Performance Evaluation of an Anode-Supported SOFC Short-Stack Operating with Different Fuel Blends as Stationary-CHP System

In the perspective of the transition of gas grids towards hydrogen/natural gas blends or even pure hydrogen, Solid Oxide Fuel Cells “SOFC” could play a crucial role as efficient and clean stationary Combined Heat and Power systems, flexibly operating on different feedstocks. A solid oxide fuel cell short stack is analyzed experimentally under different fuel gas compositions which emulate different gas grid transition scenarios. The testing campaign is defined with the aid of a preliminary system-level simulation which assesses system architecture and operating strategy (off-gas recirculation, external reforming, etc). Experimental tests (polarization curves and performance/efficiency maps) are run in different operating conditions in terms of fuel utilization and temperature in three gas composition scenarios. To assess the efficiency of the SOFC unit under the different feedstock operation, different formulations of stack and system efficiencies are proposed and analyzed, based on the boundary conditions considered for the input/output energy streams. Experimental results were key to evaluate the different efficiency definitions proposed; albeit the highest voltage/power is obtained with the 100% H2 scenario, the efficiency may be higher with 100% NG and blend scenarios, due to the lower energy content of the input fuel.