Mathematical modeling and dynamic Simulink simulation of high-pressure PEM electrolyzer system

PEM electrolysis based hydrogen generator system model is developed by using Simulink in MATLAB. The model covers the following system components: PEM electrolyzer stack, water pump, cooling fan, storage tank, water tank, power supply, control unit and sensors. In simulation, PEM electrolyzer stack model is the most complex component and consists of four parts; anode and cathode modules, membrane and finally voltage calculations module. Efficiency drops and voltage losses in the PEM electrolysis stack are estimated. The overpotentials are investigated as anode and cathode activation, electronic and ionic ohmic resistances. In addition, the loss of the other components is considered. The model is tested against the dynamic changes and it responded with quick outputs. The cell and stack behavior under different conditions (i.e. ranging of temperature and pressure) are examined. The loss of each system component at different current densities is added to the simulation. The study shows that the loss of stack dominates the losses of other components at higher current densities. The simulation counts that the stack and system model can run with different cases and scenarios. It is run for the scenario that it consumes constant power for a high pressure operation. Results show that current drawn by the stack decreases as the voltage increases because of the increasing pressure. The model is also compared with the experimental results and the model is found to be consistent with the experimental data.