SOFC20 – Development of a CFY stack platform technology for stationary SOFC systems in a 5 to 50 kW performance range

To achieve this, the testing parameters of a stable system operation were set at over 1,000 h with an electrical output ≥ 5 kW at a system efficiency of ≥ 50 % as an overall objective for the project. Using a CFY stack platform technology for the 5 to 100 kW+ performance range, a SOFC system was configured with higher efficiency and performance in line with the objectives outlined, in which the following priorities were pursued:

• Construction of a module with several, serially-connected CFY stacks
• Internal reformation
• Pre-reforming with steam from high temperature anode gas recycling

Through the development and use of new materials (interconnectors, protective coatings, MEA electrodes, glass solders) and the optimisation of the manufacturing process, CFY stacks can be built in a reproducible way with an increased stack performance of up to 850 W per stack. At the beginning of the project, 800 W per stack was the technical standard. Robustness and service life were proven in ongoing endurance tests. During a test period of 18,000 h to date, a degradation of < 0.7 %/kh at 35 A and a combustion gas consumption of 75 % has been determined. The stack module, which supplies the required voltage level as well as the necessary power, was a completely new development. By means of the simulations carried out at AVL GmbH and the Forschungszentrum Jülich, a particularly simple and efficient system could be designed through the use of hot anode gas recirculation (up to 600°C), among others. BoP components (e.g. ignition boilers, reformers, etc.) were successfully built, tested and finally integrated in the system. In particular the very compact blowers for the anode gas recirculation as well as for the cathode-side air supply achieve a high efficiency and service life and were tested for the first time globally in system operation. The required number of start/stop cycles of hydro-dynamic blowers (up to 120,000 U/min) was thus successfully proven. After three iteration stages and a component optimisation, the system was operated for over 1,000 h without degradation. The operating data of all system components were very much consistent with the results of the individual tests. The net peak capacity of 5.1 kWel,DC as well as a net efficiency of 46 %el,DC were demonstrated. An additional system analysis showed that the increase in stack module efficiency, the decrease in heat losses and the recirculation rate will lead to over 50 % efficiency. The system costs for mass production were evaluated by partners. The simplicity of the system and the minimal number of components will provide in future for inexpensive system manufacture.