Design, Optimization, and Fabrication of Slotted-Interdigitated Thin Metallic Bipolar Plates for PEM Fuel Cells

Abstract

Thin metallic sheet bipolar plates (BPPs) with sustainable coating are promising candidates to replace conventional graphitic or machined thick metal plates due to their lightweight and low cost. Interdigitated flow field design is easier for two stamped thin metallic sheets joined together to compose reactant flow fields in both sides and serpentine coolant flow field in the middle. Unfortunately, this kind of BPP inevitable brings two main defects: rupture of material during forming process and uneven flow distribution in practical operation. First, we propose a slotted-interdigitated configuration of the flow field for proton exchange membrane fuel cell with consideration of the characteristics of the metallic sheet forming process. In order to relieve the uneven flow distribution, an analytic model is introduced to analyze the reactant gas flow based on the similarity between the gas flow and the electrical current. Furthermore, an optimization model is proposed. The depth of the slot on the channel rib is optimized to eliminate the uneven flow distribution to obtain high reaction performance. Second, we studied the BPPs from the manufacturability perspective because it is also another important factor that should be considered in the design stage. The key geometric dimensions of flow field section, where the rupture occurs, are extracted and parametrized. Finite element analysis model is established to analyze the formability of BPP by flexible forming process (FFP). In addition, different dies with various flow channel sections are prepared and experiments are performed. Some design principles about material selection and key geometric dimension definition are proposed to improve the formability of BPPs. In the end, based on the design principles and experimental results, the dies are carefully design and fabricated experimental setup for FFP is prepared and practical experiments are performed. High quality metallic BPPs are achieved eventually by FFP.