Fuel Cells – Solid Oxide Fuel Cell | Cells and Stacks

A thermodynamic analysis is developed to predict the maximum possible conversion efficiency (i.e., from available energy in a fuel to electrical output) for solid-oxide fuel cells (SOFCs). Efficiency is represented as the product of three factors (reversible efficiency, part-load efficiency, and fuel utilization), all of which can be evaluated thermodynamically and are independent of the particular membrane–electrode assembly (MEA) structure and stack design. Power density, however, depends upon details of the MEA architecture and losses arising from cell integration in stack. Optimal SOFC design and operation usually depend upon practical trade-offs between efficiency and power density. The functioning of a complete fuel cell system depends upon the contributions of supporting balance-of-plant components (e.g., fuel-processing reactors and heat exchangers). A thermodynamic analysis, based upon energy availability (exergy), is used to evaluate the integrated system performance. Because of unavoidable losses in the balance-of-plant components, the system-level efficiency is significantly lower than the efficiency of the SOFC itself. Careful integration of the SOFC with supporting components is necessary for overall system performance.