Bipolar plates (BPPs) are a key component in electrolyzers and fuel cells. BPPs include two key components: the membrane electrode assembly (MEA), in a fuel-cell system; and the catalyst-coated membrane (CCM), in an electrolyzer. In a fuel-cell stack, for example, the double-walled structure of the BPPs allows oxygen and hydrogen to flow to both sides of the MEA while water cools the stack. The problem is that the current process of producing BPPs is expensive, making widespread adoption of fuel cells uneconomical.
Now, researchers at the Fraunhofer Institute for Machine Tools and Forming Technology (IWU; Chemnitz, Germany; www.iwu.fraunhofer.de), in partnership with Profiroll Technologies GmbH (Bad Düben, Germany; www.profiroll.de), have developed a prototype system for roll embossing, named BPPflexRoll, which makes it possible for continuous mass production, instead of the conventional batch-wise fabrication method.
In the newly developed technology, the structure of the BPP is embossed using a pair of rollers (photo), with the wafer-thin metal band running continuously between them. One of the forming rollers is defined as the punch, the other as the die. Since the rollers used to form the flow channels have approximately only one line contact with the workpiece, the step-by-step forming can reduce the process forces by a factor of ten on average compared to conventional embossing.
“One major advantage of roll embossing is the higher process speeds involved. As many as 120 BPP half plates can be produced every minute,” notes Robin Kurth, group manager for forming machines at Fraunhofer IWU. The researchers hope that this shift in production methods will cut the costs of manufacturing BPPs in half.
A pilot-production line is already running at Fraunhofer IWU, and the first bipolar plates produced with the pilot facility are already being tested in fuel cells at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg. The Fraunhofer researchers presented one component of the system at the Hannover Messe last month (April 22–26).