I
know I'm missing something obvious here, can someone close to this tech help me out? What problem does this solve? For reference, I'd like to compare this to a hydrogen cycle, which is apparently already a subsystem of the proposed process used to reduce the spent iron. I went to the "Why iron?" section of the web page and got the following points:
'CO2 free' - H2 cycle systems are also CO2 free
'Compact' - the energy density of iron is already pretty low and the proposed machinery also doesn't seem very compact. Maybe storing uncompressed H2 would be somewhat inconvenient depending on your location, but you can always compress it. And if you need longer term storage, you can actually make hydrocarbons from it, although that wouldn't technically be CO2 free (only CO2 neutral if you use captured carbon)
'Cost-effective' - this system seems way more expensive, per kWh and in absolute terms, than gaseous cycle concepts.
'Easy to store and transport' - the iron is certainly not easy to transport, nor is the machinery using or recycling it. It is easy to store safely, just not efficiently.
'Scalable' - while iron is abundant on Earth, most of our iron is actually at inaccessible depths, so we're stuck with traditional mining. If you think iron is cheap, you haven't tried to use it as a building material recently. Cheap and abundant metals would be calcium or potassium. Even cheaper, again: H2.
'Safe' / 'Commodity' - true, but how relevant are these, really?