[hn_throwaway_99]

> It needs to prove that it can be competitive with the other methods.

I think the one thing is that iron storage would be a potential long term form of storage, while all those other methods that you mentioned are really short term, designed primarily just to deal with the daily peaks and troughs of renewable production, but not as much the "it's been completely overcast for 3 weeks" problem. The only other form of storage I'm aware of that is also long term like that is pumped water storage, and that is obviously very geographically limited.

[rsaesha]

If using Fe why not iron batteries? Keep the redox, remove the energy from the system via eletrical current instead of low efficiency heat, boiler and steam engine combo.

[hn_throwaway_99]

Great point. Fe batteries are very new so I'm not aware of the cost/benefit or if Fe batteries still slowly discharge over time, but yeah in both cases you're just oxidizing iron, so why not take the more direct route to generate electrical current directly.

[samus]

There are also applications where the desired output is heat, not electricity. In that case, iron fuel would be useful.