In the project ‘Autostack Industrie’, five OEMs and various suppliers are working together in order to bring the key technologies in the manufacture of stacks – the core components of fuel cell vehicles – to industrialization stage. The focus of the project, which runs until the end of 2021, is to prepare the appropriate high-speed processes. The challenges are considerable, but the initial results are positive.
Aside from the FC unit, the drive train of a fuel cell (FC) vehicle includes a battery to compensate for the system reaction time and to raise the efficiency in the acceleration of the vehicle, an electric engine, transmission as well as a hydrogen tank. The complexity and number of parts of the FC system are in this respect, similar to a combustion engine. A key component is the FC stack. This is by contrast, far different from the assembly of a basic engine from a process engineering point of view. Depending on capacity, the stack alone consists of up to 400 pairings of individual parts (cells) in addition to assembly parts, endplates, and system interfaces. On top of this comes the system technology for the operation of the stack in the vehicle. “Compared to the battery electric vehicle, in total there are many more components on board, as the ‘charging pole’ is, for all intents and purposes, integrated into the vehicle, because the electrical energy is being generated during the journey as required”, says André Martin.
The owner of the consultancy of the same name is coordinating the Autostack Industrie project with Ludwig Jörisson from the Ulm Research Institute ZSW. The project is funded by the Federal Ministry of Transport and Digital Infrastructure (BMVI) under the National Innovation Programme for Hydrogen and Fuel Cell Technology (NIP) in the amount of 30 million euros and is coordinated by NOW GmbH. The goal is to bring the key technologies of stack manufacture to industrial maturity. In addition to the ZSW, the four OEMs, BMW, Daimler, Ford, and Volkswagen as well as various suppliers (see infobox) are participating. Audi has also recently joined, responsible for developing FC brands in the Volkswagen company.
The ongoing project which began in 2017 and runs until the end of 2021 pursues three main ambitious objectives:
- Automotive high-performance technology: highest power density including lower platinum loading, complete project maturity, the achievement of automotive target costs
- The exploitation of industrial economies of scale: joint FC specification and system interfaces, scalable FC output, common technological platform
- Mass production capability: selection and evaluation of critical processes, the achievement of automotive quality requirements, plant planning for 10,000, and 30,000 stacks per year.
Taking advantage of previous projects
Benefits can be derived from the results of previous projects AutoStack (2009-2012, EU project, feasibility study) and AutoStack Core (2012-2017, EU project, technological proof of concept). Industrialisation is the focus of the national project: Autostack Industrie. “With sufficient time it will thus be possible to prepare for the production of a large number of vehicles through the development and testing of industrialization-ready high-speed processes for stack manufacture and be able to meet future market demands in appropriate phases”, explains Martin. Specifically, this means having a stack product and a manufacturing process that can be converted to industrial-scale over a manageable time period of 18 to 24 months following project completion. This fits nicely together with the plans of German automotive manufacturers, who have announced increasing quantities of FC vehicles from 2023 and 2024.
With respect to resources allocated and the overall budget in the project, Martin estimates that around two-thirds are allotted to product development including the issue of scaling, and a third on production development. “We have tried to bring all important aspects that play a role in stack development together in one project”, underlines Martin. He makes it clear: “This is not about research development, but product and manufacturing development.”
Close cooperation among the project partners is particularly important. Learning from the previous projects, working in close cooperation at the interfaces is essential. “It is extremely important that the experts for the major main components work together in the development”, explains the coordinator. In the project there is a main contact partner responsible for each major component – the membrane electrode assembly (MEA), the bipolar plate, the gas diffusion layers (GDL) and the catalysers. In addition those responsible assume the roles of quality management, specification and manufacturing development.
Initial results of this cooperation are very promising. It has allowed OEMS to agree on a specification and a fundamental system description with the relevant interfaces. “This constitutes a new and unique agreement in this form”, underlines Martin – and on the other hand, the result of several years of cooperation based on mutual trust. At the end of March 2020, the first development phase – Evolution 1 – of the stack development will be completed and the level achieved will be evaluated.
Around 60 stacks will be constructed by 2021 in two development phases. They will be tested by the participating OEMS, by the ZSW and other project partners. Depending on the test target objective, different stack sizes will be used. The specified reference output of the stack is 85 kW. “It is vitally important for us that we go into the second development phase with a robust design approach”, emphasizes Martin, “in order to achieve a sufficient degree of maturity by the end of the project”.
The challenge of long-term durability
Before series maturity, there are certainly a few challenges to overcome. These include long-term durability. We are not quite there, according to Martin. A degradation of 10% is allowed over the expected lifecycle of a FC vehicle of 6,000 operational hours. Essentially the MEA is impacted by degradation. However other components and mode of operation also have an influence. In terms of the latter, primarily so-called stressors such as temperature, pressure and humidity in dynamic load change have an effect. According to Martin, these parameters can be mitigated, however the development of optimized parameters is time-consuming.
An important lever is also the smooth coordination of the main components. Martin underscores: “Only by combining can we get the results we want.” Model analysis as well as validation tests play a major role in selecting the main components. “There are very many interdependencies to take into consideration in order to make an optimal selection”, says the project coordinator. On the issue of platinum reduction we are on the right path. As opposed to the previous model, the platinum loading of the anode was able to be reduced. It is significant that according to current calculations, with today’s charging and the power density achieved, automotive target costs can be achieved and done so at a production volume of around 30,000 stacks, according to the project coordinator.
Another task to be accomplished is to substantially reduce the amount of time it takes for the stack to start operation. In this process the electrochemical components of the stack are activated. The length of time must be reduced from a few hours to a few minutes, so that the commissioning is compatible with the production sequence of mass production. In order to develop a suitable procedure for this, an enormous amount of testing has to be carried out. This example illustrates very clearly how closely product development and manufacturing development are interwoven, stresses Martin.
Nevertheless the FC expert is certain that the technological development of FC technology in this country is on equal footing with key competitive regions such as China, Korea, Japan or the USA, without forgetting that some players have an edge in industrialization. In the material and component area, the German supplier industry is among the leading global technology providers. This is not the case for battery cells, the main suppliers of which are in Asia. A successful development of the Autostack Industrie project can therefore certainly contribute majorly to successfully forging a path to series production readiness of automotive FC technology.