PEFC-Stack Development with up to 130°C Operation Temperature

Abstract

At the DLR Institute of Technical Thermodynamics new concepts for fuel cell stacks are being developed for various applications and load profiles. Thereby, the main focus lies on the simplification of the stacks for reaching a cost reduction as well as an increase of the (volumetric) power density. Today’s polymer electrolyte fuel cells (PEFCs) are applicable only within a limited operating range. This limitation restricts the spectrum of possible applications and hinders their flexibility during operation. Hence, one of the most important targets in fuel cell research is to enlarge the range of the operating temperature. Thereby, the continuous operation at elevated temperatures or an extended temperature range for a limited time comes into consideration. In order to avoidcritical operating conditions, to ascertain a sufficient durability and performance of a fuel cell stack, special concepts regarding the bipolar plates, the cooling strategy, the membrane electrode assemblies as well as a closer look on the water management are essential. Furthermore, the operating strategy of the stack has to be adapted with respect to all of the stacks’ components. In this way, operating temperatures from 60 up to 130 °C can be realized. A cold starting is feasible from -20 °C, even if during the start-up procedure the total net power can not be supplied right from the beginning. An elevated temperature range shall be applicable for short durations of approximately 1 hour. In addition, the DLR measurement technique for the determination of local current density distribution (PCB technology) is implemented in the fuel cell stacks for extending the life-time of the stacks by an adapted control strategy. The fulfilment of these “boundary” conditions leads to an improved operational flexibility of polymer electrolyte fuel cell stacks, especially in the stationary and mobile sector. The status of the development work, the definition of problems as well as the approaches to overcome them will be presented.