On a flat stretch of land in southeastern Minnesota, Google is building a new facility considered one of its most technologically ambitious data centers yet, designed to run almost entirely on renewable energy. This data center located on Pine Island will jointly develop supporting wind power and photovoltaic infrastructure with utility giant Xcel Energy. It plans to obtain up to 19 GWh of zero-carbon power for a total of 1.9 GW, and is equipped with a long-term energy storage system with "Rust" as the core.
This is Google's first data center project in Minnesota. It will rely on iron-air battery technology developed by Form Energy to achieve long-term energy storage of up to 100 hours, with a total energy storage scale of up to 30 gigawatt hours, providing support for all-weather cloud computing and AI businesses. In the data center industry, how to provide stable power for high-load facilities without relying on fossil fuels has always been a problem. Google is trying to provide multi-day stability for a high-proportion renewable energy grid through large-scale deployment of iron-air batteries.
Different from the current lithium-ion batteries widely used in mobile phones, electric vehicles and grid-level energy storage, Form Energy's technical route abandons the migration mechanism of lithium ions in the electrolyte and instead utilizes reversible "rust-reduction" chemical reactions to store and release energy. During the discharge phase, the battery generates iron oxide by oxidizing oxygen in the air with small iron particles, while releasing electrons to form an electric current; during the charging phase, electric energy is used to reverse this process and reduce the "rusted" iron oxide back to metallic iron, thereby completing a cycle.
From an energy efficiency perspective, iron-air batteries have round-trip efficiencies of about 50%–70%, significantly lower than the 90%-plus levels typically found in lithium-ion batteries. But its advantage lies in cost and duration: the energy storage cost of about US$20 per kilowatt-hour is roughly only one-third of the equivalent lithium-ion solution, making it more economical in large-scale, long-term energy storage scenarios, especially suitable for power grids dominated by wind and solar power generation that need to balance supply and demand across days.
Minnesota has become one of the testing grounds for this technology. In addition to the Google project, a smaller demonstration project deployed by Form Energy in partnership with local utility Great River Energy is also under construction. The system has a planned energy storage capacity of 150 MWh and can continuously output 1.5 MW for up to 100 hours, providing long-term peak shaving and emergency support for the local power grid. The energy storage deployment of Google's Pine Island data center is enlarged by several orders of magnitude on this basis, aiming to push this experimental technology to a real industrial application scale.
In addition to the technical aspect, this project also introduces an innovation in policy and business model: a new electricity price structure design, aiming to accelerate the process of clean energy investment. This mechanism is called "Clean Energy Accelerator Charge (CEAC)" and is an extension and evolution of the "Clean Transition Tariff" (Clean Transition Tariff) piloted by Google in cooperation with Nevada NV Energy.
Under the CEAC mechanism, Google has committed to investing $50 million in Xcel Energy's Capacity Connect program to support distributed energy storage projects and deploy smaller battery systems throughout the grid to improve overall reliability and buffer the fluctuations of intermittent renewable energy. The goal of this type of structural design is to "open up a channel" for utility companies to more quickly promote the development and construction of clean power sources and energy storage facilities without breaking the regulatory constraints on electricity prices or increasing the burden on residents' electricity bills.
Google said that this cooperation demonstrates how large energy consuming companies can collaborate with utility companies to not only deepen the proportion of renewable energy in the power grid through innovative electricity prices and investment arrangements, but also promote the new generation of energy storage technology from experimentation to large-scale application. For Minnesota, this project provides a new paradigm for industrial electricity use: On cloudy days and windless nights in the future, what supports the stable operation of cloud computing and AI data centers may no longer be fossil fuels, but batteries that work based on the "rust reaction".