SOFC components testing in a system context

The efficiency and power output of a SOFC stack strongly depend on fuel composition, type of reforming process, thermal management and operating conditions of the SOFC system. To investigate the influence of these parameters and system options on stack output, a flexible SOFC test system for biogas as well as methane operation was built. The test system has a rated power output between 1 and 2 kWel and is equipped with extensive instrumentation in order to investigate heat and power balances. All system components were designed in accordance with a focused system modeling and simulation strategy. For the verification of simulation results and the analysis of operational parameters separate tests on the system's main components (stack, flexible fuel reformer, porous media afterburner) were performed in particular test rigs. The results in the final system prototype show that small SOFC systems can successfully be operated using flexible fuel processing from partial oxidation to autothermal reforming in a single setup. It was found that the power output of stack and the ability of the reformer to run in autothermal mode is a function of water content and methane concentration in the biogas. Using 30-cell stacks based on Ducrolloy bipolar plates (Plansee S.E.) and novel electrolyte supported cells (Kerafol GmbH), efficiencies as high as 31,5 % (DC, gross) were achieved at stack fuel utilizations of 80 % using a synthetic biogas feed with a methane content of 60 %.