I'll admit I really don't get the fascination with hydrogen as an energy storage medium. It has to be manufactured, so how green it is depends on whatever the power input is coming from. It's not any inherently greener then synthetic hydrocarbon production, which can be produced from atmospheric carbon for zero net carbon impact, and of course has no sulfur or aromatics. It also works fine with existing engineering. And hydrogen is an absolute total bitch to work with. It's got bad density, a really low/really high pressure liquidation point, escapes from everything, embrittles steel, and on and on. The infrastructure has no multiple use, unlike improvements to the grid.
So why not just do full manufacture of regular fuel? I've never understood where hydrogen fits between improving batteries/capacitors and synthetic hydrocarbons. It always seemed like an answer without a question outside of rockets (and even there the economics and practicalities of methalox may be better).
> It's not any inherently greener then synthetic hydrocarbon production, which can be produced from atmospheric carbon for zero net carbon impact
As I understand it, the production of complex hydrocarbons that can be used as a replacement for jet fuel is even more inefficient when compared to the production of hydrogen, as many of the known processes that start from CO2 actually use hydrogen in the process. So, although you could get energy-denser fuels, that would be at the cost of even more end-to-end efficiency.
Finally, hydrogen has a great energy / kg ratio, making it a very interesting fuel for aviation if the material science problems of hydrogen can be overcome, as it allows for longer distance flights / flights with more/heavier cargo.
You can manufacture hydrogen anywhere as long as you have water, an electrolyzer, and a power source. Oil can only be pumped out of the ground in certain places, water is technically _much_ more abundant everywhere.
Hydrogen storage tech has improved in the last twenty years. It's becoming affordable and "as safe" to store hydrogen at fuel densities similar to that of petroleum based fuels.
Obviously the devil's in the details, but shouldn't we attempt to engineer huge carbon emitters like container shipping or aircraft to run on hydrogen + solar?
> The infrastructure has no multiple use, unlike improvements to the grid.
You need hydrogen for steel production, ammonia, and synthetic hydrocarbon production. Likely cement, glass, and plastic production too.
> So why not just do full manufacture of regular fuel? I've never understood where hydrogen fits between improving batteries/capacitors and synthetic hydrocarbons.
Because fuel cells are batteries themselves, and synthetic hydrocarbon needs hydrogen.
> So why not just do full manufacture of regular fuel?
Always fascinating when people use "just" in sentences where they propose something that hasn't been done before (at least not at any scale that would matter) and that is a huge challenge.
As for the reason, my understading is that producing fuels from electricity is just very inefficient. You still use hydrogen as the first step and then add other steps to produce hydrocarbons. Using hydrogen spares a few conversion steps and you'll need less electricity (but likely still a lot).
An advantage of hydrogen is that it can be used in fuel cells, producing only water as reaction product. Using hydrocarbons of any sort in existing engines leads to the production of nitrogen oxides due to the presence of nitrogen in the air.
Manufactured fuels have two main economies: one is energy input per energy output (usually bigger than one and the goal is to get that number as close to one as possible) and the other is transformer system cost, particularly cost that even applies when idle. If this number is very high fuel manufacturing won't be opportunistic at all and will keep the conversion systems at high utilization, offering input energy prices as needed and selling at prices depending on demand. A very low investment/idleness cost on the other hand would lead to wildly variable utilization depending on output demand and input availability.
Hydrogen is usually considered a very simple conversation (e.g. compared to synthetic hydrocarbons) that would be very open to opportunistic transformation utilization.
"Only fire up the converters when there's an open order for synfuel and the grid has excess power", that's the dream. I'm not convinced that this dream is significantly more viable for simple hydrogen than for more complex synfuels (particularly factoring in the many ways hydrogen isn't easy to store), but I can easily see how some people might want to believe that.
It's difficult to tell how they will deal with hydrogen as they don't even try to address all the points you have made.
The articles available just say "hydrogen stored in tank under the wing".
Seems investors in green tech. will be betting on both technologies aka having facilities that can both produce hydrogen and synt. fuels.
Well the answer to that is that it is not that simple. We know how synthesize hydrogen and scale it and what it will cost because companies are already doing that today. Synthesizing other fuels may be long term feasible but are simply not commonly done right now. More importantly, there don't seem to be many companies planning to do that right now. Airbus is not in the business of producing fuel so it would need such a company to step up and do it before they can start designing products for it.
E.g. liquid methane would be a good alternative for hydrogen. The appeal of both hydrogen and methane would be that converting engines to burn it seems doable and given that rockets can use either as propellant there is no question about their suitability as a fuel from an efficiency point of view. The difference of course is that with methane it would end up coming from fossil reserves which from the point of view going carbon neutral kind of defeats the purpose of making these planes carbon neutral. Swapping out kerosene for methane kind of just moves that problem. IMHO it's still worth exploring (and some companies have actually done that). Also, I imagine synthetic methane is eventually going to happen and kill the market for natural gas. Just not in the next decades.
The key here is a combination of becoming carbon neutral and doing it in a cost effective and timely way. Synthetic methane may or may not actually become a thing but the simple reality is that it's an industry that simply does not currently exist. Clean hydrogen production on the other hand exists today (at small scale) and seems to be on a feasible path to scaling in the next 15 years or so. Additionally hydrogen infrastructure is something that is attracting lots of investment currently. Airbus is targeting a launch in the mid to late 2030's. So they need to be targeting a fuel source that they can reasonably expect to have some supply for by then so they can actually fuel the planes where-ever they need to fly. So the supply and infrastructure for hydrogen are not a certainty but at least on a path where it could be there in 15 years. The rest is just solving engineering problems. They seem to believe they can do it.
Getting the carbon is a huge problem. Atmospheric CO2 is at something like 400ppm - that's 0.04% of air. Given that most hydrocarbons contain a fairly large amount of carbon, that means you have to process a huge amount of air to get the CO2 needed for your fuel. That's before all the other process inefficiencies.
I agree hydrogen isn't the best fuel, but the round trip efficiency of any other synthesised hydrocarbon must be an order of magnitude lower - and even if solar energy is abundant, it's not so abundant we can waste 90%+ of it on process inefficiencies.
Not as helpful for reducing effective emissions as you might think.
High altitude water vapor is just as big of a problem as CO2 as the lifetime of water vapor in the stratosphere is measured in years, not days or hours like it is in the lower troposphere. Water vapor is, after all, a much stronger greenhouse gas than CO2, it's just that normally its lifetime in the atmosphere is so short so as not to matter.
So unless we can be certain these planes will fly solely in the lower troposphere (unlikely, considering the aircraft presented), then hydrogen is not actually necessarily a silver bullet and in some situations (i.e. very high altitude flight, ala Concorde) could actually be worse than kerosene.
> High altitude water vapor is just as big of a problem as CO2 as the lifetime of water vapor in the stratosphere is measured in years, not days or hours like it is in the lower troposphere.
On Table 1 of your study, it’s measuring residence time of stratospheric water vapor in days. How are you getting years from that?
In a world where existing natural gas infrastructure transitions to hydrogen, securing sufficient hydrogen fuel at airports seems totally practical.
Due to the fuel's low density, the conventional fuselage designs lose a lot of load capacity.
The blended wing body looks practical, with plenty of interior volume. Hearing people complain about passengers not wanting to sit in a stadium, or that their inner ear will be unmitigatedly upset by roll changes remind me of historical folks who said cars would never take off because they'd scare the horses.
I find this announcement surprisingly scarce on details. It's basically a press release and some nice pictures. It lacks even basic information like the amount of hydrogen they'll need for a given flight.
Would not be easier to produce synthetic kerosene fuel from captured CO2 and hydrogen.
The process is straightforward:
1. A lot of cheap solar energy, from the best location.
2. Electrolyse to produce hydrogen.
3. Capture CO2. Either from air or from carbon intensive processes (e.g. producing cement).
4. Use Sabatier reaction to bond CO2 and hydrogen to produce carbohydrate fuel.
5. Since we use same amount of CO2 to produce as there will be burn this carbon neutral fuel.
It's much easier to do it at scale, than redesign, get approved new planes, replace all existing fleets and the infrastructure. This could easily take 60-120 years, when we need to act much sooner to prevent worst consequences of global warming.
Of course, today this would not work as individual steps are too expensive. Though all of the steps could be much cheaper as solar energy panel shows.
It gives possibility for oil rich countries to transform to post carbon economy when they resources will be depleted and consumers would prefer carbon neutral fuels.
I guess all of this sovereign funds would be much better of investing in this tech than pouring money in SoftBank to do WeWork style opportunities.
Google crowd oil or solar kerosene for papers about it.
> A lot of cheap solar energy, from the best location.
I recommend that you watch the "Planet of the Humans" documentary to understand why there is no cheap solar energy, no so-called "green" energies: https://www.youtube.com/watch?v=Zk11vI-7czE
So there will never be any "green" planes, no matter if they use hydrogen or kerosen. Since the minimum required amount of energy to fly from point A to point B with N passengers will always be the same.
"5. Since we use same amount of CO2 to produce as there will be burn this carbon neutral fuel."
Not necessarily, it depends on the byproducts - hypothetically, suppose when you burned the fuel the emissions were SOMEHOW 100% methane. You're essentially turning CO2 into methane in this farcical hypothetical, which is probably worse than burning normal fossil-kerosene.
Obviously the emissions won't be methane, but you'll need to track the CO2e of every type of emission it produces other than CO2.
I think most non-intercontinental flight will go to battery. The operational cost is just unbeatable. All you need to do is mass produce batteries and because of car industry the amount of money going into this is insane.
Battery planes will eat the market from below, step by step.
Interesting that this doesn't primarily use fuel cells[0] (which is what hydrogen-electric aviation usually proposes to use), but directly combusts the hydrogen to run a traditional jet engine. There was a Soviet Union airliner that did this, so it definitely works, although I'm skeptical that hydrogen makes sense as an aviation fuel because jet fuel is much more convenient (easier to transport, store, and handle, and cheaper).
[0]: It uses fuel cells too, but looks like most of the propulsion comes from the turbines.
Fuel cells are too heavy, at least for the time being. Other than biofuels or synfuels, there's basically no alternatives. Aviation companies will have to pick one of those fuels.
A side-question on the perspective of battery-driven electric-flights: when electric cars can recuperate power instead of breaking, why can't airplanes do the same on descent? Couldn't they build a propeller at the rear, which does propulsion and recuperation? Energy-wise, that would certainly be attractive...
My gut feeling is that it's probably not substantial amounts of energy to find there. Compared to a car in city traffic which might break to a standstill every other minute, an aircraft generally only "brakes" once when going down for landing.
Further, since air resistance scales with the square of the velocity, the drag forces on an aircraft is so high that you typically never reduce thrust to zero until to just before touching down. An aircraft never idle-glide any substantial part of the flight. I.e, it's like trying to recuperate energy while driving slowly in a car up a very steep hill. Just releasing the throttle will make you stop quite rapidly...
The "Blended-Wing Body" design looks radically different that any plan I've ever seen. Anyone know if anything like that has existed before, and how the shape would affect take-off speeds, cruising speeds, handing etc?
One problem with hydrogen powered air plannes (which I know from some older articles I had read airbus is aware of) is that emitting small water droplets in the higher atmosphere is actually problematic.
I have no good sources but don't articles I have read said it's potentially worse then the CO2 emission of current air plainness.
So additional care must be taken to not condense the water from the hydrogen burning into larger potions/prices before emitting it.
It's good to see aviation companies looking for fuel alternatives. For those interested, use happen to keep track of the 2035 release of the Airbus ZEROe hydrogen aircraft https://www.usehappen.com/events/67517310
These concept renderings omit the basic physical facts: that hydrogen is less energy dense and therefore you need more of it. Tanks will be bigger and distances will be shorter.
[+] [-] xoa|5 years ago|reply
So why not just do full manufacture of regular fuel? I've never understood where hydrogen fits between improving batteries/capacitors and synthetic hydrocarbons. It always seemed like an answer without a question outside of rockets (and even there the economics and practicalities of methalox may be better).
[+] [-] mattashii|5 years ago|reply
As I understand it, the production of complex hydrocarbons that can be used as a replacement for jet fuel is even more inefficient when compared to the production of hydrogen, as many of the known processes that start from CO2 actually use hydrogen in the process. So, although you could get energy-denser fuels, that would be at the cost of even more end-to-end efficiency.
Finally, hydrogen has a great energy / kg ratio, making it a very interesting fuel for aviation if the material science problems of hydrogen can be overcome, as it allows for longer distance flights / flights with more/heavier cargo.
[+] [-] schainks|5 years ago|reply
You can manufacture hydrogen anywhere as long as you have water, an electrolyzer, and a power source. Oil can only be pumped out of the ground in certain places, water is technically _much_ more abundant everywhere.
Hydrogen storage tech has improved in the last twenty years. It's becoming affordable and "as safe" to store hydrogen at fuel densities similar to that of petroleum based fuels.
Obviously the devil's in the details, but shouldn't we attempt to engineer huge carbon emitters like container shipping or aircraft to run on hydrogen + solar?
[+] [-] Hypx|5 years ago|reply
You need hydrogen for steel production, ammonia, and synthetic hydrocarbon production. Likely cement, glass, and plastic production too.
> So why not just do full manufacture of regular fuel? I've never understood where hydrogen fits between improving batteries/capacitors and synthetic hydrocarbons.
Because fuel cells are batteries themselves, and synthetic hydrocarbon needs hydrogen.
[+] [-] hannob|5 years ago|reply
Always fascinating when people use "just" in sentences where they propose something that hasn't been done before (at least not at any scale that would matter) and that is a huge challenge.
As for the reason, my understading is that producing fuels from electricity is just very inefficient. You still use hydrogen as the first step and then add other steps to produce hydrocarbons. Using hydrogen spares a few conversion steps and you'll need less electricity (but likely still a lot).
[+] [-] Yetanfou|5 years ago|reply
[+] [-] usrusr|5 years ago|reply
Hydrogen is usually considered a very simple conversation (e.g. compared to synthetic hydrocarbons) that would be very open to opportunistic transformation utilization.
"Only fire up the converters when there's an open order for synfuel and the grid has excess power", that's the dream. I'm not convinced that this dream is significantly more viable for simple hydrogen than for more complex synfuels (particularly factoring in the many ways hydrogen isn't easy to store), but I can easily see how some people might want to believe that.
[+] [-] Kosirich|5 years ago|reply
https://www.energyglobal.com/special-reports/28082020/haldor...
https://www.engineering.com/ElectronicsDesign/ElectronicsDes...
[+] [-] jillesvangurp|5 years ago|reply
E.g. liquid methane would be a good alternative for hydrogen. The appeal of both hydrogen and methane would be that converting engines to burn it seems doable and given that rockets can use either as propellant there is no question about their suitability as a fuel from an efficiency point of view. The difference of course is that with methane it would end up coming from fossil reserves which from the point of view going carbon neutral kind of defeats the purpose of making these planes carbon neutral. Swapping out kerosene for methane kind of just moves that problem. IMHO it's still worth exploring (and some companies have actually done that). Also, I imagine synthetic methane is eventually going to happen and kill the market for natural gas. Just not in the next decades.
The key here is a combination of becoming carbon neutral and doing it in a cost effective and timely way. Synthetic methane may or may not actually become a thing but the simple reality is that it's an industry that simply does not currently exist. Clean hydrogen production on the other hand exists today (at small scale) and seems to be on a feasible path to scaling in the next 15 years or so. Additionally hydrogen infrastructure is something that is attracting lots of investment currently. Airbus is targeting a launch in the mid to late 2030's. So they need to be targeting a fuel source that they can reasonably expect to have some supply for by then so they can actually fuel the planes where-ever they need to fly. So the supply and infrastructure for hydrogen are not a certainty but at least on a path where it could be there in 15 years. The rest is just solving engineering problems. They seem to believe they can do it.
[+] [-] leoedin|5 years ago|reply
I agree hydrogen isn't the best fuel, but the round trip efficiency of any other synthesised hydrocarbon must be an order of magnitude lower - and even if solar energy is abundant, it's not so abundant we can waste 90%+ of it on process inefficiencies.
[+] [-] sergeykish|5 years ago|reply
Hydrogen solves long term storage for electricity generation and heating (winter time)
https://model.energy/
[+] [-] aeternum|5 years ago|reply
[+] [-] Robotbeat|5 years ago|reply
High altitude water vapor is just as big of a problem as CO2 as the lifetime of water vapor in the stratosphere is measured in years, not days or hours like it is in the lower troposphere. Water vapor is, after all, a much stronger greenhouse gas than CO2, it's just that normally its lifetime in the atmosphere is so short so as not to matter.
So unless we can be certain these planes will fly solely in the lower troposphere (unlikely, considering the aircraft presented), then hydrogen is not actually necessarily a silver bullet and in some situations (i.e. very high altitude flight, ala Concorde) could actually be worse than kerosene.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200...
[+] [-] Hypx|5 years ago|reply
On Table 1 of your study, it’s measuring residence time of stratospheric water vapor in days. How are you getting years from that?
[+] [-] skykooler|5 years ago|reply
[+] [-] ncmncm|5 years ago|reply
[+] [-] benhurmarcel|5 years ago|reply
[+] [-] unchocked|5 years ago|reply
Due to the fuel's low density, the conventional fuselage designs lose a lot of load capacity.
The blended wing body looks practical, with plenty of interior volume. Hearing people complain about passengers not wanting to sit in a stadium, or that their inner ear will be unmitigatedly upset by roll changes remind me of historical folks who said cars would never take off because they'd scare the horses.
[+] [-] hannob|5 years ago|reply
[+] [-] jakozaur|5 years ago|reply
The process is straightforward:
1. A lot of cheap solar energy, from the best location.
2. Electrolyse to produce hydrogen.
3. Capture CO2. Either from air or from carbon intensive processes (e.g. producing cement).
4. Use Sabatier reaction to bond CO2 and hydrogen to produce carbohydrate fuel.
5. Since we use same amount of CO2 to produce as there will be burn this carbon neutral fuel.
It's much easier to do it at scale, than redesign, get approved new planes, replace all existing fleets and the infrastructure. This could easily take 60-120 years, when we need to act much sooner to prevent worst consequences of global warming.
Of course, today this would not work as individual steps are too expensive. Though all of the steps could be much cheaper as solar energy panel shows.
It gives possibility for oil rich countries to transform to post carbon economy when they resources will be depleted and consumers would prefer carbon neutral fuels.
I guess all of this sovereign funds would be much better of investing in this tech than pouring money in SoftBank to do WeWork style opportunities.
Google crowd oil or solar kerosene for papers about it.
[+] [-] largolagrande|5 years ago|reply
I recommend that you watch the "Planet of the Humans" documentary to understand why there is no cheap solar energy, no so-called "green" energies: https://www.youtube.com/watch?v=Zk11vI-7czE
So there will never be any "green" planes, no matter if they use hydrogen or kerosen. Since the minimum required amount of energy to fly from point A to point B with N passengers will always be the same.
[+] [-] Qwertious|5 years ago|reply
Not necessarily, it depends on the byproducts - hypothetically, suppose when you burned the fuel the emissions were SOMEHOW 100% methane. You're essentially turning CO2 into methane in this farcical hypothetical, which is probably worse than burning normal fossil-kerosene.
Obviously the emissions won't be methane, but you'll need to track the CO2e of every type of emission it produces other than CO2.
[+] [-] nickik|5 years ago|reply
Battery planes will eat the market from below, step by step.
[+] [-] jeffreyrogers|5 years ago|reply
[0]: It uses fuel cells too, but looks like most of the propulsion comes from the turbines.
[+] [-] Hypx|5 years ago|reply
[+] [-] ib84|5 years ago|reply
[+] [-] filleokus|5 years ago|reply
Further, since air resistance scales with the square of the velocity, the drag forces on an aircraft is so high that you typically never reduce thrust to zero until to just before touching down. An aircraft never idle-glide any substantial part of the flight. I.e, it's like trying to recuperate energy while driving slowly in a car up a very steep hill. Just releasing the throttle will make you stop quite rapidly...
[+] [-] jackdeansmith|5 years ago|reply
[+] [-] GordonS|5 years ago|reply
[+] [-] largolagrande|5 years ago|reply
[+] [-] Qwertious|5 years ago|reply
https://en.wikipedia.org/wiki/Planet_of_the_Humans#Factual_a...
https://votetosurvive.org/skepticism-is-healthy-but-planet-o...
[+] [-] nmeofthestate|5 years ago|reply
[+] [-] neximo64|5 years ago|reply
[+] [-] neuronic|5 years ago|reply
[+] [-] dathinab|5 years ago|reply
I have no good sources but don't articles I have read said it's potentially worse then the CO2 emission of current air plainness.
So additional care must be taken to not condense the water from the hydrogen burning into larger potions/prices before emitting it.
[+] [-] ncmncm|5 years ago|reply
[+] [-] amai|5 years ago|reply
[+] [-] ebbflowgo|5 years ago|reply
[+] [-] bfieidhbrjr|5 years ago|reply
[+] [-] codecamper|5 years ago|reply
These concept renderings omit the basic physical facts: that hydrogen is less energy dense and therefore you need more of it. Tanks will be bigger and distances will be shorter.
[+] [-] bildung|5 years ago|reply
Energy per kg is much higher for liquid hydrogen (122.8 MJ/kg) than for kerosine (42.8 MJ/kg): https://www.fzt.haw-hamburg.de/pers/Scholz/GF/GF_Paper_DLRK_...
So planes would look bulkier, but could actually be lighter than before.
[+] [-] aero-glide|5 years ago|reply