The integration of fluctuating renewable energy sources is a major challenge for the electrical grid. Large energy storage capacities could facilitate an increasing integration of renewable energies. Power-to-gas plants represent a possible option by using surplus electricity for the electrochemical production of fuel gases (usually hydrogen). These can be stored and, if necessary, be reconverted into electrical energy (Power-to-Gas-to-Power). This enables both a short-term stabilisation of the electrical grid and a long-term storage of excess electrical energy. PtG-concepts based on reversible solid oxide cells (RSOC) are particularly promising. Theoretically, they have the highest efficiencies and enable electrolysis and fuel cell operation with the same electrochemical cell. However, the cells and their integration into a complete system are still in the development stage. The aim of this master’s thesis is on the one hand to develop an electrochemical model of an RSOC and on the other hand to implement this model into the simulation of a complete plant including balance of plant. The RSOC model allows simulating fuel cell and electrolysis operation at part load and to dimension RSOC-stacks, which means that the number of individual cells connected in series and the number of required stacks is determined (based on cell active area). The operation with different fuel gases can also be simulated. The entire modelling is carried out in the simulation software EBSILON® Professional. Finally, important results, such as the round trip efficiency of the entire energy conversion chain, are discussed at plant level and potentials for further process optimizations are identified.