OPTIMIZATION OF OPERATING CONDITIONS IN A LABORATORY SOFC TESTING DEVICE

Solid-oxide fuel cells (SOFCs) are devices that convert chemical energy into electrical energy. They are assembled from three solid components, which, in principle, differ in their thermal expansion coefficients. These differences may cause residual stresses during an operation and consequently lead to physical damage of a cell. From this perspective, the reliability of an operating SOFC is seriously dependent on the thermal stress built inside the multi-layer structure. In this work, some operating conditions in the SOFCs based on an SDC electrolyte, an LSM cathode and a Ni-SDC anode were investigated both experimentally and theoretically. Within the theoretical analysis, the residual stresses and temperature profiles inside an operating cell were modelled with the finite-element method. The results of the mathematical modelling of the warm-up, steady-state or cool-down periods were used to optimize the cell geometry and the thickness of individual cell layers, and to determine the most appropriate operating cell conditions. In order to experimentally confirm some theoretical calculations, a new SOFC testing system was developed, which enabled relatively easy assembling and dismantling as well as quick changes in the operating conditions (temperature, atmospheres). Based on the modelling results, optimization of the operating conditions was proposed in order to reduce the thermal stresses built in the materials.