Ultra-low-cost gigawatt-scale iron rust battery storage facility approved for construction in Minnesota

Gates and Bezos-backed startup Form Energy is one of the most exciting companies in grid-scale renewable energy storage, with a multi-day iron-air battery system that costs just 10% of lithium. A 10 MW/1 GWh demonstration system has now been approved.

To move large grids toward 100% renewable energy, grid operators need smart, affordable, practical and eco-friendly ways to store energy generated at inconvenient times and then use it when demand exceeds supply. Release it.

This needs to happen on different time scales; this grid smoothing needs to happen on a daily basis, and this is an area where the lithium "big battery" project already does a good job. However, lithium is not well suited to long-term storage; it is not suited to maintaining a full charge over days or months, so other slower bulk storage options are being developed to buffer the energy grid during multiple days of severe weather and renewable energy generation seasonal stagnation.

Form Energy is working in the multi-day space to commercialize a relatively simple modular battery solution based on the rusting cycle of iron. When charging these washing machine-sized battery modules, electricity is used to convert rust or iron oxide into metallic iron, releasing oxygen as a byproduct. Discharging a battery involves putting oxygen back into the system and turning metallic iron into rust, releasing energy in the process.

It is obvious at first glance that this reaction is slower than the instantaneous high-power discharge of a lithium battery. But it happens faster than you think; a complete discharge cycle takes about 100 hours, or a little over four days. This is exactly the sweet spot for multi-day batteries that cities need to provide a buffer against severe weather.

The advantages of iron-air batteries are simple and clear. Direct reduced iron is currently the cheapest form of iron and was previously used primarily for steelmaking. It's very rich and completely safe. The same goes for water and air, the other two main ingredients.

These batteries may take up some bulk - about an acre (0.4 hectares) of land is required to generate 3 megawatts - but they can last a long time and are completely recyclable, requiring only that the iron can be pulled out again and easily to sell it. The result is a levelized cost of storage (LCoS) that costs about 10% per kWh to store and release compared to a large lithium battery array.

After announcing a $760 million manufacturing facility in West Virginia earlier this year, Form Energy has now announced an impressive demonstration project: a 10 MW/1 GWh system to be built in Minnesota On 5 acres (2 hectares) of land near the Shelburne County Generating Station in Baker City.

The location puts it close to Sherco Solar, one of the largest solar farms under development in the United States, with a total capacity of 710 megawatts when completed. The battery will be built on a site owned by Xcel Energy, which operates several coal-fired power plants but has converted more than half of its electricity generation to renewable energy.

This demonstration battery is a pilot for a plan in which Xcel will begin using iron-air batteries to replace its coal-fired power plants in a way that leverages existing transmission infrastructure but also reduces the cost of energy release to what the local grid is already paying for fuel. The cost of coal-to-grid electricity is about 10%.

"Multi-day battery storage has the potential to help us better leverage the renewable energy we generate while ensuring the grid remains reliable for our customers," Xcel Senior Vice President Bria Shea said in a press release. "We look forward to bringing this system online at our Sherco sites and learning more about the role it will play in our larger efforts to achieve 100% carbon-free electricity."

Construction will begin next year and the battery is expected to come online in 2025. This won't be Form's first grid-connected project; a smaller 1.5-megawatt system is also planned with Minnesota-based Big River Energy.