Dead-end operation-type air-cooled fuel cell system

Abstract

The present invention relates to a dead-end operation-type air-cooled fuel cell system. The dead-end operation-type air-cooled fuel cell system according to one embodiment of the present invention may comprise: a fuel cell stack including a plurality of fuel cells, and a hydrogen discharge line in which a hydrogen discharge valve is provided and which is connected to a hydrogen discharge manifold; an air supply unit for supplying air to the fuel cell stack; a hydrogen supply unit for supplying hydrogen to the fuel cell stack; a cooling unit including a cooling fan for supplying cooling air to the fuel cell stack, and a temperature sensor provided between the fuel cell stack and the cooling fan so as to measure the exhaust temperature of the cooling air discharged from the fuel cell stack; a voltage measurement unit for measuring the voltage of the fuel cell stack; and a control unit which is connected to each of the fuel cell stack, the air supply unit, the hydrogen supply unit, the cooling unit and the voltage measurement unit, and which controls that the hydrogen discharge valve is repeatedly opened and closed at hydrogen discharge valve opening and closing time intervals from closing of the hydrogen discharge value to re-opening of the hydrogen discharge valve.

Description

Air-cooled fuel cell system with dead-end operation

[0001] The present invention relates to an air-cooled fuel cell system of a dead-end operation type, and more particularly, to an air-cooled fuel cell system of a dead-end operation type, comprising: a fuel cell stack having a plurality of fuel cell cells and hydrogen discharge valves installed therein and a hydrogen discharge line connected to a hydrogen discharge manifold; an air supply unit for supplying air to the fuel cell stack; a hydrogen supply unit for supplying hydrogen to the fuel cell stack; a cooling unit including a cooling fan for supplying cooling air to the fuel cell stack and a temperature sensor installed between the fuel cell stack and the cooling fan to measure the discharge temperature of cooling air discharged from the fuel cell stack; a voltage measurement unit for measuring the voltage of the fuel cell stack; and a control unit connected to each of the fuel cell stack, the air supply unit, the hydrogen supply unit, the cooling unit, and the voltage measurement unit, and controlling the opening and closing of the hydrogen discharge valve to be repeated at a hydrogen discharge valve opening and closing time interval until the hydrogen discharge valve is closed and then opened again.

[0002] Fuel cell systems are divided into air-cooled fuel cell systems that supply air to the fuel cell stack and water-cooled fuel cell systems that supply water to the fuel cell stack, depending on the cooling method.

[0003] The dual air-cooled fuel cell system consists of a fuel cell stack and electrical / mechanical peripherals (Balance of Plant, BOP) connected to the fuel cell stack. Compared to the water-cooled fuel cell system, it has fewer parts and a simpler structure, so it is mainly used in small, low-power devices such as drones, microcars, and small generators.

[0004] In the field of air-cooled fuel cell system research, it is known that various technologies are being developed to miniaturize and reduce the weight of air-cooled fuel cell systems, depending on the characteristics of air-cooled fuel cell systems, which are mainly used in small, low-power devices.

[0005] A technology known for miniaturizing and reducing the weight of air-cooled fuel cell systems is hydrogen purge technology, which forcibly discharges hydrogen from the fuel cell stack.

[0006] Hydrogen purge technology is a technology that prevents H2O flooding generated at the hydrogen electrode of a fuel cell cell in a dead-end operation method where hydrogen gas is supplied to a fuel cell stack at a certain pressure and the manifold through which the hydrogen gas is discharged is closed with a valve to confine hydrogen inside the fuel cell stack and generate power. It is a technology that forcibly discharges hydrogen and H2OP by opening a valve installed in the manifold at certain intervals to prevent H2O flooding generated at the hydrogen electrode of the fuel cell cell.

[0007] According to this hydrogen purge technology, even when the air-cooled fuel cell system is operated in dead-end operation, hydrogen and H2O are forcibly discharged by opening the valve, so H2O flooding of the fuel cell cell can be prevented. However, there is a problem in that hydrogen is wasted because hydrogen is inefficiently and forcibly discharged without considering the operating environment of the fuel cell system.

[0008] Additionally, another known technology for improving the power generation performance of air-cooled fuel cell systems is current pulse technology, which improves the power generation performance of fuel cell cells by applying current pulses to the fuel cell stack at regular intervals.

[0009] However, when hydrogen purge technology and current pulse technology are applied to an air-cooled fuel cell system using a dead-end operation method, there is a problem in that the catalyst layer of the fuel cell cell is corroded due to hydrogen deficiency or the electrode is damaged by heat due to overvoltage occurring in the fuel cell.

[0010] [Prior Art Literature]

[0011] [Patent Document]

[0012] (Patent Document 1): KR 2015-0118296 (Published on October 22, 2015)

[0013] (Patent Document 2): KR 2022-0102446 (July 20, 2022)

[0014] The present invention has been devised to solve the above problems, and the present invention provides an air-cooled fuel cell system of dead-end operation that can reduce hydrogen waste by efficiently discharging hydrogen through controlling the operating environment of the fuel cell system.

[0015] In addition, the present invention provides an air-cooled fuel cell system of dead-end operation in which fuel cell cells are not damaged even when hydrogen purge technology and current pulse technology are applied to the fuel cell stack.

[0016] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0017] According to one embodiment of the present invention, an air-cooled fuel cell system of a dead-end operation type may include a fuel cell stack including a plurality of fuel cell cells and a hydrogen discharge valve installed therein and a hydrogen discharge line connected to a hydrogen discharge manifold, an air supply unit for supplying air to the fuel cell stack, a hydrogen supply unit for supplying hydrogen to the fuel cell stack, a cooling unit including a cooling fan for supplying cooling air to the fuel cell stack and a temperature sensor installed between the fuel cell stack and the cooling fan to measure the discharge temperature of cooling air discharged from the fuel cell stack, a voltage measurement unit for measuring the voltage of the fuel cell stack, and a control unit connected to each of the fuel cell stack, the air supply unit, the hydrogen supply unit, the cooling unit, and the voltage measurement unit, and controlling the opening and closing of the hydrogen discharge valve to be repeated at a hydrogen discharge valve opening and closing time interval until the hydrogen discharge valve is closed and then opened again.

[0018] In addition, when the discharge temperature of the cooling air is lower than the appropriate operating temperature of the fuel cell stack, the hydrogen discharge valve opening / closing time interval is the first hydrogen discharge valve opening / closing time interval, and when the discharge temperature of the cooling air exceeds the appropriate operating temperature of the fuel cell stack, the hydrogen discharge valve opening / closing time interval is the second hydrogen discharge valve opening / closing time interval, and the first hydrogen discharge valve opening / closing time interval may be greater than the second hydrogen discharge valve opening / closing time interval.

[0019] In addition, the fuel cell stack may further include an air exhaust line having an air exhaust valve installed and connected to an air inlet manifold, the air supply unit may include an air blower that supplies air to the fuel cell stack, and the voltage measurement unit may include a voltage measurement sensor installed adjacent to a hydrogen outlet of each of the plurality of fuel cell cells and a voltage monitoring device connected to the voltage measurement sensor.

[0020] In addition, the control unit can close the air discharge valve and increase the discharge pressure of the air blower at the same time as opening the hydrogen discharge valve when the discharge temperature of the cooling air exceeds the operating temperature and operating limit temperature of the fuel cell stack to discharge a large amount of air to the air discharge manifold of the fuel cell stack.

[0021] Additionally, it may further include a current pulse unit that applies a pulse current to the fuel cell stack.

[0022] Additionally, the control unit can block current drawn out from the fuel cell stack after the hydrogen discharge valve is closed and a first time interval has elapsed, and apply a pulse current to the fuel cell stack from the current pulse unit.

[0023] Additionally, the fuel cell stack may further include an air exhaust line having an air exhaust valve installed therein and connected to an air inlet manifold, the air supply unit may include an air blower that supplies air to the fuel cell stack, and the voltage measurement unit may include a voltage measurement sensor installed adjacent to a hydrogen outlet of each of the plurality of fuel cell cells and a voltage monitoring device connected to the voltage measurement sensor.

[0024] In addition, the control unit can open the hydrogen discharge valve and simultaneously close the air discharge valve and increase the discharge pressure of the air blower to discharge a large amount of air to the air discharge manifold of the fuel cell stack when the discharge temperature of the cooling air exceeds the appropriate operating temperature and operating limit temperature of the fuel cell stack.

[0025] According to an air-cooled fuel cell system of dead-end operation according to one embodiment of the present invention, the amount of hydrogen (H2) discharged out of the fuel cell stack by hydrogen purge can be minimized by controlling the opening / closing time interval of the hydrogen discharge valve according to the operating conditions and environment of the fuel cell system.

[0026] In addition, according to an air-cooled fuel cell system of dead-end operation according to one embodiment of the present invention, when the discharge temperature of the cooling air exceeds the appropriate operating temperature and the operating limit temperature of the fuel cell stack, air purge is performed on the air electrode of the fuel cell cell, thereby minimizing the amount of hydrogen (H2) discharged out of the fuel cell stack by hydrogen purge.

[0027] In addition, according to the air-cooled fuel cell system of dead-end operation according to one embodiment of the present invention, the performance of the fuel cell cell can be improved and damage can be prevented, thereby extending the service life by performing hydrogen purge and current pulse application at regular time intervals.

[0028] FIG. 1 is a block diagram of an air-cooled fuel cell system of dead-end operation according to a first embodiment of the present invention.

[0029] FIG. 2 is a schematic diagram illustrating an air-cooled fuel cell system of dead-end operation mode excluding the control unit in FIG. 1.

[0030] FIG. 3 is a schematic drawing of a fuel cell of an air-cooled fuel cell stack of the dead-end operation method of FIG. 2.

[0031] FIG. 4 is a schematic diagram illustrating the progress of hydrogen purging in the air-cooled fuel cell system of the dead-end operation method of FIG. 2.

[0032] FIG. 5 is a drawing showing the opening / closing time interval of a hydrogen discharge valve and the hydrogen purge section in a hydrogen purge progress state in an air-cooled fuel cell system of the dead-end operation method of FIG. 4.

[0033] FIG. 6 is a schematic diagram illustrating an air-cooled fuel cell system of dead-end operation mode excluding a control unit according to a second embodiment of the present invention.

[0034] Fig. 7 is a schematic diagram illustrating the progress of hydrogen purge and air purge in the air-cooled fuel cell system of the dead-end operation method of Fig. 6.

[0035] Figure 8 is a drawing showing a hydrogen purge section in a hydrogen purge and gas purge progress state in an air-cooled fuel cell system of the dead-end operation method of Figure 6.

[0036] FIG. 9 is a block diagram of an air-cooled fuel cell system of dead-end operation according to a third embodiment of the present invention.

[0037] FIG. 10 is a schematic diagram illustrating a dead-end operation type air-cooled fuel cell system excluding the control unit from the dead-end operation type air-cooled fuel cell system of FIG. 9.

[0038] Fig. 11 is a schematic diagram illustrating a state in which hydrogen purge and current pulse application are performed simultaneously in the air-cooled fuel cell system of the dead-end operation method of Fig. 10.

[0039] Figure 12 is a diagram showing the voltage state when hydrogen purge and current pulse application are performed simultaneously in the air-cooled fuel cell system of the dead-end operation method of Figure 11.

[0040] FIG. 13 is a schematic diagram illustrating a state in which a current pulse is applied to a fuel cell stack after hydrogen purging in the air-cooled fuel cell system of the dead-end operation method of FIG. 10.

[0041] FIG. 14 is a diagram schematically illustrating the hydrogen discharge valve opening / closing time interval, the first time interval during which the current pulse is applied, and the hydrogen purge section in a state in which a current pulse is applied to the fuel cell stack after hydrogen purge in the air-cooled fuel cell system of the dead-end operation method of FIG. 10.

[0042] Fig. 15 is a block diagram of an air-cooled fuel cell system of dead-end air-cooling operation according to a fourth embodiment of the present invention.

[0043] FIG. 16 is a schematic diagram illustrating the progress of hydrogen purge and air purge in the air-cooled fuel cell system of the dead-end operation method of FIG. 15 and the state in which a current pulse is applied to the fuel cell stack after the progress of hydrogen purge and air purge.

[0044] Figure 17 is a schematic diagram illustrating a hydrogen purge section after hydrogen purge, current pulse application to the fuel cell stack of Figure 16, and air purge are sequentially performed.

[0045] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described below in detail, along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms.

[0046] Hereinafter, the technical features of the present invention will be described in detail with reference to the attached drawings.

[0047] FIG. 1 is a block diagram of an air-cooled fuel cell system of dead-end operation according to a first embodiment of the present invention.

[0048] Referring to FIG. 1, the air-cooled fuel cell system (100) of dead-end operation mode according to the first embodiment of the present invention may include a fuel cell stack (10), an air supply unit (20), a hydrogen supply unit (30), a cooling unit (40), a voltage measurement unit (50), and a control unit (60).

[0049] Below, a detailed description is given of an air-cooled fuel cell system (100) of dead-end operation according to the present embodiment.

[0050] FIG. 2 is a schematic drawing of an air-cooled fuel cell system of dead-end operation mode excluding the control unit of FIG. 1, and FIG. 3 is a schematic drawing of a fuel cell of an air-cooled fuel cell stack of dead-end operation mode of FIG. 2.

[0051] Referring to FIGS. 2 and 3, a fuel cell stack (10) according to the present embodiment may include a plurality of stacked fuel cell cells (11) and a hydrogen discharge line (HDL) in which a hydrogen discharge valve (HDB) is installed and connected to a hydrogen discharge manifold.

[0052] A fuel cell cell (11) may include a cell body (11a), a hydrogen inlet (11b) formed on one surface of the cell body (11a), and a hydrogen outlet (11c) formed on the other surface of the cell body (11a) in a diagonal direction of the hydrogen inlet (11b).

[0053] Accordingly, when a plurality of fuel cell cells (11) are stacked, a plurality of hydrogen inlets (11b) can be arranged facing each other to form a hydrogen inlet manifold (not shown), and a plurality of hydrogen outlets (11c) can be arranged facing each other to form a hydrogen discharge manifold (not shown).

[0054] According to the present embodiment, a hydrogen discharge line (HDL) having a hydrogen discharge valve (HDB) installed can be connected to a hydrogen discharge manifold formed by arranging a plurality of hydrogen discharge ports (11c) facing each other.

[0055] According to this embodiment, the end of the hydrogen inlet manifold located in the opposite direction of the hydrogen inlet (11b) is closed by an end plate (not shown).

[0056] As illustrated in Fig. 2, when the hydrogen discharge valve (HDB) installed in the hydrogen discharge line (HDL) is closed, hydrogen flowing into the fuel cell stack (10) does not flow out of the fuel cell stack (10) but is trapped in the hydrogen inlet manifold, fuel cell cell (11), and hydrogen discharge manifold.

[0057] Therefore, according to this embodiment, the fuel cell system can be operated in a dead end manner in which hydrogen is trapped inside the fuel cell stack (10).

[0058] In addition, the air supply unit (20) according to the present embodiment can supply air to the air intake manifold (not shown) of the fuel cell stack (10), and the air supplied to the air intake manifold can be introduced into the air electrode (not shown) of the fuel cell cell (11) and discharged to the outside of the fuel cell stack (10) through the air exhaust manifold (not shown).

[0059] Here, the air supply unit (20) according to the present embodiment may include an air filter (21), an air blower (22), and a membrane humidifier (23).

[0060] In addition, the hydrogen supply unit (30) according to the present embodiment can supply hydrogen to the hydrogen inlet manifold (not shown) of the fuel cell stack (10), and the air supplied to the hydrogen inlet manifold can be introduced into the hydrogen electrode (not shown) of the fuel cell cell (11) and then introduced into the hydrogen discharge manifold (not shown).

[0061] As described above, hydrogen (H2) introduced into the hydrogen discharge manifold cannot be discharged outside the fuel cell stack (10) when the hydrogen discharge valve (HDB) is closed.

[0062] Here, the hydrogen supply unit (30) according to the present embodiment may include a hydrogen tank (31) and a hydrogen pressure control device (32) connected to the hydrogen tank (31).

[0063] Additionally, the cooling unit (40) according to the present embodiment may include a cooling fan (41) and a temperature sensor (42).

[0064] Here, the cooling fan (41) is a device that supplies cooling air to the fuel cell stack (10), and is installed facing the cooling air outlet (not shown) located on the opposite side of the cooling air inlet (not shown) of the fuel cell stack (10), so that cooling air can be sucked in from the cooling air inlet in the direction of the cooling air outlet.

[0065] In addition, a temperature sensor (42) is installed between the fuel cell stack (10) and the cooling fan (41), that is, between the cooling air outlet of the fuel cell stack (10) and the cooling fan (41), so as to measure the discharge temperature (CADT) of the cooling air discharged from the cooling air outlet.

[0066] The voltage measuring unit (50) according to this embodiment can measure the voltage of a fuel cell stack (10) that is being generated.

[0067] Here, the voltage measuring unit (50) may include a voltage measuring sensor (51) (see FIG. 3) installed adjacent to the hydrogen discharge port (11c) of each of the plurality of fuel cell cells and a voltage monitoring device (52) connected to the voltage measuring sensor (51).

[0068] The control unit (60) according to the present embodiment is connected to each of the fuel cell stack (10), air supply unit (20), hydrogen supply unit (30), cooling unit (40), and voltage measurement unit (50) to monitor and control the operating status of each device.

[0069] In addition, the control unit (60) according to the present embodiment can control the hydrogen discharge valve (HDB) so that the opening and closing of the hydrogen discharge valve is repeated at a hydrogen discharge valve opening and closing time interval (TI) until the hydrogen discharge valve (HDB) is closed and opened again.

[0070] As described above, if the fuel cell system is continuously operated with the hydrogen discharge valve (HDB) closed, hydrogen is not discharged outside the fuel cell stack, so moisture generated at the fuel cell air electrode may move to the hydrogen electrode, causing H2O flooding.

[0071] Therefore, by repeating the opening and closing of the hydrogen discharge valve (HDB) at the hydrogen discharge valve opening and closing time interval (TI) as in this embodiment, the H2O flooding phenomenon of the hydrogen electrode can be prevented.

[0072] Below, hydrogen purging by repeated opening and closing of the hydrogen discharge valve (HDB) according to the present embodiment and the hydrogen discharge valve opening and closing time interval (TI) for this purpose are described in detail.

[0073] FIG. 4 is a drawing schematically illustrating a hydrogen purge progress state in the air-cooled fuel cell system of the dead-end operation method of FIG. 2, and FIG. 5 is a drawing illustrating a hydrogen discharge valve opening / closing time interval in the hydrogen purge progress state in the air-cooled fuel cell system of the dead-end operation method of FIG. 4.

[0074] Referring to FIGS. 4 and 5, according to the present embodiment, when the hydrogen discharge valve (HDB) is repeatedly opened and closed at a hydrogen discharge valve opening / closing time interval (TI), a certain amount of hydrogen can be discharged outside the fuel cell stack (10) according to the opening and closing of the hydrogen discharge valve (HDB).

[0075] Here, the opening time of the hydrogen discharge valve (HDB) may be between 0.1 and 0.4 seconds. However, the opening time of the hydrogen discharge valve (HDB) is not limited thereto and may be adjusted depending on the operating conditions and environment of the fuel cell system.

[0076] In addition, the hydrogen discharge valve opening / closing time interval (TI) according to the present embodiment can be determined as described below based on the cooling air discharge temperature (CADT) measured by the temperature sensor (42) of the cooling unit (40) and the operating optimum temperature (AOT) of the fuel cell stack.

[0077] As illustrated in FIG. 5, when the discharge temperature (CADT) of the cooling air is lower than the operating temperature (AOT) of the fuel cell stack (10), the hydrogen discharge valve opening / closing time interval (TI) can be determined as the first hydrogen discharge valve opening / closing time interval (TI1).

[0078] In detail, as power generation progresses in the fuel cell stack (10), the exhaust temperature (CADT) of the cooling air gradually rises, and in the first hydrogen purge section (HP1) where the optimum operating temperature (AOT) of the fuel cell stack (10) and the exhaust temperature (CADT) of the cooling air become the same, the hydrogen discharge valve (HDB) is repeatedly opened and closed by the control unit (60) at the first hydrogen discharge valve opening and closing time interval (TI1) so that hydrogen (H2) can be discharged out of the fuel cell stack (10), thereby performing hydrogen purge.

[0079] Here, the operating temperature (AOT) of the fuel cell stack (10) and the first hydrogen discharge valve opening / closing time interval (TI1) can be set as the fuel cell stack (10) operating conditions of the control unit (60) using the inlet air pressure, inlet hydrogen pressure voltage, and the average voltage generated in the fuel cell stack (10).

[0080] For example, the operating temperature (AOT) of the fuel cell stack (10) according to the present embodiment may be 50°C, and the first hydrogen discharge valve opening / closing time interval (TI1) may be 6 seconds. However, the operating temperature (AOT) of the fuel cell stack (10) and the first hydrogen discharge valve opening / closing time interval (TI1) are not limited thereto and may be adjusted according to the operating conditions and environment of the fuel cell system.

[0081] Additionally, when the discharge temperature (CADT) of the cooling air exceeds the operating temperature (AOT) of the fuel cell stack, the hydrogen discharge valve opening / closing time interval (TI) can be determined as the second hydrogen discharge valve opening / closing time interval (TI2).

[0082] Specifically, as power generation progresses in the fuel cell stack (10), the discharge temperature (CADT) of the cooling air gradually rises and in the second hydrogen purge section (HP2) where the discharge temperature (CADT) of the cooling air exceeds the optimum operating temperature (AOT) of the fuel cell stack (10), the hydrogen discharge valve (HDB) is repeatedly opened and closed by the control unit (60) at the second hydrogen discharge valve opening and closing time interval (TI2) so that hydrogen (H2) can be discharged out of the fuel cell stack (10), thereby performing hydrogen purge.

[0083] Here, the second hydrogen discharge valve opening / closing time interval (TI2) can be set as a fuel cell stack (10) operating condition of the control unit (60) using the inlet air pressure of the fuel cell stack (10), the inlet hydrogen pressure voltage, and the average voltage generated in the fuel cell stack (10).

[0084] For example, the second hydrogen discharge valve opening / closing time interval (TI2) of the fuel cell stack (10) according to the present embodiment may be 4 seconds. However, the second hydrogen discharge valve opening / closing time interval (TI2) of the fuel cell stack (10) is not limited thereto and may be adjusted according to the operating conditions and environment of the fuel cell system.

[0085] The temperature rise of the fuel cell stack (10) in the power generation state is mainly due to the heat (exothermic reaction) generated during the chemical reaction of hydrogen and oxygen at the cathode of the fuel cell cell (11), and as the temperature of the fuel cell stack (10) rises, the amount of H2O produced at the cathode of the fuel cell cell (11) also increases.

[0086] Accordingly, as the amount of H2O produced at the air electrode of the fuel cell stack (10) increases, the H2O at the hydrogen electrode of the fuel cell cell (11) increases. Therefore, in an air-cooled fuel cell system of dead-end operation, the hydrogen purge interval must be shortened to reduce the H2O at the hydrogen electrode as the temperature of the fuel cell stack (10) increases.

[0087] According to the present embodiment, the hydrogen purge section can be divided into a first hydrogen purge section (HP1) in which hydrogen is purged at a first hydrogen discharge valve opening / closing time interval (TI1) and a second hydrogen purge section (HP2) in which hydrogen is purged at a second hydrogen discharge valve opening / closing time interval (TI2).

[0088] Here, since the discharge temperature (CADT) of the cooling air in the first hydrogen purge section (HP1) is lower than the optimum operating temperature (AOT) of the fuel cell stack (10), and the amount of H2O produced in the air electrode and the increase in H2O in the hydrogen electrode are smaller than in the second hydrogen purge section (HP2), the first hydrogen discharge valve opening / closing time interval (TI1) in the first hydrogen purge section (HP1) can be set to be greater than the second hydrogen discharge valve opening / closing time interval (TI2) in the second hydrogen purge section (HP2).

[0089] Therefore, according to the present embodiment, since the first hydrogen discharge valve opening / closing time interval (TI1) of the first hydrogen purge section (HP1) is greater than the second hydrogen discharge valve opening / closing time interval (TI2) of the second hydrogen purge section (HP2), the amount of hydrogen discharged in the first hydrogen purge section (HP1) may be less than the amount of hydrogen discharged in the second hydrogen purge section (HP2).

[0090] Ultimately, according to the present embodiment, the hydrogen purge section can be divided into a first hydrogen purge section (HP1) and a second hydrogen purge section (HP2) based on the operating optimum temperature (AOT) of the fuel cell stack (10) and the exhaust temperature (CADT) of the cooling air, and since the hydrogen purge interval can be lengthened in the first hydrogen purge section (HP1), the amount of hydrogen being discarded can be reduced, thereby minimizing the amount of hydrogen (H2) being discarded out of the fuel cell stack (10).

[0091] FIG. 6 is a schematic diagram illustrating an air-cooled fuel cell system of a dead-end operation type excluding a control unit according to a second embodiment of the present invention, and FIG. 7 is a schematic diagram illustrating hydrogen purge and air purge progress states in the air-cooled fuel cell system of the dead-end operation type of FIG. 6. In addition, FIG. 8 is a diagram illustrating a hydrogen purge section of a hydrogen purge and air purge progress state in the air-cooled fuel cell system of the dead-end operation type of FIG. 6.

[0092] Referring to FIG. 6, the dead-end operation type fuel cell system (200) according to the second embodiment of the present invention has the same configuration as the dead-end operation type fuel cell system (100) according to the first embodiment of the present invention, except for the air discharge line (ADL) in which the air discharge valve (ADB) is installed.

[0093] Therefore, a detailed description of the same configuration as the dead-end operation type fuel cell system (100) according to the first embodiment of the present invention is omitted below.

[0094] Referring to FIG. 6, the dead-end operation fuel cell system (200) according to the present embodiment may include an air discharge line (ADL) in which an air discharge valve (ADB) is installed.

[0095] The air discharge line (ADL) according to this embodiment is described in detail below.

[0096] Referring to FIGS. 7 and 8, the hydrogen purge mechanism outside the fuel cell stack (210) by repeating the opening and closing of the hydrogen discharge valve (HDB) opening and closing time interval (TI) of the hydrogen discharge valve of the fuel cell system (200) of the dead-end operation mode according to the present embodiment is the same as that of the fuel cell system (200) of the dead-end operation mode according to the first embodiment of the present invention, and therefore, a detailed description thereof will be omitted below.

[0097] As illustrated in FIG. 7, according to the present embodiment, when the discharge temperature (CADT) of the cooling air exceeds the operating temperature (AOT) and the operating limit temperature (LOT) of the fuel cell stack (10), the control unit can open the hydrogen discharge valve (HDB) and simultaneously close the air discharge valve (ADB) and increase the discharge pressure of the air blower (222) to allow a large amount of air to be discharged instantaneously through the air discharge manifold.

[0098] Here, the operating temperature (AOT) of the fuel cell stack (210) and the first hydrogen discharge valve opening / closing time interval (TI1) can be set as the fuel cell stack (210) operating conditions of the control unit (260) using the inlet air pressure, inlet hydrogen pressure voltage, and the average voltage generated in the fuel cell stack (210).

[0099] For example, the operating optimum temperature (AOT) of the fuel cell stack (210) according to the present embodiment may be 50°C, and the operating limit temperature (LOT) of the fuel cell stack (210) may be 55°C. However, the operating optimum temperature (AOT) and the operating limit temperature (LOT) of the fuel cell stack (210) are not limited thereto and may be adjusted according to the operating conditions and environment of the fuel cell system.

[0100] According to this embodiment, when the air discharge valve (ADB) is closed, air flowing out from the end of the air inlet manifold passes through the air electrode of the fuel cell cell (211) and is collected in the air discharge manifold, and at the same time, when the discharge pressure of the air blower (222) is increased, the amount of air flowing out through the air electrode of the cell (211) and into the air discharge manifold is instantaneously increased.

[0101] Accordingly, according to the present embodiment, when the air discharge valve (ADB) is closed and the discharge pressure of the blower (222) is increased, the amount of air passing through the cathode of the fuel cell cell (211) increases, so that the temperature of the fuel cell stack (210) decreases and air purge can be performed in which H2O on the cathode side of the fuel cell cell (211) is discharged to the outside.

[0102] In addition, according to the present embodiment, by lowering the rotation speed of the cooling fan (241) before opening the hydrogen discharge valve (HDB) and closing the air discharge valve (ADB), the temperature of the fuel cell stack (210) can be instantaneously increased, thereby making some of the H2O in the air electrode of the fuel cell cell (211) vaporized.

[0103] Afterwards, by closing the air discharge valve (ADB) as described above and performing air purge (Air Purge (AP)) on the air electrode of the fuel cell cell (211), the H2O in the air electrode can be easily removed by the air purge (Air Purge (AP)).

[0104] Referring to FIG. 8, according to the present embodiment, air purge (AP) may be performed at a point in time when the fuel cell stack (210) exceeds the operating limit temperature (LOT) in the 12th hydrogen purge section (HP12) after the 11th hydrogen purge section (HP11) in which the fuel cell stack (210) is operated at the AOT (Air Oven Temperature).

[0105] As illustrated in FIG. 8, when air purge is performed, the cooling air discharge temperature (CADT) decreases along with the temperature decrease of the fuel cell stack (210), so that at the start point of the 21st hydrogen purge section (HP21), the cooling air discharge temperature (CADT) may be lower than the fuel cell stack appropriate operating temperature (AOT) (Con1).

[0106] In addition, since the amount of H2O in the cathode of the fuel cell cell (211) decreases due to the air purge of the cathode of the fuel cell cell (211), the amount of H2O moving from the cathode of the fuel cell cell (211) to the hydrogen electrode also decreases, there may not be as much H2O in the hydrogen electrode of the fuel cell at the point where the 21st hydrogen purge section (HP21) starts as at the point where the 11th super purge group (HP11) starts.

[0107] Therefore, according to the present embodiment, since the cooling air discharge temperature (CADT) at the start point of the 21st hydrogen purge section (HP21) is lower than the fuel cell stack appropriate operating temperature (AOT) and the amount of H2O in the hydrogen electrode is not large, as in the 11th hydrogen purge section (HP11), the hydrogen purge (Hydrogen Purge (HP)) can be performed by making the hydrogen discharge valve opening / closing time interval for hydrogen purge in the 21st hydrogen purge section (HP21) the same as the 11th hydrogen discharge valve opening / closing time interval (TI11) in the 11th hydrogen purge section (HP11).

[0108] In addition, according to the present embodiment, hydrogen purge (Hydrogen Purge (HP)) can be repeatedly performed in a section where hydrogen purge (Hydrogen Purge (HP)) is performed at an interval equal to the 11th hydrogen discharge valve opening / closing time interval (TI11) and a section where hydrogen purge (Hydrogen Purge (HP)) is performed at an interval equal to the 12th hydrogen discharge valve opening / closing time interval (TI12).

[0109] In detail, when the fuel cell stack (210) exceeds the operating limit temperature (LOT) after the 21st hydrogen purge section (HP21) and the 22nd hydrogen purge section (HP22), air purge is performed again, and sections in which hydrogen purge is performed for the 11th hydrogen discharge valve opening / closing time interval (TI11) and the 12th hydrogen discharge valve opening / closing time interval (TI12) can be repeatedly created.

[0110] Therefore, according to the air-cooled fuel cell system (200) of the dead-end operation type according to the present embodiment, the amount of hydrogen discharged in the 11th hydrogen purge section (HP11) may be less than the amount of hydrogen discharged in the 12th hydrogen purge section (HP12) with the same hydrogen purge mechanism as in the air-cooled fuel cell system (100) of the dead-end operation type according to the first embodiment of the present invention.

[0111] In addition, as illustrated in FIG. 8, the hydrogen purge section consisting of the 11th hydrogen purge section (HP11) and the 12th hydrogen purge section (HP12) and the hydrogen purge section consisting of the 21st hydrogen purge section (HP21) and the 22nd hydrogen purge section (HP22) are continuously repeated as the air purge is repeatedly performed, so that the amount of hydrogen discarded by the 11th hydrogen purge section (HP11) and the 21st hydrogen purge section (HP21) can be minimized.

[0112] FIG. 9 is a block diagram of an air-cooled fuel cell system (300) of a dead-end operation mode according to a third embodiment of the present invention, and FIG. 10 is a schematic diagram of a dead-end operation mode fuel cell system excluding a control unit from the air-cooled fuel cell system of the dead-end operation mode of FIG. 9.

[0113] Referring to FIGS. 9 and 10, the air-cooled fuel cell system (300) of dead-end operation mode according to the third embodiment of the present invention has the same configuration as the air-cooled fuel cell system (100) of dead-end operation mode according to the first embodiment of the present invention and the current pulse unit (370).

[0114] Therefore, a detailed description of the same configuration as the dead-end operation type air-cooled fuel cell system (100) according to the first embodiment of the present invention is omitted below.

[0115] The current pulse unit (370) according to the present embodiment can apply a current pulse to the fuel cell stack (310).

[0116] In detail, when the second switch (S2) is switched to a closed state by the control unit (not shown), the current produced in the fuel cell stack (310) and drawn out to the external device (1) becomes a current pulse and can be applied to the fuel cell stack (310), and the current pulse applied to the fuel cell stack (310) can be a current that is twice or more the rated current.

[0117] Below, the influence on the fuel cell system according to the simultaneous or time-differenced progress of the hydrogen purge and current pulse unit (370) according to the present embodiment is described in detail.

[0118] FIG. 11 is a drawing schematically illustrating a state in which hydrogen purge and current pulse application are performed simultaneously in the air-cooled fuel cell system (300) of the dead-end operation method of FIG. 10, and FIG. 12 is a drawing illustrating a voltage state when hydrogen purge and current pulse application are performed simultaneously in the air-cooled fuel cell system of the dead-end operation method of FIG. 11.

[0119] As illustrated in FIG. 11, when the first switch (S1) of the fuel cell stack (310) is closed, the hydrogen discharge valve (HDB) is opened and hydrogen purging is performed, and at the same time, when the second switch (S2) is closed, a current pulse can be applied to the fuel cell stack (310) from the current pulse switch (370).

[0120] As illustrated in Fig. 12, when hydrogen purge and current pulse are performed simultaneously, the hydrogen purge voltage (HP1) due to the first hydrogen purge and the current pulse voltage (CP1) due to the current pulse can be generated simultaneously periodically in hydrogen purge voltage pulse sections (HPCPa, HPCPb) distinguished by the cooling air discharge temperature (CADT).

[0121] In the air-cooled fuel cell system (300) of dead-end operation mode according to the present embodiment, the hydrogen purge mechanism and the resulting effect are the same as those in the first to third embodiments of the present invention described above, so a detailed description thereof is omitted below.

[0122] Below, a detailed description is given of a mechanism for improving the performance of a fuel cell stack (310) by a current pulse applied to the fuel cell stack (310) from a current pulse unit (370) according to the present embodiment.

[0123] When the fuel cell stack (310) is in a normal state, a chemical reaction such as chemical formula 1 occurs at the hydrogen electrode of the fuel cell (311), and a chemical reaction such as chemical formula 2 occurs at the air electrode.

[0124]

[0125] (Chemical formula 1)

[0126] 2H2 -> 4H+ + 4e-

[0127]

[0128] (Chemical formula 2)

[0129] O2 + 4H+ + 4e- -> H2O + E + heat

[0130]

[0131] In addition, when a current pulse is applied to the fuel cell stack (310), oxygen (O2) (chemical formula 2) of the air electrode of the fuel cell cell (311) is consumed by the current pulse, and a hydrogen pumping phenomenon occurs in which H2 is generated instead of H2O.

[0132]

[0133] (Chemical formula 3)

[0134] O2 + 4H+ + 4e- + current pulse -> 2H2

[0135]

[0136] In this way, H2 generated at the cathode by the current pulse is a strong reducing agent, and the oxide film covering the surface of the catalyst at the cathode is removed by H2.

[0137] Therefore, according to the present embodiment, when a current pulse is applied to the fuel cell stack (310) by the current pulse unit (370), the oxide film of the platinum catalyst is removed, so that the performance of the air electrode of the fuel cell cell (311) can be improved.

[0138] However, as illustrated in FIG. 11, if hydrogen purging and current pulse application are performed simultaneously, a hydrogen shortage phenomenon may occur in the hydrogen electrode of the fuel cell cell (311). The cause of the hydrogen shortage phenomenon and the mechanism of the performance deterioration of the hydrogen electrode of the fuel cell cell (311) due to this phenomenon will be described in detail below.

[0139] As illustrated in Fig. 11, hydrogen from the hydrogen electrode of the fuel cell cell (311) is discharged to the outside by opening the hydrogen discharge valve (HDB) of the fuel cell stack (310).

[0140] Here, even while hydrogen purging is in progress, hydrogen is continuously supplied to the hydrogen electrode of the fuel cell cell (311) from the hydrogen supply unit (330), but the amount of hydrogen in the hydrogen electrode while hydrogen purging is in progress cannot but be less than the amount of hydrogen when hydrogen purging is not in progress.

[0141] As described above, since H2 is consumed as a reducing agent at the cathode of the fuel cell cell (311), the H2 at the cathode becomes insufficient, and the insufficient H+ is supplied from the hydrogen electrode of the fuel cell to the cathode.

[0142] Ultimately, if hydrogen purge and current pulse application are performed simultaneously, a hydrogen shortage phenomenon may occur at the hydrogen electrode of the fuel cell in proportion to the amount of H2 discharged by hydrogen purge and the amount of H2 consumed as a reducing agent at the air electrode.

[0143] Due to the lack of hydrogen in the hydrogen electrode, abnormal chemical reactions such as those in Chemical Formula 4 and Chemical Formula 5 below occur in the hydrogen electrode.

[0144]

[0145] (Chemical Formula 4)

[0146] 2H2O -> O2 + 4H+ + 4e-, E0 = 1.23V (water decomposition reaction)

[0147]

[0148] (Chemical formula 5)

[0149] C + 2H2O -> CO2 + 4H+ + 4e-, E0 = 1.4V (catalytic layer carbon corrosion, performance degradation)

[0150]

[0151] In detail, due to the lack of hydrogen in the hydrogen electrode of the fuel cell cell (311), a water decomposition reaction occurs at the hydrogen electrode (see Chemical Formula 4), the carbon of the catalyst layer is corroded, and heat generation due to an overvoltage of 1.4 V or more occurs, causing pinholes, etc., to form in the hydrogen electrode, which may damage the electrode.

[0152] Ultimately, if hydrogen purge and current pulse application are performed simultaneously on the fuel cell stack (310), the performance of the fuel cell cell (11), especially the hydrogen electrode, may deteriorate.

[0153] FIG. 13 is a drawing schematically illustrating a state in which a current pulse is applied to a fuel cell stack after hydrogen purging in the air-cooled fuel cell system of the dead-end operation type of FIG. 10, and FIG. 14 is a drawing schematically illustrating a hydrogen discharge valve opening / closing time interval, a first time interval in which a current pulse is applied, and a hydrogen purge section in a state in which a current pulse is applied to a fuel cell stack after hydrogen purging in the air-cooled fuel cell system of the dead-end operation type of FIG. 10.

[0154] Referring to FIGS. 13 and 14, the air-cooled fuel cell system (300) of the dead-end operation method according to the present embodiment can repeatedly apply a current pulse (Current Pulse (CP)) at a certain time point after hydrogen purge (Hydrogen Purge (HP)).

[0155] Here, the hydrogen purge mechanism and the effect thereof of the fuel cell cell (311) according to the opening of the hydrogen discharge valve according to the present embodiment are the same as the hydrogen purge mechanism and the effect thereof according to the first embodiment of the present invention, so a detailed description thereof is omitted.

[0156] According to this embodiment, hydrogen purging of the fuel cell cell (311) can be performed by opening the hydrogen discharge valve (HDB), closing the first switch, and opening the second switch.

[0157] In addition, the application of a current pulse from the current pulse unit (370) according to the present embodiment to the fuel cell stack (310) can be performed while the hydrogen discharge valve (HDB) is closed, the first switch (S1) is opened, and the second switch (S2) is closed.

[0158] While a current pulse is applied to the fuel cell stack (310), the external device (1) can be operated by being powered by the battery (380).

[0159] Referring to FIG. 14, the first hydrogen purge current pulse section (HPCP1) and the second hydrogen purge current pulse section (HPCP2) are the same as the hydrogen purge current pulse sections (HPCPa, HPCPb) described in FIG. 12, and the third hydrogen purge discharge time (TI3) and the fourth hydrogen purge discharge time (TI4) are the same as the first hydrogen purge discharge time (TI1) and the second hydrogen purge discharge time (TI2) described in FIG. 5, so a detailed description of the mechanism thereof is omitted.

[0160] According to the present embodiment, the control unit can block the current drawn out from the fuel cell stack (310) to the outside after the hydrogen discharge valve (HDB) is closed and the first time interval has elapsed, and apply a current pulse to the fuel cell stack (310) from the current pulse unit (370).

[0161] Here, the first time interval according to the present embodiment may include an eleventh time interval (TG11) and a twenty-first time interval (TG21).

[0162] As illustrated in Fig. 14, in the first hydrogen purge current pulse section (HPCP1), the second hydrogen pulse voltage (HP2) and the second current pulse (CP2) were generated at an 11th time interval (TG11).

[0163] Here, the 11th time interval (TG11) can be set as an operating condition of the fuel cell stack (310) of the control unit by measuring the time interval between the point at which the hydrogen purge of the fuel cell cell (311) is completed and the point at which the hydrogen purge voltage approaches the normal voltage and the amount of hydrogen supplied from the hydrogen supply unit (330) becomes stable.

[0164] For example, the 11th time interval (TG11) of the fuel cell stack (310) according to the present embodiment may be between 0.5 seconds and 1.5 seconds. However, the 11th time interval (TG11) of the fuel cell stack (310) is not limited thereto and may be adjusted according to the operating conditions and environment of the fuel cell system.

[0165] Additionally, in the second hydrogen purge current pulse section (HPCP2), the third hydrogen pulse voltage (HP3) and the third current pulse (CP3) were generated at the 21st time interval (TG21).

[0166] Here, the 21st time interval (TG21) can be set as an operating condition of the fuel cell stack (310) of the control unit by measuring the time interval between the point at which the hydrogen purge of the fuel cell cell (311) is completed and the point at which the hydrogen purge voltage approaches the normal voltage and the amount of hydrogen supplied from the hydrogen supply unit (330) becomes stable.

[0167] For example, the 21st time interval (TG11) of the fuel cell stack (310) according to the present embodiment may be between 0.5 seconds and 1.5 seconds. However, the 11th time interval (TG11) of the fuel cell stack (310) is not limited thereto and may be adjusted according to the operating conditions and environment of the fuel cell system.

[0168] Although the 11th time interval (TG11) and the 21st time interval (TG21) according to the present embodiment are described as being the same, the 11th time interval (TG11) and the 21st time interval (TG21) may be set to different time intervals depending on the operating conditions and environment of the fuel cell system.

[0169] Ultimately, if the hydrogen purge and current pulse application of the fuel cell cell (311) are performed at regular time intervals according to the present embodiment, the phenomenon of hydrogen shortage at the hydrogen electrode of the fuel cell cell (311) is prevented, and the performance of the fuel cell cell (311) is improved and its service life can be extended by removing the oxide film by the current pulse.

[0170] FIG. 15 is a block diagram of an air-cooled fuel cell system of dead-end operation mode according to a fourth embodiment of the present invention, and FIG. 16 is a diagram schematically illustrating a hydrogen purge and air purge progress state of the air-cooled fuel cell system of dead-end operation mode of FIG. 15 and a state in which a current pulse is applied to a fuel cell stack after the hydrogen purge and air purge progress.

[0171] In addition, Fig. 17 is a drawing schematically illustrating a hydrogen purge section after hydrogen purge, current pulse application to the fuel cell stack of Fig. 16, and air purge are sequentially performed.

[0172] Referring to FIGS. 15 to 17, the air-cooled fuel cell system (400) of dead-end operation mode according to the fourth embodiment of the present invention has the same configuration as the air-cooled fuel cell system (300) of dead-end operation mode according to the third embodiment of the present invention except for the air discharge line (ADL), air blower (422), and voltage measurement sensor (41), and therefore, a detailed description of the same configuration is omitted below.

[0173] In addition, the mechanism for purging hydrogen out of the fuel cell stack (10) by repeated opening and closing of the hydrogen discharge valve (HDB) of the dead-end operation type fuel cell system (400) according to the present embodiment and the mechanism for improving the fuel cell stack performance by a current pulse that is performed after a certain period of time after the hydrogen purging are the same as the mechanism of the dead-end operation type fuel cell system (300) according to the third embodiment of the present invention, and therefore, a detailed description thereof will be omitted below.

[0174] The fuel cell stack (410) according to the present embodiment may further include an air discharge line (ADL) having an air discharge valve (ADB) installed and connected to an air intake manifold.

[0175] Additionally, the air supply unit (420) may include an air blower (422) that supplies air to the fuel cell stack.

[0176] In addition, the voltage measuring unit (450) may include a voltage measuring sensor (not shown) installed adjacent to the hydrogen outlet (11c) of each of the plurality of fuel cell cells and a voltage monitoring device (452) connected to the voltage measuring sensor.

[0177] According to this embodiment, when the discharge temperature (CADT) of the cooling air exceeds the operating temperature (AOT) and the operating limit temperature (LOT) of the fuel cell stack (410), the control unit can open the hydrogen discharge valve (HDB) and simultaneously close the air discharge valve (ADB) and increase the discharge pressure of the air blower (22) to discharge a large amount of air instantaneously through the air discharge manifold.

[0178] Here, according to the present embodiment, the operating optimum temperature (AOT) and the operating limit temperature (LOT) of the fuel cell stack (410) can be set as the operating conditions of the fuel cell stack (210) of the control unit (260) using the inlet air pressure, the inlet hydrogen pressure voltage, and the average voltage generated in the fuel cell stack (210).

[0179] For example, the operating optimum temperature (AOT) of the fuel cell stack (410) according to the present embodiment may be 50°C, and the operating limit temperature (LOT) of the fuel cell stack (10) may be 55°C. However, the operating optimum temperature (AOT) and the operating limit temperature (LOT) of the fuel cell stack (410) are not limited thereto and may be adjusted according to the operating conditions and environment of the fuel cell system.

[0180] According to this embodiment, when the air discharge valve (ADB) is closed, air flowing out from the end of the air inlet manifold passes through the air electrode of the fuel cell cell (411) and is collected in the air discharge manifold, and at the same time, when the discharge pressure of the air blower (222) is increased, the amount of air flowing out through the air electrode of the cell (411) and into the air discharge manifold is instantaneously increased.

[0181] Accordingly, according to the present embodiment, when the air discharge valve (ADB) is closed and the discharge pressure of the blower (422) is increased, the amount of air passing through the cathode of the fuel cell cell (411) increases, so that the temperature of the fuel cell stack (410) decreases and air purge can be performed in which H2O on the cathode side of the fuel cell cell (411) is discharged to the outside.

[0182] In addition, according to the present embodiment, by lowering the rotation speed of the cooling fan (241) before opening the hydrogen discharge valve (HDB) and closing the air discharge valve (ADB), the temperature of the fuel cell stack (410) can be instantaneously increased, thereby making some of the H2O condensate of the air electrode of the fuel cell cell (411) vaporized.

[0183] Afterwards, by closing the air discharge valve (ADB) as described above and performing air purge on the air electrode of the fuel cell cell (11), the H2O in the air electrode can be easily removed by the air purge.

[0184] Referring to FIG. 17, according to the present embodiment, air purge may be performed at a point in time when the fuel cell stack (410) exceeds the operating limit temperature (LOT) in the 12th hydrogen purge current pulse section (HPCP12) after the 11th hydrogen purge current pulse section (HPCP11) in which the fuel cell stack (410) is operated at the AOT (Air Oven Temperature).

[0185] As illustrated in Fig. 17, when air purge is performed, the cooling air discharge temperature (CADT) decreases along with the temperature decrease of the fuel cell stack (410), so that the cooling air discharge temperature (CADT) may be lower than the fuel cell stack appropriate operating temperature (AOT) (Con2) at the start point of the 21st hydrogen purge current pulse section (HPCP21).

[0186] In addition, since the amount of H2O in the cathode of the fuel cell cell (411) decreases due to the air purge of the cathode of the fuel cell cell (411), the amount of H2O moving from the cathode of the fuel cell cell (411) to the hydrogen electrode also decreases, there may not be as much H2O in the hydrogen electrode of the fuel cell at the point where the 21st hydrogen purge current pulse section (HPCP21) starts as at the point where the 11th hydrogen purge current pulse section (HPCP11) starts.

[0187] Therefore, according to the present embodiment, since the cooling air discharge temperature (CADT) at the start point of the 21st hydrogen purge current pulse section (HPCP21) is lower than the fuel cell stack optimum operating temperature (AOT) and the amount of H2O in the hydrogen electrode is not large, as in the 11th hydrogen purge current pulse section (HPCP11), the hydrogen purge (Hydrogen Purge (HP)) can be performed by making the hydrogen discharge valve opening / closing time interval for hydrogen purge in the 21st hydrogen purge current pulse section (HPCP21) the same as the 11th hydrogen discharge valve opening / closing time interval (TI11) in the 11th hydrogen purge current pulse section (HPCP11).

[0188] In addition, according to the present embodiment, hydrogen purge (Hydrogen Purge (HP)) can be repeatedly performed in a section in which hydrogen purge (Hydrogen Purge (HP)) is performed at the same interval as the third hydrogen discharge valve opening / closing time interval (TI3) and the eleventh time interval (TG11) and in a section in which hydrogen purge (Hydrogen Purge (HP)) is performed at the same interval as the fourth hydrogen discharge valve opening / closing time interval (TI4) and the twenty-first time interval (TG21).

[0189] In detail, when the air purge is performed again at a point when the fuel cell stack (410) exceeds the operating limit temperature (LOT) after the 211th hydrogen purge section (HP211) and the 212th hydrogen purge section (HP212), a section in which hydrogen purge is performed for the 111th hydrogen discharge valve opening / closing time interval (TI111) and the 112th hydrogen discharge valve opening / closing time interval (TI112) can be repeatedly created.

[0190] Therefore, according to the air-cooled fuel cell system (400) of the dead-end operation type according to the present embodiment, the amount of hydrogen discharged in the 111th hydrogen purge section (HP111) may be less than the amount of hydrogen discharged in the 112th hydrogen purge section (HP112) with the same hydrogen purge mechanism as in the air-cooled fuel cell system (100) of the dead-end operation type according to the first embodiment of the present invention.

[0191] In addition, as illustrated in FIG. 17, since the hydrogen purge section consisting of the 111th hydrogen purge section (HP111) and the 112th hydrogen purge section (HP112) and the hydrogen purge section consisting of the 211th hydrogen purge section (HP211) and the 212th hydrogen purge section (HP212) are continuously repeated according to the repeated progress of the air purge, the amount of hydrogen discarded by the 111th hydrogen purge section (HP111) and the 211th hydrogen purge section (HP211) can be minimized.

[0192] Although the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. A fuel cell stack including a plurality of fuel cell cells and a hydrogen discharge line (HDL) having a hydrogen discharge valve (HDB) installed and connected to a hydrogen discharge manifold; An air supply unit for supplying air to the above fuel cell stack; A hydrogen supply unit that supplies hydrogen to the above fuel cell stack; A cooling unit including a cooling fan for supplying cooling air to the fuel cell stack and a temperature sensor installed between the fuel cell stack and the cooling fan for measuring the discharge temperature of cooling air discharged from the fuel cell stack; A voltage measuring unit for measuring the voltage of the above fuel cell stack; An air-cooled fuel cell system of dead-end operation, comprising: a control unit connected to each of the fuel cell stack, the air supply unit, the hydrogen supply unit, the cooling unit, and the voltage measurement unit, and controlling the opening and closing of the hydrogen discharge valve to be repeated at a hydrogen discharge valve opening and closing time interval until the hydrogen discharge valve is closed and opened again; 2. In paragraph 1, When the discharge temperature of the cooling air is lower than or equal to the operating temperature of the fuel cell stack, the hydrogen discharge valve opening / closing time interval is the first hydrogen discharge valve opening / closing time interval. When the discharge temperature of the cooling air exceeds the operating temperature of the fuel cell stack, the hydrogen discharge valve opening / closing time interval is the second hydrogen discharge valve opening / closing time interval. An air-cooled fuel cell system of dead-end operation, wherein the opening / closing time interval of the first hydrogen discharge valve is longer than the opening / closing time interval of the second hydrogen discharge valve.

3. In paragraph 2, The above fuel cell stack further includes an air exhaust line having an air exhaust valve installed and connected to an air intake manifold, The above air supply unit includes an air blower that supplies air to the fuel cell stack, A dead-end operation type air-cooled fuel cell system, wherein the voltage measuring unit includes a voltage measuring sensor installed adjacent to a hydrogen outlet of each of the plurality of fuel cell cells and a voltage monitoring device connected to the voltage measuring sensor.

4. In paragraph 3, The above control unit, If the exhaust temperature of the cooling air exceeds the operating temperature and operating limit temperature of the fuel cell stack, An air-cooled fuel cell system of dead-end operation that closes the air discharge valve at the same time as the hydrogen discharge valve is opened and increases the discharge pressure of the air blower to discharge a large amount of air to the air discharge manifold of the fuel cell stack.

5. In paragraph 1, An air-cooled fuel cell system of dead-end operation further comprising a current pulse unit for applying a current pulse to the fuel cell stack 6. In paragraph 5, The above control unit, An air-cooled fuel cell system of a dead-end operation mode in which the hydrogen discharge valve is closed and, after a first time interval, current drawn out from the fuel cell stack is blocked and the current pulse is applied to the fuel cell stack from the current pulse unit.

7. In paragraph 6, The above fuel cell stack further includes an air exhaust line having an air exhaust valve installed and connected to an air intake manifold, The above air supply unit includes an air blower that supplies air to the fuel cell stack, A dead-end operation type air-cooled fuel cell system, wherein the voltage measuring unit includes a voltage measuring sensor installed adjacent to a hydrogen outlet of each of the plurality of fuel cell cells and a voltage monitoring device connected to the voltage measuring sensor.

8. In paragraph 7, The above control unit, If the exhaust temperature of the cooling air exceeds the operating temperature and operating limit temperature of the fuel cell stack, An air-cooled fuel cell system of dead-end operation that closes the air discharge valve and increases the discharge pressure of the air blower while simultaneously opening the hydrogen discharge valve to discharge a large amount of air into the air discharge manifold of the fuel cell stack.

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