Iron-Based Hydrogen Storage

They don't know the reaction efficiency yet. I suspect the technique will be very lossy: more energy in, than stored, and by a dis-advantageous factor compared to eg conversion to NH or, storage in sintered metals as proposed for fuel-cell usage.

But, the great thing about steam is that its a really well understood technology so if this ISNT lossy, and doesnt require a huge energy imbalance to drive inward, its got a lot going for it.

Reconversion of rust back to Iron is also very energy intensive. So other parts of the cycle have huge costs.

A clever approach based on old technology to transport hydrogen indirectly rather than directly where it is needed using iron pellets, which are combined with steam on site to produce hydrogen.