To make the most of renewable energy sources, such as wind and solar, utilities must overcome the problem of intermittency. When the sun isn’t shining or the wind isn’t blowing, energy is not being generated. Moreover, the energy grid was designed to accept the constant, predictable output of fuel-burning power plants—not the sharp rise and fall produced by solar panels at dawn and dusk.

To solve this problem, utilities need low-cost, large-scale, long-duration energy storage systems that bank energy when it’s being generated and provide energy when it’s needed. Now, energy start-up ESS Inc. of Wilsonville, OR, has developed a new technology that promises to meet that need. The company’s iron-flow battery systems—the Energy Warehouse and the Energy Center—are designed to meet the energy needs of customers ranging from small industrial facilities to large, utility-scale projects.