A simple thermodynamic system model for the analysis and evaluation of possible SOFC system concepts with regard to reachable electric efficiency is presented. All reforming concepts, various available fuels and anode off‐gas recirculation are included in the model. Furthermore, the model allows the characterization of the reforming conditions necessary to reach the calculated and desired electric efficiencies by the use of two dimensionless energy flow ratios, which are introduced. It is presented how to quickly assess system concepts and identify system concepts that are particularly interesting due to a simple process, high electric efficiency, or preferably a combination of those. Within the experimental section, the model is used to support the system design process of a biogas‐driven SOFC system with partial oxidation as reforming concept, without anode off‐gas recirculation. Since adjustable operating parameters are input into the model, the parameters' influence on efficiency and reforming conditions can be analyzed. With the model real system effects are investigated making it possible to reach a maximum gross electric efficiency of 0.55 with the real designed system.

Biogas is an attractive fuel for solid oxide fuel cell applications because of the high CO2 content. Its composition allows a high electrical efficiency without adding external water to the system. Because of the CO2 reforming reaction only a very small amount of air is needed for partial oxidation, which is why the process could be called oxidative dry‐reforming. Herein, this concept is demonstrated by a thermodynamic analysis of the process and experimental system and component results. In order to realize a high yield of electrical power from the SOFC stack, a large flow of chemical energy into the stack is needed. To achieve this goal the efficiency of the reforming process is essential. With optimized reforming conditions it is possible to increase the chemical energy content of the fuel by adding an ample amount of heat to the reforming step. To achieve this in practice, the necessary heat flow to the reformer has to be calculated for a given operating temperature. Based on these thermodynamic calculations a reactor was built and tested. After successful laboratory tests the reactor was integrated into an SOFC system, where the necessary heat for the reforming step was supplied by the afterburner. The results of the component tests were verified under system conditions. Based on this system concept a high value for the electrical efficiency (ηel>0.5) of the system was achieved.

No abstract

A reformer-afterburner unit for integration into a solid oxide fuell cell system is introduced. Synthesis gas of high energy density can be produced by oxidative dry reforming of biogas. The required heat for the reforming can be provided by internal heat use. Subsequent to component testing, the unit is integrated into a solid oxide fuel cell system. The electrical efficiency of the system confirmed the results of a conducted thermodynamic analysis