable load. The model was implemented using MATLAB Simulink software, and it was used to calculate the fuel cell electric current and voltage at various steady-state conditions. The electric current was determined by the intersection of its polarisation curve and applied as an input value for the simulation of the PEM fuel cell performance. The model was validated using a Horizon H-500xp model fuel cell stack system, with the following main components: a 500 W PEM fuel cell, a 12 V at 12 A battery for the start-up, a super-capacitor bank to supply peak loads and a 48 V DC-DC boost converter. The generated power was dissipated by a variable resistive load. The results from the model shows a qualitative agreement with test bench results, with similar trends for stack current and voltage in response to load and hydrogen flow rate variation. The discrepancies ranged from 2% to 6%, depending on the load resistance applied. A controlled current source was utilised to simulate the variation of fan power consumption with stack temperature, ranging from 36.5 W at 23 °C to 52 W at 65 °C. Both model and experiments showed an overall PEMFC system maximum efficiency of about 48%.