초록 ▼

This application relates to a method and system for controlling the supply of fuel to a dead-ended hydrogen fuel cell. The invention may be utilized, for example, to more efficiently integrate the operation of a hydrogen fuel cell and a hydrogen generator, such as a reformer coupled with a hydrogen

This application relates to a method and system for controlling the supply of fuel to a dead-ended hydrogen fuel cell. The invention may be utilized, for example, to more efficiently integrate the operation of a hydrogen fuel cell and a hydrogen generator, such as a reformer coupled with a hydrogen separation unit. The invention ensures that the production and consumption of hydrogen are effectively balanced to avoid negative feed line pressure fluctuations. The fuel supply control subsystem and hydrogen consumption control subsystems are, however, “decoupled” and hence independently operable. The invention may include an accumulator disposed in a flow path between the hydrogen generator and the fuel cell for storing hydrogen under pressure. The accumulator is sufficiently large in volume such that the pressure of hydrogen in the flow path does not deviate substantially from a target pressure, even during the waste purging sessions. The system enables the use of low-cost pressure transducers in place of mass flow meters. In one aspect of the invention raffinate flow from the hydrogen separator can be controllably adjusted to regulate the temperature or other operating parameters of the reformer.

대표청구항 ▼

1. A method of regulating the current output of a dead-ended hydrogen fuel cell receiving a supply of hydrogen produced by a hydrogen generator comprising:(a) moving a volume of said hydrogen in a flow path from said hydrogen generator to said fuel cell, wherein said volume of said hydrogen has a ta

1. A method of regulating the current output of a dead-ended hydrogen fuel cell receiving a supply of hydrogen produced by a hydrogen generator comprising:(a) moving a volume of said hydrogen in a flow path from said hydrogen generator to said fuel cell, wherein said volume of said hydrogen has a target pressure value pset; (b) determining a target output current iset for said fuel cell; (c) operating said hydrogen generator at a hydrogen output level sufficient to enable said fuel cell to produce a current approximating said target output current iset; (d) measuring the pressure of said volume of hydrogen at a location in said flow path; and (e) if the pressure measured in step (d) differs from pset, adjusting the amount of hydrogen consumed by said fuel cell until the pressure of said volume of said hydrogen approximates pset. 2. The method as defined in claim 1, comprising determining a target hydrogen mass flow rate mset for said volume of hydrogen produced by said hydrogen generator corresponding to iset.3. The method as defined in claim 2, comprising operating said hydrogen generator at an output level sufficient to produce a hydrogen mass flow rate approximating mset.4. The method of claim 3, wherein said flow path comprises a hydrogen delivery vessel disposed between said hydrogen generator and said fuel cell for containing at least part of said volume of hydrogen, said delivery vessel having a pressure sensor for measuring the pressure of said volume of said hydrogen.5. The method of claim 4, wherein said hydrogen delivery vessel comprises an accumulator, said method comprising storing a portion of said volume of said hydrogen at pressure in said accumulator.6. The method of claim 5, further comprising periodically purging hydrogen from said fuel cell during a time-limited purging session.7. The method of claim 6, wherein said accumulator is sufficiently large in volume such that the pressure of said portion of said volume of hydrogen contained therein does not deviate substantially from pset during said purging session.8. The method as defined in claim 1, further comprising periodically purging hydrogen from said fuel cell during a purging session, wherein adjustment of the said amount of hydrogen consumed by said fuel cell is temporarily suspended during said purging session.9. The method as defined in claim 1, wherein said hydrogen generator and said fuel cell are damped to not respond to high frequency transient hydrogen pressure fluctuations within said vessel.10. The method of claim 4, wherein said hydrogen mass flow rate is estimated in accordance with the following formula: where {dot over (m)}in is the estimated mass flow produced by said hydrogen generator and, {dot over (m)}out is the estimated mass flow of hydrogen consumed by said fuel cell, and whereinV=Volume of hydrogen within the vessel R=Universal gas constant T=Temperature of the vessel dP/dt=Time rate of change of pressure in the vessel nc=Number of cells in fuel cell stack igross=Gross current produced by the fuel cell F=Faradays constant. 11. The method of claim 1, wherein said hydrogen generator receives a supply of fuel from a fuel supply subsystem and wherein the step of operating said hydrogen generator at a hydrogen output level sufficient to enable said fuel cell to produce a current approximating said target output current iset comprises:(a) measuring the current igross outputted by said fuel cell; (b) generating a fuel supply control command based on a comparison of iset and igross; and (c) delivering fuel from said fuel supply subsystem to said hydrogen generator in an amount corresponding to said fuel control command. 12. The method of claim 3, wherein said hydrogen generator receives a supply of fuel from a fuel supply subsystem and wherein the step of operating said hydrogen generator at a hydrogen output level sufficient to produce a hydrogen mass flow rate approximating mset comprises:(a) measuring the current igross outputted by said fuel cell; (b) estimating the mass flow rate of said volume of said hydrogen based on the measured pressure of said volume of said hydrogen and the measured current igross outputted by said fuel cell; (c) generating a fuel supply control command based on a comparison of mset and said mass flow rate estimated in step (b) above; and (d) delivering fuel from said fuel supply subsystem to said hydrogen generator in an amount corresponding to said fuel supply control command. 13. The method as defined in claim 12, wherein said flow path comprises a hydrogen delivery vessel disposed between said hydrogen generator and said fuel cell for containing at least part of said volume of hydrogen, and wherein said mass flow rate is estimated in accordance with the following formula: where {dot over (m)}in is the estimated mass flow produced by said hydrogen generator and, {dot over (m)}out is the estimated mass flow of hydrogen consumed by said fuel cell, and whereinV=Volume of hydrogen within the vessel R=Universal gas constant T=Temperature of the vessel dp/dt=Time rate of change of pressure in the vessel nc=Number of cells in fuel cell stack igross=Gross current produced by the fuel cell F=Faradays constant. 14. The method as defined in claim 13, wherein said hydrogen generator is a reformer.15. The method as defined in claim 14, wherein said hydrogen delivery vessel is an accumulator for storing a portion of said volume of said hydrogen at pressure.16. The method as defined in claim 11, wherein said fuel supply control command is generated by a process controller, wherein said method comprises calculating the difference between the target current iset and the measured current igross and providing said difference as an input to said controller.17. The method as defined in claim 12, wherein said fuel supply control command is generated by a process controller, wherein said method comprises calculating the difference between the target mass flow rate mset and the estimated actual mass flow rate and providing said difference as an input to said controller.18. The method as defined in claim 16, comprising measuring at least one operating parameter of said hydrogen generator and providing said measured parameter as an input to said process controller.19. The method as defined in claim 17, comprising measuring at least one operating parameter of said hydrogen generator and providing said measured parameter as an input to said process controller.20. The method of claim 1, further comprising controlling the amount of current drawn from said fuel cell.21. The method as defined in claim 1, comprising generating a hydrogen consumption control command based on a comparison of the measured pressure of said hydrogen within said flow path and pset.22. The method as defined in claim 21, wherein said hydrogen consumption control command is delivered to said fuel cell for controlling the amount of hydrogen consumed by said fuel cell.23. The method as defined in claim 21, further comprising providing a power converter for controlling the amount of current drawn from said fuel cell, wherein said hydrogen consumption control command is delivered to said power converter.24. The method as defined in claim 1, comprising adjusting the rate of hydrogen consumed by said fuel cell at sufficiently frequent intervals to ensure that said pressure of said volume of hydrogen in said flow path is between a minimum and a maximum pressure value.25. The method as defined in claim 1, wherein said amount of hydrogen consumed by said fuel cell is adjusted when said measured pressure of said hydrogen in said flow path differs from pset by a predetermined amount.26. The method as defined in claim 1, wherein said amount of hydrogen consumed by said fuel cell is adjusted continuously as said measured pressure of said hydrogen in said flow path differs from pset.27. The method as defined in claim 1, wherein said pressure of said volume of hydrogen is measured by a pressure sensor located in said flow path.28. The method as defined in claim 27, wherein said pressure sensor is a pressure transducer.29. The method as defined in claim 1, further comprising separating the output of said hydrogen generator into a hydrogen enriched gas stream delivered through said flow path to said fuel cell and a hydrogen depleted gas stream used to regulate the temperature of said hydrogen generator.30. The method as defined in claim 29, comprising adjusting the value of pset depending upon the desired operating temperature of said hydrogen generator.31. The method as defined in claim 1, comprising measuring the operating temperature of said hydrogen generator and adjusting the value of pset depending upon the measured operating temperature of said hydrogen generator.32. The method as defined in claim 11, wherein said fuel supply control command is generated by a process controller which receives data inputs from the group consisting of (a) the differential between iset and igross and (b) hydrogen generator process data, and wherein the process of generating said control command is either feedback, feedforward or a combination thereof.33. The method as defined in claim 12, wherein said fuel supply control command is generated by a process controller which receives data inputs from the group consisting of (a) the differential between mset and the estimated mass flow rate and (b) hydrogen generator process data, and wherein the process of generating said control command is either feedback, feedforward or a combination thereof.34. A system for regulating the current output of a dead-ended hydrogen fuel cell receiving a supply of hydrogen produced by a hydrogen generator comprising:(a) a hydrogen delivery vessel disposed between said hydrogen generator and said fuel cell for delivering a flow of hydrogen from said hydrogen generator to said fuel cell; (b) a pressure sensor located in said delivery vessel for measuring the pressure of said hydrogen; (c) a first controller receiving input from said pressure sensor, wherein said first controller generates a hydrogen consumption control command; (d) a current sensor for measuring the current produced by said fuel cell; and (e) a second controller receiving input from said current sensor, wherein said second controller generates a fuel supply control command, wherein said first controller is operatively connected to said fuel cell to regulate the amount of hydrogen consumed by said fuel cell and wherein said second controller is operatively connected to said hydrogen generator to regulate the amount of hydrogen produced by said hydrogen generator.35. The system as defined in claim 34, wherein said first controller generates said hydrogen consumption control command based on a comparison of the hydrogen pressure measured by said pressure sensor and a target hydrogen pressure pset.36. The system as defined in claim 35, wherein said first controller does not receive input from said current sensor.37. The system as defined in claim 35, wherein said second controller generates said fuel supply control command based on a comparison of the fuel cell current measured by said current sensor and a target fuel cell current iset.38. The system as defined in claim 37, comprising a hydrogen mass flow processor which receives input from said pressure sensor and said current sensor, wherein said hydrogen mass flow processor calculates a target hydrogen mass flow mset corresponding to iset and a hydrogen mass flow estimate {dot over (m)}in according to the following formula: where {dot over (m)}in is the estimated mass flow produced by said hydrogen generator and, {dot over (m)}out is the estimated mass flow of hydrogen consumed by said fuel cell, and whereinV=Volume of hydrogen within the vessel R=Universal gas constant T=Temperature of the vessel dp/dt=Time rate of change of pressure in the vessel as measure by the pressure sensor nc=Number of cells in fuel cell stack igross=Gross current produced by the fuel cell as measured by the current sensor F=Faradays constant. 39. The system as defined in claim 38, wherein said second controller comprises said mass flow processor.40. The system as defined in claim 34, further comprising a power converter operatively connected to said fuel cell for controlling the amount of current drawn from said fuel cell.41. The system as defined in claim 40, wherein said hydrogen consumption control command is transmitted from said first controller to said power converter.42. The system as defined in claim 34, further comprising a third controller operatively connected to said fuel cell for controlling the amount of current produced by said fuel cell, wherein said hydrogen consumption control signal is transmitted from said first controller to said third controller.43. The system as defined in claim 37, further comprising a fuel supply subsystem for delivering fuel to said hydrogen generator, wherein said fuel supply control command is transmitted from said second controller to said fuel supply subsystem.44. The system as defined in claim 37, wherein said target hydrogen pressure pset and said target fuel cell current iset are dynamically variable.45. The system as defined in claim 37, wherein said target hydrogen pressure pset and target fuel cell current iset are predetermined.46. The system as defined in claim 35, wherein said system further comprises a purge valve operatively connected to said fuel cell to permit periodic expulsion of hydrogen from said fuel cell during a time-limited purging session.47. The system as defined in claim 46, wherein said hydrogen delivery vessel comprises an accumulator for storing a volume of said hydrogen under pressure, wherein said accumulator is sufficiently large in size such that the measured pressure of hydrogen within said vessel does not deviate substantially from pset during said purging session.48. The system as defined in claim 43, wherein said hydrogen generator is a fuel reformer for producing said hydrogen.49. The system as defined in claim 48, wherein said hydrogen generator comprises a hydrogen separator for separating said hydrogen produced by said reformer into a first portion delivered through said vessel to said fuel cell and a second portion used to heat said reformer.50. The system as defined in claim 49, further comprising a fourth controller for controlling the temperature of said reformer, wherein said fourth controller determines the value of pset based at least in part on the target temperature of said reformer.51. The system as defined in claim 37, wherein the value of iset varies depending upon the amount of current drawn from said fuel cell by said power converter as required to service a load or charge a battery.52. The system as defined in claim 49, wherein said hydrogen separator is a palladium membrane hydrogen separator.53. The system as defined in claim 34, wherein said first controller is a PID controller.54. A fuel cell control system comprising:(a) a dead-ended hydrogen fuel cell; (b) a hydrogen generator for delivering a supply of hydrogen to said fuel cell; (c) a hydrogen delivery vessel disposed between said hydrogen generator and said fuel cell for delivering a flow of hydrogen from said hydrogen generator to said fuel cell; (d) a pressure sensor located in said delivery vessel for measuring the pressure of said hydrogen; (e) a first controller receiving input from said pressure sensor, wherein said first controller generates a hydrogen consumption control command; (f) a current sensor for measuring the current produced by said fuel cell; and (g) a second controller receiving input from said current sensor, wherein said second controller generates a fuel supply control command, wherein said first controller is operatively connected to said fuel cell to regulate the amount of hydrogen consumed by said fuel cell and wherein said second controller is operatively connected to said hydrogen generator to regulate the amount of hydrogen produced by said hydrogen generator.55. The system as defined in claim 54, wherein said first and second controllers are independently operable.56. The system as defined in claim 54, wherein said first controller does not receive input from said current sensor.