Simulink-Femlab Integrated Dynamic Simulation Model for a PEM Fuel Cell System

The necessity for reliable simulation models, able to support the fuel cell systems development activity, has increased continuously during the last years. The present work proposes a model which integrates the finite element method in a dynamic simulation, in order to achieve higher accuracy and the possibility to investigate the influence of various parameters on the fuel cell dynamics. The model is implemented using Matlab/Simulink and consists of two interacting main subsystems that calculates the fuel cell power response and the stack thermal behavior. The first simulates the mass transport and electrochemical phenomena using a model implemented in Femlab, and considers as input parameters the stack geometry, reactants pressure, flow rate and composition and the stack average temperature. The last parameter is also evaluated by the second model, implemented also in Femlab, which considers the stack geometry, cooling air flow rate and ambient temperature. Both models were validated using the experimental data acquired on a Ballard Nexa 1.5 kWe PEM system. The results prove that integrated model simulates with accuracy the dynamics of the PEMFC system and the interaction between the stack and the auxiliaries. The proposed model was used as a predictive tool for two situations. In the first simulation, with a relative fast dynamic, the model demonstrates that the cooling fan control strategy is essential for transient conditions characterized by a significant load decreasing. In the second, the model estimates the variation of the PEMFC main parameters on a 24 hour cycle, confirming its reliability.