Fuel cell system

Abstract

The present invention relates to a fuel cell system (100) for generating electric current, having at least one fuel cell stack (110), the fuel cell stack (110) having an air side (120) and a fuel side (130) and the air side (120) having an air supply section (122) for supplying supply air (ZL) to the air side (120) and an exhaust air discharge section (124) for discharging exhaust air (AL) from the air side (120), and furthermore the fuel side (130) having a fuel supply section (132) for supplying fuel (BS) to the fuel side (130) and an exhaust gas discharge section (134) for discharging exhaust gas (AG) from the fuel side (130), a compressor device (140) being arranged in the air supply section (122) for compressing the supply air (ZL), a supply air / exhaust air heat exchanger (150) being arranged downstream of this compressor device (140) for transferring heat from the supply air (ZL) to the exhaust air (AL).

Description

[0001] Fuel cell system

[0002] The present invention relates to a fuel cell system for generating electrical power and a control method for controlling such a fuel cell system.

[0003] It is generally known that fuel cell systems are used to generate electrical power. For this purpose, such fuel cell systems are usually equipped with one or more fuel cell stacks. Such a fuel cell stack is a combination of a large number of individual fuel cells arranged one above the other in a stack. In terms of process technology, a fuel cell stack can usually be divided into an air side and a fuel side. Thus, supply air, usually from the environment, is supplied on the air side. Fuel, for example, hydrogen or natural gas or similar gaseous fuels, is supplied on the fuel side. Fuel cell functionality is provided by the arrangement of a fuel cell membrane in each fuel cell in the fuel cell stack.This means that a controlled chemical reaction is carried out through the catalytic conversion of the fuel using the supply air, resulting in a current flow. The resulting chemical reaction products are discharged from the fuel cell stack as exhaust air from the exhaust air side and as exhaust gas from the fuel side. Typically, both the exhaust air and the exhaust gas are vented to the environment.

[0004] A disadvantage of the known solutions is that a large proportion of the components in the fuel cell system are temperature-sensitive. This means that coolant circuits are usually provided to specifically keep the individual components within the desired temperature ranges and, in particular, to protect them from undesired overheating. A key component here is the need to cool the supply air. For example, the supply air is usually pressurized by a compressor device, thus generating the volume flow of supply air through the fuel cell stack. When the supply air is compressed, it heats up due to the increase in pressure according to the law of ideal gases. Depending on the current application situation, this heating can lead to supply air temperatures downstream of the compressor that exceed a desired upper limit.In order to prevent the supply air from being fed into the fuel cell stack which is overheated due to compression, i.e. with a temperature above the temperature limit, known fuel cell systems have cooling elements which enable the supply air to be cooled by external liquid cooling with the aid of a connection to a coolant circuit.

[0005] The need to cool the supply air brings with it a number of disadvantages. Firstly, a heat transfer option for cooling the supply air and absorbing the heat in the coolant must be provided, both structurally and in terms of installation space. Furthermore, the heated coolant must be further transported and the absorbed heat dissipated to the environment. This requires cooling energy, which reduces the operating efficiency of the entire fuel cell system. Last but not least, this also increases the complexity of control, as the coolant circuit must also accommodate the cooling requirements and the cooling needs of the supply air in a controlled manner.

[0006] The object of the present invention is to at least partially resolve the problems described above in a cost-effective and simple manner. In particular, the object of the present invention is to increase the operating efficiency of a fuel cell system in a cost-effective and simple manner.

[0007] The above object is achieved by a fuel cell system having the features of claim 1 and a control method having the features of claim 12. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the fuel cell system according to the invention naturally also apply in connection with the control method according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0008] According to the invention, a fuel cell system serves to generate electrical power. For this purpose, this fuel cell system is equipped with at least one fuel cell stack. This fuel cell stack, which has a plurality of fuel cells arranged one above the other in a stacked manner, can be distinguished into an air side and a fuel side. The air side has an air supply section for supplying supply air to this air side. Furthermore, an exhaust air discharge section is provided for discharging exhaust air from the air side. On the fuel side, a fuel supply section is provided for supplying fuel to the fuel side. Likewise on the fuel side, an exhaust gas discharge section is provided for discharging exhaust gas from the fuel side. According to the invention, a compressor device for compressing the supply air is arranged in the air supply section.Downstream of this compressor device, a supply air-exhaust air heat exchanger is arranged for heat transfer from the supply air to the exhaust air.

[0009] A fuel cell system according to the invention is based on the known technological considerations for fuel cell systems. Reference is made here to the known implementations, so no further detailed information regarding valves, heat exchangers, or other operating components of the fuel cell system is included. The core idea of ​​the present invention is that a compressor device is also used to ensure the conveying and pressurization of the supply air. In the air supply section, air can be drawn in as supply air, for example, from the environment. The intake and conveying takes place with the compressor device, in which, for example, a compressor applies the desired conveying energy and compression energy to the air.

[0010] The operation of the compressor device not only conveys the supply air, but the increase in pressure also heats the supply air during this compression according to the law of ideal gases. The outlet temperature from the compressor device and thus the temperature of the supply air downstream of the compressor device is now significantly higher than the ambient temperature of the ambient air. In order to ensure in a known manner that this supply air does not reach the fuel cell stack at an undesirably high temperature, i.e. in particular not in an overheated state above an upper limit for the supply air temperature, an internal cooling option is now integrated into the fuel cell system according to the invention. This internal cooling option is provided by the supply air-exhaust air heat exchanger. This allows heat to be transferred from the supply air to the exhaust air, particularly as a gas-gas heat exchanger.The exhaust air is the amount of gas that is returned to the environment from the air side. Typically, the exhaust air is cooler than the supply air. The temperature difference between the superheated supply air in the air supply section and the exhaust air in the exhaust air discharge section allows for internal cooling.

[0011] The temperature gradient between the supply air and exhaust air is utilized structurally by bringing these two gas streams into heat-transfer contact. The supply air-exhaust air heat exchanger serves this purpose. The supply air side of the supply air-exhaust air heat exchanger thus represents the hot side, and the exhaust air side of the supply air-exhaust air heat exchanger represents the cold side of this heat exchanger component. In other words, the supply air is now compressed and heated by compression. The heated supply air is then passed downstream of the compressor device via the supply air-exhaust air heat exchanger, through which the exhaust air flows, particularly in counterflow, and can absorb some of the heat from the supply air. Since the exhaust air is already flowing away from the fuel cell stack, this heat is now transferred from the supply air to the exhaust air and transported further with the exhaust air, for example, released into the environment.The temperature of the compressed supply air is reduced in this way.

[0012] With this core concept of the present invention, it is now clear that a separate cooling option is no longer necessary, or at least the cooling functionality can be reduced. At least part of the required cooling of the supply air, in order to prevent overheated supply air entering the fuel cell stack, is now provided by the temperature difference to the exhaust air. In other words, the temperature difference between exhaust air and supply air can provide an internal cooling function, which allows the omission or reduction of the dimension of an additional cooling function. Separate cooling circuits can thus be designed independently of the supply air, thus offering significant advantages in terms of increased design freedom and reduced cooling requirements.Of course, there can be further advantages if, as explained later, the heat transferred internally is used for other purposes, so that an increase in efficiency is possible in addition to the temperature reduction.

[0013] A fuel cell system according to the invention is particularly advantageously used where cooling options are limited or, in particular, where there is a high dependence on weight. In particular, when the fuel cell system is intended to be used at low ambient pressures, for example, in high mountainous areas or in aircraft, increased compression effort is required, resulting in a correspondingly increased compression energy and an increased probability of overheating of the supply air. In such cases, a fuel cell system according to the invention offers decisive advantages, so that the fuel cell system is particularly designed for use in aviation, at high mountainous areas, or in other air pressure-sensitive situations.

[0014] Further advantages can be achieved if, in a fuel cell system according to the invention, the supply air / exhaust air heat exchanger is designed as a gas / gas heat exchanger for transferring heat from the gaseous supply air to the gaseous exhaust air. In other words, the supply air / exhaust air heat exchanger clearly differs from previously known heat transfer components when using active coolant circuits. If coolant circuits are used for the targeted temperature control and cooling of fuel cell systems, a liquid coolant is usually used. Due to the use of the liquid coolant, the heat transfer components for cooling the supply air must also be designed as gas / liquid heat transfer components. By switching to a pure gas / gas functionality in an embodiment according to the invention, additional design advantages are now achieved.Flowing two gases, especially in countercurrent, in a gas-to-gas heat exchanger is significantly easier to implement from a design perspective. Furthermore, the flow calculation and heat transfer can be optimized.

[0015] It can further be advantageous if, in a fuel cell system according to the invention, the exhaust air discharge section has a turbine device for at least partially recovering flow energy from the exhaust air, wherein the supply air-exhaust air heat exchanger for transferring the heat to the exhaust air is arranged upstream of the turbine device. At the outlet of the exhaust air from the fuel cell stack, this still contains, among other things, a certain amount of flow energy. This can, for example, also be the residual flow velocity which has been applied to the supply air by the compression device and the pressure differences. In order to recover at least part of this flow energy, it is known to provide turbine devices which allow the flow velocity of the exhaust air to be partially converted into rotational energy and thus into usable forms of energy.Because the supply air / exhaust air heat exchanger is now located upstream of this turbine device, the operating situation changes in that the exhaust air now reaches the turbine device at a higher inlet temperature than with known solutions. The increase in the inlet temperature changes the operating efficiency of the turbine device. Due to the increase in the inlet temperature of the exhaust air, the turbine device can be operated with increased turbine power, for example, with up to 10% higher absorption of the flow energy. In other words, simply increasing the temperature of the exhaust air means that, with otherwise identical operating parameters and ambient conditions, i.e., in particular, with identical flow velocity, a greater proportion of the flow energy can be recovered in the turbine device. The form of recovery is explained in more detail in the two following paragraphs.

[0016] It is advantageous if the turbine device and the compressor device can be operated independently of each other. In particular, the compressor device and the turbine device are not mounted on a common shaft, but separately.

[0017] Thus, it is advantageous if, in a fuel cell system according to the invention, the turbine device is at least partially connected to the compressor device in a torque-transmitting manner for at least partially transferring the flow energy absorbed by the turbine device from the exhaust air to the compressor device. In other words, the combination of turbine device and compressor device thus forms a type of turbocharger device, so that, for example, through a mechanical coupling and a torque-transmitting shaft contact, the absorbed torque from the turbine device can be delivered to the compressor device. By transferring the torque from the turbine device to the compressor device, the electrical energy required to operate the compressor device is reduced.Since, as already explained in the previous paragraph, heating the exhaust air already increases the amount of recoverable flow energy in the turbine device, this recovered energy can also be made available to the compressor device to a greater extent. In other words, this combination will result in a reduction in the total energy required by the compressor device during operation of the fuel cell system, thus further increasing operating efficiency.

[0018] It can also be advantageous if, in a fuel cell system according to the invention, the turbine device has an electric generator for at least partial use of the flow energy absorbed by the turbine device from the exhaust air to generate electrical power by means of the generator. This embodiment can be provided in addition to or alternatively to the mechanical coupling according to the preceding paragraph. Thus, an electric generator can be used to directly convert the absorbed and recyclable flow energy from the turbine device into electrical power. This electrical power can then, in turn, be made available to the compressor device, but also to other components.In comparison to the mechanical coupling according to the previous paragraph, the use of an electric generator may involve an electrical coupling with the compressor device or an electrical recovery option for the flow energy of the exhaust air.

[0019] Further advantages can be achieved if, in a fuel cell system according to the invention, the exhaust air discharge section upstream of the turbine device is designed without a water separator. A further design advantage can be achieved here through the inventive design. While in conventional fuel cell systems there is a risk of droplet formation in the exhaust air due to the increased air humidity, i.e., a partial condensation of the relative humidity, this risk can be minimized in the inventive manner. Droplets typically lead to increased abrasion and thus increased wear upon entering a turbine device.This increased wear is due to the fact that the turbine blades of the turbine device, rotating at high speed, come into mechanical contact with the water droplets, thus creating stresses that significantly increase wear. By using an inventive design with regard to the supply air-exhaust air heat exchanger, the temperature of the exhaust air is now increased before it enters the turbine device. Increasing the temperature essentially has two main advantages. Firstly, the increase in temperature reduces the relative humidity. By reducing the humidity and increasing the temperature, a driving force is created that stimulates any water droplets present to evaporate again.In other words, the likelihood of residual droplets in the exhaust air is significantly reduced, so that, depending on the operating situation and the design of the fuel cell system, the water separator, which otherwise protects the turbine assembly, can even be completely dispensed with. Eliminating the water separator component brings with it corresponding space, cost, and weight advantages.

[0020] It is also advantageous if, in a fuel cell system according to the invention, the exhaust air discharge section is designed free of a turbine device. This is an alternative solution to the previous paragraph. While the turbine solution generally brings about a greater increase in efficiency, the omission of a turbine can already enable the inventive advantages of increased efficiency even with reduced components. The mere return of a portion of the heat from the supply air to the exhaust air and the pure discharge of this exhaust air with the absorbed heat to the environment already brings about a significant part of the advantages in terms of reduced cooling effort for the supply air. Of course, the advantages of a fuel cell system according to the invention can be achieved in both cases.

[0021] It can also be advantageous if, in a fuel cell system according to the invention, the air supply section has a supply air bypass section, which forms a bypass for the supply air past the supply air-exhaust air heat exchanger. The air supply section and / or the supply air bypass section are equipped with at least one bypass valve device for controlled routing of the supply air through the supply air-exhaust air heat exchanger and / or the supply air bypass section. Depending on the operating situation, ambient temperature, flow velocity, or similar parameters, the cooling requirement for the supply air can vary. In very cold ambient conditions or during the start-up state of the fuel cell system, it is sometimes possible that no cooling of the supply air is required or desired at all. The provision of a supply air bypass section now leads to controllability of the heat transfer function.Thus, with the help of the bypass valve device, it is now possible to quantitatively and / or qualitatively control whether the supply air is routed entirely via the supply air / exhaust air heat exchanger or entirely via the supply air bypass section. If the bypass valve device is designed as a quantitatively switchable valve, a finer adjustment of the different partial quantities via the supply air / exhaust air heat exchanger and the supply air bypass section is also possible. In both cases, it is now possible to switch the heat transfer functionality to the exhaust air on and off, or even to quantitatively control it. This makes it possible to specifically adapt the heat transfer functionality and thus the cooling of the supply air to the respective operating situation and, in the case of a quantitatively controlling valve, even to exert a controlled influence on the temperature of the supply air.

[0022] It is also advantageous if, in a fuel cell system according to the invention, the exhaust air discharge section has an exhaust air bypass section, which forms a bypass for the supply air / exhaust air heat exchanger. At least one bypass valve device is arranged in the exhaust air discharge section and / or in the exhaust air bypass section for controlled routing of the exhaust air through the supply air / exhaust air heat exchanger and / or the exhaust air bypass section. This embodiment represents an alternative or additional bypass option, as described in the preceding paragraph. The basic functionality is essentially identical. The fact that a switch can now be made between a bypass and the supply air / exhaust air heat exchanger on the side of the exhaust air discharge section creates a similar level of control with regard to the heat transfer functionality.In this way, the temperature of the supply air can now be indirectly equipped with different heat absorption options through the exhaust air, so that the temperature of the compressed supply air can be controlled indirectly.

[0023] It is further advantageous if, in a fuel cell system according to the invention, the air supply section is designed without a cooling connection to a cooling circuit. As already explained, the internal cooling option can significantly reduce the additional cooling requirement for the supply air. In particular, if it is guaranteed for all application situations that the exhaust air has sufficient cooling functionality and cooling capacity due to the temperature gradients, an additional cooling connection to a cooling circuit can be completely dispensed with. By eliminating components, increased design freedom, reduced weight, reduced installation space, and reduced costs can be achieved. The present invention also relates to a control method for controlling a fuel cell system according to the invention. Such a control method comprises the following step:

[0024] - Leading the supply air downstream of the compressor device in the air supply section via a supply air-exhaust air heat exchanger for partial heat transfer from the supply air to the exhaust air.

[0025] A control method according to the invention thus brings with it the same advantages as have been explained in detail with reference to a fuel cell system according to the invention.

[0026] It may be advantageous if the following steps are additionally carried out in a control method according to the invention:

[0027] - Detecting an outlet temperature of the supply air at the outlet of the compressor device,

[0028] - Comparison of the recorded outlet temperature of the supply air with a target temperature for the supply air,

[0029] - Guide the supply air at least partially through the supply air-extract air heat exchanger if the outlet temperature exceeds the target temperature.

[0030] This controllability not only allows the cooling function to be provided by the exhaust air, but also ensures a qualitative or even quantitative switching option. By recording the outlet temperature, it is now possible to determine whether the supply air is too hot or sufficiently tempered. If a limit value, i.e. the set target temperature as a threshold, is exceeded, a targeted and controlled routing of the supply air via the supply air-exhaust air heat exchanger can now allow for targeted cooling of the supply air temperature. This can, of course, be achieved qualitatively and / or quantitatively and is ensured in particular by the bypass options already explained in the form of a supply air bypass section and / or an exhaust air bypass section.

[0031] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. They show schematically:

[0032] Fig. 1 shows an embodiment of a fuel cell system according to the invention,

[0033] Fig. 2 shows a further embodiment of a fuel cell system according to the invention,

[0034] Fig. 3 shows a further embodiment of a fuel cell system according to the invention,

[0035] Fig. 4 shows a further embodiment of a fuel cell system according to the invention and

[0036] Fig. 5 shows a further embodiment of a fuel cell system according to the invention.

[0037] Figure 1 schematically shows a very simple embodiment of a fuel cell system 100 according to the invention. A fuel cell stack 110 is shown schematically here. The individual fuel cells, arranged one above the other in a stack, are not shown in detail. The fuel cell stack 110 can be divided into an air side 120 and a fuel side 130. To carry out the electrochemical reaction to generate electricity in the fuel cell stack 110, supply air ZL is supplied to the air side 120 via an air supply section 122. On the fuel side 130, fuel BS is supplied via the fuel supply section 132. Within the fuel cell stack 110, fuel BS and supply air ZL are chemically reacted with one another, resulting in the desired generation of electrical current.

[0038] Figure 1 shows that the supply air ZL, for example, can be drawn in from the environment via a compressor device 140 and compressed. At the outlet downstream of the compressor device 140, the supply air ZL therefore has a significantly increased pressure and, due to the law of ideal gases, also an increased temperature. To ensure that the heated supply air ZL does not exceed a predefined upper limit and, in particular, does not reach the fuel cell stack 110 in an overheated and thus potentially damaging state, a cooling option is now provided downstream of the compressor device 140. This cooling option is provided here by the supply air-exhaust air heat exchanger 150. The supply air ZL will flow through this supply air-exhaust air heat exchanger 150 in a compressed and thus overheated form on the hot side.On the cold side, as part of the exhaust air discharge section 124, the exhaust air AL is discharged from the fuel cell stack 110 and there from the air side 120. Because the discharge from the fuel cell stack 110 creates a temperature gradient between the superheated supply air ZL and the significantly cooler exhaust air AL, a heat transfer from the supply air ZL to the exhaust air AL can be generated via the heat-contacting connection within the supply air-exhaust air heat exchanger 150. This heat transfer leads to the exhaust air AL being partially heated and the supply air ZL being cooled accordingly. Downstream of the supply air-exhaust air heat exchanger 150, the temperature of the supply air ZL, reduced accordingly by the heat transfer, now enters the fuel cell stack 110, so that the desired and required cooling functionality can be ensured as internal cooling by the existing media flows.

[0039] Figure 2 further develops the embodiment of Figure 1. Here, to further increase efficiency, a turbine device 160 is arranged in the exhaust air discharge section 124 downstream of the supply air-exhaust air heat exchanger 150. This turbine device 160 serves to recover at least a portion of the flow energy from the exhaust air AL. For this purpose, the flow of the exhaust air AL is directed over the turbine device 160 so that it can be set in rotation to recover the flow energy. In the embodiment of Figure 2, this is now designed in torque-transmitting contact with the compressor device 140 via a mechanical coupling 164. In other words, a portion of the torque recovered from the flow energy of the exhaust air AL can be transferred to the compressor device, so that the required electrical compressor power can be significantly reduced.Because the supply air-exhaust air heat exchanger 150 now serves to heat exhaust air AL upstream of the turbine device 160, the inlet temperature of the exhaust air AL at the turbine device 160 is increased. By increasing the inlet temperature compared to known solutions, the turbine power is correspondingly increased, so that simply by increasing the inlet temperature of the exhaust air AL, a further increase in recovery and thus an additional efficiency optimization for the fuel cell system 100 can be achieved. Figure 3 is based on the embodiment of Figure 2. However, here the turbine device 160 is coupled to an electrical generator 162. The recovered flow energy from the preheated exhaust air AL is thus converted into electrical current in the generator 162. This electrical current can be temporarily stored or fed to other components.Here, the dashed line indicates, in particular, a return of the recovered electrical power to the compressor device 140. This means that, even with increased design freedom in different arrangement positions between the turbine device 160 and the compressor device 140, the use of the recovered energy is now possible by supplementing the power supply in the compressor device 140.

[0040] Figure 4 shows one possibility for controlling the cooling functionality in the form of internal cooling of the fuel cell system 100. This is ensured here by providing an air supply bypass section 126 in the air supply section 122. With the aid of a bypass valve device 170, which here has two separate valves, a controlled, quantitative and / or qualitative distribution of the supply air ZL between the supply air / exhaust air heat exchanger 150 and the supply air bypass section 126 can take place. In other words, it becomes possible to either qualitatively direct the entire flow through the supply air / exhaust air heat exchanger 150 and thus switch it on. Alternatively, the entire flow of supply air can be directed through the supply air bypass section 126, so that this cooling functionality is completely switched off.If the two valves of the bypass valve device can be controlled quantitatively, a gradual division of the individual flow rates can be carried out accordingly, so that a gradual adjustment of the flow rates will lead to a controllability of the temperature reduction for the supply air at the supply air-exhaust air heat exchanger 150.

[0041] Figure 5 shows a further controllability similar to the embodiment in Figure 4. However, here the control of the temperature reduction for the supply air ZL is ensured indirectly. For this purpose, an exhaust air bypass section 136 is integrated into the exhaust air discharge section 124. For the sake of simplicity, the bypass valve device 170 is also equipped with only a single valve, so that the bypass section can essentially only be opened and closed. This reduces the design effort and the number of components, but also reduces the controllability with regard to the desired control over the supply air temperature.

[0042] The above explanation of the embodiments describes the present invention exclusively by way of examples.

[0043] List of reference symbols

[0044] 100 fuel cell system

[0045] 110 fuel cell stacks

[0046] 120 airside

[0047] 122 Air supply section

[0048] 124 Exhaust air discharge section

[0049] 126 Supply air bypass section

[0050] 130 Fuel side

[0051] 132 Fuel supply section

[0052] 134 Exhaust gas discharge section

[0053] 136 Exhaust air bypass section

[0054] 140 Compressor device

[0055] 150 supply air-exhaust air heat exchangers

[0056] 160 turbine device

[0057] 162 Generator

[0058] 164 mechanical coupling

[0059] 170 Bypass valve device

[0060] ZL supply air

[0061] AL exhaust air

[0062] BS Fuel

[0063] AG Exhaust

Claims

Patent claims 1. A fuel cell system (100) for generating electrical power, comprising at least one fuel cell stack (110), wherein the fuel cell stack (110) has an air side (120) and a fuel side (130), and the air side (120) has an air supply section (122) for supplying supply air (ZL) to the air side (120) and an exhaust air discharge section (124) for discharging exhaust air (AL) from the air side (120), wherein the fuel side (130) further has a fuel supply section (132) for supplying fuel (BS) to the fuel side (130) and an exhaust gas discharge section (134) for discharging exhaust gas (AG) from the fuel side (130), characterized in that a compressor device (140) is arranged in the air supply section (122) for compressing the supply air (ZL),wherein downstream of this compressor device (140) a supply air-exhaust air heat exchanger (150) is arranged for heat transfer from the supply air (ZL) to the exhaust air (AL)., 2. Fuel cell system (100) according to claim 1, characterized in that the supply air-exhaust air heat exchanger (150) is designed as a gas-gas heat exchanger for transferring heat from a gaseous supply air (ZL) to a gaseous exhaust air (AL).

3. Fuel cell system (100) according to one of the preceding claims, characterized in that the exhaust air discharge section (134) has a turbine device (160) for at least partial recovery of flow energy from the exhaust air (AL), wherein the supply air-exhaust air heat exchanger (150) for transferring the heat to the exhaust air (AL) is arranged upstream of the turbine device (160).

4. Fuel cell system (100) according to claim 3, characterized in that the turbine device (160) and the compressor device (140) can be operated independently of one another.

5. Fuel cell system (100) according to claim 3, characterized in that the turbine device (160) is at least partially connected to the compressor device (140) in a torque-transmitting manner for at least partial transfer of the flow energy absorbed by the turbine device (160) from the exhaust air (AL) to the compressor device (140).

6. Fuel cell system (100) according to one of claims 3 to 5, characterized in that the turbine device (160) has an electric generator (162) for at least partial use of the flow energy absorbed by the turbine device (160) from the exhaust air (AL) for generating electric current by means of the generator (162).

7. Fuel cell system (100) according to one of claims 3 to 6, characterized in that the exhaust air discharge section (134) upstream of the turbine device (160) is designed free of a water separator.

8. Fuel cell system (100) according to one of claims 1 or 2, characterized in that the exhaust air discharge section (134) is designed free of a turbine device (160).

9. Fuel cell system (100) according to one of the preceding claims, characterized in that the air supply section (122) has a supply air bypass section (126) which forms a bypass for the supply air (ZL) past the supply air-exhaust air heat exchanger (150), wherein in the air supply section (122) and / or in the supply air bypass section (126) at least one bypass valve device (170) is arranged for a controlled guidance of the supply air (ZL) through the supply air-exhaust air heat exchanger (150) and / or the supply air bypass section (126).

10. Fuel cell system (100) according to one of the preceding claims, characterized in that the exhaust air discharge section (134) has an exhaust air bypass section (136) which forms a bypass for the exhaust air (AL) past the supply air-exhaust air heat exchanger (150), wherein in the exhaust air discharge section (134) and / or in the exhaust air bypass section (136) at least one bypass valve device (170) is arranged for a controlled guidance of the exhaust air (AL) through the supply air-exhaust air heat exchanger (150) and / or the exhaust air bypass section (136).

11. Fuel cell system (100) according to one of the preceding claims, characterized in that the air supply section (122) is designed free of a cooling connection to a cooling circuit.

12. Control method for controlling a fuel cell system (100) having the features of one of claims 1 to 11, characterized by the following step: - guiding the supply air (ZL) downstream of the compressor device (140) in the air supply section (122) via a supply air-exhaust air heat exchanger (150) for partial heat transfer from the supply air (ZL) to the exhaust air (AL).

13. Control method according to claim 12, characterized in that the following steps are additionally carried out: - detecting an outlet temperature of the supply air (ZL) at the outlet of the compressor device (140), - Comparison of the recorded outlet temperature of the supply air (ZL) with a target temperature for the supply air (ZL), - guiding the supply air (ZL) at least partially via the supply air-exhaust air heat exchanger (150) if the outlet temperature exceeds the target temperature.

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