Sustainable Aircraft Propulsion With Four Energy Sources

In response to the aviation sector’s decarbonization goals, particularly the European Union’s 2050 net-zero target, this study proposes an advanced hybrid-electric propulsion system for regional aircraft integrating four energy sources to enhance energy efficiency and environmental sustainability. Building upon a prior three-source model comprising a gas turbine, a hydrogen fuel cell, and one lithium-ion battery, this work introduces a second battery to create a four-source Serial-Parallel-Partial Hybrid (SPPH) architecture. The powertrain includes two 2,550 kW gas turbines (specific fuel consumption: 0.213 kg/kWh during cruise), two 1,500 kW hydrogen fuel cells (55% peak efficiency), and two lithium-ion batteries: a power-oriented 100 kWh unit (C-rate: 2 h⁻¹, 96% efficiency) designed for transient power demands, and a 300 kWh energy-optimized unit (C-rate: 0.33 h⁻¹, 96% efficiency) intended for steady operating phases such as cruise. A throttle-based control algorithm dynamically allocates power among the different energy sources according to mission requirements, ensuring optimal energy management and thermal balance. Simulations of regional aircraft missions demonstrate the advantages of the proposed configuration compared with its three-source predecessor. The dual-battery system enables targeted energy deployment: the high-power battery supports takeoff and climb phases, while the energy-oriented battery sustains cruise operations, reducing gas turbine and fuel cell loads during transient conditions. This results in lower fuel consumption, reduced thermal peaks, and extended component lifetime. Furthermore, the architecture improves redundancy, fault tolerance, and overall system resilience. Environmental benefits include reduced CO₂ and NOₓ emissions enabled by the integration of hydrogen fuel cells and the strategic reduction of gas turbine utilization. Compatibility with renewable energy sources for battery charging and hydrogen production further strengthens the sustainability potential of the proposed system. The four-source hybrid-electric architecture therefore represents a promising pathway toward cleaner regional aviation, offering enhanced efficiency, operational flexibility, and improved integration with future green energy infrastructures.