Hydrogen leaks much more easily than bigger molecules. It's entirely possible that existing storage systems designed for natural gas would be completely unusable for H2.

You've also got to account for hydrogen embrittlement, where the small size of the hydrogen molecule means that under pressure it works its way into the crystal lattice of the metal of the container itself, and changes its mechanical properties.

Leaks and embrittlement are always trotted out as big problems.

But they are a product of high pressure. Keep pressure low and ensure positive airflow in any closed space, and there is little to worry about.

That precludes reusing existing infrastructure at the same pressures as today, though. For the same pressure, H2 will leak worse than natural gas.

And it's not just a pressure problem, either: embrittlement will happen at room temperature and pressure, just through diffusion.

Embrittlement is a problem at high pressure because the stuff being embrittled has to be strong to contain pressure. Take away the pressure, and it only needs to not have holes in it.

For decades, lamp gas -- carbon monoxide and hydrogen - was piped to homes, factories, offices, and ... street lamps, in cast -iron pipes. Then they switched to methane, same cast-iron pipes. They started out pretty brittle, really. Still in use, though.

Higher pressure is necessary to keep costs down, smaller pipes and higher pressure is what makes sense for vast majority of liquids and gases.

There will be no need to pipe H2 long distances. It can be made locally from wired in power.

Where a large amount must be handled, underground caverns at low pressure and LH2 tanks at ambient pressure will be favored.

Basically, everything about it is hard. Very high pressure and low temperature, leakage, steel walls get brittle, etc. It's a nightmare, doable, but very hard to scale.

The most promising solutions I've seen are taking advantage of the fact that single H+ “dissolves” into metal under pressure. You store that saturated metal and heat it when you want to release it. That way energy density starts to make sense. This video shows one such approach:

https://www.youtube.com/watch?v=M0fnEsz4Ks0

Binding it with carbon seems promising as well, but I wouldn't bet on simply trying to jam it as a gas in a tank.

But I'm not an expert, just very interested on the subject for many decades.

How is binding it with carbon different from just using methane? I guess you reuse the carbon instead of emitting it into the air?

"Binding" is probably the wrong term to use. Its likely absorption with a bit of adsorption. Not the same as a covalent bond.

Of course, imagining carbon capture from the atmosphere. All of that is really hard to do economically