Another addition to the ‘Hydrogen Hub at Airport’ network underlines the growing belief that the technology is the most viable pathway to zero-emission flights

Hamburg in December became the latest airport to join the ‘Hydrogen Hub at Airport’ network, joining an impressive line-up that already includes the likes of Paris – Charles de Gaulle and Changi in Singapore, spread across 11 countries.
The initiative was launched by Airbus program ZEROe Hydrogen Ecosystem in 2020 to drive research into developing low-carbon airport operations and the necessary infrastructure requirements across the value chain. 
The program has set itself a target of deploying hydrogen-powered aircraft by 2035 – the OEM’s first major step on the pathway to zero emissions, according to Glenn Llewellyn, Airbus VP of Zero-Emission Aircraft:
“At Airbus, we strongly believe renewable energy needs to power future aviation. And hydrogen is potentially the best pathway through which to do so.” 
Hydrogen Hub at Airport is not only such initiative. Others include Project HEART, an end-to-end hydrogen infrastructure funded by the UK Research & Innovation Future Flight Challenge, and the Baltic Sea region HyAirport project in northern Europe.
Together they represent big votes of confidence for hydrogen being the most obvious solution to aviation’s carbon footprint problems at a time when many other industries are already taking enormous strides to becoming zero-emission. 
And it’s also timely: by the midway point of this century, it’s estimated that aviation could be responsible, if unmitigated, for as much as 22 percent of climate impact. 

Four pathways to zero emissions

Nevertheless, aviation remains divided about which pathway to take, and investment is pouring into four major areas – two that involve hydrogen, and two that do not:
  • Green hydrogen fuel derived from Power-to-X
  • Lithium-ion batteries
  • Electric engines
  • Hydrogen-electric engines
So before we assess the current progress of hydrogen-electric engines, let’s take a look at how the other three pathways are faring.

Green fuel 

Producing enough green hydrogen fuel to power the world’s current fleet would require a herculean effort. 
One popular option is Power-to-X, which converts alternative energy into hydrogen fuel. 
Interest is high – Denmark, for example, has set itself a target of using Power-to-X to power all its domestic flights by 2030 – but hopes are low that enough can be produced in the time needed to achieve zero-emissions by 2050.
In the meantime, OEMs won’t hang around waiting to see if the fuel can successfully power its current models. Nevertheless, as a way of fuelling hybrid solutions, it remains a viable option.

Lithium-ion batteries

Already, electric aircraft powered by lithium-ion batteries are making flights that produce next to no emissions. 
Over the last decade, batteries have transformed the way we travel in our cities by bicycle and scooter, and today they power 1 percent of all passenger cars in Europe.
But not only are plane batteries very heavy – on a recent trial by Israeli startup Alice, they accounted for 50 percent of the takeoff weight – they’re not capable of producing enough power to take a small plane much more than 1,000 km. 
Nevertheless, the demand for the tech is high as air travel becomes more local – the advent of electrically-powered air taxis in futuristic cities in the Middle East, where less regulatory clearance will be required, is just around the corner.

Electric engines

Considerable progress has been made with electric engines in the last year – although it remains the least likely of the pathways to flourish. 
In 2023, Canadian company Duxion Motors carried out a successful test of its eJet Motor, the world’s first rim-driven jet propulsion motor​​.
Also in 2023, MIT engineers created a 1MW motor of a weight and size comparable to current small aero-engines. 
However, the creation would be best suited to hybrid propulsion systems: electric and traditional, or electric and hydrogen – the pathway with the most promise, according to Hydrogen Hub at Airport.

Hydrogen-electric: a compelling case

Most likely, the tech that enables us to fly cleanly in the future has not been invented yet, so why do so many in the industry think the hydrogen-electric engine is the best pathway to future zero emissions?
Well, the typical hydrogen-electric engine can already harness 60 times more energy than lithium-ion batteries – and for a significantly lower cost too. 
Universal Hydrogen, a Californian-based company founded in 2020, is one of several making serious headway in the sector – and it already has an order to convert 75 planes for US carrier Connect Airlines.
Europe also staged hydrogen-electric trials last year: H2FLY, a German company based in Stuttgart with funding from several ministries, oversaw four flights taking off in Maribor, Slovenia, of which the longest lasted for three hours.
The H2FLY aircraft uses liquid hydrogen to power a hydrogen-electric fuel cell propulsion system. Using hydrogen gas, the planes have a range of 750 km, but this doubles using cryogenically-stored liquid hydrogen, which enables lower tank weights and volume, thus increasing the range and useful payload.
The timeline is not groundbreaking though. For example, British-American developer ZeroAvia – which welcomed Satair onboard as an investor in September 2023 along with Alaska Airlines and some big hitting investment funds – has plans to start retrofitting existing planes with its hydrogen-electric powertrains in 2025.
The powertrains will exert 15 times as much power than a battery-powered engine and be two to three times more fuel-efficient.
Its first engine in 2025 will fly planes with 9-19 seats and a range of 300 nautical miles, followed by larger models in 2027 (40-80 seats), 2029 (100-200 seats) and 2032 (200 seats). But it is only by 2040 that it expects to retrofit a plane capable of intercontinental travel (200+ seats). 
One airline to sign up is British green pioneer Ecojet, which in November 2023 confirmed its intention to buy 70 of ZeroAvia’s hydrogen-electric engines to power its planes. In 2027, it will become one of the first to take the ZA2000 engine, which will offer power in the range of 2.0-5.4 MW and fly 80-seaters.
Other airlines taking major strides in the sector include: Avolon, Delta Airlines, EasyJet, GOL, Icelandair, Japan Airlines, JetBlue, SAS, United Airlines, Vertical Aerospace, Virgin Atlantic, Viva Aerobus and Wideroe.

Growing MRO interest in the sector

ZeroAvia has been busy signing deals with MRO operators with a particular interest in hydrogen-electric engines.
For example, the Aerospace Engineering Center department at the MHI RJ Aviation Group has confirmed it will be providing MRO expertise to ZeroAvia – particularly in regard to engineering services, aircraft integration and certification support – and a number of OEMs have expressed interest in getting involved.
MRO operators cannot ignore this development. They will need to move with the times and start stocking spare parts for hydrogen-electric engines – as part of an overall strategy to get ready for a future in which clean fuel will power the world’s planes.
If they don’t, they run the risk that operators will shop elsewhere because as part of a lengthy transitional period they will have a mixed fleet of new gen hybrid aircraft and conventional aircraft solely powered by non-sustainable fuel, and they will favour USM suppliers that can cater to all their needs, instead of having to visit multiple suppliers.
US engineering services provider AeroTEC is one such operator. It takes pride in its ability to provide aftermarket support to one-off aircraft that other MRO providers might lack the capability or willingness to service. Its support includes aircraft integration, modifications, design, parts manufacturing, and safety and detail analysis. 
It not only provides hydrogen-electric support (to the likes of MagniX/NASA, Surf Air Mobility and Universal Hydrogen) but also parts to electric operators (such as MagniX and Eviation) – so it’s clearly hedging its bets about what the future might bring.
Another MRO making moves is Lufthansa Technik, which in 2021 launched a project to design and test hydrogen tech processes.
It transformed a decommissioned A320 into what it describes as a “stationary laboratory”, where it is testing out internal cryo-tanks for liquid hydrogen, a fuel-cell system and a conditioning system. It is also considering the practicality of refuelling, repairs and potential incidents.

New future, new skills

AeroTEC harbours plans to also provide training – a necessity in this new age of MRO for not only the next generation of planes, but also vertiports and electric vertical-takeoff-and-landing (eVTOL) aircraft, such as air taxis and drones.
MRO workers will need to seriously upgrade their skill sets across a wide range of new tech: from AI-powered IT to high-voltage electronics. 
Safety is also an incentive as liquid hydrogen cyro-tanks require cooling to -250C while the high-voltage electronics require 800-1,000 volts of electricity – more than enough to kill a worker who doesn’t follow procedure.
However, experts believe the switch to hydrogen solutions could simplify engine maintenance, not complicate it. They predict reduced wear and tear – primarily due to a significant lowering of engine part temperatures. Reduced combustion and fewer rotating components play a part in this.
But the technology isn’t in place at the moment for larger plans, the experts concur – particularly in regards to cooling hydrogen for use in a combustion engine. A breakthrough is needed.
A Russian experiment in the 1980s, the Tupolev Tu-155, encountered the same problem. The result was a plane filled with tubes and refrigeration units with no room for seats, let alone passengers. 
This missing link in the future development of hydrogen-electric tech could still leave the door open for green fuels that power conventional engines.


Investment continues to pour into the possibility of using batteries or clean fuel to power the world’s airlines, but it cannot compare with the recent tsunami of interest in the potential of hydrogen-electric engines – not only from airlines, but also airports and OEMs. MRO operations are accordingly waking up to the need to adapt quickly to the growing demand for expertise, maintenance and spare parts.
Cover image credits: Jernej Furman/Creative Commons