Form Energy -iron-air battery

Form Energy’s new ‘iron-air’ battery, it can store electricity from wind or solar power stations for days at a time and then discharging it to the grid as needed.

To run the grid reliably and affordably, we need new cost-effective technologies capable of storing electricity for multiple days. We conducted a broad review of available technologies and have reinvented and optimized the iron-air battery for the electric grid.

The active components of our iron-air battery system are some of the safest, cheapest, and most abundant materials on the planet — low-cost iron, water, and air. Iron-air batteries are the best solution to balance the multi-day variability of renewable energy due to their extremely low cost, safety, durability, and global scalability.

Our first commercial product using iron-air technology is optimized to store electricity for 100 hours at system costs competitive with legacy power plants. It helps with the key barrier to deep decarbonization: making renewable energy available when and where it’s needed, even during multiple days of extreme weather, grid outages, or periods of low renewable generation.

  • The basic principle of operation is reversible rusting
  • While discharging, the battery breathes in oxygen from the air and converts iron metal to rust
  • While charging, the application of an electrical current converts the rust back to iron and the battery breathes out oxygen

Each individual battery is about the size of a washing machine. Each of these modules is filled with a water-based, non-flammable electrolyte, similar to the electrolyte used in AA batteries. Inside of the liquid electrolyte are stacks of  between 10 and 20 meter-scale cells, which include iron electrodes and air electrodes, the parts of the battery that enable the electrochemical reactions to store and discharge electricity. 


These battery modules are grouped together in modular megawatt-scale power blocks, which comprise thousands of battery modules in an environmentally protected enclosure. Depending on the system size, tens to hundreds of these power blocks will be connected to the electricity grid. For scale, in its least dense configuration, a one megawatt system requires about an acre of land. Higher density configurations can achieve >3MW/acre.

Battery systems can be sited anywhere, even in urban areas, to meet utility-scale energy needs. Batteries complement the function of lithium-ion batteries, allowing for an optimal balance of our technology and lithium-ion batteries to deliver the lowest-cost renewable and reliable electric system year-round.