Multiscale modelling potentialities for solid oxide fuel cell performance and degradation analysis

Abstract

Solid oxide fuel cells are electrochemical devices that are able to directly convert the chemical energy of fed fuels to electricity as well as to provide heat through exhausted gases allowing a higher energy efficiency compared to tradition thermal engines. However, the state-of-the-art materials show a drastic performance drop after too few working hours because of irreversible microstructural changes. Here the main issue consists of improving cell durability by optimising its structure and operative conditions. Modelling can significantly support this target, permitting a better understanding of different phenomena and providing information that are difficult to directly measure. However, degradation simulation is a quite challenging task due to the complexity of the studied systems, where different phenomena overlap, as well as due to the numerous data requested on both electrochemical and microstructural features. Depending on the available cell information and the analysis detail level, a multiscale modelling approach is a promising solution for providing effective results with reduced computational efforts. Based on a macroscale characterization, for example, semi-empirical degradation functions can be directly derived from electrochemical impedance spectra and area-specific resistance variations without knowing anything on the microstructure in order to estimate global cell performance and durability through a lumped-parameter model. Whereas, when aiming at the identification of an aged element specific behaviour, detailed formulations have to be introduced for each mechanism following a microscale approach. In such cases, a local-level modelling is fundamental in view of uneven distributions of properties on the cell plane which influence locally the degradation process development and resulting performance.