Storage of fuel cell energy during startup and shutdown or other power transitions

• US 20060068249A1
• Filed: 11/14/2005
• Published: 03/30/2006
• Est. Priority Date: 09/23/2003
• Status: Active Grant

• Current Assignee: Audi AG (Volkswagen AG)
• Original Assignee: UTC Power Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Fredette, Steven J.
• Granted Patent: US 7,790,303 B2
• Time in Patent Office: Days
• US Class Current: 429/429
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 8/04225 during start-up
• CPC Class Codes: H01M 8/04228 during shut-down
• CPC Class Codes: H01M 8/04302 applied during start-up
• CPC Class Codes: H01M 8/04303 applied during shut-down
• CPC Class Codes: H01M 8/0488 of fuel cell stacks
• CPC Class Codes: H01M 8/04947 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

During fuel cell startup and shutdown or other power reduction transitions of a fuel cell power plant, the excess electric energy generated by consumption of reactants is extracted by a storage control (200) in response to a controller (185) as current applied to an energy storage system 201 (a battery). In a boost embodiment, an inductor (205) and a diode (209) connect one terminal (156) of the stack (151) of the battery. An electronic switch connects the juncture of the inductor and the diode to both the other terminal (155) of the stack and the battery. The switch is alternately gated on and off by a signal (212) from a controller (185) until sufficient energy is transferred from the stack to the battery. In a buck environment, the switch and the inductor (205) connect one terminal (156) of the stack to the battery. A diode connects the juncture of the switch with the inductor to the other terminal (155) of the fuel cell stack and the battery.

Claims

1. A fuel cell power plant adapted to store energy which is removed from an associated fuel cell stack during transition from being not operating to operating, and vice versa, or other power reductions, comprising:

a controller interconnected with said fuel cell stack and responsive to signals received by said controller to cause said fuel cell stack to start up and to cause said fuel cell stack to shut down or otherwise vary generated power;

an energy storage system associated with said fuel cell power plant, said energy storage system responsive to electrical output provided thereto to store corresponding energy; and

storage control means operable by said controller, during a transition selected from (a) startup of said fuel cell power plant or (b) shutdown of said fuel cell power plant or other reduction of power supplied by said power plant, to extract, in the form of electrical output, energy generated by said fuel cell stack, said electrical output being provided to said energy storage device, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during said transition.

2. A power plant according to claim 1 wherein:

said storage control means comprises an inductor in series with a unilaterally conducting device extending from one electric output of said fuel cell stack to one input of said energy storage system and an electronic switch connected from the juncture of said inductor with said unilaterally conducting device to both a second electric output terminal of said fuel cell stack and a second terminal of said energy storage system; and

said electronic switch is gated on and off by a signal from said controller.

3. A power plant according to claim 1 wherein:

said storage control means comprises an inductor in series with an electronic switch extending from one electric output of said fuel cell stack to one input of said energy storage system and a unilaterally conducting device connected from the juncture of said inductor with said electronic switch to both a second electric output terminal of said fuel cell stack and a second terminal of said energy storage system; and

said electronic switch is cyclically gated on and off by a signal from said controller.

4. A method for controlling a fuel cell power plant adapted to store energy in an energy storage system associated with said fuel cell power plant which is removed from an associated fuel cell stack during transition from being not operating to operating, and vice versa, or other power reductions, in response to a controller interconnected with said fuel cell stack and responsive to signals received by said controller to cause said fuel cell stack to start up and to cause said fuel cell stack to shut down or otherwise vary power output, said energy storage system responsive to electrical output provided thereto to store corresponding energy, said method comprising:

during a transition selected from (a) startup of said fuel cell power plant or (b) shutdown of said fuel cell power plant or other reduction of power supplied by said fuel cell power plant, extracting, in the form of electrical output, energy generated by said fuel cell stack, said electrical output being provided to said energy storage device, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during said transition.

5. A fuel cell power plant adapted to store energy which is removed from an associated fuel cell stack during transitions including transitions from being not operating to being operating, and vice versa, and power reduction transitions from a first level of power demanded by a load, to a second level of power demanded by said load, said second level being lower than said first level;

comprising;

a fuel cell stack;

a controller interconnected with said fuel cell stack and responsive to one or more signals received by said controller to cause said fuel cell stack to start up, or to shut down, or to provide power to said load in response to demand for power by said load;

an energy storage system associated with said fuel cell power plant, said energy storage system responsive to electrical output provided thereto to store corresponding energy; and

storage control means, operable by said controller during transitions, selected from (a) startup of said fuel cell power plant, (b) shutdown of said fuel cell power plant, and (c) transition from providing power to said load at said first level to providing power to said load at said second level, to provide to said energy storage device at least a portion of the energy generated by said fuel cell stack in the form of electrical power output which is in excess of any power demanded by said load during any of said transitions, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during any of said transitions.

6. A method of operating a fuel cell power plant adapted to store energy, which is removed from an associated fuel cell stack, in an energy storage system associated with said fuel cell power plant during transitions including transitions from being not operating to being operating, and vice versa, and power reduction transitions from a first level of power demanded by a load, to a second level of power demanded by said load, said second level being lower than said first level, said energy storage system responsive to electrical output provided thereto to store corresponding energy in response to a controller interconnected with said fuel cell stack and responsive to one or more signals received by said controller to cause said fuel cell stack to start up, or to shut down, or to provide power to said load in response to demand for power by said load, said method comprising:

during transitions including (a) startup of said fuel cell power plant, (b) shutdown of said fuel cell power plant, and (c) transition from providing power to said load at said first level to providing power to said load at said second level, providing to said energy storage device at least a portion of the energy generated by said fuel cell stack in the form of electrical power output which is in excess of any power demanded by said load during any of said transitions, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during any of said transitions.

7. A fuel cell power plant adapted to store energy, comprising:

a fuel cell stack;

a controller interconnected with said fuel cell stack, said controller responsive to at least one received signal, and said controller configured to control said fuel cell stack to provide power to a load;

an energy storage system associated with said fuel cell power plant, said energy storage system responsive to power output provided thereto to store corresponding energy; and

a storage control operable by said controller, said storage control configured to protect said fuel cell stack from adverse fuel cell operating conditions during operating transitions.

8. A method of operating a fuel cell power plant to store energy in an energy storage system associated with said fuel cell power plant in response to a controller interconnected with a fuel cell stack associated with said power plant, said controller responsive to at least one received signal, and said controller configured to control said fuel cell stack to provide power to a load, said energy storage system responsive to power output provided thereto to store corresponding energy, said method comprising:

during operating transitions, protecting said fuel cell stack from adverse fuel cell operating conditions in response to an appropriately configured storage control operable by said controller.

9. A fuel cell power plant adapted to store energy which is removed from an associated fuel cell stack comprising:

a controller interconnected with said fuel cell stack and responsive to signals received by said controller to cause said fuel cell stack to start up and to cause said fuel cell stack to shut down; and

an energy storage system associated with said fuel cell power plant, said energy storage system responsive to electrical output provided thereto to store corresponding energy; and

storage control means operable by said controller, during a transition of operating conditions of said fuel cell stack, to extract in the form of electrical output, energy generated by said fuel cell stack, said electrical output being provided to said energy storage device, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during said transition.

10. A method of operating a fuel cell power plant to store energy, which is removed from an associated fuel cell stack, in an energy storage system associated with said fuel cell power plant, in response to a controller interconnected with said fuel cell stack and responsive to signals received by said controller to cause said fuel cell stack to start up and to cause said fuel cell stack to shut down, said energy storage system responsive to electrical output provided thereto to store corresponding energy, said method comprising:

during a transition of operating conditions of said fuel cell stack, extracting in the form of electrical output, energy generated by said fuel cell stack; and

providing said electrical output to said energy storage device, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during said transition.

11. A fuel cell power plant adapted to store energy which is removed from an associated fuel cell stack during a power reduction transition from a first level of power demanded by a load, to a second level of power demanded by said load, said second level being lower than said first level;

comprising;

a fuel cell stack;

a controller interconnected with said fuel cell stack and responsive to one or more signals received by said controller to cause said fuel cell stack to provide power to a load in response to demand for power by said load;

an energy storage system associated with said fuel cell power plant, said energy storage system responsive to electrical output provided thereto to store corresponding energy; and

storage control means, operable by said controller during a transition from providing power to said load at said first level to providing power to said load at said second level, to provide to said energy storage device at least a portion of the energy generated by said fuel cell stack in the form of electrical power output which is in excess of the power demanded by said load, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during said transition.

13. A power plant according to claim 11 wherein:

said storage control means comprises an electronic switch gated on and off by a signal from said controller.

14. A power plant according to claim 11 wherein:

said energy storage system comprises an electric battery.

15. A power plant according to claim 11 wherein:

said energy storage system comprises an electric battery disposed on a vehicle powered by said power plant.

16. A power plant according to claim 11 wherein:

said energy storage system comprises a capacitor.

12. A method of operating a fuel cell power plant to store energy in an energy storage system associated with said fuel cell power plant which is removed from an associated fuel cell stack during a power reduction transition, from a first level of power demanded by a load to a second level of power demanded by said load, said second level being lower than said first level, in response to a controller interconnected with said fuel cell stack and responsive to one or more signals received by said controller to cause said fuel cell stack to provide power to said load in response to demand for power by said load, said energy storage system responsive to electrical output provided thereto to store corresponding energy, said method comprising:

providing to said energy storage device, during a transition from providing power to said load at said first level to providing power to said load at said second level, at least a portion of the energy generated by said fuel cell stack in the form of electrical power output which is in excess of the power demanded by said load, thereby limiting the maximum average voltage in the fuel cells of said fuel cell stack during said transition.