What Is a Redox Flow Battery?
StorEn Technologies has revolutionized energy storage by engineering sustainable vanadium redox flow batteries. Our batteries represent only one type of redox flow batteries—there is a wide range of additional redox flow batteries, along with a number of hybrid battery systems. If you’re unfamiliar with redox flow batteries, here’s a quick primer.
Understanding Redox Flow Batteries
Redox flow batteries are a type of rechargeable electrochemical energy storage device. “Redox” refers to the chemical reduction and oxidation reactions that redox flow batteries use to store energy in liquid electrolyte solutions. These solutions flow through a battery of electrochemical cells whenever it is charged or discharged.
The electromotive force or voltage generated in the cells of the battery is determined by the difference in chemical potential between the chemical states of the active elements on each side of the battery. The redox flow battery’s voltage is dependent on the chemical species engaged in the reactions, as well as the number of cells connected in series. The amount of atoms or molecules of the active chemical species that are reacted within the cells as a function of time determines the current generated by the battery.
The power generated by a redox flow battery is a product of the total current and voltage created by the electrochemical cells. The amount of active chemical species available in the electrolyte solution determines the amount of energy stored in the redox flow battery.
Types of Redox Flow Batteries
There are a number of types of flow batteries, including hybrid options that combine one battery electrode and one fuel cell electrode in an electrochemical cell. True redox flow batteries include:
Vanadium redox flow batteries
Polysulfide bromide batteries
Uranium redox flow batteries
Zinc-polyiodide flow batteries
Iron-chromium redox flow batteries
Vanadium redox flow batteries are the most commonly used, as they show the most promise for more widespread commercial use and mass production. StorEn vanadium flow batteries are a sustainable alternative to lithium batteries, with full capacity throughout their lifetime, low maintenance, and a life expectancy of up to 25 years.
Uses for Redox Flow Batteries
Redox flow batteries are best for applications requiring power in the tens of kilowatts to tens of megawatts, as well as energy storage in the 500 kilowatt-hours to hundreds of megawatt-hours range. Because storage tanks and flow controls are straightforward and inexpensive to scale, and electrochemical stacks can include repeat units with power ratings in the tens to hundreds of kilowatts, redox flow batteries may be the most practical solution in this range.
Redox flow batteries are a cost-effective and low-risk method of storing electrical energy at the grid scale. Other electrochemical technologies for storing electrical energy offer less flexibility in tailoring power and energy ratings. With power ratings ranging from tens of kW to tens of MW and storage durations ranging from two to 10 hours, redox flow batteries are ideal for residential, commercial, and telecom energy storage applications.