Battery Technology

Enabling a 100% Renewable Grid

Transforming the grid to be fully renewable

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 our iron-air technology is optimized to store electricity for 100 hours at system costs competitive with legacy power plants. This product is our first step to tackling the biggest 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.

Technology Applications
A Better World

A Closer Look

The Battery Cycle
  • 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
Our modular, scalable multi-day storage system

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.

Our battery systems can be sited anywhere, even in urban areas, to meet utility-scale energy needs. Our 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.

To learn more about how our battery system works, please watch this video produced by ClearPath.

Key Advantages of Our Technology


Stores energy at less than 1/10th the cost of lithium-ion battery technology.


Pairs well with lithium-ion batteries and renewable energy resources to enable optimal energy system configurations.


Delivers 100+ hour duration required to make wind, water, and solar reliable, year round, anywhere in the world.


Can be sited anywhere for utility-scale needs.


Materials and designs with global scale needed for zero carbon economy.


No risk of thermal runaway. No heavy metals. High recyclability.