ESS Tech Inc is a long-duration energy storage company specializing in iron flow battery technology. It develops and manufactures long-duration energy storage systems based on iron flow battery technology. The company's batteries use earth-abundant materials, including iron, salt, and water, and are designed for high cycle life and recyclability. It operates as a single business operating segment, which includes all activities related to the design, engineering, and manufacturing of the company's long duration energy storage products. The company's revenue is derived from the sale of its energy storage products and from service contracts.