High-pressure PEM water electrolyser performance up to 180 bar differential pressure

Proton exchange membrane (PEM) electrolysers (PEMEL) are key for converting and storing excess renewable energy. PEMEL water electrolysis offers benefits over alkaline water electrolysers, including a large dynamic range, high responsiveness, and high current densities and pressures. High operating pressures are important because it contributes to reduce the costs and energy-use related to downstream mechanical compression. In this work the performance of a high-pressure PEMEL system has been characterized up to 180 bar. The electrolyser stack has been characterized with respect to electrochemical performance, net H2 production rate, and water crossover, and the operability and performance of the thermal- and gas management systems of the test bench has been assessed. The tests show that the voltage increase upon pressurization from 5 to 30 bar is 30 % smaller than expected, but further pressurization reduces performance. The study confirms that high-pressure PEMEL has higher energy consumption than state-of-the-art electrolyser systems with mechanical compressors. However, there can be a business case for high-pressure PEMEL if the trade-off between stack efficiency and system efficiency is balanced.