Fuel cell system and method for inspecting fuel cell system

Abstract

A fuel cell unit 1a of the present disclosure comprises a plurality of fuel cell stacks 10, a measuring instrument 20, a first feeder 30, a second feeder 40, and a controller 50. The plurality of fuel cell stacks 10 are electrically connected in series. The measuring instrument 20 measures the voltage of the plurality of fuel cell stacks 10 electrically connected in series. The controller 50 causes the measuring instrument 20 to measure a voltage generated in the plurality of fuel cell stacks 10 under a first condition. Under the first condition, a plurality of fuel electrodes 11 of the plurality of fuel cell stacks 10 continue to receive fuel gas supply, and a plurality of oxidant electrodes 12 of the plurality of fuel cell stacks 10 are sequentially subjected to a process in which oxidant gas is supplied for a predetermined period and then the oxidant gas supply is stopped.

Description

Fuel cell system and fuel cell system inspection method

[0001] The present disclosure relates to a fuel cell system and a method for inspecting a fuel cell system.

[0002] Patent Document 1 describes a method for diagnosing a fuel cell stack. This method diagnoses a fuel cell including a stack in which a plurality of unit cells are electrically connected in series, a fuel gas manifold, and an oxidizer gas manifold. A hydrogen-containing gas containing a certain concentration of hydrogen is supplied to the fuel electrode, and an oxygen-containing gas containing a certain concentration of oxygen is supplied to the oxidizer electrode. The correspondence between the change in the supply amount of the oxygen-containing gas over time and the corresponding change in the voltage generated in the stack over time is recorded. If the voltage generated in the stack changes abruptly in response to the change in the supply amount of the oxygen-containing gas, a hydrogen leak in the stack is detected. The hydrogen leakage amount in the stack is calculated from the correspondence between the change in the supply amount of the oxygen-containing gas over time and the voltage generated in the stack. If this hydrogen leakage amount is equal to or greater than the hydrogen leakage amount when the stack is normal, the occurrence of a cross leak is identified.

[0003] Patent Document 2 describes a fuel cell system equipped with a predetermined cross leak determination means. This fuel cell system includes a voltage measurement means, a first stopping means, a second stopping means, a cutoff means, and a cross leak determination means. The voltage measurement means measures the voltage of a plurality of unit cells that generate electricity through an electrochemical reaction between a fuel gas supplied to an anode and an oxidizer gas supplied to an oxidizer electrode at predetermined units. The first stopping means stops the supply of fuel gas. The second stopping means stops the supply of oxidizer gas. The cutoff means cuts off the transfer of charge between the anode and the oxidizer electrode. The cross leak determination means determines whether a voltage difference between the voltages measured at predetermined units by the voltage measurement means after stopping the supply to the anode and the oxidizer electrode and cutting off the transfer of charge is equal to or greater than a predetermined value, thereby determining whether a cross leak has occurred.

[0004] Japanese Patent Laid-Open No. 9-27336 Japanese Patent Laid-Open No. 2005-63724

[0005] The present disclosure provides an advantageous technique for identifying an abnormal fuel cell stack in a fuel cell system including multiple fuel cell stacks.

[0006] The present disclosure provides a fuel cell system comprising: a plurality of fuel cell stacks electrically connected in series; a measuring device for measuring the voltage of the plurality of fuel cell stacks; a first supplier for supplying a fuel gas containing hydrogen to a plurality of fuel electrodes of the plurality of fuel cell stacks; a second supplier for supplying an oxidizer gas containing oxygen to a plurality of oxidizer electrodes of the plurality of fuel cell stacks; and a controller, wherein the controller causes the measuring device to measure the voltage generated in the plurality of fuel cell stacks under a first condition or a second condition, wherein under the first condition, the plurality of fuel electrodes of the plurality of fuel cell stacks continue to receive the supply of the fuel gas, and the plurality of oxidizer electrodes of the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas is supplied for a predetermined period and then the supply of the oxidizer gas is stopped, and under the second condition, the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas and the fuel gas are supplied for a predetermined period and then the supply of the oxidizer gas and the fuel gas is stopped.

[0007] The technology of the present disclosure is advantageous from the perspective of identifying an abnormal fuel cell stack in a fuel cell system having multiple fuel cell stacks.

[0008] FIG. 1 is a diagram showing a schematic configuration of a fuel cell system according to a first embodiment; FIG. 2 is a flowchart showing an example of a method for inspecting the fuel cell system shown in FIG. 1; FIG. 3 is a flowchart showing another example of a method for inspecting the fuel cell system shown in FIG. 1; and FIG. 4 is a graph showing an example of a change over time in voltages generated in a plurality of fuel cell stacks.

[0009] (Knowledge, etc., that Forms the Basis of the Present Disclosure) At the time the inventors arrived at the present disclosure, it was common practice to measure the voltage of each fuel cell stack in a fuel cell system to determine an abnormality in the fuel cell stack. To increase the power generation output of a fuel cell system, multiple fuel cell stacks may be electrically connected in series. In this case, if an abnormality occurs in one of the multiple fuel cell stacks, it is considered important to identify the abnormal fuel cell stack from among the multiple fuel cell stacks. According to the technology described in Patent Document 1, a correspondence relationship between changes over time in the supply amount of oxygen-containing gas and corresponding changes over time in the voltage generated in the stack is recorded. Therefore, it is understood that in order to identify a stack from among multiple stacks in which an abnormality such as cross leakage has occurred, it is necessary to acquire changes over time in voltage for each stack. In the technology described in Patent Document 2, a voltage measurement means measures the voltage of multiple unit cells in predetermined units, for example, measuring the voltage for each sub-stack.

[0010] In a fuel cell system, measuring the voltage of each fuel cell stack to determine whether there is an abnormality in the fuel cell stack is cumbersome and is hardly advantageous from the perspective of identifying an abnormal fuel cell stack from among multiple fuel cell stacks.

[0011] Therefore, the present disclosure provides a fuel cell system that is advantageous from the viewpoint of identifying an abnormal fuel cell stack in a fuel cell system including a plurality of fuel cell stacks.

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of already well-known matters or redundant description of substantially the same configuration may be omitted.

[0013] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0014] First Embodiment Hereinafter, a first embodiment will be described with reference to FIGS. 1 to 3. FIG.

[0015] [1-1. Configuration] FIG. 1 is a diagram schematically illustrating the configuration of a fuel cell system according to a first embodiment. As shown in FIG. 1, the fuel cell system 1a includes a plurality of fuel cell stacks 10, a measuring device 20, a first supplier 30, a second supplier 40, and a controller 50. The plurality of fuel cell stacks 10 are electrically connected in series. The fuel cell system 1a includes, for example, four fuel cell stacks 10a, 10b, 10c, and 10d as the plurality of fuel cell stacks 10. Each of the plurality of fuel cell stacks 10 includes an anode 11 and an oxidizer electrode 12. In the fuel cell stack 10, power is generated by an electrochemical reaction between a fuel gas and an oxidizer gas. The power generated in the plurality of fuel cell stacks 10 is supplied to an external load. The fuel cell stack 10 is not limited to a stack of a specific type of fuel cell. The fuel cell stack 10 may be, for example, a stack of a polymer electrolyte fuel cell, a solid oxide fuel cell, a phosphoric acid fuel cell, or a molten carbonate fuel cell.

[0016] The measuring device 20 measures the voltage of a plurality of fuel cell stacks 10 electrically connected in series.

[0017] 1, the fuel cell system 1a includes an inverter 25. The inverter 25 converts DC power obtained by power generation in the plurality of fuel cell stacks 10 into AC power and outputs the AC power to the outside of the fuel cell system 1a.

[0018] The first supplier 30 supplies fuel gas containing hydrogen to the multiple anodes 11 of the multiple fuel cell stacks 10. As shown in FIG. 1 , the first supplier 30 includes, for example, a pressure reducing valve 31 and a governor 32. The first supplier 30 is connected to, for example, a fuel gas source (not shown) that stores high-pressure fuel gas. The fuel gas supplied from the fuel gas source passes through the pressure reducing valve 31 and the governor 32, thereby adjusting the pressure of the fuel gas to a pressure suitable for supply to the anodes 11 of the fuel cell stacks 10. The fuel cell system 1a includes, for example, a pressure gauge 35. The pressure gauge 35 is disposed in the fuel gas flow path near the outlet of the governor 32. The pressure gauge 35 measures the pressure of the fuel gas that has passed through the governor 32, and the pressure of the fuel gas at the outlet of the governor 32 is adjusted to a desired range based on the pressure value measured by the pressure gauge 35.

[0019] The second supplier 40 supplies an oxidant gas containing oxygen to the oxidant electrodes 12 of the fuel cell stacks 10. The second supplier 40 includes, for example, a blower. The oxidant gas is, for example, air.

[0020] As shown in FIG. 1 , the fuel cell system 1 a further includes, for example, a plurality of on-off valves 15. The plurality of on-off valves 15 are respectively arranged corresponding to the plurality of oxidizer electrodes 12 of the plurality of fuel cell stacks 10. Each of the plurality of on-off valves 15 is arranged, for example, in at least one selected from the group consisting of a first portion 45 a and a second portion 45 b in the oxidizer gas flow path. The first portion 45 a is a portion upstream of the oxidizer gas inlet of the oxidizer electrode 12 in the oxidizer gas flow. The second portion 45 b is a portion downstream of the oxidizer gas outlet of the oxidizer electrode 12 in the oxidizer gas flow. For each of the plurality of fuel cell stacks 10, the on-off valve 15 may be arranged in either the first portion 45 a or the second portion 45 b, or in both the first portion 45 a and the second portion 45 b. The on-off valve 15 adjusts the supply and stop of the oxidizer gas to the plurality of oxidizer electrodes 12 of the plurality of fuel cell stacks 10.

[0021] As shown in FIG. 1, the fuel cell system 1 a includes, for example, a heat exchanger 61 , a gas-liquid separator 62 , a pump 63 , a valve 64 , and a ventilation fan 70 .

[0022] The heat exchanger 61 exchanges heat between the anode off-gas discharged from the fuel electrode 11 of the fuel cell stack 10 and a heat medium. The anode off-gas contains, for example, unreacted hydrogen and water vapor. The heat medium is, for example, water. Due to the heat exchange between the anode off-gas and the heat medium in the heat exchanger 61, the water vapor contained in the anode off-gas condenses to produce liquid water.

[0023] The gas-liquid separator 62 separates the liquid water and the hydrogen-containing gas contained in the anode off-gas that has passed through the heat exchanger 61. The liquid water separated by the gas-liquid separator 62 is stored, for example, in a predetermined tank (not shown) and is used to cool the fuel cell stack 10, humidify the fuel gas, and humidify the oxidant gas.

[0024] The gas separated in the gas-liquid separator 62 is sent by, for example, a pump 63 , merges with the flow of fuel gas that has passed through the governor 32 , and is supplied toward the fuel electrode 11 .

[0025] The valve 64 is a valve for purging the gas separated in the gas-liquid separator 62. The gas that passes through the valve 64 is mixed with the cathode off-gas discharged from the oxidizer electrode 12 of the fuel cell stack 10, and is discharged to the outside of the fuel cell system 1a.

[0026] The ventilation fan 70 exhausts the cathode off-gas to the outside of the fuel cell system 1 a. The gas that has passed through the valve 64 is mixed with, for example, the cathode off-gas exhausted from the oxidizer electrode 12, and is then exhausted to the outside of the fuel cell system 1 a by the ventilation fan 70.

[0027] For example, the controller 50 causes the measuring device 20 to measure the voltages generated in the plurality of fuel cell stacks 10 under predetermined conditions in order to test the plurality of fuel cell stacks 10 .

[0028] The controller 50 includes, for example, a microcomputer, a memory, and an input / output interface. A control program for operating or inspecting the fuel cell system 1a is stored in the memory. The control program is read and executed by the microcomputer. In this way, the controller 50 controls devices such as pumps, valves, blowers, fans, and voltage measuring devices. The controller 50 may be connected to an operation panel (not shown) for receiving input from a user and displaying various information.

[0029] [1-2. Operation] The operation of the fuel cell system 1a configured as above will be described below.

[0030] FIG. 2A is a flowchart showing an example of a method for inspecting the fuel cell system 1a. FIG. 2B is a flowchart showing another example of a method for inspecting the fuel cell system 1a. The controller 50 executes a control program for inspecting the fuel cell system 1a when a predetermined condition is met. This control program is a control program for the method for inspecting the fuel cell system 1a shown in FIG. 2A or 2B. An example of the predetermined condition is detection of an error related to the fuel cell stack 10. For example, the predetermined condition may be met when a decrease in power generation output during normal operation of the fuel cell system 1a, a temperature of the fuel cell stack 10 exceeding a predetermined value, or a voltage of the fuel cell stack 10 exceeding a predetermined value is detected. The method for inspecting the fuel cell system 1a shown in FIG. 2A or 2B may be performed as part of maintenance of the fuel cell system 1a. For example, the control program for inspecting the fuel cell system 1a may be executed by a maintenance person inputting a predetermined command.

[0031] As shown in FIG. 2A , when inspection of the fuel cell system 1a is started due to the satisfaction of a predetermined condition, etc., in step S101, the supply of fuel gas to the multiple anodes 11 of the multiple fuel cell stacks 10 is started. Alternatively, the supply of fuel gas to the multiple anodes 11 of the multiple fuel cell stacks 10 is continued. In this case, fuel gas containing a predetermined concentration of hydrogen is supplied to all the anodes 11 of the fuel cell stacks 10a, 10b, 10c, and 10d. The supply of fuel gas to the multiple anodes 11 of the multiple fuel cell stacks 10 continues, for example, until the inspection process shown in FIG. 2A is completed. As shown in FIG. 2B , the supply of fuel gas to the multiple anodes 11 of the multiple fuel cell stacks 10 may be stopped during the inspection process.

[0032] Next, in step S102, the supply of oxidant gas to the plurality of fuel cell stacks 10 is stopped. For example, the on-off valves 15 corresponding to the fuel cell stacks 10a, 10b, 10c, and 10d are closed to stop the supply of oxidant gas to the plurality of fuel cell stacks 10. In testing the fuel cell system 1a, the controller 50 causes the measuring device 20 to measure the voltages V1 generated in the plurality of fuel cell stacks 10. In step S103, the processing of step S103 is repeated until it is determined that the voltage V1 is equal to or less than a predetermined threshold value V2.

[0033] The threshold value V2 is, for example, a threshold value corresponding to the plurality of fuel cell stacks 10 hardly generating power. In step S102, the supply of oxidant gas to the plurality of fuel cell stacks 10 is stopped, and therefore the oxidant gas decreases at the oxidant electrodes 12 due to the electrochemical reaction between the fuel gas and the oxidant gas in the plurality of fuel cell stacks 10. When the oxidant gas runs out at the plurality of oxidant electrodes 12 of the plurality of fuel cell stacks 10, the voltage of the plurality of fuel cell stacks 10 becomes nearly zero, the voltage V1 becomes equal to or less than the predetermined threshold value V2, and the condition of step S103 is satisfied.

[0034] Next, the oxidizer electrodes 12 of the fuel cell stacks 10 are sequentially supplied with oxidizer gas for a predetermined period of time and then the supply of oxidizer gas is stopped (see steps S104 to S115). For example, this process is performed in the order of fuel cell stack 10a, fuel cell stack 10b, fuel cell stack 10c, and fuel cell stack 10d. In this process, the predetermined period for supplying oxidizer gas is, for example, 30 seconds to 1 minute. When this process is performed for fuel cell stack 10a (see steps S104 to S105), the on-off valve 15 corresponding to fuel cell stack 10a is opened for a predetermined period of time and then closed. Thereafter, if it is determined that the voltage V1 is equal to or lower than a predetermined threshold V3, the process moves to fuel cell stack 10b. The threshold V3 is, for example, a threshold corresponding to the fuel cell stacks 10 generating almost no power. The threshold V3 may be the same as or different from the threshold V2. When this process is performed on fuel cell stack 10b, fuel cell stack 10c, or fuel cell stack 10d, the opening and closing of the corresponding on-off valve 15 is similarly controlled, and a determination is made as to whether voltage V1 is equal to or lower than a predetermined threshold value V3.

[0035] When the above process is performed on the fuel cell stack 10a, the supply of oxidant gas to the oxidant electrodes 12 of the fuel cell stacks 10b, 10c, and 10d is stopped. When the above process is performed on the fuel cell stack 10b, the supply of oxidant gas to the oxidant electrodes 12 of the fuel cell stacks 10a, 10c, and 10d is stopped. When the above process is performed on the fuel cell stack 10d, the supply of oxidant gas to the oxidant electrodes 12 of the fuel cell stacks 10a, 10b, and 10d is stopped.

[0036] For example, when the above process is performed on the fuel cell stack 10a, oxidant gas is supplied to the oxidant electrode 12 of the fuel cell stack 10a for a predetermined period of time (see steps S104 and S105). As a result, a voltage is generated due to an electrochemical reaction between the fuel gas and the oxidant gas in the fuel cell stack 10a. Because no oxidant gas is supplied to the other fuel cell stacks 10b, 10c, and 10d, the voltage V1 measured by the measuring device 20 is approximately equal to the voltage generated in the fuel cell stack 10a. When the supply of oxidant gas is stopped, the oxidant gas decreases at the oxidant electrode 12 due to the electrochemical reaction between the fuel gas and the oxidant gas in the fuel cell stack 10a. When the oxidant gas runs out at the oxidant electrode 12 of the fuel cell stack 10a, the voltage generated in the fuel cell stack 10a becomes approximately zero. The voltage V1 measured by the measuring device 20 gradually decreases over time from the stop of the supply of oxidant gas to the oxidant electrode 12 of the fuel cell stack 10a to the start of the supply of oxidant gas to the oxidant electrode 12 of the fuel cell stack 10b. If some abnormality, such as cross leakage, occurs in the fuel cell stack 10a, the change in voltage V1 over time during this period may differ from the change in voltage V1 over time when the fuel cell stack 10a is normal. For example, if an abnormality occurs in the fuel cell stack 10a, the voltage V1 decreases more rapidly over a shorter period of time and approaches zero. Based on this difference in the change in voltage V1 over time, an abnormal fuel cell stack 10a can be identified from among multiple fuel cell stacks 10 by the voltage V1 measured by the measuring device 20.

[0037] 3 is a graph showing an example of the change over time in voltage V1 generated in a plurality of fuel cell stacks 10 during the processing periods from step S104 to step S115. In FIG. 3, periods Pa, Pb, Pc, and Pd indicate periods during which oxidant gas is supplied to the oxidant electrodes 12 of fuel cell stacks 10a, 10b, 10c, and 10d, respectively. As shown in FIG. 3, when oxidant gas is supplied to the oxidant electrode 12 of fuel cell stack 10c, voltage V1 decreases rapidly in a short period of time and approaches zero compared to when oxidant gas is supplied to the oxidant electrodes 12 of the other fuel cell stacks 10. This suggests that some kind of abnormality, such as cross leakage, is occurring in fuel cell stack 10c.

[0038] If an abnormal fuel cell stack 10 is identified through the above inspection, then in step S116, for example, a message informing the operator of the abnormal fuel cell stack 10 is sent to an operation panel or an information terminal of a maintenance personnel, and the series of processes ends. This prompts the operator to replace the abnormal fuel cell stack 10, for example.

[0039] 2B , when an inspection of the fuel cell system 1a is started due to the satisfaction of a predetermined condition, the process of step S301 is repeated until it is determined in step S301 that the voltage V1 is equal to or less than a predetermined threshold value V2. For example, when the inspection of the fuel cell system 1a is started, no oxidant gas or fuel gas is supplied to the multiple fuel cell stacks 10.

[0040] Next, the plurality of fuel cell stacks 10 are sequentially subjected to a process in which oxidant gas and fuel gas are supplied for a predetermined period of time and then the supply of oxidant gas and fuel gas is stopped (see steps S302 to S312). For example, this process is performed in the order of fuel cell stack 10a, fuel cell stack 10b, fuel cell stack 10c, and fuel cell stack 10d. In this process, the predetermined period for supplying oxidant gas and fuel gas is, for example, 30 seconds to 1 minute. When this process is performed for fuel cell stack 10a (see steps S302 to S303), the on-off valve 15 corresponding to fuel cell stack 10a is opened for the predetermined period of time and then closed. In addition, the first supplier 30 is controlled so that fuel gas is supplied to fuel cell stack 10a for the predetermined period of time. Thereafter, when it is determined that voltage V1 is equal to or lower than predetermined threshold value V3, the process shifts to fuel cell stack 10b. When this process is performed on fuel cell stack 10b, fuel cell stack 10c, or fuel cell stack 10d, the corresponding on-off valve 15 is similarly opened and closed and the first supplier 30 is controlled, and a determination is made as to whether the voltage V1 is equal to or lower than a predetermined threshold value V3.

[0041] For example, when the above process is performed on the fuel cell stack 10a, oxidant gas and fuel gas are supplied to the fuel cell stack 10a for a predetermined period of time (see steps S302 and S303). Therefore, a voltage is generated due to an electrochemical reaction between the fuel gas and oxidant gas in the fuel cell stack 10a. Because no oxidant gas is supplied to the other fuel cell stacks 10b, 10c, and 10d, the voltage V1 measured by the measuring device 20 is substantially equal to the voltage generated in the fuel cell stack 10a. When the supply of oxidant gas and fuel gas is stopped, the electrochemical reaction between the fuel gas and oxidant gas in the fuel cell stack 10a decreases the oxidant gas at the oxidant electrode 12 and the fuel gas at the fuel electrode 11. When the oxidant gas runs out at the oxidant electrode 12 of the fuel cell stack 10a or when the fuel gas runs out at the fuel electrode 11 of the fuel cell stack 10a, the voltage generated in the fuel cell stack 10a becomes substantially zero. The voltage V1 measured by the measuring device 20 gradually decreases over time from the stop of the supply of oxidant gas and fuel gas to the fuel cell stack 10a to the start of the supply of oxidant gas and fuel gas to the fuel cell stack 10b. If some abnormality, such as a cross leak, occurs in the fuel cell stack 10a, the change in voltage V1 over time during this period may differ from the change in voltage V1 over time when the fuel cell stack 10a is normal. For example, if an abnormality occurs in the fuel cell stack 10a, the voltage V1 decreases more rapidly in a shorter period of time and approaches zero. Based on this difference in the change in voltage V1 over time, an abnormal fuel cell stack 10a can be identified from among multiple fuel cell stacks 10 by the voltage V1 measured by the measuring device 20.

[0042] If an abnormal fuel cell stack 10 is identified through the above inspection, then in step S314, for example, a message informing the operator of the abnormal fuel cell stack 10 is sent to an operation panel or an information terminal of a maintenance personnel, and the series of processes ends. This prompts the operator to replace the abnormal fuel cell stack 10, for example.

[0043] (Other Embodiments) As described above, the first embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. Furthermore, it is also possible to combine the components described in the first embodiment above to create new embodiments.

[0044] Therefore, other embodiments will be exemplified below.

[0045] The switching of the oxidizer electrode 12 to which the oxidizer gas is supplied for a predetermined period and then the supply of the oxidizer gas is stopped is not limited to the switching based on whether or not the voltage V1 is equal to or lower than the predetermined threshold value V3. The switching of the oxidizer electrode 12 to which the oxidizer gas is supplied for a predetermined period and then the supply of the oxidizer gas is stopped may be performed based on the elapse of a predetermined period (e.g., 1 to 5 minutes) since the supply of the oxidizer gas was stopped.

[0046] The process in step S116 is not limited to sending a message informing of an abnormality in the fuel cell stack 10. For example, in step S113, instead of sending a message, the change in voltage V1 over time may be output to an operation panel or an information terminal.

[0047] The fuel gas used in the fuel cell system 1a is not limited to a specific gas as long as it contains hydrogen. The fuel gas may be a hydrogen-containing gas obtained by reforming a hydrocarbon gas, or may be a hydrogen-containing gas obtained by water electrolysis. When the fuel gas is obtained by reforming a hydrocarbon gas, the fuel cell system 1a may be equipped with a reformer for reforming the hydrocarbon gas.

[0048] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0049] (Technology 1) A fuel cell system comprising: a plurality of fuel cell stacks electrically connected in series; a measuring device that measures the voltage of the plurality of fuel cell stacks; a first supplier that supplies a fuel gas containing hydrogen to a plurality of fuel electrodes of the plurality of fuel cell stacks; a second supplier that supplies an oxidizer gas containing oxygen to a plurality of oxidizer electrodes of the plurality of fuel cell stacks; and a controller, wherein the controller causes the measuring device to measure the voltage generated in the plurality of fuel cell stacks under a first condition or a second condition, wherein under the first condition, the plurality of fuel electrodes of the plurality of fuel cell stacks continue to receive the supply of the fuel gas, and the plurality of oxidizer electrodes of the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas is supplied for a predetermined period and then the supply of the oxidizer gas is stopped, and under the second condition, the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas and the fuel gas are supplied for a predetermined period and then the supply of the oxidizer gas and the fuel gas is stopped.

[0050] According to Technology 1, it is possible to identify an abnormal fuel cell stack by measuring the voltages of multiple fuel cell stacks electrically connected in series, without measuring the voltage of each of the multiple fuel cell stacks. Therefore, Technology 1 is advantageous from the perspective of identifying an abnormal fuel cell stack in a fuel cell system having multiple fuel cell stacks.

[0051] (Technology 2) The fuel cell system according to Technology 1, further comprising a plurality of on-off valves arranged corresponding to each of the plurality of oxidizer electrodes of the plurality of fuel cell stacks, wherein each of the plurality of on-off valves is arranged in at least one selected from the group consisting of a first portion of the flow of the oxidizer gas upstream of the oxidizer gas inlet at the oxidizer electrode and a second portion of the flow of the oxidizer gas downstream of the oxidizer gas outlet at the oxidizer electrode.

[0052] According to Technique 2, the supply of oxidant gas to each of the oxidant electrodes of the fuel cell stacks can be adjusted by the multiple on-off valves, and for example, the number of second supply devices can be made smaller than the number of fuel cell stacks, making it easier to miniaturize the fuel cell system even if it includes multiple fuel cell stacks.

[0053] (Technology 3) A method for inspecting a fuel cell system, comprising measuring voltages generated in a plurality of fuel cell stacks under a first condition or a second condition, wherein under the first condition, a plurality of fuel electrodes of the plurality of fuel cell stacks continue to receive a supply of fuel gas, and a plurality of oxidizer electrodes of the plurality of fuel cell stacks are sequentially subjected to a process in which an oxidizer gas is supplied for a predetermined period of time and then the supply of the oxidizer gas is stopped, and under the second condition, the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas and the fuel gas are supplied for a predetermined period of time and then the supply of the oxidizer gas and the fuel gas is stopped.

[0054] According to Technique 3, it is possible to identify an abnormal fuel cell stack by measuring the voltages of multiple fuel cell stacks electrically connected in series, without measuring the voltage of each of the multiple fuel cell stacks. Therefore, Technique 3 is advantageous from the perspective of identifying an abnormal fuel cell stack in a fuel cell system having multiple fuel cell stacks.

[0055] The techniques of the present disclosure are useful in fuel cell systems.

Claims

1. A fuel cell system comprising: a plurality of fuel cell stacks electrically connected in series; a measuring device for measuring the voltage of the plurality of fuel cell stacks; a first supplier for supplying a fuel gas containing hydrogen to a plurality of fuel electrodes of the plurality of fuel cell stacks; a second supplier for supplying an oxidizer gas containing oxygen to a plurality of oxidizer electrodes of the plurality of fuel cell stacks; and a controller, wherein the controller causes the measuring device to measure the voltage generated in the plurality of fuel cell stacks under a first condition or a second condition, wherein under the first condition, the plurality of fuel electrodes of the plurality of fuel cell stacks continue to receive the supply of the fuel gas, and the plurality of oxidizer electrodes of the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas is supplied for a predetermined period and then the supply of the oxidizer gas is stopped, and under the second condition, the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas and the fuel gas are supplied for a predetermined period and then the supply of the oxidizer gas and the fuel gas is stopped.

2. The fuel cell system according to claim 1, further comprising a plurality of on-off valves arranged corresponding to each of the plurality of oxidizer electrodes of the plurality of fuel cell stacks, each of the plurality of on-off valves being arranged in at least one selected from the group consisting of a first portion of the flow of the oxidizer gas upstream of the oxidizer gas inlet at the oxidizer electrode and a second portion of the flow of the oxidizer gas downstream of the oxidizer gas outlet at the oxidizer electrode.

3. A method for inspecting a fuel cell system, comprising measuring voltages generated in a plurality of fuel cell stacks under a first condition or a second condition, wherein under the first condition, a plurality of fuel electrodes of the plurality of fuel cell stacks continue to receive a supply of fuel gas, and a plurality of oxidizer electrodes of the plurality of fuel cell stacks are sequentially subjected to a process in which an oxidizer gas is supplied for a predetermined period of time and then the supply of the oxidizer gas is stopped, and under the second condition, the plurality of fuel cell stacks are sequentially subjected to a process in which the oxidizer gas and the fuel gas are supplied for a predetermined period of time and then the supply of the oxidizer gas and the fuel gas is stopped.

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