Energy efficiency of a microtubular solid-oxide fuel cell

► Showing the correlation between single cell performance and its energy efficiency. ► High energy efficiency of over 40% can be achieved in a single SOFC operation. ► Limiting factor of the efficiency at lower temperature was mainly due to gas transport. Energy efficiency of a single solid-oxide fuel cell (SOFC) has been studied in various experimental conditions and directly correlated to the character of the cell. A microtubular cell, which has the exact geometry for stack/module application, is used for this study. The energy efficiency simply improves by increasing the operating temperature, and reaches over 40% (lower heating value: LHV) at the operating temperature of over 700 °C in flowing 20% H 2–Ar fuel inside the tube. Impedance analysis has shown that the gas transport is the limiting factor for improving the energy efficiency at lower operating temperatures.