Pressurized SOFC for the integration in a hybrid power plant

Kurzfassung

With the increasing demand for flexible power in Europe and especially in Germany, the need for distributed efficient power plants and renewable energy sources is growing further. Hybrid power plants consisting of a gas turbine coupled with pressurized solid oxide fuel cells (PSOFC) can help to meet this demand. They offer the opportunity to convert chemically bound energy into electrical energy with high electrical efficiencies within a large range of installed power. Due to their high operating temperature, they are suitable for combined heat and power applications. Furthermore, they can be operated with a variety of different gases. The German Aerospace Center (DLR) is going to build a demonstration hybrid power plant. The electrochemical behaviour of the pressurized SOFC was examined in a wide range of operating conditions during the preliminary phase. The hybrid power plant will be operated with natural gas as fuel therefore many investigations with pre-reformed methane as fuel have been carried out. Results showed that cell performance is strongly influenced by methane concentration. In this paper, this effect is analyzed in detail using electrochemical impedance spectroscopy (EIS). It is found that the influence of methane concentration on cell performance is mainly due to a change in temperature. High methane concentrations lead to high internal reforming rates and therefore a significant cooling of the stack. It was found that by controlling the temperature within the stack and keeping it constant for different fuels similar performance results can be obtained.