Flow battery | Sustainability Language

Definition

A flow battery is an electrochemical storage device in which energy is stored in dissolved electroactive species in liquid electrolytes, pumped from external tanks through a cell stack where charging and discharging occur. Because the tanks (energy capacity) and the stack (power rating) are sized independently, flow batteries scale to long-duration storage by simply enlarging tanks. The most mature chemistry is the vanadium redox flow battery (VRFB), which uses vanadium ions in different oxidation states (V2+/V3+ and V4+/V5+) in both half-cells, eliminating cross-contamination; zinc–bromine is a prominent hybrid design. Flow batteries offer long cycle life and low degradation, at the cost of lower energy density than lithium-ion.

References

ScienceDirect

separation of energy storage and power conversion, VRFB as most mature chemistry with V2+/V3+ and V4+/V5+ couples, zinc–bromine hybrid

Sumitomo Electric

liquid-electrolyte tank design, scalability, long-duration storage application

Overview

What it means

The energy/power decoupling makes flow batteries a candidate technology for multi-hour to multi-day grid storage — exactly the duration gap that lithium-ion struggles to serve economically — supporting high shares of variable renewables.

How it is used

Deployed in grid-scale storage projects, microgrids and renewable-integration pilots; commercial VRFB systems operate at utility scale in several countries.

Why it matters

Long-duration storage is the missing piece for deeply decarbonised grids; flow batteries are one of the few demonstrated technologies that scale storage duration cheaply.

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Definition

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A flow battery is an electrochemical storage device in which energy is stored in dissolved electroactive species in liquid electrolytes, pumped from external tanks through a cell stack where charging and discharging occur. Because the tanks (energy capacity) and the stack (power rating) are sized independently, flow batteries scale to long-duration storage by simply enlarging tanks. The most mature chemistry is the vanadium redox flow battery (VRFB), which uses vanadium ions in different oxidation states (V2+/V3+ and V4+/V5+) in both half-cells, eliminating cross-contamination; zinc–bromine is a prominent hybrid design. Flow batteries offer long cycle life and low degradation, at the cost of lower energy density than lithium-ion.

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