1. The Challenge of Decarbonization for Aviation
The aviation sector accounts for 2.5%-3% of global CO2 emissions. Since the 1960s, fuel efficiency has improved, but air traffic growth has increased emissions. In response, the International Civil Aviation Organization (ICAO) and industry bodies like IATA have set net-zero carbon targets for 2050.
In 2022, ICAO adopted the Long-Term Aspirational Goal (LTAG) for net-zero emissions by 2050, supported by aircraft technology improvements, innovations in electric propulsion systems, sustainable aviation fuels (SAF), and improved air traffic management. The European Union’s “Fit for 55” package aims to reduce greenhouse gas emissions by 55% by 2030. The gradual phasing out of free allowances in the EU Emissions Trading System (ETS) and initiatives like RefuelEU Aviation aim to increase SAF usage and electrification.
Source : ICAO
The European Union Aviation Safety Agency (EASA) and Federal Aviation Agency (FAA) are actively adapting regulations to accommodate new propulsion systems like electric and hydrogen. EASA has introduced “Special Conditions” to ensure that regulations are technology-agnostic, paving the way for for electric and hybrid aircraft to enter the market.
Key stakeholders like Airbus are advancing projects such as the ZEROe hydrogen-powered aircraft and SAF-compatible planes. Europe is positioning itself as a leader in zero-emission aviation, driven by initiatives like the Alliance for Zero-Emission Aviation (AZEA), which seeks to align the industry and policymakers to achieve net-zero goals. Achieving full decarbonization by 2050 will require overcoming challenges, including SAF costs and technological advancements in propulsion and efficiency. SAF and hydrogen alone cannot fully reduce CO2 emissions; a combination of electrification, hybrid systems, and operational improvements will be needed. The collective efforts of regulators, manufacturers, airlines, and governments are essential to meet decarbonization targets.
2. Decarbonization by Market Segment
General Aviation:
General aviation includes all flights other than military and commercial airlines, such as private flying and air sports. Due to smaller aircraft and flexibility, general aviation is positioned to lead decarbonization with electrification and hybrid technologies. For example, the Pipistrel electric aircraft is already being used in pilot training and recreational flying, showcasing the potential of electric propulsion. Flight schools still use to this day old aircraft, some being even older than their pilots. By 2035, some fleet renewal will be required and many general aviation aircraft are expected to be fully electric or hybrid.
Business Aviation:
Business aviation, which includes corporate and personal jets, will focus on SAF as a short-term solution, with electrification and hybrid technologies integrated by 2040. Integration of Lithium-ion batteries and electric propulsion systems will be crucial for short-range flights, reducing emissions without sacrificing convenience.
Regional Aviation:
Regional aviation, serving routes with 20-100 passengers, represents a prime opportunity for hybrid electric aircraft and hydrogen propulsion systems. Electric and hydrogen propulsion could significantly reduce aviation’s CO2 emissions on short and medium-haul flights, offering a cost-effective solution compared to other options. By 2035, hydrogen-powered regional aircraft are expected to be in service, and by 2050, many regional flights will be low-emission. Projects like the EVO concept by ATR aim to reduce fuel consumption and emissions by 20%, incorporating mild hybridization. Electric and hydrogen propulsion could reduce emissions on short and medium-haul flights by up to 43 megatonnes of CO2 annually by 2050, significantly impacting regional aviation. Shorter flight routes make regional aviation ideal for hybrid-electric propulsion, which allows for smaller battery packs and frequent recharging.
Source : ATR
Urban Air Mobility (UAM):
UAM, including electric vertical take-off and landing (eVTOL) aircraft, aims to provide a new layer of low-emission urban transportation. Commercial operations are anticipated to begin by the late 2020s. These aircraft rely on compact and lightweight aviation battery models, using the densest of lithium-ion chemistries such as high nickel content NMC. Challenges include regulatory approval, infrastructure development, and public acceptance. The CityAirbus NextGen, presented in 2024, aims to be a pioneering eVTOL for sustainable urban travel, with a range of up to 80 km and a top speed of 120 km/h.
Commercial Aviation:
Commercial aviation will focus on hydrogen and hybrid-electric propulsion systems for regional flights, while larger aircraft will rely on SAF. Airbus plans to have 100% SAF-compatible aircraft by 2030 and introduce hydrogen-powered planes by 2035. SAF, though crucial, must be complemented by other technologies due to limited availability and high costs. Hydrogen-powered aircraft are expected to gradually increase their share of regional flights as infrastructure develops.
Electrification will begin with lighter aircraft on short-haul routes. For larger planes, hydrogen fuel and SAF will play key roles due to their higher energy density. Hybrid solutions combining electric and conventional propulsion will be important transitional technologies over the next decade. Infrastructure development, including charging stations and hydrogen refueling facilities, will be vital. Collaboration between governments, industry, and research institutions is necessary to create a supportive ecosystem.
Furthermore, electric and hydrogen-powered aircraft offer opportunities to reduce non-CO2 warming effects, such as contrail and cirrus cloud formation, which contribute significantly to aviation’s climate impact.
3. Battery Requirements for Electrification
Batteries are crucial for aviation electrification, especially for small aircraft. However, achieving effective electrification is challenging due to the need for high energy and power density while ensuring safety and longevity. Increasing energy density often compromises safety, as higher-density cells are more prone to overheating. The weight of battery systems also affects aircraft efficiency and range, making it vital to balance energy storage and weight.
Immersion cooling technology is emerging as a superior solution compared to traditional cooling methods, effectively reducing the risks associated with high energy density in battery systems. Unlike traditional air or liquid cooling, which often struggles to manage heat uniformly and prevent localized hotspots, immersion cooling submerges cells in dielectric fluid, providing consistent and efficient thermal management. This approach significantly reduces hotspots that lead to failure, improves performance, and simplifies the cooling system by eliminating the need for complex heat exchangers. Moreover, immersion cooling effectively stops thermal runaway propagation of lithium batteries, which is a major safety advantage.
At EXOES, we have demonstrated that immersion cooling maintains optimal battery temperatures, enhancing safety and prolonging battery life. Through extensive experience, trial and error, and customer projects, EXOES has been able to minimize the amount of fluid used and match the weight of traditional designs, while retaining the performance and safety advantages of immersion. High power density supports rapid energy delivery for take-off and manoeuvring, and immersion cooling meets these demands, making it a key innovation for aviation electrification. Immersion cooling has the added benefit of evening out temperatures in the batteries and reducing overall cell temperatures, leading to longer lifetimes, further reducing the CO2 impact relative to traditional designs.
Advancing battery technology is essential for zero-emission aviation. New chemistries and advanced cooling techniques will be needed to meet the sector’s requirements. Infrastructure will also need to be developed, with the electrification of runways being key for the adoption of fully electric aircraft. Collaboration between aerospace companies, battery designers and manufacturers, and research institutions will help accelerate progress. Additionally, public and private investments in electrification infrastructure, such as runway charging systems, will pave the way for the widespread adoption of electric aircraft. Addressing challenges related to energy density, safety, and weight will enable a future where electric flight is feasible and economically viable, contributing to significant emissions reductions.
Conclusion
The aviation sector is at the forefront of a global transition toward zero-emission transportation, and EXOES is committed to enabling cleaner skies. Our expertise in immersion cooling and battery technology positions us as a leader in supporting the industry’s decarbonization goals.