An electrochemical fuel cell having an anode, an ion transfer membrane and a cathode has liquid water delivered to the fluid flow channels within the cathode so as to maintain a relative humidity of 100% throughout the fluid flow channels. A calibration method and apparatus is described for determin
An electrochemical fuel cell having an anode, an ion transfer membrane and a cathode has liquid water delivered to the fluid flow channels within the cathode so as to maintain a relative humidity of 100% throughout the fluid flow channels. A calibration method and apparatus is described for determining an optimum quantity or range of quantities of liquid water to be delivered to the cathode fluid flow channels under varying operating conditions. An operating method and apparatus is described that ensures an optimum quantity of liquid water is delivered to the cathode fluid flow channels under varying operating conditions.
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1. An electrochemical fuel cell assembly comprising: an electrochemical fuel cell stack comprising a plurality of fuel cells, each of the fuel cells comprising: an anode having one or more anode fluid flow channels therein;an ion transfer membrane; anda cathode having one or more fluid flow channels
1. An electrochemical fuel cell assembly comprising: an electrochemical fuel cell stack comprising a plurality of fuel cells, each of the fuel cells comprising: an anode having one or more anode fluid flow channels therein;an ion transfer membrane; anda cathode having one or more fluid flow channels therein;a mechanism configured to deliver fluid fuel to one or more fluid flow channels in each anode of one or more fuel cells in the electrochemical fuel cell stack;a mechanism configured to deliver fluid oxidant to one or more fluid flow channels in each cathode of the one or more fuel cells;a mechanism to exhaust reaction by-products and unused oxidant from the one or more fluid flow channels in each cathode of the one or more fuel cells; anda water injection mechanism controllable to deliver a sufficient quantity of liquid water to the one or more fluid flow channels in each cathode of the one or more fuel cells such that a relative humidity of 100% is maintained throughout the one or more fluid flow channels in each cathode of the one or more fuel cells;a controller configured to control delivery of the sufficient quantity of liquid water, the controller being configured (i) to determine, for each of a plurality of currents, a maximum voltage for the one or more fuel cells as a function of liquid water flow rate, the each of a plurality of currents being within a range of operating conditions of the one or more fuel cells, (ii) to determine a calibration function expressing a minimum liquid water flow rate as a function of current and/or air stoichiometry, the calibration function being determined by variation of water flow rate to each cathode operating at constant current and constant air stoichiometry to determine minimum and maximum water flow rates repeated for a plurality of stack currents or air stoichiometries, and (iii) to control delivery of at least the minimum liquid water flow rate for a corresponding current drawn from the one or more fuel cells and/or for the air stoichiometry, the delivered minimum liquid water flow rate being determined by the calibration function. 2. The assembly of claim 1, wherein the water injection mechanism comprises a pump. 3. The assembly of claim 1, wherein the controller comprises a voltage sensor for sensing a fuel cell voltage. 4. The assembly of claim 3, wherein the controller is configured to operate in a calibration mode comprising determining, for each of the plurality of currents, the maximum voltage for the one or more fuel cells as a function of liquid water flow rate. 5. The assembly of claim 4, wherein the calibration mode further comprises determining the calibration function expressing the minimum liquid water flow rate as a function of current and/or air stoichiometry. 6. The assembly of claim 1, further comprising: a current sensor for sensing current flow through the one or more fuel cells in the electrochemical fuel cell stack;wherein the controller is configured to control a water injection rate to maintain delivery of a water factor greater than 1.0 for all currents within an operating range of the one or more fuel cells. 7. The assembly of claim 6, wherein the controller is configured to control the water injection rate to maintain delivery of a water factor of at least 1.5. 8. The assembly of claim 6, wherein the controller is configured to control the water injection rate to maintain delivery of a water factor of less than 40. 9. The assembly of claim 6, wherein the controller is configured to control the water injection rate to maintain delivery of a water factor of at least 3. 10. The assembly of claim 1, wherein the controller is configured to control the water injection rate to maintain of delivery of a water factor in a range from 3 to 6. 11. The assembly of claim 1, further comprising: a mechanism configured to temporarily permit delivery of a quantity of liquid water to the fluid flow channels within a cathode such that a relative humidity of less than 100% is maintained when a cathode exhaust temperature is below a predetermined threshold corresponding to a sub-optimal operating temperature. 12. The electrochemical fuel cell assembly of claim 1, wherein the one or more fuel cells comprises less than all fuel cells in the electrochemical fuel cell stack. 13. The electrochemical fuel cell assembly of claim 1, wherein the one or more fuel cells comprises all fuel cells in the electrochemical fuel cell stack. 14. The electrochemical fuel cell assembly of claim 1, wherein the calibration function is determined for air stoichiometry in a range 1.1 to 10. 15. The electrochemical fuel cell assembly of claim 1, wherein the calibration function is determined for air stoichiometry in a range 1.4 to 4.0. 16. The electrochemical fuel cell assembly of claim 1, wherein the water injection mechanism is controllable to deliver the sufficient quantity of liquid water upon start-up of a fuel cell. 17. The electrochemical fuel cell assembly of claim 1, wherein a fuel cell among the one or more fuel cells is operable such that, for any measured fuel cell power delivery, a liquid water injection rate into a cathode of the fuel cell and/or a gas flow through the cathode are controllable to ensure that there is more liquid water in all regions of a surface of the cathode than can be evaporated in prevailing temperature and pressure conditions. 18. The electrochemical fuel cell assembly of claim 17, wherein a plurality of fuel cells in the electrochemical fuel cell stack have a common oxidant supply manifold and a common water injection manifold such that, for any measured stack power delivery, a liquid water injection rate into the common water injection manifold and/or a gas flow rate in the common oxidant supply manifold are controllable to ensure that there is more liquid water in all regions of cathode surfaces of all of the plurality of fuel cells than can be evaporated in prevailing temperature and pressure conditions.
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이 특허에 인용된 특허 (5)
Breault Richard D. ; Condit David A. ; Grasso Albert P. ; Gorman Michael E., Direct antifreeze cooled fuel cell.
Matcham, Jeremy Stephen; Grange, Nathan; Benson, Paul Alan; Baird, Scott; Kells, Ashley; Cole, Jonathan; Adcock, Paul L.; Hood, Peter David; Foster, Simon Edward, Water management in fuel cells.
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