Despite ongoing efforts to reduce CO2 emissions through electric and hybrid vehicles, other modes of transport still contribute significantly to greenhouse gas emissions. To address this problem, older technologies are being reworked to make them more environmentally friendly, such as the reintroduction of sailing ships to shipping and new applications for hydrogen in aviation. Now, researchers have used computer models to investigate the feasibility and challenges of hydrogen-powered aviation in the journal ACS Sustainable Chemistry & Engineering .
“We hope that our analysis of the onboard system design and the corresponding infrastructure will help set priorities for development,” says Dharik Mallapragada, one of the study’s co-authors.
According to the International Energy Agency, energy-related CO2 emissions from the aviation industry have increased faster than those from rail, road, and shipping in recent decades. To mitigate the potential climate impact of this growth, scientists are improving aircraft design and operation and developing low-emission fuels such as hydrogen, which can be used for direct combustion or to power electric fuel cells. Hydrogen's appeal as a fuel source lies in the fact that its use produces no CO2 and it delivers more energy per pound than jet fuel. To understand the potential impact of switching from conventional jet fuel to hydrogen in aviation, Anna Cybulsky, Mallapragada, and colleagues have calculated the use of hydrogen in the electrification of regional and short-range turboprop aircraft.
The researchers calculated that the additional weight of a hydrogen tank and fuel cells retrofitted to an existing aircraft would have to be offset by weight reductions elsewhere, such as a decrease in the aircraft's payload (cargo or passengers). This could mean that more flights would be required to carry the same payload. However, the team's model suggests that improvements in fuel cell performance and the fuel system's gravimetric index (the weight of the fuel relative to the weight of a full tank) could eliminate the need for payload reduction , thus removing the environmental impact of additional flights. At the same time, they found that switching to hydrogen-powered flights could reduce the aviation industry's CO2 emissions by up to 90%.
A greater challenge than switching to alternative aviation fuels could be providing the infrastructure needed for low-carbon and 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 requires access to CO₂ infrastructure and sequestration facilities. Another environmentally friendly option is electrolysis, which splits water into hydrogen and oxygen and could be powered by electricity from a nuclear power plant or renewable energy sources. However, this would create a significant additional demand for electricity grids. Cybulsky and colleagues pointed out that, due to highly variable regional electricity prices, it might be more cost-effective to transport the hydrogen from a low-cost production facility to end users.
For these reasons, the researchers suggest that the adoption of hydrogen-based aviation could begin in locations that offer favorable conditions for hydrogen production, such as Hamburg, Germany, or Barcelona, Spain. The infrastructure required for the use of hydrogen in aviation would also benefit decarbonization efforts in other industries, such as road transport and shipping, by improving the availability of hydrogen as a fuel.
Original Paper:
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