Numerical analysis of flow configurations and electrical contact positions in SOFC single cells and their impact on local effects

Abstract

Predictable long-term operation is key to the industrial roll-out of SOFC technologies; as one of the primary factors hindering steady and reliable operation, performance degradation is one of the main challenges facing SOFC development. A homogeneous temperature profile is essential to the steady long-term operation of SOFC cells. In order to investigate and improve the temperature distribution across the cells, a ceramic housing was developed for an industrial scale (100×100mm2) SOFC single cell with the aid of a spatially resolved numerical model. This study investigated the influence of co-, counter-, and cross-flow configurations, as well as various electrical contact positions in order to analyse the current density distribution and temperature evolution within the cell. The chemical and electrochemical performance of the model were validated with in-house experimental data gained from operating the cell within the developed cell housing under three hydrogen/nitrogen mixtures of varying levels of humidification. The simulations revealed that the outermost parts of the cathode are subject to diffusion limitations, which can lead to local air starvation effects. Moreover, they showed that the position of the cell's electrical contacts has a distinct impact on the current density distribution, in addition to affecting the temperature profile of the cell. This study found that the counter-flow configuration, in combination with placing the electrical contacts on the inlet side of the cathode led to the most homogeneous current density and temperature distribution across the cell. Most importantly, the position of the electrical contacts was identified as having a major influence on the cell's current density profile, and these position changes were able to homogenize the temperature distribution across the electrolyte. This configuration is thus proposed as a viable method of both ensuring the steady long-term operation of SOFCs and prolonging their lifetimes.