ESS Iron Flow Chemistry

Powerful technology transforming the utility grid

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A flow battery is an electrochemical cell where two chemical solutions are separated by a membrane. Ions are exchanged across this membrane, producing chemical energy and electricity.

For most people, iron flow chemistry probably isn’t the first type of battery system that comes to mind. If you really care about clean, reliable, and cost effective long-duration energy storage, it should be.

ESS iron flow battery solutions are mature, second-generation systems that offer unmatched cost and sustainability with performance so dependable, it’s guaranteed through an independent insurer: Munich Re.

Conventional battery chemistries, with limited cycle life, can hope for a 7- to 10-year lifecycle before needing augmentation. ESS iron flow chemistry lasts 20 years or more with no capacity fade or degradation.

Cleaner and more sustainable: Thanks to food-grade, earth-abundant iron, salt, and water for the electrolyte, ESS batteries are the easiest to site and safest to operate systems on the market. Because iron flow chemistry doesn’t use rare-earth minerals like vanadium and lithium, it produces less environmental harm in materials sourcing and production processes. That’s part of the reason it’s a more affordable choice.

6 to 12-hour cycle cost chart

Lowest cost per kWh: For applications that can use 6+ hours of discharge and frequent cycling, the Energy Center™ delivers the lowest cost per KWh over its 25-year lifetime.

The superiority of iron flow chemistry: Lower levelized cost of storage (LCOS)

Industry-leading lcos graph

Zero degradation over 20,000 cycles: Iron flow batteries circulate liquid electrolytes to charge and discharge electrons via a process called a redox reaction. The word “redox” is a contraction of the words “reduction,” which represents a gain of electrons, and “oxidation,” or a loss of electrons. ESS uses the same electrolyte on both the negative and positive sides of the equation, eliminating cross-contamination and degradation. This is why ESS chemistry remains stable for an unlimited number of deep-cycle charge and discharge cycles.

Our patented electrode design and control system, coupled with our simple, yet elegant electrochemistry, allows you to operate longer, at higher efficiency and deeper discharge levels. Unlike typical batteries packaged as fixed cells or modules, a flow battery has significantly more energy storage capacity, which gives the user the flexibility to align both the power and amount of electricity stored precisely to a project’s requirements today and for the future.

Safer by design

ESS iron flow batteries are safe and non-toxic, eliminating the need for fire suppression equipment, secondary containment, or hazmat restrictions. Its chemistry has a pH similar to soda and wine and contains no toxic materials. In addition, the battery system is substantially recyclable at end-of-life.

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Next generation = next level improvements

Designed for durability: With the ESS generation 2.0 platform, you get a system designed to eliminate potential points of failure. There are no O-rings with our adhesively bonded and sealed stack architecture, resulting in a life-long seal. We’ve increased power density and reduced plumbing connections by more than 60%. We’ve also engineered the batteries with a self-supporting structure, eliminating the need for expensive and space-consuming racking. All of these enhancements further reduce potential points of failure and increase durability.

Scalable: We have invested in the expansion and automation of our plant to support 2 GWh of battery module production for our Energy Warehouse™ and Energy Center™ solutions. The Gen2’s streamlined architecture allows ESS power modules to be compact and modular enough for our 50 kW Energy Warehouse and still be scalable enough to support a multiple MW Energy Center deployment. An enhanced power module architecture also allows double the plating capacity, extending the module-level discharge duration to up to 16 hours. In addition, the entire ESS battery assembly is designed to facilitate robotic manufacturing for precision quality and faster delivery of your order.

Easy operation and maintenance: Each Gen2 cell stack is individually controlled and power conditioned through independent DC-DC converters and stack level monitoring. Stacks can be run at their ideal operating point and be monitored for battery health and optimal performance. Any faults can be detected early and easily isolated from the rest of the system, allowing for enhanced uptime and system safety.

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Enhanced electrolyte health management: The improved Gen 2 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. The system also works in conjunction with the closed-loop plumbing system to prevent electrolyte evaporative losses and to allow the system to run at near-atmospheric pressures. This improves safety, increases scalability, and eliminates the need for electrolyte augmentation during the life of the product.

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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.