General TRL Redox Characteristics

Static Electrolyte System

Redox cells with two electrolytes and all liquid reagents can be designed and operated as either static electrolyte systems, or full flow electrolytes. In the first case the electrolytes remain fixed in their respective compartments.  All the energy is stored within the cell structure. The drawing below shows such a basic design.

 

The static electrolyte offers simplicity in design, and no mechanically moving parts. However, the energy and power densities of any particular cell design are compromised because inter-electrode cell spacing simultaneously affects cell energy capacity and power delivery capability.      Charge retention time is significantly reduced in the static cell configuration because of ionic and molecular diffusion across the membrane separator when the cell is not in use.

Full Flow Electrolyte

In the full flow configuration the two electrolytes are circulated from reservoirs into and out of their respective cell compartments through appropriate manifolds and pumps as shown in the figure below.

 

 

This  configuration of the CIR system is imminently suited for large energy storage applications because of these advantages;

• Indefinitely long charge retention times
• No cell imbalance problems with large cell arrays
• System can be electrically shut off by electrolyte draining
• Separation of energy capacity from power delivery parameters in system designs
• Ability to be recharged chemically by replacing electrolytes
• Electrolytes may be electrically recharged in an external device
• No degradation resulting from unwanted trans-membrane molecular or ionic migration

Since reagents remain in solution at all times, no deposition or removal of solid reagents at electrode surfaces in the energy storing process. There are few choices of chemical components that have all the properties necessary to make it a practical electrochemical process.  Almost all of the materials combinations have the singular drawback of having dissimilar materials on opposite electrolytes. And, since these reagents are in solution there is the inexorable transport of catholyte materials into the anolyte region and vice versa. In most cases there is no direct method of returning these unwanted components from one electrolyte to their origin.

The TRL-CIR system does not degrade in performance because of such unwanted transport problem.

 

Return to home Page Home Page