Abstract: In the regenerative fuel cell, a positive chamber is separated from a negative chamber by a cation exchange membrane. The positive chamber comprises a positive electrode and a bromine-containing electrolyte. The negative chamber comprises a negative electrode and a sulfide-containing electrolyte. When the cell is in operation, the electrolytes are replenished using electrolyte from an electrolyte store (32, 34). In the method, the distribution of water between the two electrolytes is controlled by discharging the electrolyte(s), such that when the electrolytes are separated by a water permeable membrane (46), water will flow from the sulfide-containing electrolyte to the bromine-containing electrolyte by osmosis. The electrolytes are circulated through a container (43) which is divided by a water permeable membrane (46), under conditions wherein no current flows in the container between the two electrolytes.

Abstract: The present invention relates to a process for operating a regenerative fuel cell (RFC). The process involves circulating a first electrolyte (electrolyte 1) through the negative chamber of the cell and a second electrolyte (electrolyte 2) through the positive chamber of the cell. Electrolyte (1) contains sulfide during the discharge cycle of the cell. Electrolyte (2) contains bromine during the discharge cycle of the cell. Decreases in ph in the electrolyte are compensated by circulating a fraction of other electrolyte (1) or (2) through the positive chamber of an auxiliary cell. A fraction of electrolyte (2), which has been made free of bromine, is circulated in the negative chamber of the auxiliary cell.

Abstract: A process for rebalancing the electrolyte system in a regenerative fuel cell using a sulfide/polysulfide reaction in one half of the cell and a bromine/bromide reaction in the other half of the cell comprises passing the electrolyte containing sulfide/polysulfide or bromine/bromide through the +ve chamber of an auxiliary cell and passing an electrolyte containing water and being free from polysulfide or bromine through the ?ve chamber of the auxiliary cell the auxiliary cell operating so as to oxidize sulfide ions to sulfur or bromide ions to bromine in the +ve chamber and to reduce water to hydrogen and hydroxide ions in the ?ve chamber.

Abstract: In a regenerative fuel cell, a positive chamber is separated from a negative chamber by a cation exchange membrane. The positive chamber comprises a positive electrode and a bromine-containing electrolyte. The negative chamber comprises a negative electrode and a sulfide-containing electrolyte. When the cell is in operation, the electrolytes are replenished using electrolyte from an electrolyte store (32, 34). In the method of the present invention, the distribution of water between the two electrolytes is controlled by discharging the electrolyte(s), such that when the electrolytes are separated by a water permeable membrane (46), water will flow from the sulfide-containing electrolyte to the bromine-containing electrolyte by osmosis. The present invention involves circulating the electrolytes through a container (43) which is divided by a water permeable membrane (46), under conditions wherein no current flows in the container between the two electrolytes.

Abstract: A method suitable for detecting the onset of colloid formation within a solution whose composition is in a state of change, which method makes use of the technique of acoustophoresis and which comprises the step of either (I) applying an oscillating electric field to the solution and monitoring the amplitude of the resultant acoustic signal, the onset of colloid formation being detected by a change in the amplitude of the resultant acoustic signal, or (ii) applying an oscillating acoustic signal to the solution and monitoring the resultant oscillating electric field, the onset of colloid formation being detected by a change in the amplitude of the resultant oscillating electric field, or (iii) applying an oscillating electric field to the solution and monitoring the resultant oscillating electric field, the onset of colloid formation being detected by a change in the amplitude of the resultant oscillating electric field.

Abstract: A method for the removal of sulfate ions from an electrolyte of an electrochemical reduction-oxidation system wherein said electrolyte comprises a halogen and in which the sulfate ions an a contaminant or interferant, which method comprises the steps of: (i) increasing the halide concentration in the electrolyte by electrochemical reduction of the halogen, (ii) crystallizing a sulfate salt out of the electrolyte, and (iii) separation of the electrolyte from the crystallized sulfate salt. An electrochemical process for energy storage and/or power delivery comprising the step of removal of sulfate ions from the electrolyte according to the above cited method is also disclosed.