Image: Xcel Energy
Google has signed a definitive agreement with Xcel Energy to deploy a 300 MW / 30 GWh iron-air battery system in Pine Island, marking what is set to become the largest battery installation globally by energy capacity ever announced.
The project will utilize long-duration energy storage (LDES) technology developed by Form Energy and represents a major step forward in stabilizing renewable-heavy power grids. Located in Minnesota, the system is designed to support growing electricity demand driven by AI data centers and other energy-intensive digital infrastructure.
A New Clean Energy Framework
The deployment is a cornerstone of a newly established “Clean Energy Accelerator” agreement, a regulatory framework that enables Google to directly cover project costs. According to Xcel Energy, this structure ensures that the 100-hour storage system — paired with 1,400 MW of wind and 200 MW of solar generation — will not increase electricity rates for residential customers.
The initiative highlights how large technology companies are increasingly taking a direct role in financing grid infrastructure to secure reliable clean power supplies.
While lithium-ion batteries are widely used for short-duration applications — typically four to eight hours — they become prohibitively expensive for multi-day storage. In contrast, Form Energy’s iron-air technology is designed to store renewable electricity for up to 100 hours at system costs competitive with conventional thermal power plants.
This capability is critical for addressing renewable intermittency, particularly during extended periods of low wind or limited sunlight.
The iron-air battery operates through a reversible rusting process. Each cell contains thousands of iron pellets that react with oxygen from the air to form rust during discharge. When charging, the system removes oxygen, converting the rust back into iron. By carefully controlling this electrochemical reaction, the battery stores and releases electricity over extended periods.
Although less energy-dense than lithium-ion batteries, iron-air systems are well suited for large-scale, grid applications where space constraints are less critical.
According to Form Energy, a single battery module is roughly the size of a side-by-side washer and dryer and contains approximately 50 vertically stacked, one-meter-tall cells. Each cell includes iron and air electrodes that enable the electrochemical reaction, along with a water-based, non-flammable electrolyte similar to that used in AA batteries.
As electricity demand accelerates — particularly from AI-driven data centers — the Pine Island project could serve as a blueprint for how hyperscale technology companies firm renewable generation with long-duration storage. By integrating multi-day battery systems with large-scale wind and solar resources, the project demonstrates a potential pathway toward maintaining grid reliability while advancing decarbonization goals.
