Technology

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...

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).

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.

Same goes for large container ships. It won't make sense to use batteries unless there are significant breakthroughs in capacity technology.

Sadly industrial hydrogen production is done by reforming petroleum with steam which releases huge amounts of CO2.

Yes, it's very flammable. But it's also very light. Lighter than Oxygen. And the molecules are small which means most air tight applications don't work well. Even the tanks they make now still has this issue where hydrogen molecules can escape through the barriers over time.