Fuel cell system with recirculation unit and method for operating

Abstract

The present invention relates to a fuel cell system (100) for regulating and / or controlling a fuel utilization (FU sys ) of the fuel cell system (100) and / or a fuel utilization (FU Stk ) of a fuel cell unit (101) of the fuel cell system (100). Furthermore, the invention relates to a corresponding method for operating a fuel cell system (100), a computer program product, a computer-readable data carrier, a control unit (FCCU), and a system (200).

Description

[0001] The invention relates to a method having the features of the independent method claim, a fuel cell system having the features of the independent device claim, a computer program product having the features of the independent patent claim relating to a computer program product, a computer-readable data carrier having the features of the independent patent claim relating to a computer-readable data carrier, a control unit having the features of the independent patent claim relating to a control unit, and a system having the features of the independent patent claim relating to a system.

[0002] Fuel cell systems, in particular solid oxide fuel cells, are known, comprising at least one fuel cell unit having an anode and a cathode and an electrolyte therebetween. A fuel gas, for example hydrogen or one comprising hydrogen (e.g. ammonia), can be supplied from the anode, and a further substance comprising oxygen, e.g. air, can be supplied from the cathode. The anode and cathode can be gas-permeable. The electrolyte represents an interface at which (separate) a reduction and an oxidation of a redox reaction take place. The redox reaction can comprise a reaction of oxygen with the fuel gas, e.g. hydrogen. There may be an excess of oxygen on the cathode side, while there may be a deficiency of oxygen on the anode side, since the oxygen reacts directly with hydrogen there. Due to the resulting concentration gradient, oxygen diffuses from the cathode to the anode.Since the electrolyte in between is only permeable to oxygen ions, the oxygen absorbs electrons there.

[0003] The resulting oxygen ions react with hydrogen ions on the anode side, which release electrons. During this exothermic reaction, an electron flow between the anode and cathode can be used externally as electrical power (current and / or voltage). Furthermore, fuel cell systems can comprise a stack of the fuel cell units described above.

[0004] However, devices and methods known from the prior art have disadvantages. For example, the electrical and / or thermal performance as well as the efficiency can be optimized. In particular, the fuel utilization of the fuel cell system (e.g. based on the overall system) and / or the fuel utilization of a fuel cell unit (of the fuel cell system, in particular based on just the fuel cell unit, e.g. stack) may be inadequate. Deposits, in particular carbon deposits, resulting from the fuel can affect performance, longevity and / or freedom from faults. Furthermore, diffusion losses and / or polarization losses can affect performance, efficiency, costs, longevity and / or freedom from faults. The cell voltage, in particular Nernst voltage, may be inadequate, which can in particular reduce the performance of a cell or a stack.The control and / or regulation of known devices may be inadequate. Excessive humidity, particularly at the anode or at the anode inlet, can also reduce performance and / or efficiency. This can also (potentially) lead to increased wear. The control and / or regulation of the fuel cell system can be optimized.

[0005] It is therefore an object of the present invention to at least partially overcome at least one of the disadvantages described above. In particular, the object of the invention is to provide an optimized fuel cell system and method that optimize performance, efficiency, longevity, trouble-free operation, and / or cost.

[0006] The above object is achieved by a method having the features of the independent method claim, a fuel cell system having the features of the independent device claim, a computer program product having the features of the independent patent claim relating to a computer program product, a computer-readable data carrier having the features of the independent patent claim relating to a computer-readable data carrier, a control unit having the features of the independent patent claim relating to a control unit, and a system having the features of the independent patent claim relating to a system. Further features and details of the invention emerge from the subclaims, the description, and the drawings.Features and details described in connection with the method according to the invention naturally also apply in connection with the fuel cell system according to the invention and / or in connection with the computer program product according to the invention and / or in connection with the computer-readable data carrier according to the invention and / or in connection with the control unit according to the invention and / or in connection with the system according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other. In particular, advantages described in the context of the first, second, third, fourth, fifth and / or sixth aspect also apply to the first, second, third, fourth, fifth and / or sixth aspect.

[0007] The above object is achieved according to a first aspect by a method for operating a fuel cell system, in particular a solid oxide fuel cell system, the fuel cell system comprising - at least one fuel cell unit for energy generation, comprising - having an anode path - an anode input for receiving an anode input current A in and - an anode output for outputting an anode output current A out , and - having a cathode path - a cathode input for receiving a cathode input current K in and - a cathode output for outputting a cathode output current K out , - a recirculation unit for regulating and / or controlling a humidity x H2O, Ain the anode input current A in the fuel cell unit, and / or a fuel utilization FU Stkthe fuel cell unit, - comprising the method - Controlling the fuel cell system to absorb the anode output current A out contained water vapor through a heat exchanger of the recirculation unit, whereby the heat exchanger is connected to the anode outlet A out is connected, - Controlling the recirculation unit to tap a specific portion r div the cathode input current K in by the recirculation unit for regulating and / or controlling the humidity of the anode input stream, and / or the fuel utilization FU Stk the fuel cell unit - Controlling the fuel cell system, in particular a hydrogen mass flow controller of the anode path, in order to adjust a volume flow of hydrogen in the anode path for controlling and / or regulating a fuel utilization of the fuel cell system.

[0008] In this case, operation can in particular comprise controlling and / or regulating, wherein preferably a control unit (see below) is used. The described actions or features of the method can be carried out in the order shown and in particular can be carried out repeatedly. Preferably, the method can be used to control and / or regulate a fuel cell system according to the second aspect. In this case, a control unit according to the fifth aspect can particularly preferably be used for controlling and / or regulating. In this case, the control unit can carry out the corresponding actions or features and / or carry out a control, in particular where technically expedient, in order to preferably implement the actions.

[0009] In this case, the control of the fuel cell system for receiving (in particular introducing) in the anode output current A outcontained water vapor through a heat exchanger of the recirculation unit, taking up from the anode output stream A out (total), which includes water vapor, which has been generated in particular inside the fuel cell unit. The anode output stream may also include (unreacted) hydrogen. By means of the recirculation unit for regulating and / or controlling a humidity x H2O, Ain the anode input current A in the fuel cell unit, the fuel utilization FU Sys of the fuel cell system, and / or the fuel utilization FU Stkthe fuel cell unit, the water vapor can be (at least partially) condensed. In other words, a humidity can preferably be set by the control unit. In this case, at least one target value can be specified for one, two, or all three parameters. The control unit can control and / or adjust the fuel cell system depending on the target value(s). For this purpose, the recirculation unit in particular can be controlled. This allows the condensation of water vapor to be influenced and / or adjusted. The condensation can in particular be carried out in the heat exchanger of the recirculation unit. The control unit can initiate or start the influence of substances in the fuel cell system.

[0010] The fuel cell unit can achieve a fuel utilization FU StkThis may in particular include a quantification of the proportion of fuel used, particularly relative to the fuel cell unit. The fuel cell system may have a fuel utilization FU Sys This may, in particular, include a quantification of the proportion of (efficiently) used fuel, particularly with respect to the fuel cell system.

[0011] For this purpose, the recirculation unit can be controlled to tap a certain proportion r div the cathode input current K in through the recirculation unit. Accordingly, the control unit can be configured to control the recirculation unit. This can initiate or start the tapping of the specific portion. For this purpose, the cathode path valve (see below) can be controlled in particular. Accordingly, it is advantageous to regulate and / or control the humidity (x H2O, Ain) of the anode input current, and / or the fuel utilization FU Stk the fuel cell unit.

[0012] For this purpose, the tapped cathode input current K in to the heat exchanger in order to cool the absorbed water vapor by the tapped cathode input current K in The tapped portion, which is fed to the heat exchanger of the recirculation unit, can be used to increase the anode output current A out and / or the water vapor is cooled. This allows the water vapor to condense (at least partially).

[0013] It is possible, in particular subsequently, to supply the absorbed water vapor to the anode input current A in through the heat exchanger, especially by feeding it to an anode path connection point. This allows the humidity x H2O, Ain the anode input current A ininfluenced, preferably reduced. In this way, the recirculation unit can adjust the humidity x H2O, Ain the anode input current A in influenced or adjusting the humidity x H2O, Ain the anode input current A in make possible..

[0014] The humidity x H2O, Ain the anode input current A in may include or represent a proportion of water, particularly water vapor. Preferably, the humidity, particularly at the anode inlet, should be adjustable and / or not excessively high. This allows the efficiency, robustness, and / or longevity of the fuel cell unit and / or the fuel cell system to be optimized.

[0015] It can be provided that at least one of the following setpoint values ​​is influenced, in particular set, by the recirculation unit and / or a control unit (see below), in particular by appropriate control: - Humidity xH2O, Ain the anode input current A in - Fuel utilization FU Sys of the fuel cell system - Fuel utilization FU Stk the fuel cell unit.

[0016] Preferably, the fuel utilization (FU Sys ) of the fuel cell system (100) and / or the fuel utilization (FU Stk ) of the fuel cell unit (101). The control unit can (respectively) specify corresponding target values, which can in particular be provided (externally) to the control unit by a user. The control unit can (thereupon) control the fuel cell system in order to set the target values ​​by controlling and / or regulating. In other words, the fuel cell system can be controlled such that the target values ​​are set, achieved, and / or realized.

[0017] The (target) fuel utilization FU Sysof the fuel cell system can be defined and / or calculated as (Equation 1): FUSys=I∗nc∗60∗VNorm2∗V˙H2in

[0018] In this case, I can be a current, in particular a current intensity, in particular a current drawn and / or generated by the fuel cell unit. This can be specified as a target current, in particular by the control unit, in particular as a function of a load operated by the fuel cell system and / or an inverter (of the fuel cell system). It is conceivable that the control unit, for example via a data connection, controls an inverter in order to produce, in particular to "draw", a (target) current specified by the control unit. In this case, n c a number of fuel cell units, for example n c = 1, for a fuel cell unit, or e.g. n c= 100, for a fuel cell system comprising (a stack of) 100 fuel cell units. V Norm comprise a standard volume which in particular is 22.41 NL mol -1 at 0°C and 1013.15 mbar. V̇ H2inthe (incoming or adjustable) volume flow of hydrogen, which can be adjusted in particular by a hydrogen mass flow controller, which can preferably be controlled by a control unit. Accordingly, for example, proactively to start the operation of the fuel cell system, the hydrogen mass flow controller can be adjusted by the control unit and / or the hydrogen valve can be opened. With a predetermined and / or constant current, the control unit can accordingly calculate a volume flow of hydrogen (in particular using equation 3) depending on a (target) fuel utilization of the fuel cell system, and in particular subsequently adjust it, preferably by controlling the hydrogen mass flow controller.

[0019] The (target) fuel utilization FU Stkof the fuel cell unit (or stack), especially when pure hydrogen is used as fuel, can be defined and / or calculated as: FUStk=I∗nc∗60∗VNorm2∗V˙H2in An in

[0020] V̇ H2 An in the (incoming or adjustable) volume flow of hydrogen at the anode inlet, especially in NL min -1 , which can be adjusted in particular as a function of a hydrogen mass flow controller and / or a recirculation rate r.

[0021] Within the scope of the invention, a volume flow, in particular designated by a point above a V (e.g. V̇ H2 An in), a volume flow rate, in particular a volume that passes per unit of time, for example, a cross-sectional area of ​​a pipe. Furthermore, it can be provided that forms and / or equations for specific values, e.g., a saturation steam temperature, can also be used to calculate corresponding actual values ​​and / or target values, e.g., an actual saturation steam temperature and / or target saturation steam temperature.

[0022] A recirculation rate r can be defined and / or calculated by: r=V˙loopV˙An out

[0023] In particular, the recirculation rate r can have a value in the range r = [0,1]. V̇ An out a volume flow at the anode outlet, especially in NL min -1 , Accordingly, the anode output current A out a volume flow at the anode outlet V̇ An,outbe characterized in particular by this. V̇ loop a returned volume flow, especially in NL min -1 , which can correspond in particular to the volume flow directed towards the anode heat exchanger. In other words, it can be provided that the returned volume flow V̇ loop is not fed into a burner.

[0024] The following relationship can be defined and / or calculated: FUStk=(1−r)∗FUSys1−r∗FUSys

[0025] The following relationship can be defined and / or calculated, especially by rearranging (equation 2): r=FUStk−FUSysFUSys∗(FUStk−1)

[0026] In this case, equation 2 can also be valid under and / or despite consideration of condensation of water (condensation of water vapor) in the anode path. In other words, it can be provided that even the condensation of water vapor in the heat exchanger does not affect the validity of equation 2. This can be taken into account during control and / or regulation, in particular during calculation, by the control unit. For a predetermined and / or calculated (target) fuel utilization of the fuel cell system, the control unit can calculate a recirculation rate (or vice versa) depending on a (target) fuel utilization of the fuel cell unit, and in particular subsequently adjust it, preferably by controlling the recirculation fan, the hydrogen mass flow controller, and / or the cathode path valve by a specific proportion r div the cathode input current K in to grab.

[0027] The tapping of a certain share r div the cathode input current K in through the recirculation unit can be described as follows. The following relationship can be defined and / or calculated: rdiv=V˙Air heat exchanger inV˙Air air filter out

[0028] V can Air Wärmetauseher in the (incoming or adjustable) volume flow of air at the inlet of the heat exchanger, especially in NL min -1 , which can be controlled and / or regulated in particular by adjusting the cathode path valve by the control unit, in particular by controlling and / or specifying a control value r div,SW for the cathode path valve. V̇ Air Luftfilter out the (outgoing or adjustable) volume flow of air at an outlet of the air filter, especially in NL min -1, which can be controlled and / or regulated in particular by adjusting the air filter (e.g. via an actuator) by the control unit.

[0029] It can be provided to set at least one of the setpoints by the recirculation unit and / or a control unit (see below), in particular by appropriate control, in particular by setting one of the following control variables: - Volume flow of hydrogen V̇ H2in , in particular by controlling and / or adjusting the hydrogen mass flow controller, - recirculating volume flow V̇ recy , in particular by controlling and / or adjusting the recirculation fan, - certain proportion r div the cathode input current K in , in particular by controlling and / or adjusting the cathode path valve.

[0030] The setpoints and / or manipulated variables can be provided, received, calculated and / or set by the control unit, in particular by controlling them via a corresponding data connection.

[0031] The following relationship can be defined and / or calculated (equation 3): V˙H2 in=I∗nc∗60∗VNorm2∗FUSys

[0032] Accordingly, the control unit can, in particular by controlling and / or regulating the volume flow of hydrogen V̇ H2in , the (target) fuel utilization FU Sysof the fuel cell system, in particular by adjusting it. It can be provided, in particular when the (target) fuel utilization of the fuel cell system, and in particular a (target) current, is specified, to (first) calculate the volume flow of hydrogen and, in particular, subsequently adjust the volume flow of hydrogen, in particular by controlling the hydrogen mass flow controller. The further (target) values ​​and / or manipulated variables can be calculated and / or adjusted based on the volume flow of hydrogen, the (target) current, and / or the fuel utilization of the fuel cell system.

[0033] In particular, based on the above definition for the recirculation rate r, the following relationship can be defined and / or calculated: r=V˙loopV˙An out

[0034] It can preferably be provided (in particular as an assumption) that the (electrochemical) reaction in the fuel cell unit (in particular the anode), in particular comprising the reaction of H2 with O 2- as reactants and water H2O as product, does not cause an increase in the molar flow. Consequently, the volume flow at the anode inlet and anode outlet can be maintained and / or equal. The recirculating volume flow V̇ recy can be fed into the anode inlet. The anode inlet current can be replaced by the recirculating volume flow V̇ recy are characterized and / or exhibit this.

[0035] Consequently, the following volume flows can be equal: V˙An out=V˙recy

[0036] It can be provided that the volume flow at the anode outlet V̇ An,out a volume flow of water (or water vapor) at the anode outlet V H2O,An,outin particular (as an assumption) the volume flow can primarily and / or exclusively comprise water (H2O).

[0037] As a result, the following can be obtained (equation 11): r=V˙loopV˙recy

[0038] This assumption may result in simplified and / or improved control and / or regulation, in particular calculation.

[0039] The following relationship can be defined and / or calculated by a mass flow balance at the heat exchanger, especially before the anode path connection point (equation 12): r=V˙recy−V˙H2 in+V˙CondV˙recy

[0040] In particular by forming, the following can be obtained (equation 13): V˙recy=V˙H2 in−V˙Cond1−r

[0041] In particular by inserting equation 2 and / or equation 3, the following can be obtained (equation 4): V˙recy=I∗nc∗60∗VNorm2∗FUSys−V˙Cond1−FUStk−FUSysFUSys∗(FUStk−1)

[0042] A volume flow V̇ Cond of (condensed) water (vapor), which can act as a disturbance variable, can be determined. This can be made possible by a sensor in the anode path outlet, which can be connected to the control unit, in particular, via a data connection. Particularly preferably, it can be provided (alternatively or additionally) to enable indirect measurement and / or determination, preferably by detecting an actual temperature t ist , in particular an actual saturation steam temperature t sat, ist, which can preferably be done via a temperature sensor, which can be arranged between the heat exchanger (preferably immediately thereafter) and the anode path connection point. The control unit can be configured to control the temperature sensor in order to perform a detection and / or transmit the measured temperature to the control unit. Alternatively or additionally, it can be provided to enable indirect measurement and / or determination, preferably by detecting an actual pressure p ist , in particular an actual saturation vapor pressure p sat, ist, which can preferably be carried out via a pressure sensor, which can be arranged between the heat exchanger (preferably immediately thereafter) and the anode path connection point. In this case, the control unit can be configured to control the pressure sensor in order to carry out a detection and / or to transmit the measured pressure to the control unit. It can be provided that in particular (as an assumption) the pressure in the fuel cell system is substantially uniform. It can preferably be assumed that pressure differences balance out quickly and thus a constant pressure can be assumed to be a good approximation. It can be provided that a pressure within the fuel cell system, in particular near a temperature sensor and / or pressure sensor, is substantially a normal pressure p normwhich can be, in particular, 1013 hPa (1013 mbar). Deviations can be neglected and / or taken into account by recording the (actual) pressure, for example via a pressure sensor (e.g., as the pressure used instead of the standard pressure). It may be particularly preferred to measure the actual pressure p ist , in particular the actual saturation vapor pressure p sat, ist , to be determined by a formula, in particular a Magnus formula: psat=MagnusFormula(tsat)

[0043] Accordingly, the saturation vapor pressure can be determined (solely) by temperature measurement and / or calculation. In this case, the following can apply, especially in reverse (Equation 6): tsat=MagnusFormula−1(xH2O,Ain∗pNorm1−V˙H2 inV˙recy)

[0044] Alternatively or additionally, calculation can also be carried out using a formula according to IAPWS-IF97, as disclosed in particular in: "Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam" (named as IAPWS-IF97).

[0045] In this case, based in particular on equation 6, a saturation steam temperature t sat depending on a normal pressure p norm , a humidity x H2O, Ain the anode input current A in , a volume flow of hydrogen V̇ H2in and / or a recirculating volume flow V̇ recy Particularly preferably, a target saturation steam temperature t sat, soll be determined: tsat, shall=MagnusFormula−1(xH2O, Ain, shall*pNorm1−V˙H2 inV˙recy)

[0046] Thus, starting from and / or depending on a desired target humidity x H2O, Ain, soll the anode input current Ain, a target saturation steam temperature t sat, soll It can also be determined depending on the target saturation steam temperature t sat, soll and an actual saturation steam temperature t sat, ist (by the control unit) a control value r div,SW for the cathode path valve. This allows the target humidity x H2O, Ain, soll the anode input current A in can be set by the control unit.

[0047] It can be provided (especially for the derivation of the above relationships) that the following relationship can be defined and / or calculated (equation 7): V˙H2O, On, out=[(V˙recy−V˙H2 in)*psatpNorm]+[I*nc*60*VNorm2*F]

[0048] V̇ H2O, An, out represent a volume flow of water (or water vapor) at the anode outlet. It can be assumed that (everywhere) in the fuel cell system the normal pressure p Normprevails. F can be the Faraday constant. The right-hand term (right square bracket) can represent the water generated at the anode, particularly in standard liters per minute. The left-hand term (left square bracket) can represent a volume flow of water or water vapor, particularly including water or water vapor that returns to the anode inlet via the recirculation unit.

[0049] Starting from equation 7, in particular due to division by V̇ recy , apply: xH2O, On, out=[(1−V˙H2 inV˙recy)*psatpNorm]+[I*nc*60*VNorm2*F*V˙recy]

[0050] Here, x H2O, An, out the water mole fraction (or water vapor mole fraction) at the anode outlet, in particular a humidity.

[0051] It can be considered as a volume flow balance at or in the heat exchanger, especially at a condensation point: (V˙recy−V˙H2 in)*psatpNorm+V˙Cond =V˙loop*[(1−V˙H2 inV˙recy)*psatpNorm+I*nc*60*VNorm2*F*V˙recy]

[0052] Using equation 11 and equation 12 we can get: (V˙recy−V˙H2 in)*psatpNorm+V˙Cond =[V˙recy−V˙H2 in+V˙Cond] *[(1−V˙H2 inV˙recy)*psatpNorm+I*nc*60*VNorm2*F*V˙recy]

[0053] By factoring out V̇ recy on the right we get: (V˙recy−V˙H2 in)*psatpNorm+V˙Cond =V˙recy*[1−V˙H2 inV˙recy+V˙CondV˙recy] *[(1−V˙H2 inV˙recy)*psatpNorm+I*nc*60*VNorm2*F*V˙recy]

[0054] By multiplying out V̇ recy on the right we get: (V˙recy−V˙H2 in)*psatpNorm+V˙Cond =[1+V˙Cond−V˙H2 inV˙recy] *[(V˙recy−V˙H2 in)*psatpNorm+I*nc*60*VNorm2*F]

[0055] By inserting equation 13 for V̇ recy surrendered: (V˙H2 in−V˙Cond1−r−V˙H2 in)*psatpNorm+V˙Cond =[1−1+r] *[(V˙H2 in−V˙Cond1−r−V˙H2 in)*psatpNorm+I*nc*60*VNorm2*F]

[0056] Furthermore, by transforming we get: V˙Cond*(1−psatpNorm*(1−r))+V˙H2 in*psatpNorm*(11−r−1) =r*[(V˙H2 in−V˙Cond1−r−V˙H2 in)*psatpNorm+I*nc*60*VNorm2*F] V˙Cond*(1−psatpNorm*(1−r))+V˙H2 in*psatpNorm*(11−r−1) =−V˙Cond*psatpNorm*r1−r+V˙H2 in*psatpNorm*r*(11−r−1) +r*I*nc*60*VNorm2*F V˙Cond*(1−psatpNorm*(1−r)+psatpNorm*11−r) =V˙H2 in*[psatpNorm*r*(11−r−1)−psatpNorm*(11−r−1)] +r*I*nc*60*VNorm2*F V˙Cond*[1−psatpNorm*(1−r)+(1−r)] =V˙H2 in*[psatpNorm*(11−r−1)*(r−1)]+r*I*nc*60*VNorm2*F V˙Cond*[1−psatpNorm]=−V˙H2 in*psatpNorm*r*(1−r)(1−r)+r*I*nc*60*VNorm2*F V˙Cond*[1−psatpNorm]=−V˙H2 in*psatpNorm*r+r*I*nc*60*VNorm2*F

[0057] With equation 1 for FU Sys follows: V˙Cond*[1−psatpNorm]=(1−psatpNorm*FUSys)*r*l*nc*60*VNorm2*F V˙Cond=r∗I∗nc∗60∗VNorm2∗F∗1−psatpNorm∗FUSys1−psatpNorm

[0058] Using equation 2 for r we get (equation 5): V˙Cond=FUStk−FUSysFUSys∗(FUStk−1)∗I∗nc∗60∗VNorm2∗F∗1−psatpNorm∗FUSys1−psatpNorm

[0059] Alternatively, the following can apply (equation 14): V˙Cond=V˙recy∗FUSys−psatpNorm1−psatpNorm

[0060] Accordingly, the volume flow of condensed water vapor can be calculated as a function of a (target) fuel utilization of the fuel cell system, a (target) fuel utilization of the fuel cell unit, a (target) current, and / or a saturation vapor pressure, which can be determined in particular as described above.

[0061] With equation 4 for V̇ recy follows (equation 5a): V˙recy=I∗nc∗60∗VNorm2∗FUSys−FUStk−FUSysFUSys∗(FUStk−1)∗I∗nc∗60∗V Norm2∗F∗1−psatpNorm∗FUSys1−psatpNorm1−FUStk−FUSysFUSys∗(FUStk−1)

[0062] Alternatively, especially with equation 14, the following can also apply (equation 15): V˙recy=r∗V˙H2 in1−r∗(1−FUSys−psatpNorm1−psatpNorm)

[0063] Thus, the recirculating volume flow can be adjusted by the control unit, in particular depending on the recirculation rate, the volume flow of hydrogen, the (target) fuel utilization of the fuel cell system, and / or the saturation vapor pressure.

[0064] Alternatively, the following can also apply (equation 16): V˙recy=r∗V˙H2 in−r∗V˙Cond1−r

[0065] Thus, the recirculating volume flow can be adjusted by the control unit, in particular depending on the recirculation rate, the volume flow of hydrogen, and / or the volume flow of condensed water vapor.

[0066] Furthermore, in particular by equation 15 and equation 3, it can be defined and / or calculated (equation 17): V˙recy=r∗I∗nc∗60∗VNormF∗2∗FUSys1−r∗(1−FUSys−psatpNorm1−psatpNorm)

[0067] Thus, the recirculating volume flow can be adjusted by the control unit, in particular depending on the recirculation rate, the saturation vapor pressure, the (target) current and / or the (target) fuel utilization of the fuel cell system.

[0068] The (target) humidity can be defined and / or calculated by (equation 18): xH2O An in=psatpNorm∗V˙recy∗(1−FUSys−psatpNorm1−psatpNorm)V˙recy∗(1−FUSys−psatpNorm1−psatpNorm)∗V˙H2 in

[0069] Thus, the humidity, in particular at the anode inlet, can be adjusted by the control unit, in particular depending on the recirculating volume flow, the saturation vapor pressure, the volume flow of hydrogen and / or the (target) fuel utilization of the fuel cell system.

[0070] Preferably, the control unit, in particular based on equation 18, can also determine the saturation vapor pressure as a function of the humidity, the atmospheric pressure, the recirculating volume flow, the saturation vapor pressure, the volume flow of hydrogen, the (target) current, the (target) fuel utilization of the fuel cell unit, and / or the (target) fuel utilization of the fuel cell system. In particular, it can be defined and / or calculated (equation 19): psat=f(pNorm,xH2O An in,FUSys,FUStk,I)

[0071] The control unit can calculate the saturation vapor temperature, particularly using a Magnus formula, depending on the humidity, the atmospheric pressure, the recirculating volume flow, the saturation vapor pressure, the hydrogen volume flow, the (target) current, the (target) fuel utilization of the fuel cell unit, and / or the (target) fuel utilization of the fuel cell system. In particular, the following can be defined and / or calculated (Equation 20): tsat=MagnusFormula−1(f(pNorm,xH2O An in,FUSys,FUStk,I))

[0072] The recirculation fan can be arranged in the recirculation unit, particularly between the anode path heat exchanger and the heat exchanger. In this case, different equations apply, which can, however, be derived analogously.

[0073] Equations 5 and 5a allow, in particular by the control unit, V̇ Cond and / or V̇ recyto be calculated, in particular depending on (actual values ​​and / or target values ​​for) the (target) fuel utilization FU Sys of the fuel cell system, the (target) fuel utilization FU Stk the fuel cell unit, a (target) current I, and / or a saturation vapor pressure p sat . It may therefore be particularly preferable to V̇ recy to calculate the saturation vapor temperature t sat , in particular a target saturation steam temperature t sat, soll , in order to advantageously determine a (desired) target humidity x H2O, Ain, soll the anode input current A inAlternatively or additionally, in particular using equation 5a, the control unit can calculate a recirculating volume flow as a function of a (target) fuel utilization of the fuel cell system and / or a (target) fuel utilization of the fuel cell unit, in particular as a function of the saturation vapor pressure. This can be set by controlling the recirculation blower by the control unit, in particular by controlling an actuator of the recirculation blower by the control unit. In this way, the target values ​​can be set by open-loop and / or closed-loop control. In this way, a (target) humidity, a (target) fuel utilization of the fuel cell system and / or a (target) fuel utilization of the fuel cell unit can be set.

[0074] Within the scope of the invention, it may be advantageous that the control of the recirculation unit for tapping a certain proportion r divthe cathode input current K in by the recirculation unit has at least one of the following features: - Controlling, by a control unit, a temperature sensor to detect an actual temperature t ist , in particular an actual saturation steam temperature t sat, ist , of the water vapor through the temperature sensor, - Transmission of the recorded actual temperature t ist , in particular an actual saturation steam temperature t sat, ist , from the temperature sensor to the control unit, - Provision, by the control unit, of a target humidity x H2O, Ain, soll the anode input current Ain , which preferably optimizes the performance of the fuel system, a target fuel utilization FU Sys,soll of the fuel cell system, and / or a target fuel utilization FU Stk,soll the fuel cell unit, - Calculating, by the control unit, a target temperature t soll, in particular a target saturation steam temperature t sat, soll , depending on the target humidity x H2O, Ain, soll , the target fuel utilization FU Sys,soll of the fuel cell system, and / or the target fuel utilization FU Stk,soll the fuel cell unit, - Providing, by the control unit, the target temperature t soll , in particular the actual saturation steam temperature t sat, soll , and the recorded actual temperature t ist , - Calculating, by the control unit, a control value r div,SW for a cathode path valve of the fuel cell system, in particular depending on a target temperature t soll , in particular an actual saturation steam temperature t sat, soll , and a recorded actual temperature t ist , - Adjustment, by the control unit, of the cathode path valve depending on the control value r div,SW to a certain proportion r divthe cathode input current K in preferably the humidity of the anode input current x H2O, Ain the target fuel utilization FU Sys,soll of the fuel cell system, and / or the target fuel utilization FU Stk,soll of the fuel cell unit, depending on the specific proportion r div the cathode input current K in is set, - Recording the specific proportion r div the cathode input current K in through the heat exchanger, in particular to achieve a saturation steam temperature t sat and / or a saturation vapor pressure p sat between the heat exchanger and the anode path connection point, preferably the humidity of the anode input stream x H2O, Ain the target fuel utilization FU Sys,soll of the fuel cell system, and / or the target fuel utilization FU Stk,soll of the fuel cell unit, depending on the saturation vapor temperature tsat is set, - at least partial return of the determined share r div the cathode input current K in from the heat exchanger into the cathode path, in particular from a second feeder of the heat exchanger into the cathode input stream K in via a cathode path connection point, wherein in particular alternatively to the return the certain portion r div the cathode input current K in is released directly into the environment, for example through an exhaust.

[0075] Within the scope of the invention, it is conceivable that, in particular following the activation of the recirculation unit for tapping, the following occurs: - Providing the tapped cathode input current (K in ) to the heat exchanger to cool the absorbed water vapor by the tapped cathode input current (K in), in particular the cooling has at least one of the following features: - at least partial condensation of the water vapor by the heat exchanger, in particular by a condensate separator, - Discharge of a volume flow of condensed water vapor V̇ Cond via an anode path outlet connected to the heat exchanger, in particular the condensate separator, wherein in particular the volume flow of condensed water vapor V̇ Cond is set by the control unit, depending on a target humidity x H2O, Ain, soll the anode input current Ain , a target fuel utilization FU Sys,soll of the fuel cell system, and / or a target fuel utilization FU Stk,soll the fuel cell unit.

[0076] It can be provided within the scope of the invention that the method comprises: - feeding the absorbed water vapor, in particular comprising (still contained) hydrogen, to the anode input stream (A in ) through the heat exchanger, in particular the supply of the absorbed water vapor to the anode input stream A in through the heat exchanger has at least one of the following features: - Mixing, in particular in an anode path connection point, a volume flow of hydrogen V̇ H2in with the water vapor supplied through the heat exchanger to create a recirculating volume flow V̇ recy to generate, whereby in particular the recirculating volume flow V̇ recy the anode input current A in corresponds.

[0077] It may be intended to supply pure hydrogen. This can optimize efficiency and / or longevity, particularly because less wear is generated. In particular, it may be intended to reduce the proportion of carbon molecules in the fuel and / or set it to zero (no carbon molecules). This can result in reduced and / or no carbon deposition, particularly in the anode circuit. This can improve longevity and / or efficiency. This can also increase fuel utilization. Stk of the fuel cell unit. This can enable a (comparatively) higher (target) fuel utilization of the fuel cell unit, which can preferably be adjusted according to the invention.

[0078] It is further conceivable that, in particular repeatedly, the fuel cell system is controlled and / or regulated by the control unit, in particular via a data connection, comprising at least one of the following features: - controlling and / or regulating a hydrogen valve, in particular to provide hydrogen in the anode path, - Controlling and / or regulating a hydrogen mass flow controller, in particular to control a volume flow of hydrogen V̇ H2in in the anode path, in particular the volume flow of hydrogen V̇ H2in is set by the control unit, depending on a target humidity x H2O, Ain, soll the anode input current Ain , a target fuel utilization FU Sys,soll of the fuel cell system, and / or a target fuel utilization FU Stk,soll the fuel cell unit, - Controlling and / or regulating a recirculation fan, in particular to generate a recirculating volume flow V̇ recy to be adjusted, whereby in particular the recirculating volume flow V̇ recy is set by the control unit, depending on a target humidity x H2O, Ain, soll the anode input current Ain , a target fuel utilization FU Sys,soll of the fuel cell system, and / or a target fuel utilization FU Stk,soll the fuel cell unit, - Controlling and / or regulating an air supply unit, - Controlling and / or regulating an air blower, - Controlling and / or regulating a burner, in particular the volume flow and the recirculation rate r being set by the control unit, depending on a target humidity x H2O, Ain, soll the anode input current Ain , a target fuel utilization FU Sys,soll of the fuel cell system, and / or a target fuel utilization FUStk,soll the fuel cell unit, - Controlling and / or regulating an air outlet.

[0079] The above object is further achieved according to a second aspect by a fuel cell system according to the invention, in particular a solid oxide fuel cell system, comprising - at least one fuel cell unit for energy generation, comprising - having an anode path - an anode input for receiving an anode input current A in and - an anode output for outputting an anode output current A out , and - having a cathode path - a cathode input for receiving a cathode input current K in and - a cathode output for outputting a cathode output current K out , - a recirculation unit for regulating and / or controlling a humidity x H2O, Ain the anode input current A inthe fuel cell unit, and / or a fuel utilization FU Stk the fuel cell unit, - wherein the recirculation unit comprises a heat exchanger connected to the anode outlet and configured to conduct in the anode outlet stream A out contained water vapor and then to the anode input current Ain , in particular at an anode path connection point, - wherein the recirculation unit is designed to recirculate a certain proportion r div the cathode input current K in to be tapped and made available to the heat exchanger, for the regulation and / or control of the fuel utilization FU Stk the fuel cell unit, and / or to reduce the absorbed water vapor by the specific proportion r div of the tapped cathode input current K in to cool.

[0080] The fuel cell unit can comprise one or more fuel cells, which can be arranged in a stack (e.g., a "stack"). Each fuel cell can comprise an anode and / or a cathode, with the anode being connected to the anode path and / or the cathode being connected to the cathode path. The fuel cell unit(s) can preferably comprise solid oxide fuel cells.

[0081] The fuel cell system or fuel cell unit can be used to generate energy, in particular by generating thermal and / or electrical energy or power. Thus, a current and / or voltage can be utilized, for example, for external devices. The fuel cell system preferably comprises an inverter, in particular a DC / AC converter. This can preferably be tapped via an anode electrode connected to the anode and a cathode electrode connected to the cathode.

[0082] The anode path can carry a material flow, in particular towards an anode inlet (see below). The anode path can also, at least in part, comprise a material flow from the anode outlet. The anode path can carry the anode inlet current A in and / or anode output current A out include, in particular, lead.

[0083] The anode input current A in (essentially) include the material flow from a hydrogen tank (in particular inlet into the system) to an anode inlet.

[0084] The anode inlet can be configured to receive an anode input current and, in particular, to guide it into the interior of the fuel cell unit.

[0085] The anode outlet can be configured to output an anode output current, in particular from the interior of the fuel cell unit. The anode output current comprises at least partially water, in particular water vapor.

[0086] The cathode path can carry a material flow, in particular towards a cathode inlet (see below). The cathode path can also, at least in part, comprise a material flow from the cathode outlet. The cathode path can carry the cathode inlet current K in and / or cathode output current Kout include, in particular, lead.

[0087] The cathode input current K in (essentially) include the material flow from an air supply unit (in particular inlet for air into the system) to a cathode inlet.

[0088] The cathode inlet can be configured to receive a cathode input current and, in particular, to lead into the interior of the fuel cell unit.

[0089] The cathode output may be configured to output a cathode output current, and in particular may lead from the interior of the fuel cell unit.

[0090] The fuel cell unit can comprise an electrolyte, in particular in the form of a membrane, along the sides of which the cathode path and the anode path or the corresponding material flows are guided, in order to preferably enable an (exothermic) redox reaction.

[0091] Unless otherwise stated, transport between different components of the fuel cell unit can be achieved through connecting units, such as pipes. This can enable material flow to operate the fuel cell system.

[0092] The recirculation unit can be included in the anode path, in particular forming part of the anode path. Preferably, the recirculation unit can be configured to regulate and / or control the humidity of the anode input stream and / or the fuel utilization FU. Stk of the fuel cell unit. The recirculation unit comprises a heat exchanger that is connected to the anode outlet (directly or at least indirectly). This allows the heat exchanger to convert the anode outlet current A out completely or at least partially and then subjected to the anode input current Ain, especially at an anode path connection point. The heat exchanger in the anode output stream A out absorb the water vapor contained in it and then add it to the anode input current Ain , in particular at an anode path connection point. This can create a circuit in which (at least partially) the anode output current is fed back to the anode input current (in particular feedback). The recirculation unit can be configured to supply a certain proportion r div of the cathode input current and provide it to the heat exchanger to provide the anode output current A out , especially water vapor contained therein, by the specific proportion r divof the tapped cathode input current, for example by heat transfer, wherein in particular the cathode input current or the tapped specific portion thereof has a lower temperature than the anode output current or the water vapor. Thus, in particular before the absorbed anode output current or water vapor is fed to the anode input current, in particular via the anode path connection point, the temperature can be influenced, in particular reduced. As a result, the saturation vapor temperature can be influenced, in particular reduced. As a result, the humidity of the anode input current can be controlled and / or regulated, preferably influenced, in particular reduced. This can realize the above-mentioned advantages, in particular the performance of the fuel cell system can be increased.

[0093] The heat exchanger, the anode heat exchanger, and / or the cathode path heat exchanger can each have a first inlet connected to a first outlet and a second inlet connected to a second outlet. Preferably, no material or material flow can occur between the first inlet / outlet and the second inlet / outlet. Preferably, only (thermal) energy can be exchanged. Thus, it can be provided that a respective volume flow (or molar flow) does not change when passing through a heat exchanger, anode heat exchanger, and / or cathode path heat exchanger.

[0094] The anode path connection point can be located between the hydrogen mass flow controller and the recirculation blower. This can be advantageous to allow for influence by the recirculation blower and / or the anode heat exchanger, particularly after mixing and / or before reaching the anode inlet. Thus, the flow velocity can be varied by the recirculation blower. Heat can also be removed and / or added by the anode heat exchanger.

[0095] This results in the same advantages with regard to a fuel cell system according to the invention as have already been described with regard to a method according to the invention according to the first aspect.

[0096] It is also conceivable that the recirculation unit has a temperature sensor for detecting an actual temperature t ist , in particular an actual saturation steam temperature t sat, ist, of the water vapor, which is used to regulate and / or control the humidity x H2O, Ain the anode input current Ain , the fuel utilization FU Sys of the fuel cell system and / or fuel utilization FU Stk the fuel cell unit can be used by the control unit, in particular is used, wherein the temperature sensor is arranged on the heat exchanger, in particular at an outlet of the heat exchanger.

[0097] It can be provided that depending on the humidity x H2O, Ain a regulation and / or control of fuel utilization FU Sys of the fuel cell system and / or fuel utilization FU Stk of the fuel cell unit by the control unit, in particular based on one of the preceding equations.

[0098] The temperature sensor can be arranged shortly after, in and / or shortly after the heat exchanger. The arrangement can be arranged shortly after the heat exchanger, in particular shortly after the first feeder. This can be advantageous in order to enable precise measurement and / or to prevent the temperature sensor from being exposed to excessive temperatures (in particular due to a temperature gradient from the first receptacle to the first feeder of the heat exchanger). A temperature sensor with lower temperature resistance can be selected and / or wear can be reduced. The actual temperature t ist , in particular an actual saturation steam temperature t sat, ist , of the water vapor are transmitted to the control unit in order to be preferably taken into account during control and / or regulation, in particular during calculation.

[0099] Alternatively or additionally, the temperature sensor can detect a pressure, an actual pressure, and / or an actual saturation vapor pressure. This can be transmitted to the control unit, particularly analogously to the above explanations, to be preferably taken into account during control and / or regulation, particularly during calculation.

[0100] A high-temperature region can be provided, which in particular includes the fuel cell unit, the cathode path heat exchanger, the anode heat exchanger, the burner, the cathode inlet, the cathode outlet, the anode inlet, and / or the anode outlet. The temperature in the high-temperature region can be (relatively) high; for this purpose, it can be thermally insulated.

[0101] Within the scope of the invention, it is optionally possible for the heat exchanger to have at least one, preferably all, of the following features: - a condensate separator for at least partially condensing the water vapor around the anode output stream A out to cool, - an anode path outlet connected to the heat exchanger, in particular the condensate separator, for discharging a volume flow of condensed water vapor V̇ Cond , - a first receptacle for receiving the anode output current A out contained water vapor, - a first feeder for feeding the absorbed water vapor to the anode input stream Ain , - a second recording for tapping the specific portion r div the cathode input current K in , wherein in particular the second receptacle is connected to a cathode path valve, - a second feeder for at least partially returning the determined portion r div the cathode input current K in into the cathode path, especially into the cathode input current Kin via a cathode path connection point.

[0102] The condensate separator can be arranged in the heat exchanger. The condensate separator can cool the anode output stream, in particular by heat exchange or cooling in the heat exchanger. The water vapor at least partially contained in the anode output stream can be at least partially condensed in the condensate separator by condensation. In the heat exchanger, in particular in the condensate separator, moisture, humidity and / or water vapor can be removed from the anode output stream, in particular by condensation. This can increase the moisture content, the fuel utilization FU Sys of the fuel cell system and / or the fuel utilization FU Stk of the fuel cell unit. It can also be provided, depending on the humidity, the fuel utilization FU Sys of the fuel cell system and / or the fuel utilization FUStk of the fuel cell unit. The fuel utilization FU Sys of the fuel cell system and / or the fuel utilization FU Stk of the fuel cell unit as a setpoint. The control unit can then adjust the (required) humidity, the saturation vapor temperature, the saturation vapor pressure, the recirculating volume flow, the recirculation rate, the volume flow of hydrogen, the fuel utilization FU Sys of the fuel cell system and / or the fuel utilization FU Stk of the fuel cell unit (see equations above). In particular, the fuel efficiency FU Sys of the fuel cell system or the fuel utilization FU Stk of the fuel cell unit are specified as a setpoint and the other variable (as well as one or more of the others) are calculated. If several setpoints are specified, for example, the humidity, the fuel utilization FUSys of the fuel cell system and / or the fuel utilization FU Stk of the fuel cell unit, the control unit can be configured to set as many setpoints as possible and / or at least to set an optimum for all setpoints.

[0103] The resulting condensate can then be removed from the fuel cell system, for example via an anode path drain, which is preferably connected to the heat exchanger, in particular to the condensate separator. Accordingly, the anode path drain can be configured to drain a volume flow of condensed water vapor V̇ Cond . The volume flow of condensed water vapor V̇ Condcan be detected by a volume flow sensor for condensed water vapor. The volume flow sensor can be arranged in or downstream of the heat exchanger, in particular in a connecting section between the heat exchanger and the anode path outlet. Alternatively or additionally, the volume flow sensor for condensed water vapor can be arranged at or in the anode path outlet. The result of the detection can be transmitted to a control unit, preferably for use in controlling and / or regulating, in particular in calculating.

[0104] The heat exchanger may comprise a first receptacle for receiving in the anode output stream A out contained water vapor.

[0105] The heat exchanger may comprise a first feeder for feeding the absorbed water vapor to the anode input stream A in , The first receptacle can be connected to the first feeder, in particular directly.

[0106] The heat exchanger may have a second receptacle for tapping the specific portion r div the cathode input current K in wherein in particular the second receptacle is connected to a cathode path valve.

[0107] The heat exchanger may comprise a second feeder for at least partially returning the determined portion r div the cathode input current K in into the cathode path, especially into the cathode input current K in via a cathode path connection point. The second receptacle can be connected to the second feeder, in particular directly. Thus, the cathode input current K inat least partially through the heat exchanger. Provision can be made for the remaining portion of the cathode inlet stream to flow (without detour) through the cathode path valve, in particular toward the cathode inlet. Preferably, heat exchange or heat transfer takes place (only) between the first receptacle / feeder and the second receptacle / feeder in the heat exchanger. Preferably, no medium, in particular gas and / or liquid, is exchanged. Thus, the saturation vapor temperature and / or humidity can be influenced (solely) by cooling.

[0108] The cathode path connection point can be designed as a T-piece, Y-splitter and / or component (e.g. pipe) with three openings, in particular two inlets (e.g. connected to the outlet of the cathode path valve and the, in particular, second feeder of the heat exchanger) and one outlet (e.g. in the direction of the cathode inlet). In the cathode path connection point or the cathode path connection point, the cathode inlet stream preferably recombines, which in particular was tapped at least partially by the cathode path valve, while the remaining portion flows directly from the cathode path valve to the cathode path connection point. In this case, the volume flow of the cathode inlet stream upstream of the cathode path valve can preferably correspond to the volume flow downstream of the cathode path connection point, in particular since only heat is exchanged in the heat exchanger and preferably no medium (“mole-preserving” or “mass-preserving”).

[0109] The cathode path valve can be arranged between the air supply unit and the cathode path connection point, in particular connected to them. The cathode path valve can comprise a three-way valve. In particular, by adjusting the valve, a specific proportion r div the cathode input current K in tapped, while the remaining portion preferably flows directly to the cathode path connection point. Thus, in particular in a first end position, the entire flow can be directed directly to the cathode path connection point by setting. In particular in a second end position, the entire flow can be directed via the heat exchanger to the cathode path connection point by setting. In an intermediate position of the cathode path valve, a specific portion (e.g. percentage) r divfed to the heat exchanger, preferably to enable cooling. The cathode input stream preferably has a lower temperature than the anode output stream. This allows the cathode input stream to cool the anode output stream (reduce its temperature), particularly by transferring heat. For example, the temperature of the anode output stream can be cooled by the heat exchanger from approximately 250°C to 40°C.

[0110] Furthermore, within the scope of the invention, it can be provided that the fuel cell system has at least one of the following features: - a control unit, in particular as a logic circuit, wherein the control unit is configured to carry out and / or control / regulate a method according to the first aspect, in particular at least partially, - an inverter, in particular a DC / AC converter.

[0111] The control unit can carry out the method at least partially and / or control and / or regulate the fuel cell system in order to carry out the method at least partially.

[0112] The control unit can be included in the fuel cell system, in particular in the recirculation unit, and / or connected to it, for example via a data connection.

[0113] The control unit can be connected to the hydrogen valve, the hydrogen mass flow controller, the recirculation blower, the recirculation unit, the temperature sensor, the air supply unit, the cathode path valve, the air blower, the burner, and / or the air outlet, preferably via a data connection, for controlling and / or regulating the hydrogen valve. The aforementioned components can each have an actuator that can be controlled by the control unit, for example, for adjusting a valve, controlling a sensor, and / or transmitting data (e.g., acquired sensor data). Furthermore, the aforementioned components can each have a sensor that is designed to detect temperature, pressure, volume flow, and / or other relevant parameters.The recorded results can be sent to the control unit, in particular via a data connection, in order to preferably be taken into account in a control and / or regulation, in particular calculation.

[0114] With regard to the present invention, it is conceivable that the anode path has at least one of the following features: - a hydrogen tank comprising hydrogen, ammonia and / or a chemical compound comprising hydrogen, - a hydrogen valve, in particular for opening and / or closing, - a hydrogen mass flow controller, in particular for regulating and / or controlling a volume flow of hydrogen V̇ H2in in the anode input current Ain , - a recirculation fan, in particular for controlling and / or regulating a recirculating volume flow V̇ recy , - an anode heat exchanger, in which in particular the anode input current Ain by the anode output current A out is heated and / or the anode output current A out by the anode input current A in is cooled, wherein preferably the anode input current A in is taken in via a first inlet of the anode heat exchanger and is fed to the anode inlet via a first outlet of the anode heat exchanger, wherein preferably the anode output stream is taken in via a second inlet of the anode heat exchanger and is fed to the heat exchanger via a second outlet of the anode heat exchanger, - an anode path drain connected to the heat exchanger to provide a volume flow of condensed water vapor V̇ Cond from the anode path.

[0115] The hydrogen tank can comprise a container and / or a supply line. This allows hydrogen, ammonia, and / or a chemical compound comprising hydrogen to be provided. This can then be introduced into the anode path through the hydrogen tank.

[0116] The hydrogen valve can be used for connecting and / or disconnecting, especially between the hydrogen tank and the hydrogen mass flow controller. This allows you to adjust whether a medium (such as those mentioned above) can even enter the anode path.

[0117] The hydrogen mass flow controller can be used to set a volume flow of hydrogen V̇ H2in(particularly at the inlet and / or front part of the anode path), in particular controlled by a control unit, for example by the control unit adjusting a valve of the hydrogen mass flow controller. The volume flow of hydrogen V̇ H2in have a mass and / or volume, especially per unit of time. In other words, the amount of hydrogen per unit of time can be adjusted.

[0118] The recirculation fan can adjust the flow rate of the anode input stream. A recirculation sensor can be arranged before, on, in and / or after the recirculation fan, which can be configured in particular to measure a recirculating volume flow V̇ recy to measure, wherein in particular the measured value can be transmitted to the control unit in order to be taken into account preferably during control and / or regulation, in particular during calculation.

[0119] The recirculating volume flow V̇ recy can be the sum of the volume flow of hydrogen V̇ H2in and the anode output current A out (in particular minus the volume flow of condensed water vapor V̇ Cond and / or a volume flow fed into the burner). The anode input current A in can (especially at the anode inlet and / or exclusively) reduce the recirculating volume flow V̇ recy In particular, the anode input flow initially at the hydrogen mass flow controller may (only) be the volume flow of hydrogen V̇ H2in The anode input flow can (subsequently) increase the volume flow of hydrogen V̇ due to the addition of what is supplied from the heat exchanger. H2in and (at least partially) the anode output current A out wherein in particular the anode output current A outby a volume flow of condensed water vapor V̇ Cond may be reduced (outflow from the anode path). Thus, the anode input flow may change during transport from the hydrogen tank to the anode inlet, particularly with regard to humidity (preferably reduced by recirculation or adjusted / increased for the injected hydrogen), volume flow (especially increased), temperature (especially increased), and / or pressure.

[0120] In this case, the anode heat exchanger can preferably (only) provide an exchange of heat, in particular from the anode output stream to the anode input stream or the recirculating volume flow, the temperature of which preferably increases in order to advantageously already have a higher temperature at the anode inlet, wherein the temperature of the anode output stream is advantageously reduced before it is fed to the heat exchanger.

[0121] Furthermore, it is conceivable that the cathode path has at least one of the following features: - an air supply unit for introducing the cathode input current K in into the cathode path, - a cathode path connection point, via which a return of air tapped by the cathode path valve into the cathode path is at least partially made possible, - an air blower, in particular for controlling and / or regulating a flow rate, a volume flow and / or a mass flow of the cathode input current K in , - a cathode path heat exchanger, in which in particular the cathode input current K in by the cathode output current K out is heated and / or the cathode output current K out by the cathode input current K in is cooled, wherein preferably the cathode input current K inis taken up via a first inlet of the cathode heat exchanger and is fed to the cathode inlet via a first outlet of the cathode heat exchanger, - a burner which is connected to the cathode output and / or the anode output, in particular to control the cathode output current K out and / or the anode output current A out to burn at least partially, - an air outlet connected to the cathode outlet, in particular the burner, in order to at least partially remove air from the fuel cell system.

[0122] An air supply unit for introducing the cathode input current K ininto the cathode path. The air supply unit can comprise an oxygen tank, an air tank, a filter, in particular an oxygen filter or air filter, and / or an intake device, for example for intake of air. Accordingly, the cathode input stream, which is preferably introduced into the cathode path, can comprise oxygen and / or air.

[0123] The cathode path connection point can be configured to allow a previously tapped portion of the cathode input current and / or the air to flow back into the cathode input current by recirculating it. Accordingly, a portion of the cathode input current can preferably be tapped to cool the anode output current. The extent of cooling can be adjusted by controlling and / or regulating the tapped portion. The cathode path connection point is preferably arranged between the cathode path valve and the air blower. Alternatively, the air blower can be arranged upstream of the cathode path valve. Preferably, the volume flow downstream of the cathode path connection point corresponds to the volume flow at or downstream of the air supply unit.

[0124] In this case, an air blower, in particular for controlling and / or regulating a flow rate, a volume flow and / or a mass flow of the (in particular recombined) cathode input flow (K in ), which is preferably arranged between the cathode connection point and the cathode path heat exchanger.

[0125] In this case, the cathode path heat exchanger can preferably (only) provide an exchange or transfer of heat, in particular from the cathode output stream to the cathode input stream, the temperature of which preferably increases in order to advantageously already have a higher temperature at the cathode inlet, wherein the temperature of the cathode output stream is advantageously reduced before it is fed to the cathode path heat exchanger.

[0126] The burner can preferably be arranged between the cathode outlet and the cathode path heat exchanger. It can be provided that the anode output stream is at least partially fed to the burner. The cathode output stream and / or the anode output stream can be combusted, in particular partially, by the burner. This makes it possible to influence and / or adjust the recirculation rate. In particular, air, oxygen, ammonia and / or (flammable) chemical compounds, in particular comprising hydrogen, can be combusted. The burner can preferably be controlled and / or regulated by the control unit. In particular, this enables adjustment of the temperature, the proportion of the anode output stream, and / or the supply of additional substances.

[0127] The air outlet can guide the cathode output stream, in particular air, out of the cathode path or allow it to escape. The air outlet can be connected to the cathode path heat exchanger, in particular to its outlet. If a burner is provided, its combustion products can be expelled via the air outlet. The anode output stream can also be expelled, at least partially, via the air outlet after being fed to the burner, in particular after combustion.

[0128] The above object is further achieved according to a third aspect by a computer program product according to the invention, comprising instructions which, when the computer program product is executed by a computer, cause the computer to implement the method according to the first aspect.

[0129] This results in the same advantages with regard to a computer program product according to the invention as have already been described with regard to a method according to the invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect.

[0130] The above object is further achieved according to a fourth aspect by a computer-readable data carrier according to the invention, in which instructions are stored which, when executed by a computer, cause the computer to carry out the method according to the first aspect.

[0131] This results in the same advantages with regard to a computer-readable data carrier according to the invention as have already been described with regard to a method according to the invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect and / or a computer program product according to the invention according to the third aspect.

[0132] The above object is further achieved according to a fifth aspect by a control unit according to the invention, comprising a computing unit and a memory unit in which instructions are stored which, when at least partially executed by the computing unit, carry out a method according to the first aspect, wherein in particular the control unit has a PID controller and / or a feedforward control.

[0133] It can be provided that the control unit, in particular the computing unit, carries out and / or initiates the method steps, for example by controlling the fuel cell system and / or its (above-mentioned) components. The control unit can send control signals to corresponding actuators of the fuel cell system in order to adjust them. The control unit can also receive sensor signals from sensors of the fuel cell system, for example the temperature sensor, which are taken into account in particular during control and / or regulation. Based on these signals, for example, target values ​​can be calculated, in particular a target saturation vapor temperature.

[0134] It may be provided that a pilot control enables start-up and / or basic operation of the fuel cell system. The pilot control may specify starting values, for example, for the adjustment of the cathode path valve. Thus, for example, the cathode path valve can be adjusted, particularly independently of the PID controller. For example, it could initially be closed. Afterward, it may be provided to open it (continuously).

[0135] It can be provided that the PID controller, particularly after starting and / or running up the fuel cell system, performs control and / or regulation of the fuel cell system in addition to and / or as an alternative to the pre-control. This can include control and / or regulation of the cathode path valve. This allows for (particularly fine) optimization of the operation of the fuel cell system.

[0136] This results in the same advantages with regard to a control unit according to the invention as have already been described with regard to a method according to the invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect and / or a computer program product according to the invention according to the third aspect and / or a computer-readable data carrier according to the invention according to the fourth aspect.

[0137] The above object is further achieved according to a sixth aspect by a system according to the invention comprising a fuel cell system according to the second aspect and / or a control unit according to the fifth aspect.

[0138] A system may comprise a (residential) building, an industrial building, a power plant, a storage facility, a vehicle, a ship, an aircraft, or another system with, in particular, increased energy requirements. It may be particularly preferred to provide a (substantially) stationary (immobile) application of the fuel cell system.

[0139] This results in the same advantages with regard to a system according to the invention as have already been described with regard to a method according to the invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect and / or a computer program product according to the invention according to the third aspect and / or a computer-readable data carrier according to the invention according to the fourth aspect and / or a control unit according to the invention according to the fifth aspect.

[0140] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. In each case, schematically Fig. 1 an anode path, Fig. 2 an anode path and a cathode path of a fuel cell system, Fig. 3 a fuel cell system, Fig. 4 a fuel cell system, Fig. 5 a fuel cell system comprising a control unit, Fig. 6 a system 200, and Fig. 7 a procedure.

[0141] In the following figures, identical reference numerals are used for the same technical features, even for different embodiments.

[0142] Fig. 1 shows an example of an anode path 10, as may be provided in particular in a fuel cell system 100. The anode path 10 may be configured to supply a fuel gas, e.g., hydrogen, to the anode inlet 16 of a fuel cell unit 101. The latter may be fed in via a hydrogen tank 11, in particular alternatively or additionally via a hydrogen network. A hydrogen valve 12 may prevent or permit the inflow, in particular depending on an actuator, which may be adjustable, for example, via a control unit FCCU. A hydrogen mass flow controller 13 may control the volume flow of hydrogen V̇ H2inFurthermore, a recirculation fan 14 can be used to adjust the flow velocity at this point on the anode path 10. For this purpose, the recirculation fan 14 can be controlled by a control unit FCCU. The volume flow can then be passed through an anode heat exchanger 15, which in particular enables heating. The anode path 10 can then be connected to the anode inlet 16. In this case, the volume flow can be introduced into the anode inlet 16. Within the fuel cell unit 101, the volume flow is passed from the anode inlet 16 to an anode outlet 17. A connection to the anode heat exchanger 15 can be provided from the anode outlet 17, wherein the volume flow is passed, for example, via a recirculation path 18.1 through the anode heat exchanger 15, to a heat exchanger 18.2. A recirculation unit 18 can have a recirculation path 18.1, in particular as an "input," a heat exchanger 18.2, and an anode path connection point 18.4. An output of the heat exchanger 15 can thus be connected to an inlet of the heat exchanger 18.2. The volume flow can be fed back to the anode path 10 at the anode path connection point 18.4 via the heat exchanger 18.2.

[0143] Fig. 2 shows in reference to Fig. 1 shows, by way of example, a fuel cell system 100 with an anode path 10 and a cathode path 20. The cathode path 20 can have an air unit 21 (as a "starting point"), via which air can be introduced into the cathode path 20. It can be provided that the air unit 21 introduces ambient air into the cathode path. The corresponding volume flow can then be passed through a cathode path valve 22, where, in particular, a portion of the volume flow can be branched off in order to feed it to the heat exchanger 18.2. The tapped portion can be returned at a cathode path connection point 23. An air blower 24 can then accelerate the volume flow. This can then be passed through a heat exchanger 25 before being fed into the fuel cell unit 101 via a cathode inlet 26.Inside the fuel cell unit 101, the volume flow can be transported from the cathode inlet 26 to a cathode outlet 27. A corresponding reaction can occur inside the fuel cell unit 101 to advantageously generate energy, in particular current and / or voltage.

[0144] Fig. 3 shows in reference to Fig. 1 or Fig. 2 a fuel cell system 100, with an anode path 10 (in particular as in Fig. 1) and a cathode path 20 (in particular as shown in Fig. 2). At the cathode path valve 22, a certain proportion r div the cathode input current K in The cathode input current K in can extend from the air supply unit 21 to the cathode inlet 26, and in particular can change along the way (e.g., by tapping and / or changing the temperature). A cathode output current K outleaves the fuel cell unit 101 via a cathode outlet 27. In this case, the cathode output current K out a burner 28. The anode output current A out can be fed, in particular partially, to the burner 28. In this case, a recirculation rate r can be provided which determines the proportion of the anode output flow, in particular a volume flow V̇ An,out at the anode outlet 17, which is fed to the recirculation unit 18.

[0145] Combustion can take place in the burner 28. This can be used for material conversion and / or to increase the temperature. An output of the burner 28 can be connected to the cathode path heat exchanger 25. This allows, in particular, the cathode input current K in be tempered, in particular heated, preferably (at least partially) by the cathode output current K out .

[0146] The reaction in the fuel cell unit 101 can generate a current I and / or a voltage. An inverter 40 can be used to generate an alternating current from direct current, in particular the current I. The resulting (waste) heat can also be utilized. The fuel cell unit 101 can comprise a stack of fuel cells.

[0147] The specific proportion r div the cathode input current K in can be fed to the heat exchanger 18.2 to enable cooling 131 of the anode output stream, in particular the water vapor contained therein. This allows the humidity x H2O, Ain the anode input current Ain changed, in particular reduced. For this purpose, a recording 121 of an actual temperature t ist , in particular an actual saturation steam temperature t sat, istbe provided, which can preferably be carried out by a temperature sensor 18.3, in particular included in the recirculation unit 18. The actual saturation steam temperature t sat, ist can be determined depending on a saturation steam temperature t sat be determined, in particular they essentially correspond to this. The saturation steam temperature t sat, and in particular a saturation vapor pressure p sat , prevail in a section between heat exchanger 18.2 and anode path connection point 18.4. Preferably, the temperature sensor 18.3 can be arranged in this area to detect the actual temperature t ist , in particular an actual saturation steam temperature t sat, ist , to enable. The anode input current A in can, especially initially (only), increase the volume flow of hydrogen V̇ H2inAn additional volume flow can be supplied at the anode path connection point 18.4. The anode output current A out (at least partially). Accordingly, a recirculating volume flow V̇ recy the volume flow of hydrogen V̇ H2in and the (returned) anode output current A out The recirculating volume flow V̇ recy can be introduced again into the anode input 16. It could also be formulated so that the anode input current A in then the recirculating volume flow V̇ recy or is converted to it, especially after the recirculating volume flow V̇ recy has passed the anode heat exchanger 15 (e.g. to increase the temperature).

[0148] Fig. 4 shows an example, particularly based on the Fig. 1 to 3, a fuel cell system 100. In this case, a volume flow V̇ Cond of condensed water vapor, which is produced in particular during the cooling of water vapor in the heat exchanger 18.2, can be removed, and in particular leave the fuel cell system 100. An air outlet 29 can also be provided, which is connected in particular to the cathode path heat exchanger 25. Via this, (excess) air from the cathode path or the cathode output stream K outA high-temperature region 102 can be provided, which in particular comprises the fuel cell unit 101, the cathode path heat exchanger 25, the anode heat exchanger 15, the burner 28, the cathode inlet 26, the cathode outlet 27, the anode inlet 16 and / or the anode outlet 17. In the high-temperature region 102, the temperature can be (relatively) high; for this purpose, it can in particular be thermally insulated. The fuel cell unit 101 can have a fuel utilization FU Stk This can in particular comprise a quantification of the proportion of fuel used, in particular with respect to the fuel cell unit 101. The fuel cell system 100 can have a fuel utilization FU Sys This may, in particular, include a quantification of the proportion of (efficiently) used fuel, in particular with respect to the fuel cell system 100.

[0149] Fig. 5 shows an example, particularly based on the Fig. 1 to 4, a fuel cell system 100. This is also connected to a control unit FCCU, in particular via a data connection. The control unit FCCU can be connected to the temperature sensor 18.3, and can use the latter, in particular, to detect an actual temperature t ist , for example an actual saturation steam temperature t sat, ist , which can be transmitted to the FCCU control unit. The FCCU control unit can then set a target humidity x H2O, Ain, soll the anode input current Ain , a (target) fuel utilization FU Sys of the fuel cell system, a (target) fuel utilization FU Stk of the fuel cell unit, and / or a (target) current I, can be specified or have specified. Depending on this, in particular on the target humidity x H2O, Ain, soll , the control unit FCCU can set a target temperature t soll, in particular a target saturation steam temperature t sat, soll , calculate. The control unit FCCU can control a PID controller FCCU PID and / or a feedforward control FCCU VS The target temperature t soll , in particular a target saturation steam temperature t sat, soll , from the PID controller FCCU PID and / or the feedforward control FCCU VS The PID controller FCCU PID the actual temperature t ist , in particular the actual saturation steam temperature t sat, ist , by transmitting 122. The PID controller FCCU PID and / or the feedforward control FCCU VS can set a control value r div,SW for the cathode path valve 22. This can be transmitted, in particular via a data connection, to the cathode path valve 22, in particular to an actuator, in order to adjust the cathode path valve 22, in particular by a certain proportion r divthe cathode input current K in Depending on the specific proportion r div the cathode input current K in a cooling 131, in particular a cooling power, of (or for) the water vapor or the anode output current can be adjusted. Accordingly, depending on the specific proportion r div the cathode input current K in , in particular from the cooling 131, a saturation vapor temperature t sat and / or actual saturation steam temperature t sat, ist Depending on the saturation steam temperature t sat and / or actual saturation steam temperature t sat, ist , the proportion of condensed water vapor and / or the volume flow V̇ Cond of condensed water vapor. Accordingly, more (condensed) water vapor can be removed, especially via the anode path outlet 19. The more water vapor is condensed, the lower the humidity x can be. H2O, Ainthe anode input current A in Therefore, the humidity x H2O, Ain the anode input current A in depending on the saturation steam temperature t sat and / or actual saturation steam temperature t sat, ist be set, in particular by setting a control value r div,SW for the cathode path valve 22 a certain proportion r div the cathode input current K in is tapped.

[0150] Fig. 6 shows, by way of example, a system 200, in particular a vehicle 200, comprising a fuel cell system 100 and a control unit FCCU. The control unit FCCU can have a computing unit CU and a memory unit MU. The fuel cell system 100 and the control unit FCCU can be connected for data communication via a data connection.

[0151] Fig.7 shows an example of a method for operating a fuel cell system 100, in particular a solid oxide fuel cell system, comprising: - Controlling the fuel cell system 100 to receive 110 of the anode output current A out contained water vapor through a heat exchanger 18.2 of the recirculation unit 18, wherein the heat exchanger 18.2 is connected to the anode outlet A out is connected, - Controlling the recirculation unit to tap 120 a specific portion r div the cathode input current K in through the recirculation unit 18, - Providing 130 the tapped cathode input current K in to the heat exchanger 18.2 in order to cool 131 the absorbed water vapor by the tapped cathode input current K in to obtain, and - Feeding 140 of the absorbed water vapor to the anode input current A in through the heat exchanger 18.2.

[0152] It can be provided that the control of the recirculation unit for tapping 120 of a certain proportion r div the cathode input current K in by the recirculation unit 18 has at least one of the following features: - Controlling, by a control unit (FCCU), a temperature sensor (18.3) for detecting (121) an actual temperature (t ist ), in particular an actual saturation steam temperature (t sat, ist ), the water vapor through the temperature sensor (18.3), - Transmit 122 the recorded actual temperature t ist , in particular an actual saturation steam temperature t sat, ist , from the temperature sensor 18.3 to the control unit FCCU, - Providing 123, by the control unit FCCU, a target humidity x H2O, Ain, soll the anode input current Ain , which preferably optimizes the performance of the fuel system 100, a target fuel utilization FU Sys,sollof the fuel cell system 100, and / or a target fuel utilization FU Stk,soll the fuel cell unit 101, - Calculating 124, by the control unit FCCU, a target temperature t soll , in particular an actual saturation steam temperature t sat, soll , depending on the target humidity x H2O, Ain, soll , the target fuel utilization FU Sys,soll of the fuel cell system 100, and / or the target fuel utilization FU Stk,soll the fuel cell unit 101, - Providing 125, by the control unit FCCU, the target temperature t soll , in particular the actual saturation steam temperature t sat, soll , and the recorded actual temperature t ist , - Calculating 126, by the control unit FCCU, a control value r div,SW for a cathode path valve 22 of the fuel cell system 100, in particular depending on a target temperature t soll , in particular an actual saturation steam temperature tsat, soll , and a recorded actual temperature t ist , - Adjustment 127, by the control unit FCCU, of the cathode path valve 22 depending on the control value r div,SW to a certain proportion r div the cathode input current K in preferably the humidity of the anode input current x H2O, Ain , depending on the specific proportion r div the cathode input current K in is set, - Recording 128 of the specific portion r div the cathode input current K in through the heat exchanger 18.2, in particular to achieve a saturation steam temperature t sat and / or a saturation vapor pressure p sat between the heat exchanger 18.2 and the anode path connection point 18.4, preferably the saturation steam temperature t sat depending on the humidity of the anode input current x H2O, Ain , the fuel utilization FU Sysof the fuel cell system 100, and / or the fuel utilization FU Stk the fuel cell unit 101 is set, - at least partial return 129 of the determined share r div the cathode input current K in from the heat exchanger 18.2 into the cathode path 20, in particular from a second feeder of the heat exchanger 18.2 into the cathode input stream K in via a cathode path connection point 23.

[0153] Furthermore, it can be provided that the cooling 131 has at least one of the following features: - at least partial condensation 132 of the water vapor by the heat exchanger 18.2, in particular by a condensate separator, - Discharge 133 of a volume flow of condensed water vapor V̇ Condvia an anode path outlet 19 connected to the heat exchanger 18.2, in particular the condensate separator, wherein in particular the volume flow of condensed water vapor V̇ Cond is set by the control unit FCCU, depending on a target humidity x H2O, Ain, soll the anode input current Ain , a target fuel utilization FU Sys,soll of the fuel cell system 100, and / or a target fuel utilization FU Stk,soll the fuel cell unit 101.

[0154] In addition, it can be provided that the supply 140 of the absorbed water vapor to the anode input current A in through the heat exchanger 18.2 has at least one of the following features: - Mixing 141, in particular in an anode path connection point 18.4, a volume flow of hydrogen V̇ H2in with the steam supplied through the heat exchanger 18.2 to create a recirculating volume flow V̇ recyto generate, whereby in particular the recirculating volume flow V̇ recy the anode input current A in corresponds.

[0155] It can also be provided that, in particular repeatedly, a control and / or regulation 150 of the fuel cell system 100 is carried out by the control unit FCCU, in particular via a data connection, comprising at least one of the following features: - controlling and / or regulating a hydrogen valve 12, in particular to provide hydrogen in the anode path 10, - Controlling and / or regulating a hydrogen mass flow controller 13, in particular to control a volume flow of hydrogen V̇ H2in in the anode path 10, wherein in particular the volume flow of hydrogen V̇ H2in is set by the control unit FCCU, depending on a target fuel utilization FU Sys,soll of the fuel cell system 100, , - Controlling and / or regulating a recirculation fan 14, in particular to generate a recirculating volume flow V̇ recy to be adjusted, whereby in particular the recirculating volume flow V̇ recy is set by the control unit FCCU, depending on a target humidity x H2O, Ain, soll the anode input current Ain , a target fuel utilization FU Sys,soll of the fuel cell system 100, and / or a target fuel utilization FU Stk,soll the fuel cell unit 101. List of reference symbols 10 Anode path 11 Hydrogen tank 12 Hydrogen valve 13 hydrogen mass flow controllers V H2in Volume flow of hydrogen 14 recirculation fans V recy recirculating volume flow 15 anode heat exchangers 16 Anode input A in Anode input current 17 Anode output Aout Anode output current V An,out Volume flow at the anode outlet V H2O , An, out Volume flow of water at the anode outlet V loop recirculated volume flow 18 Recirculation unit 18.1 Recirculation path 18.2 Heat exchanger 18.3 Temperature sensor r recirculation rate t sat Saturated steam temperature t ist Actual temperature t sat, ist Actual saturation steam temperature t soll Target temperature t sat, soll Target saturation steam temperature p sat Saturation vapor pressure 18.4 Anode path connection point 19 Anode path drain V Cond Volume flow of condensed water vapor r div certain proportion of the cathode input current r div,SW Control value for cathode path valve xH2O, Ain Humidity of the anode input current x H2O, Ain, soll Target humidity of the anode input current 20 Cathode path 21 Air supply unit 22 Cathode path valve 23 Cathode path connection point 24 air blowers 25 cathode path heat exchangers 26 Cathode input K in Cathode input current 27 Cathode output K out Cathode output current 28 burners 29 Air outlet 40 inverters 100 fuel cell system FU Sys Fuel utilization of the fuel cell system FU Sys,soll Target fuel utilization of the fuel cell system 101 Fuel cell unit FU Stk Fuel utilization of the fuel cell unit FU Stk,soll Target fuel utilization of the fuel cell unit 102 high temperature range I Current 110 Controlling the fuel cell system to absorb water vapor 120 Controlling the recirculation unit to tap a specific portion 121 Controlling a temperature sensor to detect an actual temperature 122 Transmission of the recorded actual temperature 123 Providing a target humidity, target fuel utilization of the fuel cell system, and / or a target fuel utilization 124 Calculating a target temperature 125 Providing the target temperature and the recorded actual temperature 126 Calculating a control value for a cathode path valve 127 Adjusting the cathode path valve 128 Recording the specific portion of the cathode input current 129 Return of the specific share 130 Providing the tapped cathode input current 131 Cooling of the absorbed water vapor 132 Condensation of the absorbed water vapor 133 Discharge of a volume flow of condensed water vapor 140 Supplying the absorbed water vapor to the anode input stream 141 Mixing a volume flow of hydrogen with the water vapor 150 Control and / or regulation of the fuel cell system 200 systems FCCU control unit FCCU PID PID controller FCCU VS Feedforward control CU computing unit MU storage unit QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam" (named as IAPWS-IF97

[0044]

Claims

[1] Method for operating a fuel cell system (100), in particular a solid oxide fuel cell system, the fuel cell system (100) comprising - at least one fuel cell unit (101) for generating energy, comprising - having an anode path (10) - an anode input (16) for receiving an anode input current (A in ) and - an anode output (17) for outputting an anode output current (A out ), and - having a cathode path (20) - a cathode input (26) for receiving a cathode input current (K in ) and - a cathode output (27) for outputting a cathode output current (K out ), - a recirculation unit (18) for regulating and / or controlling a humidity (x H2O, Ain ) of the anode input current (A in ), and / or fuel utilization (FU Stk ) of the fuel cell unit (101), - comprising the method - controlling the fuel cell system (100) to receive (110) in the anode output current (A out ) contained water vapor through a heat exchanger (18.2) of the recirculation unit (18), wherein the heat exchanger (18.2) is connected to the anode outlet (A out ) is connected, - controlling the recirculation unit (18) to tap (120) a specific portion (r div ) of the cathode input current (K in ) by the recirculation unit (18) for regulating and / or controlling the humidity (x H2O , Ain ) of the anode input current (A in ), and / or fuel efficiency (FU Stk ) of the fuel cell unit (101), - controlling (150) the fuel cell system (100), in particular a hydrogen mass flow controller (13) of the anode path (10), in order to control a volume flow of hydrogen (V̇ H2in) in the anode path (10) for controlling and / or regulating a fuel utilization (FU sys ) of the fuel cell system (100). [2] Method according to claim 1, characterized by that the control of the recirculation unit (18) for tapping (120) a certain portion (r div ) of the cathode input current (K in ) by the recirculation unit (18) has at least one of the following features: - Controlling, by a control unit (FCCU), a temperature sensor (18.3) for detecting (121) an actual temperature (t ist ), in particular an actual saturation steam temperature (t sat, ist ), the water vapor through the temperature sensor (18.3), - Transmitting (122) the recorded actual temperature (t ist ), in particular an actual saturation steam temperature (t sat, ist ), from the temperature sensor (18.3) to the control unit (FCCU), - Providing (123), by the control unit (FCCU), a target humidity (x H2O , Ain, soll ) of the anode input current (A in ), which preferably optimizes the performance of the fuel system (100), a target fuel utilization (FU Sys,soll ) of the fuel cell system (100), and / or a target fuel utilization (FU Stk,soll ) of the fuel cell unit (101), - Calculating (124), by the control unit (FCCU), a target temperature (t soll ), in particular a target saturation steam temperature (t sat, soll ), depending on the target humidity (x H2O , Ain, soll ), the target fuel utilization (FU Sys,soll ) of the fuel cell system (100), and / or the target fuel utilization (FU Stk,soll ) of the fuel cell unit (101), - Providing (125), by the control unit (FCCU), the target temperature (t soll ), in particular the actual saturation steam temperature (t sat, soll), and the recorded actual temperature (t ist ), - Calculating (126), by the control unit (FCCU), a control value (r div,SW ) for a cathode path valve (22) of the fuel cell system (100), in particular depending on a target temperature (t soll ), in particular an actual saturation steam temperature (t sat, soll ), and a recorded actual temperature (t ist ), - Adjustment (127), by the control unit (FCCU), of the cathode path valve (22) depending on the control value (r div,SW ) to a certain proportion (r div ) of the cathode input current (K in ), preferably the humidity of the anode input current (x H2O , Ain ), depending on the specific proportion (r div ) of the cathode input current (K in ) is set, - Recording (128) the specific portion (r div ) of the cathode input current (K in) through the heat exchanger (18.2), in particular to achieve a saturation steam temperature (t sat ) and / or a saturation vapor pressure (p sat ) between the heat exchanger (18.2) and the anode path connection point (18.4), wherein preferably the humidity of the anode input stream (x H2O, Ain ), the fuel utilization (FU sys ) of the fuel cell system (100), and / or the fuel utilization (FU Stk ) of the fuel cell unit (101), depending on the saturation vapor temperature (t sat ) is set, - at least partial return (129) of the determined share (r div ) of the cathode input current (K in ) from the heat exchanger (18.2) into the cathode path (20), in particular from a second feeder of the heat exchanger (18.2) into the cathode input stream (K in ) via a cathode path connection point (23). [3] Method according to one of the preceding claims, characterized by , that, in particular following the activation of the recirculation unit (18) for tapping (120), takes place: - Providing (130) the tapped cathode input current (K in ) to the heat exchanger (18.2) in order to cool (131) the absorbed water vapor by the tapped cathode input current (K in ) to obtain wherein in particular the cooling (131) has at least one of the following features: - at least partial condensation (132) of the water vapor by the heat exchanger (18.2), in particular by a condensate separator, - Discharge (133) of a volume flow of condensed water vapor (V̇ cond ) via an anode path outlet (19) connected to the heat exchanger (18.2), in particular the condensate separator, wherein in particular the volume flow of condensed water vapor (V̇ cond) is set by the control unit (FCCU), depending on a target humidity (x H2O , Ain, soll ) of the anode input current (A in ), a target fuel utilization (FU Sys,soll ) of the fuel cell system (100), and / or a target fuel utilization (FU Stk,soll ) of the fuel cell unit (101). [4] Method according to one of the preceding claims, characterized by that the procedure has: - feeding (140) the absorbed water vapor to the anode input current (A in ) through the heat exchanger (18.2), wherein in particular the supply (140) of the absorbed water vapor to the anode input stream (A in ) through the heat exchanger (18.2) has at least one of the following features: - mixing (141), in particular in an anode path connection point (18,4), a volume flow of hydrogen (V̇ H2in) with the steam supplied through the heat exchanger (18.2) to create a recirculating volume flow (V̇ recy ), whereby in particular the recirculating volume flow (V̇ recy ) the anode input current (A in ) corresponds. [5] Method according to one of the preceding claims, characterized by that, in particular repeatedly, a control and / or regulation (150) of the fuel cell system (100) is carried out by the control unit (FCCU), in particular via a data connection, comprising at least one of the following features: - controlling and / or regulating a hydrogen valve (12), in particular to provide hydrogen in the anode path (10), - controlling and / or regulating a hydrogen mass flow controller (13), in particular to control a volume flow of hydrogen (V̇ H2in ) in the anode path (10), wherein in particular the volume flow of hydrogen (V̇ H2in) is set by the control unit (FCCU), depending on a target fuel utilization (FU Sys,soll ) of the fuel cell system (100), - controlling and / or regulating a recirculation fan (14), in particular to generate a recirculating volume flow (V̇ recy ), whereby in particular the recirculating volume flow (V̇ recy ) is set by the control unit (FCCU), depending on a target humidity (x H2O , Ain, soll ) of the anode input current (A in ), a target fuel utilization (FU Sys,soll ) of the fuel cell system (100), and / or a target fuel utilization (FU Stk,soll ) of the fuel cell unit (101). [6] Fuel cell system (100), in particular solid oxide fuel cell system, comprising - at least one fuel cell unit (101) for generating energy, comprising - having an anode path (10) - an anode input (16) for receiving an anode input current (A in ) and - an anode output (17) for outputting an anode output current (A out ), and - having a cathode path (20) - a cathode input (26) for receiving a cathode input current (K in ) and - a cathode output (27) for outputting a cathode output current (K out ), - a recirculation unit (18) for regulating and / or controlling fuel utilization (FU sys ) of the fuel cell system (100) and / or a fuel utilization (FU Stk ) of the fuel cell unit (101), - wherein the recirculation unit (18) comprises a heat exchanger (18.2) which is connected to the anode outlet (17) and is designed to out ) contained water vapor (110) and then to the anode input current (A in), in particular at an anode path connection point (18.4), - wherein the recirculation unit (18) is designed to recirculate a certain proportion (r div ) of the cathode input current (K in ) and to provide (130) it to the heat exchanger (18.2) for regulating and / or controlling the humidity (x H2O , Ain ) of the anode input current (A in ) and / or fuel efficiency (FU Stk ) of the fuel cell unit (101). [7] Fuel cell system (100) according to the preceding claim, characterized by that the recirculation unit (18) has a temperature sensor (18.3) for detecting an actual temperature (t ist ), in particular an actual saturation steam temperature (t sat, ist ), of the water vapor, which is used in particular for regulating and / or controlling the humidity (x H2O , Ain ) of the anode input current (A in ), the fuel utilization (FU sys) of the fuel cell system (100) and / or the fuel utilization (FU Stk ) of the fuel cell unit (101) by the control unit (FCCU), wherein the temperature sensor (18.3) is arranged on the heat exchanger (18.2), in particular on an outlet of the heat exchanger (18.2). [8] Fuel cell system (100) according to one of the preceding claims, characterized by that the heat exchanger (18.2) has at least one of the following features: - a condensate separator for at least partially condensing (132) the water vapor around the anode output stream (A out ) to cool, - an anode path outlet (19) connected to the heat exchanger (18.2), in particular the condensate separator, for discharging (133) a volume flow of condensed water vapor (V̇ Cond ), - a first receptacle for receiving (110) in the anode output current (A out ) contained water vapor, - a first feeder for feeding (140) the absorbed water vapor to the anode input stream (A in ), - a second receptacle for tapping (120) the determined portion (r div ) of the cathode input current (K in ), wherein in particular the second receptacle is connected to a cathode path valve (22), - a second feeder for at least partially returning (129) the determined portion (r div ) of the cathode input current (K in ) into the cathode path (20), in particular into the cathode input current (K in ) via a cathode path connection point (23). [9] Fuel cell system (100) according to one of the preceding claims, characterized by that the fuel cell system (100) has at least one of the following features: - a control unit (FCCU), wherein the control unit (FCCU) is configured to carry out a method according to one of the preceding claims, - an inverter (40), in particular a DC / AC converter (40). [10] Fuel cell system (100) according to one of the preceding claims, characterized by that the anode path (10) has at least one of the following features: - a hydrogen tank (11) comprising hydrogen, ammonia and / or a chemical compound comprising hydrogen, - a hydrogen valve (12), - a hydrogen mass flow controller (13), in particular for regulating and / or controlling a volume flow of hydrogen V̇ H2in in the anode input current (A in ), - a recirculation fan (14), in particular for controlling and / or regulating a recirculating volume flow V̇ recy , - an anode heat exchanger (15), in which in particular the anode input current (A in ) by the anode output current (A out ) is heated and / or the anode output current (Aout ) by the anode input current (A in ), wherein preferably the anode input current (A in ) is received via a first inlet of the anode heat exchanger (15) and is supplied to the anode inlet (16) via a first outlet of the anode heat exchanger (15), wherein preferably the anode output stream is received via a second inlet of the anode heat exchanger (15) and is supplied to the heat exchanger (18.2) via a second outlet of the anode heat exchanger (15), - an anode path outlet (19) connected to the heat exchanger (18.2) to provide a volume flow of condensed water vapor (V̇ Cond ) from the anode path (10). [11] Fuel cell system (100) according to one of the preceding claims, characterized by that the cathode path (20) has at least one of the following features: - an air supply unit (21) for introducing the cathode input current (Kin ) into the cathode path (20), - a cathode path connection point (23), via which a return (129) of air tapped by the cathode path valve (22) into the cathode path (20) is at least partially enabled, - an air blower (24), in particular for controlling and / or regulating a flow rate, a volume flow and / or a mass flow of the cathode input current (K in ), - a cathode path heat exchanger (25), in which in particular the cathode input current (K in ) by the cathode output current (K out ) is heated and / or the cathode output current (K out ) by the cathode input current (K in ), wherein preferably the cathode input current (K in ) is received via a first inlet of the cathode heat exchanger (25) and is fed to the cathode inlet (26) via a first outlet of the cathode heat exchanger (25), - a burner (28) which is connected to the cathode output (27) and / or the anode output (17), in particular to control the cathode output current (K out ) and / or the anode output current (A out ) to burn at least partially, - an air outlet (29) connected to the cathode outlet (27), in particular the burner (28), in order to at least partially discharge air from the fuel cell system. [12] A computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to implement the method according to any one of the preceding claims. [13] Computer-readable data carrier in which instructions are stored which, when executed by a computer, cause the computer to carry out the method according to one of the preceding claims. [14] Control unit (FCCU), comprising a computing unit (CU) and a memory unit (MU), in which instructions are stored, which, when at least partially executed by the computing unit (CU), carry out a method according to one of the preceding claims, wherein in particular the control unit (FCCU) comprises a PID controller (FCCU PID ) and / or a feedforward control (FCCU VS ). [15] System (200) comprising a fuel cell system (100) and / or a control unit (FCCU) according to one of the preceding claims.

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