[Tagbert]

Why is it “waste” rather than just aluminum which hasn’t been recycled, yet? The embodied energy from aluminum and iron metal is very high. It takes large amounts of energy input to convert the source ores into pure metal. Using that metal as a fuel seems like a step backwards.

This article talks about using iron as a fuel and while it admits that it takes electricity and hydrogen to conver iron oxide to iron and that the process is inefficient, it seems to just handwave that away and go into how great a fuel source iron would be.

Seems very “perpetual motion” to me.

[jmopp]

I always thought of technologies like these as potential solutions to the grid-storage problem: excess solar and wind energy can be put into electrolysis, and then the metals can be burned to provide base load power — while keeping lithium for portable use-cases

[kaliszad]

I would rather use a process that uses more abundant elements and can be used to (re)produce electricity directly without burning: https://news.ycombinator.com/item?id=37548917 Generally, it is a good idea to lower the temperature needed to produce your fuel as that usually is just waste heat. Melting iron oxides needs very high temperatures which makes everything more complex.

[NikkiA]

Still magnitudes less efficient than just building gravity batteries.