Patent ID: 6887600

Claim:
An electrochemical process for energy storage and/or power delivery comprising: (i) maintaining and circulating electrolyte flows in a liquid system in which the active constituents are soluble in a single cell or in an array of repeating cell structures, each cell with a positive (+ ve ) chamber containing a + ve electrode and a negative (âˆ’ ve ) chamber containing a âˆ’ ve electrode, the chambers being separated from one another by a cation exchange membrane, the electrolyte circulating in the âˆ’ ve chamber of each cell during discharge containing sulfide (electrolyte 1 ), and the electrolyte circulating in the + ve chamber during discharge containing bromine (electrolyte 2 ), (ii) restoring or replenishing the electrolytes in the + ve and âˆ’ ve chambers by circulating the electrolyte from each chamber to storage means comprising a volume of electrolyte greater than the cell volume for extended delivery of power over a longer discharge cycle than the cell volume alone would permit, and (iii) compensating for pH decreases in the electrolytes by (a) circulating a fraction of electrolyte 1 or 2 through the + ve chamber of an auxiliary cell, said auxiliary cell comprising a + ve chamber containing a + ve electrode and a âˆ’ ve chamber containing a âˆ’ ve electrode, the chambers being separated from one another by a cation exchange membrane, the electrolyte circulating through the âˆ’ ve chamber of the auxiliary cell being a friction of electrolyte 2 which has been made free of bromine by electrochemical reduction thereof, the auxiliary cell operating so as to oxidise sulfide ions to sulfur (where a fraction of electrolyte 1 is circulated through the + ve chamber) or bromide ions to bromine (where a fraction of electrolyte 2 is circulated through the + ve chamber) in the + ve chamber and so as to reduce water present in electrolyte 2 to hydrogen and hydroxide ions in the âˆ’ ve chamber and (b) transferring at least a portion of electrolyte 2 which exits the âˆ’ ve chamber of the auxiliary cell into electrolyte 1 .