CONTROL SYSTEM FOR A SEALED COOLANT FLOW FIELD FUEL CELL POWER PLANT HAVING A WATER RESERVOIR

• US 20140162152A1
• Filed: 08/11/2011
• Published: 06/12/2014
• Est. Priority Date: 08/11/2011
• Status: Active Grant

• Current Assignee: Audi AG (Volkswagen AG)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Darling, Robert M.
• Granted Patent: US 9,147,898 B2
• Time in Patent Office: Days
• US Class Current: 429/414
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 8/04126 Humidifying
• CPC Class Codes: H01M 8/04156 with product water removal
• CPC Class Codes: H01M 8/04171 using adsorbents, wicks or hydrophilic material
• CPC Class Codes: H01M 8/04492 Humidity; Ambient humidity; Water content
• CPC Class Codes: H01M 8/04522 of cathode exhausts
• CPC Class Codes: H01M 8/04619 of fuel cell stacks
• CPC Class Codes: H01M 8/04723 of the coolant
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/04828 Humidity; Water content
• CPC Class Codes: H01M 8/04835 of fuel cell reactants
• CPC Class Codes: H01M 8/04843 of fuel cell exhausts
• CPC Class Codes: H01M 8/0485 of the electrolyte
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

The system (10) controls at least one of a pressure of the reactant streams (16A, 16B) within at least one of an anode flow field (28) and a cathode flow field (36), a flow rate of the reactant streams (16A, 16B) flowing through the anode and/or cathode flow fields (26, 28), a temperature of a coolant fluid passing through a sealed coolant flow field (44), and a flow rate of the coolant fluid; so that water (14) moves from a water reservoir (18A, 18B) into the reactant stream (16A, 16B) whenever power generated by the fuel cell (20) is between about 80% and about 100% of a maximum fuel cell power output, and so that water (14) moves from the reactant stream (16A, 16B) into the water reservoir (18A, 18B) whenever fuel cell power is less than about 75% of the maximum power output.

Claims

1. A control system (10) for a fuel cell power plant (12) for generating electrical current from an oxidant reactant stream (16A) and a hydrogen-rich fuel reactant stream (16B), the system (10) comprising:

a. at least one fuel cell (20) including a membrane electrode assembly (22) having a proton exchange membrane (23) disposed between an anode catalyst surface (24) and an opposed cathode catalyst surface (26) of the assembly (22), an anode flow field (28) defined in fluid communication with the anode catalyst surface (24) and with a fuel inlet line (30) for directing flow of the hydrogen-rich fuel reactant stream (16B) from the fuel inlet line (30) adjacent the anode catalyst surface (24) and out of the anode flow field (28) through an anode exhaust (34) as an anode exhaust stream, a cathode flow field (36) defined in fluid communication with the cathode catalyst surface (26) and with a source (38) of the oxidant for directing flow of the oxidant reactant stream (16A) from an oxidant inlet line (40) adjacent the cathode catalyst surface (26) and out of the cathode flow field (36) through a cathode exhaust (42) as a cathode exhaust stream;

b. a sealed coolant flow field (44) secured in thermal exchange relationship with one of the anode flow field (28) and the cathode flow field (36) for directing a coolant fluid from a coolant inlet (46) of a coolant loop (48), through the coolant flow field (44) and through a coolant loop outlet (50), the coolant loop configured for controlling a temperature of the coolant fluid within the coolant flow field (44);

c. at least one water reservoir (18A, 18B) secured in fluid communication with at least one of the anode flow field (28) and the cathode flow field (36) and secured in fluid isolation from the sealed coolant flow field (44), the water reservoir (18A, 18B) configured for moving water from the reservoir (18A, 18B) and into the reactant stream (16A, 16B) located in the at least one anode and cathode flow fields (28, 36), and for moving water (14) from the reactant stream (16A, 16B) located in the at least one anode and cathode flow fields (28, 36) and into the at least one reservoir (18A, 18B); and

,

d. a relative-humidity controller (62) secured in communication with the fuel cell (12) for selectively controlling at least one of a pressure of the reactant streams (16A, 16B), a flow rate of the reactant streams (16A, 16B), a temperature of the coolant fluid within the sealed coolant flow field (44), so that water (14) moves from the water reservoir (18A, 18B) into the reactant gas streams (16A, 16B) whenever power generated by the fuel cell (20) is between about eighty percent and about one-hundred percent of a predetermined maximum power output of the fuel cell (20), and so that water (14) moves from the reactant gas streams (16A, 16B) into the water reservoir (18A, 18B) whenever power produced by the fuel cell (20) is less than about seventy-five percent of the predetermined maximum power output of the fuel cell (20).

2. The control system (10) of claim 1 further comprising a relative-humidity sensor (60) means secured in communication with the reactant stream (16A, 16B) passing through the at least one of the anode flow field (28) and the cathode flow field (36), and also secured in communication with the relative-humidity controller (62) for communicating sensed information about the relative humidity of the reactant streams (16A, 16B) to the controller (62).

3. The control system (10) of claim 2, wherein the relative-humidity sensor (60) means is secured in communication with the cathode exhaust (42).

4. The control system (10) of claim 1 wherein the relative-humidity controller (62) is also secured in communication at least one of a fuel inlet valve (68) secured to the fuel inlet line (30), an oxidant inlet valve (72) secured to the oxidant inlet line (40), an oxidant blower (76) secured to the oxidant inlet line (40), an anode exhaust valve (86) secured to the anode exhaust (34), a cathode exhaust valve (82) secured to the cathode exhaust (42), the coolant loop (48).

5. The control system (10) of claim 1, wherein the water reservoir (18A, 18B) further comprises pores defined in at least one of a cathode porous body (92) secured in fluid communication with the cathode catalyst surface (26) of the membrane electrode assembly (22) and an anode porous body (92) secured in fluid communication with the anode catalyst surface (24) of the membrane electrode assembly (22).

6. The control system (10) of claim 1, wherein the water reservoir (18A, 18B) defines a water-retention volume dimensioned to retain an adequate volume of water (14) to maintain the relative humidity of the reactant streams (16A, 16B) at or about 1.00 during a predetermined duration of power output of the fuel cell (20) that is between about eighty percent and about one-hundred percent of a predetermined maximum power output of the fuel cell (20).

7. The control system (10) of claim 6, wherein the water reservoir (18A, 18B) defines a water-retention volume that is adequate to maintain a relative humidity of the reactant streams 16A, 16B at or about 1.0 whenever the predetermined duration of the power output of the fuel cell (20) that is between about eighty percent and about one-hundred percent of a predetermined maximum power output of the fuel cell (20) is about five minutes.

8. A method of operating the sealed coolant flow field fuel cell power plant (12) of claim 1 to control relative-humidity levels of reactant streams (16A, 16B) passing through the fuel cell (20), the method comprising:

a. controlling at least one of;

a pressure of the reactant streams (16A, 16B) within at least one of an anode flow field (28) and a cathode flow field (36);

a flow rate of the reactant streams (16A, 16B) flowing through at least one of the anode flow field (28) and the cathode flow field (36);

a temperature of a coolant fluid passing through a sealed coolant flow field (44);

a flow rate of the coolant fluid passing through the sealed coolant flow field (44);

b. so that water (14) moves from a water reservoir (18A, 18B) into the reactant stream (16A, 16B) whenever power generated by the fuel cell (20) is between about eighty percent and about one-hundred percent of a maximum power output of the fuel cell (20), and so that water (14) moves from the reactant stream (16A, 16B) into the water reservoir (18A, 18B) whenever power produced by the fuel cell (20) is less than about seventy-five percent of the maximum power output of the fuel cell (20).

9. The method of claim 8 further comprising, retaining an adequate volume of water (14) within the water reservoir (18A, 18B) to maintain the relative-humidity of the reactant streams (16A, 16B) at about 1.00 during a predetermined duration of power output of the fuel cell (20) that is between about eighty percent and about one-hundred percent of a predetermined maximum power output of the fuel cell (20).

10. The method of claim 8, wherein controlling water to move from the reactant stream (16A, 16B) into the water reservoir (18A, 18B) comprises controlling water to move water into pores defined in at least one of a cathode porous body (92) secured in fluid communication with the cathode catalyst surface (26) of the membrane electrode assembly (22) and an anode porous body (90) secured in fluid communication with the anode catalyst surface (24) of the membrane electrode assembly (22).