Reviewed by Lexie CornerNov 4 2024
While electric and hybrid vehicles are making transportation greener, other sectors, like aviation, continue to contribute significantly to CO2 emissions. Researchers are exploring hydrogen-powered airplanes as a potential solution. Recent research published in ACS Sustainable Chemistry & Engineering uses computer modeling to investigate the viability and challenges of hydrogen-powered aviation.
Additionally, older technologies are being revisited to improve environmental sustainability, such as the resurgence of sailing ships in shipping and innovative uses of hydrogen in aviation.
While there is a long way to go for hydrogen aviation to be realized at scale, we hope that our analysis of both onboard system design and enabling infrastructure will be used to prioritize development efforts.
Dharik Mallapragada, MIT Energy Initiative, Massachusetts Institute of Technology
The International Energy Agency reports that aviation sector CO₂ emissions from energy use have risen more rapidly than those of rail, road, and shipping over recent decades. To address the potential climate impact of this increase, researchers are working on optimizing aircraft design and operations and developing low-emission fuels like hydrogen, which can be used for direct combustion or to power electric fuel cells.
Hydrogen is an appealing fuel option as it produces zero CO₂ emissions and offers more energy per pound than jet fuel. To evaluate the effects of replacing conventional jet fuel with hydrogen in aviation, researchers Anna Cybulsky, Mallapragada, and colleagues modeled hydrogen’s potential in the electrification of regional and short-range turboprop aircraft.
The team found that the additional weight of hydrogen fuel tanks and fuel cells on existing aircraft would need to be offset by reducing weight elsewhere, such as in the payload (cargo or passengers). This could potentially lead to the need for more flights to transport the same amount of payload.
The team’s model suggests that advances in fuel cell power and improvements in the fuel system’s gravimetric index (the ratio of the fuel’s weight to the total weight of a fully loaded fuel tank) could eliminate the need to reduce payload, thus avoiding the environmental impact of additional flights. Furthermore, they found that transitioning to hydrogen-powered aviation could potentially reduce the industry’s CO₂ emissions by up to 90 %.
However, a more challenging hurdle than switching fuel types may be building the infrastructure needed for low-carbon, cost-effective hydrogen production and distribution. One low-carbon production method is natural gas reforming (extracting hydrogen from methane) combined with carbon capture, but this approach requires access to CO₂ infrastructure and sequestration sites.
Another environmentally friendly option is electrolysis, which splits water into hydrogen and oxygen using electricity from nuclear plants or renewable energy sources. However, this process would substantially increase demand for electrical grids. Cybulsky and colleagues noted that, given the variability in electricity costs across regions, it might be more cost-effective to produce hydrogen at low-cost facilities and transport it to end-users.
The researchers suggest that hydrogen-based aviation could initially launch in regions with favorable conditions for hydrogen production, such as Hamburg, Germany, or Barcelona, Spain. The infrastructure developed to support hydrogen use in aviation could also advance decarbonization in other sectors, like road transport and shipping, by making hydrogen fuel more widely available.
The authors received financial support from the Massachusetts Institute of Technology Energy Initiative Low-Carbon Energy Centers for Energy Storage and Future Energy Systems Center.
Journal Reference:
Cybulsky, A., et al. (2024) Challenges of Decarbonizing Aviation via Hydrogen Propulsion: Technology Performance Targets and Energy System Trade-Offs. ACS Sustainable Chemistry & Engineering. doi.org/10.1021/acssuschemeng.4c02868.