Theoretical and experimental analysis of an asymmetric high pressure PEM water electrolyser up to 155Â bar

In this paper a semi-empiric zero-dimensional steady state simulation model of an asymmetric high pressure proton exchange membrane water electrolyser is being presented. Based on experimental investigations on a 9.6 kW asymmetric high pressure water electrolysis module, empirical parameters were determined. Measurements were taken by varying the production pressure between 70 bar and 155 bar, the process temperature between 45 °C and 75 °C and the current density from 0.81 A cm−2 to 1.85 A cm−2. Stack efficiency and hydrogen diffusion from the cathode to the anode side were determined and expressed by the faradaic efficiency. Stack efficiencies of up to 74.8% were achieved at 0.81 A cm−2, 75 °C and 155 bar. As expected the stack efficiency decreases with increasing hydrogen production pressure. A temperature decrease of 30 °C has greater impact on the efficiency than an increase of pressure from 70 to 155 bar. The faradaic efficiency at 1.85 A cm−2, 155 bar and 45 °C is higher than 99% and even at a high operating temperature of 75 °C higher than 97%. The presented model can be used for prediction of the stack voltage, gas production flow rates, water consumption and stack efficiency as function of input current, process temperature and production pressure. Results show a very satisfactory consistency of measurement and simulation.