ESS Tech, a manufacturer of iron flow long-duration energy storage (LDES) systems for commercial- and utility-scale applications, has closed $31 million in insider-led funding measures. This funding enables the company to build its technical momentum for its LDES product, Energy Base, which has a 12.2-hour duration at rated power and 17.8 hours at reduced power. The product is focused on being produced completely in the U.S.