Studies in degradation of Solid Oxide Fuel Cells are vital to market entry. Project SOFC Life found a major contributor to the degradation processes of SOFC.
Long-term stable operation of Solid Oxide Fuel Cells (SOFC) is a basic requirement for introducing the technology to the stationary power market, but the prospects for market entry of SOFC is directly linked to their longevity and production costs.
Research in prolonging the durability and lifetime of SOFC is hence vital for SOFC technology. Recently, DTU Energy Conversion and 12 partners from research institutes, universities and industry took part in the EU project SOFC-Life (2011-2013) to study major degradation effects of SOFC cells.
The mission of SOFC-Life was to develop models to predict the combined effect of several degradation phenomena on SOFC cells. To do this SOFC cells and stacks were deconstructed into single elements and interfaces which were considered to be the main contributors to performance loss.
New 2D and 3D techniques
These elements were then subjected to systematic long term experimentation in an out-of-cell setup with a close control of operating parameters covering a range of temperatures, current flows, water content and oxygen concentration. Samples were then removed from the experimental setups to examine the changes of physical and chemical properties over time.
This task was made considerably easier as DTU Energy Conversion in a project work package developed and refined several SEM (Scanning Electron Microscopy) based 2D and 3D microstructure characterization techniques. This made it possible to for instance compare the evolution of the measured conductivity to the evolution of the microstructure. The new techniques enabled the researchers to perform systematic quantitative characterization studies of the evolution of important microstructure parameters such as the interface area between particles, the length of the triple phase boundaries or particle size distributions.
“Additionally, the new techniques offered new insight into which microstructural aspects of the transport pathways are important for the effective transport properties”, explains researcher Peter Stanley Jørgensen from DTU Energy Conversion.
A major villain in the interface
Out of several physical and chemically themes investigated, only the processes at the cathode-interconnect interface are now considered major contributors to the overall degradation observed in SRUs (single repeating unit) and stacks. SRU is a single cell surrounded by two interconnects, which is the smallest stack possible.
SOFC-Life ended 31st December 2013, but the results of SOFC-Life are used in the project SCoRed 2:0, Steel Coatings for Reducing Degradation in SOFC, continuing the work to secure the economic viability of SOFC and preparing SOFC for market entry.