sThe adjacent video is an introduction to the basics of Vandium Redox Flow Batteries (VRFB). In general, flow batteries can be quite useful for processes like peak shaving and load leveling. By having flow batteries in a microgrid with a renewable energy source, such as a photovoltaic, you can store the excess energy generated during the day and utilize it when the renewable source is not active, like during cloud cover or at night.
For most flow batteries, including vanadium redox flow batteries, the setup consists of two electrodes separated by an ion separation membrane. Between these electrodes, we have an electrolyte. There is a positive half-cell and a negative half-cell. Depending on whether you’re in the charge or discharge cycle, electrons will flow into or out of these cells.
We have two fluidic loops: a pump and a positive electrolyte tank, as well as another pump with a negative electrolyte tank. When we have a power source, such as a photovoltaic or wind turbine, we’re essentially charging the battery. Later, when we’re running lights or refrigeration at night, we consider it a load, and that’s when we discharge the flow battery.
The flow battery works by pumping Vanadium in different oxidation states into the half-cells. In the case of a Vanadium redox flow battery during the discharge cycle, we pump Vanadium (V2+) into the negative half-cell. Here, Vanadium donates electrons to the electrode, which then travel around an external circuit. Simultaneously, in the positive half-cell, Vanadium (V5+) is reduced to Vanadium (V4+). During this process, there’s also a diffusion of protons across the ion selective membrane.
In the charge cycle, the process happens in reverse. For instance, during the daytime, when the battery is being charged, Vanadium (V4+) donates electrons that travel around the external circuit and pass to the Vanadium (V3+) in the half-cell. At the same time, Vanadium (V2+), which is being pumped from its reservoir, becomes Vanadium (V3+). Additionally, the proton (or hydrogen ion) travels in the opposite direction compared to the previous slide, moving back across the ion membrane. Vanadium (V4+), after donating an electron, becomes Vanadium (V5+)
To summarize, a vanadium redox flow battery consists of two half-cells with electrodes bordering them, and an ion selective membrane between the half-cells through which protons shuttle. Vanadium is recycled in different redox states between the two half-cells.