Sustainable propulsion and advanced energy-storage systems for net-zero aviation

Abstract

The transition of the aviation industry toward sustainable propulsion requires transformative shifts in energy systems, storage technologies, and emission strategies. This review critically assesses sustainable aviation fuels (SAFs), hydrogen fuel cells, advanced batteries, and hybrid-electric powertrains in pursuit of net-zero goals. SAFs provide up to 89% lifecycle CO₂ reduction and are compatible with the existing infrastructure but face limitations in terms of feedstock supply, production cost, and global scalability. Hydrogen, with a gravimetric energy density of ∼120 MJ kg⁻¹, exhibits long-term potential but is constrained by cryogenic storage and airframe redesign requirements. Electric aviation has been advancing through lithium-ion, lithium–sulfur (400–600 Wh kg⁻¹), and solid-state chemistries; however, current energy densities limit the range and payload. Hybrid-electric propulsion systems with series, parallel, or turboelectric configurations, exhibit enhanced emission reduction and energy management, particularly when paired with SAFs or hydrogen. Demonstrators such as Airbus EcoPulse, Rolls-Royce E-Fan X, and Ampaire Electric EEL have validated hybrid-electric and SAF feasibility, while hydrogen-powered flights are being advanced by H2FLY's HY4 and ZeroAvia's Dornier 228. Lifecycle assessments show 57–88% per-revenue passenger-kilometer (RPK) emission reduction. Future scalability depends on improved safety, thermal management, recyclability, material innovation, dual certification, and harmonized policies. This roadmap underscores the need for coordinated technological, regulatory, and industrial efforts to realize a resilient and sustainable aviation ecosystem.