Researchers at the Fraunhofer Institute for Machine Tools and Forming Technology (IWU) have developed a new welding process for the bipolar plates of electrolysers. By using electron beam welding, the efficiency can be increased and the processing time and production costs reduced.
A team from the Fraunhofer IWU has succeeded in building an electron beam system. This enables a new welding process: Electron beam welding. Electron beam welding uses electrons as the welding medium. Several electromagnetic lenses control the negatively charged particles, which collide at up to two thirds the speed of light and fuse the two workpieces together.
Electrolysers require a large number of bipolar plates (BPP) that enclose the conversion component CCM (Catalyst Coated Membrane). The higher the quality of the welded connection of the bipolar plates, the higher the efficiency of the system.
Most bipolar plate manufacturers currently rely on laser beam scanner welding, which uses focussed light (laser). A mirror directs the laser beam and guides it along the desired joints. However, the mechanics for (deflecting) the laser beam and the mirror limit the welding speed due to its inertia. For a bipolar plate the size of an A4 sheet of paper, weld seams with a total length of more than 1 metre are required, meaning that the welding speed is decisive for the production time.
Shorter processing time
The new process does not require a sluggish steering mechanism, which means that the electron beam can be guided without delay, significantly reducing the processing time. Flexibility is also increased: Thanks to the ability to quickly deflect the beam, several process zones can be processed simultaneously, where previously one joining point had to be processed after the other. Even pre- and post-heating processes can be carried out almost simultaneously.
The research team at the Fraunhofer IWU led by Dr Frank Riedel is experimenting with the parallel processing of five zones (melting baths). Riedel is certain: "Much more is possible with multi-bath technology."
Vacuum increases quality
From a quality point of view, the fact that this technology is used under vacuum conditions also speaks in its favour. These guarantee constant conditions without disruptive fluctuations in air pressure or humidity.
The particular challenge when joining bipolar plates is that even a single cavity, a hole or any other irregularity in the weld seam would lead to the entire component leaking. It would then no longer be usable. Project manager Patrick Urbanek: "With vacuum technology, we can rule out external influencing factors and achieve the highest possible weld seam quality from today's perspective."
The so-called electron beam system, with which Urbanek and his team are now conducting research as part of the "Hydrogen Republic of Germany" ideas competition launched by the Federal Ministry of Research and Education, is the first machine of its kind. The Steigerwald company is also involved in the construction and development of the electron beam system.
In the current calendar year, the research team is focussing on the further development of the technology. Maturity for small series production should be achieved by 2025. The new system is an integral part of the reference factory.H2, which aims to lay the foundations for the industrial mass production of electrolysers and fuel cells.
