It is correct to say hydrogen is principally a storage medium, although its use as direct feedstock will always be comparably important. The rest is questionabl

It is correct to say hydrogen is principally a storage medium, although its use as direct feedstock will always be comparably important. The rest is questionable. You get back the ("enormous") energy used to strip oxygen off of water molecules, yielding hydrogen, when you react the hydrogen again with oxygen. Of course by far the most cost-effective way to generate that ("enormous") energy is with enormously cheap solar panels and wind turbines. (The round-trip efficiency of hydrolysis and combustion is fairly low because the hydrogen recombines to H2, yielding heat during electrolysis, then the hydrogen may need to be liquified for transport, and then the H2 may need to be split again when making H2O. Perhaps surprisingly, low round-trip efficiency doesn't matter very much because solar has become so cheap; you just add more panels to make up the difference.) There is no plausible scenario where fusion or fission provides a substantial fraction of the energy used. Fission is enormously more expensive than renewables for the same output -- beyond order-of-magnitude more expensive. Fusion, if ever made to work, would cost another order of magnitude beyond that. Things >100x as expensive as practical alternatives are rarely seen used. AA batteries and bottled beverages are exceptions. And, of course CO2 is a pollutant. The most dominant one, it has turned out. Taxing release of it, and the revenue used to build out renewables, storage, and transmission lines cannot come soon enough.