Improving the efficiency of fuel cell systems for aircraft propulsion: A comparative study of turbo-compressor and conventional systems

In this study, the advantages and limitations of implementing a turbo-compressor system in a fuel cell propulsion architecture were examined. By integrating a turbine into the conventional air supply line, the system recovers exhaust energy, increasing the portion of fuel cell output available for propulsion. The objective is to quantitatively assess the improvement in system efficiency achieved through turbine integration and to identify the operational constraints associated with its use. The KC-100 aircraft manufactured by Korea Aerospace Industries was selected as the modeling target. Two configurations—a conventional compressor-only system and a turbo-compressor system equipped with turbine—were modeled to compare their performance in terms of altitude effects, available propulsion energy, and operational range under identical control conditions. The results show that, over the defined mission profile, compressor motor energy consumption was reduced by 30.44 % when using the turbo-compressor system. This indicates that a greater portion of the fuel cell’s generated energy can be used for propulsion, enabling a more compact and lighter fuel cell system design in terms of the number of cells. However, as the back pressure of the fuel cell is passively determined when a turbine is used, there is a limitation in increasing the internal pressure of the fuel cell to enhance its output performance. This suggests that, when adopting a turbo-compressor system, it may be necessary to incorporate technologies such as variable geometry turbines that can actively regulate back pressure to maintain optimal operating conditions.