Progress of the Evaluation and Analysis Methods for Durability of SOFC Stacks

Abstract

Recent progress in the development of R&D for the evaluation and analytical methods of SOFC stack durability is reported under the NEDO Japanese national project. The goal of this project is the following two points: (1) to develop the advanced evaluation and analytical methods for the cell stacks which show a lifetime over 15 years (130 kh) with high efficiency of over 65% LHV, and (2) to develop the evaluation and analytical methods for dynamic operation mode such as rapid start-stop and load cycling. Three practical stacks (one flat tube and two types of planar) were supplied by the stack developers and tested over 10,000 hours with high fuel utilization (Uf~85%). It was found that the same evaluation methods can be applied to the stack resistance component determination between normal Uf (=75%) and high Uf (85%) conditions. Relatively stable performances were reported for these stacks and degradation factors were considered taking into account the degradation mechanisms at cells and stacks. Under high Uf conditions, some specific degradation mechanisms are now analyzed in the cells. For rapid starts of stacks, evaluation protocols are considered taking into account the mechanical stress arising from the thermal distribution in the cells. Simulation methods are considered for the evaluation of performance after 15 years of operation in the stacks.