If the fuel cell is to become competitive as a technology alternative for powertrains and power generation, all components and subsystems must be subject to further research and development. The goal is to optimise the performance, service life, efficiency and dimensions of the cells according to the specific requirements of the area of application. High-performance fuel cell stacks are complex constructions: Hundreds of individual cells, consisting of membrane-electrode units with 10-micrometre-thin membranes, have to be coordinated with bipolar plates with an overall height of just under 1 millimetre and filigree gas distribution structures plus the gas diffusion layers and joined together to form a stack. So far, however, there has been no universal research platform. The few companies that develop complete fuel cell systems usually do not disclose operating data and details on material composition for competitive reasons. This makes it difficult for small and medium-sized component suppliers to enter the market.
» With a generic stack, fundamental phenomena can be investigated in a reproducible way. «
Robot-assisted fuel cell stack assembly.
Pressing the fuel cell stack.
Fuel cell stack research design by ZSW.
Graphite bipolar plate for automotive applications.
Fuel cell components – bipolar plate.
Commissioned by the FVV, the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) developed the design concept for a generic fuel cell stack. The stack is needed as a research and test platform, as the fuel cell – or specifically the polymer electrolyte membrane fuel cell (PEMFC) used as a vehicle powertrain – needs to be far more cost-efficient in order to succeed in the market. To this end, the power yield per cell needs to be increased further. This is not just an issue regarding the cells themselves, but of optimising the entire system. The fuel cell periphery has a decisive impact not only on the performance of the cells, but also on their service life. As such, unequal distribution of hydrogen across the cell membranes can result in premature ageing. And pollutants in the intake air cause the catalyst material - usually high-quality platinum - to degrade prematurely. Greater knowledge of the relationship between pollutant input, filtration and ageing behaviour could help to reduce the amount of the precious metal needed. The problem when developing filters, compressors, seals and other components is that testing has previously generally only been performed on commercially available fuel cell systems. This is exactly the prpblem, the research project, sponsored by the FVV, aims to solve.
» The stack will be just as important as the single-cylinder research engine is at the institutes for combustion engines. «
First of all, a basic question had to be answered: What performance and dimensions are required of a low-temperature fuel cell if it is to cover as many applications as possible later? The researchers initially conducted a survey of the FVV member companies to gauge opinions, which were then discussed intensively in the user committee. According to the experts, the high level of power density required can only be achieved with metallic bipolar plates. After making this fundamental decision, the ZSW developed a design concept that, for example, defines both the active surface area per cell as well as the number of cells and, above all, does not conflict with designs that are already protected. The concept was then successfully validated on the basis of initial simulations.
The size and design of the developed stack concept corresponds, e.g. in terms of power density, to the systems used in the automotive sector today. The stack module is designed in such a way that useful tests in short and long stack format are possible, e.g. through modularisation on a 10-cell stack. Various configurations are possible, e.g. co-/counter-flow. A market overview of commercially available stacks was also prepared. The feasibility in terms of available manufacturing processes was examined and the design of the fuel cell was taken into account. The developed stack concept is suitable for a power output of up to 150 kW. It includes the channel dimensioning, which was determined via CFD cell modelling, the channel web geometry as well as a distributor and sealing concept for the bipolar plate and other components. The complete design of a generic stack could be the subject of a follow-up project.
2019-08-31 to 2020-06-29
Dr.-Ing. Jan Haußmann
Schaeffler Technologies AG & Co. KG
1 | Department Fuel Cell Stacks - ZSW Centre for Solar Energy and Hydrogen Research Baden-Württemberg
Head of research:
Dr. rer. nat. Ludwig Jörissen
Research Association for Combustion Engines eV
Lyoner Strasse 18
60528 Frankfurt am Main
T +49 69 6603 1345