Operating results of the SOFC20 stationary SOFC CHP system using a CFY-stack platform
Operating results of the stationary SOFC CHP system jointly developed within the project ""SOFC20"" by Plansee, IKTS, FZJ, Schott and AVL will be shown. The system is based on a CFY-stack platform with chromium based (CFY) interconnects and electrolyte supported cells. The successful development of all stack components i.e.: interconnect (Plansee), cells (IKTS), glass sealing (IKTS and Schott), protection- and contact layer (IKTS) enables robust, redox stable stacks with a low degradation rate. The stacks were arranged to modules of eight 30-cell stacks and were electrically connected in series. Uniform gas and air distribution were simulated with CFD tools and reproduced in tests. The stack module was tested at a test rig at IKTS and showed good results. Stationary power points were measured to compare the behavior of the stack module to the system test at AVL. For an optimized start of the system a procedure for a start of the stack module with CH4 containing reformate was determined. After shipping the stack module was tested in the system at AVL in Graz and showed comparable results. AVL as the system integrator operated the system at 3 - 6 kWel for more than 1000 h at an efficiency of ~56 %DC. The system was operated at ~830 °C up to a current output of 36 A. During this testing period the stack module has shown no observable degradation. The natural gas driven system is equipped with an anode gas recirculation cycle using a hot anode gas blower to enable steam reforming during load operation without an external steam supply. The blowers use hydrodynamic bearings and were successfully operated at 600 °C gas temperature with a significant amount of start/stop cycles showing no degradation. By controlling the rotor speed of the blower the recirculation ratio could be adjusted in a wide range. An exhaust gas heated steam reformer was used to control the reforming temperature and thus influence the methane content at the stack inlet. The results of operation of the stack module under lab conditions and in the real system are in a good agreement. The module performance in terms of cell voltages, stack temperature distribution and fuel utilization under methane reformate fuel will be shown.