Crust iron is all oxide. Fe at 5% average. In some locations obviously more concentrated up to 90% ore. Not all sites are viable for mining, and this is very important to understand. Just because there is plenty of iron out there doesn't mean all of it is commercial grade.
This means energy input to turn iron oxide into iron, which the article claims could be used as fuel and/or long term energy storage.
-Fuel I don't believe for a second.
-Energy storage it's a maybe. It needs to commercially beat plenty of options. Which to me seems unlikely since the path still includes heat and steam engine which would incurr at a cicle loss of at least 50%. And this being conservative etc. Would mean a steam engine operated in a very narrow power band - which would mean a baselevel powerplant not a peaker powerplant. And didn't yet consider other possible losses, as for one, the Fe degradation over time. Energy cycles that count on heat and engine are wasteful. Could this waste be compensated by a much cheaper capex and/or opex relative to Li or similar batteries? That's a big Maybe.
I myself want to believe there is a solution to renewables intermittency. But on this one in particular, I'm quite bearish for the reasons above.