Chapter 7: Integrating Degradation into Fuel Cell Models and Lifetime Prediction Check Access

A one dimensional (1D) model for simulating Solid Oxide Fuel Cell (SOFC) isothermal performance with humidified hydrogen and air is introduced. It is based on a set of ordinary differential equations (ODEs) describing the local current density as a function of the flow path for parallel flow SOFCs. Isothermal operation is a reasonable idealisation for laboratory cells placed in comparatively large furnaces, especially when operated at low fuel utilization. Such small scale SOFCs are often used to characterize the electrochemical cell performance.

The electrochemical behaviour is modeled by a single constant Area Specific Resistance (ASR) by taking the slope of an experimentally recorded I-V curve. It will be discussed that suitable operating conditions are found at a steam content (fuel humidity) of approx. 50 Vol-% and low fuel utilizations of less than 10 %. Alternatively, the 1D model can be used to calculate the ASR from I-V data directly which is less strict on operating condition requirements. Using the 1D model also allows to convert endurance test data, usually delivering a V_cell(t) data set, at constant electric current into a corresponding ASR(t) data set. The ODE set is solved numerically. Based on this model, a further step is taken by introducing a simple model for describing SOFC degradation during stationary operation. The simple degradation model can be useful as a first approach to more sophisticated life time prediction models and for deriving accelerated life time tests.