Process H2 generated at point of use makes sense (e.g. for steel production), but the whole “H2 as a fuel” story is simply nonsense to keep the legacy fossil fuel companies happy.
Fun fact: currently 95% of hydrogen is produced from fossil fuels. This might be a clue as to why such a dumb idea is still around.
Synthetic methane and other hydrocarbons are also ideas that are floated. But those need hydrogen as an input anyway. They also need a source of carbon, which is too difficult to extract from the atmosphere. So using the hydrogen directly may be more feasible.
Actually, there are many carbon free fuels. It is hard for any to use as jet fuel. An example fuel that has much better properties than hydrogen is for instance sodium. Making a sodium fuel cell does not need any rare earth metals such as platinum, sodium is solid at room temperature, does not produce any fumes, better energy density than liquid hydrogen, the resulting NaOH sodium hydroxide can be recycled into sodium (with hydrogen as a byproduct) by the Castner process. Hard to say, if this could use the water vapor present in the atmosphere, if it did, you would also have to think about what to do with the caustic hydroxide solution. Probably, that would be neutralized quickly in the atmosphere but at ground level or above cities could "raise eyebrows" even though burning leaded petroleum in aviation still seems to be a thing...
Of course, for almost all uses, the volumetric efficiency is important because you have to create bigger tanks, which if they have to contain liquid hydrogen, are usually heavy and costly.
Short-range aircraft will probably switch to batteries in the coming decades, because the prototypes are already flying[1] and battery and electric motor tech is ever-increasingly ubiquitous and mature.
[0] https://en.wikipedia.org/wiki/Greenhouse_gas_emissions#Aviat...
[1] https://www.cbc.ca/news/canada/british-columbia/vancouver-el...
It's not just long haul flights out of reach of battery powered aircraft. Even a regional flight like Seattle to San Francisco cannot be feasibly done with batteries. This is fundamentally due to the energy density of lithium ion batteries, no amount of engineering can change the chemical limitations at hand: https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3...
As far as I understand, the problem is not just the speed, but the thermal management. IIRC the impact on battery life is not as bad if cooled properly.
> and a plane needing a new set of batteries after a few hundred flights due to aggressive wear from fast charging is unacceptable.
That's an economics question. How much does it cost to get that battery replaced and charged over its lifetime versus the alternative.
> This is fundamentally due to the energy density of lithium ion batteries, no amount of engineering can change the chemical limitations at hand
That's the beauty of battery technology, you can substitute. Cobalt a problem? Fine we can make batteries with out it. Lead-acid not suitable, fine here's lithium ion. Lithium ion not good enough, find we'll find a better battery.
Hydrogen however is just that: hydrogen. Notice how low it is on the energy per volume scale. You can't substitute it out for anything. The volume requirement is what's going to kill you with hydrogen.
Well, then get back to us when you find that battery. Unfortunately, simply finding a new battery chemistry that has an order of magnitude better energy density is easier said than done.
> Hydrogen however is just that: hydrogen. Notice how low it is on the energy per volume scale.
You're looking at uncompressed hydrogen. Hydrogen at 700 bar has several times better energy density than lithium ion batteries, and over 1000x as much energy by mass. And lower mass means you need less fuel since the craft is lighter.
Will point out takes a decade now to produce a blue print aircraft. So if we started designing one now it would be flying when 2033? China rolled out a high speed rail network in ten years. You could do that in the US and other places.
Notable point. The complaints I hear about high speed rail in Europe is tickets cost more than airplane tickets and the trains are always full. The explanation is the ergonomics and logistics of passenger aircraft sucks.
H2 has a daily boil off 5 times greater than LNG. https://www.sciencedirect.com/science/article/pii/S277265682...
Not only that, liquid H2 has worse energy density than LNG. So again, you're spending more units of energy to comparatively more less units of energy.
You will need bigger tanks but the fuel is much lighter. It is a solvable problem.
>You can liquefy hydrogen on the spot. You don't need to move LH₂ around.
Why are you liquefying H2 if you are using it right away and or not transporting it? Liquefaction is to optimize for storage. You're all over the shop.
It has been invented, the majority are in China and Japan if I remember rightly.
Similarly, cargo ships can't run on batteries, but could fairly trivially be switched to hydrogen with only minor loss in storage capacity (1-5%).
The benefit of hydrogen is that it was functioning just fine in the 1960s, there aren't any outright technical showstoppers here; just financial problems and technical problems that are hard to solve cheaply.
I'm not saying that hydrogen is the best solution (if synthfuel pans out then it'll be a perfect drop-in replacement for existing jet fuel), but it's a solution that exists today. It's there if we care.
Obviously we don't care, since coal plants are still around, but if we genuinely wanted to stop using fossil fuels ASAP then it would permit us to keep using planes/cargo ships.
If I were to bet, I would say that converting hydrogen to kerosene will be far cheaper and more efficient than trying to power long distance flight with hydrogen
H2 molecules are extremely small -- storing them without loss is heavy and volumetrically expensive, making it implausible for any aircraft.
The same factors apply to ships, pipelines etc because space for fuel is space that does not contain high value cargo.
Ships don't care about weight. The cooling infrastructure or heavy steel tanks are possible.
Have you looked at how high the containers are stacked on a container ship? Space taken up by fuel is space that can't be sold.
Source: we partner with commercial shipping companies and spend time not just talking to the commercial people but on the ships themselves.
Jet fuel is ludicrously energy dense, to the extent that it's easy to underestimate how much energy you need: at any reasonably-sized airport, if you want to replace the current fleet then you need to be talking about roughly a power station's worth of continuous energy delivery into aircraft fuel tanks. That's doable with jet fuel because you're not climbing out of an energy well just to get hold of the fuel. You just separate it out, and the problem becomes pure logistics.
With H2, the volume you need and the added storage complexity means the current logistics becomes a rounding error in comparison to how on earth you get the gigawatts to churn feedstock into gas.
You could do it, but you'd want nukes on-site to do it.
The shipping industry is investigating making ammonia from the hydrogen and then using that in fuel cells; it has the advantage that it's easier to handle. https://maritime-executive.com/article/highest-power-output-...
This doesn't make any sense: free trade is not a magic spell against the desires of imperialism, and the US embargoed Japan slightly before Japan attacked the US (but long into Japan's war with China).
I am glad that decentralised electrical from solar and wind can fully replace the old system and look foward to a new many-noded culture which can allow all humanity to flourish.
Sorry. But there’s no reason so many people need to fly (consultants, I used to be one racked up a few hundred thousand miles) besides leisure or critical travel. And it should reflect in the price so tickets aren’t $150 to be crammed in like cattle.
And yes it should be rare to fly until we figure out cleaner fuel methods. Just my hot take.
Is the problem that wind isn't reliable and you might go days without it? Or you wouldn't fit in ports or other areas with a big turbine sticking out? Or is there some other practical problem.
Further, the ships take a significant amount of energy to get going, so much of that initial acceleration could be handled by strong tug boats which would then be immediately recharged.
Might solve problems for countries that have lost their own manufacturing capacity because shipping products gets way less appealing.
Ammonia (a toxic gas) as a fuel is an insane idea and will lead to needless deaths.
Efuels are incredibly inefficient. Hard to justify paying 10x the price.
Ammonia or synfuels are not the only alternative. The elephant in the room, the one fuel that is being used today is biofuel.
I was merely stating why cellulosic ethanol is not the major source of biofuel; because corn is heavily subsidized and produces a cheaper product, hence nobody wants to buy the more expensive product.
That's not a technical problem, it's an economic one. And the subsidies where to change we would see less from corn and more from other sources.
Cellulosic ethanol is an idea brought up as a solution to the problems of corn ethanol. Ironically, by the George W. Bush administration. Unfortunately, nothing has materialized in any meaningful quantity.
And FYI, they’d be subsidizing it heavily if any meaningful quantity of cellulosic ethanol could be produced. So bringing up that part doesn’t mean much. But cellulosic ethanol production never happened and so far there is no reason to believe it is possible.
I'm not so sure. That would introduce competition for the corn ethanol, and there's a fairly large constituency (those having their corn production subsidised) that would oppose this kind of measure.
Aircraft will remain liquid-hydrocarbon-fueled for the foreseeable future, even if the fuel production transitions to a synthetic process vs. refined crude oil.
Making more room for the tanks means either less cabin/storage and/or bigger cross-section and increased drag.
"Long-distance" is a subjective term. There is an ever-increasing distance for which batteries are doable. Everything else is will be liquid biofuels, rather than efuels.
Biofuels are as green as the process making them. Electrify the equipment being used (something that's being done for reasons orthogonal to this) and you're already made the process more green.
Again, biofuels are not green. The process that makes them involve vast quantities of land and resources. It is in fact a very inefficient and resource intensive idea. It is actually much worse than what it takes to make e-fuels.
There needs to be more productive uses of this free electricity and I imagine H2 is one of them.
NB: Batteries won't solve this unless prices dropped astronomically. The issue isn't overcapacity on a day by day basis, it's seasonal overcapacity. Areas further south are less affected by this, as there is less seasonal variation in solar output. You're not going to charge a battery then discharge it weeks later - the economics don't make sense.