An ESS iron flow battery pack. ESS

Batteries are needed to store clean power from wind and solar, but the high cost of lithium batteries has slowed their widespread adoption. Companies have long sought to produce alternatives made of cheaper materials, like zinc, and Oregon-based ESS Inc. says it has now developed a more affordable and better-performing battery made with iron, Bloomberg reported. 36v Lifepo4 Battery

CSB Energy Corp., a clean-energy firm, is planning to install these batteries at solar projects across the U.S., where they will store surplus power generated during the day and distribute it at night. The company will deploy enough batteries to power 50,000 American homes for a day.

“Unlike lithium-ion batteries, iron flow batteries are really cheap to manufacture,” Rich Hossfeld, CEO of SB Energy, told Bloomberg. “The battery is made of iron salt and water.”

While lithium-ion batteries have gotten dramatically cheaper over the last decade, with prices dropping around 90 percent, their dependence on expensive materials like nickel and cobalt means there is a limit to how far costs can fall. Whereas lithium-ion batteries used for power storage can cost up to $350 per kilowatt-hour, ESS’s iron-based battery could be purchased for as little $200 per kilowatt-hour or less by 2025 and store energy for longer, Bloomberg reported.

Since iron-flow batteries do not work like the lithium-ion batteries used in smartphones or EVs, they have limited applications. Because the electrolytes stored within need to be moved with a physical pump, iron-flow batteries are much larger than lithium-ion batteries — ESS batteries are sold inside shipping containers. But they are still a practical option for grid storage.

12 Volt Lifepo4 Battery “Long-duration energy storage, like this iron-flow battery, [is] key to adding more renewables to the grid,” Venkat Viswanathan, a battery expert and associate professor of mechanical engineering at Carnegie Mellon University, told Bloomberg.