Solid Oxide Fuel Cells – Integrating Degradation Effects into Lifetime Prediction Models
Long-term stable operation of Solid Oxide Fuel Cells (SOFC) is a basic requirement for introducing this technology to the stationary power market. Degradation phenomena limiting the lifetime can be divided into continuous (baseline) and incidental (transient) effects.
This project is concerned with understanding the details of the major SOFC continuous degradation effects and developing models that will predict single degradation phenomena and their combined effect on SOFC cells and single repeating units.
The planar SOFC cell and stack is deconstructed into single elements and interfaces (‘finite elements’) which are considered to be the main contributors to performance loss, i.e. degradation. These elements are chosen to be electrode samples, representing the time evolution of the materials in the SOFC cell, and samples including the interfaces between interconnect and cell, especially including the cathode contacting. These single elements will be subjected to systematic long term experimentation in an out-of-cell setup with a close control of operating parameters, simulating real stack operation. The conditions for instance cover a range of temperatures, current flows, water content and oxygen concentration. By removing samples periodically, the changes of physical and chemical properties over time under these conditions are examined. The results will allow the processes and kinetics of the change to be quantified and lead to descriptions of the single degradation phenomena as functions of time and condition parameters at the materials level. The changes in materials will be translated into the parameters of the electrochemical performance equations and be integrated into predictive models of the effect of degradation on more complex units like cells or single repeating units.
The outcome of the project will be an in-depth understanding of the degradation phenomena as a function of the basic physico-chemical processes involved, including their dependency on operational parameters. Up to now research has rarely succeeded in linking the basic changes in materials properties to the decrease in electro-chemical performance at the level of multi-layer systems and SOFC cells, and even up to single repeating units.