Great Western Coffee Shop

.............ready before HS2!  ;)

https://www.theguardian.com/business/2020/sep/21/airbus-reveals-plans-zero-emission-aircraft-fuelled-hydrogen

It says "could take to the skys by 2035".  Suggests it is likely to be after then certainly before there are significant numbers of them.  Then there is the question of how do you efficiently generate zero emission Hydrogen (electrolysis of water is currently very inefficient and people are still producing it from methane).  There is also the concern at the fate of the last aircraft that carried large amounts of hydrogen (airships - think R101, Hindenburg). 

One improvement being considered by the design committee is storing the hydrogen in pressurised cryogenic tanks, rather than using rubber bladders again...

But seriously, folks. I'm no President Trump when it comes to science, but I know that aviation depends on energy, and there are no zero sums, not even in gliding. Getting enough energy onto the aircraft to provide enough thrust to overcome gravity and drag for long enough to reach a destination without relying on fuels refined from fossils is the tricky bit. Hydrogen might have the edge over batteries if powerful enough electric motors can be developed.

The International Space Station could help here, though. It has a bigger and more immediate issue with carbon dioxide than the big blue planet below. The people on board breathe out a lot of it, and it tends to pool, being heavier than air, hence why there are lots of small fans around to distribute it. Left unchecked, it would suffocate the residents. Getting rid of it would mean bringing large volumes of oxygen from Earth regularly. I understand that the current solution involves reacting the separated CO₂ with hydrogen over a catalyst to produce water and methane using the Sabatier process (https://www.nasa.gov/mission_pages/station/research/news/sabatier.html). The hydrogen is electrolysed from water produced by the hydrogen fuel cells powering the onboard systems, this process also supplying the oxygen supply. It is very energy intensive, but there is a predictable supply of energy from a cloud-free sun for 45 minutes in each orbit. The methane is vented to space, but if similar were to be done on Earth using CO₂ separated from the atmosphere and the power of the sun somewhere with more of it that the UK, then we could have a synthetic fuel for aircraft, produced from the unwanted waste using the power of the sun. Whether it is possible without covering the entire Sahara with machinery is something I don't know.

Interesting that they are talking about burning the hydrogen in jet engines, rather than using fuel cells and electric motors.

Comparing efficiencies is a fraught business, but I think the consensus is that fuel cells are more efficient. They also have the advantage of not burning stuff in the upper atmosphere. Whatever you burn, you'll be burning it in air - a mixture of oxygen, nitrogen and other gases - so the exhaust won't be just water, but will also contain oxides of nitrogen and other nasties. Presumably aircraft manufacturers prefer to stick to turbo-machinery because that's the technology they know best, but surely there's no future in burning stuff?

There are, indeed, no zero sums. However, as luck would have it there's a massive positive input. Solar and wind can provide us with far far more energy than we can possibly consume; we just (just!) have to be more intelligent about how we harvest it. One option will be to use the nighttime surplus energy produced by cheap, extremely efficient wind turbines to produce hydrogen by electrolysis.

Fuel cells to power aircraft seem unlikely as they are relatively bulky and heavy, remembering that electric motors are also required. Fuel cells also don't respond very well to sudden changes in power demand, for this reason most fuel cell powered land vehicles also use batteries to supply sudden peaks.

The burning of hydrogen in modified jet engines shows more promise.

I remain rather doubtful about hydrogen power in general. It is inherently expensive, explosive, challenging to store and challenging to manufacture.
The only likely source of green hydrogen is from electrolysis of water, a well understood process. The efficiency is about 50%. Electricity costs about 5 pence a unit, off peak and in bulk. So hydrogen produced thus will cost at least 10 pence per KWH just for the energy input. A lot more after allowing for capital costs, rates, insurance, wages, and all the other costs of doing business.
Hydrogen gas would be useless for an aircraft, it is far too bulky. Liquified hydrogen is proposed instead, the liquefaction uses a lot of expensive and complicated plant, that requires substantial energy input. Very expensive super insulated tanks are needed to store and transport this fuel, and since no such insulated tank is perfect there will be continual losses by boiling off. Risk of fire and explosion, and a loss of the expensive product.

This hydrogen that boils off will rise and disperse. I still do not fancy a liquid hydrogen rail tanker running under OHLE or through a tunnel, nor do I like the idea of a road tanker passing under a bridge, upon which someone lights a fag and tosses the match over the railing.

I'm not surprised, given that the market Airbus addresses is medium-long range. Fuel cells, motors, and for now batteries too, simply weigh too much and don't allow enough fuel to be carried. Plus, for long range, you have to be at high altitude and propellers don't work up there (too little air).

Also, these are concepts. Built today, they wouldn't work (and quite likely not fly). They are starting points for a long process of evolution, changing the design, which may end up with something different (or with nothing). That evolution will also include the market (as defined by Airbus).

I think HS2 being finished first is a pretty good bet still.  ;)

?106 billion says it won't!  ;D

And if we are serious about significant use of hydrogen, whether for aircraft or other purposes, we will need to build a lot more wind turbines and a lot more solar capacity.
Proponents of hydrogen power often state that "surplus night time wind power" could be used for hydrogen production.

There is no surplus wind power. Even at times of high wind and low demand we still burn natural gas to generate electricity.
And we are often importing electricity from France as well, arguably also generated from natural gas.

Maybe "stuff", but not hydrogen. It has a lot going for it in fuel cells where batteries are not practical, and a higher energy density than methane. It has a lot going against it in terms of its Houdini-like ability to leak out of practically anything, its invisible burning in air, and expense. Jet engines depend on high temperatures and pressures to provide power, and hydrogen doesn't like that. Jet fuel has the big selling point of being liquid and relatively stable at normal ambient pressure and temperature, whereas hydrogen boils at -253?C. Fuel cells could work in propeller driven aircraft. Turboprops run at a constant engine speed, using propeller pitch to vary thrust, so regional aircraft might go there one day. Turbofans, even high bypass or unducted, would be a big ask.


With the exception of nuclear, all energy derives from the sun, without which there would be precious little wind. I'm not sure how many wind turbines would be needed to get to the place where we can stop burning gas  at every second of every day to produce electricity, but storing energy from wind and solar while still using any fossil fuel must be the environmental equivalent of using your credit card to fill your ISA.


France is our offshore nuclear facility.


There used to be a lot of "concept" cars, fridges, and aircraft turning up at the international shows, in non-working dummy form,  when I was somewhat younger. In those days, they were usually adorned with a couple of young smiling beautiful ladies, wearing clothing designed to be representative of what we would be wearing when the super glass sky-bike powered by stale urine took to the streets. Either someone knew global warming was coming before it got famous, or material for clothes is going to be in very short supply, because the garments got skimpier every year. As soon as the Sunday papers had photographed them, they probably went the way of the Bristol hydrogen ferry.

But yes, things change, sometimes slowly and by tiny increments, giving us cars that achieve the function of a 1960s Ford Consul, but using a lot less fuel and being safer. Sometimes, as in the jet engine, the change is sudden and has a more immediate impact, although the jet engine has changed enormously since the 1940s. Something lasting may come out of this research that we haven't spotted yet. If "zero emission aviation" ends up with dodgy accountancy tricks like the carbon trading and offset rackets in place, or if it means cutting every tree in Borneo and the Amazon region to grow crops for biofuel, I would count that as a disaster.

Interesting especially as Airbus do not make the Jet engines - they buy them from others.  If Rolls Royce were saying that I might take a bit more interest, but even then I am with TonyK. 


Don't forget tidal power. 

Only partly true in my view.
The bulk of French electricity is indeed from nuclear power. They have some natural gas fueled generating capacity, but this is a small proportion of the total.
It could however be argued that electricity that we import from France is entirely produced by burning gas.
Nuclear power is hugely expensive in capital cost, but cheap to run after the capital has been sunk. Therefore nuclear power plants are generally run continually apart from breakdowns and maintenance.
Gas burning power plants are the "marginal capacity" used to handle variable demand. If we import say 2 GW from France, this extra 2GW is produced by burning more gas. Not from nuclear which is already running "flat out".

Either way, that's nice. It's good to know that we are doing our bit, and that our emissions are lower. Our other pollution export programmes look good on paper, too.

Not being a Scientist,could solar type panels not be used on the wings and the top of the plane?

It won't power the plane 100 per cent,but a small per centage would be better than nothing.

To say 'they buy [engines] from others' is an oversimplification. Engines and airframes are highly-integrated, and when aircraft are available with a choice of engines from different manufacturers that's because the airframer has worked with the engine manufacturers for years to design variants to allow this.

And of course Rolls-Royce are working on various forms of hydrogen propulsion - they'd hardly be a world-beating engineering company if they weren't:

Source: BBC: Giant jet engines aim to make our flying greener (https://www.bbc.co.uk/news/business-50850242)

Added to existing designs, almost certainly not. The extra weight and drag would exceed the gain in energy terms.
For a purpose designed aircraft, possibly yes if the solar cells are designed in rather than being an afterthought.
Use of the electric power to help propel the aircraft might be too complicated, but use for heating, lighting, and electronics might be a possibility, thereby slightly reducing fuel used.
Solar powered drones, of considerable size but low speed have been demonstrated, IIRC one has circumnavigated the world.

There is  NASA's Pathfinder (https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-034-DFRC.html), which has made it well above Concorde altitude and into long endurance at slow speed. It's a very long way from flying 300 passengers across the Atlantic at night, but my grandma, whose name lives on in many hospitals across the country, was a schoolgirl on the day that Orville Wright made his first successful flight. She lived to see space shuttles, so a lot can change in a lifetime.

But! Hydrogen vehicles are NOT zero emission. Assuming you are burning it, there will be water vapour and unless the aircraft stores that water vapour on-board until it has landed said water vapour will be emitted into the atmosphere. If I recall correctly (and this seems to confirm https://www.skepticalscience.com/water-vapor-greenhouse-gas-basic.htm (https://www.skepticalscience.com/water-vapor-greenhouse-gas-basic.htm)), water vapour is a more-potent greenhouse gas than CO2! Thus, a hydrogen-powered aircraft is potentially worse than existing ones.

I have been led to believe that the tailpipe emissions of a fuel cell powered car or train are not an issue, as the water vapour is emitted close to ground level and will probably condense and fall out of the air soon after, but this is not true of air travel. Am I right?

You may have seen in the news about the HyFlyer project, being not at all modest about their 19-mile round trip in an HFC-powered plane. From prnewswire (https://www.prnewswire.co.uk/news-releases/zeroavia-completes-world-first-hydrogen-electric-passenger-plane-flight-870218125.html):

It's hard to know exactly what ZeroAvia (https://www.zeroavia.com/) have done, given the kind of high-intensity hype their web site is made of. But it's probably the first time they've used only the fuel cell, without a booster battery for the steep hill at the start.

I suspect the critical component is the fuel cell - it needs high power and low weight, plus - eventually - long life and high reliability. This comes from Intelligent Energy (https://www.intelligent-energy.com/news-and-events/company-news/2020/09/25/zeroavia-completes-world-first-hydrogen-electric-passenger-plane-flight/), who make this bit, and their prose is a bit duller. For example:

Leaving aside all the stuff about small planes and local airports being much cheaper (like taxis are cheaper than buses and trains?), the trouble with 10-20 seats and up to 800 km at (presumably) about 450 km/hr is that it competes primarily with high-speed trains except on routes without any.

As to emissions - they are pushing the line that jet engine exhaust is much worse (than what?) because it's at high altitude. That's not relevant for CO₂: it's the accumulation in the atmosphere/hydrosphere that matters. Water doesn't accumulate - it all exists already - so that's a genuine advantage. And you can't really raise the water vapour at high (or even medium) altitude, as the capacity for it so low. Convection keeps pushing the stuff up there, and it keeps condensing into tiny drops that grow bigger and fall - and we spend half our time talking about when and where they land.

Not quite. There's also hell fire. At the moment it's all wasted. Stolen shamelessly from Gunter Grass's fictionalisation of the real Lord Rumford, Benjamin Thompson, physicist and stove inventor.

I think it's quite an achievement, even if it looks like it did cost less than their website to run. don't think that I would have wanted to go too far from home on a first flight using a new application for a relatively new technology, especially given the model of aircraft used. Almost a tenth of all the PA46 family of aircraft built have been in accidents described in the jargon as "hull loss", and they are not known as being forgiving of mistakes. That said, I am sure the crew  were chosen because of their exceptional ability to fly in unusual situations.

From what I can gather , the aircraft is an adapted PA46R-350T, commonly known as a Piper Matrix, although one account I have read describes it as the subtly different Piper Malibu. It was built as a six seater aircraft with a 350 hp turbocharged engine (hence the T) and retractable undercarriage (and hence the R). It probably fitted the bill best because of the space available at the front end for the motors, and the already fitted constant velocity propeller. I would imagine that was easier to fit the new motors to that than to start ab initio development of a different way of turning the propellers. The electric motors would need only to turn the drive shaft at a constant speed, and react to differences in load from the variable pitch. Reading the blurb on the website, I think they are aiming for the smaller point-to-point flight rather than scaling up to A380 size.


Nasty though the CO₂ may be, it isn't all that comes out of the back of a jet engine. The hydrocarbons give up their energy by reacting, very efficiently in modern engines, with atmospheric oxygen to leave water and carbon dioxide. The trouble is that at the high pressures and temperatures in the combustion chamber, some of the normally inert atmospheric nitrogen reacts with the oxygen too, to make some very unpleasant compounds. The quantities may very well be a lot lower than claimed by the anti-aviation lobby, and the effects much less profound, but we could still do without them. This also happens at floor level in internal combustion engines, most markedly in diesel engines, but also in biogas engines, such as used by Bristol MetroBust. Win some, lose some.

And here's another, bigger, one, though I don't think it's going to be flying for a wee while yet, given the funding. Announced by the DfT and BEIS (https://www.gov.uk/government/news/government-backed-liquid-hydrogen-plane-paves-way-for-zero-emission-flight):

But as a project, it's more of a funding arrangement itself than a group of leading-edge manufacturers. They are still doing their initial technology selection reports, done by academics and consultants, while inviting more bids for work packages. So they are going to demonstrate a regional jet by 2030 and the long-range narrow-body plane by ... perhaps it's wise not to promise a date for that one. Here's a few more technical details (from E&T):

I don't suppose tickets have gone on sale yet?

£15 million sounds quite a lot when you are, like me, a pensioner of limited means, but a lot less when compared to, for example, the £1 billion reported cost of developing an engine for a Formula 1 car. Hydrogen seems to be the subject of some very expensive publicity campaigns at the moment, probably driven by the fossil fuel industry and gas pipeline owners wanting to position themselves for the future. My inner cynic views this as a part of that strategy, but you never know. One certainty is that it will cost a lot more than that to develop a cryogenic system that can be certified for passenger aircraft use. Burning hydrogen isn't a particularly efficient way of using it for motive power of any kind. Both problems would be resolved by making commercially economic synthetic fuel, by mixing that hydrogen with carbon from CO₂ recovered from the atmosphere. That might be a better answer to the problem, but hey - while none of the concept cars I have seen since childhood have ended up on the road, some engineering breakthroughs have come about as a result of the research. This could go the same way.

This thread started with Airbus's plans for hydrogenivorous aircraft, which were to lead up to a choice of concept in 2025. Well, they have company - or competition - in Toulouse from a bunch of Americans in much more of a hurry.

This is Universal Hydrogen, who have taken a can-opener to an ATR 72 to make a big door for loading liquid hydrogen storage "capsules" into the back of the cabin space (losing 20% of the seats). They started with a Dash-8 in Washington state, which is scheduled to fly with one engine replaced by the electric motor and HFC (in the nacelle) by the end of this year. Then, with customer airlines lined up in Europe and the USA, into commercial operation with a range of 500 nm by 2025.

There's obviously a big dollop of good ol' American can-do in that. But in this case we won't have long to wait to see if they could-do. And there are some clearly iffy bits in their story. Their US partner is "prospective Massachusetts-based regional carrier Connect Airlines" ... so that's not a real airline yet, then. In Europe it's DAT (Danish), which is at least a concrete airline. And how far will 500 nm get you anyway?  Not even halfway to Catania, for one thing.

Here's a detailed article from AINonline (https://www.ainonline.com/aviation-news/air-transport/2022-10-19/universal-hydrogen-fly-hydrogen-powered-dash-8-year-end)

How far will 500 nm get you? Not 500 nm, unless you don't bother carrying the normally reserve to divert or for bad weather.

Hopefully, the latest attempt will fare better than poor old G-HYZA above, which suffered a bit of a prang while on test last year, and has since been de-registered with the CAA. The AAIB report  (https://assets.publishing.service.gov.uk/media/62a20c39d3bf7f037097be7b/Piper_PA-46-350P__Modified__G-HYZA_08-22.pdf)must have been fun to write, with things going on the were hitherto unknown to the world of accident investigation, and it will interest experts of electronic sysytems everywhere.At the end of it all, though, the accident did involve a fair bit of standard aviation issues, cleverly adapted for the hydrogen era, and reminded us of the importance of flying the aircraft rather than getting bogged down with systems and dials and switches.

But that's only 0.0005 millimetres!

Let's upgrade it to 500 NM, and I'll get my caps lock looked at.  ;D

ZeroAvia (https://www.zeroavia.com/caa-part-21-permit) have now been given their ticket to start flight trials:

ZeroAvia are claiming another world first - though as usual it's hard to tell how first or how world it was. Since they flew a smaller one last year, this time (https://www.zeroavia.com/do228-first-flight):

Rather pointedly, they also say:

Follows on from their set-back last year
https://flyer.co.uk/ad-hoc-changes-to-flight-test-plan-contribute-to-zeroavia-electric-piper-crash/

Nice bit of promotional video of G-HYZA, previously N866LP, in happier times.

https://youtu.be/yqEDhIxh-aU