CN116544476A

CN116544476A - Fuel cell system and method for controlling at least one stack temperature of a fuel cell system

Info

Publication number: CN116544476A
Application number: CN202310084104.4A
Authority: CN
Inventors: P·霍斯特曼
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2022-02-01
Filing date: 2023-01-31
Publication date: 2023-08-04
Also published as: DE102022201060A1

Abstract

The invention relates to a fuel cell system (10) having a plurality of fuel cell stacks (12), wherein a fuel Shan Chidui (12) is connected to an air supply (16) and to a cathode exhaust gas guide (30), wherein a first cathode return (64 a) is connected to the cathode exhaust gas guide (30) at least one first fuel cell stack (12 a), which is designed to branch off a portion of the cathode exhaust gas (KA) discharged from the first fuel cell stack (12 a) by the cathode exhaust gas guide (30). It is proposed that a first injector (62 a) is connected in front of the first fuel cell stack (12 a) in the air delivery section (16), to which first injector a first cathode return (64 a) is connected.

Description

Fuel cell system and method for controlling at least one stack temperature of a fuel cell system

Technical Field

The present invention relates to a fuel cell device according to the preamble of the independent claim. The invention further relates to a method for regulating at least one stack temperature of a fuel cell system.

Background

The air supplied to the fuel Shan Chidui typically must be warmed in a fuel cell plant. For this purpose, the anode exhaust gas and the cathode exhaust gas are usually combusted in a afterburner, and fresh air is heated with the exhaust gas of the afterburner by means of a heat exchanger. This type of heat recovery is often not very efficient and thus generally reduces the efficiency of the fuel cell plant.

Disclosure of Invention

The invention describes a fuel cell system having a plurality of fuel cell stacks, wherein fuel Shan Chidui is connected to an air supply and to a cathode exhaust gas guide, wherein a first cathode return is connected to the cathode exhaust gas guide at least one first fuel cell stack, which is configured to branch off a portion of the cathode exhaust gas discharged from the first fuel cell stack by the cathode exhaust gas guide. According to the invention, a first injector is connected in the air supply upstream of the first fuel cell stack, and the first cathode return is connected to the first injector. This has the advantage that warm cathode exhaust gas can be recirculated directly through the injector back via the air supply into the first fuel cell stack. Therefore, the heat of the cathode off-gas can be optimally utilized. Furthermore, no additional compressor and/or fan is required in order to transport the cathode exhaust gas back into the fuel cell stack, due to the use of the ejector and the direct connection through the return. This enables a lower complexity in terms of the structure of the fuel cell device and in terms of the cabling on the fluid, which enables a simple and resource-saving production and makes the fuel cell device more reliable and simpler to repair.

A "fuel cell system" is to be understood in particular as meaning a system which forms in particular a particularly functional component, in particular a structural and/or functional assembly, of a fuel cell system or a complete fuel cell system.

In this context, a "fuel cell system" is to be understood in particular to mean a system for stationary and/or mobile acquisition of, in particular, electrical and/or thermal energy using at least one fuel cell unit.

"fuel Shan Chidui" is to be understood in this connection in particular as a unit having a plurality of fuel cells. The fuel cell is provided in particular for converting at least one chemical reaction energy of at least one, in particular continuously supplied, fuel gas, in particular hydrogen, and at least one oxidizing agent, in particular oxygen, into electrical energy. The fuel cell can be configured in particular as a Solid Oxide Fuel Cell (SOFC). Typically a plurality of fuel cells are electrically coupled in series with each other in a fuel cell stack.

A "plurality of fuel cell stacks" is to be understood in particular as meaning at least two fuel cell stacks.

An "air supply" is understood to mean, in particular, a line for air, which is provided for guiding air during normal operation of the fuel cell system. However, it is also conceivable that the air supply leads further gas, for example, cathode exhaust gas or air from the cathode recirculation circuit, during a start-up or heating operation or during a shut-down or cooling operation. The air delivery section can have, for example, one tube or a plurality of tubes. The air delivery portion is supplied with air from an air source.

The term "cathode exhaust gas guide" is understood to mean, in particular, a line for the cathode exhaust gas from the fuel cell stack. The cathode exhaust gas guide can have, for example, one pipe or a plurality of pipes.

By "fuel Shan Chidui is connected to the air supply or to the cathode exhaust gas guide" it is to be understood, in particular, that fuel Shan Chidui is fluidically connected to the air supply or to the cathode exhaust gas guide, so that air can be introduced into the fuel cell stack by the air supply or the cathode exhaust gas can be discharged from the fuel cell stack by the cathode exhaust gas guide.

The term "cathode return" is understood to mean, in particular, a line for the cathode exhaust gas, which is provided for the indirect or direct reintroduction of the cathode exhaust gas from the cathode exhaust gas line into the fuel cell, in particular by feeding the cathode exhaust gas into the air feed.

An "injector" is understood to mean in particular a component which leads through a first fluid and into which a second fluid is injected or introduced. Typically, the ejector has a transfer line for the first fluid with a cross-sectional constriction, at which the second fluid is introduced into the flow of the first fluid. For this purpose, the injector has an opening or nozzle for the second fluid at the cross-sectional constriction. The flow velocity of the first fluid is increased and the pressure is reduced by the cross-sectional constriction, so that the second fluid is sucked into the flow rate of the first fluid (Venturi principle). In the framework of the invention, the cathode exhaust gas is injected into the air stream by means of an injector.

By "the injector is connected in the air supply upstream of the first fuel cell stack" it is to be understood in particular that the injector is connected to the air supply in such a way that the fluid, in particular air, guided by the air supply is guided as the first fluid through the injector or through a cross-sectional constriction of the injector, and that the injector is arranged in fluid terms upstream of the fuel cell stack in the flow direction, i.e. the fluid flowing through the air supply flows first through the injector and then through the fuel cell stack.

The injectors are preferably connected directly upstream of the fuel cell stack, i.e. upstream, in such a way that no further components are arranged in terms of flow technology between the injectors and the fuel Shan Chidui, except for the fuel supply, and in particular no branches of the fuel supply are arranged.

Advantageous refinements of the method can be achieved by the features recited in the dependent claims.

Advantageously, a cathode return associated with the fuel Shan Chidui is connected to the cathode exhaust gas guide at each of the plurality of fuel cell stacks, said cathode return being connected to an injector connected in the air supply to the front of the respective fuel cell stack. This enables particularly good heat utilization. Advantageously, each fuel cell stack is respectively assigned a respective cathode return and a respective injector.

It is further advantageous if a first air distribution device is connected in the air supply upstream of the first injector, said first air distribution device being configured for supplying air to the first fuel cell stack. An air distribution device, which is preferably associated in each case in the air supply, is connected upstream of each injector, which is associated with the fuel Shan Chidui. This has the advantage that in this way a personalized air supply can be allocated to the first fuel cell stack or to each fuel cell stack in a particularly simple manner. This enables particularly reliable and efficient operation, so that the fuel Shan Chidui can operate close to optimum.

An "air distribution device" is understood here to mean, in particular, a device which is provided to distribute the amount of air supplied to the associated fuel Shan Chidui. The air distribution device can, for example, have a settable nozzle or valve, which sets the amount of air supplied to the fuel Shan Chidui from the air supply line. In particular, the air distribution device can have an adjustable valve or an adjustable throttle, which is arranged at the air supply or air supply line and is provided for setting or adjusting the fluid flow via the air supply or air supply line. It is also conceivable that the collection of fuels Shan Chidui has a common air supply line, which supplies substantially the same air quantity to all fuel cell stacks, and that the first air distribution device represents an additional air supply for the first fuel cell stack, which supplies an additional, individually settable air quantity.

Advantageously, the first fuel cell stack has a first temperature sensor for detecting a first stack temperature, wherein the fuel cell device has a controller which is configured to receive the first stack temperature, and wherein the controller is set for setting a first air distribution for the first fuel cell stack, and wherein the controller is set for adjusting the first stack temperature by means of the first air distribution by the first air distribution device. It is possible to operate the fuel Shan Chidui at the optimum operating temperature at all times. Such fuel cell systems operate particularly reliably and with little maintenance.

Advantageously, the controller is configured to set a first current draw (Stromabnahme) from the first fuel cell stack and/or to operate the at least one air distribution device if present. At least the control unit is configured in particular for actuating a common fuel supply for a plurality of fuel cell stacks. Furthermore, the control unit is designed in particular for actuating a common air supply for a plurality of fuel cell stacks.

In this case, it has proven to be particularly advantageous if the first temperature sensor is arranged at the cathode exhaust gas guide at the first fuel cell stack. This enables a particularly reliable assessment of the first stack temperature. Advantageously, the first temperature sensor is arranged directly at the cathode exhaust gas guide or at the cathode exhaust gas outlet of the first fuel cell stack.

When multiple fuel cell stacks have a common fuel supply, the fuel cell arrangement is further improved. In this way, the structure of the fuel cell device can be simplified. In this context, a "common fuel supply" is to be understood in particular to mean that a plurality of fuel cell stacks are fluidically connected to a fuel source and each fuel cell stack is supplied with substantially the same fuel quantity or substantially the same fuel flow. In this case, a common fuel supply is provided under the framework of the invention for supplying a plurality of fuel cell stacks with a largely identical basic quantity of fuel. It is conceivable that at least one first fuel distribution device is provided for precisely setting the first fuel distribution to the first fuel cell stack. In particular, it is then possible for the common fuel supply to provide all fuel cell stacks with a largely identical basic proportion of the fuel distribution for all fuel cell stacks, while the respective fuel distribution device enables a precise adaptation of the respective fuel distribution of the associated respective fuel Shan Chidui.

The structure of the fuel cell device can also be simplified when a plurality of fuel cell stacks have a common air supply. In this context, a "common air supply" is to be understood in particular to mean that a plurality of fuel cell stacks are fluidically connected to an air source and each fuel cell stack is supplied with a largely identical air quantity or a largely identical air flow. In this case, the common air supply is designed under the framework of the invention to supply a plurality of fuel cell stacks with a largely identical basic quantity of air, while at least one first air distribution device is provided for precisely setting the first air distribution.

Also advantageous is a method for regulating at least one stack temperature of a fuel cell system, in particular of a fuel cell system according to the invention, wherein the fuel cell system has a plurality of fuel cell stacks, wherein at least a first stack temperature of a first fuel cell stack of the plurality of fuel cell stacks is detected. According to the invention, at least the first fuel cell stack has a first air distribution device which is designed to supply air to the first fuel cell stack and by means of which the first stack temperature is regulated by means of the first air distribution.

This has the advantage that the first stack temperature of the first fuel cell stack can be set independently of the stack temperature of the remaining fuel Shan Chidui from the plurality of fuel cell stacks. In this way, all fuel cell stacks can be operated optimally, which enables reliable, durable and efficient operation of the fuel cell system.

"detecting the stack temperature" is understood to mean, in particular, measuring the temperature of the fuel Shan Chidui. Here, the temperature of the fuel Shan Chidui can be measured directly at the fuel cell stack. It is also conceivable to approximate or derive the stack temperature by measuring other temperatures, for example, the exhaust air or exhaust gas of the fuel Shan Chidui can be measured and the stack temperature can be determined from this temperature. It can be envisaged, for example, that in the first approximation the temperature of the exhaust air of the fuel Shan Chidui is measured at the fuel cell stack and set equal to the stack temperature in the first approximation. Alternatively, it is conceivable to measure the temperature of the exhaust fuel or exhaust gas of the fuel Shan Chidui at the fuel cell stack in the approximation and to set it equal to the stack temperature in the first approximation. In an advantageous variant, it is conceivable to measure the temperature at the cathode exhaust gas guide and/or the anode exhaust gas guide and to use it to determine and/or approximate the stack temperature.

By "regulating the stack temperature of the fuel cell device" is understood in particular regulating at least one stack temperature of the fuel Shan Chidui. By "regulating the stack temperature of fuel Shan Chidui" is to be understood in particular that the operating parameters of fuel Shan Chidui are adapted or set in such a way that the stack temperature lies in a desired, predefined range. In particular, it is possible to change the operating parameters by adjusting, in particular by adjusting, the loop in such a way that the measured stack temperature lies in a predetermined temperature range. In this case, the measured stack temperature is preferably a control variable, which is compared with a predefined target value. The settable operating parameter of the fuel Shan Chidui is a control variable which is adapted by means of an adjustment in such a way that a deviation of the actual value of the measured stack temperature from the target value is minimized. Control, in particular feed-forward control, is also possible, wherein, for example, in the case of a current too severe deviation of the measured stack temperature, the necessary adaptation to the operating parameters is determined, for example, from a stored value table provided for this purpose, from an analytical model and/or from a simulation model, depending on the value of the deviation.

What is important for the stack temperature is the thermal or energy balance of the fuel cell stack. Thus supplying fuel Shan Chidui to one side chemical energy in the form of fuel and air. This chemical energy is at least partially converted into electrical energy, which is derived from the fuel cell by means of electric current or collection of electric current, the remaining supplied chemical energy being the heat formed in the reaction, the heat is dissipated by air cooling or cathode gas cooling and/or fuel cooling or anode gas cooling. Here the number of the elements to be processed is, the value of the current drawn by the current determines what amount of fuel is converted in the fuel cell stack. If more fuel is supplied than can be oxidized by current collection, a portion of the fuel is directed out in an untreated manner along with the exhaust gas at the anode side of the fuel Shan Chidui. The amount of fuel that is not converted can be correspondingly used for cooling.

The heat flow dQ/dt of the cathode gas of the air or fuel Shan Chidui corresponds to the product of the mass flow dm/dt of the air or cathode gas, the specific heat capacity of the air or cathode gas, and the temperature difference Δt of the air or cathode gas between the input and output of the fuel cell stack. Thus, conceivable operating parameters of the fuel Shan Chidui suitable for adjusting or controlling the stack temperature are: the mass flow of air or cathode gas, for example, with respect to the rotational speed or power of the compressor, fan and/or ventilation device for the air supply; and/or the temperature of the air supplied to the fuel Shan Chidui, such as the power of the air preheater or the on or off condition of the corresponding heat exchanger. In order to cool the fuel cell stack, the fuel Shan Chidui can be supplied with a particularly high amount of air or an increased air flow.

The heat flow dQ/dt of the fuel or exhaust gas or anode gas exiting the fuel cell stack corresponds to the product of the mass flow dm/dt of the fuel or exhaust gas or anode gas, the specific heat capacity of the fuel or exhaust gas or anode gas, and the temperature difference Δt of the fuel or exhaust gas or anode gas between the input and output of the fuel cell stack. Thus, conceivable operating parameters of the fuel Shan Chidui suitable for regulating or controlling the stack temperature are: the mass flow of fuel or anode gas, for example, with respect to the rotational speed or power of a compressor, a fan and/or a ventilation device for the fuel supply or for the anode recirculation or the anode recirculation circuit; and/or the temperature of the air supplied to the fuel Shan Chidui, such as the power of the air preheater or the on or off condition of the corresponding heat exchanger. In order to cool the fuel cell stack, the fuel Shan Chidui can be supplied with a particularly greater amount of fuel or anode gas or with an increased fuel flow or anode gas flow.

Further conceivable operating parameters of the fuel Shan Chidui which are suitable for regulating or controlling the stack temperature are: the current or current drawn by the fuel Shan Chidui. The current drawn or the electrical power output can then be reduced for cooling the fuel cell stack. In this way, on the one hand, the heat formed in the oxidation reaction is reduced and, on the other hand, less fuel supplied to the fuel Shan Chidui is oxidized, so that the amount of fuel that has not been converted contributes to cooling.

The preferred temperature range to which the stack temperature is adjusted, or for the adjusted target temperature or target temperature range, depends on the constructional details of the fuel Shan Chidui or fuel cell system and is typically between 580 ℃ and 640 ℃, preferably between 600 ℃ and 630 ℃, particularly preferably between 610 ℃ and 620 ℃ for SOFCs. In a cell with electrolyte (Electrolyte Supported Cells (electrolyte support cell) -ESC), the preferred temperature range of the stack temperature is typically between 750 ℃ and 950 ℃, preferably between 800 ℃ and 900 ℃, particularly preferably between 850 ℃ and 875 ℃.

Typically, in a fuel cell system all fuel cell stacks are supplied with a common air supply line. Starting from the following assumption, namely: all fuel cell stacks should have the same target temperature, a coarse adjustment of the stack temperature by setting the air delivery often occurs in the prior art. In this case, the stack temperature of the fuel Shan Chidui which deviates most strongly, preferably most strongly, upwards from the target value is typically considered, and this stack temperature is set to the target temperature or into the target temperature range by air supply. This has the disadvantage that all fuel cell stacks are cooled by means of the same air flow, so that the possibility exists that: fuel Shan Chidui, which has less cooling requirements than the fuel Shan Chidui considered for conditioning, is severely cooled and does not operate in the optimal temperature range. The invention thus provides the advantage that the fuel Shan Chidui can be individually warmed with additional independent control parameters or operating parameters. The first fuel cell stack, which has a higher cooling requirement, for example due to increased aging, can be cooled, for example, by increasing the first air distribution by the first air distribution device, without having to reduce the total air flow at all fuel cell stacks, so that the remaining fuel Shan Chidui in the plurality of fuel cell stacks can furthermore be supplied with an air flow which is optimized for their temperature adjustment.

Advantageously, further stack temperatures of further fuels Shan Chidui of the plurality of fuel cell stacks are detected and the respective stack temperatures are adjusted by means of an adaptation of the air distribution through the air distribution devices of the respective fuels Shan Chidui. In particular, it is possible to set the stack temperature of the fuel Shan Chidui, which is susceptible to deviations in the stack temperature, for example, due to its arrangement in the fuel cell system, for example in particularly cold or particularly warm areas. It is conceivable, for example, that a plurality of fuel cell stacks are arranged directly next to one another. Centrally disposed fuel Shan Chidui has more adjacent fuel Shan Chidui than externally disposed fuel Shan Chidui, so that externally disposed fuel Shan Chidui can cool more rapidly than internally disposed fuel Shan Chidui. It is particularly advantageous to detect the stack temperature of each of the fuel Shan Chidui of the plurality of fuel cell stacks and to adjust the respective stack temperature by means of an adaptation of the air distribution of the respective fuel Shan Chidui. This enables a particularly accurate and optimal operation of all fuel cell stacks, which enables a particularly reliable, durable and efficient operation of the fuel cell device.

Advantageously, at least a second stack temperature of the second fuel Shan Chidui of the plurality of fuel cell stacks is detected, and at least the second fuel Shan Chidui has a second air distribution device, and the second stack temperature is adjusted by means of a second air distribution by the second air distribution device, wherein the first air distribution device and the second air distribution device or the second air distribution device are set during the adjustment in such a way that a total deviation of the first stack temperature and the second stack temperature from a target temperature is minimized. This enables a particularly accurate and optimal operation of all fuel cell stacks, which enables a particularly reliable, durable and efficient operation of the fuel cell device. In particular, the fuel cell stack can be balanced with respect to one another during the adjustment in this way.

By "minimizing the total deviation of the first and second and, if necessary, the third stack temperature from the target temperature" is to be understood in particular that, during the adjustment, each stack temperature is no longer adjusted to the target value, but rather the total deviation of the first and second and, if necessary, the third stack temperature is minimized. In other words, the value of the total deviation, which is a scalar value that depends on the first and second and, if necessary, the third stack temperature, is minimized, adjusted to zero as much as possible. The total deviation can be, for example, the sum of the magnitudes of the respective differences of the stack temperature under consideration with respect to the target temperature. It is also conceivable that the total deviation is the sum of the mean square deviations of the stack temperature under consideration with respect to the target temperature. In principle, different solutions for the total deviation can be envisaged, it being possible in particular to evaluate the temperature deviations of the different fuels Shan Chidui to different extents, so that the deviations from the target temperature of the first stack temperature can be weighted to a greater extent in the total deviation than the deviations from the target temperature of the second stack temperature, for example.

A further improvement can be achieved when the first stack temperature is regulated by means of a first current collection from the first fuel cell stack. In particular, the first stack temperature is regulated by means of the first current collection and the first air distribution device or the first air distribution. In other words, the air supply and the current collection are two operating parameters of the first fuel cell stack, which are adapted as adjustment variables in order to set the stack temperature. In this way a finer adjustment of the stack temperature can be achieved. In particular, the adjustment can then be optimized as a function of the further target parameter. The regulation as a function of the air supply may, for example, lead to an excessively severe power drop of the first fuel cell stack alone, which can be reduced by additionally adapting the first current collection.

Particularly reliable regulation can be achieved by the first current collection when a first fuel cell stack of the plurality of fuel cell stacks is electrically connected in series with the second fuel Shan Chidui and the first current collection is adapted by an adjustable first resistance electrically connected in parallel with the first fuel cell stack. This enables a particularly simple drop in the current through the first fuel cell stack, so that the first current set drops without the current through the second fuel Shan Chidui dropping. Advantageously, second fuel Shan Chidui has an adjustable second resistance that is electrically connected in parallel with second fuel Shan Chidui. In this way, the second current draw of second fuel Shan Chidui can be set, particularly for adjusting the second stack temperature of fuel Shan Chidui. The additional fuel Shan Chidui of the plurality of fuel cell stacks can each be connected in parallel to an associated adjustable resistor, so that a corresponding current collection can be set. It is conceivable that all fuel cell stacks are electrically connected in series. It is also conceivable that a set of fuels Shan Chidui are electrically connected in series. It is particularly conceivable that there are a plurality of groups of fuel cell stacks, wherein the fuels Shan Chidui of one group are electrically connected in series with each other and the groups are electrically connected in parallel with respect to each other.

In a further variant, it is possible for a first fuel cell stack of the plurality of fuel cell stacks to be electrically connected in parallel with a third fuel cell stack and for the first current collection to be adapted by means of an adjustable first dc/dc converter or dc voltage converter electrically connected in series with the first fuel cell stack. This has the additional advantage, inter alia, that: the current draw of the additional fuel Shan Chidui connected in series with the first fuel cell stack can be adjusted or set simultaneously without changing the current draw of the third fuel cell stack and, if necessary, the current draw of the additional fuel Shan Chidui connected in series with the third fuel cell stack. It is conceivable that a group of a plurality of fuel cell stacks are electrically connected in parallel with respect to each other, and each fuel cell stack of the fuel Shan Chidui of the ganged plurality of fuel cell stacks is respectively assigned a dc/dc converter connected in series with the corresponding fuel Shan Chidui. It is also conceivable that there are a plurality of groups of fuel cell stacks, wherein one group of fuels Shan Chidui is electrically connected in series with each other and the groups are electrically connected in parallel with respect to each other, wherein in each group the dc/dc converters are electrically connected in series, respectively.

Advantageously, the power requirements for a plurality of fuel cell stacks are taken into account in the regulation. Typically, it is provided that the fuel cell plant operates on the power requirements provided by a plurality of fuel cell stacks. If the current draw is now reduced, for example in one of the fuel cell stacks, in order to regulate the stack temperature, the electrical power supplied via this fuel cell stack is also reduced. According to this advantageous variant of the method, it is now possible to regulate one or more, advantageously all of the remaining fuel Shan Chidui to a slightly higher current collection, so that the required power can be supplied overall. A slightly higher current pick-up is associated with a corresponding increase in stack temperature, which in the regulation can be adapted by changing further operating parameters of the fuel Shan Chidui, for example by increasing or adapting the total air delivery at all fuel cell stacks.

The method is further improved in the case that: the first current collection and the first air distribution of the first air distribution device are adapted during the regulation in such a way that deviations of the first stack temperature from the target temperature, deviations of the first current collection from the current target value, and deviations of the first air quantity distributed by the first air distribution device from the air target value are minimized. In this way, the regulation of the stack temperature can be further refined, in particular, deviations in the air supply and current collection areas can also be minimized.

By "minimizing the deviation of the first stack temperature from the target temperature, the deviation of the first current collection from the target current value, and the deviation of the first air quantity dispensed by the first air dispensing device from the target air value" is understood, in particular, not only the stack temperature is adjusted to the target value in each case, but also the deviation of the stack temperature, the air quantity, and the current collection from their corresponding target values. Advantageously, for this purpose, the scalar total operating value of the respective deviations of the air quantity and of the current collection from their respective target values as a function of the stack temperature is minimized. For this purpose, the stack temperature, the air quantity and the current are advantageously collected or their respective deviations from the respective target values are converted into dimensionless values which can be converted from one another. In this case, the deviations of the stack temperature, the air quantity and the current collection can be weighted to different extents, in particular, depending on the technical requirements of the current fuel cell system. For example, the deviation of the air amount can be weighted more strongly when the change in the air amount is particularly disadvantageous, or the deviation of the current collection can be weighted more weakly when such deviation can be easily balanced by the other fuel Shan Chidui.

In a further variant, the deviation of the air quantity and the current collection from their respective target values for the stack temperature of at least one further fuel Shan Chidui, advantageously of all fuel cell stacks, is also taken into account in the regulation. For this purpose, for example, a scalar total operating value can be minimized, which is dependent on the respective deviations of the air quantity and the current collection from their respective target values for all stack temperatures of the fuels Shan Chidui under consideration.

It is also advantageous if at least the first fuel cell stack has a first fuel distribution device which is configured to supply the first fuel cell stack with fuel and/or reformed fuel, and wherein the first stack temperature is adjusted by means of the first fuel distribution device. By "adjusting the stack temperature by means of the first fuel distribution device" is understood in particular that the stack temperature is adjusted by adapting the first fuel distribution, wherein the first fuel distribution is provided by the first fuel distribution device. In particular, the first stack temperature is regulated by means of a first fuel distribution or first fuel distribution device and a first air distribution or first air distribution device. In other words, the air and fuel supply are two operating parameters of the first fuel cell stack, which are adapted as adjustment parameters in order to set the stack temperature. In this way can be made more the stack temperature is finely adjusted. In particular, the adjustment can then be optimized as a function of the further target parameter. The regulation as a function of the air supply may, for example, lead to an excessively severe power drop of the first fuel cell stack alone, which can be reduced by additionally adapting the fuel supply. Advantageously, this variant can be improved by additionally using a regulation of the current collection, which variant enables the current collection to be implemented as a further regulation variable for the regulation.

In this context, a "fuel metering device" is understood to mean, in particular, a device which is provided to meter the fuel quantity supplied to the associated fuel Shan Chidui. The fuel dispensing device can, for example, have a settable nozzle or valve that sets the amount of fuel supplied to the fuel Shan Chidui from the fuel inlet line. It is also conceivable that the collection of fuel Shan Chidui has a common fuel supply line, which supplies substantially the same fuel quantity to all fuel cell stacks, and that the first fuel distribution device represents an additional fuel supply for the first fuel cell stack, which supplies an additional, individually settable fuel quantity.

Finer adjustment can be achieved if: the first fuel metering of the first fuel metering device and the first air metering of the first air metering device are adapted during the regulation in such a way that deviations of the first stack temperature from the target temperature, deviations of the first fuel quantity from the fuel target value, and deviations of the first air quantity metered by the first air metering device from the air target value are minimized. For this purpose, a scalar total operating value is advantageously minimized, which is dependent on the respective deviations of the stack temperature, the air distribution and the fuel distribution from their respective target values. The regulation can be further refined if the deviation of the first current collection from the current target value is additionally minimized. For this purpose, a scalar total operating value can be minimized, which is dependent on the respective deviations of the stack temperature, air distribution, fuel distribution and current collection from their respective target values.

Drawings

Embodiments of fuel cell apparatus and methods are illustrated in the accompanying drawings and explained in more detail in the following description. Wherein:

FIG. 1 shows a schematic circuit diagram of a fuel cell device from the prior art

Figure 2 shows a schematic circuit diagram of an embodiment of a fuel cell device,

figure 3 shows a partial view of a circuit diagram of a variant of the fuel cell system,

figure 4 shows a schematic circuit diagram of an embodiment,

figure 5 shows a schematic circuit diagram of a variant of a fuel cell device,

FIG. 6 shows a method according to the invention, and

fig. 7 shows a partial view of a circuit diagram of a further variant of a fuel cell system.

Detailed Description

The same reference numerals are given to the same components in different design variants.

In fig. 1 a schematic circuit diagram of a fuel cell device 10 from the prior art is shown. The fuel cell apparatus 10 illustratively includes two fuel cell units 12, a first fuel cell unit 12a and a second fuel cell unit 12b.

Furthermore, the fuel cell device 10 comprises a plurality of processor units 14. One of the processor units 14 is a heat exchanger 18 arranged in the air conveying section 16 for warming the oxygen-containing air L supplied to the fuel cell unit 12. In the present case, air L is supplied, for example, in normal operation to the cathode spaces 20 of the fuel cell units 12, respectively, while reformed fuel RB, currently hydrogen, is supplied to the anode spaces 22, respectively. The reformed fuel RB is electrochemically converted in the fuel cell unit 12 by the combined action of oxygen from the air L under the generation of electric current and heat.

The reformed fuel RB is produced by: the fuel cell device 10 is supplied with fuel B, in the present case by way of example natural gas, via a fuel supply 24, which fuel is reformed in the further processor unit 14 (in the present case the reformer 26).

The term "fuel supply" is understood to mean, in particular, a line for a fluid or a gas, which is provided for guiding a preferably gaseous fuel during normal operation of the fuel cell system. However, it is also conceivable that the fuel supply leads further gas, for example reformed fuel or anode exhaust gas or air, in particular from the anode recirculation circuit, during a start-up or heating operation or during a shut-down or cooling operation. For example, the fuel delivery section can have one tube or a plurality of tubes. The fuel delivery portion is supplied with fuel from a fuel source.

"fuel source" is understood to be the source of fuel for supply to the fuel cell apparatus. For example, the fuel source can be a fitting for a fuel input line, for example from a natural gas network or from the outside of a hydrogen cylinder. The fuel can be, for example, natural gas, hydrogen or a mixture of natural gas and hydrogen. In a variant, other fuels and mixtures of fuels are also conceivable, for example fuel B can have natural gas, hydrogen, methane, ammonia and/or gas or synthesis gas.

In this context, a "recirculation circuit" or "anode recirculation circuit" is to be understood in particular to mean a fluid connection or a fluid path which is provided for supplying the fuel-containing or hydrogen-containing and water-containing anode exhaust gas of the at least one fuel cell stack to a mixing point at which the anode exhaust gas is mixed with at least substantially pure fuel or hydrogen. In particular, a recirculation circuit is provided for the renewed supply of unconverted fuel or hydrogen to the fuel Shan Chidui on the anode side. In particular, a mixture of anode exhaust gas and fuel or hydrogen is provided for supplying fuel Shan Chidui on the anode side. The compressor can be configured, for example, as a fan.

An "anode exhaust gas guide" is to be understood in particular as a line for the anode exhaust gas from the fuel cell stack. For example, the anode exhaust gas guide can have one tube or a plurality of tubes.

Typically, the reformer is connected before the fuel cell stack. A "reformer" or "reforming unit" is understood in this connection to mean in particular a unit in chemical technology for at least the treatment of at least one hydrocarbon-containing fuel, in particular for the capture of at least one fuel gas, in particular hydrogen, and/or for the decomposition of higher olefins, in particular by steam reforming and/or by partial oxidation and/or by autothermal reforming.

Thus, in operation fuel is first directed into the reformer through the fuel delivery and subsequently the reformed fuel is directed into the fuel cell stack. The fuel cell system preferably has at least one reformer which is fluidically connected to all fuel cell stacks and is connected in particular upstream of the fuel cell stacks.

Furthermore, the fuel cell unit 12 is connected on the exhaust gas side to a further processor unit 14, in the present case to a afterburner 28. The exhaust gas of the fuel cell unit 12 is supplied to a afterburner 28, to which in the present case the cathode exhaust gas KA is supplied via a cathode exhaust gas guide 30 and a portion of the anode exhaust gas AA is supplied via an anode exhaust gas guide 32. The cathode exhaust gas KA comprises unconsumed air L or unconsumed oxygen, while the anode exhaust gas AA comprises optionally unconverted, reformed fuel RB and/or optionally unconverted fuel B. In the case of mixing the oxygen contained therein of the cathode exhaust gas KA or the air L, the anode exhaust gas AA or optionally the unconverted, reformed fuel RB and/or optionally the unconverted fuel B contained therein is combusted by means of the afterburner 28, as a result of which additional heat can be generated.

The hot exhaust gas a formed during combustion in the afterburner 28 is led out of the afterburner 28 by means of an exhaust gas guide 34 via the further processor unit 14, in the present case via a heat exchanger 36. The heat exchanger 36 is in turn connected to the reformer 26 in terms of flow technology, so that the heat of the hot exhaust gas a is transferred to the fuel B supplied to the reformer 26. The heat of the hot exhaust gas a can be correspondingly used for reforming the fuel B supplied in the reformer 26.

Downstream of the heat exchanger 36, in the exhaust gas guide 34, a further processor unit 14, in the present case a heat exchanger 18, is present, so that the remaining heat of the hot exhaust gas a can be transferred to the supplied air L in the air conveying section 16. Correspondingly, the remaining heat of the hot exhaust gases can be used to preheat the supplied air L in the air conveying section 16.

Furthermore, the fuel cell system 10 has a return 38, by means of which a part of the anode exhaust gas AA can be branched off from the anode exhaust gas guide 32 and supplied to the anode recirculation circuit 40. The branched anode exhaust gas AA passes here through a further processor unit 14, in the present case a further heat exchanger 39.

The branched part of the anode exhaust gas AA can be returned or re-supplied to the respective anode space 22 of the fuel cell unit 12 and/or to the reformer 26 by means of the anode recirculation circuit 40, so that the unconverted reformed fuel RB, if appropriate, included in the branched anode exhaust gas AA can be converted later in the fuel cell unit 12 and/or the unconverted fuel B, if appropriate, included in the branched anode exhaust gas AA can be reformed later in the reformer 26. Further, the fresh fuel B can be mixed with the branched anode off-gas AA recirculated in the anode recirculation loop 40 by the fuel delivery portion 24. The heat of the branched anode exhaust gas AA can then be transferred from the return 38 to the fuel mixture in the anode recirculation circuit 40, which is formed by mixing the fresh fuel B, for the purpose of the heat treatment by means of a further heat transfer 39.

The delivery of air L in air delivery section 16, the delivery of fuel B in fuel delivery section 24, and the recirculation rate of anode exhaust gas AA in anode recirculation loop 40 can be regulated and/or matched to each other by compressors 42 in the respective lines.

Furthermore, the fuel cell system 10 has a heating element 44 for additionally heating the air L supplied to the fuel cell unit 12 in the bypass line 46 in the present case, as a result of which the operating efficiency of the fuel cell system 10 is increased.

Fig. 2 shows a schematic circuit diagram of a fuel cell device 10 according to the invention. The fuel cell device 10 has a very similar structure to the embodiment shown in fig. 1 from the prior art and is expanded with additional components. The fuel cell system 10 likewise comprises a first fuel cell unit 12a and a second fuel cell unit 12b embodied as a fuel cell stack 12 having a plurality of fuel cells, in the present case solid oxide fuel cells (solid oxide fuel cell, SOFC). The first fuel cell unit 12a is in the embodiment shown in fig. 2a first fuel cell stack 12a. The second fuel cell unit 12b is a second fuel Shan Chidui b in the embodiment shown in fig. 2.

Furthermore, the fuel cell device 10 comprises a plurality of processor units 14. The term "processor unit 14" is understood within the framework of the present invention to mean in particular a unit or component of the fuel cell system 10, which is not a fuel cell unit 12. In the present case, the processor unit 14 is a unit for chemically and/or thermally pre-and/or post-treating at least one medium to be converted and/or converted in the fuel cell unit 12, such as, for example, fuel gas, air and/or exhaust gas.

One of the processor units 14 is a heat exchanger 18 arranged in the air conveying section 16 for warming the oxygen-containing air L supplied to the fuel cell unit 12. In the present case, air L is supplied, for example, in normal operation, to the cathode space 20 of the fuel cell unit 12, respectively, while reformed fuel RB, currently hydrogen, is supplied to the anode space 22, respectively. The reformed fuel RB is electrochemically converted in the fuel cell unit 12 by the combined action of oxygen from the air L under the generation of electric current and heat.

The reformed fuel RB is produced by: the fuel B, in the present case natural gas, is supplied to the fuel cell arrangement 10 by way of the fuel feed 24, which fuel is reformed in the further processor unit 14, in the present case in the reformer 26.

Furthermore, the fuel cell unit 12 is connected on the exhaust gas side to a further processor unit 14, in the present case to a afterburner 28. The exhaust gas of the fuel cell unit 12 is supplied to a afterburner 28, to which a part of the cathode exhaust gas KA is supplied in the present case via a cathode exhaust gas guide 30 and a part of the anode exhaust gas AA is supplied via an anode exhaust gas guide 32. The cathode exhaust gas KA comprises unconsumed air L or unconsumed oxygen, while the anode exhaust gas AA comprises optionally unconverted reformed fuel RB and/or optionally unconverted fuel B. In the case of mixing the oxygen contained therein of the cathode exhaust gas KA or the air L, the anode exhaust gas AA or optionally the unconverted reformed fuel RB and/or optionally the unreformed fuel B contained therein is combusted by means of the afterburner 28, as a result of which additional heat can be generated.

The hot exhaust gas a formed in the afterburner 28 during combustion is led out of the afterburner 28 by an exhaust gas guide 34 via the further processor unit 14, in the present case via a heat exchanger 36. The heat exchanger 36 is in turn connected to the reformer 26 in terms of flow technology, so that the heat of the hot exhaust gas a is transferred to the fuel B supplied to the reformer 26. Correspondingly, the heat of the hot exhaust gas a can be used for reforming the supplied fuel B in the reformer 26.

A first injector 62a is arranged at the air supply 16 of the first fuel cell stack 12a immediately in front of the first fuel cell stack 12 a. In particular, the first injector 62a is disposed upstream of the first fuel cell stack 12 a.

According to the invention, the fuel cell system 10 has a first cathode return 64a, by means of which a part of the cathode exhaust gas KA can be supplied directly from the anode exhaust gas guide 32 at the first fuel cell stack 12a to the first injector 62a. The rest of the AA of the cathode exhaust gas is led in the afterburner 28.

In this way, the branched part of the cathode exhaust gas KA can be returned or re-supplied to the respective cathode space 20 of the first fuel cell unit 12a by means of the first cathode return 64a and the first injector 62a, so that the unconverted oxygen, if necessary, included in the branched cathode exhaust gas KA can be converted later in the first fuel cell unit 12 a. In particular, however, the heat of the cathode exhaust gas KA can in this way be led back directly into the first fuel cell unit 12 a. Thereby enabling further improvement in the efficiency of the fuel cell apparatus 10.

In order to be able to effectively inject the cathode exhaust gas KA supplied to the first injector 62a via the first cathode return 64a into the air flow L, the air L should have an increased pressure at the first injector 62 a. The increased pressure of the air L can be provided, for example, by a compressor 42 in the air delivery portion 16. Advantageously, the pressure of the air L is at least 2bar, preferably greater than 3bar, particularly preferably greater than 5bar, in particular in the air conveying section 16 at the first injector 62 a.

In the embodiment shown in fig. 2, a second injector 62b is furthermore exemplarily arranged immediately in front of the second fuel Shan Chidui b at the air supply 16 of the second fuel Shan Chidui b. In particular, the second injector 62b is disposed upstream of the second fuel Shan Chidui b.

The fuel cell apparatus 10 illustratively has a second cathode return 64b, by means of which a part of the cathode exhaust gas AA can be supplied directly from the anode exhaust gas guide 32 at the second fuel Shan Chidui b to the first injector 62b. The other part of the anode exhaust gas AA is led in a afterburner 28.

In this way, the branched part of the anode exhaust gas AA can be returned or re-supplied to the corresponding cathode space 20 of the second fuel cell unit 12b by means of the second return portion 38b and the second injector 62a, so that the unconverted oxygen, if necessary, included in the branched cathode exhaust gas KA can be converted later in the second fuel cell unit 12 b. In particular, the heat of the cathode exhaust gas KA can then also be returned directly to the second fuel cell unit 12b in this way. Thereby enabling further improvement in the efficiency of the fuel cell apparatus 10.

Furthermore, the fuel cell system 10 has a heating element 44 for additionally heating the air L supplied to the fuel cell unit 12 in the bypass line 46 in the present case, as a result of which the operating efficiency of the fuel cell system 10 is increased, in particular in the heating operation of the fuel cell system 10.

The first fuel cell stack 12a has, by way of example, a first temperature sensor 48a, which is arranged at the first fuel cell stack 12a at the cathode exhaust gas outlet of the cathode exhaust gas guide 30. Thus, the first temperature sensor 48a detects, among other things, the temperature of the cathode exhaust gas KA at the first fuel cell stack 12a, which is a good approximation of the first stack temperature.

The second fuel Shan Chidui b illustratively has a second temperature sensor 48b, which is disposed at the cathode exhaust gas outlet of the cathode exhaust gas guide 30 at the second fuel Shan Chidui b. Thus, the second temperature sensor 48b detects, among other things, the temperature of the cathode exhaust gas KA at the second fuel Shan Chidui b, which is a good approximation of the second stack temperature.

As can be clearly seen, in the exemplary embodiment two fuel cell stacks 12 are supplied with air L via the air supply 16 and the compressor 42. The two fuel cell stacks 12 are fluidly coupled in parallel by an air delivery 16. Thus, the two fuel cell stacks 12 have a common air supply 16, 42. The two fuel cell stacks 12 therefore have a common air supply, wherein the air L fed by the compressor 42 is guided to the respective fuel Shan Chidui by two air feeds 16 which are fluidically connected to one another. The same air flow L is largely provided by the common air supply 16, in particular at the two fuel cell stacks 12. The two fuel cell stacks 12 are in particular supplied with a largely identical basic quantity of air L via the common air supply 16, 42 in the exemplary embodiment shown.

In the exemplary embodiment shown in fig. 2, the two fuel cell stacks 12 are supplied with fuel B or reformed fuel RB via a fuel supply and an exemplary reformer 26. In this case, the fuel B or the reformed fuel RB is transported by the compressor 42 at the fuel supply. Here, in an embodiment, the fuel Shan Chidui is fluidly coupled in parallel with the reformer 26. Thus, the two fuel cell stacks 12 have a common fuel supply 24, 26, 42. These common fuel supplies 24, 26, 42 in the illustrated embodiment provide the two fuel cell stacks 12 with a largely identical base amount of fuel B.

In other words, the two fuel cell stacks 12 have a common fuel supply, wherein the fuel B or the reformed fuel RB fed by the compressor 42 is guided to the respective fuel Shan Chidui by two fuel feed portions 24 that are fluidically connected in parallel to each other. The common fuel supply 24 provides a largely identical fuel flow B or a reformed fuel flow RB, in particular at the two fuel cell stacks 12.

Fig. 3 shows a variant of the embodiment from fig. 2. For clarity, only fuel Shan Chidui 12 is depicted, as well as the lines 16, 30 connected to fuel Shan Chidui and the directly fluidly connected components. Unlike the embodiment of fig. 2, the fuel cell system 10 has three fuel cell stacks 12 instead of two, that is to say there is an additional third fuel cell stack 12c in the variant depicted in fig. 3. Each of the three fuel cell stacks 12a, 12b, 12c has a cathode return 64a, 64b, 64c, respectively, which is connected to the cathode exhaust gas guide 30 of the respective fuel Shan Chidui. Furthermore, each of the three fuel cell stacks 12a, 12b, 12c has an injector 62a, 62b, 62c, respectively, which is connected in the respective air supply 16 upstream of the respective fuel Shan Chidui a, 12b, 12c and to which a respective cathode return 64a, 64b, 64c is connected.

In the embodiment shown in fig. 3, the first fuel cell stack 12a has an additional first air distribution device 60a. The first air distribution device 60a is arranged at the air supply 16, wherein the first air distribution device 60a is connected to the first fuel cell stack 12a in terms of flow technology shortly before the connection of the air supply 16. Illustratively, the first air distribution device 60a is fluidly connected immediately before the first ejector 62 a. The first air distribution device 60a is configured in such a way that air L is introduced into the air supply L immediately before the first fuel cell stack 12a in the flow direction, so that in particular air L introduced via the first air distribution device 58a is introduced into the first fuel cell stack 12 a. The first air distribution device 60a is provided for, an individually settable air quantity L or air supply is set for the first fuel cell stack 12 a. Illustratively, the first air distribution device 60a is configured as an adjustable valve that is disposed in the flow path of the air delivery portion 16. It is also conceivable for the first air distribution device 60a to be configured as an adjustable throttle in the air delivery section 16.

For example, the second fuel Shan Chidui b in the exemplary embodiment shown in fig. 3 has an additional second air supply device 60b, which is provided for supplying the second fuel Shan Chidui b with an air quantity L or air supply that can be individually supplied. The second air distribution device 60b is fluidically connected to the air supply 16, wherein the second air distribution device 60b is fluidically connected to the second fuel Shan Chidui b immediately upstream of the second injector 62 b.

The third fuel cell stack 12c has, for example, in the exemplary embodiment shown in fig. 3, an additional third air distribution device 60c which is provided for supplying the third fuel cell stack 12c with an individually dispensable air quantity L or air distribution. The third air distribution device 60c is fluidically connected to the air supply 16, wherein the third air distribution device 60c is fluidically connected to the third fuel cell stack 12c immediately upstream of the third injector 62 c.

Fig. 4 illustrates the circuit of two fuel cell units 12 or fuels Shan Chidui from the embodiment shown in fig. 2. The first fuel cell stack 12a is connected in series with the second fuel Shan Chidui b in the illustrated embodiment. Illustratively, a DC/AC converter 50 is connected in series with the two fuel cell stacks 12. The dc/ac converter is provided in particular for converting the dc voltage generated by the fuel Shan Chidui into an ac voltage.

The first fuel cell stack 12a has an adjustable first electrical resistance 52a electrically connected in parallel with the first fuel cell stack 12 a. Illustratively, the second fuel Shan Chidui b also has an adjustable second electrical resistance 52b electrically connected in parallel with the second fuel Shan Chidui b. In this way, the first stack temperature can additionally also be adjusted by setting the first current collection via the first resistor 52 a. Further, the second stack temperature of the second fuel Shan Chidui b can additionally be adjusted by setting a second current pickup from the second fuel Shan Chidui b via the second resistor 52 b.

However, it is also conceivable that only the first fuel cell stack 12a has a first electrical resistance 52a and the second fuel Shan Chidui b does not. The regulation of the stack temperatures can be performed, for example, in such a way that the second stack temperature is achieved first by setting the common air supply 16, 42 and the first stack temperature is then achieved by setting the first current collection via the first resistor 52 a.

Fig. 5 shows an alternative embodiment, in which the fuel cell device 10 has four fuel cell stacks 12. Illustratively, the first fuel cell stack 12a and the second fuel Shan Chidui b are electrically connected in series relative to each other, and the third fuel cell stack 12c and the fourth fuel cell stack 12d are electrically connected in series relative to each other. An adjustable first resistor 52a is connected in series with the first fuel cell stack 12a and is configured to adjust the first stack temperature. An adjustable second resistor 52b is connected in series with the second fuel Shan Chidui b, the second resistor being configured to adjust the second stack temperature. An adjustable third resistor 52c is connected in series with the third fuel cell stack 12c and is configured to adjust a third stack temperature of the third fuel cell stack 12 c. An adjustable fourth resistor 52d is connected in series with the fourth fuel cell stack 12d and is configured to adjust a fourth stack temperature of the fourth fuel cell stack 12 d.

Furthermore, a first dc/dc converter 54a is electrically connected in series with the first fuel cell stack 12a, and illustratively with the second fuel Shan Chidui b. Illustratively, the second DC/DC converter 54b is electrically connected in series with the third fuel cell stack 12c and the fourth fuel cell stack 12 d. Here, the first fuel cell stack 12a, the second fuel Shan Chidui b, and the first dc/dc converter 54a are electrically connected in parallel with the third fuel cell stack 12c, the fourth fuel cell stack 12d, and the second dc/dc converter 54 b. The dc/dc converter 54 is provided here for regulating or setting the current or the current pickup thereof via the fuel Shan Chidui, which is associated with the dc/dc converter in each case in series connection. In particular, a first DC/DC converter 54a is provided for setting a first current draw from the first fuel cell stack 12 a. The current wires are then gathered after the two dc/dc converters 54 and connected to the dc/ac converter 50.

In this way, it is particularly possible, for example, to change the first current draw at the first fuel cell stack 12a via the first dc/dc converter 54a, without changing the third current draw at the third fuel cell stack 12c, which is electrically connected in parallel with the first fuel cell stack 12a and the first dc/dc converter 54 a. This enables the stack temperature of the fuels Shan Chidui electrically connected in parallel to each other to be individually adjusted by adapting the current collection via the respective dc/dc converter 54.

The dc/dc converter 54 in particular allows the current or current tap at all fuel cell stacks 12 electrically connected in series with the dc/dc converter 54 to be changed. Furthermore, by means of the adjustable resistor 52a in the variant shown in fig. 5, individual current collection can be specifically changed at the individual fuel cell stacks 12 within a group of fuel Shan Chidui electrically connected in series. For example, it is conceivable in the variant shown in fig. 5 to first set the second stack temperature of the second fuel Shan Chidui b by adapting the second current tap by means of the first dc/dc converter 54a and then to set the first stack temperature of the first fuel cell stack 12a by adapting the first current tap by means of the first resistor 52 a.

Further variants are conceivable in which, for example, groups of two, three or more fuel cell stacks 12 are each electrically connected in series with a dc/dc converter 54, and a plurality of such groups are electrically connected in parallel with respect to one another. The fuels Shan Chidui in such groups can advantageously each have an adjustable electrical resistance 52 electrically connected in parallel.

Fig. 6 illustrates a method 56 for regulating a first stack temperature of the first fuel cell stack 12a of the fuel cell device 10 shown in fig. 3. For this purpose, in a first step S1, a first stack temperature is determined. To this end, the temperature is illustratively received by the first temperature sensor 48a and used as the first stack temperature. Subsequently, the first stack temperature is compared with a target value in a second step. The target value is illustratively 615 ℃. If the first stack temperature does not deviate more severely from the tolerance value exceeding the target value, the method 56 proceeds again with step S1 via path A. The tolerance value is illustratively 5 ℃. If the stack temperature deviates from the tolerance value beyond the target value, the method 56 continues with step S3 via path B.

The first air ration is changed by the first air ration device 58a in step S3. If the first stack temperature determined in step S1 is less than the target value, the first air supply is reduced. If the first stack temperature determined in step S1 is greater than the target value, the first air supply is increased. In this case, the increase or decrease in the first air supply can take place either with a predetermined absolute value or with a relative value as an amplitude. It is also conceivable to increase or decrease the first air supply in dependence on the magnitude of the deviation of the first stack temperature from the target value, for example to increase or decrease the first air supply more severely in the case of more severe deviations. The method then proceeds again with step S1.

It is conceivable in step S2 to count (Anzahl) too severe deviations of the determined first stack temperatures from one another, for example with an error counter, and to implement a fault response, for example to shut down the first fuel cell stack 12a, if a critical number of errors, for example ten times, are determined. It is also conceivable to detect in step S2 or in a further step following step S1 whether the ascertained stack temperature is below a lower critical value or exceeds an upper critical value and, if so, to implement a fault response.

In a variant of the method 56, it is conceivable that if the first stack temperature determined in step S1 is greater than the target value, then in step S2 the first air supply is increased, in particular in that: the first amount of air dispensed by the first air dispensing device 60a of the first fuel cell stack 12a is increased. If the first stack temperature determined in step S1 is less than the target value, then further operating parameters of the first fuel cell stack 12a are changed, for example the fuel supply 24, 26, 42 common to all fuel cell stacks 12 is set such that the fuel flow is reduced, for example: by reducing the fan speed; and/or by increasing the first current draw from the first fuel cell stack 12 a; and/or by reducing the amount of first fuel dispensed by the first fuel dispensing device 58a of the first fuel cell stack 12a (see fig. 7). It is also conceivable that the first dc/dc converter 54a is electrically connected in series with the first fuel cell stack 12a, and that the first current collection is increased in step S2 when the first stack temperature determined in step S1 is smaller than the target value, by: the current through the first fuel cell stack 12a is increased by the first dc/dc converter 54 a.

In the variant shown in fig. 7, the first fuel cell stack 12a has an additional first fuel distribution device 58a. The first fuel distribution device 58a is fluidically connected to the fuel supply 24, wherein the first fuel distribution device 58a is fluidically connected to the first fuel cell stack 12a shortly before the connection of the fuel supply 24. The first fuel distribution device 58a is configured in such a way that the fuel B and/or the reformed fuel RB is introduced into the fuel supply 24 shortly before the first fuel cell stack 12a in the flow direction, so that in particular the fuel B or the reformed fuel RB introduced via the first fuel distribution device 58a is introduced into the first fuel cell stack 12a. It is also contemplated that the first fuel dispensing device 58a is directly connected to the fuel Shan Chidui a. The first fuel metering device 58a is provided for delivering a fuel quantity B which can be metered individually to the first fuel cell stack 12a. In this way, the fuel quantity guided by the fuel supply 24 jointly at all fuel cell stacks 12 can be adapted to the extent of the additional fuel quantity.

It is contemplated that first fuel dispensing device 58a is coupled to reformer 26 as is common fuel delivery portion 24. The first fuel dispensing device 58a can have its own compressor 42. It is also contemplated that the first fuel dispensing device 58a has its own reformer 26. It is also contemplated that the first fuel dispensing device 58a has its own fuel source that is different from the fuel source of the common fuel supply 24. In an alternative variant, it is possible for the first fuel metering device 58a to be configured as an adjustable metering valve or an adjustable throttle in the fuel supply 24 upstream of the first fuel cell stack 12a, so that the fuel quantity B delivered to the first fuel cell stack 12a via the common fuel supply 24 can be adapted by means of the metering valve or the throttle without changing the fuel quantity B delivered to the second fuel Shan Chidui B.

In the variant shown in fig. 7, the second fuel Shan Chidui B has an additional second fuel metering device 58B, which is provided for supplying the individualizing metered fuel quantity B to the second fuel Shan Chidui B. The second fuel distribution device 58b is fluidically connected to the fuel supply 24, wherein the second fuel distribution device 58b is fluidically connected to the second fuel Shan Chidui b shortly before the connection of the fuel supply 24.

Claims

1. Fuel cell system (10) having a plurality of fuel cell stacks (12), wherein the fuel Shan Chidui (12) is connected to an air supply (16) and to a cathode exhaust gas guide (30), wherein a first cathode return (64 a) is connected to the cathode exhaust gas guide (30) at least one first fuel cell stack (12 a), which is designed to branch off a portion of the cathode exhaust gas (KA) discharged from the first fuel cell stack (12 a) by the cathode exhaust gas guide (30), characterized in that a first injector (62 a) is connected in front of the first fuel cell stack (12 a) in the air supply (16), and the first cathode return (64 a) is connected to the first injector.

2. The fuel cell arrangement (10) according to claim 1, characterized in that at each fuel cell stack (12) of the plurality of fuel cell stacks (12), a respective cathode return (64 a, 64b, 64 c) associated with the fuel Shan Chidui (12 a, 12b, 12 c) is connected to the cathode exhaust gas guide (30), which is connected to an injector (62 a, 62b, 62 c) connected in the air delivery (16) in front of the respective fuel Shan Chidui (12 a, 12b, 12 c), respectively.

3. Fuel cell device (10) according to one of the preceding claims, characterized in that a first air distribution device (60 a) is connected in the air delivery section (16) upstream of the first injector (62 a), which is configured for supplying air (L) to the first fuel cell stack (12 a), preferably an associated air distribution device (60 a, 60b, 60 c) is connected in the air delivery section (16) upstream of each injector (62 a, 62b, 62 c) respectively associated with a fuel cell stack (12 a, 12b, 12 c).

4. A fuel cell device (10) according to claim 3, characterized in that at least the first fuel cell stack (12 a) has a first temperature sensor (48 a) for detecting a first stack temperature, wherein the fuel cell device (10) has a controller configured for receiving the first stack temperature, and wherein the controller is provided for setting a first air dosing for the first fuel cell stack (12 a), and wherein the controller is provided for adjusting the first stack temperature by means of the first air dosing device (60 a).

5. The fuel cell arrangement (10) according to claim 4, characterized in that the first temperature sensor (48 a) is arranged at a cathode exhaust gas guide (30) at the first fuel cell stack (12 a).

6. The fuel cell arrangement (10) according to any one of the preceding claims, wherein the plurality of fuel cell stacks (12) have a common fuel supply (24, 26, 42).

7. Method (56) for adjusting at least one stack temperature of a fuel cell device (10), in particular of a fuel cell device (10) according to one of the preceding claims, wherein the fuel cell device (10) has a plurality of fuel cell stacks (12), wherein at least a first stack temperature of a first fuel cell stack (12 a) of the plurality of fuel cell stacks (12) is detected, characterized in that at least the first fuel cell stack (12 a) has a first air distribution device (60 a) which is configured for supplying air (L) to the first fuel cell stack (12 a) and the first stack temperature is adjusted by means of a first air distribution by the first air distribution device (60 a).

8. The method (56) of claim 7, wherein at least a second stack temperature of a second fuel Shan Chidui (12 b) of the plurality of fuel cell stacks (12) is detected, and at least the second fuel Shan Chidui (12 b) has a second air distribution device (60 b), and the second stack temperature is adjusted by means of a second air distribution by the second air distribution device (60 b), wherein the first air distribution or the first air distribution device (60 a) and the second air distribution or the second air distribution device (60 b) are set during the adjustment such that a total deviation of the first stack temperature and the second stack temperature from a target temperature is minimized.

9. The method (56) of any of claims 7 or 8, wherein the first stack temperature is adjusted by means of a first current collection from the first fuel cell stack (12 a).

10. The method (56) of claim 9, wherein the first fuel cell stack (12 a) is electrically connected in series with the second fuel Shan Chidui (12 b) of the plurality of fuel cell stacks (12) and the first current draw is adapted by an adjustable first resistance (52 a) electrically connected in parallel with the first fuel cell stack (12 a).

11. The method (56) of any of claims 9 to 10, wherein the first fuel cell stack (12 a) is electrically connected in parallel with a third fuel cell stack (12 c) of the plurality of fuel cell stacks (12), and the first current collection is adapted by an adjustable first direct current/direct current converter (54 a) electrically connected in series with the first fuel cell stack (12 a).

12. The method (56) of any of claims 9 to 11, wherein the first current draw and the first air dosing of the first air dosing device (60 a) are adapted upon conditioning such that a deviation of the first stack temperature from a target temperature, a deviation of the first current draw from a current target value, and a deviation of a first amount of air dosed by the first air dosing device (60 a) from an air target value are minimized.

13. The method (56) of any of claims 9 to 12, wherein at least the first fuel cell stack (12 a) has a first fuel dosing device (58 a) configured for supplying the first fuel cell stack with fuel (B) and/or reformed fuel (RB), and wherein the first stack temperature is adjusted by means of the first fuel dosing device (58 a).

14. The method (56) of claim 13, wherein the first fuel dosing of the first fuel dosing device (58 a) and the first air dosing of the first air dosing device (60 a) are adapted when adjusted such that a deviation of the first stack temperature from a target temperature, a deviation of the first fuel dosing dosed by the fuel dosing device (58 a) from a fuel target value, and a deviation of the first air dosing from an air target value are minimized.