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ZEROe: Hydrogen-hybrid aircraft concept

airbus.com

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Re: ZEROe: Hydrogen-hybrid aircraft concept

#71

Post by benhurmarcel »

Robotbeat wrote: post #20

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 unle…

If that’s such a problem we could store onboard the water produced by the fuel cell.

Re: ZEROe: Hydrogen-hybrid aircraft concept

#72

Post by dcustodio »

xoa wrote: post #9
mattashii wrote: post #8

Earlier quoted context omitted.

> 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, altho…

That makes sense. I guess the questions would be whether the material science can really allow us to make use of that, and how the end-to-end efficiency weights against the infrastructure/engineering greenfield costs that synthetic fuels avoid. Being able to just keep using all existing engines/storage/distribution knowledge we already have is a major economic advantage. Electric will cover most land based transporta…

Don't forget that wind turbines still produce at night when there is less demand. So either you use that power to pump water upstream (if you have dams) or you can use it to produce Hydrogen.

Re: ZEROe: Hydrogen-hybrid aircraft concept

#73

Post by filleokus »

ib84 wrote: post #70

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...

Re: ZEROe: Hydrogen-hybrid aircraft concept

#74

Post by Symmetry »

liability wrote: post #38
mattashii wrote: post #8

Earlier quoted context omitted.

> 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, altho…

> start from CO2 Why would that route even be taken though? Biofuel for jet engines is proven technology in limited use for many years now. Let plants deal with the CO2, since they're good at it, then process the resultant vegetable oils to produce a suitable diesel or jet fuel. https://en.wikipedia.org/wiki/Aviation_biofuel

Biomass fuel production averages 1 watt per square meter compared to the 100 watts per square meter that solar power gives. Before fossil fuels civilization was in many ways energy constrained, forced to make harsh tradeoffs in how much land was devoted to forests for heating/iron production and how much to farmland for food.

Re: ZEROe: Hydrogen-hybrid aircraft concept

#75

Post by Yetanfou »

xoa wrote: post #13
Yetanfou wrote: post #6

Earlier quoted context omitted.

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.

Thanks for this reply as well. But batteries will cover most land use, and going by sources like the EIA [1] the primary source of anthropogenic N2O emissions is overwhelmingly agriculture, at 70+%. Other sources indicate that may have fallen somewhat since then, but even so everything I can find indicates fossil fuel combustion is still only around 10%. And of that air travel will be single digits. Not nothing, but…

I don't think hydrogen is a good energy storage solution. I do see its advantage over hydrocarbons for certain applications but the difficulties in storing hydrogen - a small molecule which is sort of an escape artist - make it less than ideal for many purposes. Fuel cells can get contaminated unless they're run with pure hydrogen and oxygen. In applications where hydrogen is already available - e.g. H₂-LOX fuelled rockets - it makes sense to use fuel cells. It might be possible to run aircraft using H₂-fed fuel cells if these can be made powerful and light enough to fit the application, the advantage over battery-electric here is that the energy density of liquid hydrogen is much higher than that of current battery technology. For the rest - cars being a good example - I think batteries are currently a better solution.

Large scale energy storage is probably handled better using either redox flow batteries [1], hydro storage systems or energy storage vaults using concrete blocks which are lifted when there is too much energy available, lowered when energy is needed.

[1] https://en.wikipedia.org/wiki/Flow_battery

Re: ZEROe: Hydrogen-hybrid aircraft concept

#76

Post by jakozaur »

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.

Re: ZEROe: Hydrogen-hybrid aircraft concept

#77

Post by Qwertious »

jakozaur wrote: post #76

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…

"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.

Re: ZEROe: Hydrogen-hybrid aircraft concept

#78

Post by Qwertious »

liability wrote: post #38
mattashii wrote: post #8

Earlier quoted context omitted.

> 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, altho…

> start from CO2 Why would that route even be taken though? Biofuel for jet engines is proven technology in limited use for many years now. Let plants deal with the CO2, since they're good at it, then process the resultant vegetable oils to produce a suitable diesel or jet fuel. https://en.wikipedia.org/wiki/Aviation_biofuel

Speaking generally about biofuel, it's a terrible idea - it's taking farming output and turning it into fuel, which is a bad idea because 1) it's unreliable and climate-dependent, and 2) we're basically just turning oil into plants and then turning the plants back into oil.

Re: ZEROe: Hydrogen-hybrid aircraft concept

#79

Post by usrusr »

ncmncm wrote: post #47
m4rtink wrote: post #43

Earlier quoted context omitted.

Not to mention hydrogen fires being invisible to unaided eye in daylight.

Hydrogen at atmospheric pressure is hard to ignite in uncontrolled circumstances. It wants a specific gas/air ratio.

Thought experiment: how close would the Hindenburg have been to missing that specific ratio?

The thing is, no matter how far you are overshooting or undershooting that ratio, as soon as you are doing both there'll be a boundary where it's matching.

Re: ZEROe: Hydrogen-hybrid aircraft concept

#80

Post by rbanffy »

JAlexoid wrote: post #60
liability wrote: post #39

Earlier quoted context omitted.

> for a very specific number of hours Unless you plan on throwing away the planes after one or two flights, those tanks will be filled with hydrogen for tens of thousands of hours over their lifespan. Perhaps they have light weight alloys that can cope with this though, I'm no metallurgist..

I never addressed the lifespan of containers, that's not same as hydrogen leakage.

Still embrittlement is an issue. How long until the hydrogen tank needs replacement?

Liquid per liquid, why not liquid methane that's far easier to work with and can be manufactured at zero carbon emissions.

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