| description abstract | Abstract. Hydrogen has emerged as a promising energy carrier for aerospace applications due to its high specific energy and suitability for long-duration missions. Fuel cells (FCs), electrolyzers, and regenerative fuel cell systems (RFCSs) represent key electrochemical technologies within aerospace energy architectures, enabling power generation, gas production, and energy storage. This review examines these three classes of electrochemical systems within a unified, system-level framework tailored to aerospace applications. Fuel cell technologies are reviewed for power generation in applications such as landers, aircraft, unmanned aerial vehicles (UAVs), auxiliary power units (APUs), and stationary backup systems. Proton exchange membrane (PEM) electrolysis is discussed as a viable approach for hydrogen and oxygen production to support both terrestrial infrastructure and onboard aerospace operations. Regenerative fuel cell systems, which integrate an electrolyzer and a fuel cell to enable cyclic energy storage, are then evaluated as advanced energy storage solutions. A system-level comparison between RFCSs and state-of-the-art, space-qualified lithium-ion battery systems is presented based on reported specific energy, system mass, and discharge-duration data. The analysis highlights that RFCSs offer advantages in specific energy and total system mass under long discharge-duration conditions, making them particularly suitable for extended aerospace missions. Key technical challenges and design considerations, including system integration, energy density, and operational performance, are also discussed. Overall, this review provides a coherent assessment of electrochemical energy systems and clarifies the potential role of regenerative fuel cell technologies in future long-duration and sustainable aerospace energy applications. | |
