Handbook of Energy Storage for Transmission or ... - W2agz.com

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1. Description
1.1. Introduction
The Vanadium Redox Battery (VRB) is a flowing-electrolyte battery (or “flow battery”)
that lends itself to high capacity, high cycle count requirements necessary for utility-scale
T&D electricity storage applications. As its name implies, the VRB is based upon
chemical reactions employing the mineral vanadium, a commercially produced metal.
Unlike conventional batteries, the VRB stores its chemical energy in external electrolyte
tanks that are sized according to the needs of the user. As necessary, aqueous liquid
electrolyte is pumped from storage tanks into a set of reaction stacks where chemical
energy is converted to electrical energy (discharge) or electrical energy is converted to
chemical energy (charge). The electrolyte reactants can be thought of as a “fuel”, so the
VRB is sometimes referred to as a fuel cell or a reversible fuel cell (as are other flow
batteries).
Figure 1 shows the stacks and tanks of a 250 kW / 520 kWh installation in Cape Town,
South Africa.
Figure 1
Typical VRB stacks and tanks (Courtesy Vantech)
The VRB promises the following advantages over other storage technologies:
• Power/Energy Design Flexibility. Since electrolyte is stored separately from
the reaction stacks, the energy storage rating (kWh) is independent of the
power rating (kW). This allows for design optimization for power and energy
separately, specific to each application.
• Long Service Life. Many of the failure modes associated with other batteries
are avoided in the simple, elegant VRB electrochemistry. There are no
Vanadium Redox Battery 6