I really doubt the claim about 80% efficiency of converting iron oxide back to iron. Industrial processes widely used today are based on fossil fuel (natural gas or coal). There is some research on electrolysis, but this process is not an easy one either: you have to heat oxides up to 1600 C, apply electricity, extract resulting iron, cool it down, powder it. Each step takes energy, so I guess the 80% are only for the electricity part, without accounting for other required steps.
And how do they get the 40% round-trip efficiency? Even if we assume the 80%, modern gas turbines have efficiency of up to 38%. In complicated combined cycle mode plants efficiency can be boosted up to 60%. And it is natural gas, a very convenient fuel to work with.
And how do they get the 40% round-trip efficiency? Even if we assume the 80%, modern gas turbines have efficiency of up to 38%. In complicated combined cycle mode plants efficiency can be boosted up to 60%. And it is natural gas, a very convenient fuel to work with.