Yes, I’m aware of what Fuel Cell Technology is, but it still needs to use Hydrogen in it’s liquid state.
Liquid Hydrogen has a very low density value as it is, if it were to be used in it’s gas state, you’d need a gigantic tank to store enough Hydrogen to fuel a small car for a few minutes. Maintaining it in it’s liquid state is a must, and that’s the major reason why the technology itself is so expensive.
It doesn’t matter which kind of technology you use; there’s no realistic way to power anything using Hydrogen gas. The submarine you posted, for example, uses LH for storing (as well as any other Hydrogen-powered prototype ever created).
By saying Ethanol/Oil are alternatives to it, I don’t mean to imply that they’re all combustible fuels. Just that they’re different ways of acquiring energy to power something, with those two being largely cheaper than Hydrogen.