SOFC modelling was performed on two different levels. Micromodelling, which is mainly concerned with electrochemical kinetics, potential field distribution and mass flow in the electrode structure taking into consideration the actual geometry of the PEN structure. This approach is important for investigations of electrochemical kinetics. Macromodelling aims at the operating conditions of the whole stack. In this way current and potential distributions are obtained in the cell and the stack. In addition, the local temperatures and the gas composition under various load conditions can be calculated. The results for the steady state and transient conditions are important information with respect to the stack design.