Hydrogen-powered aviation has moved closer to reality in 2022, with recent announcements from major aerospace companies Rolls-Royce and Airbus. Ground tests for hydrogen engines are underway, but there are still significant hurdles to overcome before emissions-free commercial aviation can progress.
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Commercial Aviation’s Environmental Impact
Commercial air transport as it exists today poses a serious threat to the world’s agreed emissions targets.
Aircraft contribute 2.4% of all anthropogenic carbon dioxide (CO2) emissions. Combined with other gas emissions and water vapor trails from aircraft, they are responsible for approximately 5% of global warming effects.
Developing technological innovations reduces the environmental impact of aviation. New technologies in development focus primarily on propulsion technologies, such as electric aircraft, or new fuels, such as hydrogen.
Is Hydrogen Sustainable?
Hydrogen (H) is a fuel that reacts with oxygen (O2) to burn and release usable energy, just like carbon (C).
Unlike C, which emits CO2 due to its energy-releasing interaction with O2, H only releases harmless water (H2O) vapor with a small amount of nitrogen.
As hydrogen fuel can release as much energy as carbon-based fuels such as petroleum and gas, it is considered a viable means to eliminate CO2 emissions from “heavy” industries with high energy demands, including shipping, mining, and aviation.
However, pure hydrogen is rarely available due to its high reactivity.
Hydrogen fuel must be derived from other sources in energy-intensive processes. Steam methane reforming (SMR) is the most common form of hydrogen fuel production, but this consumes finite natural gas (composed of methane, CH4), releases CO2, and requires large amounts of energy.
Water electrolysis is a method for producing hydrogen fuel from H2O. It is highly energy intensive, requiring more energy to produce than is available from the fuel product.
The resulting fuel can be considered emissions-free if entirely renewable sources power water electrolysis. This is referred to as green hydrogen, which makes up approximately 1% of all hydrogen produced.
New Hydrogen Developments in the Aviation Industry
Two recent announcements have brought hydrogen-powered aviation one step closer to reality.
Aerospace engine manufacturer Rolls-Royce, in partnership with the commercial airline easyJet, recently completed ground tests for a jet engine specially designed to run on hydrogen fuel.
The hydrogen fuel used in these tests was generated with renewable wind and tide energy at a facility in the UK’s Orkney Islands off the north coast of Scotland. This was entirely green hydrogen, and the ground tests successfully delivered jet power with no CO2 emissions.
Soon after Rolls-Royce’s successful ground test, aircraft manufacturer Airbus announced that ground and air testing of a new hydrogen-fueled architecture would commence soon, with ambitions to achieve zero-emission commercial aviation by 2035.
Do These Hydrogen Aircraft Developments Matter?
Developments such as these are essential as green hydrogen only accounts for approximately 1% of all hydrogen fuel in production today.
As technologies using hydrogen fuel at commercial scales develop, the demand for green hydrogen can be expected to increase. This increasing demand can lead to more investment in green hydrogen production, which could lead to green hydrogen taking up a larger share of all hydrogen production in the future.
Is Hydrogen Development Being Held Back?
Hydrogen fuel cell technology is not particularly new or complicated. With the potential for emissions-free propulsion, some may question why hydrogen is not already replacing carbon fuel sources in heavily polluting industries such as aviation.
This results from market forces that make hydrogen production investment a risky endeavor, with no clear route to profitability in the short term.
However, this is not the case worldwide. Europe is a world leader in hydrogen-fuel technology development, and the recent announcements by three European aerospace companies contribute to and benefit from this prime position.
The European Commission is playing its role in hydrogen development in the continent, and public intervention is likely also needed in markets such as the United States to catch up.
When Will Hydrogen-Powered Aviation Progress?
There are still several technological challenges to overcome to make hydrogen aviation a reality, as well as the economic challenges discussed above.
Storage systems cannot carry enough liquid hydrogen in aircraft safely for long-haul flights, and transporting hydrogen fuel from production facilities to airports is challenging.
The industry and government bodies need to develop new standards, codes, and regulations to make hydrogen-powered aviation as safe as other forms of flight.
Integration is the major conundrum facing the industry. While discrete parts of a hydrogen-powered plane are already being tested (such as engines), combining these with the rest of the plane architecture is a serious challenge. As well as designing planes to carry and use hydrogen fuel, manufacturers must design or re-design manufacturing processes to make them.
What Will Hydrogen-Powered Aviation Look Like?
If all of these challenges are overcome, and there is a steady supply of green hydrogen available, then emissions-free flight could become a reality.
Total CO2 emissions from the aviation industry, including manufacturing and other “upstream” emissions, could be reduced by up to 50%.
Drastic emissions reductions such as these could decrease the need to fly less to meet net-zero emissions targets in the next few decades.
Continue Reading: Is Emission-Free Aviation Possible?
References and Further Reading
Bellwood, O. (2022) Airbus Will Test Hydrogen Fuel Cell Engines on the First A380. [Online] Jalopnik. Available at: https://jalopnik.com/airbus-will-test-hydrogen-fuel-cell-engines-on-the-firs-1849846726 (Accessed on 12 December 2022).
The green hydrogen ecosystem for aviation, explained. (2021) [Online] Airbus. Available at: https://www.airbus.com/en/newsroom/news/2021-06-the-green-hydrogen-ecosystem-for-aviation-explained (Accessed on 12 December 2022).
Gössling, S., S. Dolnicar (2022) A review of air travel behavior and climate change. WIREs Climate Change. doi.org/10.1002/wcc.802.
Hydrogen. [Online] Airbus. Available at: https://www.airbus.com/en/innovation/zero-emission-journey/hydrogen (Accessed on 12 December 2022).
Marquis, E. (2022). Rolls-Royce Performs Successful Test of World's First Jet Engine Fueled by Green Hydrogen. [Online] Jalopnik. Available at: https://jalopnik.com/airlines-always-happy-to-raise-ticket-prices-upset-ab-1849877144 (Accessed on 12 December 2022).
O’Callaghan, J. (2020). Quiet and green: Why hydrogen planes could be the future of aviation. [Online] EU Horizon. Available at: https://ec.europa.eu/research-and-innovation/en/horizon-magazine/quiet-and-green-why-hydrogen-planes-could-be-future-aviation (Accessed on 12 December 2022).
Pilkington, B. (2022). What is the Difference Between Green Hydrogen and Blue Hydrogen? [Online] AZO Cleantech. Available at: https://www.azocleantech.com/article.aspx?ArticleID=1525 (Accessed on 12 December 2022).
Rolls-Royce and easyJet set new world first. (2022) [Online] Rolls-Royce. Available at: https://www.rolls-royce.com/media/press-releases/2022/28-11-2022-rr-and-easyjet-set-new-aviation-world-first-with-successful-hydrogen-engine-run.aspx (Accessed on 12 December 2022).
TImperley, J. (2020). Should we give up flying for the sake of the climate? [Online] BBC. Available at: https://www.bbc.com/future/article/20200218-climate-change-how-to-cut-your-carbon-emissions-when-flying (Accessed on 12 December 2022).