Energy and Exergy Evaluation of a Solar and Hydrogen Hybrid Electric Aircraft With Energy Storage Support

Decarbonization of the aviation sector would entail the utilization of renewable energy technologies as well as novel thermodynamic approaches to allow performance evaluation of the propulsion systems with regard to operational limitations. The current work proposes an energy and exergy assessment approach, which allows evaluating the energy‐exergy performance of a hybrid solar‐hydrogen propulsion system based on the PEMFC and battery‐assisted Energy Storage concept in the steady‐state condition, specifically, a low‐power UAV‐scale hybrid solar‐hydrogen electric aircraft (≈5.5 kW). Specifically, influences of flight speed and altitude on propulsion power requirements, achievable operational conditions, thermodynamic performance, and power interactions of the proposed hybrid power system were investigated in detail. As shown from the results, propulsion power requirement increases non‐linearly with the increase of flight speed, which is sensitive to cruise altitude. Higher cruise altitude implies lower aerodynamic effect, making it possible for feasible propulsion operation under limited onboard power availability. Considering the adopted low‐power UAV scale, feasible operating range occurs under high cruise altitude conditions with moderate flight speed (about 35–38 m/s) at the height range of 8500–9000 m, whereas operation closer to 40 m/s needs higher cruise altitudes (about 10 000 m). The proposed system exhibits an indicative energy efficiency of approximately 34% and an exergy efficiency of about 29%, highlighting the importance of second‐law losses in propulsion‐system assessment. Component‐level exergy analysis suggests that the fuel cell–battery–electric motor chain constitutes a comparatively influential source of thermodynamic irreversibility under the adopted conceptual assumptions. Furthermore, photovoltaic–fuel‐cell hybridization improves propulsion continuity and operational reliability by mitigating the intermittency associated with solar‐energy availability through complementary power sharing and battery‐assisted energy buffering.