Glossary / Batteries and storage
Iron-air battery
A battery that draws electricity as iron rusts in air and turns the rust back into iron when charged. Its materials are extremely cheap, suiting it to storing energy for days.
On discharge iron oxidises to iron hydroxide — rust; on charge it is reduced back to iron. The positive side uses oxygen from the air, so the materials are essentially iron, water and air. Research dates back to the 1970s; a 2015 review by Richard McKerracher and colleagues identified hydrogen evolution during charging, which wastes energy, and the durability of the air electrode as the main problems[1].
Only about half the energy put in comes back out, but it is so cheap that it is being tried for long-duration storage, covering days when solar and wind fall short.
Related terms
- Round-trip efficiencyThe share of the electricity put into a battery or other store that can later be taken back out.
- CurtailmentSwitching off or reducing solar or wind output that could have been generated, because demand or grid capacity is insufficient.
- Sodium-ion batteryA battery that shuttles sodium ions instead of lithium. Its materials are plentiful and cheap, and it is entering use in grid storage.