(Invited) Industrialization of PEM Electrolyzer Stack Platforms: Driving Lab-Scale Innovation to Multi-MW Implementation

Abstract

The Hydrogen production plays important role as part of energy transition strategy in Germany as well as in visions and subsequent policy of European Green Deal activities. Schaeffler [1] is driving further technological development with strong financial backing of European (CHP) and German funding (H2Giga). PEM water electrolysis is regarded as powerful technology, bringing advantages of limited installation footprint, broad range of operating conditions, especially in terms of dynamic load range and featuring high efficiency between 75-90% (based on HHV) [2].Minimizing the Levelized Cost of Hydrogen demands reduction in CAPEX, OPEX, maintenance whilst extending lifetime to secure full Return of Investment [3]. In addition, production of green hydrogen needs to anticipate the intermittent and distributed nature of renewable energy sources whilst functioning in a decentralized energy distribution network. Enabling maximum uptime sets high demands on the stack performance requirements and its material specifications. Here we show examples of how component development and design iterations make a huge impact on the commercial viability of electrolysers in industrial applications.Efficiency is key when converting renewable electricity and water into green hydrogen and other chemicals, even though PEM electrolyser stack technology is deemed capable of increasing current densities up to 10 A/cm2. Therefore, State-of-Art commercial stacks are rated at current densities between ~1-3 A/cm2, but this anticipated trend to increase power density underlines the necessity to reduce the total electrical resistance and avoid Ohm’s losses.Critical to success is selecting materials that can sustain functionality, stability and compatibility within an operational window being pushed to higher current density to increase stack output, whilst reducing PGM content and overall cost. Progress has been achieved by combining formed metal components with durable, conductive coatings, and establishing optimum compression.Most promising results published in open literature are based on small cells on laboratory scale (5-25 cm2 active area). So-called “screeners” are ideally suited for studying phenomena under well-controlled conditions with a plethora of diagnostic tools. In contrast, large-area stacks operated in the field don’t always operate under ideal operating conditions and can show variability in performance characteristics that escalate into unexpected degradation issues. Of course, stack behavior is dependent on its local environment within the BOP system, relative to its peers. We show how continuous remote monitoring during operation helps identify non-uniform stack operation and flag off-spec conditions, which could form the basis of Accelerated Stress Tests for testing in the laboratory.In this work we estimate how much stack technology can be improved further by forming BPP metal structures and optimizing the component design using CFD. Especially when scaling stack hardware to larger capacity, there is much emphasis on enhanced thermal management to avoid hot-spots and mitigate non-uniform degradation mechanisms and premature stack failure. Simulation results will show how flow designs could be adapted maintain uniform conditions when scaling up the active area or adding more cells to the stack.Robust Stacks are demanded for market ramp-up, demonstrating predictable performance over a long lifetime and insensitivity to a wide range of possible operating conditions. However, but to the best of our knowledge, no component- nor stack- supplier is willing to provide extensive guarantees. Fortunately, stacks quality can be improved significantly by strong automotive and manufacturing industries stepping into the PEM electrolyzer arena and introducing their automated assembly, mature manufacturing and controlled processes to guarantee reproducibility, tight tolerances, superior quality and support supply chain development. Before ramping up global production capacity massively, all players would benefit from standardizing general geometric specifications of stacks so we can leverage a stronger collective learning curve with increasing numbers.