Quite a lot of discussion about this here:

https://www.greencarcongress.com/2024/01/20240113-zeroe.html

I will duplicate a post I made there:

'

I have not managed to track the performance specs of the fuel cell down, but I have come across more info on how Airbus intends to move forward:

https://www.flightglobal.com/airframers/airbus-will-be-ready-to-develop-hydrogen-powered-aircraft-by-2035-goal-ceo/154962.article

' “The bottlenecks are no longer in the technology of the plane,” Airbus chief executive Guillaume Faury said on 12 September during an aerospace event in Washington DC. “We strongly believe that we will be ready by 2035 with a hydrogen plane. The technology will be ready.”

Airbus in 2020 revealed three hydrogen-powered aircraft concepts as part of its ZEROe programme, and said it aimed to bring one to market by 2035.'

That's a pretty strong claim about the technology,

And:

' Executives stress that, optimism aside, Airbus has not committed to developing a hydrogen-powered passenger airliner, saying the decision depends on factors partly or largely outside the company’s control.

Those include unclear regulatory and certification standards, the need for hydrogen transportation and storage infrastructure, and the availability – at the “right price” – of green hydrogen produced using renewable electricity: “That’s going to be where the challenge lies,” Faury says.

Knittel says any initial hydrogen-powered aircraft would likely be on the “smaller” side, and that “long range” is among the toughest “challenges” associated with hydrogen propulsion.'

My betting is that IF hydrogen gets the go-ahead, it will be in a configuration where fuel cells power the APU, with hydrogen combustion which can manage more range etc as the propulsive unit'

I also posted on the thread claims by Airbus that contrails, at any rate of the sort which can cause climate change, can be lowered by hydrogen combustion instead of kerosene and virtually eliminated using fuel cells for propulsion.

@Gryf:

Just so.

https://www.eurocontrol.int/article/aviation-outlook-2050-air-traffic-forecast-shows-aviation-pathway-net-zero-co2-emissions

' The report considers the environmental consequences of this. It predicts long-haul flights will continue to be the major source of CO2 emissions. Revolutionary fleet renewal (using electric or hydrogen propulsion) represents 2% of the 279 million tonnes of CO2 emissions savings required to meet the net zero target therefore the remaining required reduction in CO2 emissions will have to come from greater use of SAFs, ATM and operational improvements and out-of-sector measures.'

However, it seems to me that the introduction of hydrogen and fuel cells for short haul initially is an enabling technology, as 25 years is not so very long,

And SAF etc cannot, or at any rate should not, be used as an excuse for pressing on with long haul without effective decarbonisation.

' U.S. jet fuel currently retails at around $2.85 per gallon while SAF prices are at $6.69 per gallon, as per data from commodities and energy pricing agency Argus Media.'

https://www.reuters.com/sustainability/us-sustainable-aviation-fuel-production-target-faces-cost-margin-challenges-2023-11-01/

So it would appear that the projected increases in long haul flights using SAF, or hoping to do so at some time in the indefinite future, are predicated on the carbon emissions being not really taken very seriously.

Flying to the Maldives on holiday perhaps should not be taken as the absolute priority over frying the planet.

Reading up on it, SAF is sounding more and more like a fake non-solution to me
ie an excuse for more and more CO2 emissions from a sector, long haul flight, which if to use it as an excuse for expansion:

https://www.oliverwyman.com/our-expertise/journals/energy-journal/the-saf-flight-path-to-decarbonization.html

' While governments in the United States and Europe have tried to encourage more production, their efforts haven’t yet moved the needle. Recently, the US has been more aggressive, passing a generous tax credit for SAF and pledging $4 billion as starter money to build three billion gallons of capacity, equaling about 10% of the US demand for jet fuel. The European Commission has proposed a mandate requiring the blending of a minimum of 2% SAF or other low-carbon fuels with conventional jet fuel beginning in 2025. The mandate would increase in five year intervals until it reached 63% in 2050. Still, more government support is needed if SAF production is to attract the additional investment necessary from the private sector and the industry is to cut its emissions. '

And:

' The long-term goal in SAF continues to be e-SAF, which is fuel produced directly from captured CO2, using renewable energy and green hydrogen with negligible environmental impact. In theory, this feedstock has an unlimited supply, but it requires copious amounts of green electricity. The technology is a decade or more from commercial maturity and is expensive, even by biofuel standards.'

Presumably relying on Direct Air Capture, to put the cherry on the top of a wholly unrealistic proposition.

So aeroplane manufacturers, with a small partial exemption for Airbus, intend to churn out umpteen thousands of planes, reliant for decarbonisation on a hopelessly uneconomic fantasy fuel, 'to be developed'

They are lying.

There is no necessity to have an ever increasing volume of long distance flights.

@SJC

https://www.airbus.com/en/newsroom/stories/2022-11-airbus-prepares-for-its-first-megawatt-class-hydrogen-fuel-cell-engine

'Two years ago, Airbus unveiled several possible aircraft concepts – known collectively as “ZEROe” – which are helping to define the world’s first zero-emission commercial airliner which could enter service by 2035. While these concepts explore various size categories, aerodynamic layouts and propulsion system architectures, they all have one thing in common: they are hydrogen-fuelled. Three of them have engines which use hydrogen combustion to drive their gas turbines – similar to the way that turbofans and turboprops burn kerosene today, but without the latter’s CO2 and particulate emissions.

Meanwhile, a fourth ZEROe concept aircraft, representing a high-wing 100-seat regional airliner, features six eight-bladed propellers attached to engine pods – a configuration recently patented by Airbus. While outwardly resembling turboprop powerplants, these pods actually contain hydrogen fuel cells which produce electricity as the result of an electro-chemical reaction to power electric motors. It is in this context that Airbus has been conducting feasibility studies and laboratory tests to realise a fully working megawatt-class fuel-cell engine and demonstrator which could be tested in flight by the middle of this decade – around 2026.'

That was November 2022

They now have the fuel cell set up working, and it is undergoing tests.

Airbus like the rest of the aerospace industry though is relying on SAF for its long range, transatlantic etc stuff

The priority is not to hinder more traffic to the Maldives, it seems

Whether they can land there without floats due the rising water consequent on the increase in CO2 is thought to be irrelevant, so long as they can build and sell more long distance planes.

@SJC

Somehow I don't think Airbus have forgotten that they need a motor for their possible 100 seater fuel cell powered plane!

@SJC

https://www.electrive.com/2023/02/10/nidec-subsidiary-to-develop-aircraft-drives/

' Apart from the “very high requirements”, Nidec does not give any further details on the planned electric motor prototypes in the announcement. What power and weight the drive units are to achieve is thus not known. However, it says that the research and development team in Angoulême, France, is challenged to “explore breakthrough technologies and innovations to optimize the architecture of the aircraft propulsion system”. So the demands are likely to be high.'

We do know that they are building not one, but a series of protoypes:

https://www.urbanairmobilitynews.com/air-taxis/nidec-leroy-somer-selected-by-airbus-to-develop-electric-motors-for-future-hydrogen-engine/

@sd

Non- engineer here!

However, the bits I understand indicate that the power requirements are not necessarily the same, and of course the 1.2MW system is modular, and could have several units,

The volume requirements are to some extent reduced by the extra energy density.
Airbus propose different configurations to present ones to deal with the fuel.

The tanks and cost of hydrogen are also the subject of extensive debate elsewhere.

@Gryf

Many thanks. Fuel cells can, perhaps, manage regional markets, but long distance is way outside their capability, and even the turbofan blended wing version is limited compared to conventional jets.

So for long distance, hydrogen is irrelevant, and unfortunately that is where most of the CO2 emissions happen,

There would appear to be no practical plans at all to achieve low emission SAF fuel in volume at a price enabling the projected increase in flights.

So the aircraft industry is counting on a free pass for carbon emissions, prioritising ever increasing long distance travel over climate change.

If low emission SAF were priced enough to replace conventional fuel, and in any case there would appear to be severe constraints on volumes of production as it is mainly biomass, there would be no increase in long distance flight, nor a market for the umpteen thousands of planes the industry intends to produce on the basis of their free pass for climate change.

@GdB

Thanks for your deeply informed input.
This confirms my own inexpert notions, that there is no real emphasis on effectively going for zero carbon, or even greatly reduced, just lip service.

With present planes obviously incapable of being converted to blended wing etc, they are planning on a very large expansion of the long haul fleet without any effective way of reducing emissions greatly, just creating a legacy of planes obsolete from the outset, sunk costs in obsolescence.

And this vast expansion of GHG emissions for an industry which is overwhelmingly a matter of convenience, not necessity.

With proper carbon costing there would be little or no expansion of the long haul fleet.