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Hybrid combinations of solid oxide fuel cell and recuperated micro gas turbines can convert the chemical energy of hydrocarbon-based fuels in electrical energy with high electrical efficiency. With an integrated and improved cycle management, more than 70% of the energy content of the fuel could be converted. Therefore, the systems are highly suitable for the Power-To-Gas conversion. In particular, a pressure charging of the SOFC fuel cell leads to an increase in stack performance. By a downstream turbo set, after residual fuels are intentionally oxidized with an afterburner, additional electrical energy can be gained from the expansion of the hot exhaust gas stream and the overall efficiency can be increased. In order to increase the electrical efficiency of the system, it is proposed, to ensure the required compression of the process air in particular by a-two-staged turbo compressor with an intermediate cooling system. By thus achievable reduction of the dissipation of the compressor and by targeted condensation of finest drops in front of the second compressor stage affected by intermediate cooling, an increase in efficiency of the system is possible. This is achieved by targeted cooling of the process air behind a low pressure compression, so that it is saturated over 100% relative air humidity. As a result, a slightly supersaturated airflow is available for the second compressor stage, which enters the compressor after heat removal via an intermediate cooling having a small number of microdroplets. Therefore, the condensed water evaporates again by the heat of compression in the second stage and the compressed flow ultimately enters the recuperation at a lower temperature than during normal compression. Thus, more heat can be recovered within the recuperation system. Therefore, the electrical energy of the system can be produced having higher efficiency, because the heat dissipation of the overall system decreases. In this article it is presented, how such a process is thermodynamically modelled and how a technical realization can be built after optimization by simulations. Finally, in this study, the process-influencing factors are analyzed to show the highest possible electrical yield of such a system.

Simulations of various modifications and technical solutions to improve the energy yield when connecting micro gas turbines and SOFC high-temperature fuel cell systems are presented. Above all, heat integration measures enable an increase in system efficiency and a reduction in primary energy input. On the basis of analysis of efficiencies and the heat output it is shown, which high influence the modifications for the improvement of the hybrid process have on the energy yield. Finally, an optimal configuration is worked out, which enables primary energy to be used with the highest possible efficiency. Particular emphasis is placed on the use of gaseous fuels from renewable energy sources. Preparation mechanisms, e.g., the reforming of used methane, and the improvement of the heat insulation materials was also taken into account. All in all, electrical total efficiencies for the optimized hybrid system of more than 65 % could be proven and additional thermal energy for heating purposes was extracted. Overall efficiency for the utilization of the energy content of the primary energy of up to 95 % was then achieved. Entire systems with a maximum system output of around 270kW were examined. In the near future, these plants can replace existing fossil-fuel power plants. Due to the achievable flexibility, the previous security of supply and load fluctuation compensation can also be performed.