Prediction of Performance Degradation Due to Grain Coarsening Effects in Solid Oxide Fuel Cells

Tuesday, 25 July 2017
Grand Ballroom East (The Diplomat Beach Resort)
J. H. Mason (U.S. DOE, National Energy and Technology Laboratory, Oak Ridge Associated Universities), I. B. Celik (MAE Department, West Virginia University, Morgantown WV, U.S. DOE, National Energy Technology Laboratory), S. Lee (U.S. DOE, National Energy Technology Laboratory, AECOM), H. Abernathy (AECOM, U.S. DOE National Energy Technology Laboratory), and G. A. Hackett (U.S. DOE National Energy Technology Laboratory)
Long term degradation of solid oxide fuel cells is one of the biggest impediments to commercialization. Due to the inordinate amount of time required to properly test degradation experimentally, physics based models which can predict long term degradation can be crucial time and money saving tools. At the cell level, one of the primary modes of degradation comes from grain coarsening and the resulting changes in microstructure properties. In this study a multi-physics model of a single fuel cell is presented which aims to predict performance loss as a function of time caused by coarsening in the electrodes of an LSM/YSZ/Ni SOFC. Microstructural properties are changed as a function of time from their initial values using functional relations derived from data from experiments and phase field models. Specie and charge transport equations are solved using these parameters to predict performance changes with time which result from the aforementioned microstructural changes. The model is first calibrated such that it correctly captures the performance and impedance response of a particular button cell at a given time without any degradation. This same model is run for a duration of 750 hours with performance data being measured for the same cell including impedance measurements being taken intermittently. Performance change over time predicted by the model are compared to experimental data. It is found that the model predicts a slower degradation rate than the rate which occurs experimentally. This is deemed reasonable as other forms of degradation are not being accounted for. The model is then used to make long term predictions of cell performance loss due to grain coarsening. The resulting degradation rate is considered to be the theoretical minimum which occurs when all other modes of degradation are not present. Work is underway to include other forms of degradation in the model so that a complete and robust degradation prediction tool is available for design analysis without the need for costly long term degradation measurements.