Processes involving in the temperature variations in solid oxide fuel cells in-situ analyzed through electrode-segmentation method

We aim to mitigate the spatial temperature variations contributing to the thermal stresses in solid oxide fuel cells.We thus analyze the involving processes through spatial temperature, current, and impedance variations in-situ measured by the electrode-segmentation method in a microtubular solid oxide. We find that, despite the preheating, the excess air flow commonly supplied in the practical applications for the convective cooling is the prevailing factor on the temperature variations causing a significant temperature gradient in the air inlet region, that poses a high risk of mechanical failure. In terms of the flow configuration, counter-flow shows larger temperature and current variations. The impedance variations clarify the impact of the temperature distribution on the current variations. Namely, high temperature in the fuel upstream accompanied with the high hydrogen concentration boosts the local current density, thus, results in larger Nernst-loss in the downstream wherein temperature is lower as well. We conclude that the excess air flow indirectly contributes to the thermal stresses and thus we recommend the reduction of the excess flow.