Fuel cell device and method for operating a fuel cell device

Abstract

The invention is based on a fuel cell device (10a; 10b), in particular an SOFC fuel cell device, with at least one fuel cell unit (12a; 12b), with a fluid supply unit (14a; 14b) which is provided for supplying at least one oxygen-containing fluid (16a; 16b) to the fuel cell unit (12a; 12b), and with at least one functional unit (18a; 18b), in particular different from a heating unit, which is functionally connected to the fuel cell unit (12a; 12b). It is proposed that the fuel cell device (10a; 10b) has a heat recovery unit (20a; 20b) which is thermally coupled to the fluid supply unit (14a; 14b) and is intended to use waste heat from the functional unit (18a; 18b) to heat the oxygen-containing fluid (16a; 16b).

Description

State of the art

[0001] A fuel cell device having at least one fuel cell unit, having a fluid supply unit which is provided for supplying at least one oxygen-containing fluid to the fuel cell unit, and having at least one functional unit which is functionally connected to the fuel cell unit has already been proposed. Disclosure of the invention

[0002] The invention is based on a fuel cell device, in particular an SOFC fuel cell device, with at least one fuel cell unit, with a fluid supply unit which is provided for supplying at least one oxygen-containing fluid to the fuel cell unit, and with at least one functional unit, in particular different from a heating unit, which is functionally connected to the fuel cell unit.

[0003] It is proposed that the fuel cell device has a heat recovery unit thermally coupled to the fluid supply unit, which is intended to use waste heat of the functional unit to heat the oxygen-containing fluid.

[0004] The inventive design of the fuel cell device allows the oxygen-containing fluid to be heated to a desired temperature in a particularly energy-efficient manner. Advantageously, the fuel cell device can be operated in a particularly wide range of temperature environments. Particularly energy-efficient operation of the fuel cell device can be achieved in a cold environment of down to -25°C. Advantageously, a heating unit for heating the oxygen-containing fluid can be dispensed with and / or the heating requirement for a heating unit for heating the oxygen-containing fluid can be kept particularly low. A particularly energy-efficient fuel cell device can be provided.

[0005] The fuel cell device is preferably designed as a solid oxide fuel cell, abbreviated in particular to SOFC (Solid Oxide Fuel Cell). It is conceivable for the fuel cell device to have a plurality of fuel cell units connected in parallel, in particular with regard to the conduction of a fuel and / or the oxygen-containing fluid. The fuel cell unit has at least one, preferably a plurality of, fuel cells. Preferably, the at least one fuel cell unit is configured to generate electrical energy, preferably through cold combustion, in particular oxidation, of the fuel in a redox reaction with oxygen from the oxygen-containing fluid. “Configured” should be understood in particular to mean specially programmed, designed and / or equipped.The fact that an object is configured for a specific function should be understood in particular to mean that the object fulfils and / or executes this specific function in at least one application and / or operating state.

[0006] The fluid supply unit is preferably configured to supply the oxygen-containing fluid to the fuel cell unit, in particular continuously. The fluid supply unit preferably comprises a compressor. The compressor of the fluid supply unit is provided, in particular, to generate a flow of the oxygen-containing fluid to supply the fuel cell unit with the oxygen-containing fluid. The fluid supply unit preferably comprises at least one fluid guide element, which is designed, for example, as a pipe, a shaft, or the like. The compressor is preferably fluidically connected to the fuel cell unit via the fluid supply unit, in particular the at least one fluid guide element. "Provided" is to be understood as specifically configured, specifically designed, and / or specifically equipped.The fact that an object is intended for a specific function should be understood to mean that the object fulfils and / or executes this specific function in at least one application and / or operating state.

[0007] The fuel cell device preferably has at least one fuel supply unit. The fuel supply unit is preferably designed to supply the fuel to the fuel cell unit, in particular continuously. The fuel supply unit preferably has a compressor, in particular a gas booster. The compressor of the fuel supply unit is preferably designed to generate a fuel pressure, which is in particular designed to move the fuel to the fuel cell unit.

[0008] A “functional unit” is to be understood here in particular as a unit which assumes a function in the generation of electrical energy by the fuel cell device. The functional unit is preferably designed such that operation of the functional unit generates waste heat. The functional unit preferably has a motor, electrical components and / or electronic components, which preferably generate waste heat during operation. The functional unit can be designed, for example, as a compressor, preferably as the compressor of the fuel supply unit, as an electrical unit or the like. The functional unit is designed, in particular, differently from a heating unit. The fact that the functional unit is designed differently from a heating unit is to be understood in particular as meaning that the primary function of the functional unit is different from heat generation.

[0009] It is also conceivable for the heat recovery unit to be thermally coupled to a plurality of functional units of the fuel cell device, in particular to utilize waste heat from the functional units to heat the oxygen-containing fluid. The heat recovery unit is, in particular, configured to supply the waste heat from the functional unit to the oxygen-containing fluid. The heat recovery unit is, in particular, thermally coupled to the fuel cell unit. The fluid supply unit, in particular the oxygen-containing fluid, is preferably thermally coupled to the functional unit via the heat recovery unit. The heat recovery unit can be configured for heat transfer, in particular based on thermal conduction, between the fluid supply unit and the functional unit.The heat recovery unit can, in particular, be designed for heat transfer based on heat conduction between the functional unit and the fluid supply unit. Alternatively or additionally, it is conceivable that the heat recovery unit is designed for heat transfer based on heat transport between the fluid supply unit, in particular the oxygen-containing fluid, and the functional unit.

[0010] The term “functionally connected” should be understood to mean, in particular, connected to one another to achieve a desired function, here in particular to generate electrical energy, where “functionally connected” can be, for example, electrically connected, fluidically connected, thermally coupled, data-connected, a combination thereof or the like.

[0011] It is further proposed that the functional unit be designed as a compressor, in particular as the compressor of the fuel supply unit. Waste heat from the compressor can advantageously be used to heat the oxygen-containing fluid. This allows particularly energy-efficient heating of the oxygen-containing fluid. Advantageously, operation of the fuel cell device under optimal conditions, in particular with regard to the temperature of the oxygen-containing fluid, can be supported in a particularly energy-efficient manner.

[0012] It is further proposed that the compressor, in particular the compressor of the fuel supply unit, comprise a motor, wherein the heat recovery unit is provided to utilize waste heat from the compressor motor to heat the oxygen-containing fluid. Waste heat from the compressor motor can advantageously be utilized to heat the oxygen-containing fluid. A particularly energy-efficient heating of the oxygen-containing fluid can be achieved. Advantageously, operation of the fuel cell device under optimal conditions, in particular with regard to the temperature of the oxygen-containing fluid, can be supported in a particularly energy-efficient manner. The compressor of the fuel supply unit comprises, in particular, a fan. The motor is provided, in particular, to drive the fan.

[0013] Furthermore, it is proposed, particularly in an alternative embodiment, that the functional unit be designed as an electrical unit for the fuel cell unit. Waste heat from the electrical unit can advantageously be used to heat the oxygen-containing fluid. A particularly energy-efficient heating of the oxygen-containing fluid can be achieved. Advantageously, operation of the fuel cell device under optimal conditions, particularly with regard to the temperature of the oxygen-containing fluid, can be supported in a particularly energy-efficient manner. The electrical unit is preferably provided to decouple an electrical current generated by the fuel cell unit, particularly from the fuel cell device.The electrical unit comprises, for example, an inverter arranged on the fuel cell unit, an electrical energy buffer for compensating load fluctuations, a power supply for electrical components of the fuel cell device, and / or the like. Particularly preferably, the heat recovery unit is thermally coupled to the inverter of the electrical unit.

[0014] It is further proposed that the heat recovery unit comprise a heat exchanger. Advantageously, the waste heat can be used particularly efficiently to heat the oxygen-containing fluid. A particularly energy-saving fuel cell device can be provided. The heat recovery unit, in particular the heat exchanger, preferably comprises a waste heat conduction unit which is thermally coupled to the functional unit and the fluid supply unit. The heat exchanger comprises a working medium which is guided in the waste heat conduction unit. The waste heat conduction unit preferably comprises at least one waste heat conduction element, for example a pipe or the like, preferably for guiding the working medium. The working medium is designed, for example, as water, as thermal oil, as brine, as air or the like.Preferably, the waste heat conduction unit is fluidically separated from the fluid supply unit, but thermally coupled for heat transfer.

[0015] It is also proposed that the heat exchanger be designed as a tube-in-tube arrangement. This advantageously enables a particularly space-saving and / or efficient heat exchange. At least part of the fluid supply unit, in particular at least part of the fluid guide element, is preferably arranged within the waste heat conduction unit, preferably the waste heat conduction element of the waste heat conduction unit. At least part of the fluid supply unit, in particular part of the fluid guide element, is surrounded by the waste heat conduction unit, preferably the waste heat conduction element.

[0016] It is further proposed that the fuel cell device have a control and / or regulating unit which is provided for controlling the heat recovery unit to heat the oxygen-containing fluid to at least 5°C. Particularly precise heating of the oxygen-containing fluid can advantageously be achieved. Particularly efficient operation of the fuel cell device can be enabled. The control or regulating unit comprises, in particular, at least one processor and one memory element as well as an operating program stored on the memory element. The memory element is preferably designed as a digital storage medium, for example as a hard disk or the like. It is conceivable for the heat recovery unit to have a delivery unit, for example a pump and / or a blower, and / or a valve unit. The delivery unit is preferably provided for generating a fluid flow of the working medium.By means of the valve unit, for example, a fluid flow through the waste heat conduction unit, preferably the waste heat conduction element, can be blocked and / or released. It is conceivable for the fuel cell device to have a sensor unit, preferably at least one temperature sensor, for detecting a temperature parameter relating to the oxygen-containing fluid. The temperature parameter can, for example, comprise a temperature of an environment of the fuel cell device and / or a temperature of the oxygen-containing fluid. The oxygen-containing fluid is in particular gaseous, preferably air, preferably air from the environment of the fuel cell device. The fluid supply unit is in particular provided to draw in air from the environment and preferably supply it to the fuel cell unit.It is conceivable that the control and / or regulating unit is designed to control the heat recovery unit depending on the temperature parameter.

[0017] Furthermore, the invention is based on a method for operating a fuel cell device, in particular the one already mentioned. It is proposed that an oxygen-containing fluid to be supplied to at least one fuel cell unit, in particular the one already mentioned, of the fuel cell device, in particular the one already mentioned, is heated by waste heat from a functional unit of the fuel cell device that is functionally connected to the fuel cell unit, in particular the one already mentioned. By means of the method according to the invention, the oxygen-containing fluid can be heated to a required temperature in a particularly energy-efficient manner. Advantageously, the fuel cell device can be operated in a particularly wide variety of temperature environments. Particularly energy-efficient operation of the fuel cell device can be achieved in a particularly cold environment of down to -25 °C.It is advantageous to dispense with a heating unit for heating the oxygen-containing fluid.

[0018] It is also proposed that the oxygen-containing fluid be heated at least partially to at least 5 °C by the waste heat. This can enable particularly efficient operation of the fuel cell device.

[0019] The fuel cell device according to the invention and / or the method according to the invention are not intended to be limited to the application and embodiment described above. In particular, the fuel cell device according to the invention and / or the method according to the invention may have a number of individual elements, components, units, and method steps that differs from the number stated herein to fulfill a function described herein. Furthermore, in the value ranges specified in this disclosure, values ​​within the stated limits are also to be considered disclosed and can be used arbitrarily. drawing

[0020] Further advantages will become apparent from the following description of the drawings. The drawings illustrate two exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0021] They show: Fig. 1 a fuel cell device according to the invention in a schematic representation, Fig. 2 a part of a heat recovery unit of the fuel cell device in a perspective view, Fig. 3 a schematic sequence of a method according to the invention for operating the fuel cell device and Fig. 4 a schematic representation of a part of a fuel cell device according to the invention in an alternative embodiment. Description of the embodiments

[0022] Fig. 1 shows a fuel cell device 10a. The fuel cell device 10a is embodied here, by way of example, as an SOFC fuel cell device.

[0023] The fuel cell device 10a here, for example, has five fuel cell units 12a. Alternatively, it is conceivable for the fuel cell device 10a to have fewer or more than five fuel cell units 12a. The fuel cell units 12a are connected in parallel with respect to the conduction of a fuel and / or an oxygen-containing fluid 16a. The fuel cell units 12a are configured to generate electrical energy, preferably through cold combustion, in particular oxidation, of the fuel in a redox reaction with oxygen from the oxygen-containing fluid 16a.

[0024] The fuel cell units 12a are provided for an electrochemical conversion of the fuel while supplying the oxygen-containing fluid 16a to an exhaust gas.

[0025] The fuel cell device 10a has a fluid supply unit 14a. The fluid supply unit 14a is provided for supplying the oxygen-containing fluid 16a to the fuel cell units 12a. The fluid supply unit 14a is provided for drawing in air from the environment and supplying it to the fuel cell units 12a. The fluid supply unit 14a has a compressor (not shown here). The compressor of the fluid supply unit 14a is provided for generating a flow of the oxygen-containing fluid 16a to supply the fuel cell units 12a with the oxygen-containing fluid 16a. The fluid supply unit 14a has fluid guide elements 34a, which are designed, for example, as tubes or the like. The compressor of the fluid supply unit 14a is fluidly connected to the fuel cell units 12a via the fluid guide elements 34a.

[0026] The fuel cell device 10a has a plurality of functional units 18a, in particular different from a heating unit, which are each functionally connected to one of the fuel cell units 12a. The functional units 18a are embodied here, for example, as electrical units 24a for the fuel cell units 12a.

[0027] The electrical units 24a are provided for extracting an electrical current generated by the respective fuel cell unit 12a, in particular from the fuel cell device 10a. The electrical units 24a each comprise, for example, an inverter arranged on the respective fuel cell unit 12a, an electrical energy buffer for compensating load fluctuations, a power supply for electrical components of the fuel cell device 10a, and / or the like (not shown here).

[0028] The fuel cell device 10a has a fuel supply unit (not shown here). The fuel supply unit is designed to supply the fuel to the fuel cell units 12a, in particular continuously. The fuel supply unit has a compressor, in particular a gas booster. The compressor of the fuel supply unit is designed to generate a fuel pressure, which is designed in particular to move the fuel to the fuel cell units 12a.

[0029] The fuel cell device 10a has an exhaust gas guide unit 36a. The exhaust gas guide unit 36a has exhaust gas guide elements 38a. The exhaust gas guide unit 36a is provided to discharge the exhaust gas from the fuel cell units 12a, in particular from the fuel cell device 10a, preferably via the exhaust gas guide elements 38a.

[0030] The fuel cell device 10a here has, for example, a heat exchanger 40a thermally coupled to the exhaust gas guide unit 36a. The heat exchanger 40a is provided here, for example, for heating water.

[0031] The fuel cell device 10a has a heat recovery unit 20a thermally coupled to the fluid supply unit 14a. The heat recovery unit 20a is designed to utilize waste heat from the functional units 18a to heat the oxygen-containing fluid 16a.

[0032] The heat recovery unit 20a has a waste heat conduction unit 66a. The waste heat conduction unit 66a is thermally coupled to the functional units 18a and the fluid supply unit 14a. The waste heat conduction unit 66a has waste heat conduction elements 42a. The waste heat conduction elements 42a are provided for conducting waste heat from the functional units 18a to the fluid supply unit 14a. The functional units 18a are thermally coupled to the fluid supply unit 14a via the waste heat conduction elements 42a. The waste heat conduction elements 42a are designed as tubes. The heat recovery unit 20a has a flap 44a. The flap 44a is arranged between the functional units 18a and the fluid supply unit 14a, in particular on a waste heat conduction element 42a, which is preferably common to the functional units 18a.The flap 44a is provided to selectively block or release a heat flow from the functional units 18a to the fluid supply unit 14a.

[0033] The heat recovery unit 20a has an additional heat dissipation outlet 46a. The additional heat dissipation outlet 46a is provided for dissipating waste heat from the functional units 18a to an environment. The heat recovery unit 20a has, for example, a further flap 48a. The further flap 48a is arranged between the functional units 18a and the additional heat dissipation outlet 46a, in particular on a waste heat conduction element 42a, preferably common to the functional units 18a. The further flap 48a is provided to selectively block or allow a heat flow from the functional units 18a to the additional heat dissipation outlet 46a.

[0034] The fluid supply unit 14a has a filter 50a for filtering the oxygen-containing fluid 16a drawn in from the environment. It is conceivable for the fluid supply unit 14a to have a heating unit 52a, in particular an electric heater, for heating the oxygen-containing fluid 16a. The heating unit 52a is fluidically connected downstream of the filter 50a. The heat recovery unit 20a has a heat exchanger 26a. The filter 50a is fluidically connected downstream of the heat exchanger 26a, in particular, is interposed between the heat exchanger 26a and the heating unit 52a. Alternatively, it is conceivable for the fluid supply unit 14a to be designed without a heating unit 52a.

[0035] The fuel cell device 10a has an electrical unit air supply unit 54a for supplying air, preferably from the environment, to the electrical units 24a. The electrical unit air supply unit 54a has air supply elements 56a, which are designed as tubes or the like, for supplying air to the electrical units 24a. The electrical unit air supply unit 54a has a filter 58a for the air to be supplied to the electrical units 24a. The electrical unit air supply unit 54a has a heating unit 60a, in particular to advantageously enable a minimum temperature of a cooling air, preferably at low outside temperatures, for reliable operation of the fuel cell device 10a. The fuel cell device 10a has a housing heating unit 62a for heating a housing 64a of the fuel cell device 10a.

[0036] The heat recovery unit 20a is configured to supply the waste heat from the functional units 18a to the oxygen-containing fluid 16a. The heat recovery unit 20a is thermally coupled to the fuel cell units 12a. The fluid supply unit 14a, in particular the oxygen-containing fluid 16a, is thermally coupled to the functional units 18a via the heat recovery unit 20a.

[0037] The heat exchanger 26a has a working medium 84a, which is guided in the waste heat conduction unit 66a. The working medium 84a is configured, for example, as water, thermal oil, brine, air, or the like. The waste heat conduction unit 66a is fluidically separated from the fluid supply unit 14a, but is thermally coupled for heat transfer.

[0038] The heat exchanger 26a is designed as a tube-in-tube connection (cf. Fig. 2). At least a part of the fluid supply unit 14a, in particular at least a part of one of the fluid guide elements 34a, is arranged within the waste heat conduction unit 66a, preferably one of the waste heat conduction elements 42a.

[0039] The fuel cell device 10a has a control and / or regulating unit 28a. The control and / or regulating unit 28a is provided to control the heat recovery unit 20a to heat the oxygen-containing fluid 16a to at least 5°C.

[0040] The control or regulating unit 28a comprises at least one processor and one memory element, as well as an operating program stored on the memory element (not shown here). The memory element is designed as a digital storage medium, for example, as a hard disk or the like. It is conceivable for the heat recovery unit 20a to have a conveying unit, for example, a fan and / or a pump, and / or a valve unit, for example, the flap 44a and / or the further flap 48a. The conveying unit is provided for generating a fluid flow of the working medium 84a. By means of the valve unit, in particular the flap 44a and / or the further flap 48a, a fluid flow through the waste heat conduction unit 66a, preferably the waste heat conduction elements 42a, can be blocked and / or released, for example.

[0041] It is conceivable that the fuel cell device 10a has a sensor unit, preferably at least one temperature sensor, for detecting a temperature parameter relating to the oxygen-containing fluid 16a. The temperature parameter can, for example, be a temperature of an environment of the fuel cell device 10a and / or a temperature of the oxygen-containing fluid 16a. The oxygen-containing fluid 16a is gaseous, preferably air, preferably air from the environment of the fuel cell device 10a. It is conceivable that the control and / or regulating unit 28a is provided to control the heat recovery unit 20a, in particular the flap 44a and / or the further flap 48a, and / or the heating unit 52a, depending on the temperature parameter.

[0042] Fig. 3 shows a schematic sequence of a method for operating the fuel cell device 10a. In one method step, in particular in a supply step 30a, the oxygen-containing fluid 16a is supplied to the fuel cell units 12a, in particular by means of the fluid supply unit 14a. The oxygen-containing fluid 16a to be supplied to the fuel cell units 16a is heated by waste heat from the functional units 18a functionally connected to the fuel cell units 12a. The oxygen-containing fluid 16a is at least partially heated to at least 5°C by the waste heat. Additionally, it is conceivable that the oxygen-containing fluid 16a, in particular in the supply step 30a, is heated by the heating unit 52a. The heating of the oxygen-containing fluid 16a in the supply step 30a is controlled by the control and / or regulating unit 28a.

[0043] In a further process step, particularly in a power generation step 32a, electrical energy is generated from the fuel and the oxygen-containing fluid 16a. The exhaust gas generated in the power generation step 32a is discharged via the exhaust gas guide unit 36a.

[0044] In Fig. 4 shows a further embodiment of the invention. The following descriptions and the drawings are essentially limited to the differences between the embodiments, whereby with regard to components with the same designation, in particular with regard to components with the same reference numerals, reference is also made to the drawings and / or the description of the other embodiments, in particular to the Fig. 1 to 3. To distinguish the embodiments, the letter a is added to the reference numerals of the embodiment in the Fig. 1 to 3. In the example of the Fig. 4, the letter a is replaced by the letter b.

[0045] Fig. 4 shows part of a fuel cell device 10b. The fuel cell device 10b has a functional unit 18b. The functional unit 18b is designed as a compressor 22b. The fuel cell device 10b has a heat recovery unit 20b. The heat recovery unit 20b is thermally coupled to a fluid supply unit 14b of the fuel cell device 10b. The fluid supply unit 14b is provided for supplying an oxygen-containing fluid 16b to at least one fuel cell unit 12b of the fuel cell device 10b.

[0046] The compressor 22b is configured to generate a fuel pressure, which is particularly configured to move a fuel 68b to the at least one fuel cell unit 12b. The compressor 22b is preferably arranged outside a housing (not shown in detail here) of the fuel cell device 10b, in which the fuel cell units 12b or a plurality of fuel cell units 12b of the fuel cell device 10b are arranged.

[0047] The compressor 22b has a circulation regulator 76b. The compressor 22b has a motor (not shown here). The heat recovery unit 20b is designed to utilize waste heat from the motor to heat the oxygen-containing fluid 16b.

[0048] The fuel cell device 10b has a vacuum pressure switch 70b. The vacuum pressure switch 70b is fluidically connected upstream of the compressor 22b. The fuel cell device 10b has an overpressure pressure switch 74b. The overpressure pressure switch 74b is fluidically connected downstream of the compressor 22b. The fuel cell device 10b has a temperature switch 72b. The overpressure pressure switch 74b and the temperature switch 72b preferably form a safety device for the compressor 22b. The temperature switch 72b monitors the temperature of the fuel 68b, in particular since the temperature of the fuel 68b can increase due to compression by the compressor 22b. The temperature switch 72b is preferably provided to generate a signal, in particular an emergency shutdown signal, when a safety-critical temperature is reached in order to protect the fuel cell device 10b from damage.The vacuum pressure switch 70b is provided to prevent a vacuum limit from being exceeded—i.e., an excessive vacuum—in the event of a particularly unintentional interruption of the supply of fuel 68b to the compressor 22b, preferably while maintaining a power supply to the compressor 22b. The overpressure pressure switch 74b is preferably provided to trigger an emergency shutdown of the compressor 22b if the compressed fuel 68b is not removed and the pressure continues to rise. Preferably, the vacuum pressure switch 70b, the temperature switch 72b, and / or the overpressure pressure switch 74b are provided for an emergency shutdown of the compressor 22b should a respective threshold value be exceeded / undershot.

[0049] The fuel cell device 10b has a pressure sensor 78b for a frequency converter of the fuel cell device 10b. The pressure sensor 78b is fluidically connected downstream of the compressor 22b. Fig. 4 shows an electrical connection 82b for the compressor 22b. The compressor 22b also has a temperature monitoring unit 80b, for example, with a temperature sensor, for monitoring the temperature inside the compressor 22b. The compressor 22b of the fuel supply unit has a fan (not shown here). The motor is provided to drive the fan.

Claims

[1] Fuel cell device (10a; 10b), in particular SOFC fuel cell device, with at least one fuel cell unit (12a; 12b), with a fluid supply unit (14a; 14b) which is intended to supply at least one oxygen-containing fluid (16a; 16b) to the fuel cell unit (12a; 12b), and with at least one functional unit (18a; 18b), in particular different from a heating unit, which is functionally connected to the fuel cell unit (12a; 12b), characterized by a heat recovery unit (20a; 20b) thermally coupled to the fluid supply unit (14a; 14b), which is intended to use waste heat from the functional unit (18a; 18b) to heat the oxygen-containing fluid (16a; 16b). [2] Fuel cell device (10b) according to claim 1, characterized by that the functional unit (18b) is designed as a compressor (22b). [3] Fuel cell device (10b) according to claim 2, characterized bythat the compressor (22b) has a motor, wherein the heat recovery unit (20b) is provided to use waste heat from the motor of the compressor (22b) to heat the oxygen-containing fluid (16b). [4] Fuel cell device (10a) according to claim 1 or 2, characterized by that the functional unit (18a) is designed as an electrical unit (24a) for the fuel cell unit (12a). [5] Fuel cell device (10a; 10b) according to one of the preceding claims, characterized by that the heat recovery unit (20a; 20b) has a heat exchanger (26a). [6] Fuel cell device (10a) according to claim 5, characterized by that the heat exchanger (26a) is designed as a tube-in-tube connection. [7] Fuel cell device (10a; 10b) according to one of the preceding claims, characterized bya control and / or regulating unit (28a) which is provided to control the heat recovery unit (20a; 20b) to heat the oxygen-containing fluid (16a; 16b) to at least 5 °C. [8] Method for operating a fuel cell device (10a; 10b), in particular according to one of the preceding claims, characterized by that an oxygen-containing fluid (16a; 16b) to be supplied to at least one fuel cell unit (12a; 12b) of the fuel cell device (10a; 10b) is heated by waste heat from a functional unit (18a; 18b) of the fuel cell device (10a; 10b) that is functionally connected to the fuel cell unit (12a; 12b). [9] Method according to claim 8, characterized by that the oxygen-containing fluid (16a; 16b) is at least partially heated to at least 5 °C by the waste heat.

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