Prudent Uses Vanadium-based Redox Regenerative Fuel Cell

I got an interesting comment on one of my posts about distributed power generation and storage.

Charles Toca representing Prudent Energy VRB Energy Storage System (VRB-ESS) says they have an energy storage system base on the the vanadium-based redox regenerative fuel cell that converts chemical energy into electrical energy.

This is from their website:

-Editor

How It Works

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

• (positive: V(IV)/V(V) redox couple,
• negative: 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.

The VRB-ESS employs vanadium ions in both half-cell electrolytes. Therefore, cross-contamination of ions through the membrane separator has no permanent effect on the battery capacity, as is the case in redox flow batteries employing different metal species in the positive and negative half-cells. The vanadium half-cell solutions can even be remixed bringing the system back to its original state.

The open circuit cell voltage at a concentration of 2 mole per liter for each vanadium species is 1.6 V when fully charged. The relatively fast kinetics of the vanadium redox couples allows high Coulombic and voltage efficiencies to be achieved without costly catalysts. The same current is passed through all of the cells as they are arranged in series. Such systems have many admirable properties including high efficiency, long cycle life, ease of scalability and negligible environmental impact.

More....

The VRB-ESS can economically store and supply large amounts of electricity on demand and is focused on stationary applications. It is a long life, cost effective, low maintenance, efficient technology that allows for the scalability of power and storage capacity independently.

The VRB-ESS is particularly beneficial to renewable energy providers, utilities and end users through its ability to “inventory” electricity, allowing for the optimal match of supply and demand.

The VRB-ESS is well suited for a variety of applications. Enabling the provision of “firm” capacity from intermittent renewable generation such as wind and solar; more cost effective and efficient generation of electricity in remote areas; capital deferral for utilities; and load levelling (peak shaving) applications. The VRB-ESS is also capable of providing backup power solutions including applications for utility sub-stations and telecommunication sites.

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