BTW, if you object to hydrogen on these grounds, you must also object to nuclear on these grounds, and more strongly. This is especially the case if you imagine a nuclear powered world economy. You need to imagine a jump in technology more radical than for hydrogen storage -- either massive scale up of seawater uranium extraction (many orders of magnitude, from gram scale to megaton scale) or use of breeder reactors instead of burner reactors.

Factories for iron-air storage are being built today, to start supplying grid-scale storage in 2023. Everybody knows the demand is there and will remain there, so there is plenty of capital for anything known to work. But it takes time to build out.

After costs shake out, build-out will concentrate on the cheapest alternatives, but everything already built will still work, and still be used, because the cost is capital cost. It will be a long time before the storage market is saturated and storage providers have to compete on prices.