JP5051982B2 - Control of fuel cell using current density distribution measuring device - Google Patents

Description

  The present invention relates to a technique for measuring a current density distribution of a fuel cell.

  Conventionally, a method for measuring a current density distribution in an electrode has been proposed for various purposes such as flow path design evaluation, failure detection, and quality assurance of a fuel cell. For example, Patent Document 1 discloses a method of measuring a current density distribution of a separator by conducting a plurality of electrodes to a separator via a carbon terminal and measuring a current flowing through each electrode. Furthermore, a technique (Patent Document 2) for detecting an abnormality using the measured current density distribution and a technique for suppressing an excessively partial reaction state (Patent Document 3) have been proposed.

JP 2004-152501 A JP 2004-95301 A JP-A-9-259913

  However, conventionally, it has not been studied to optimize the electrochemical reaction control in each fuel cell by absorbing individual differences and aging of each fuel cell constituting the fuel cell stack.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique for realizing optimal control in a fuel cell system including a measuring device that measures a current density distribution.

The present invention provides a control device for a fuel cell system in order to solve at least a part of the problems described above. In the control device of the present invention,
The fuel cell system includes a plurality of fuel cells stacked, and a fuel having at least one current density sensor that measures a current density distribution in a plane perpendicular to the stacking direction between the stacked fuel cells. With a battery stack,
The control device observes an internal state of the fuel cell stack based on the measured current density distribution, and operates a fluid supplied to the fuel cell stack according to the observed internal state. Control the output current distribution in the fuel cell stack to be uniform,
The operation of the fluid includes an operation of at least one of a flow rate of a fuel gas, a flow rate of an oxidant gas, a flow rate of a cooling medium, and a humidification amount of the oxidant gas.

  In the control device of the present invention, the internal state of the fuel cell stack is observed based on the measured current density distribution, and the fluid supplied to the fuel cell stack is operated according to the observed internal state to operate the fuel. Since the output current distribution in the battery stack is made uniform, individual differences and aging of each fuel cell constituting the fuel cell stack can be absorbed to optimize the electrochemical reaction control in each fuel cell. it can.

In the above control device,
The fuel cell stack is a polymer electrolyte fuel cell,
The control device detects dryout in response to a decrease in current density distribution in a region relatively close to the upstream side, and detects flooding in response to decrease in current density distribution in a region relatively close to the downstream side. , Executing dryout reduction processing according to the detection of the dryout, executing flooding reduction processing according to the detection of the flooding,
The dryout reduction process is a process for reducing the dryout by increasing at least one of a humidification amount of the oxidant gas and a flow rate of the cooling medium,
The flooding reduction process may be a process of reducing the flooding by executing at least one of an increase in the flow rate of the oxidant gas and a reduction in the humidification amount of the oxidant gas. Note that dryout and flooding may be detected more precisely by measuring the humidity of the gas discharged from the fuel cell stack.

  The present invention relates to a fuel cell control method, a fuel cell stack state observation device or method, a computer program for fuel cell control, a recording medium storing this program, a vehicle equipped with this fuel cell system, etc. The present invention can be realized in various other modes.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
A. Configuration of a fuel cell system in an embodiment of the present invention:
B. Variations:

A. Configuration of a fuel cell system in an embodiment of the present invention:
FIG. 1 is a block diagram showing a configuration of a fuel cell system 100 according to an embodiment of the present invention. The fuel cell system 100 includes a fuel cell stack 10, an air supply system 30 that supplies air as an oxidizing gas to the fuel cell stack 10, and a hydrogen gas circulation system 20 that circulates hydrogen gas as fuel gas through the fuel cell stack 10. And a hydrogen gas supply system 40 that supplies hydrogen gas to the hydrogen gas circulation system 20 and a control unit 50. The control unit 50 controls the air supply system 30, the hydrogen gas supply system 40, and the hydrogen gas circulation system 20.

  The fuel cell stack 10 is a fuel cell having a stack structure in which a plurality of fuel cells 200 and a plurality of current distribution measuring sensors described later are stacked. Each of the fuel cells 200 includes a fuel cell air passage 35 and a fuel cell hydrogen passage 25 therein.

  The air supply system 30 is a system for supplying humidified air to the fuel cell air flow path 35. The air supply system 30 includes a blower 31 that sucks outside air, a humidifier 39 that humidifies the sucked air, a humidified air supply pipe 34 that supplies the humidified air to the air flow path 35 in the fuel cell, a fuel And an exhaust pipe 36 for exhausting from the air flow path 35 in the battery.

  The hydrogen gas circulation system 20 includes a circulation pump 28 for circulating the hydrogen gas inside the hydrogen gas circulation system 20, and a hydrogen gas supply that supplies the hydrogen gas discharged from the circulation pump 28 to the hydrogen flow path 25 in the fuel cell. A pipe 24, an exhaust gas pipe 26 for supplying hydrogen gas containing water from the hydrogen flow path 25 in the fuel cell to the gas-liquid separator 29, and a gas for separating the water and hydrogen gas and supplying the hydrogen gas to the circulation pump 28 A liquid separation unit 29. The hydrogen gas supply system 40 includes a hydrogen tank 42 that stores hydrogen gas, and a hydrogen valve 41 that controls the supply of hydrogen gas to the hydrogen gas circulation system 20.

  FIG. 2 is an explanatory diagram showing the configuration of the fuel cell stack 10 in the embodiment of the present invention. The fuel cell stack 10 is a solid polymer electrolyte fuel cell. The fuel cell stack 10 includes sub-stacks 10a, 10b, 10c, and 10d each having five fuel cells 200, and five current distribution measurement sensors 125a that are disposed at both ends of each sub-stack 10a, 10b, 10c, and 10d. , 125b, 125c, 125d, and 125e. The five current distribution measurement sensors 125a, 125b, and 125c can measure the output current distribution at the boundary surfaces of the sub-stacks 10a, 10b, 10c, and 10d.

  Each of the sub stacks 10a, 10b, 10c, and 10d is configured so that the air flow rate, the humidification amount, and the hydrogen gas flow rate can be controlled independently. That is, the air supply system 30 and the hydrogen gas circulation system 20 are configured so that the air flow rate, the humidification amount, and the hydrogen gas flow rate can be independently controlled for each of the sub-stacks 10a, 10b, 10c, and 10d.

  The control performed in this embodiment absorbs individual differences regarding the membrane resistance of each of the substacks 10a, 10b, 10c, and 10d so that power can be generated in a uniform state within each of the substacks 10a, 10b, 10c, and 10d. One of the purposes is to The individual difference regarding membrane resistance means the ease of occurrence of flooding and dryout. Flooding refers to a phenomenon in which the amount of moisture in the vicinity of an electrolyte membrane (not shown) is excessive and the performance of the battery is lowered by inhibiting gas diffusion. On the other hand, dryout refers to a phenomenon in which the performance of a battery decreases due to a lack of moisture supplied to an electrolyte membrane (not shown) and a decrease in ionic conductivity.

  In a solid polymer electrolyte type fuel cell, it is difficult to uniformly reduce the membrane resistance in the reaction gas channel over the entire channel. This is because, in general, there is an individual difference between the fuel cells 200 in addition to the property that dry out is likely to occur at the channel inlet and flooding is likely to occur due to the generated water at the channel outlet.

  FIG. 3 is an explanatory diagram showing a method for measuring the current density distribution of the fuel cell stack 10 in the embodiment of the present invention. In FIG. 3, in the fuel cell stack 10, the current distribution measurement sensors 125a, 125c, 125d, and 125e other than the current distribution measurement sensor 125b are not shown so that the drawing is not complicated. The fuel cell stack 10 further includes end plates 109 and 111 for outputting electric power, a terminal plate 107 disposed between the end plate 109 and the fuel cell 200, an end plate 111 and the fuel cell 200. And a terminal plate (not shown) disposed between the two. The end plates 109 and 111 are connected to the load 110.

  In this embodiment, the fuel battery cell 200 includes a membrane electrode assembly 202 and two carbon separators 203 and 204 that sandwich the membrane electrode assembly 202 from both sides. The two separators 203 and 204 are formed with gas flow paths (not shown) through which the reaction gas flows on the membrane electrode assembly 202 side. The fuel cell 200 generates electric power by the reaction of the reaction gas and outputs it to the outside through the two separators 203 and 204.

  FIG. 4 is an enlarged view of the current distribution measuring sensor 125b. The current distribution measurement sensor 125 b includes a plurality of measurement electrodes 120. Each of the measurement electrodes 120 includes a rod 128, two current collecting electrodes 124 and 127 connected to both ends of the rod 128, and a current sensor 126. The five current distribution measurement sensors 125a, 125b, 125c, 125d, and 125e all have the same configuration.

  In this embodiment, the current sensor 126 is a sensor using a Hall element that can measure a change in magnetic field with high sensitivity. The current sensor 126 outputs an electrical signal corresponding to a magnetic field that changes according to the current flowing through the rod 128. The controller 50 measures the current density distribution based on the output electrical signal. However, in this embodiment, measurement is performed for the purpose of realizing uniform operation in each fuel cell 200 as a whole, and therefore, a relative value of the current density distribution is measured.

  The measurement of the current density distribution of the fuel cell is not limited to the above-described method. For example, Japanese Patent Application Laid-Open No. 2004-152501 (Patent Document 1), Japanese Patent Application Laid-Open No. 2004-95301 (Patent Document 2), and Japanese Patent Application Laid-Open No. Hei 9-. A method disclosed in other technical documents such as 259913 (Patent Document 3) can also be used.

  FIG. 5 is an explanatory diagram showing an example of the current density distribution of the fuel cell stack 10 according to the embodiment of the present invention. In FIG. 5, the horizontal axis and the vertical axis indicate the measurement position and current density distribution in the stacking direction of the fuel cell stack 10, respectively. White circles and black circles are obtained by normalizing and plotting measured values of the current density distribution in the vicinity of the inlet side and outlet side channels in the oxidant gas channel, respectively.

  In this example, each fuel cell 200 is controlled in an optimal state, that is, in each fuel cell 200, in the vicinity of an oxidant gas inlet side flow path (not shown) and an oxidant gas outlet side flow path. A uniform current density distribution is measured in the vicinity of (not shown).

  FIG. 6 is an explanatory diagram illustrating an example of a current density distribution in a state where dryout has occurred in all the fuel cells 200 of the fuel cell stack 10. In this example, the current density distribution in the vicinity of the oxidant gas inlet side flow path is lowered. This decrease is caused by the occurrence of dryout in the oxidant gas inlet side flow path.

  In such a case, the control unit 50 (FIG. 1) can reduce dryout by increasing the amount of humidification by controlling the humidifier 39, for example.

  FIG. 7 is an explanatory diagram illustrating an example of a current density distribution in a state where flooding has occurred in all the fuel cells 200 of the fuel cell stack 10. In this example, the current density distribution in the vicinity of the oxidant gas outlet side flow path is lowered. This decrease is due to the occurrence of flooding due to the generation of excess product water in the oxidant gas outlet side flow path.

  In such a case, the control unit 50 (FIG. 1) purges excess generated water to reduce flooding by controlling the air supply system 30 and increasing the amount of air supply as an oxidant gas, for example. be able to. Further, after purging, the generation of flooding can be suppressed by controlling the humidifier 39 to reduce the humidification amount.

  FIG. 8 is an explanatory diagram showing an example of a current density distribution in a state where both dryout and flooding occur in the fuel cell stack 10. In this example, dryout occurs in the substack 10a (FIG. 2), and flooding occurs in the substack 10c. As described above, in this embodiment, the five current distribution measuring sensors 125a, 125b, 125c, 125d, and 125e are provided at both ends of each of the substacks 10a, 10b, 10c, and 10d. The internal state for every 10b, 10c, 10d can be estimated.

  In such a case, the control unit 50 performs control to suppress dryout for the substack 10a, and eliminates flooding and suppresses reoccurrence for the substack 10c. It is possible to perform control to realize

  As described above, in the embodiment of the present invention, the current density distribution is measured three-dimensionally for the entire fuel cell stack 10 to detect dryout and flooding and to realize a control system for eliminating these. Has been. Thereby, the individual difference and secular change of the fuel cell 200 which comprises the fuel cell stack 10 are absorbed, and the whole fuel cell 200 can be drive | operated efficiently.

  In this embodiment, in order to make the explanation easy to understand, paying attention to dryout and flooding in the solid polymer electrolyte fuel cell, the internal state of the fuel cell stack 10 is observed, and the fuel cell system 100 based on this observation. The control method is described. However, the present invention is not limited to the solid polymer electrolyte fuel cell, and a control system that efficiently operates the entire fuel cell 200 is configured by monitoring a partial operation state in other types of fuel cells. can do.

B. Variations:
As mentioned above, although several embodiment of this invention was described, this invention is not limited to such embodiment at all, and implementation in various aspects is possible within the range which does not deviate from the summary. It is. For example, the following modifications are possible.

B-1. In the above embodiment, the flow rate of the oxidant gas and the humidification amount of the oxidant gas are manipulated, but the flow rate of the coolant and the flow rate of the fuel gas may be manipulated. In general, the operation of the fluid in the present invention may include at least one of the flow rate of the fuel gas, the flow rate of the oxidant gas, the flow rate of the cooling medium, and the humidification amount of the oxidant gas.

  For the coolant flow rate operation, for example, the coolant flow rate is decreased to increase the temperature of the fuel cell stack to suppress flooding, or the coolant flow rate is increased to decrease the temperature of the fuel cell stack. Thus, an operation for suppressing the occurrence of dryout can be realized. For example, the flow rate of the fuel gas can be increased by increasing the flow rate of the fuel gas to suppress a decrease in the electrochemical reaction downstream of the fuel gas flow path, or the flow rate of the fuel gas can be reduced, for example, by reducing the flow rate of the fuel gas. An increase operation is feasible.

B-2. In the above embodiment, the current density distribution is measured at five locations of the fuel cell stack using the five current distribution measurement sensors 125a, 125b, 125c, 125d, and 125e. However, only one current distribution measurement sensor may be used. . The fuel cell stack used in the present invention includes at least one current density sensor in which a plurality of fuel cells are stacked and a current density distribution in a plane perpendicular to the stacking direction is measured between the stacked fuel cells. Any fuel cell stack having

B-3. In the above embodiment, the configuration in which the fluid flow path is divided is not disclosed. Also good.

The block diagram which shows the structure of the fuel cell system 100 in the Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the structure of the fuel cell stack 10 in the Example of this invention. Explanatory drawing which shows the measuring method of the current density distribution of the fuel cell stack 10 in the Example of this invention. The enlarged view of the current distribution measurement sensor 125b. Explanatory drawing which shows an example of the current density distribution of the fuel cell stack 10 in the Example of this invention. FIG. 3 is an explanatory diagram showing an example of a current density distribution in a state where dryout has occurred in all the fuel cells 200 of the fuel cell stack 10. FIG. 3 is an explanatory diagram showing an example of current density distribution in a state where flooding has occurred in all the fuel cells 200 of the fuel cell stack 10. FIG. 3 is an explanatory diagram showing an example of a current density distribution in a state where both dryout and flooding occur in the fuel cell stack 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 10a, 10b, 10c, 10d ... Substack 20 ... Hydrogen gas circulation system 24 ... Hydrogen gas supply piping 25 ... Hydrogen flow path in fuel cell 26 ... Exhaust gas piping 28 ... Circulation pump 29 ... Gas-liquid separation part 30 DESCRIPTION OF SYMBOLS ... Air supply system 31 ... Blower 34 ... Humidification air supply piping 35 ... Fuel cell air flow path 36 ... Exhaust pipe 39 ... Humidifier 40 ... Hydrogen gas supply system 41 ... Hydrogen valve 42 ... Hydrogen tank 50 ... Control part 100 ... Fuel Battery system 107 ... Terminal plate 109 ... End plate 110 ... Load 111 ... End plate 120 ... Measurement electrode 124 ... Current collecting electrode 125a, 125b, 125c, 125d, 125e ... Current distribution measuring sensor 126 ... Current sensor 128 ... Rod 200 ... Fuel cell 202 ... Membrane electrode assembly 203, 204 ... Regulator

Claims (5)

A control device for a fuel cell system,
The fuel cell system with a plurality of fuel cells are stacked, a plurality of current density sensor for measuring a current density distribution in a plane perpendicular to the stacking direction between the stacked fuel cell, the laminate Comprising fuel cell stacks arranged at predetermined intervals across the direction ,
The control device includes the fuel cell stack in the vertical plane and in the stacking direction based on a current density distribution in the vertical plane measured by the plurality of current density sensors and a current density distribution in the stacking direction. A control device that detects the non-uniformity of the internal moisture state . The control device according to claim 1,
The fuel cell stack is a polymer electrolyte fuel cell,
The control device detects dryout in response to a decrease in current density distribution in a region relatively close to the upstream side, and detects flooding in response to decrease in current density distribution in a region relatively close to the downstream side. , Executing dryout reduction processing according to the detection of the dryout, executing flooding reduction processing according to the detection of the flooding,
The dry-out mitigation process is a process in which at least one of the flow rate of the humidification amount and the cold却媒of acid agent gas to increase the, reduce the dryout,
The flooding reduction processing is a control device that executes at least one of an increase in the flow rate of the oxidant gas and a reduction in the humidification amount of the oxidant gas to reduce the flooding. A fuel cell system,
A plurality of fuel cells are stacked, and a plurality of current density sensors that measure a current density distribution in a plane perpendicular to the stacking direction between the stacked fuel cells are provided at predetermined intervals in the stacking direction. An arranged fuel cell stack;
The control device according to claim 1 or 2,
A fuel cell system comprising: A control method for a fuel cell system, comprising:
(A) computer, a plurality of fuel cells are stacked, a plurality of current density sensor for measuring a current density distribution in a plane perpendicular to the stacking direction between the stacked fuel cell, the laminate A preparation step of preparing fuel cell stacks arranged at predetermined intervals in a direction ;
(B) The fuel in the vertical plane and in the stacking direction based on the current density distribution in the vertical plane measured by the plurality of current density sensors and the current density distribution in the stacking direction. A moisture state detection step for detecting the non-uniformity of the moisture state inside the battery stack ;
Bei El, control methods. A plurality of fuel cells are stacked, and a plurality of current density sensors that measure a current density distribution in a plane perpendicular to the stacking direction between the stacked fuel cells are provided at predetermined intervals in the stacking direction. a computer program for executing the control of the fuel cell system provided with an arrangement fuel cell stack in a computer,
Based on the current density distribution in the vertical plane measured by the plurality of current density sensors and the current density distribution in the stacking direction , the moisture state in the fuel cell stack in the vertical plane and in the stacking direction is determined. It characterized the Turkey to realize the water state detection function for detecting the nonuniformity in the computer, the computer program.

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