Renewable energy (RE) based hydrogen production via low temperature water electrolysis is attracting increased interest globally. Proton exchange membrane water electrolysis (PEMWE) technology is particularly suitable for integration with variable RE power due to its great load-following capabilities. The PEMWE-technology can also be designed to operate at high current densities and pressures, which can reduce the system footprint and make the technology particularly suitable for distributed hydrogen production using RE power (e.g., from wind or solar PV). However, to reach the cost targets for green hydrogen more R&D on PEMWE stacks and systems is required to improve the overall system efficiency, durability, and capital costs.

Institute for Energy Technology (IFE) has designed and built a flexible PEM water electrolyzer system platform for testing of small-scale prototype electrolyzers up to 33 kW and 200 bar differential pressure. This PEMWE system laboratory is part of a national research infrastructure on hydrogen and fuel cells in Norway (NFCH Centre) at the IFE Hynor Hydrogen Technology Center (IFE Hynor) at Kjeller. The PEMWE test rig is integrated with a sophisticated power conditioning system which consists of custom-built DC/DC-converters (for PEMWE, PEMFC, and Li-ion battery systems), all coupled to a DC-bus. This makes it possible to use the Li-ion battery system to test different hybrid electric topologies for the water electrolyzer system and to emulate different loads (e.g., grid load profiles, solar PV input). The PEMWE test rig can also be configured to test different types of PEMWE stacks and key components.

The PEMWE system test rig at IFE has now been fully commissioned, including testing up to the rated pressure of 200 bar on the H2-side. A small-scale (2 Nm³/h) prototype high-pressure PEMWE stack was used as reference technology for these tests. The high differential pressure prototype PEMWE stack was characterized by recording polarization curves at temperatures up to 80°C and pressures up to 190 bar. Electrochemical impedance spectroscopy was used to obtain information about the electrode processes and the degradation of the stack during operation and was recorded at selected current densities for the same temperatures and pressures as the polarization curves. The first results (Figure) show that at 80°C the voltage efficiency (HHV) decreases from 71.3% at 30 bar to 68.8% at 150 bar, while it at 50°C decreases from 66.3% at 30 bar to 64.4% at 150 bar. More results, including the calculation of current and overall efficiencies, will be presented in the final paper.

The one-of-a-kind high-pressure PEMWE System Laboratory at IFE is very well suited to study the performance of next-generation PEMWE stacks and systems, and to tailor and test control strategies that safeguards the system and maximizes efficiency and durability when operated using variable power based on RE power. The standard delivery pressure of PEMWE systems is today around 30 bar, but to realize H2-generation systems at several hundred bars there are several challenges related to system operability and safety that need to be addressed and solved. The PEM water electrolyzer test rig is now ready to be used to test and characterize different PEMWE stack technologies.