Method for operating a fuel cell system, and fuel cell system

Abstract

The invention relates to a method for operating a fuel cell system (100) comprising at least one fuel cell stack (11) in which an integrated coolant path (KM) is provided, a fuel cell stack cooling circuit (45) that constitutes a closed circuit in which a vehicle cooler (42) and the coolant path (KM) are provided, and an anode system (200) and a cathode system (300), wherein the anode system (200) is equipped with an anode system cooling circuit (54) that constitutes a closed circuit in which a coolant is recirculated, and the anode system cooling circuit (54) is equipped with a heat exchanger (50) and a water separator (30) such that coolant in the anode system cooling circuit (200) can control the temperature of the water separator (30).

Description

[0001] Description

[0002] Method for operating a fuel cell system; fuel cell system

[0003] The invention relates to a method for operating a fuel cell system having the features of the preamble of independent claim 1. Furthermore, the invention relates to a fuel cell system having the features of the preamble of independent claim 8.

[0004] State of the art

[0005] It is known from the prior art that fuel cell systems exist that have an anode system and a cathode system. The anode system consists of an anode supply line that supplies fuel to a fuel cell stack, and a recirculation line that recirculates anode exhaust gas to the anode supply line using a conveying unit. Furthermore, the cathode system consists of a cathode supply line, in which a compressor can be located, and a cathode outlet line through which cathode exhaust gas is conveyed from the cathode system into the exhaust system.

[0006] The waste heat from the fuel cell stack is dissipated via a fuel cell stack cooling circuit and can be released into the environment via a vehicle radiator. A coolant is recirculated in the fuel cell stack cooling circuit. The coolant is pumped through the fuel cell stack by a coolant pump. A 3-way valve ensures that the vehicle radiator can be partially or completely bypassed.

[0007]

[0008] The inventive method for operating a fuel cell system with the features according to independent claim 1 has the advantage that a water separator arranged within an anode system cooling circuit can be temperature-controlled in a reliable manner. The anode system cooling circuit represents a closed circuit in which a coolant recirculates, allowing the coolant to temperature-control the water separator.

[0009] Tempering occurs when the water separator is brought to a specific temperature and / or maintained at that temperature. Tempering also includes heating and cooling the water separator.

[0010] It is advantageous if the coolant of the anode system cooling circuit is additionally tempered via a heat exchanger in order to be able to specifically set a temperature in the heat exchanger.

[0011] Advantageously, the coolant of the anode system cooling circuit is heated by a heating element arranged in the anode system cooling circuit. This allows for rapid heating of the water separator, for example, in the event of expected icing of the water separator and / or during a freeze-start of the fuel cell system, in which the fuel cell system is started at a temperature below the freezing point of water.

[0012] It is advantageous if the anode system cooling circuit can be connected to the fuel cell stack cooling circuit, allowing the vehicle cooler of the fuel cell system cooling circuit to be coupled into the anode system cooling circuit. When the vehicle cooler is coupled into the anode system cooling circuit, the coolant of the anode system cooling circuit flows through it to control the coolant temperature, particularly to cool it. This represents an efficient way to control the coolant temperature. Furthermore, it is cost-effective because it utilizes a component already present in the fuel cell system. Furthermore, a space-saving design is ensured.

[0013] Advantageously, the coolant of the anode system cooling circuit does not flow through the coolant path of the at least one fuel cell stack when the vehicle radiator is coupled into the anode system. If the coolant of the anode system cooling circuit does not flow through the coolant path of the at least one fuel cell stack, the coolant of the anode system cooling circuit can be cooled more efficiently, since no waste heat from the fuel cell stack is introduced into the coolant of the anode system cooling circuit.

[0014] It is advantageous if the anode system cooling circuit can be connected to the fuel cell stack cooling circuit, so that the waste heat from the fuel cell stack can be transferred to the coolant of the anode system cooling circuit to heat the water separator. If the waste heat already present in the fuel cell system is transferred to the coolant of the anode system cooling circuit when needed, the efficiency of the fuel cell system is increased.

[0015] Advantageously, the coolant of the anode system cooling circuit can also flow partially through the fuel cell stack cooling circuit and at least partially through the coolant path of at least one fuel cell stack. This allows the coolant to partially absorb the waste heat from the fuel cell stack if necessary, and the introduction of waste heat from the fuel cell stack into the coolant of the anode system can be adjusted to the temperature control requirements.

[0016] The fuel cell system according to the invention comprises at least one fuel cell stack in which an integrated coolant path is arranged, as well as a fuel cell stack cooling circuit in which a vehicle radiator and a bypass 3-way valve are arranged, and a bypass line arranged parallel to the vehicle radiator. Furthermore, the fuel cell system according to the invention comprises an anode system in which an anode system cooling circuit is arranged, and a cathode system.

[0017] Advantageously, the fuel cell system according to the invention for carrying out the method according to the invention has a first connecting line that connects the anode system cooling circuit and the fuel cell stack cooling circuit. The first connecting line opens into the anode system cooling circuit upstream of a second coolant pump in the flow direction. The first connecting line opens into the fuel cell system cooling circuit downstream of the coolant path of the at least one fuel cell stack and the vehicle radiator.

[0018] Advantageously, the fuel cell system according to the invention for carrying out the method according to the invention has a second connecting line that connects the anode system cooling circuit and the fuel cell stack cooling circuit. The second connecting line opens downstream of the water separator arranged in the anode system cooling circuit. The second connecting line opens upstream of the bypass line into the fuel cell stack cooling circuit.

[0019] The fuel cell system according to the invention, with the first connecting line and the second connecting line, can specifically utilize the existing waste heat from the fuel cell stack to heat the coolant of the anode system cooling circuit. The fuel cell system according to the invention also allows the coolant of the anode system cooling circuit to be specifically cooled, so that the existing units and the existing temperature gradient between the anode system cooling circuit and the fuel cell stack cooling circuit are utilized to increase the efficiency of the fuel cell system, since active temperature control by corresponding units can be completely or partially dispensed with.

[0020] Advantageously, at least one first valve is arranged in the first connecting line and / or at least one second valve is arranged in the second connecting line. This allows the coolant of the anode system cooling circuit to flow more flexibly through the fuel cell stack cooling circuit, and the method according to the invention can be carried out more efficiently.

[0021] Advantageously, a third valve is arranged in the fuel cell stack cooling circuit between the second connecting line and the bypass line. This allows the coolant of the anode system cooling circuit to flow more flexibly through the fuel cell stack cooling circuit, and the method according to the invention can be carried out more efficiently.

[0022] The fuel cell system according to the invention can preferably be used for mobile applications, for example in vehicles, in particular fuel-powered vehicles. The fuel cell system according to the invention can serve as the main energy supplier for a vehicle. At the same time, however, it is also conceivable that the fuel cell system according to the invention can be a secondary drive and / or auxiliary drive of a vehicle, for example, a hybrid vehicle.

[0023] The fuel cell system according to the invention can also be used for stationary applications, for example, in generators. The fuel cell system according to the invention can comprise one or more stacks, each containing several stacked fuel cells and the associated functional systems, including a cathode system, an anode system, a cooling system, and an electrical system.

[0024] Description of the drawings

[0025] The fuel cell system according to the invention and the method according to the invention are explained in more detail below with reference to drawings with preferred embodiments

[0026] They show:

[0027] Fig. 1 shows a schematic topology of a fuel cell system according to a first embodiment and

[0028] Fig. 2 is a flow chart of the method according to the invention.

[0029] Figure 1 shows a schematic topology of a fuel cell system 100 with at least one fuel cell stack 11 and a fuel cell stack cooling circuit 45, an anode system 200 with an anode system cooling circuit 54 and a cathode system 300.

[0030] The cathode system 300 supplies a cathode chamber K with oxygen (O2) as a reactant. Oxygen is a component of air. By supplying air to the fuel cell system 100, oxygen is made available to the system as a reactant.

[0031] A cathode supply line 31 is arranged in the cathode system 300 and leads into the fuel cell stack 11. Oxygen is supplied to the fuel cell stack 11 via the cathode supply line 31.

[0032] A cathode compressor 33 is located within the cathode supply line 31. The cathode compressor 33 conveys air into the fuel cell stack 11. The cathode compressor 33 can be used to vary the air flow rate. Increasing the power of the cathode compressor 33 results in an increased air flow rate being supplied to the fuel cell stack 11 via the cathode supply line 31. Reducing the power of the cathode compressor 33 results in a reduced air flow rate being supplied to the fuel cell stack 11.

[0033] A cathode outlet line 32 is arranged in the cathode system 300. Gases, such as cathode exhaust gas and / or fluids, such as product water, are discharged from the cathode system 300 via the cathode outlet line 32.

[0034] The fuel cell stack cooling circuit 45 is arranged in the fuel cell system 100. The fuel cell stack cooling circuit 45, which represents a closed circuit, serves to control the temperature of the fuel cell stack 11 by flowing a coolant through an integrated coolant path KM of the fuel cell stack 11.

[0035] In the fuel cell stack cooling circuit 45, the coolant is recirculated by means of a first coolant pump 43. The first coolant pump 43 is arranged upstream of the integrated coolant path KM in the flow direction. A three-way bypass valve 41 can direct the coolant at least partially or completely past a vehicle radiator 42 via a bypass line 46. The bypass line 46 and the vehicle radiator 42 are arranged parallel to each other.

[0036] In the fuel cell cooling circuit, a third valve 44 is arranged between the bypass line 46 and the vehicle cooler 42.

[0037] At least one sensor can optionally be arranged in the fuel cell cooling circuit 45. The sensor can be arranged upstream of the coolant path KM and / or downstream of the coolant path KM.

[0038] The anode system 200 is arranged in the fuel cell system 100. The anode system 200 supplies an anode compartment A of the fuel cell stack 11 with a fuel or anode fluid, in particular hydrogen (H2), as a reactant. By supplying fuel to the anode compartment A, the fuel is made available to the fuel cell system 100 as a reactant. An anode supply line 22 is arranged in the anode system 200 and opens into the fuel cell stack 11. Fuel is supplied to the fuel cell stack 11 via the anode supply line 22.

[0039] The fuel supply to the fuel cell stack 11 can be superstoichiometric, so that the anode exhaust gas still contains fuel. To make the excess fuel from the anode exhaust gas available to the anode system 200 again, the anode exhaust gas is recirculated via a recirculation line 21 into the anode supply line 22.

[0040] A jet pump 26 is arranged in the anode supply line 22. The jet pump 26 is arranged between the anode supply line 22 and the recirculation line 21 and connects them to each other.

[0041] In an alternative embodiment, the jet pump 26 can be designed as a combined valve jet pump assembly 26. A combined valve jet pump assembly 26 typically includes a metering valve and a jet pump. The metering valve is firmly connected to the jet pump 26, for example, by means of a screw connection.

[0042] When the volume flow of the fuel supplied into the jet pump 26 increases, the volume flow of the anode exhaust gas into the anode feed line 22 also increases.

[0043] A recirculation conveying unit 25 is optionally arranged within the recirculation line 21. The recirculation conveying unit 25 can be a compressor configured as a blower, pump, and / or compressor.

[0044] The recirculation conveying unit 25 supports recirculation of the anode exhaust gas from the recirculation line 21 into the anode supply line 22.

[0045] The recirculation feed unit 25 can be used to vary the volume flow of the anode exhaust gas flowing from the recirculation line 21 into the anode feed line 22. Increasing the power of the recirculation feed unit 25 results in an increased volume flow of anode exhaust gas being supplied to the fuel cell stack 11 via the recirculation line 21. Reducing the power of the recirculation feed unit 25 results in a reduced volume flow of anode exhaust gas being supplied to the fuel cell stack 11.

[0046] A water separator 30 is arranged within the recirculation line 21.

[0047] The water separator 30 is arranged upstream of the optional recirculation conveyor unit 25 in the flow direction. The water separator 30 removes water from the anode exhaust gas.

[0048] The water separator 30 is equipped with a temperature sensor 29. The temperature sensor 29 measures a temperature of the water separator 30, which is available for the method according to the invention.

[0049] An anode outlet line 23 is arranged in the anode system 200. The anode outlet line 23 is connected to the recirculation line 21 via the water separator 30. Gases, such as anode exhaust gas, and / or fluids, such as product water, are discharged from the anode system 200 via the anode outlet line 23.

[0050] A drain valve 24 is arranged in the anode outlet line 23. When the combined drain valve 24 is opened, anode exhaust gas and / or product water are discharged from the anode system 200.

[0051] In an alternative embodiment, the drain valve 24 may also be designed as a combined purge / drain valve 24 to also remove anode exhaust gas from the anode system 200.

[0052] Anode system cooling circuit 54 is arranged in the anode system 200. This circuit represents a closed circuit in which a coolant recirculates. The water separator 30 is connected to and integrated into the anode system cooling circuit 54. The anode system cooling circuit 54 is connected to the water separator 30, which is arranged in the recirculation line 21.

[0053] Furthermore, a second coolant pump 49, a heat exchanger 50, and a fourth valve 48 are arranged in the anode system cooling circuit 54. In the illustrated embodiment of the fuel cell system 100 according to the invention, the fourth valve 48 is designed as a 3-way valve.

[0054] The second coolant pump 49 is arranged between the water separator 30 and the fourth valve 48. The second coolant pump 49 recirculates the coolant of the anode system cooling circuit 54.

[0055] The heat exchanger 50 can temper the coolant of the anode system cooling circuit 54 and is arranged between the water separator 30 and the fourth valve 48.

[0056] The heat exchanger 50 optionally has a heating element so that the coolant can be additionally heated if necessary, e.g., when freezing is expected.

[0057] The anode system cooling circuit 54 and the fuel cell stack cooling circuit 45 can be connected to each other via a first connecting line 51 and a second connecting line 52.

[0058] The first connecting line 51 is connected at one end to the anode system cooling circuit 54 via the fourth valve 48.

[0059] The first connecting line 51 opens at the other end between the coolant path KM of the at least one fuel cell stack 11 and the vehicle cooler 42 into the fuel cell system cooling circuit 45.

[0060] A first valve 47 is arranged within the first connecting line 51. In the illustrated embodiment, the first valve 47 is designed as a 3-way valve, so that the first connecting line 51 is divided into a first and a second section.

[0061] The first section of the first connecting line 51 opens between the coolant path KM of the at least one fuel cell stack 11 and the bypass 3-way valve 41. The second section of the first connecting line 51 opens between the bypass 3-way valve 41 and the vehicle radiator 42 into the fuel cell cooling circuit 45. The second connecting line 52 is connected at a first end between the water separator 30 and the heat exchanger 50 to the anode system cooling circuit 200.

[0062] The second connecting line 52 is connected to the fuel cell system cooling circuit 45 at a second end between the third valve 44 and the vehicle cooler 42.

[0063] A second valve 53 is arranged within the second connecting line 52.

[0064] A control unit 500 is provided to regulate and control all control-related processes in the fuel cell system 100. This also includes the processing of at least one measurement signal for executing the method according to the invention.

[0065] In an alternative embodiment, more than one fuel cell stack 11 can be arranged in the fuel cell system 100, without the execution of the method according to the invention being restricted thereby.

[0066] The method according to the invention can be carried out in a fuel cell system 100 in several fuel cell stacks 11 in parallel or sequentially.

[0067] Figure 2 shows an embodiment of the method according to the invention.

[0068] The method is started in a step S100.

[0069] In a step S200, it is checked whether temperature control of the water separator 30 is required.

[0070] If it is determined that no temperature control of the water separator 30 is required, a step S500 is executed in which the method according to the invention is terminated.

[0071] If it is determined that temperature control of the water separator 30 is required, step S300 is executed. In step S300, the water separator 30 is temperature controlled by the coolant that recirculates in the anode system cooling circuit 54.

[0072] Optionally, the heat exchanger 50 can control the temperature of the coolant of the anode system cooling circuit 54. The heat exchanger 50 can additionally have a heating element and thereby heat the coolant of the anode system cooling circuit 54.

[0073] In order to heat the water separator 30 by recirculating the coolant of the anode system cooling circuit 54, the third valve 44 of the fuel cell cooling circuit 45 and the first valve 47 are brought into a closed switching position so that the coolant of the anode cooling circuit 54 cannot flow into the fuel cell stack cooling circuit 45.

[0074] Furthermore, the fourth valve 48 is set to a switching position in which the coolant can recirculate within the anode system cooling circuit 54.

[0075] In a first alternative embodiment of the method according to the invention, the vehicle radiator 42 can be coupled into the anode system cooling circuit 54 for tempering, in particular for cooling, the coolant of the anode system cooling circuit 54 and can be flowed through by the coolant of the anode system cooling circuit 54.

[0076] In addition, it is possible that the coolant of the anode system cooling circuit 54 does not flow through the coolant path KM of the at least one fuel cell stack 11 when the vehicle cooler 42 is coupled into the anode system 200.

[0077] To couple the vehicle radiator 42 into the anode system cooling circuit 43, the third valve 44 is moved to a closed switching position and the second valve 53 is moved to an open switching position, so that the coolant of the anode system circuit 54 flows through the vehicle radiator 42 via the second connecting line 52. In addition, the bypass 3-way valve 41 has a switching position in which the coolant of the anode system cooling circuit 54 flows into the first connecting line 51.

[0078] The fourth valve 48 has a switching position in which the coolant in the anode system cooling circuit 54 flows from the first connecting line 51 via the fourth valve 48 toward the second coolant pump 49. The coolant pump 49 conveys the coolant so that the coolant flows through the water separator 30 and can control the temperature of the water separator 30.

[0079] In a second alternative embodiment of the method according to the invention, the waste heat of the fuel cell stack 11 can be transferred to the coolant of the anode system cooling circuit 54 in order to heat the water separator 30.

[0080] Optionally, it is possible for the coolant of the anode system cooling circuit 54 to flow through the fuel cell stack cooling circuit 45 and to flow at least partially through the coolant path KM of the at least one fuel cell stack 11.

[0081] In order to transfer the waste heat of the fuel cell stack 11 to the coolant of the anode system cooling circuit 54, the coolant flows through the second connecting line 52 via the open second valve 53 into the coolant circuit 45.

[0082] In the coolant circuit 45, the third valve 44 has an open switching position so that the coolant of the anode system cooling circuit 54 can flow through the open third valve 44 in the direction of the first coolant pump 43.

[0083] The coolant is pumped into the coolant path KM of at least one fuel cell stack 11 by means of the first coolant pump 43. The coolant of the anode system cooling circuit 54 then flows via the fuel cell stack cooling circuit 45 into the first connecting line 51.

[0084] When the bypass 3-way valve 41 is in the closed switching position, the coolant of the anode system cooling circuit 54 flows from the coolant path KM into the first section of the first connecting line 51.

[0085] The first valve 47 has a switching position in which the coolant of the anode system cooling circuit 54 flows in the direction of the fourth valve 48, so that the flow direction into the second section of the first connecting line 51 is blocked.

[0086] In another embodiment, the switching positions of the bypass 3-way valve 41 and the first valve 47 may deviate from the switching positions described above without impairing the implementation of the method according to the invention. From the first connecting line 51, the coolant flows via the fourth valve 48 into the anode system cooling circuit 54 and is pumped toward the water separator 30 by the second coolant pump 49 to heat the water separator 30.

[0087] In step S400, a check is made to determine whether an event triggering the end of the process has occurred. An event triggering the end of the process can be the exceeding of a specified time period. An event triggering the end of the process can also occur if the water separator has reached a specified temperature.

[0088] If no event triggering the end of the method has occurred, step S200 is executed again.

[0089] If an event triggering the end of the procedure has occurred, step S500 is executed.

[0090] In step S500, the method according to the invention is terminated.

[0091] In an alternative embodiment, it is also possible to carry out the method according to the invention with more than one fuel cell stack 11.

[0092] The method according to the invention can be carried out in a fuel cell system 100 in several fuel cell stacks 11 in parallel or sequentially.

[0093] The method can further be carried out at least in part by the control unit 500 of the fuel cell system 100. A computer program in the form of code can be stored in a memory unit of the control unit 500. When the code is executed by a computing unit of the control unit 500, the program performs a method that can proceed as described above. With the aid of the control unit 500, the same advantages can be achieved that were described above in connection with the method according to the invention. These advantages are incorporated herein by reference in their entirety.

[0094] The control unit 500 can be in communication with the sensors of the fuel cell system 100 in order to monitor the sensor values. The control unit 500 can control the actuators in the fuel cell system 100 in order to carry out the method accordingly. In addition, the control unit 500 can be connected to an external computing unit in a

[0095] Communication connection in order to outsource some process steps and / or calculations in whole or in part to the external computing unit.

[0096] According to a further aspect, the invention provides a computer program product comprising instructions which, when the computer program product is executed by a computer, such as the processing unit of the control unit 500, cause the computer to carry out the method, which can proceed as described above. Using the computer program product, the same advantages can be achieved as described above in connection with the method according to the invention and / or the control unit 500 according to the invention.

[0097] Advantages are fully referred to here.

Claims

Claims 1.) Method for operating a fuel cell system (100) with at least one A fuel cell stack (11) in which an integrated coolant path (KM) is arranged, comprising a fuel cell stack cooling circuit (45) which represents a closed circuit in which a vehicle cooler (42) and the coolant path (KM) are arranged, and comprising an anode system (200) and a cathode system (300), characterized in that an anode system cooling circuit (54) is arranged in the anode system (200), which represents a closed circuit in which a coolant recirculates, wherein a heat exchanger (50) and a water separator (30) are arranged in the anode system cooling circuit (54) so ​​that the coolant in the anode system cooling circuit (200) can control the temperature of the water separator (30). 2.) Method according to claim 1, characterized in that the coolant of the Anode system cooling circuit (200) is tempered via the heat exchanger (50). 3.) Method according to claim 1, characterized in that the coolant of the Anode system cooling circuit (200) is heated via a heating element arranged in the anode system cooling circuit (54). 4.) Method according to claim 1, characterized in that the anode system Cooling circuit (54) is connectable to the fuel cell stack cooling circuit (45), so that the vehicle cooler (42) of the fuel cell system cooling circuit (45) is coupled into the anode system cooling circuit (54) and is flowed through by the coolant of the anode system cooling circuit (54) in order to temper the coolant, in particular to cool it. 5.) Method according to claim 4, characterized in that the coolant of the Anode system cooling circuit (54) does not flow through the coolant path (KM) of the at least one fuel cell stack (11) when the vehicle cooler (42) is coupled into the anode system cooling circuit (54). Method according to claim 1, characterized in that the anode system Cooling circuit (54) is connectable to the fuel cell stack cooling circuit (45) so that the waste heat of the fuel cell stack (11) can be transferred to the coolant of the anode system cooling circuit (54) in order to heat the water separator (30). Method according to claim 6, characterized in that the coolant of the Anode system cooling circuit (54) flows through the fuel cell stack cooling circuit (45) and at least partially flows through the coolant path (KM) of the at least one fuel cell. A fuel cell system (100) comprising at least one fuel cell stack (11) in which an integrated coolant path (KM) is arranged, a fuel cell stack cooling circuit (45) in which a vehicle cooler (42) and a bypass 3-way valve (41) are arranged, and a bypass line (46) arranged parallel to the vehicle cooler (42), and an anode system (200) in which an anode system cooling circuit (54) is arranged, and a cathode system (300), for carrying out the method according to one of the above claims, characterized in that the fuel cell system (100) comprises: a first connecting line (51) connecting the anode system cooling circuit (54) and the fuel cell stack cooling circuit (45),so that the coolant from the fuel cell stack cooling circuit (45) can flow into the anode system cooling circuit (54) via the first connecting line (51), and a second connecting line (52) that connects the anode system cooling circuit (54) and the fuel cell stack cooling circuit (45), so that the coolant of the anode system cooling circuit (54) can flow into the fuel cell stack cooling circuit (45). Fuel cell system (100) according to claim 8, characterized in that at least one first valve (47) is arranged in the first connecting line (51) and / or at least one second valve (53) is arranged in the second connecting line (52). Fuel cell system (100) according to claim 8, characterized in that in the fuel cell coolant circuit (45) between the vehicle radiator (42) and, a third valve (44) is arranged in the first coolant pump (43), wherein the third valve (44) is arranged upstream of the first coolant pump (43) in the flow direction.

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