> producing hydrogen on a scale sufficient to back up the entire world electricity system is going to require electrolyzing the ocean This statement seems fals

> producing hydrogen on a scale sufficient to back up the entire world electricity system is going to require electrolyzing the ocean This statement seems false unless you take it to somewhat tautologically mean that electrolysis could use seawater as an input. The quantity of water in the ocean is vast, we could remove enough hydrogen to store 5 years of world energy usage and that would still be a tiny fraction of the water in the ocean. Less than 0.0001%, probably less than that. * Liquid water in the ocean 1.37e21 kg * Roughly 1.37e20kg of hydrogen * Roughly 120 MJ of hydrogen/kg * Annual energy usage is 5.387e14 MJ * So we require roughly 4.489e12 kg of hydrogen, or 0.00000003% of the hydrogen in the ocean. I feel like most of the "real costs" of green hydrogen are overstated. There don't seem to be any actual impediments. It's true that current prices are high but hydrogen electrolysis presently costs maybe 5-7x what natural gas does for unit energy. This is expensive but economies of scale have to at least cut that in half if we did it at scale and it's very much within reach. (And it seems plausible that economies of scale cut it down even further.) Yes, people are balking but that's why we need to just subsidize it until costs come down.