Fuel cell system with multiple fuel cell stacks and a method for operating a corresponding fuel cell system

Abstract

The invention relates to a fuel cell system (100) comprising at least one first fuel cell stack (S1) and a second fuel cell stack (S2), wherein the first fuel cell stack (S1) comprises a first coolant system (10) with a coolant pump (PmpCool), wherein the second fuel cell stack (S2) comprises a second coolant system (20) with a coolant pump (PmpCool), wherein the first coolant system (10) and the second coolant system (20) are fluidically connected to each other downstream of the coolant pumps (PmpCool) by a first connecting line (A), and wherein the first coolant system (10) and the second coolant system (20) are fluidically connected to each other upstream of the coolant pumps (PmpCool) by a second connecting line (B).wherein a coolant path through the first fuel cell stack (S1) of the first coolant system (10) and a coolant path through the second fuel cell stack (S2) of the first coolant system (20) are arranged between the first connecting line (A) and the second connecting line (B), and wherein at least one connecting valve (Vlink) is provided in the first connecting line (A) and / or in the second connecting line (B).

Description

The invention relates to a fuel cell system, having at least one first fuel cell stack and one second fuel cell stack. The invention further relates to a corresponding method for operating a corresponding fuel cell system. The invention furthermore relates to a corresponding computer program product and a corresponding control unit for carrying out a corresponding method.Prior ArtIn fuel cell systems (FCS) with one or more fuel cell stacks (or fuel cell stacks or stacks for short), the oxidizing agent oxygen from the ambient air is generally used to react with hydrogen to water or water vapor in the fuel cell and thus to supply an electrical power by electrochemical conversion.The waste heat is dissipated or the temperature control of a stack is usually carried out by a coolant system which contains a pump and valves and conducts the coolant flow via a cooler (or a plurality of) which are equipped with one or a plurality of cooler fans.In order to quickly warm up the coolant when starting the stack, the cooler (large cooling circuit) can be bypassed or bypassed, so that a small cooling circuit with little coolant mass (and thus also thermal mass) is formed.Disclosure of the InventionThe present invention provides a fuel cell system having the features of the independent system claim. Furthermore, the invention provides a corresponding method for operating a corresponding fuel cell system having the features of the independent method claim. Furthermore, the invention provides a corresponding computer program and a corresponding control unit for carrying out a corresponding method having the features of the subordinate claims. Features and details which are described in connection with the different 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 reference is or can always be made to the individual embodiments and / or aspects mutually.According to the first aspect, the present invention provides: a fuel cell system, having at least a first fuel cell stack and a second fuel cell stack. The first fuel cell stack has a first coolant system with a coolant pump and the second fuel cell stack has a second coolant system with a coolant pump. On the one hand, the first coolant system and the second coolant system are fluidically connected to one another downstream of the coolant pumps by a first connecting line. On the other hand, the first coolant system and the second coolant system are fluidically connected to one another upstream of the coolant pumps by a second connecting line. In this case, a coolant path through the first fuel cell stack of the first coolant system and a coolant path through the second fuel cell stack of the first coolant system are arranged between the first connecting line and the second connecting line. It is provided here that at least one connecting valve is arranged in the first connecting line and / or in the second connecting line.The fuel cell system in the sense of the invention can preferably be used for mobile applications, for example in vehicles, in particular fuel-driven vehicles. The fuel cell system in the sense of the invention can serve as a main energy supplier for a vehicle. At the same time, however, it is also conceivable that the fuel cell system in the sense of the invention can be an energy supply for a power take-off and / or an auxiliary drive of a vehicle, for example a hybrid vehicle. The fuel cell system in the sense of the invention can also be used for stationary applications, for example in generators.The fuel cell system in the sense of the invention can have a plurality of stacks, each with a plurality of stacked fuel cells and the associated functional systems, comprising: media systems (air or cathode system, fuel or anode system, cooling system) and an electrical system. Preferably, the fuel cell system in the sense of the invention can comprise a plurality of modules in the form of individual stacks with a plurality of stacked fuel cells.The invention recognizes that, on the one hand, there are systems that have a plurality of stacks with separate coolant systems (FIG. 1 ) or that there are systems that have a plurality of stacks and a common coolant system (FIG. 2 ).The invention also recognizes that the known systems lack redundancy and error operability (FIGS. 1, 2 ) or stack-specific controllability of thermodynamic variables (FIG. 2 ) or lack of possibilities for preheating a non-active stack with an active stack (FIG. 1 ) or modularity for usability in a modular unit (FIG. 2 ) or spreading for different operating ranges / operating modes (FIG. 2 ) or degrees of freedom for energy optimizations (FIGS. 1 and 2 ).The invention proposes a fuel cell system which can provide various topologies for coolant systems that can cover a wide range of requirements mentioned above.Coolant system topologies for multi-stack applications are thus made possible, which can provide different operating objectives and / or operating modes: A) a stack-specific operation with one assigned coolant pump each, B) an operation of two or more stacks with (only) one coolant pump in multiple and switchable operating modes.This can be achieved in particular by switchable coupling (transfer or connecting paths with valves), which can be used in B) and switched off in A), for example, or vice versa.The following requirements and / or advantages can thus be achieved:ready-to-operate in the event of a fault / redundancy,preheating another (non-active) stack by an active stack,degrees of freedom for energy optimization,spreading for different operating modes and operating ranges can be covered flexibly,setting stack inlet temperatures on a stack-specific basis,setting temperature changes on a stack individually,adjusting pressure levels of a coolant on a stack-specific basis,modular pump sizes and / or number of pumps / utilization or realization modular, etc.An advantageous coolant system topology can result if one, in particular only one, connecting valve is provided in the first connecting line, and if one, in particular only one, connecting valve is provided in the second connecting line. In this case, in particular each coolant system can have a cooler. In this way, an advantageous coolant system topology can be implemented with two simple connection valves.An advantageous coolant system topology can result if two connecting valves, in particular in the form of 3-way valves, are provided in the first connecting line, and if one, in particular only one, connecting valve is provided in the second connecting line. In this case, in particular each coolant system can have a cooler. In this way, an advantageous coolant system topology with two 3-way valves and a simple connection valve can be implemented.An advantageous coolant system topology can result if one, in particular only one, connecting valve is provided in the first connecting line, and if a common 3-way valve is provided in the second connecting line, wherein in particular the 3-way valve is designed to split a coolant flow between a coolant path through a cooler and between a cooler bypass. In this way, a further variant of coolant systems according to the invention can be realized, which can operate with only one cooler.An advantageous coolant system topology can result if two connecting valves, in particular in the form of 3-way valves, are provided in the first connecting line, and if a common 3-way valve is provided in the second connecting line, wherein in particular the 3-way valve is designed to split a coolant flow between a coolant path through a cooler and a cooler bypass. In this way, a further variant of coolant systems according to the invention can be realized, which can operate with only one cooler.An advantageous coolant system topology can result if one, in particular only one, connecting valve is provided in the first connecting line, and if one, in particular only one, connecting valve is provided in the second connecting line, and if the first coolant system and the second coolant system each have a 3-way valve, wherein in particular the 3-way valves are designed to divide a coolant flow between two coolant paths through a cooler and the respective cooler bypasses. In this way, a further variant of coolant systems according to the invention can be realized, which can operate with only one cooler.According to another aspect, the present invention provides: a method for operating a fuel cell system, which can be embodied as described above, wherein the at least one connecting valve in the first connecting line and / or in the second connecting line is operated in such a way that at least one operating requirement, preferably a plurality of operating requirements, preferably all operating requirements, of the following operating requirements can be realized with the aid of the coolant systems:Ctrl_TCoolSin:adjusting an inlet temperature of the coolant into the respective fuel cell stack on a stack-specific basis,Ctrl_dTCoolS:controlling a temperature change of the coolant in the respective fuel cell stack in a stack-specific manner,Ctrl_pStackSadjusting a pressure level of the coolant in the respective fuel cell stack in a stack-specific manner,FailOp:standby in the event of a fault and / or failure of a coolant pump,PreHeatOtherSpreheating a fuel cell stack, in particular not yet active, by another fuel cell stack, in particular active, in order in particular to condition the fuel cell stack, which has not yet been started, with a coolant, in particular preheated coolant, such that it is preferably possible to avoid the fuel cell stack having to be freeze-started, and such that degradation of the fuel cell stack is avoided,ModPmp:providing modularity in pump sizes and / or reduction in pump count and / or providing a modular construction for fuel cell systems with a variable number of fuel cell stacks and / or coolant systems,SpreadOp:spread for different operating modes and / or operating ranges, in particular comprising different operating states for a normal operation, a hot landing operation, cold start and / or freeze start, preferably comprising different operating ranges for an idle, a partial load and / or a full load,EnergyOpt:providing a selected operating mode with a degree of freedom for energy optimization, in particular comprising a minimization of a pump output, an increase of a system efficiency and / or a minimization of a consumption.Furthermore, it can be provided that at least one operating mode, preferably a plurality of operating modes, preferably all operating modes, can be realized by the following operating modes with the aid of the coolant systems:OpS1S2Pmp1 Pmp2:wherein both fuel cell stacks and both coolant pumps in both coolant systems are operated independently of one another, wherein the connecting valves remain closed,OpS1S2P1, OpS1S2Pmp2wherein both fuel cell stacks are operated, and wherein only one coolant pump is operated in a coolant system,OpS1Pmp1, OpS2Pmp2:wherein only one fuel cell stack is operated, and wherein only one coolant pump is operated in its coolant system, in particular so that the other fuel cell stack can be preheated,OpS1Pmp2, OpS2Pmp1:wherein only one fuel cell stack is operated, and wherein only one coolant pump is operated in a coolant system of the other fuel cell stack, such that, as an example, the other fuel cell stack can be preheated.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 arithmetic unit of the control unit, cause the computer to carry out the method which can be carried out as described above. With the aid of the computer program product, the same advantages can be achieved as described above in connection with the method according to the invention. These advantages are referred to in the present case in their entirety.A corresponding control unit provides a further aspect of the invention. A computer program in the form of a code can be stored in a memory unit of the control unit, which computer program, when the code is executed by a computing unit of the control unit, carries out a method which can be carried out as described above. With the aid of the control unit, the same advantages can be achieved as described above in connection with the method according to the invention. These advantages are referred to in the present case in their entirety.A corresponding fuel cell system with a corresponding control unit provides a further aspect of the invention. With the aid of the fuel cell system, the same advantages can be achieved as described above in connection with the method according to the invention. These advantages are referred to in the present case in their entirety.Preferred Embodiments:The invention and its developments and its advantages are explained in more detail below with reference to drawings. They show in each case schematically: FIG. 1 shows a known coolant system topology with separate coolant systems for each stack, FIG. 2 shows a known coolant system topology with a common coolant system for two stacks, FIG. 3 shows a coolant system topology in the sense of the invention with two simple connection valves Vlink-A and Vlink-B, FIG. 4 shows a coolant system topology in the sense of the invention with two 3-way valves Vlink-A1 and Vlink-A2 and a connecting valve Vlink-B, FIG. 5 shows a coolant system topology in the sense of the invention with only one vehicle radiator, FIG. 6 shows a further coolant system topology in the sense of the invention with only one vehicle radiator, and FIG. 7 shows an advantageous coolant system topology in the sense of the invention with only one vehicle radiator.In the different figures, identical parts of the invention are always provided with the same reference numerals, for which reason they are generally described only once.FIGS. 1 and 2 show known fuel cell systems 100*, 100**.FIG. 1 shows a topology of individual coolant systems 10*, 20* for tempering stacks S 1*, S 2*. A coupling between the coolant systems 10*, 20* of the individual stacks S 1*, S 2* is not provided here.FIG. 2 shows a topology of a common coolant system 10** for two stacks S 1*, S 2*, wherein a coolant pump HE supplies a plurality of S 1*, S 2*.The idea of the invention is illustrated by means of FIGS. 2 to 7. FIGS. 2 to 7 show a fuel cell system 100 which has a first fuel cell stack S 1 and a second fuel cell stack S 2. However, the fuel cell system 100 can also have a plurality of fuel cell stacks S 1, S 2 or, briefly, stacks S 1, S 2. The concept of the invention can be applied analogously to a fuel cell system 100 having a plurality of fuel cell stacks S 1, S 2.The fuel cell system 100 in the sense of the invention can preferably be used for mobile applications, for example in vehicles, in particular fuel-driven vehicles, and / or for stationary applications, for example in generators.As FIGS. 2 to 7 indicate, the stacks S 1, S 2 can have associated functional systems, comprising: media systems (air or cathode system, fuel or anode system, coolant system 10, 20) and an electrical system.As FIGS. 2 to 7 show, the first fuel cell stack S 1 has a first coolant system 10 with a coolant pump PmpCool. The second fuel cell stack S 2 has a second coolant system 20 with a coolant pump PmpCool.The coolant pumps PmpCool may be equipped, for example, with integrated check valves (if necessary, for example in order to prevent undesired secondary flows).As FIGS. 2 to 7 further show, the first coolant system 10 and the second coolant system 20 are fluidically connected to one another downstream of the coolant pumps PmpCool by a first connecting line A.As FIGS. 2 to 7 further show, the first coolant system 10 and the second coolant system 20 are fluidically connected to one another upstream of the coolant pumps PmpCool by a second connecting line B.The coolant paths through the stacks S 1, S 2 are arranged between the first connecting line A and the second connecting line B.As FIGS. 2 to 7 show, at least one connecting valve Vlink is arranged in the first connecting line A and / or in the second connecting line B.The invention recognizes that the known systems 100*, 100** (FIGS. 1, 2 ) lack redundancy and error operability (FIGS. 1, 2 ) or stack-specific controllability of thermodynamic variables (FIG. 2 ) or lack of possibilities for preheating a non-active stack with an active stack (FIG. 1 ) or modularity for usability in a modular unit (FIG. 2 ) or spreading for different operating ranges / operating modes (FIG. 2 ) or degrees of freedom for energy optimizations (FIGS. 1 and 2 ).The invention proposes a fuel cell system 100 having different topologies for coolant systems 10, 20, only some examples of which are shown in FIGS. 2-7, and which can cover a wide range of these requirements.The concept of the invention can be explained in detail with reference to FIG. 3.FIG. 3 shows an advantageous coolant system topology in which one, in particular only one, connecting valve Vlink-A is provided in the first connecting line A, and in which one, in particular only one, connecting valve Vlink-B is provided in the second connecting line B. In this case, in particular each coolant system 10, 20 can have a cooler HE. In this way, an advantageous coolant system topology can be implemented with two simple connection valves Vlink-A and Vlink-B.The proposed coupling allows different operating variants or operating modes (in particular with respect to operating modes of the coolant system) to be covered and therefore also the requirements mentioned to be covered.The present invention provides a method for operating a fuel cell system 100, which can be embodied as described above, wherein the at least one connecting valve Vlink is operated in the first connecting line A and / or in the second connecting line B in such a way that at least one operating requirement, preferably a plurality of operating requirements, preferably all operating requirements, of the following operating requirements can be realized with the aid of the coolant systems 10, 20, in particular by the topologies of FIGS. 3 and 4 :Ctrl_TCoolSin:Stack-Specific Adjustment of an Inlet Temperature of the Coolant KM into the Respective Fuel Cell Stack S1, S2,Ctrl_dTCoolS:Adjusting a temperature change of the coolant KM in a stack-specific manner into the respective fuel cell stack S 1, S 2,Ctrl_pStackSStack-specific adjustment of a pressure level of the coolant KM in the respective fuel cell stack S 1, S 2,FailOp:Operational readiness in the event of a fault and / or failure of a coolant pump PmpCool,PreHeatOtherSPreheating of an, in particular not yet active, fuel cell stack S 1, S 2 by another, in particular active, fuel cell stack S 1, S 2 in order in particular to condition the fuel cell stack S 1, S 2, which has not yet been started, with an, in particular preheated, coolant KM, such that it is preferably possible to avoid the fuel cell stack S 1, S 2 having to be freeze-started, and such that degradation of the fuel cell stack S 1, S 2 is avoided,ModPmp:providing modularity of pump sizes and / or reduction of a pump number and / or providing a modular unit for fuel cell systems 100 with a variable number of fuel cell stacks S 1, S 2 and / or on coolant systems,SpreadOp:spread for different operating modes and / or operating ranges, in particular comprising different operating states for a normal operation, a hot landing operation, cold start and / or freeze start, preferably comprising different operating ranges for an idle, a partial load and / or a full load,EnergyOpt:providing a selected operating mode with a degree of freedom for energy optimization, in particular comprising a minimization of a pump output, an increase of a system efficiency and / or a minimization of a consumption.Furthermore, at least one operating mode can be realized with the aid of the coolant systems 10, 20.OpS1S2Pmp1Pmp2:wherein both fuel cell stacks S 1, S 2 and both coolant pumps PmpCool in both coolant systems 10, 20 are operated independently of one another, wherein the connecting valve Vlink-A and the connecting valve Vlink-B remain closed.The connection valves Vlink-A and Vlink-B may remain closed.This operating mode OpS1S2Pmp1Pmp2 can preferably be used if high to medium load points are required for both stacks S1, S2.The coolant systems 10, 20 can then be regulated on a stack-specific basis and, in this operating mode OpS1S2Pmp1Pmp2, meet the requirements as the system in FIG. 1.Even in the case of required pressure differences between the stacks S 1, S 2, it is possible to switch over to this operating mode OpS 1S 2PMP 1PMP 2.Furthermore, at least one operating mode can be realized with the aid of the coolant systems 10, 20.OpS1S2P1, OpS1S2Pmp2wherein both fuel cell stacks S 1, S 2 are operated, and wherein only one coolant pump PmpCool is operated in a coolant system 10, 20.The operating mode OpS1S2Pmp1 may provide:The connection valves Vlink-A and Vlink-B are open. The coolant pump PmpCool in the second coolant system 20 is turned off.This operating mode OpS1S2Pmp1 can preferably be used if both stacks S1, S2 are operated at similar pressure levels at low to medium load points. Then, one coolant pump PmpCool (e.g., the coolant pump PmpCool in the second coolant system 20) can be turned off and the respective other coolant pump PmpCool (e.g., the coolant pump PmpCool in the first coolant system 10) can supply both stacks S 1, S 2.This operating mode OpS1S2Pmp1may also be applied when a coolant pump PmpCool(e.g., coolant pump PmpCoolin second coolant system 20) has a fault or even fails.Both stacks S 1, S 2 can continue to be operated.The operating mode OpS1S2Pmp2may provide:The connection valves Vlink-A and Vlink-B are open. The coolant pump PmpCoolin the first coolant system 10 is turned off.This operating mode OpS1S2Pmp2 can preferably be used if both stacks S1, S2 are operated at similar pressure levels at low to medium load points. Then, one coolant pump PmpCool (e.g., coolant pump PmpCool in first coolant system 10) can be turned off and the respective other coolant pump PmpCool (e.g., coolant pump PmpCool in second coolant system 20) can supply both stacks S 1, S 2.This operating mode OpS1S2Pmp1may also be applied when a coolant pump PmpCool(e.g., coolant pump PmpCoolin first coolant system 10) has a fault or even fails.Both stacks S 1, S 2 can continue to be operated.Furthermore, at least one operating mode can be realized with the aid of the coolant systems 10, 20.OpS1Pmp1, OpS2Pmp2:wherein only one fuel cell stack S 1, S 2 is operated, and wherein only one coolant pump PmpCool is operated in its coolant system 10, 20, in particular so that the other fuel cell stack S 1, S 2 can be preheated,The operating mode OpS1 Pmp1 can provide:The first stack S 1 is in operation and is operated with the first coolant system 10 and its coolant pump PmpCool.The second stack S 2 is off or on standby, as is the second coolant system 20 and its coolant pump PmpCool.The connection valves Vlink-A and Vlink-B are open or open depending on the sub-operation modes (OpS1Pmp1-TempS2 or OpS1Pmp1-NoTempS2)).If the second stack S 2 is to be warmed up in the switched-off state or kept warm in the standby state (temperature control S 2), then the connecting valves Vlink-A and Vlink-B can be open and / or preferably regulated and a part of the warmed-up coolant can be used to temperature control the second stack S 2.This allows the PreHeatOtherS request to be covered.If the second stack S 2 is not to be flowed through, then the connection valves Vlink-A and Vlink-B can remain.The operating mode OpS2P2may provide:The second stack 2 is in operation and is operated with the second coolant system 20 and its coolant pump PmpCool.The first stack S 1 is off or on standby, and also the first coolant system 10 and its coolant pump PmpCool.The connection valves Vlink-A and Vlink-B are open or open depending on the sub-operation modes (OpS2Pmp2-TempS1 or OpS2Pmp2-NoTempS1).If the first stack S 1 is to be warmed up in the switched-off state or kept warm in the standby state (temperature control S 1), then the connecting valves Vlink-A and Vlink-B can be open and / or preferably controlled and a part of the warmed-up coolant can be used to temperature control the first stack S 1.This allows the PreHeatOtherS request to be covered.If the first stack S 1 is not to be flowed through, then the connection valves Vlink-A and Vlink-B may remain.Furthermore, at least one operating mode can be realized with the aid of the coolant systems 10, 20.wherein only one fuel cell stack S 1, S 2 is operated, and wherein only one coolant pump PmpCool is operated in a coolant system 10, 20 of the other fuel cell stack S 1, S 2, in particular such that the other fuel cell stack S 1, S 2 can be preheated.The operating mode OpS1Mp2may provide:The first stack S 1 is in operation and is operated with the second coolant system 20 and its coolant pump PmpCool.The second stack S 2 is off or on standby, and also the first coolant system 10 and its coolant pump PmpCool.The connection valves Vlink-A and Vlink-B are open.The first stack S 1 is operated, but the second stack S 2 is not operated.This operating mode OpS1Pmp2can be used, for example, when the coolant pump PmpCoolin the first coolant system 10 fails.However, this operating mode OpS1Pmp2can also be used to temperature control the second stack S2and to operate the first stack S1.The operating mode OpS2P1may provide:The second stack S 2 is in operation and is operated with the first coolant system 10 and its coolant pump PmpCool.The first stack S 1 is off or on standby, as is the second coolant system 20 and its coolant pump PmpCool.The connection valves Vlink-A and Vlink-B are open.The second stack S 2 is operated, but the first stack S 1 is flowed through but not operated.This operating mode OpS2Pmp1may be applied when the coolant pump PmpCoolin the second coolant system 20 fails.However, this operating mode OpS2Pmp1can also be used to temperature control the first stack S1and to operate the second stack S2.A further coolant system topology is shown in FIG. 4, in which two connecting valves Vlink-A1, Vlink-A2, in particular in the form of 3-way valves, are provided in the first connecting line A, and in which one, in particular only one, connecting valve Vlink-B is provided in the second connecting line B. In this case, in particular each coolant system 10, 20 can have a cooler HE. In this way, an advantageous coolant system topology with two 3-way valves and a single connection valve Vlink-B can be implemented.A further advantageous coolant system topology is shown in FIG. 5, in which a, in particular only one, connecting valve Vlink-A is provided in the first connecting line A, and in which a common 3-way valve 3WV is provided in the second connecting line B, wherein in particular the 3-way valve 3WV is designed to divide a coolant flow between a coolant path through a cooler HE and between a cooler bypass HEby. In this way, a further variant of coolant systems according to the invention can be realized, which operate with only one cooler and thereby cover the requirements:Ctrl_TCoolSin:Stack-Specific Adjustment of an Inlet Temperature of the Coolant KM in the Respective Fuel Cell Stacks S1, S2,Ctrl_dTCoolS:Adjusting a temperature change of the coolant KM in the respective fuel cell stacks S 1, S 2 in a stack-specific manner,Ctrl_pStackSStack-specific adjustment of a pressure level of the coolant KM in the respective fuel cell stacks S 1, S 2.A further advantageous coolant system topology is shown in FIG. 6, in which two connecting valves Vlink-A1, Vlink-A2, in particular in the form of 3-way valves, are provided in the first connecting line A, and if a common 3-way valve 3WV is provided in the second connecting line B, wherein in particular the 3-way valve 3WV is designed to split a coolant flow between a coolant path through a cooler HE and a cooler bypass HEby. In this way, a further variant of coolant systems according to the invention can be realized, which operate with only one cooler and thereby cover the requirements:Ctrl_TCoolSin:Stack-Specific Adjustment of an Inlet Temperature of the Coolant KM in the Respective Fuel Cell Stacks S1, S2,Ctrl_dTCoolS:Adjusting a temperature change of the coolant KM in the respective fuel cell stacks S 1, S 2 in a stack-specific manner,Ctrl_pStackSStack-specific adjustment of a pressure level of the coolant KM in the respective fuel cell stacks S 1, S 2.A further advantageous coolant system topology is shown in FIG. 7, in which one, in particular only one, connecting valve Vlink-A is provided in the first connecting line A, and if one, in particular only one, connecting valve Vlink-B is provided in the second connecting line B, and if the first coolant system 10 and the second coolant system 20 each have a 3-way valve 3WV, wherein in particular the 3-way valves 3WV are designed to split a coolant flow between two coolant paths through a cooler HE and the respective cooler bypasses HEby. In this way, a further variant of coolant systems according to the invention can be realized, which operate with only one cooler and thereby cover the requirements:Ctrl_TCoolSin:Stack-Specific Adjustment of an Inlet Temperature of the Coolant KM in the Respective Fuel Cell Stacks S1, S2,Ctrl_dTCoolS:Adjusting a temperature change of the coolant KM in the respective fuel cell stacks S 1, S 2 in a stack-specific manner,Ctrl_pStackSStack-specific adjustment of a pressure level of the coolant KM in the respective fuel cell stacks S 1, S 2.A corresponding computer program product, a corresponding control unit ecu and a corresponding fuel cell system 100 with a corresponding control unit ecu represent further aspects of the invention.The foregoing explanation of the embodiments describes the present invention solely by way of examples. Of course, individual features of the embodiments can be freely combined with one another, insofar as technically expedient, without departing from the scope of the present invention.

Claims

Fuel cell system (100), comprising at least a first fuel cell stack (S1) and a second fuel cell stack (S2), wherein the first fuel cell stack (S1) comprises a first coolant system (10) with a coolant pump (PmpCool), wherein the second fuel cell stack (S2) comprises a second coolant system (20) with a coolant pump (PmpCool), wherein the first coolant system (10) and the second coolant system (20) are fluidically connected to one another downstream of the coolant pumps (PmpCool) by a first connecting line (A), wherein the first coolant system (10) and the second coolant system (20) are fluidically connected to one another upstream of the coolant pumps (PmpCool) by a second connecting line (B), wherein a coolant path through the first fuel cell stack (S 1) of the first coolant system (10) and a coolant path through the second fuel cell stack (S 2) of the first coolant system (20) are arranged between the first connecting line (A) and the second connecting line (B), and wherein at least one connecting valve (Vlink) is provided in the first connecting line (A) and / or in the second connecting line (B).Fuel cell system (100) according to Claim 1, wherein one, in particular only one, connecting valve (Vlink-A) is provided in the first connecting line (A), and wherein one, in particular only one, connecting valve (Vlink-B) is provided in the second connecting line (B).Fuel cell system (100) according to Claim 1 or 2, wherein two connecting valves (Vlink-A1, Vlink-A2), in particular in the form of 3-way valves, are provided in the first connecting line (A), and wherein one, in particular only one, connecting valve (Vlink-B) is provided in the second connecting line (B).Fuel cell system (100) according to one of the preceding claims, wherein one, in particular only one, connecting valve (Vlink-A) is provided in the first connecting line (A), and wherein a common 3-way valve (3WV) is provided in the second connecting line (B), wherein in particular the 3-way valve (3WV) is designed to divide a coolant flow between a coolant path through a cooler (HE) and a cooler bypass (HEby).Fuel cell system (100) according to one of the preceding claims, wherein two connecting valves (Vlink-A1, Vlink-A2), in particular in the form of 3-way valves, are provided in the first connecting line (A), and wherein a common 3-way valve (3WV) is provided in the second connecting line (B), wherein in particular the 3-way valve (3WV) is designed to split a coolant flow between a coolant path through a cooler (HE) and a cooler bypass (HEby).Fuel cell system (100) according to one of the preceding claims, wherein one, in particular only one, connecting valve (Vlink-A) is provided in the first connecting line (A), and wherein one, in particular only one, connecting valve (Vlink-B) is provided in the second connecting line (B), and wherein the first coolant system (10) and the second coolant system (20) each have a 3-way valve (3WV), wherein in particular the 3-way valves (3WV) are designed to split a coolant flow between two coolant paths through a cooler (HE) and the respective cooler bypasses (HEby).Method for operating a fuel cell system (100) according to one of the preceding claims, wherein the at least one connecting valve (Vlink) in the first connecting line (A) and / or in the second connecting line (B) is operated in such a way that at least one operating requirement, preferably a plurality of operating requirements, preferably all operating requirements, of the following operating requirements can be realized with the aid of the coolant systems (10, 20).Ctrl_TCoolSin:adjusting an inlet temperature of the coolant (KM) into the respective fuel cell stack (S 1, S 2) on a stack-specific basis,Ctrl_dTCoolS:controlling a temperature change of the coolant (KM) in a stack-specific manner in the respective fuel cell stack (S 1, S 2),Ctrl_pStackSadjusting a pressure level of the coolant (KM) in the respective fuel cell stack (S 1, S 2) in a stack-specific manner,FailOp:Operational readiness in the event of a fault and / or failure of a coolant pump (PmpCool),PreHeatOtherSpreheating a fuel cell stack (S 1, S 2), which is in particular not yet active, by another fuel cell stack (S 1, S 2), which is in particular active,ModPmp:providing a modularity of pump sizes and / or a reduction in a number of pumps and / or providing a modular unit for fuel cell systems ( 100) having a variable number of fuel cell stacks (S 1, S 2) and / or on coolant systems,SpreadOp:spreading for different operating modes and / or operating ranges,EnergyOpt:providing a selected mode of operation with a degree of freedom for energy optimization.Method according to the preceding claim, wherein at least one operating mode, preferably a plurality of operating modes, preferably all operating modes, can be realized by the following operating modes with the aid of the coolant systems (10, 20).OpS1S2Pmp1 Pmp2:wherein both fuel cell stacks (S1, S2) and both coolant pumps (PmpCool) in both coolant systems (10, 20) are operated independently of one another, wherein the connecting valve (Vlink-A) and the connecting valve (Vlink-B) remain closed,OpS1S2P1, OpS1S2Pmp2wherein both fuel cell stacks (S1, S2) are operated, and wherein only one coolant pump (PmpCool) is operated in a coolant system (10, 20),OpS1Pmp1, OpS2Pmp2:wherein only one fuel cell stack (S1, S2) is operated, and wherein only one coolant pump (PmpCool) is operated in its coolant system (10, 20), for example so that the other fuel cell stack (S1, S2) can be preheated,OpS1Pmp2, OpS2Pmp1:wherein only one fuel cell stack (S1, S2) is operated, and wherein only one coolant pump (PmpCool) is operated in a coolant system (10, 20) of the other fuel cell stack (S1, S2), for example so that the other fuel cell stack (S1, S2) can be preheated.A computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer program product to perform a method according to any preceding claim.Control unit (ecu), having a computing unit (cu) and a memory unit (mu) in which a code is stored which, when at least partially executed by the computing unit, carries out a method according to one of the preceding claims 1 to 8.

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