With 4.5bn passenger trips taken each year and more than 16mn planes taking off in the US every year, aircraft are responsible for 2.5% of global CO2 emissions, according to the Global Carbon Project, and the problem is growing. One proposed solution rivals the power of fossil fuels without the emissions — hydrogen. With the industry attempting to achieve net-zero emissions by 2050, both big players like Airbus and startups alike are exploring the technology.Hydrogen is a high-potential technology with a specific energy-per-unit mass that is three times higher than traditional jet fuel. If generated from renewable energy through electrolysis, hydrogen emits no CO2 emissions, thereby enabling renewable energy to potentially power large aircraft over long distances but without the undesirable by-product of CO2 emissions.Because hydrogen has a lower volumetric energy density, the visual appearance of future aircraft will likely change. This is to better accommodate hydrogen storage solutions that will be bulkier than existing jet fuel storage tanks.Hydrogen has been safely used in the aerospace and automobile industries for decades. The aviation industry’s challenge now is to take this decarbonised energy carrier and adapt it to commercial aviation’s needs.Aircraft manufacturers like Airbus and Boeing two primary uses for hydrogen:Hydrogen propulsion: Hydrogen can be combusted through modified gas-turbine engines or converted into electrical power that complements the gas turbine via fuel cells. The combination of both creates a highly efficient hybrid-electric propulsion chain powered entirely by hydrogen.Synthetic fuels: Hydrogen can be used to create e-fuels, which are generated exclusively through renewable energy.The UK Civil Aviation Authority has launched a challenge for the aviation industry to help leverage the potential of hydrogen as a zero-carbon emission aviation fuel.The regulator’s challenge will facilitate collaboration with industry and academia to improve understanding of hydrogen-related risks in aviation, identify gaps in policies, and propose new recommendations to develop net-zero policies.Sophie O’Sullivan, Head of Future Safety & Innovation at the UK Civil Aviation Authority, said: "The project will help facilitate efforts to move towards a net-zero aviation sector by supporting the industry to explore how feasible the introduction of hydrogen is and how we can make sure regulation is fit for purpose."Enabling innovation while maintaining safety is a key part of our work and this challenge is a clear example of our collaborative approach to shaping the future of aviation."Introducing hydrogen propulsion is key to achieving the Government’s Jet Zero Strategy and is also a key deliverable for the UK Civil Aviation Authority’s sustainability strategy.The Hydrogen Challenge is funded with nearly £940,000 from the Regulators' Pioneer Fund, which is overseen by the Department for Science, Innovation, and Technology.The Fund is a grant-based fund to enable UK regulators and local authorities to help create a UK regulatory environment that encourages business innovation and investment.Airbus has already modified a superjumbo A380 to test a hydrogen-powered jet engine as the European aerospace group prepares to bring a zero emissions aircraft into service by 2035. The partnership is an agreement with CFM International, a 50/50 joint company between GE and Safran Aircraft Engines, to develop an engine that can run on hydrogen. The converted test aircraft, the A380, will fly by the end of 2026.The programme’s objective is to ground and flight test a direct combustion engine fuelled by hydrogen, which Airbus is betting on to enable the company to decarbonise in line with aviation’s climate change goals. The A380 flying test jet will be equipped with liquid hydrogen tanks prepared at Airbus facilities in France and Germany. Airbus will also define the hydrogen propulsion system requirements, oversee flight testing, and provide the A380 platform to test the hydrogen combustion engine in cruise phase.CFM International will modify the combustor, fuel system, and control system of a GE Passport turbofan to run completely on hydrogen. The engine itself will be mounted along the rear fuselage of the A380 test jet to allow engine emissions, including contrails, to be monitored separately from those of the engines powering the aircraft."This is the most significant step undertaken at Airbus to usher in a new era of hydrogen-powered flight since the unveiling of our ZEROe concepts back in September 2020," said Sabine Klauke, Airbus Chief Technical Officer. "By leveraging the expertise of American and European engine manufacturers to make progress on hydrogen combustion technology, this international partnership sends a clear message that our industry is committed to making zero-emission flight a reality."The venture comes amid increasing pressure on the aviation industry to cut pollution and meet zero-emission targets by 2050. Before the pandemic led to the grounding of much of the world’s aircraft, aviation accounted for roughly 2.4% of global emissions. "To achieve these goals by 2050 the industry has to take action now and we are," said Gael Meheust, chief executive of CFM."Is hydrogen harder? Yes. Is it do-able? Absolutely," said Mohamed Ali, vice-president and general manager of engineering at GE Aviation.Executives said the decision to use an A380, the world’s largest passenger airline jet that has been phased-out at many airlines around the world due to its inefficiencies, would allow engineers more room for things like the tanks and the testing equipment. A commercial product available to airlines over the coming years will be much smaller. Airbus is expected to initially produce a regional or shorter-range aircraft.In today’s aircraft, wings are where the fuel is stored, and they are in no way large enough to store the hydrogen that would be needed for a long flight. Hydrogen planes of the future could have extra-large fuselages, but more likely they will be what’s called blended wing, in which the planes are shaped like large triangles. This would allow them to store more fuel, but also reduce fuel consumption to make the aircraft aerodynamics even better.Planes using hydrogen would emit only water, and initial tests suggest they can be just as fast as traditional planes, carrying more than a hundred passengers per flight over thousands of kilometres.Most of the world’s hydrogen today is produced by reforming methane from natural gas – a fossil fuel - which produces carbon dioxide. Efforts are underway to develop green hydrogen by using an electric current from a renewable source to convert water into oxygen and hydrogen and reduce emissions in its production. If that is possible, along with no emissions from the planes themselves, aviation could become a green form of travel.There are significant challenges that remain. If Europe were to fully achieve the environmental benefits of hydrogen-power – for example, for air travel, the production of clean – or green – hydrogen needs to be dramatically scaled up. Clean hydrogen is produced from water using an electric current from a renewable source, rather than from fossil fuels. Today only a tiny fraction of hydrogen used in Europe is categorically "clean."Hydrogen is a high-potential technology with a specific energy-per-unit mass that is three times higher than traditional jet fuel. Airbus notes that, if generated from renewable energy through electrolysis, given the fact it emits no CO2 emissions, it will enable renewable energy to potentially power large aircraft over long distances but without the undesirable by-product of CO2 emissions.For now, we are still years away from commercial hydrogen aircraft becoming a reality, though. The refuelling infrastructure doesn’t exist yet and hydrogen is more expensive and difficult to store onboard than kerosene-based fuel."Hydrogen combustion capability is one of the foundational technologies we are developing and maturing as part of the CFM RISE Program," said Gaël Méheust, president & CEO of CFM. "Bringing together the collective capabilities and experience of CFM, our parent companies, and Airbus, we really do have the dream team in place to successfully demonstrate a hydrogen propulsion system."
November 22, 2023 | 09:43 PM