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Author Topic: Zero emission aircraft  (Read 1199 times)
TaplowGreen
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« on: September 23, 2020, 07:26:15 am »

.............ready before HS2!  Wink

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

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ellendune
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« Reply #1 on: September 23, 2020, 07:52:06 am »



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). 
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TonyK
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« Reply #2 on: September 23, 2020, 09:49:24 am »

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. 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.
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Red Squirrel
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« Reply #3 on: September 23, 2020, 12:18:08 pm »

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.
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broadgage
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« Reply #4 on: September 23, 2020, 02:03:23 pm »

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.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
stuving
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« Reply #5 on: September 23, 2020, 03:53:53 pm »

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

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).
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IndustryInsider
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« Reply #6 on: September 23, 2020, 05:02:30 pm »

I think HS2 being finished first is a pretty good bet still.  Wink
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TaplowGreen
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« Reply #7 on: September 23, 2020, 05:27:56 pm »

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

?106 billion says it won't!  Grin
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broadgage
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« Reply #8 on: September 23, 2020, 06:48:34 pm »

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.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
TonyK
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« Reply #9 on: September 23, 2020, 08:36:44 pm »

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?

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.

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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.

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.

And we are often importing electricity from France as well, arguably also generated from natural gas.

France is our offshore nuclear facility.

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).

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.
« Last Edit: September 24, 2020, 11:13:44 pm by TonyK » Logged

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ellendune
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« Reply #10 on: September 23, 2020, 08:55:18 pm »

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

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. 

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.

Don't forget tidal power. 
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broadgage
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« Reply #11 on: September 23, 2020, 09:38:45 pm »



And we are often importing electricity from France as well, arguably also generated from natural gas.

France is our offshore nuclear facility.


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".
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
TonyK
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« Reply #12 on: September 24, 2020, 07:39:34 am »


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.
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« Reply #13 on: September 24, 2020, 09:53:41 am »

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.
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Red Squirrel
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« Reply #14 on: September 24, 2020, 11:27:13 am »

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

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. 

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.

Don't forget tidal power. 

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:

Quote
While Rolls-Royce and others in the aerospace industry are working on electric and hybrid propulsion systems for aircraft, for long-haul aircraft, at the moment jet engines are the only option.
Source: BBC: Giant jet engines aim to make our flying greener

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