There are several changes underway that are set to make a long term difference to the environmental footprint of the aviation industry. Sustainable Aviation Fuel (SAF) is having the biggest difference currently, and electric propulsion is making progress with small aircraft.
Looking further ahead, and in particular with larger aircraft, hydrogen power is likely the most promising development. This took a big step forward recently with Rolls -Royce and airline partner easyJet successfully testing its first hydrogen fuelled aircraft engine.
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Rolls-Royce and the AE 2100 engine
Engine manufacturer Rolls-Royce presented its AE 2100 hydrogen fuelled test engine in September 2022, and followed this up in late November with the news that it had been successfully ground run. This is the first time globally that a modern aircraft engine has been operated using hydrogen as a fuel source.
The AE 2100 used in the tests is a modified turboprop engine (currently used in a range of aircraft including the Lockheed Martin C-130 Hercules transport and the Saab 2000 regional aircraft). The engine technology remains the same, but it has been modified to take hydrogen rather than jet fuel / kerosene as a fuel source.
These are early-stage tests. The engine in this case has been run at low power on the ground, taking place on a test rig at the UK Defence Ministry’s Boscombe Down facility.
Working in partnership with easyJet
The Rolls-Royce project is being carried out in partnership with easyJet. The airline is interested in decarbonization and the potential of hydrogen power long term, even though initial aims of the project will be for smaller aircraft than it currently operates. Rolls-Royce states the aims of the project as developing potential hydrogen power sources for small and medium sized aircraft by the 2030s.
Speaking about the partnership and its aims, Rolls-Royce CTO Grazia Vittadini explains:
“Rolls-Royce engines are made to fly, and our ambition is to take this technology to the air and indeed power a whole range of aircraft. easyJet and Rolls-Royce are absolutely on the same page on this. We both signed the UN Race to Zero campaign, and we’re absolutely determined and excited to join that race next to easyJet as they sprint to really decarbonizing the skies and having a net zero future.”
Green commitments from hydrogen
One of the challenges of hydrogen use is the production and supply of the fuel. This is something that Rolls-Royce is also addressing in these tests. It is using so-called “green hydrogen” produced without the need to burn fossil fuels. For a true zero-emission future, this is important.
For these tests, hydrogen from the European Marine Energy Centre (EMEC) was used. This is generated using renewable energy from a tidal based facility in the UK’s Orkney Islands.
There are many more aspects of hydrogen fueling that the tests will help to research. These include the practicalities of feeding hydrogen to an engine, the process of burning hydrogen, and the emissions produced (including water instead of carbon dioxide as a by-product, and potential nitrogen oxides).
Taking hydrogen tests further
The joint Rolls-Royce and Airbus project has plans to expand testing to the Pearl 15 jet engine next. This is found on many jets, including the Bombardier Global 5500 and Global 6500.
These tests are planned to take place in the US, but no timeframe has yet been released. Pearl 15 tests will include a more representative integrated hydrogen fuel and combustion system.
All the hydrogen tests so far are planned as ground tests. The next phase of course will be to take to the air, but we don’t yet know when this will happen. Ground testing with engines can go a long way to prove use and performance, however.
Rolls-Royce is not the only manufacturer working on hydrogen projects. CFM International has a project underway to modify a GE Passport turbofan engine to run on hydrogen. Testing of this will take place in partnership with Airbus on an Airbus A380 test bed fitted with liquid hydrogen tanks. A schedule for this testing has not been released, but engine development is part of Airbus’ ZEROe project to have a zero-emission aircraft flying by 2035.
Final Thoughts
Hydrogen is gaining momentum in the aviation industry as a future possibility for large scale use. This will need many changes, including to aircraft design and to airport infrastructure and fueling procedures. Engine development is an early, but vital, part of this. With participation from airlines and manufacturers too, this is heading in the right direction.
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