A reliable and cost effective long duration energy storage solution is poised to play a pivotal role not only in the future developments of renewable energy industry but also in the necessary modernization of outdated electrical grid system.
Vanadium is the only one metal known as a naturally complete battery. Emerging vanadium based energy storage solution technology should not be ignored. After enormous research and developments since the1980s, the Vanadium Redox Flow Battery (VRFB) is becoming mature for commercial applications.
VRFB is a type of rechargeable flow battery that employs vanadium ions in different oxidation states to store chemical potential energy.
As shown in the Figure, the energy conversion from electricity energy to chemical potential energy (charge) and vice versa (discharge) occurs instantly as the liquid electrolytes flowing through the stacks built of Ion Exchange Membranes.
The VRFB structure separates design of energy (kwh) and power (kw), and the power/energy ratio can be designed and adjusted per the applications. Both overheat issues and thermal run-away problems are avoided by such structure.
The following favorable general features of VRFB have attracted wide interests for utility scale stationary applications.
Demonstrates excellent electrochemical reversibility and virtually unlimited life cycle.
Can offer almost unlimited energy capacity simply by using larger electrolyte storage tanks.
The electrolytes are aqueous and inherently safe and non-flammable. Even when the electrolytes are accidentally mixed, the battery suffers no permanent damage. VRFB can be recharged by replacing the electrolytes when charging power source is not available.
The limited self-discharge characteristics of VRFB are useful in applications where the batteries must be stored for long periods of time with little maintenance. VRFB can be left completely discharged for long periods with no ill effects.
The extremely rapid response time offered by VRFB makes it as a good choice for microgrid with “all-in one” solution for reliability, frequency regulation and load shifting.
The main disadvantages with vanadium redox technology are a relatively low energy-to-volume ratio, and the heaviness of the battery due to aqueous electrolyte therefore limit applications.