Future production with fully interlinked systems

According to development chief Scherer, all processes and technologies are based on decades of experience gained at ElringKlinger/EKPO in large-scale production for the automotive industry. This brings with it benefits such as high-precision products, in-house tool production and the application of automotive quality and management techniques, he says. The company has already run through the appropriate Production Part Approval Process or PPAP for the NM5evo stack, a vehicle fuel cell module with a power output of up to 76 kilowatts. Scherer also highlights that suppliers are validated in line with automotive series processes. All manufacturing procedures at EKPO for metal BPPs are already highly automated.

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Even so, Joachim Scherer believes that the high degree of production flexibility that is required to cover the wide range of BPP designs and variations means that it is does not make sense to further interlink individual processes at this stage. He does indicate, however, that dedicated BPP lines with fully interlinked production systems for individual stack platforms will be installed for the future manufacturing of very high part volumes.

What’s more, the component production manager reports that for individual production steps work is already underway to create innovative processes for the next-plus-one generation that should make it possible to decrease cycle times even further. Such processes will be needed for volumes ranging up to tens of millions of BPPs a year.

EKPO is already envisaging the mass production of 100,000 stacks annually. The company points out that this will require procedures that enable components to be processed and checked in less than a second, an undertaking that will understandably come up against limiting factors, as Scherer underlines: “This up to 10-Hz production goes well beyond today’s scale in terms of the critical requirements for processing speed, stability and control.” It would also spark increased demands on the materials and tools used.

Scherer is well aware of what this signifies: “In the years ahead, further developments are expected with regard to lower material costs, higher material quality, improved supply security and efficient tool production.” This calls for measures to optimize the component design, new methods of measurement and control that are integrated directly in the production systems and a further minimization of time-consuming component inspections.

Schaeffler focuses on functional coatings

Automotive supplier Schaeffler has chosen to focus on a pressing method for forming BPPs combined with the application of functional coatings. “Here we can leverage our core competencies. For instance every year we coat over a billion parts for conventional powertrains,” explains Benjamin Daniel who heads up the company’s fuel cell division. The job of a BPP coating is to maintain a high level of electrical conductivity throughout the entire service life as well as to stop metal ion contamination of the MEA. Otherwise the ions would accumulate over time on both the active catalyst material and at the sites in the membrane through which the protons can pass.

Schaeffler has been developing several coating systems especially for BPP modules as part of its Enertect range. One is based on platinum group metals for very high service life requirements, and another is based on a low-cost carbon coating. According to Daniel, this is advantageous for customers: “Thanks to our expertise in surface technology, we are in a position to offer application-specific coating development and also to balance this against costs and performance according to requirements.”

The coating systems are applied using the physical vapor deposition process which has already proved suitable for large-scale production – such as in the fabrication of heavily loaded valve train components, states Daniel.

Just as at EKPO, Schaeffler is also looking increasingly to scale up production. For example, at the beginning of the year a pilot plant at its headquarters in Herzogenaurach entered operation that will make more than 700,000 BPP modules for fuel cell applications on a yearly basis. The plant’s design means that it also has the potential to manufacture even greater numbers of BPPs for electrolyzers. According to Daniel, the individual processing stages of the pilot plant, which was designed by Schaeffler’s own specialized machinery department, are already highly automated. Furthermore, the pilot facility is embedded within a new hydrogen center of excellence at the Herzogenaurach site. The center includes a large area for testing electrolyzer technologies and fuel cells at the component, stack and total system levels.