Air-cooled fuel cell system

Abstract

Provided is a fuel cell system capable of suppressing deterioration of a fuel cell. A fuel cell system is provided with a fuel cell having a reaction air flow path and a cooling air flow path each having a flow path structure in which reaction air and cooling air are independent, a hydrogen system, a reaction air system having an inlet-side seal valve at an inlet of the reaction air of the fuel cell, and a cooling air system having an outlet-side seal valve at an outlet of the reaction air of the fuel cell. When the system is stopped, the fuel cell system continues the supply of hydrogen to the fuel cell and the supply of cooling air to the fuel cell, and stops the supply of reaction air to the fuel cell. And closing the inlet-side sealing valve and the outlet-side sealing valve to seal the cathode of the fuel cell, after which the supply of cooling air to the fuel cell is intermittently or continuously continued, and the supply of hydrogen to the fuel cell is stopped.

Description

Technical Field

[0001] The present disclosure relates to an air-cooled fuel cell system. Background Art

[0002] Various technologies have been proposed regarding fuel cells (FC) such as those disclosed in Patent Documents 1 to 6.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2005-216783

[0004] Patent Document 2: Japanese Patent Application Publication No. 2012-505496

[0005] Patent Document 3: Japanese Patent Application Publication No. 2007-115533

[0006] Patent Document 4: Japanese Patent Application Publication No. H06-022155

[0007] Patent Document 5: Japanese Patent Application Publication No. 2022-185251

[0008] Patent Document 6: Japanese Patent Application Publication No. 2022-185247

[0009] In the case of an open air-cooled fuel cell, when the system is stopped, if the air supply is stopped, the cathode is exposed to the air, so an abnormal potential is generated in the cell of the fuel cell, resulting in degradation of the fuel cell. Summary of the invention

[0010] The present disclosure has been made in view of the above-mentioned actual situation, and a main object of the present disclosure is to provide an air-cooled fuel cell system capable of suppressing degradation of a fuel cell.

[0011] In a first embodiment of the present disclosure, there is provided a fuel cell system, which is an air-cooled fuel cell system, characterized in that:

[0012] The fuel cell system includes a fuel cell, a hydrogen system for supplying hydrogen to the fuel cell, a reaction air system for supplying reaction air to the fuel cell, and a cooling air system for supplying cooling air to the fuel cell.

[0013] The fuel cell has a reaction air flow path and a cooling air flow path in which the reaction air and the cooling air have independent flow paths.

[0014] The reaction air system has an inlet-side sealing valve at the inlet of the reaction air of the fuel cell and an outlet-side sealing valve at the outlet of the reaction air of the fuel cell.

[0015] When the fuel cell system is stopped, the supply of hydrogen and the supply of cooling air to the fuel cell continue, and the supply of reaction air to the fuel cell is stopped, and the inlet side sealing valve and the outlet side sealing valve are closed to seal the cathode of the fuel cell, and thereafter, the supply of cooling air to the fuel cell is continued intermittently or continuously, and the supply of hydrogen to the fuel cell is stopped.

[0016] In a second embodiment of the present disclosure, it may be configured as follows: based on the first embodiment, the reaction air system includes a reaction air supply mechanism.

[0017] The cooling air system has a cooling air supply mechanism.

[0018] The hydrogen exhaust flow path of the hydrogen system merges with the cooling air exhaust flow path of the cooling air system.

[0019] In a third embodiment of the present disclosure, the fuel cell system may be configured as follows: in addition to the first embodiment, the fuel cell system includes an electrical system.

[0020] The fuel cell system connects the fuel cell to a power line of the electrical system when the system is stopped.

[0021] In a fourth embodiment of the present disclosure, in addition to the first embodiment, the hydrogen system may include a hydrogen pump.

[0022] The fuel cell system of the present disclosure can suppress degradation of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an exploded perspective schematic diagram showing an example of a single cell of a fuel cell included in the fuel cell system of the present disclosure.

[0024] Figure 2 It is a perspective schematic diagram showing an example of a fuel cell stack included in the fuel cell system of the present disclosure.

[0025] Figure 3 1 is a system configuration diagram showing an example of the fuel cell system of the present disclosure.

[0026] Figure 4 1 is a circuit diagram showing an example of an electrical system included in the fuel cell system of the present disclosure.

[0027] Figure 5 1 is a flowchart showing an example of control of the fuel cell system of the present disclosure.

[0028] Figure 6: is a flowchart showing another example of control of the fuel cell system of the present disclosure.

[0029] Description of Reference Numerals

[0030] 1…battery cell; 2…cooling fin (cooling air flow path); 3…reaction air inlet; 4…reaction air outlet; 5…hydrogen inlet; 6…hydrogen outlet; 7…cooling air (cooling gas); 8…hydrogen; 9…reaction air; 10…fuel cell stack; 11…diaphragm; 12…MEA, resin frame; 13…collecting plate; 14…pressurizing plate; 20…reaction air system; 21…reaction air intake port; 22…air blower; 23…inlet side sealing valve; 24…outlet side sealing valve; 30…cooling air system; 31…cooling fan; 40…hydrogen system; 41…hydrogen tank; 42…hydrogen inlet valve; 43…gas-liquid separator; 44…hydrogen purge valve; 45…hydrogen pump; 50…electrical system; 51…power line; 52…diode; 53…relay; 54…power consumption absorption mechanism; 55…auxiliary equipment; 56…power consumption equipment. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present disclosure. In addition, matters required for the implementation of the present disclosure other than matters specifically mentioned in this specification (for example, the general structure and manufacturing process of the fuel cell system that does not characterize the present disclosure) can be understood as design matters for those skilled in the art based on the prior art in the art. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the art.

[0032] In addition, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships.

[0033] In the present disclosure, the gas supplied to the anode of the fuel cell is the fuel gas (anode gas), and the gas supplied to the cathode of the fuel cell is the oxidant gas (cathode gas). The fuel gas is a gas mainly containing hydrogen, and may also be hydrogen. The oxidant gas is a gas containing oxygen, and may also be oxygen, air, etc. In the present disclosure, the air serving as the oxidant gas is referred to as reaction air, and the air serving as the cooling gas is referred to as cooling air.

[0034] In the present disclosure, a fuel cell system is provided, which is an air-cooled fuel cell system, characterized in that the fuel cell system comprises a fuel cell, a hydrogen system for supplying hydrogen to the fuel cell, a reaction air system for supplying reaction air to the fuel cell, and a cooling air system for supplying cooling air to the fuel cell, the fuel cell having a reaction air flow path and a cooling air flow path with independent flow path structures for the reaction air and the cooling air, the reaction air system having an inlet side sealing valve at the inlet of the reaction air of the fuel cell, and an outlet side sealing valve at the outlet of the reaction air of the fuel cell, the fuel cell system continues to supply the hydrogen to the fuel cell and the cooling air to the fuel cell when the system is stopped, stops the supply of the reaction air to the fuel cell, and closes the inlet side sealing valve and the outlet side sealing valve to seal the cathode of the fuel cell, and thereafter, continues to supply the cooling air to the fuel cell intermittently or continuously, and stops the supply of hydrogen to the fuel cell.

[0035] When the fuel cell system is stopped, if air is mixed into the anode partly due to cross leakage, etc., the catalyst layer in the cell surface of the fuel cell is partially exposed to high potential, causing the catalyst layer to deteriorate. In order to prevent the abnormal potential from occurring, the oxygen in the cathode needs to be consumed to sufficiently reduce the cell voltage during the shutdown process of the fuel cell system.

[0036] In an air-cooled fuel cell, the volume of the fluid used for cooling is larger than that of a water-cooled fuel cell, and the flow path structure for flowing the fluid is also larger.

[0037] For example, the cooling water required for 4 kW of cooling is about 5 L / min, while in the case of air, more than 10,000 L / min is required.

[0038] If the power generation operation of the fuel cell is continued, the accumulation of oxides on the catalyst surface of the cathode reduces the catalyst activity and reduces the power generation efficiency.

[0039] In a general open air-cooled fuel cell, the opening of the air system is relatively large, and it is difficult to seal the cathode when the power generation of the fuel cell ends. After the power generation stops, air flows into the cathode, and the electrolyte membrane cross-leakage and oxygen is also mixed into the anode. This state is a state in which an abnormal potential of the fuel cell is generated, and the degradation of the catalyst layer cannot be avoided. The main reason why the life of a general open air-cooled fuel cell is short to less than 1000 hours is the generation of abnormal potential. In addition, even if the cathode is sealed, its spatial volume is relatively large. It takes time to fully reduce the oxygen in the cathode space. If there is residual oxygen, the fuel cell becomes abnormally potential when the system stops.

[0040] When air is added to the cathode and hydrogen is added to the anode without current flowing, the potential of the fuel cell becomes high (about 0.95 to 1.05 V). In this state, although it is stable, the degradation of the fuel cell is aggravated. In addition, an oxide film is generated on the Pt catalyst, causing the performance of the catalyst to decrease. To avoid this, the potential of the fuel cell can also be operated at a constant level below 0.85 V.

[0041] The present disclosure relates to improving the performance of an air-cooled fuel cell, and proposes a structure and method for preventing the generation of abnormal potential of a fuel cell and the degradation of the fuel cell, and smoothly stopping the system. A fuel cell having a flow path structure in which reaction air and cooling air are independent is stopped in a prescribed order. When the system is stopped, the supply of reaction air is stopped to cut off the cathode from the outside of the fuel cell system and consume the reaction air, and then the system is stopped, thereby suppressing the degradation of the fuel cell. The hydrogen discharged in the stopping process can be diluted with cooling air.

[0042] The fuel cell system includes a fuel cell that generates electricity by reacting hydrogen with air, a hydrogen system that supplies hydrogen required for power generation to the fuel cell, a reaction air system that supplies reaction air to the fuel cell, and a cooling air system that supplies cooling air to the fuel cell to cool the heat generated by power generation.

[0043] The fuel cell may be a single cell (battery cell) having only one fuel cell, or may be a fuel cell stack (battery stack) which is a stacked body in which a plurality of cells are stacked.

[0044] In the present disclosure, there are cases where both a battery cell and a fuel cell stack are referred to as a fuel cell.

[0045] The number of stacked cells in the fuel cell stack is not particularly limited, and may be, for example, 2 to several hundred.

[0046] The fuel cell stack may include corrugated cooling fins serving as cooling air flow paths in each cell.

[0047] The fuel cell stack may have a collecting plate, a pressurizing plate, etc. at the end portion in the stacking direction.

[0048] The fuel cell has a reaction air flow path (oxidant gas flow path) and a cooling air flow path (cooling gas flow path) in which the reaction air and cooling air have independent flow paths, and may further have a hydrogen flow path (fuel gas flow path).

[0049] The independent flow path structure of reaction air and cooling air means that the air does not communicate between the flow paths from the supply of air to the fuel cell to the exhaust of air from the fuel cell. In addition, the flow paths for exhausting the air exhausted from the fuel cell to the outside of the fuel cell system may be independent or not.

[0050] The cell may also include a flow path structure that allows the reaction air and the cooling air to flow so that the flow of the cooling air intersects with the flow of the reaction air in a plan view. The flow of the cooling air and the flow of the reaction air may intersect or be orthogonal.

[0051] The battery cell may have a power generation unit.

[0052] The shape of the power generation unit may be a rectangle in a plan view.

[0053] The power generation unit may be a membrane electrode assembly (MEA) including an electrolyte membrane and two electrodes.

[0054] The electrolyte membrane may also be a solid polymer electrolyte membrane. As the solid polymer electrolyte membrane, for example, a fluorine electrolyte membrane such as a film of perfluorosulfonic acid containing water, and a hydrocarbon electrolyte membrane may be cited. As the electrolyte membrane, for example, a Nafion membrane (manufactured by DuPont) may also be used.

[0055] The two electrodes are the anode (fuel or hydrogen) and the cathode (oxygen or air).

[0056] The electrode includes a catalyst layer and may include a gas diffusion layer as required, and the power generation unit may be a membrane electrode gas diffusion layer assembly (MEGA).

[0057] The catalyst layer may include a catalyst including a catalyst metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, and a carrier having electron conductivity.

[0058] As the catalyst metal, for example, platinum (Pt) and alloys composed of Pt and other metals (for example, Pt alloys mixed with cobalt, nickel, etc.) can be used. The catalyst metal used as the cathode catalyst and the catalyst metal used as the anode catalyst may be the same or different.

[0059] The electrolyte may be a fluorine-based resin or the like. For example, a Nafion solution or the like may be used as the fluorine-based resin.

[0060] The above-mentioned catalyst metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalyst metal (catalyst-supporting carrier) and the electrolyte may be present in a mixed state.

[0061] Examples of the carrier for supporting the catalyst metal include carbon materials such as carbon generally available on the market.

[0062] The gas diffusion layer may be a conductive member having pores or the like.

[0063] Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous members such as metal mesh and foamed metal.

[0064] The cells of the fuel cell may also include a membrane.

[0065] The diaphragm collects the current generated by power generation and functions as a partition. In the battery cell of a fuel cell, the diaphragm is usually arranged on both sides of the stacking direction of the power generation part in a way that a pair of diaphragms sandwich the power generation part. One side of the pair of diaphragms is the anode diaphragm and the other side is the cathode diaphragm.

[0066] The anode separator may have grooves serving as hydrogen flow paths on the surface on the power generation portion side, and may have grooves serving as cooling air flow paths on the surface on the opposite side to the power generation portion.

[0067] The cathode separator may have grooves serving as reaction air flow paths on the surface facing the power generation portion, and may have grooves serving as cooling air flow paths on the surface facing the opposite side to the power generation portion.

[0068] The separator may have holes constituting manifolds such as supply holes and discharge holes for allowing the fluid to flow in the stacking direction of the battery cells.

[0069] The separator may be, for example, dense carbon obtained by compressing carbon to be airtight, or press-formed metal (for example, iron, titanium, stainless steel, etc.).

[0070] The battery cell may also be provided with an insulating resin frame disposed on the outside (periphery) of the surface direction of the membrane electrode assembly between the anode separator and the cathode separator. The resin frame is formed into a plate-like and frame-like shape using a thermoplastic resin, and the anode separator and the cathode separator are sealed while the membrane electrode assembly is maintained in its central area. As the resin frame, for example, resins such as PE, PP, PET, and PEN can be used. The resin frame may also be a three-layer sheet body consisting of three layers in which an adhesive layer is disposed on the surface layer.

[0071] The fuel cell system may also include a control device, which controls the reaction air system, the hydrogen system, the cooling air system, etc., and may also control the entire fuel cell system.

[0072] The control device physically has, for example, a processing unit such as a CPU (central processing unit), a ROM (read-only memory) for storing control programs and control data processed by the CPU, a storage device such as a RAM (random access memory) mainly used as various work areas for control processing, and an input / output interface. It can also be an ECU (electronic control unit), etc.

[0073] The reaction air system supplies reaction air as oxidant gas to the fuel cell and adjusts the flow rate of the reaction air. The reaction air system may also include reaction air piping and the like.

[0074] The hydrogen system supplies hydrogen as fuel gas to the fuel cell and adjusts the flow rate of the hydrogen. The hydrogen system may also include a hydrogen tank, a hydrogen inlet valve, an ejector, a gas-liquid separator, a hydrogen purge valve, an ejector for hydrogen circulation, a hydrogen pump for hydrogen circulation, and hydrogen piping.

[0075] The cooling air system supplies cooling air as cooling gas to the fuel cell and adjusts the flow rate of the cooling air.

[0076] The reaction air system has an inlet-side sealing valve at the reaction air inlet of the fuel cell and an outlet-side sealing valve at the reaction air outlet of the fuel cell.

[0077] In the present disclosure, the fuel cell has an independent flow path structure for reaction air and cooling air, and in the reaction air system, valves (inlet side sealing valve and outlet side sealing valve) are set at the inlet and outlet of the reaction air of the fuel cell, thereby enabling the fuel cell to seal the cathode of the fuel cell with a smaller volume than the case of having a flow path structure shared by the reaction air and the cooling air.

[0078] The reaction air system may include a reaction air supply mechanism, the cooling air system may include a cooling air supply mechanism, and the hydrogen exhaust flow path of the hydrogen system may merge with the cooling air exhaust flow path of the cooling air system.

[0079] Furthermore, the hydrogen exhaust flow path of the hydrogen system may further include a merging portion capable of merging with the reaction air exhaust flow path of the reaction air system.

[0080] The reaction air system and the cooling air system are provided with independent air supply mechanisms, and the hydrogen exhaust flow path merges with the cooling air exhaust flow path. Therefore, when the system stops, the fuel cell system stops the reaction air supply mechanism and drives the cooling air supply mechanism, thereby being able to dilute the exhaust hydrogen with cooling air and discharge it to the outside of the fuel cell system.

[0081] The reaction air supply mechanism and the cooling air supply mechanism may also be an air compressor, an air pump, an air blower, an air fan, etc. respectively.

[0082] The reaction air system may include a reaction air intake port for taking in reaction air from outside the fuel cell system, and a pressure loss body such as an air filter may be provided at the reaction air intake port.

[0083] The cooling air system may include a cooling air intake port for taking in cooling air from outside the fuel cell system, and a pressure loss body such as an air filter may be provided at the cooling air intake port.

[0084] When the fuel cell system is stopped, the supply of hydrogen and cooling air to the fuel cell is continued, and the supply of reaction air to the fuel cell is stopped, and the reaction air inlet side sealing valve and the reaction air outlet side sealing valve are closed to seal the cathode of the fuel cell, and then the supply of cooling air to the fuel cell is continued intermittently or continuously, and the supply of hydrogen to the fuel cell is stopped. The subsequent operation may be after a predetermined time has passed, or after the voltage of the fuel cell drops below a predetermined voltage.

[0085] Furthermore, the fuel cell system may also disconnect the cathode and anode of the fuel cell from the outside of the fuel cell system when the system is stopped.

[0086] By stopping the fuel cell system according to the following stop sequence, it is possible to prevent the fuel cell from being degraded.

[0087] (1) Stop sequence 1

[0088] If necessary, the fuel cell is purged and drained, the air blower is disconnected, and the inlet-side sealing valve and the outlet-side sealing valve of the reaction air system are closed to seal the reaction air system.

[0089] (2)Stop sequence 2

[0090] Furthermore, the hydrogen system is scavenged and drained. The hydrogen purge valve may be opened and closed. At this time, the cooling fan may be turned on intermittently or continuously to dilute and exhaust hydrogen.

[0091] After the voltage of the fuel cell drops to a specified value, the hydrogen purge valve and the hydrogen inlet valve are closed to seal the hydrogen system. If the hydrogen purge valve is stopped, the hydrogen inlet valve can also be closed after the cooling fan is stopped. If the hydrogen purge valve is closed, the flow of hydrogen stops, so there is no need to dilute the hydrogen. Therefore, the cooling fan can be stopped before, after, or at the same time as the hydrogen inlet valve is closed.

[0092] When the power generation operation of the fuel cell ends, the cathode is sealed first, and then the hydrogen system is sealed after the hydrogen system is purified by opening and closing the hydrogen purge valve. In this way, the cell of the fuel cell can be sealed in a hydrogen-rich state, thereby preventing deterioration caused by abnormal potential of the stopped fuel cell.

[0093] When the anode is sealed before the cathode is sealed, oxygen continues to flow into the cathode, so that hydrogen becomes insufficient in the cell of the fuel cell, resulting in an abnormal potential state.

[0094] In order to seal the cathode with a small volume, a flow path structure for reaction air and cooling air is formed independently.

[0095] After the cathode is sealed, the purified hydrogen needs to be diluted and exhausted, so separate air supply mechanisms can also be set in the reaction air system and the cooling air system.

[0096] After the cathode is sealed, when the oxygen concentration decreases, if the voltage of the fuel cell drops, it is possible to ensure hydrogen in an amount equivalent to or greater than the amount of residual oxygen and stop the hydrogen supply.

[0097] When the fuel cell has a lot of liquid water and tends to overflow at the end of power generation, the flow rate of the air blower and hydrogen pump can be increased before sealing the reaction air system to perform scavenging and draining of the fuel cell.

[0098] The fuel cell system may also include an electrical system.

[0099] The electrical system may also have a diode on the power line to the fuel cell, and may also have a relay for the fuel cell. By having a diode, the generation of reverse current from the power line side to the fuel cell can be avoided. A power consumption absorption mechanism such as a secondary battery (battery) or a capacitor is connected to the power line.

[0100] The fuel cell system can also connect the fuel cell to the power line of the electrical system when the system is stopped. This can prevent the fuel cell from reaching a high potential during scavenging, and can reduce the voltage of the fuel cell in a short time.

[0101] By connecting the fuel cell to the power line via a diode and performing a stop process, the potential of the fuel cell can be kept below V2 at all times. If the above process is performed in an open circuit state where the relay is disconnected, the voltage of the fuel cell becomes a high potential (exceeding 0.9V) of the open circuit voltage (OCV), and the degradation of the fuel cell is aggravated. V2 can also be set according to the power consumption absorption mechanism such as the connected battery and capacitor so that the voltage of the fuel cell becomes an operating range of less than 0.85V. In addition, by absorbing electricity by using the power consumption absorption mechanism after the cathode is sealed, oxygen is quickly consumed by power generation, thereby completing the stop process in a short time.

[0102] The hydrogen system may also have a hydrogen pump for circulation. By having a hydrogen pump, it is possible to efficiently perform scavenging and drainage with a small amount of hydrogen. In addition, the hydrogen concentration in the fuel cell can be quickly uniformized, thereby preventing the degradation of the fuel cell caused by local hydrogen deficiency.

[0103] In stop sequence 2, the hydrogen system is circulated by the hydrogen pump, and the amount of hydrogen discharge can be suppressed while draining and scavenging can be performed. In addition, in stop sequences 1 and 2, local hydrogen shortage (= abnormal potential) can be prevented.

[0104] Figure 1 It is an exploded perspective schematic diagram showing an example of a single cell of a fuel cell included in the fuel cell system of the present disclosure.

[0105] Figure 1 The cell 1 shown in the figure has cooling fins (cooling air flow path) 2 which serve as a flow path for cooling air (cooling gas) 7, a reaction air inlet 3, a reaction air outlet 4, a hydrogen inlet 5, a hydrogen outlet 6, two diaphragms 11, and an MEA and a resin frame 12 sandwiched between the two diaphragms 11. Figure 1 As shown, the cell 1 of the fuel cell has a flow path structure in which the reaction air 9 and the cooling air 7 are independent.

[0106] Figure 2 It is a perspective schematic diagram showing an example of a fuel cell stack included in the fuel cell system of the present disclosure.

[0107] Figure 2 The fuel cell stack shown is a stacked body in which a plurality of cells 1 are stacked, and includes collecting plates 13 and pressure plates 14 at both ends in the stacking direction.

[0108] Figure 3 1 is a system configuration diagram showing an example of the fuel cell system of the present disclosure.

[0109] Figure 3The fuel cell system shown in the figure includes a fuel cell stack 10, a reaction air system 20, a cooling air system 30, and a hydrogen system 40. The reaction air system 20 includes a reaction air intake port 21, an air blower 22, an inlet side sealing valve 23, and an outlet side sealing valve 24. The cooling air system 30 includes a cooling fan 31. The hydrogen system 40 includes a hydrogen tank 41, a hydrogen inlet valve 42, a gas-liquid separator 43, a hydrogen purge valve 44, and a hydrogen pump 45. Figure 3 The fuel cell system shown in the figure is provided with sealing valves 23 and 24 at the inlet and outlet of the reaction air system 20 , and is provided with independent air supply mechanisms 22 and 31 in the reaction air system 20 and the cooling air system 30 .

[0110] Figure 4 1 is a circuit diagram showing an example of an electrical system included in the fuel cell system of the present disclosure.

[0111] Figure 4 The illustrated electrical system 50 includes a power line 51 , a diode 52 , a relay 53 , a power consumption absorbing mechanism 54 such as a battery or a capacitor, auxiliary equipment 55 , and power consuming equipment 56 .

[0112] By providing the diode 52 on the power line 51 , the fuel cell stack 10 is connected to the power line 51 during the recovery control, thereby avoiding the generation of reverse current from the power line 51 to the fuel cell stack 10 and shortening the recovery control time.

[0113] Figure 5 1 is a flowchart showing an example of control of the fuel cell system of the present disclosure.

[0114] Figure 5 (1) represents the stop sequence of the fuel cell system.

[0115] At the start of the stop sequence, the hydrogen inlet valve is open, the cooling fan is on, the reaction air sealing valves (inlet side sealing valve and outlet side sealing valve) are open, and the reaction air blower is on.

[0116] The reaction air sealing valve is closed to seal the reaction air system (S101).

[0117] The hydrogen purge valve is intermittently opened, and a purge process of the hydrogen system is started (S102).

[0118] When the voltage of the fuel cell drops to a predetermined value, the hydrogen inlet valve and the hydrogen purge valve are closed, the cooling fan is stopped, and the control is terminated (S104).

[0119] Figure 5 (2) represents the stop sequence in the fuel cell system structure including the hydrogen pump, relay, and diode.

[0120] At the start of the stop sequence, the hydrogen inlet valve is open, the hydrogen pump is on, the cooling fan is on, the reaction air sealing valves (inlet side sealing valve and outlet side sealing valve) are open, the reaction air blower is on, and the relay is on.

[0121] The fuel cell is purged (S201). The purging process may be performed for 5 seconds with a high flow rate of reaction air (a stoichiometric ratio of 3 or more when power generation is performed simultaneously, and a flow rate at which droplets in the flow path can move when power generation is not performed).

[0122] Thereafter, the reaction air sealing valve is closed to seal the reaction air system (S202).

[0123] Thereafter, the hydrogen system purge process is started (S203). For the hydrogen system purge, the hydrogen purge valve may be opened intermittently (S204) and the hydrogen pump may be circulated at a high flow rate for a certain period of time.

[0124] It is also possible to prepare a data group indicating the relationship between the pressure change when the hydrogen purge valve is opened, the cell temperature, and the scavenging required time in advance, and determine that the scavenging is complete based on the passage of the scavenging required time.

[0125] After it is determined that the scavenging is completed (S205), the hydrogen pump is disconnected (S206). After the hydrogen pump is disconnected, the hydrogen system is finally purified in order to discharge the liquid water and the like accumulated in the gas-liquid separator. For the final purification of the hydrogen system, the hydrogen purge valve may be intermittently opened while the hydrogen pump is disconnected (S207).

[0126] After the final purge of the hydrogen system is completed, the exhaust hydrogen is diluted to the outside of the fuel cell system by cooling air, and then the hydrogen purge valve is closed and the cooling fan is turned off (S208).

[0127] The fuel cell voltage may be monitored, and after the average cell voltage becomes 0.4 V or less (S209), the relay may be turned off (S210). After the relay is turned off, the hydrogen inlet valve may be closed to seal the hydrogen system (S211), and the control may be terminated.

[0128] Figure 6 : is a flowchart showing another example of control of the fuel cell system of the present disclosure.

[0129] like Figure 6 As shown, from the perspective of shortening the stop process time, the hydrogen system scavenging process (S401) to (S407) may be performed in parallel with the fuel cell scavenging process (S301) to (S302) and the electrical system stop process (S303) to (S304).

[0130] After the reaction air system is sealed, the electrical system is shut down, the hydrogen system is finally purged (exhaust gas is diluted with cooling air), and the hydrogen system is sealed, thereby preventing the generation of abnormal potential in the fuel cell.

Claims

1. A fuel cell system, which is an air-cooled fuel cell system, characterized in that: The fuel cell system includes a fuel cell, a hydrogen system for supplying hydrogen to the fuel cell, a reaction air system for supplying reaction air to the fuel cell, and a cooling air system for supplying cooling air to the fuel cell. The fuel cell has a reaction air flow path and a cooling air flow path in which the reaction air and the cooling air have independent flow paths. The reaction air system has an inlet-side sealing valve at the reaction air inlet of the fuel cell and an outlet-side sealing valve at the reaction air outlet of the fuel cell. When the fuel cell system is stopped, the fuel cell system continues to supply the hydrogen and the cooling air to the fuel cell, stops the supply of the reaction air to the fuel cell, and closes the inlet-side sealing valve and the outlet-side sealing valve to seal the cathode of the fuel cell, and then continues to supply the cooling air to the fuel cell intermittently or continuously, and stops the supply of hydrogen to the fuel cell.

2. The fuel cell system according to claim 1, characterized in that: The reaction air system has a reaction air supply mechanism. The cooling air system comprises a cooling air supply mechanism. The hydrogen exhaust flow path of the hydrogen system merges with the cooling air exhaust flow path of the cooling air system.

3. The fuel cell system according to claim 1, characterized in that: The fuel cell system comprises an electrical system, The fuel cell system connects the fuel cell to a power line of the electrical system when the system is stopped.

4. The fuel cell system according to claim 1, characterized in that: The hydrogen system has a hydrogen pump.

5. The fuel cell system according to claim 1, characterized in that: The fuel cell has at least one single cell, which has an anode diaphragm, a power generation unit, and a cathode diaphragm in sequence. The cathode diaphragm has the reaction air flow path on one side of the power generation unit and the cooling air flow path on the opposite side of the power generation unit.

6. The fuel cell system according to claim 5, characterized in that: The single cell has corrugated cooling fins as the cooling air flow path.

7. The fuel cell system according to claim 1, characterized in that: After a predetermined time has passed or the voltage of the fuel cell drops below a predetermined voltage, the fuel cell system continues to supply the cooling air to the fuel cell intermittently or continuously and stops supplying the hydrogen to the fuel cell.

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