Massive Funding for Iron-Air Technology
The long-duration energy storage (LDES) sector is attracting unprecedented capital as the grid demands multi-day storage solutions. In August 2026, Form Energy secured $750 million in Series G financing to scale manufacturing of its 100-hour-duration iron-air battery technology. This architecture targets multi-day grid storage, enabling renewable capacity to provide firm power through prolonged periods of low wind or solar generation. The transition to renewable energy requires storage solutions that can bridge multi-day gaps in generation.
Iron-Based Redox Flow Innovations
Alongside iron-air advancements, ESS Inc. is developing iron-based redox flow battery systems designed specifically for stationary, long-duration energy storage. Unlike lithium-ion batteries, flow batteries decouple energy capacity from power output by storing energy in external electrolyte tanks. This design allows for flexible scaling of discharge duration.
ESS Inc.'s technology utilizes abundant iron chemistry and offers long operational lifetimes, making it highly suitable for utility and industrial applications where cost-effectiveness and safety are paramount.
Market Outlook for Long-Duration Storage
These technological leaps are occurring within a rapidly expanding market. A September 2026 report by DataM Intelligence values the grid-scale battery market at USD 13.61 billion in 2026. It is expected to reach USD 107.29 billion by 2035, growing at a CAGR of 25.74%. The report specifically identifies unlocking long-duration storage via emerging non-lithium technologies capable of longer discharge durations as a key market opportunity. Both Form Energy's iron-air systems and ESS Inc.'s iron flow batteries are positioned to capture significant market share as grid operators seek alternatives to traditional lithium-ion for extended storage needs.
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