Hydrogen is _really_ hard to store. It leaks from every container, transport and storage losses are just an accepted fact.
It might be a good option when we have so much renewables that we can't find any more batteries to shove it in. Then we can use it to store compressed hydrogen, that can be released as electricity from large-scale fuel cells during calm cloudy days.
Hydrogen is incredibly dangerous and bulky. Using it where you create it works well enough, but without some breakthrough in metal hydride storage or similar it's starting to look like a poor choice even against batteries if you want to move your energy around.
Stuff that can store as a liquid opens a lot of possibilities, although this probably means ammonia most of the time.
Storing energy as hydrogen involves a lot more than just a tank. Again, you obviously didn't bother reading up on this and you are guessing how hydrogen based energy systems work. You clearly don't.
Just FYI, hydrogen fuel cells are hydrogen-air batteries. There's no rational reason to reinvent the wheel for what is basically an inferior version of hydrogen fuel cells.
I would normally agree with you out of hand, but using hydrogen for temporary grid storage isn't as obviously stupid as, say, using it to power cars. Sure, most proposed uses of hydrogen are blatant red herrings invented by the fossil fuel industry, but not all of them.
If you're going to use electricity to make your hydrogen, you are certainly no better off than using it to charge a battery. Also, the energy density of hydrogen isn't exactly awesome either, and it's hard to store.
Okay, but now you just have some steam and heat floating around.
It's gonna dissipate pretty quickly, not a great way to store power for the medium-long term. Hydrogen separated from Oxygen is where the useful potential energy difference is.
The idea behind hydrogen fuel cell batteries is that you spend your cheap clean renewable energy to split H2O slowly when energy is available, and burn the hydrogen when you need bursts of power. If you burn the hydrogen right away, you're just un-doing the water-splitting reaction and you won't have anything to use for power when the cheap clean renewable energy is not available, like during the night for solar power.
I think that the usual way to get energy back out of the hydrogen is just to burn it and let the hot pressurized gas power a steam turbine, but don't quote me on that. Or try it at home; scalding and flash burns are good things to avoid.
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