In cooperation with the Forschungszentrum Jülich GmbH (FZJ) and a national consortium of component suppliers, the BMW Group is developing Solid Oxide Fuel Cell (SOFC) technology for Auxiliary Power Units (APU) in passenger cars. Considering key challenges of the automotive application like rapid start-up, large number of thermocycles, compact construction and low cost, a lightweight cassette design has emerged allowing the mounting of high power density anode supported SOFCs. The design is based on modeling results which were conducted to optimize gas flow distribution and to reduce contact resistance. The flow distribution was investigated by using commercial Computational Fluid Dynamics (CFD) software and then validated by experiments, whereas the contact resistance was analyzed by a commercial Finite Element software. The results provide a design guideline to optimize the geometry of the interconnect plate. Cost-effective embossing and punching technologies were used to produce the metal components of the cassettes to be completed by laser beam welding. Up to now, stacks with 2, 5, 10 and 15 levels have been assembled using conventional glass ceramic seals. First results of stack operation are presented covering tests under stationary conditions for more than 5000 hours as well as thermocycles with heating rates up to 25 K/min. Engineering diagrams have been derived via CFD to facilitate a rapid estimation of the pressure drop and the flow resistance, respectively, in wave-shaped channels embossed in sheet metal interconnects without need of extensive calculations. It has also been demonstrated that results based on CFD simulations can give information about design drawbacks and thus provide optimization potential for the design process. Experimental results show a degradation rate between 33 and 47 mV/kh during the first 2000 hours of operation and then a considerable continuous increase of the degradation rate after 3500 hours. During this time the lightweight stack was operated at 800 deg C at a constant load of 0.3 A/cm2. Concerning the fast start-up capability the experimental results exhibit that the lightweight stack can withstand multiple fast start-up cycles without noticeably degradation.
Lightweight cassette type SOFC stacks for automotive applications
Leichtgewichtige kassettenartige Festoxidbrennstoffzellenstapel für den Einsatz in Kraftfahrzeugen
2006
16 Seiten, 12 Bilder, 3 Tabellen, 10 Quellen
Aufsatz (Konferenz)
Englisch
Dynamic behaviour of SOFC short stacks
Online Contents | 2006
|Cube-type micro SOFC stacks using sub-millimeter tubular SOFCs
Online Contents | 2009
|Development of cube-type SOFC stacks using anode-supported tubular cells
Online Contents | 2008
|