Vrb Energy

The VRB Energy Storage System (VRB-ESS) is an electrical energy storage system based on the patented vanadium-based redox regenerative fuel cell that converts chemical energy into electrical energy. Energy is stored chemically in different ionic forms of vanadium in a dilute sulphuric acid electrolyte. The electrolyte is pumped from separate plastic storage tanks into flow cells across a proton exchange membrane (PEM) where one form of electrolyte is electrochemically oxidized and the other is electrochemically reduced. This creates a current that is collected by electrodes and made available to an external circuit. The reaction is reversible allowing the battery to be charged, discharged and recharged.

The principle of the VRB is shown in more detail in Figure 1 - it consists of two electrolyte tanks, containing active vanadium species in different oxidation states (catholyte: V(IV)/V(V) redox couple, anolyte: V(II)/(III) redox couple). These energy-bearing liquids are circulated through the cell stack by pumps. The stack consists of many cells, each of which contains two half-cells that are separated by a membrane. In the half-cells the electrochemical reactions take place on inert carbon felt polymer composite electrodes from which current may be used to charge or discharge the battery.

Concept of a Redox Flow Battery System

The VRB-ESS employs vanadium ions in both half-cell electrolytes. Therefore, cross-contamination of ions through the membrane separator has no detrimental influence on the battery capacity, as is the case in redox flow batteries employing different metal species in the positive and negative half-cells. The