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.

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

Conventional battery chemistries, with limited cycle life, deliver a 7- to 10-year lifecycle before requiring augmentation. ESS iron flow chemistry delivers 25 years or more with no capacity fade or degradation.

Cleaner and more sustainable

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.

Lowest cost per kWh: For applications that use up to 12 hours of discharge and frequent cycling, the ESS systems deliver the lowest cost per KWh over a 25-year operating design life.

6 to 12 hour capital cost and cycle capacity diagram

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

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

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 electrochemistry, allows ESS systems to operate longer, at deeper discharge levels. Unlike typical batteries packaged as fixed cells or modules, a flow battery has more energy storage capacity, which gives the user the flexibility to align both the power output and energy storage capacity precisely to a project’s requirements.

Safer by design

ESS iron flow batteries are safe and sustainable, reducing the need for fire suppression equipment, secondary containment, or hazmat precautions. Iron flow chemistry has a pH similar to soda or wine and contains iron, salt, and water. In addition, the battery system is substantially recyclable at end-of-life.

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Designed to meet customer needs

Scalable: ESS power modules’ streamlined architecture allows them to power our turnkey Energy Warehouse product line and still be scalable enough to support Energy Center deployments delivering MWh or GWh of storage. An enhanced power module architecture also allows double the plating capacity of prior generations, extending the module-level discharge duration to up to 12 hours. In addition, the entire ESS battery assembly is designed to facilitate robotic manufacturing for precision quality.

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

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.

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. 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.