Regenerative fuel cell with pH control
AssigneeRegenesys Technologies Limited
InventorsPatrick John Morrissey, Norman John Ward
Life of this patent
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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.
Claims5
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 (−ve) chamber containing a −ve electrode, the chambers being separated from one another by a cation exchange membrane, the electrolyte circulating in the −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 −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 −ve chamber containing a −ve electrode, the chambers being separated from one another by a cation exchange membrane, the electrolyte circulating through the −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 −ve chamber and (b) transferring at least a portion of electrolyte 2 which exits the −ve chamber of the auxiliary cell into electrolyte 1.
Apparatus for carrying out a process as claimed in any one of the preceding claims comprising:
- (i) a single cell or an array of repeating cell structures, each cell comprising;
- a +ve chamber containing a +ve electrode and a −ve chamber containing a −ve electrode the chambers being separated from one another by an ion exchange membrane, an electrolyte circulating in the −ve chamber of each cell which contains sulfide during discharge (electrolyte 1), and an electrolyte circulating in the +ve chamber which contains bromine during discharge (electrolyte 2),
- (ii) storage and circulation means for each electrolyte for restoring or replenishing the electrolytes in the +ve and −ve chambers,
- (iii) means for compensating for pH decreases in the electrolytes comprising;
- (a) an auxiliary cell which comprises a +ve chamber containing a +ve electrode and a −ve chamber containing an −ve electrode the chambers being separated from one another by a cation exchange membrane, means for circulating a fraction of electrolyte 1 or 2 through the +ve chamber of the auxiliary cell, means for circulating a fraction of electrolyte 2 which has been made free of bromine by electrochemical redution thereof through the −ve chamber of the auxiliary cell and (b) means for transferring at least a portion of electrolyte 2 which exits the −ve chamber of the auxiliary cell into electrolyte 1.
Dependencies are inferred from the claim text.