Iron Flow Chemistry

The foundation for a decarbonized grid

ESS iron flow batteries being installed at a utility site
Unlimited cycling icon

Unlimited
cycle life

12 hour duration icon

Up to 12 hours
of energy storage

Low carbon footprint icon

Safe and Sustainable

Long life icon

25-year
design life

Our iron flow batteries work by circulating liquid electrolytes — made of iron, salt, and water — to charge and discharge electrons, providing up to 12 hours of storage capacity.

ESS Tech, Inc. (ESS) has developed, tested, validated, and commercialized iron flow technology since 2011.

While conventional battery chemistries deliver a 7- to 10-year lifecycle before requiring augmentation, ESS’ iron flow chemistry delivers 25+ years and unlimited cycling with no capacity fade or degradation.

Safe and sustainable to source, build, and operate

ESS batteries are easy to site and safe to operate. Iron flow chemistry doesn’t use critical minerals such as vanadium, lithium, or cobalt, reducing the environmental impacts associated with the supply chain and reducing their lifecycle greenhouse gas footprint. Incorporating easy-to-source iron, salt, and water, ESS iron flow batteries stand out as the safe and sustainable LDES solution.  Our technology is engineered for flexibility and scale to meet demand peaks and intermittency periods with no degradation or capacity fade, enabling energy security and resilience. It is purpose-built to solve long-duration energy storage.

Safe to deploy in urban areas image
City icon

Can be deployed anywhere from densely populated neighborhoods to regions prone to wildfires.

Non-flammable icon
Non-flammable electrolyte, no risk of thermal runaway.
Easy to source materials icon
Made with easy-to-source iron, salt, and water.
Secure supply chain icon
Secure supply chain of domestically available materials minimizing supply chain risk and climate impact.
Low carbon footprint icon
Lowest lifecycle carbon footprint among competing storage technologies.
Recycle icon
Substantially recyclable or reusable at end-of-life.

Clean technology through full life cycle

ESS iron flow batteries reduce the need for fire suppression equipment, secondary containment, or hazmat precautions. ESS systems are substantially recyclable or reusable at end-of-life.

In collaboration with UC Irvine, a Lifecycle Analysis (LCA) was performed on the ESS Energy Warehouse™ iron flow battery (IFB) system and compared to vanadium redox flow batteries (VRFB), zinc bromine flow batteries (ZBFB) and lithium-ion technologies. Researchers assessed the manufacturing, use, and end-of-life phases of the battery lifecycle. Their findings were clear:

Iron flow batteries proved to be the cleanest technology with the lowest global warming potential (GWP).

Life cycle analysis white paper image

For detailed information, download our LCA comparison of iron-flow batteries to lithium-ion and other types of flow batteries.

Storage flexibility that maximizes value

Diagram showing why the ESS iron flow battery is the world's most sustainable battery

A competitive total cost of ownership over a 25-year design life ensures that our customers will reap the benefits of our long-lasting and reliable energy storage solutions. By strategically driving down costs with our innovative technology, we are on track to meet the DOE’s ambitious LDES cost target of $0.05/kWh by 2030. Implementing fully automated production enhances manufacturing efficiency and consistency and propels ESS towards achieving economies of scale in production. Furthermore, our utilization of standard, widely available components not only streamlines production processes but also significantly reduces costs.

Flexible and cost-effective
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Unlimited cycling without degradation or capacity fade

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Allows for maximized value with revenue stacking

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Operates at wide range of temperatures

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Scalable for a wide range of energy needs

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Competitive total cost of ownership over 25-year design life

Designed to meet customer needs

Enhanced electrolyte health management

The ESS electrolyte health management system cleans and rebalances the electrolyte in real-time, eliminating the need for frequent downtime for recovery or rebalancing required with other flow battery systems.

Iron flow electrolyte image

The ESS iron flow battery uses the same electrolyte on both positive and negative sides. And the proton pump maintains the state of charge and battery health.

Meeting the energy needs of today and tomorrow

Join Eric Dresselhuys, CEO and Vince Canino, COO of ESS Inc. as they take you on a tour of the ESS factory in Wilsonville, Oregon.

While competing non-lithium technologies are still in the lab, our second-generation LDES technology is validated and being deployed worldwide. Iron flow technology is engineered for flexibility and scale; so we can continue to develop solutions that meet future energy storage demand.