Iron Fuel Shows Its Mettle
17th June 2024
Iron is one of the most abundant metals on Earth, and the most produced. It has an energy density of about 11.3 kilowatt-hours per liter—better than gasoline. Burning iron powder produces heat that can be used directly or converted into electricity by a steam turbine, leaving behind iron oxide, or rust. This can later be reduced—that is, the oxygen can be stripped away—back into iron powder. “You can think of iron fuel as a clean, recyclable coal,” says Bergthorson.
Iron oxide can also be reduced to iron using hydrogen. Hydrogen is already a carbon-free green fuel if produced by splitting water using renewable electricity. But it is also an ultralight, voluminous gas, so it must be converted using high pressures and extreme cold into liquid, which then has to be stored and transported in special containers. Iron, by contrast, is already moved in dry containers for a lower cost.