Fuel cell system and method for determining the reusability of a fuel cell stack

Abstract

Fuel cell system with a fuel cell stack arrangement, wherein the fuel cell stack arrangement comprises a fuel cell stack and a data storage device configured to store a start-up history of the fuel cell stack; wherein the data storage includes a detector configured to detect the presence or absence of a connection to at least one selected from the group consisting of an external power source and an external communication device; the data storage starts when a voltage of the fuel cell stack is a predetermined threshold or higher; wherein, at the time of data storage startup, the data storage records the startup as a normal startup of the fuel cell stack when the detector detects the presence of the connection; and where, at the time of data storage startup, the data storage records the startup as an abnormal startup of the fuel cell stack if the detector detects the lack of connection.

Description

TECHNICAL AREA

[0001] The invention relates to a fuel cell system and a method for determining the reusability of a fuel cell stack. BACKGROUND

[0002] A fuel cell (FC) is a power generation device that produces electrical energy through an electrochemical reaction between hydrogen (H₂), which serves as the fuel gas, and oxygen (O₂), which serves as the oxidizer gas, in a fuel cell stack (hereinafter referred to simply as a "stack") consisting of stacked unit fuel cells (hereinafter referred to simply as "cells"). Hereinafter, the fuel gas and oxidizer gas can be collectively and simply referred to as the "reaction gas" or "gas".

[0003] In general, unit fuel cells consist of a membrane electrode assembly (MEA) and, if required, two separators that sandwich the membrane electrode assembly.

[0004] The membrane electrode arrangement has such a structure that a catalyst layer and a gas diffusion layer are placed in that order on both surfaces of a solid polymer electrolyte membrane with proton-(H) + )-conductivity (hereinafter referred to simply as the "electrolyte membrane") are formed.

[0005] In general, the separators have a structure such that a groove forms on a surface in contact with the gas diffusion layer, serving as a pathway for the reaction gas flow. The separators act as collectors for the generated flow.

[0006] In the fuel cell's anode, hydrogen supplied from the flow path and the gas diffusion layer is protonated by the catalytic activity of the catalyst layer. The protonated hydrogen then passes through the electrolyte membrane to the cathode. Simultaneously, an electron is generated, which travels through an external circuit, performs work, and then travels to the cathode. The oxygen supplied to the cathode reacts with the proton and the electron at the cathode, producing water.

[0007] The generated water supplies the electrolyte membrane with the necessary moisture. The excess water permeates the gas diffusion layer and is then drained to the outside.

[0008] When selling the stack, the reuse value of the stack (especially the used stack) depends essentially on the remaining service life of the stack.

[0009] For example, patent literature 1 discloses such a technique for evaluating the lifetime of a fuel cell, wherein a fuel cell contains a storage medium for storing its own operating history data, stores the operating history data in the storage medium and diagnoses the lifetime of the fuel cell based on the stored operating history data.

[0010] Patent literature 2 discloses a device for determining the lifetime of a fuel cell, with which the lifetime of a standard fuel cell can be determined in a suitable manner.

[0011] Patent literature 3 discloses an electric vehicle that can easily obtain a determination result as to whether a collected battery pack is reusable or not. Patent Literature 1: Japanese Patent Application JP 2007-128769A Patent Literature 2: Japanese Patent Application JP 2008-097836A Patent Literature 3: Japanese Patent Application JP 2018-078025A

[0012] To accurately assess the remaining lifespan of a stack, it is necessary to precisely track the stack's history. To accurately track this history, the stack must be in one of the following states: the state in which the stack remains mounted on a fuel cell vehicle (hereinafter referred to as the "vehicle"); the state in which the stack, even if removed from the vehicle, is disassembled using predetermined correct procedures; and the state in which the stack is stored using a predetermined storage procedure.

[0013] The lifetime diagnosis disclosed in patent literature 1 is directed towards the stack mounted on a vehicle.

[0014] Accordingly, the prior art only records the operating history of the fuel cell stack mounted on the vehicle. It also does not record whether the stack was properly removed from the vehicle or whether it generated electricity after removal. Furthermore, the abnormal potential phenomenon specific to fuel cells is not detected in the conventional prior art. There is also no data storage system in the prior art to detect the abnormal potential phenomenon that occurs after the fuel cell is removed from the vehicle.

[0015] The stack is expected to be removed from the fuel cell vehicle when a user uses the vehicle or when the stack is sold.

[0016] If the stack is removed from the vehicle using unspecified or incorrect procedures, or if the removed stack is made to generate electricity, the stack will be subjected to an abnormally high voltage, resulting in deterioration of the catalyst and a negative impact on the stack's lifespan.

[0017] Even when the stack is used correctly, it is inevitable that it will be subjected to high stress, and the degradation of the catalyst will progress accordingly. However, since the stack is monitored by the fuel cell system in this case, its history can be precisely tracked, and the reliability of the remaining stack life diagnosis is ensured. In contrast, if the stack is used improperly, it is not monitored by the fuel cell system. Consequently, its history cannot be accurately traced, and the reliability of the remaining stack life diagnosis decreases. SUMMARY

[0018] The disclosed embodiments were achieved in light of the circumstances described above. One objective of the disclosed embodiments is to provide a fuel cell system whose stack can be easily inspected to determine whether it has value as a stack with a remaining service life when sold on the reuse market. Another objective of the disclosed embodiments is to provide a method for determining the reusability of a fuel cell stack.

[0019] In a first embodiment, a fuel cell system is provided which includes a fuel cell stack arrangement, wherein the fuel cell stack arrangement comprises a fuel cell stack and a data storage device configured to store a start-up history of the fuel cell stack; wherein the data storage includes a detector configured to detect the presence or absence of a connection to at least one selected from the group consisting of an external power source and an external communication device; the data storage starts when a voltage of the fuel cell stack is a predetermined threshold or higher; wherein, at the time of data storage startup, the data storage records the startup as a normal startup of the fuel cell stack when the detector detects the presence of the connection; and where, at the time of data storage startup, the data storage records the startup as an abnormal startup of the fuel cell stack if the detector detects the lack of connection.

[0020] The threshold can be a predetermined voltage at which a catalyst in the fuel cell stack deteriorates.

[0021] The data storage system can start using the fuel cell stack as a power source.

[0022] The fuel cell stack arrangement can further include an internal power source, and the data storage can start using the internal power source as a power source.

[0023] In a further embodiment, a method for determining the reusability of a fuel cell stack is specified, where, for the fuel cell system described above, the fuel cell stack of the fuel cell system is determined to be non-reusable if at least one abnormal start-up data record is included in the stored start-up history.

[0024] According to the disclosed embodiments, such a fuel cell system can be provided whose stack can be easily checked and it can be determined whether it has value as a stack with a remaining lifetime or not when it is distributed on the reuse market. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The attached drawings show Fig. 1 a view of an example of the construction of the fuel cell stack arrangement according to the disclosed embodiments, and Fig. 2 a flowchart of an example of the method for determining the reusability of the fuel cell stack according to the disclosed embodiments. DETAILED DESCRIPTION

[0026] The fuel cell system of the disclosed embodiments is a fuel cell system comprising a fuel cell stack arrangement, wherein the fuel cell stack arrangement comprises a fuel cell stack and a data storage device configured to store a start-up history of the fuel cell stack; wherein the data storage includes a detector configured to detect the presence or absence of a connection to at least one selected from the group consisting of an external power source and an external communication device; the data storage starts when a voltage of the fuel cell stack is a predetermined threshold or higher; wherein, at the time of data storage startup, the data storage records the startup as a normal startup of the fuel cell stack when the detector detects the presence of the connection; and where, at the time of data storage startup, the data storage records the startup as an abnormal startup of the fuel cell stack if the detector detects the lack of connection.

[0027] When the stack is mounted on a vehicle, it is generally under the control of the fuel cell system. Accordingly, there is no unexpected gas entry / exit, and no abnormal potential is generated in the anode. When the stack is removed from the vehicle using predetermined, correct procedures, no abnormal potential is generated in the anode.

[0028] If the stack is removed from the vehicle using improper procedures, or if the removed stack is subjected to generating electricity, an abnormal voltage will be generated in the stack due to an abnormal potential at the anode. This leads to catalyst degradation and a reduction in stack performance. Consequently, the remaining service life of the stack cannot be accurately estimated. Therefore, to increase the reliability of determining the reusability of the removed stack, it must be ensured that the stack has been handled according to a predetermined, correct procedure. However, current state of the art lacks a method for recording the stack's history both at the time of removal from the vehicle and after removal.

[0029] The abnormal condition of the stack could be, for example, the following: the condition in which a stress is generated in the stack that is not mounted in the vehicle, the condition in which the stack is not removed from the vehicle by predetermined correct procedures, and the condition in which the stack is not stored by a predetermined correct procedure.

[0030] In the event that a voltage is generated in the stack that is not mounted in the vehicle, the following possibility exists: Since the stack is not under the control of the fuel cell system, an abnormal potential was generated in the anode due to an unexpected gas entry / exit, and the catalyst deteriorated.

[0031] If the stack is not removed from the vehicle using predetermined correct procedures, there is a possibility that the unexpected gas entry / exit will create an abnormal potential in the anode and the catalyst will deteriorate.

[0032] Furthermore, if the stack is stored without hermetically sealing the stack distributor, there is a possibility that unexpected gas ingress / egress will create an abnormal potential in the anode and damage the catalyst.

[0033] If the stack is caused to generate its own electricity, it is not possible to track the history of how the stack was started and operated.

[0034] For the reasons mentioned above, it can be said that under normal conditions, a voltage is only generated when the stack is installed in the vehicle. Furthermore, as long as the stack is installed in the vehicle, there is always a connection to a predetermined external power source (e.g., a 12V power source), an external communication device, etc. Accordingly, the voltage of the stack can be determined as normal or abnormal depending on the presence or absence of a connection to a predetermined external power source, an external communication device, etc.

[0035] According to the disclosed embodiments, the data storage device, which operates without an external power supply, is integrated into the fuel cell stack assembly. The data storage device detects abnormal voltages in the stack and records the startup history, including time and date. Accordingly, the presence or absence of abnormal voltage generation in the stack can be recorded both at the time of removal from the vehicle and after removal.

[0036] Specifically, if an abnormal voltage is generated in the stack and the stack is not connected to the predetermined external power source, external communication device, etc., the data storage system considers this an abnormal case and sets a flag. Accordingly, the stack can be easily checked to determine whether it has value as a stack with remaining lifespan (i.e., is a reusable stack) when it is placed on the reuse market.

[0037] Examples of predetermined correct procedures for dismantling the stack from the vehicle include, but are not limited to, the following procedures (1) to (4): (1) After the vehicle's ignition (IG) has been switched off, the stack is left to stand for a predetermined time (to consume the oxygen in the cathode and reduce the stack voltage). (2) The hydrogen remaining in the anode is removed from the anode, and the reaction gas in the anode and the cathode is replaced by nitrogen. (3) Air is introduced into the anode and cathode at a specific time with a predetermined flow rate (an abnormal voltage is not generated in the stack as long as fuel gas is reintroduced into the anode at that point). (4) The pipeline is detached from the stack, the stack's distributor is closed, and the stack is removed from the vehicle.

[0038] The following storage methods (A) and (B) are possible as predetermined correct procedures for storing the stack, but are not limited to them: (A) The distributor of the stack is covered and stored in such a way as to prevent the ingress of foreign substances and toxic gas (especially sulfide-based gas). (B) The stack is stored in such a way that it cannot generate electricity itself.

[0039] Fig. Figure 1 is a view of an example of the construction of the fuel cell stack arrangement according to the disclosed embodiments.

[0040] One in Fig. The fuel cell stack arrangement 100 shown comprises a fuel cell stack 11 and a data storage device 12. The data storage device 12 is configured to be connected to an external power source, etc.

[0041] The fuel cell system of the disclosed embodiments comprises at least the fuel cell stack arrangement.

[0042] The fuel cell stack assembly includes the fuel cell stack and the data storage unit, which is configured to store the startup history of the fuel cell stack.

[0043] The fuel cell stack consists of stacked unit fuel cells.

[0044] The number of stacked unit fuel cells is not particularly limited. For example, two to several hundred unit fuel cells can be stacked, or two to 200 unit fuel cells can be stacked.

[0045] The fuel cell stack can contain an end plate at both ends in the stacking direction of each unit fuel cell.

[0046] Each standard fuel cell contains at least one membrane electrode assembly with an oxidation electrode, an electrolyte membrane, and a fuel electrode. Depending on requirements, it may include two separators that sandwich the membrane electrode assembly.

[0047] The separators can have a reaction gas flow path on a surface in contact with a gas diffusion layer. Additionally, the separators can have a coolant flow path on a surface opposite the surface in contact with the gas diffusion layer to maintain the fuel cell temperature at a constant level.

[0048] The separators can have inlet and outlet openings for the supply of reaction gas and refrigerant in the stacking direction of the unit cells.

[0049] Examples of supply openings include, but are not limited to, a fuel gas supply opening, an oxidation gas supply opening, and a refrigerant supply opening.

[0050] Examples of outlet openings include, but are not limited to, a fuel gas outlet opening, an oxidation gas outlet opening, and a refrigerant outlet opening.

[0051] The separators can be gas-tight, electrically conductive, etc. Examples of electrically conductive elements include gas-tight, dense carbon obtained by carbon compaction and a metal plate obtained by pressing. The separators can also have a current-collecting function.

[0052] The fuel cell stack can have a distributor, such as an inlet distributor that communicates between the inlet ports, and an outlet distributor that communicates between the outlet ports.

[0053] Examples of inlet distributors include, but are not limited to, an anode inlet distributor, a cathode inlet distributor, and a coolant inlet distributor.

[0054] Examples of outlet distributors include, but are not limited to, an anode outlet distributor, a cathode outlet distributor, and a refrigerant outlet distributor.

[0055] The oxidation electrode comprises an oxidation electrode catalyst layer and a gas diffusion layer.

[0056] The fuel electrode comprises a fuel electrode catalyst layer and a gas diffusion layer.

[0057] The oxidation electrode catalyst layer and the fuel electrode catalyst layer can, for example, contain a catalyst metal to accelerate an electrochemical reaction, a proton-conducting electrolyte, or electron-conducting carbon particles.

[0058] Platinum (Pt) or an alloy of Pt and another metal (e.g., Pt alloy mixed with cobalt, nickel, etc.) can be used as the catalyst metal.

[0059] The electrolyte can be a fluorinated resin or similar substance. For example, a Nafion solution can be used as a fluorinated resin.

[0060] The catalyst metal is applied to carbon particles. In each catalyst layer, the carbon particles carrying the catalyst metal (i.e., the catalyst particles) and the electrolyte can be mixed.

[0061] For example, water-repellent carbon particles, obtained by enhancing the water-repellent properties of commercially available carbon particles (carbon powder) by heating, can be used as the carbon particles for carrying the catalyst metal (i.e., carrying carbon particles).

[0062] The gas diffusion layer can be a gas-permeable, electrically conductive element or something similar.

[0063] Examples of electrically conductive elements include porous carbon materials such as carbon fabric and carbon paper, and porous metal materials such as metal fabric and metal foam, but are not limited to these.

[0064] The electrolyte membrane can be a solid polymer electrolyte membrane. Examples of solid polymer electrolyte membranes include hydrocarbon electrolyte membranes and fluorine electrolyte membranes, such as a moisture-containing, thin perfluorosulfonic acid membrane. The electrolyte membrane can, for example, be a Nafion membrane (manufactured by DuPont).

[0065] The data storage device records the startup history of the fuel cell stack.

[0066] The start-up history of the fuel cell stack can be the history of recording an increase in the voltage of the fuel cell stack to the predetermined threshold or higher.

[0067] The startup history can be an operational history.

[0068] The operating history can be the history of recording a period between an increase in the voltage of the fuel cell stack to the predetermined threshold or more and a drop in the voltage of the fuel cell stack to the predetermined voltage or less.

[0069] The data storage device can, for example, start using the electrical energy of the fuel cell stack as a power source.

[0070] The fuel cell stack assembly can further include an internal power source, and the data storage can start using this internal power source. A real-time clock, powered by the internal power source, can be attached to the fuel cell stack assembly to record the time and date as the stack's startup history.

[0071] For example, a conventionally known primary battery and a conventionally known secondary battery can be used as an internal power source, without being limited to this.

[0072] The data storage includes a detector configured to detect the presence or absence of a connection to at least one selected from the group consisting of an external power source and an external communication device.

[0073] When the stack is mounted on the vehicle, it is connected to the external power source, external communication device, etc., and the detector can recognize that the stack is connected to the external power source, the external communication device (such as a Controller Area Network (CAN)), etc. Conversely, when the stack is not mounted on the vehicle, it is not connected to the external power source, the external communication device, etc., and the detector can recognize that the stack is not connected to the external power source, the external communication device, etc.

[0074] The connection detected by the detector can be a connection to either the external power source and the external communication device, or it can be a connection to both.

[0075] The data storage system physically comprises a processing unit, such as a central processing unit (CPU), a memory device, such as read-only memory (ROM) and random-access memory (RAM), and an input / output interface. The ROM is used to store a control program, control data, etc., which is processed by the processing unit, and the RAM is primarily used as various workspaces for control processes. The data storage system can also be a control unit, such as an engine control unit (ECU).

[0076] The detector could be, for example, a conventionally known connection detection sensor.

[0077] The data storage starts when the voltage of the fuel cell stack is a predetermined threshold or higher.

[0078] For example, the data storage device can record the time and date when the voltage of the fuel cell stack rose to or above the predetermined threshold as a startup history. Additionally, the data storage device can record, for example, the time and date when the voltage of the fuel cell stack rose to or above the predetermined threshold, and the time and date when the voltage dropped to or below the predetermined voltage value, and the data storage device can record this as the operating history of the stack.

[0079] At the time of startup, the data storage records the start-up as a normal start-up of the fuel cell stack when the detector detects the presence of a connection to the external power source, external communication device, etc.

[0080] In addition, the data storage records the start-up as an abnormal start-up of the fuel cell stack if the detector detects the absence of a connection to the external power source, external communication device, etc.

[0081] The fuel cell stack can be determined to be non-reusable if the abnormal start-up is recorded in the data storage.

[0082] The predetermined voltage threshold of the fuel cell stack is not particularly limited. For example, it could be a predetermined voltage at which the catalyst in the fuel cell stack degrades. Since the catalyst degradation voltage varies depending on the type of catalyst, the voltage can be determined accordingly, depending on the catalyst used.

[0083] Fig.Figure 2 is a flowchart of an example of the method for determining the reusability of the fuel cell stack according to the disclosed embodiments. The disclosed embodiments are not limited to this typical example.

[0084] The data storage starts when the voltage of the fuel cell stack is the predetermined threshold or higher.

[0085] Next, the detector detects the presence or absence of a connection to the external power source.

[0086] Next, the data storage records the start-up as a normal start-up of the fuel cell stack when the detector detects the presence of a connection to the external power source.

[0087] In addition, the data storage records the start-up as an abnormal start-up of the fuel cell stack when the detector detects the absence of a connection to the external power source.

[0088] The fuel cell stack is classified as reusable if there is not a single abnormal start-up in the start-up history stored in the data storage.

[0089] On the other hand, the fuel cell stack is classified as non-reusable if at least one abnormal start-up data record is included in the start-up history stored in the data storage. REFERENCE MARK LIST 11 fuel cell stacks 12 Data storage devices 100 fuel cell stack arrangement

Claims

[1] Fuel cell system with a fuel cell stack arrangement, wherein the fuel cell stack arrangement comprises a fuel cell stack and a data storage device configured to store a start-up history of the fuel cell stack; wherein the data storage includes a detector configured to detect the presence or absence of a connection to at least one selected from the group consisting of an external power source and an external communication device; where the data storage starts when a voltage of the fuel cell stack is a predetermined threshold or higher; wherein, at the time of data storage startup, the data storage records the startup as a normal startup of the fuel cell stack when the detector detects the presence of the connection; and where, at the time of data storage startup, the data storage records the startup as an abnormal startup of the fuel cell stack if the detector detects the lack of connection. [2] Fuel cell system according to claim 1, wherein the threshold is a predetermined voltage at which a catalyst of the fuel cell stack deteriorates. [3] Fuel cell system according to claim 1 or 2, wherein the data storage starts using the fuel cell stack as a power source. [4] Fuel cell system according to claim 1 or 2, the fuel cell stack arrangement further includes an internal power source, and the data storage starts using the internal power source as the power source. [5] Method for determining the reusability of a fuel cell stack, wherein for the fuel cell system defined by one of claims 1 to 4, the fuel cell stack of the fuel cell system is determined to be non-reusable if at least one abnormal start-up data record is included in the stored start-up history.

Images