Systems and methods for fuel cell thermal management

• US 8,790,840 B2
• Filed: 03/10/2010
• Issued: 07/29/2014
• Est. Priority Date: 03/10/2010
• Status: Active Grant

• Current Assignee: DCNS SA (Government of France)
• Original Assignee: DCNS SA (Government of France)
• Inventors: LaVen, Sudha Rani, Rouveyre, Luc
• Primary Examiner(s): Ruddock, Ula C
• Assistant Examiner(s): Chmielecki, Scott J
• Application Number:
  US12/721,250
• Publication Number:
  US 20110223507A1
• Time in Patent Office: 1,602 Days
• US Class Current: 429/442
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 8/04029 Heat exchange using liquids
• CPC Class Codes: H01M 8/04298 Processes for controlling fuel cells or fuel cell systems
• CPC Class Codes: H01M 8/04313 characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
• CPC Class Codes: H01M 8/04335 of cathode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04358 of the coolant
• CPC Class Codes: H01M 8/04723 of the coolant
• CPC Class Codes: H01M 8/0485 of the electrolyte
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

Thermal and hydration management systems and methods for fuel cell systems, including control of electrolytic membrane hydration levels. In some embodiments, the thermal properties of the fuel cell are controlled based on a variable associated with the oxidant supply stream and/or a variable associated with the fuel cell energy output. In some embodiments, the temperature of the fuel cell is controlled based on the temperature of the oxidant supply stream. In some embodiments, the temperature range across the fuel cell stack is controlled based on the flow rate of the oxidant stream and the electrical output generated by the fuel cell stack. In some embodiments, the humidity within the fuel cell stack is controlled. In some embodiments, the liquid water content of the cathode exhaust stream is controlled.

Claims

1. A method of operating a fuel cell system that is configured to supply an electrical output to an energy consuming device and which comprises a fuel cell stack configured to produce the electrical output, an energy delivery system configured to supply the electrical output to the energy consuming device, a thermal management system configured to regulate the temperature of the fuel cell stack, a fuel supply system configured to supply fuel to the fuel cell stack, an oxidant supply system configured to supply oxidant to the fuel cell stack, a sensor system configured to detect a status of the fuel cell system, and a control system configured to control operation of the fuel cell system, the method comprising:

supplying a feedstock stream to a fuel processing assembly of the fuel supply system;

generating a mixed gas stream, which includes hydrogen gas and other gasses, from the feedstock stream within the fuel processing assembly;

purifying the mixed gas stream within a separation region of the fuel supply system to generate a byproduct stream, which includes a greater concentration of the other gasses than the mixed gas stream, and a fuel stream, which includes a greater concentration of hydrogen gas than the mixed gas stream;

supplying the fuel stream from the fuel supply system to the fuel cell stack;

supplying an oxidant stream from the oxidant supply system to the fuel cell stack;

producing the electrical output from the fuel cell stack;

supplying a thermal management fluid from the thermal management system and from a fuel cell stack fluid outlet to a fuel cell stack fluid inlet in a thermal management fluid recirculation loop, wherein the thermal management fluid recirculation loop includes a thermal management fluid conditioning assembly;

detecting a variable associated with the oxidant stream, wherein the variable associated with the oxidant stream is an oxidant inlet temperature associated with the oxidant stream at a fuel cell stack oxidant inlet;

detecting a temperature associated with the thermal management fluid; and

controlling the temperature associated with the thermal management fluid based at least in part on the variable associated with the oxidant stream by controlling a heat transfer from the thermal management fluid by the thermal management fluid conditioning assembly.

2. The method of claim 1, wherein supplying the oxidant stream further comprises supplying the oxidant stream to an oxidant conditioning assembly to produce a conditioned oxidant stream and supplying the conditioned oxidant stream to the fuel cell stack, wherein detecting the variable associated with the oxidant stream includes detecting a temperature associated with the conditioned oxidant stream, wherein the oxidant conditioning assembly includes an oxidant humidifier, and further wherein the conditioned oxidant stream is a humidified oxidant stream.

3. The method of claim 1, wherein the thermal management fluid conditioning assembly includes a radiator and a fan, and the method further comprises flowing the thermal management fluid within the radiator, propelling an air stream in heat exchange relationship with the radiator, and exchanging thermal energy between the thermal management fluid and the air stream, and further wherein controlling the heat transfer from the thermal management fluid by the thermal management fluid conditioning assembly comprises controlling a velocity of the air stream in heat exchange relationship with the radiator by controlling a speed of the fan.

4. The method of claim 1, wherein the temperature associated with the thermal management fluid is a fluid inlet temperature associated with the thermal management fluid at the fuel cell stack fluid inlet, detecting the temperature associated with the thermal management fluid includes detecting the fluid inlet temperature, and further wherein controlling the temperature associated with the thermal management fluid includes controlling the fluid inlet temperature responsive to the variable associated with the oxidant stream.

5. The method of claim 4, wherein controlling the fluid inlet temperature includes utilizing a feedback loop to control the fluid inlet temperature to correspond to the oxidant inlet temperature.

6. The method of claim 5, wherein controlling the fluid inlet temperature to correspond to the oxidant inlet temperature includes controlling the difference between the fluid inlet temperature and the oxidant inlet temperature.

7. The method of claim 5, wherein controlling the fluid inlet temperature to correspond to the oxidant inlet temperature includes controlling the fluid inlet temperature to be within 5°

C. of the oxidant inlet temperature.

8. The method of claim 1, wherein detecting the variable associated with the oxidant stream includes detecting a flow rate of the oxidant stream and an inlet temperature of the oxidant stream associated with the oxidant stream at an inlet to the fuel cell stack, wherein the method further includes detecting a magnitude of the electrical output supplied to the energy consuming device, wherein detecting the temperature associated with the thermal management fluid includes detecting a fluid inlet temperature associated with the thermal management fluid at the fuel cell stack fluid inlet and detecting a fluid outlet temperature associated with the thermal management fluid at the fuel cell stack fluid outlet, and further wherein controlling the temperature associated with the thermal management fluid includes controlling a relationship between the fluid inlet temperature and the fluid outlet temperature based at least in part on the flow rate of the oxidant stream, the inlet temperature of the oxidant stream, and the magnitude of the electrical output from the fuel cell stack.

9. The method of claim 8, wherein controlling the relationship between the fluid inlet temperature and the fluid outlet temperature includes controlling the difference between the fluid inlet temperature and the fluid outlet temperature.

10. The method of claim 8, wherein the thermal management fluid recirculation loop further includes a thermal management fluid drive assembly configured to control the flow rate of the thermal management fluid within the thermal management fluid recirculation loop, and further wherein controlling the relationship between the fluid inlet temperature and the fluid outlet temperature includes controlling the flow rate of the thermal management fluid within the thermal management fluid recirculation loop by controlling the thermal management fluid drive assembly.

11. The method of claim 10, wherein controlling the relationship between the fluid inlet temperature and the fluid outlet temperature includes controlling the difference between the fluid inlet temperature and the fluid outlet temperature.

12. The method of claim 11, further comprising determining a stoichiometry of an electrochemical reaction within the fuel cell stack based on the flow rate of the oxidant stream and the magnitude of the electrical output supplied to the energy consuming device and controlling the difference between the fluid inlet temperature and the fluid outlet temperature based on the stoichiometry.

13. The method of claim 12, further comprising calculating a target difference between the fluid inlet temperature and the fluid outlet temperature based on the stoichiometry, the inlet temperature of the oxidant stream, and a target fraction of water generated within the fuel cell stack that is vaporized within the fuel cell stack, and controlling the difference between the fluid inlet temperature and the fluid outlet temperature based on the target difference, wherein the thermal management fluid is a liquid, the thermal management fluid drive assembly includes a pump, and further wherein controlling the thermal management fluid drive assembly includes controlling the speed of the pump.

14. The method of claim 12, wherein controlling the difference between the fluid inlet temperature and the fluid outlet temperature includes utilizing a feedback loop to control the difference between the fluid inlet temperature and the fluid outlet temperature to correspond to the target difference.

15. The method of claim 14, wherein controlling the difference between the fluid inlet temperature and the fluid outlet temperature includes controlling the fluid outlet temperature to be less than a threshold fluid outlet temperature.

24. A fuel cell system, comprising:

a fuel cell stack configured to supply an electrical output to an energy consuming device;

a thermal management system configured to supply a thermal management fluid to the fuel cell stack to regulate the temperature of the fuel cell stack;

a fuel supply system configured to supply a fuel stream to the fuel cell stack;

an oxidant supply system configured to supply an oxidant stream to the fuel cell stack;

a fluid sensor configured to detect a temperature associated with the thermal management fluid;

an oxidant sensor configured to detect a variable associated with the oxidant stream; and

a control system programmed to control the operation of the fuel cell system according to the method of claim 1.

16. A fuel cell system, comprising:

a fuel processing assembly that is configured to receive a feedstock stream and to generate a mixed gas stream, which includes hydrogen gas and other gasses, therefrom;

a separation region that is configured to receive the mixed gas stream and to produce a fuel stream, which includes a greater concentration of hydrogen gas than the mixed gas stream, and a byproduct stream, which includes a greater concentration of the other gasses than the mixed gas stream, therefrom;

a fuel cell stack that is configured to receive the fuel stream, to produce an electrical output from the fuel stream, and to supply the electrical output to an energy consuming device;

a thermal management system configured to supply a thermal management fluid to the fuel cell stack to regulate the temperature of the fuel cell stack, wherein the thermal management system includes;

a thermal management fluid recirculation loop configured to circulate the thermal management fluid between a fuel cell stack fluid outlet and a fuel cell stack fluid inlet;

a radiator that is in heat exchange relationship with the thermal management fluid and an air stream; and

a fan that is configured to propel the air stream in heat exchange relationship with the radiator;

a fuel supply system configured to supply a fuel stream to the fuel cell stack;

an oxidant supply system including a humidifier that is configured to supply a humidified oxidant stream to the fuel cell stack;

a fluid sensor configured to detect a temperature associated with the thermal management fluid;

an oxidant sensor configured to detect a temperature associated with the humidified oxidant stream, wherein the temperature associated with the humidified oxidant stream is an oxidant inlet temperature associated with the humidified oxidant stream at a fuel cell stack oxidant inlet; and

a control system programmed to control the temperature associated with the thermal management fluid based at least in part on the oxidant inlet temperature by controlling a speed of the fan.

17. The system of claim 16, wherein the temperature associated with the thermal management fluid is a fluid inlet temperature associated with the thermal management fluid at the fuel cell stack fluid inlet, and further wherein the control system is programmed to utilize a feedback loop to control the fluid inlet temperature to correspond to the oxidant inlet temperature.

18. The system of claim 16, wherein the oxidant sensor is a first oxidant sensor configured to detect an oxidant inlet temperature associated with the humidified oxidant stream at the fuel cell stack oxidant inlet and the system includes a second oxidant sensor configured to detect a flow rate associated with the humidified oxidant stream, wherein the system further includes an electrical sensor configured to detect a magnitude of the electrical output from the fuel cell stack, wherein the fluid sensor is a first fluid sensor configured to detect a fluid inlet temperature associated with the thermal management fluid at the fuel cell stack fluid inlet, wherein the system further includes a second fluid sensor configured to detect a fluid outlet temperature associated with the thermal management fluid at the fuel cell stack fluid outlet, and further wherein the control system is programmed to control a difference between the fluid inlet temperature and the fluid outlet temperature responsive to the flow rate of the oxidant stream, the oxidant inlet temperature, and the magnitude of the electrical output from the fuel cell stack.

19. The system of claim 18, wherein the thermal management fluid recirculation loop further includes a thermal management fluid drive assembly configured to control a flow rate of the thermal management fluid within the thermal management fluid recirculation loop, and further wherein the control system is programmed to control the difference between the fluid inlet temperature and the fluid outlet temperature by controlling the thermal management fluid drive assembly.

20. The system of claim 19, wherein the control system determines a stoichiometry of an electrochemical reaction within the fuel cell stack based on the flow rate of the oxidant stream and the magnitude of the electrical output supplied to the energy consuming device, and further wherein the control system controls the difference between the fluid inlet temperature and the fluid outlet temperature based on the stoichiometry, the magnitude of the electrical output from the fuel cell stack, and the oxidant inlet temperature.

25. The system of claim 16, wherein the control system is further programmed to calculate a desired temperature associated with the thermal management fluid based upon the temperature associated with the humidified oxidant stream and to increase the speed of the fan responsive to determining that the temperature associated with the thermal management fluid is greater than the desired temperature associated with the thermal management fluid.

26. The system of claim 16, wherein the control system is further programmed to calculate a desired temperature associated with the thermal management fluid based upon the temperature associated with the humidified oxidant stream and to decrease the speed of the fan responsive to determining that the temperature associated with the thermal management fluid is less than the desired temperature associated with the thermal management fluid.

21. A fuel cell system, comprising:

a fuel processing assembly that is configured to receive a feedstock stream and to generate a mixed gas stream, which includes hydrogen gas and other gasses, therefrom;

a separation region that is configured to receive the mixed gas stream and to produce a fuel stream, which includes a greater concentration of hydrogen gas than the mixed gas stream, and a byproduct stream, which includes a greater concentration of the other gasses than the mixed gas stream, therefrom;

a fuel cell stack that is configured to receive the fuel stream, to produce an electrical output from the fuel stream, and to supply the electrical output to an energy consuming device;

a thermal management system configured to supply a thermal management fluid to the fuel cell stack to control the temperature of the fuel cell stack;

a fuel supply system configured to supply a fuel stream to the fuel cell stack;

an oxidant supply system configured to supply an oxidant stream to the fuel cell stack;

means for detecting a variable associated with the thermal management fluid;

means for detecting a variable associated with the oxidant supply system, wherein the variable associated with the oxidant supply system is an oxidant inlet temperature associated with the oxidant stream at an oxidant inlet to the fuel cell stack; and

means for controlling the variable associated with the thermal management fluid based at least in part on the oxidant inlet temperature.

22. The fuel cell system of claim 21, wherein the means for detecting a variable associated with the thermal management fluid includes a means for detecting a first variable associated with the thermal management fluid and a means for detecting a second variable associated with the thermal management fluid, the means for detecting a variable associated with the oxidant supply system includes a means for detecting a first variable associated with the oxidant supply system and a means for detecting a second variable associated with the oxidant supply system, the fuel cell system further includes a means for detecting a variable associated with the electrical output, and further wherein the means for controlling includes a first means for controlling the first variable associated with the thermal management fluid based at least in part on the first variable associated with the oxidant supply system and a second means for controlling a relationship between the first variable associated with the thermal management fluid and the second variable associated with the thermal management fluid based at least in part on the first variable associated with the oxidant supply system, the second variable associated with the oxidant supply system, and the variable associated with the electrical output.

23. The fuel cell system of claim 22, wherein the first variable associated with the thermal management fluid includes a fluid inlet temperature associated with the thermal management fluid at a fluid inlet to the fuel cell stack, the second variable associated with the thermal management fluid includes a fluid outlet temperature associated with the thermal management fluid at a fluid outlet from the fuel cell stack, the first variable associated with the oxidant supply system includes the oxidant inlet temperature associated with the oxidant stream at the oxidant inlet to the fuel cell stack, the second variable associated with the oxidant supply system includes an oxidant flow rate, and the variable associated with the electrical output of the fuel cell stack includes the electrical output generated by the fuel cell stack.