Fuel cell system and method for operating a fuel cell system

Abstract

The invention relates to a fuel cell system (100) having at least one fuel cell stack (101) and at least one air system (10), wherein in the at least one air system (10) an exhaust gas path (EGR, EGT), in particular an exhaust gas recirculation path (EGR) and / or an exhaust gas transfer path (EGT), is provided between a supply air path (11) to the at least one fuel cell stack (101) and an exhaust air path (12) from the at least one fuel cell stack (101) or from another fuel cell stack (101), wherein an EGR / EGT infeed point of the exhaust gas path (EGR, EGT) into the supply air path (11) is arranged downstream of an air filter (AF) and upstream of an air compression device (Comp), in particular a one-stage air compression device, wherein a thermal temperature control device (3, 4, 5, 6, 7, 8) is provided for a region (BB) in the supply air path (11) between the EGR / EGT infeed point and the air compression device (Comp).

Description

[0001] Description

[0002] title

[0003] Fuel cell system and method for operating a fuel cell system

[0004] The invention relates to a fuel cell system, a method for operating a corresponding fuel cell system, a corresponding computer program product and a corresponding control unit for carrying out a corresponding method.

[0005] State of the art

[0006] In vehicles (FCV, English for "Fuel Cell Vehicle") in which the drive energy is also supplied (among other things) by one or more fuel cell systems (FCS, English for "Fuel Cell System"), the oxidizing agent oxygen from the ambient air is generally used to react with hydrogen in the fuel cell to form water and / or water vapor and thus to supply electrical power through electrochemical conversion.

[0007] In some systems, exhaust gas recirculation (EGR) is used in the cathode path to recirculate part of the exhaust gas back into the supply air path, e.g. to deoxygenate the supply air of the stack cathode paths.

[0008] In some systems, an exhaust gas transfer (EGT) path is used to transfer a portion of the exhaust gas from one stack to the intake air path of another stack. Disclosure of the Invention

[0009] The present invention provides a fuel cell system with the features of the independent device claim. Furthermore, the invention provides a method for operating a corresponding fuel cell system, a corresponding computer program product, and a corresponding control unit for carrying out a corresponding method with the features of the independent claims. Features and details described in connection with the various embodiments and / or aspects of the invention naturally also apply in connection with the other embodiments and / or aspects, and vice versa, so that with regard to the disclosure of the individual embodiments and / or aspects, reference is or can always be made to each other.

[0010] The present invention provides according to the first aspect: a fuel cell system (may be referred to as system for short) with at least one (PEM) fuel cell stack (may also be referred to as (PEM) stack for short) and at least one air system.

[0011] In the at least one air system, an exhaust gas path, for example in the form of an exhaust gas recirculation path and / or an exhaust gas transfer path, is provided between an air supply path to the at least one fuel cell stack and an exhaust air path from the at least one fuel cell stack or from another fuel cell stack. An EGR / EGT inlet point of the exhaust gas path into the air supply path is arranged downstream of an air filter and upstream of a, in particular single-stage, air compression device (can also be referred to as a compressor for short).

[0012] According to the invention, a thermal temperature control device is provided for a region in the intake air path between the EGR / EGT inlet point and the air compression device. The fuel cell system (or system for short) can preferably be used for mobile applications, e.g., in vehicles, in particular fuel-powered vehicles, preferably in the commercial vehicle sector with high service life requirements. The fuel cell system can serve as the main energy supplier for a vehicle. Furthermore, the fuel cell system within the meaning of the invention can serve as an energy supply for a power take-off drive and / or an auxiliary drive of a vehicle, e.g., a hybrid vehicle. However, the fuel cell system can also be used for stationary applications, e.g., in generators.

[0013] The fuel cell system can comprise multiple fuel cell stacks (or stacks for short), each with multiple stacked fuel cells and the associated functional systems, including media systems (air or cathode system, fuel or anode system, cooling system) and an electrical system. Preferably, the fuel cell system can comprise multiple modules in the form of individual stacks with multiple stacked fuel cells.

[0014] The invention recognizes that water management in the membrane and thus also in the cathode path is essential during operation of a PEM stack. The membrane must be sufficiently moist to conduct protons. The risk of drying out is significantly high, especially in the cathode inlet area. Therefore, various humidification concepts exist, including

[0015] - Exhaust Gas Transfer (EGT)

[0016] During exhaust gas transfer or EGT, part of the moist stack exhaust gas is directed into the supply air path of another stack, so that a cross-stack transfer of the fluid takes place.

[0017] - Exhaust Gas Recirculation (EGR)

[0018] With exhaust gas recirculation (EGR), a portion of the moist stack exhaust gas is directed from the exhaust path into the intake air path (usually related to the same stack). With EGT and EGR, the oxygen content of the intake air can also be reduced (or a higher stack cathode gas mass flow can be achieved with a comparable oxygen content—with / without EGT or with / without EGR).

[0019] The following topology options are available for the EGR / EGT inlet point into the supply air path:

[0020] F1. downstream of the air filter and upstream of the air compression

[0021] F2. downstream of a first compressor stage or downstream of the air compression

[0022] The invention deals with case F1, i.e., the supply of the EGT / EGR fluid into the supply air path upstream of the air compression and downstream of the air compressor. In this case, the air compression device can be designed as a single-stage device.

[0023] The invention further recognizes that for cases of cold ambient conditions (close to 0°C and below), the risk of ice formation is high when moist EGT / EGR fluid is introduced from the exhaust path into the cold area in the supply air path upstream of the air compression device.

[0024] This can result in some negative effects:

[0025] - Undefined humidification and insufficient humidification of the supply air (cold supply air is very dry) and negative consequences for stack cathode entry (e.g. power loss, increased degradation)

[0026] - Danger of cross-sectional narrowing due to ice formation

[0027] - Undefined inflow into compressor

[0028] - Negative consequences for air compression (loss of efficiency, changes in surge limit, non-robust operation, etc.)

[0029] - Risk of component damage due to ice impact, e.g., on the compressor impeller or due to ice particles entering the gas bearings of the air compressor unit. The invention addresses these cases, which can occur in cold ambient conditions (close to 0°C and below) and where the risk of ice formation is high when moist EGT / EGR fluid is introduced from the exhaust path into the cold area in the intake air path upstream of the air compression device.

[0030] With the help of the invention, the negative effects described above can be reliably avoided.

[0031] For this purpose, it is proposed that the relevant area in the supply air path between the EGR / EGT inlet point and the air compression device is tempered, in particular, at least if necessary, warmed up.

[0032] For this purpose, the fuel cell system is designed with a thermal tempering device to temper the relevant area in the supply air path between the EGR / EGT inlet point and the air compression device, in particular to warm it up, at least if necessary.

[0033] One embodiment may provide for the temperature control device to be implemented by a thermal, in particular heat-conducting, rather than fluidic, coupling of the region to the air compression device. The thermal, in particular heat-conducting, rather than fluidic, coupling of the region to the air compression device can be implemented, for example, by heat-conducting connecting lines and / or pipe sections of the exhaust gas path, which can be provided at least in the region and which can be arranged on the air compression device, e.g., in the region of a compressor volute. During operation of the compressor, the region of a compressor volute can advantageously become warm. Thus, it can be advantageously achieved that the relevant region in the supply air path between the EGR / EGT inlet point and the air compression device is heated.

[0034] One embodiment may provide for the temperature control device to be implemented by integrating the region, particularly structurally, into the air compression device, for example, by integrating the region into a coolant jacket of the air compression device. This also advantageously allows the relevant region in the supply air path between the EGR / EGT inlet point and the air compression device to be temperature-controlled, particularly, at least if necessary, heated.

[0035] One embodiment can provide for the temperature control device to have a heater, e.g., an electric heater, for the area. This allows the area to be heated in a controllable manner and / or as needed. Furthermore, it can be provided that the heater can be switched on at temperatures below a threshold, e.g., 0°C, and / or that the heater can be switched off at temperatures above a threshold, e.g., 0°C, or another threshold, e.g., 4°C.

[0036] One embodiment may provide for the temperature control device to be implemented by a thermal, in particular heat-conducting, rather than fluidic, coupling of the region to a coolant circuit of the air compression device. This advantageously ensures that the relevant region in the supply air path between the EGR / EGT inlet point and the air compression device is temperature-controlled, in particular, at least if necessary, heated.

[0037] One embodiment may provide for the temperature control device to be implemented by a thermal, in particular heat-conducting, rather than fluidic, coupling of the region to a cooling air path for gas bearings of the air compression device. This also advantageously ensures that the relevant region in the supply air path between the EGR / EGT inlet point and the air compression device is temperature-controlled, in particular, at least if necessary, heated.

[0038] One embodiment can provide for the temperature control device to be implemented by a thermal, in particular heat-conducting, but not fluidic, coupling of the region to a bypass path between an air supply path and an exhaust air path of the at least one fuel cell stack. In this way, it can be achieved that the region can be heated in a controllable manner and / or as needed. Furthermore, it can be provided that at temperatures below a threshold, e.g., 0°C, a bypass mass flow and / or a compressor pressure ratio can be increased, at least temporarily, and / or that at temperatures above a threshold, e.g., 0°C, or another threshold, e.g., 4°C, an increased bypass mass flow and / or an increased compressor pressure ratio can be reset.

[0039] A further embodiment may provide for the temperature control device to be implemented by a thermal, in particular heat-conducting, rather than fluidic, coupling of the region to an intercooler and / or a coolant circuit of an intercooler (IC) for supply air. Thus, it can be advantageously achieved that the relevant region in the supply air path between the EGR / EGT inlet point and the air compression device is temperature-controlled, in particular, at least if necessary, warmed up.

[0040] A further embodiment may provide for the temperature control device to be implemented by a thermal, in particular heat-conducting, rather than fluidic, coupling of the region to a coolant circuit of the at least one fuel cell stack or of another fuel cell stack. This also advantageously allows the temperature control of the relevant region in the supply air path between the EGR / EGT inlet point and the air compression device, in particular, at least if necessary, to be warmed up.

[0041] According to a further aspect, the invention presents a method for operating a fuel cell system having at least one fuel cell stack and at least one air system, wherein an exhaust gas path, in particular an exhaust gas recirculation path and / or an exhaust gas transfer path, is provided in the air system between an air supply path to the at least one fuel cell stack and an exhaust air path from the at least one fuel cell stack or from another fuel cell stack, wherein an EGR / EGT inlet point of the exhaust gas path into the air supply path is arranged downstream of an air filter and upstream of a, in particular single-stage, air compression device. For this purpose, the method according to the invention provides that a region in the air supply path between the EGR / EGT inlet point and the air compression device is tempered, in particular, heated, at least if necessary.The method can achieve the same advantages described above in connection with the fuel cell system according to the invention. These advantages are incorporated herein by reference.

[0042] In particular, the invention can be used to:

[0043] - defined humidification of the supply air (cold supply air is very dry) can be achieved

[0044] - Loss of performance and degradation due to excessively dry air can be avoided

[0045] - Risk of cross-sectional narrowing due to ice formation is reduced

[0046] - Defined inflow into compressor can be achieved

[0047] - Efficiency loss during air compression, changes in the surge limit, non-robust operation, etc. can be avoided

[0048] - Risk of component damage due to ice impact, e.g. on the compressor impeller, or due to ice particles entering, e.g., the gas bearings of the air compressor unit, can be reduced

[0049] According to a further aspect, the invention provides a computer program product comprising instructions that, when executed by a computer, such as the processing unit of the control unit, cause the computer to perform the method, which can proceed as described above. Using the computer program product, 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.

[0050] A corresponding control unit provides a further aspect of the invention. A computer program in the form of code can be stored in a memory unit of the control unit. When executed by a computing unit of the control unit, the program performs a method that can proceed as described above. Using the control unit, 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.

[0051] A corresponding fuel cell system with a corresponding control unit provides a further aspect of the invention. Using the fuel cell system, the same advantages described above in connection with the method according to the invention can be achieved. These advantages are incorporated herein by reference.

[0052] Preferred embodiments:

[0053] The invention and its further developments, as well as their advantages, are explained in more detail below with reference to the accompanying drawings. They show schematically:

[0054] Figure 1 shows an example system topology,

[0055] Figure 2 shows another example system topology,

[0056] Figure 3 shows a proposed system topology,

[0057] Figure 4 shows a proposed system topology,

[0058] Figure 5 shows a proposed system topology,

[0059] Figure 6 shows a proposed system topology,

[0060] Figure 7 shows a proposed system topology, and

[0061] Figure 8 shows a proposed system topology,

[0062] In the various figures, identical parts of the invention are always provided with the same reference numerals, which is why they are generally described only once. Figures 3 to 8 serve to explain the inventive concept.

[0063] Figs. 3 to 8 show a fuel cell system 100 (may also be referred to as system for short) with at least one (PEM) fuel cell stack 101 (may also be referred to as (PEM) stack for short) and at least one air system 10.

[0064] In the at least one air system 10, an exhaust gas path EGR, EGT, for example in the form of an exhaust gas recirculation path EGR and / or an exhaust gas transfer path EGT, is provided between an air supply path 11 to the at least one fuel cell stack 101 and an exhaust air path 12 from the at least one fuel cell stack 101 or from another fuel cell stack 101.

[0065] An EGR / EGT inlet point of the exhaust gas path EGR, EGT into the supply air path 11 is arranged downstream of an air filter AF and upstream of a, in particular single-stage, air compression device Comp (can also be referred to as compressor for short).

[0066] According to the invention, a thermal tempering device 3, 4, 5, 6, 7, 8 is provided for a region BB in the supply air path 11 between the EGR / EGT inlet point and the air compression device Comp.

[0067] When operating a PEM stack, water management in the membrane and thus also in the cathode path is an important aspect. The membrane must be sufficiently humidified to conduct protons. The risk of drying out is particularly high in the cathode inlet area. Therefore, various humidification concepts exist, including:

[0068] - Exhaust Gas Transfer (EGT)

[0069] During exhaust gas transfer or EGT, part of the moist stack exhaust gas is directed into the supply air path of another stack, so that a cross-stack transfer of the fluid takes place (see Fig. 2).

[0070] Exhaust gas recirculation (EGR) During exhaust gas recirculation or EGR, part of the moist stack exhaust gas is directed from the exhaust path into the supply air path (usually related to the same stack) (see Fig. 1).

[0071] The following topology options are available for the EGR / EGT inlet point into the supply air path:

[0072] F1. downstream of the air filter and upstream of the air compression

[0073] F2. downstream of a first compressor stage or downstream of the air compression device

[0074] As illustrated in Figs. 1 and 2, the invention addresses case F1, i.e., the supply of the EGT / EGR fluid into the supply air path 11 upstream of the air compression Comp and downstream of the air compression. As indicated in Figs. 3 to 8, the air compression device Comp can be designed as a single-stage device.

[0075] The invention further recognizes that for cases of cold ambient conditions (close to 0°C and below), the risk of ice formation is high when moist EGT / EGR fluid is introduced from the exhaust path 12 into the cold area in the supply air path 11 upstream of the air compression device Comp.

[0076] The invention allows the following advantages to be achieved even in cold ambient conditions (close to 0°C and below):

[0077] - Risk of ice formation is reduced

[0078] - defined humidification of the supply air (cold supply air is very dry) can be achieved

[0079] - Loss of performance and degradation due to excessively dry air can be avoided

[0080] - Risk of cross-sectional narrowing due to ice formation is reduced

[0081] - Defined inflow into compressor can be achieved

[0082] - Efficiency loss during air compression, changes in the surge limit, non-robust operation, etc. can be avoided

[0083] - The risk of component damage due to ice impact, e.g. on the compressor impeller, or due to the entry of ice particles, e.g. into the gas bearings of the air compressor unit, can be reduced in this way. As Figs. 3 to 8 illustrate, it is proposed that the relevant area BB in the supply air path 11 between the EGR / EGT inlet point and the air compression device Comp is tempered, in particular, at least if necessary, heated.

[0084] The fuel cell system 100 is designed with a thermal tempering device 3, 4, 5, 6, 7, 8 in order to temper the relevant area BB in the supply air path 11 between the EGR / EGT inlet point and the air compression device Comp, in particular to heat it up, at least if necessary.

[0085] One embodiment (Fig. 3) can provide that the temperature control device 3, 4, 5, 6, 7, 8 is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the area BB to the air compression device Comp.

[0086] The thermal, in particular heat-conducting and not fluidic, coupling of the region BB to the air compression device Comp can be realized, for example, by heat-conducting connecting lines and / or pipe sections of the exhaust gas path EGR, EGT, which can be provided at least in the region BB and which can be arranged on the air compression device Comp, e.g., in the area of ​​a compressor volute. During operation of the compressor, the area of ​​a compressor volute can advantageously become warm.

[0087] An embodiment (Fig. 4) can provide that the temperature control device 3, 4, 5, 6, 7, 8 is realized by a, in particular structural, integration of the area BB in the air compression device Comp.

[0088] The integration, in particular structural, of the area BB in the air compression device Comp can be realized, for example, by integrating the area BB in a coolant jacket of the air compression device Comp.

[0089] An embodiment (Fig. 5) can provide that the tempering device 3,

[0090] 4, 5, 6, 7, 8 have a heater (HH), e.g., an electric one, for area (BB). This allows area (BB) to be heated in a controllable and / or demand-based manner. At temperatures below a threshold, e.g., 0 °C, the heater (HH) can be switched on. At temperatures above a threshold, e.g., 0 °C, or another threshold, e.g., 4 °C, the heater (HH) can be switched off.

[0091] An embodiment (Fig. 6) can provide that the temperature control device 3, 4, 5, 6, 7, 8 is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the area BB to a coolant circuit of the air compression device Comp.

[0092] An embodiment (Fig. 7) can provide that the temperature control device 3, 4, 5, 6, 7, 8 is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the area BB to a cooling air path for gas bearings of the air compression device Comp.

[0093] One embodiment (Fig. 8) can provide that the temperature control device 3, 4, 5, 6, 7, 8 is realized by a thermal, in particular heat-conducting, but not fluidic, coupling of the region BB to a bypass path 13 between a supply air path 11 and an exhaust air path 12 of the at least one fuel cell stack 101.

[0094] In this way, the zone (BB) can be heated in a controllable and / or demand-based manner. At temperatures below a threshold, e.g., 0 °C, a bypass mass flow and / or a compressor pressure ratio can be increased, at least temporarily. At temperatures above a threshold, e.g., 0 °C, or another threshold, e.g., 4 °C, an increased bypass mass flow and / or an increased compressor pressure ratio can be reduced.

[0095] A further embodiment (not shown) may provide that the temperature control device 3, 4, 5, 6, 7, 8 is implemented by a thermal, in particular heat-conducting and not fluidic, coupling of the region BB to an intercooler IC and / or a coolant circuit of an intercooler (IC) for supply air. A further embodiment (not shown) may provide that the temperature control device 3, 4, 5, 6, 7, 8 is implemented by a thermal, in particular heat-conducting and not fluidic, coupling of the region BB to a coolant circuit of the at least one fuel cell stack 101 or of another fuel cell stack 101.

[0096] A corresponding method for operating a corresponding fuel cell system 100 also represents an aspect of the invention.

[0097] For this purpose, the method according to the invention provides that an area in the supply air path between the EGR / EGT inlet point and the air compression device is tempered, in particular, at least if necessary, warmed up.

[0098] A corresponding computer program product and a corresponding control unit ECU for carrying out a corresponding method also represent aspects of the invention.

[0099] The above explanation of the embodiments describes the present invention exclusively by way of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically feasible, without departing from the scope of the present invention.

Claims

Claims 1. A fuel cell system (100) comprising at least one fuel cell stack (101) and at least one air system (10), wherein in the at least one air system (10) an exhaust gas path (EGR, EGT), in particular an exhaust gas recirculation path (EGR) and / or an exhaust gas transfer path (EGT), is provided between an air supply path (11) to the at least one fuel cell stack (101) and an exhaust air path (12) from the at least one fuel cell stack (101) or from another fuel cell stack (101), wherein an EGR / EGT inlet point of the exhaust gas path (EGR, EGT) into the air supply path (11) is arranged downstream of an air filter (AF) and upstream of a, in particular single-stage, air compression device (Comp), wherein a thermal tempering device is provided for a region (BB) in the air supply path (11) between the EGR / EGT inlet point and the air compression device (Comp). (3, 4, 5, 6, 7, 8) is provided 2. Fuel cell system (100) according to claim 1, wherein the temperature control device (3, 4, 5, 6, 7, 8) is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the region (BB) to the air compression device (Comp), in particular by heat-conducting connecting lines and / or pipe sections of the exhaust gas path (EGR, EGT), at least in the region (BB), to a structure of the air compression device (Comp), preferably in the region of a compressor volute.

3. Fuel cell system (100) according to claim 1 or 2, wherein the temperature control device (3, 4, 5, 6, 7, 8) is realized by a, in particular structural, integration of the region (BB) in the air compression device (Comp), in particular by means of an integration of the region (BB) in a coolant jacket of the air compression device (Comp).

4. Fuel cell system (100) according to one of the preceding claims, wherein the temperature control device (3, 4, 5, 6, 7, 8) has a, in particular electric, heater (HH) for the area (BB) in order to heat the area (BB) in a controllable manner and / or as required, in particular wherein at temperatures below a threshold, for example 0 °C, the heater (HH) can be switched on, and / or wherein at temperatures above a threshold, for example 0 °C, or another threshold, for example 4 °C, the heater (HH) can be switched off.

5. Fuel cell system (100) according to one of the preceding claims, wherein the temperature control device (3, 4, 5, 6, 7, 8) is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the region (BB) to a coolant circuit of the air compression device (Comp).

6. Fuel cell system (100) according to one of the preceding claims, wherein the temperature control device (3, 4, 5, 6, 7, 8) is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the region (BB) to a cooling air path for gas bearings of the air compression device (Comp).

7. Fuel cell system (100) according to one of the preceding claims, wherein the temperature control device (3, 4, 5, 6, 7, 8) is implemented by a thermal, in particular heat-conducting and not fluidic, coupling of the region (BB) to a bypass path (13) between an air supply path (11) and an exhaust air path (12) of the at least one fuel cell stack (101) in order to heat the region (BB) in a controllable and / or demand-oriented manner, in particular wherein at temperatures below a threshold, e.g. 0 °C, a bypass mass flow and / or a compressor pressure ratio can be increased, at least temporarily, and / or wherein at temperatures above a threshold, e.g. 0 °C, or another threshold, e.g. 4 °C, an increased bypass mass flow and / or an increased compressor pressure ratio can be reset.

8. Fuel cell system (100) according to one of the preceding claims, wherein the temperature control device (3, 4, 5, 6, 7, 8) is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the region (BB) to an intercooler (IC) and / or a coolant circuit of an intercooler (IC) for an air supply.

9. Fuel cell system (100) according to one of the preceding claims, wherein the temperature control device (3, 4, 5, 6, 7, 8) is realized by a thermal, in particular heat-conducting and not fluidic, coupling of the region (BB) to a coolant circuit of the at least one fuel cell stack (101) or of another fuel cell stack (101).

10. Method for operating a fuel cell system (100) with at least one fuel cell stack (101) and at least one air system (10), wherein in the air system (10) between an air supply path (11) to the at least one fuel cell stack (101) and an exhaust air path (12) from the at least one fuel cell stack (101) or from another fuel cell stack (101), an exhaust gas path (EGR, EGT), in particular an exhaust gas recirculation path (EGR) and / or an exhaust gas transfer path (EGT), is provided, wherein an EGR / EGT inlet point of the exhaust gas path (EGR, EGT) into the supply air path (11) is arranged downstream of an air filter (AF) and upstream of a, in particular single-stage, air compression device (Comp), wherein the method provides that a region (BB) in the supply air path (11) between the EGR / EGT inlet point and the air compression device (Comp) is temperature-controlled.

11. A computer program product comprising instructions which, when executed by a computer, cause the computer to perform a method according to claim 10.

12. Control unit (ecu), comprising a computing unit and a memory unit in which a code is stored which, when at least partially executed by the computing unit, carries out a method according to claim 10.

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