this post was submitted on 10 Aug 2023
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You'd need huge cryogenic tanks due to the volume density of hydrogen over kerosene. Good for rockets that you can jettison tanks from, but less so for planes. I just don't see it ever being practical for aviation over just creating our own hydrocarbons out of something else. Either catalyst based or otherwise. That's potentially carbon neutral as well.
Edit: my comment, but with numbers https://pubs.aip.org/physicstoday/article/74/9/11/928294/Hydrogen-as-an-aviation-fuel It's not a problem with how heavy the fuel would be or just how much space they'd take. It's how heavy the damn tanks would need to be and how much of the aircraft would be devoted to them on long distance flights.
Even if it takes more space, there are still benefits over biofuels.
The hydrogen can be created using electricity. Currently it is not very efficient, but only uses electricity and water. Electricity can come from de carbonated (/low carbon) sources.
And a fuel cell will use that hydrogen to generate electricity by combining the hydrogen into water with outside oxygen.
For the biofuel, it's a big climate hoax. The issue with bio fuels, is that the energy required to produce them is huge. It required bacteria producing carbon emissions, and the fuel also produced carbon emissions. Whatever entered that plan, will get out, and even more because of the transformation. (i don't remember which video from Undecided with Matt Ferell was about biofuels). Tho maybe it could be used for something. To get slightly less carbon emissions than with normal fuel.
There may also be a solution with batteries. However the energy density for them is lower compared to hydrogen. Tho, there may be some battery innovation I saw passing by which could be pretty interesting.
CO2 to syngas to hydrocarbon fuels is probably a better carbon zero process, considering we will need to do a ton of cdr anyway....although doubt energetics and economics would be great. Hydrogen, just like biofuels today are anything but carbon neutral, and efficient electrolysis might never happen. Hydrogen production will also face water shortage issues and in general electrolysis requires pretty low tds water which is not trivial to source...not sure what's best way to get carbon zero airplanes honestly...
i think the important thing to consider is that not EVERYTHING has to emit no carbon… it’s perfectly acceptable (IMO) to make air travel carbon neutral by eg carbon capture, etc… sometimes it’s just not efficient to either carry around carbon neutral but not dense fuel, or capture and carry your waste with you
it’s shit that carbon offset programs have been hijacked :(
This seems to be a key point ppl miss. There is still quiet a big question if cdr and storage can be net negative...for example one place we want to store co2 is in saline basins, but this will require disposal and treatment of the brines removed from the basin...which might emit might end up emmiting as much co2 as ends up being stored in the saline basin. There is a paper on this issue....
If we're able to make hydrocarbon-synthesis from CO2 efficient.... we're still going to need to source the hydrogen somewhere.
But if we do that using electrolysis (with renewables), and are able to create more energy efficient CO2 capturing processes, I could see synthetic hydrocarbons as a viable fuel option in the future. The thing is: They're stupidly good at being stable, energy dense, energy carriers. We also have a lot of infrastructure in place to handle hydrocarbons already.
In principle, synthetic hydrocarbons could be part of a zero-emission cycle, where we capture CO2 and electrolyse hydrogen with renewable energy, and use the hydrocarbons as an energy carrier. But if we go that way, we're definitely going to have to research efficient hydrogen production, and probably storage as well.
There was an article around here about Germany ditching hydrogen for their trains, which, if justifiable, seems damning for anything in the air.
As someone from Germany that's the first time in reading that it was ever a thing for trains
Pretty much all our rails have electric lines on top and most trains are working electrically already
I really don't see a point to waste hydrogen on cars or trains where pure electricity is working fine
Planes seems to be the main target that absolutely will never work electrically so it needs hydrogen - there even was an article about a ship running on batteries a couple of days ago
The thing with trains is twofold: First of all, it's relatively easy to ensure that a train is more or less always hooked up to the grid (lines over the tracks). That means it can charge almost constantly, and doesn't need a large battery.
The second thing is that the energy required to run a train scales very slowly with mass, because there is almost no rolling resistance (steel wheels on steel tracks have that advantage). That means you can increase the base weight of the train a bit without worrying about increased energy consumption.
Hydrogen can compete in applications where you need large amounts of energy, that needs to be transported, and where you don't have regular access to the grid. Prime examples could be long-distance shipping, flight, and long-distance trucking through areas with little or no electric infrastructure (e.g. rural Australia).
It's no more of a problem than dealing with LPG, surely? Pressurise it for storage.
The difference is the 'L' in LPG. It turns liquid at a relatively low pressure and takes up much less space then. Hydrogen does not do that, so it has to be stored at a much, much higher pressure. For example, a medical oxygen bottle or a scuba tank has around 200 atm of pressure. For cars, hydrogen is usually stored at 700 atm. And the pressure inside an LPG tank is around 8 atm at room temperature.
I think it is, not sure but it requres bigger pressure and hidrogen is smallest atom that escapes even from high presure tanks.
You can't keep liquid hydrogen by pressure alone and even as a liquid it's volume density it's very low compared to other liquids.
A couple issues have been mentioned, but what hasn't been mentioned is that hydrogen is difficult to store, because the molecules are small enough do migrate through most containers and escape. If your container is made of metal, you also get something called hydrogen embrittlement which breaks your container over time.