Technology (VRFB)

How it works

Vanadium Redox Flow is an energy storage technology with unique characteristics

How does a Vanadium Redox Flow battery (VRFB) work?

  • A flow battery is charged and discharged by a reversible reduction-oxidation reaction between the two liquid vanadium electrolytes of the battery
  • Unlike conventional batteries, electrolytes are stored in separated storage tanks, not in the power cell of the battery
  • During operation these electrolytes are pumped through a stack of power cells, in which an electrochemical reaction takes place and electricity is produced
    How does a Vanadium Redox Flow battery (VRFB) work? [chart]
  • Other key features of the VRFB are that:
    • Since vanadium can exist in four different states, only a single element used (rather than two or more, as in zinc-bromine batteries)
    • The battery is simple, nontoxic and avoids cross-contamination

Source: Pacific Northwest National Laboratory (


Over the past 5 years, VRFB technology has evolved and improved significantly

Factors leading to better VRFB technology

  • More companies undertaking research in the commercial application of the VRFB. 15 years ago there was only one company active in this field, while today there are more than a dozen and the number is growing
  • More installations and a longer track record of performance
    • Three manufacturers have more than 60 global installations each
    • Larger installations (over 1MWh) have increased
  • More research funding, including from the US Department of Energy for the Pacific Northwest National Laboratory (PNNL)

Improvements in VRFB technology over the past few years

  • Improvement in energy density by 70% (by using hydrochloric acid rather than sulphuric acid in the electrolyte)
  • Improved cell stack / membrane technology that eliminates the issue of cross-contamination
  • Commercial development of larger systems of 200-250kW size, which have lower costs per kW
  • Overall lower prices, decreasing from over $2,000 to around $500 per kWh for larger systems. Price points of around $300/kWh are likely in 12-24 months.
  • Improved overall quality, with some manufacturers offering free 5 year warranties and others offering 20 year maintenance plans

Modern Vanadium Redox Flow batteries are modular "plug and play" containerised utility scale storage solutions

Key components of VRFB system
  1. Cell stacks / membrane

  2. Electrolyte tanks

  3. Pumps and other balance of plant equipment (such as pipes and hoses)

  4. Power conversion system (including control system, communications, inverter, electrical wiring, etc.)

  5. External electrical connection

  6. Standard size shipping container


Vanadium contributes ~30% to the overall cost of the VRFB system

VRFB cost breakdown

VRFB cost breakdown [graph]
  • The larger the VRFB system (both in watts and hours), the larger the relative contribution of Vanadium
  • Vanadium will be the one cost component immune to economies of scale

Source: EPRI – Vanadium Redox Flow Batteries (1014836)