"That rust can be regenerated straight back into iron powder with the application of electricity, and if you do this using solar, wind or other zero-carbon power generation systems, you end up with a totally carbon-free cycle."

Making solar panels is not carbon free. Making batteries instead of emitting gases is not carbon free. We still have to recycle those panels and those batteries and take in account the impact of it.

I feel like we are changing the place where gases are emitted or residues stored instead of making less cars, consuming less in general, etc.