As it expands a just completed long-duration battery storage system factory in West Virginia to more than 850,000 sq ft of production space by the end of 2025 and boosts annual manufacturing capacity to 500 MW at minimum—along with getting several proposed U.S. commercial scale installations under way—startup Form Energy has gained $405 million in new funding from some high-profile backers.

The Massachusetts-based firm's iron-air technology is for limited, but large-scale application in enabling continuous clean-energy discharge to the grid for 100 hours at one-tenth the cost of lithium-ion batteries, it said. Form Energy’s system intakes oxygen to convert iron to rust, then changes rust back into iron in exhaling the oxygen—discharging and charging the battery in the process.