Fuel cell system

Abstract

The invention relates to a method for operating a fuel cell system comprising a fuel cell (2), a cooler (3) for providing cooling fluid (30) with which the fuel cell (2) is cooled, and an exhaust line (4) leading from the fuel cell (2). It is proposed that water (5) be separated from an exhaust gas (40) flowing through the exhaust line (4), and that the separated water (5) be fed to a cooling body (31) of the cooler (3).

Description

The present invention relates to a method for operating a fuel cell system having the features of claim 1 and to a fuel cell system having the features of claim 6.A fuel cell converts the chemical reaction energy of a continuously supplied fuel, e.g., hydrogen, and an oxidizing agent, e.g., oxygen, into electrical energy. Fuel cells are used, for example, in fuel cell vehicles in order to convert the generated electrical energy directly into movement by means of an electric drive or temporarily buffer it in a drive battery. Apart from hydrogen, fuel cells can also use other fuels, in particular methanol, butane or natural gas.The exhaust gas which is produced during the power generation reaction in a hydrogen-oxygen fuel cell and is discharged in particular from the cathode of the fuel cell contains water (usually in the form of water vapor and water droplets) and has an exhaust gas temperature in the range of 80° C. However, in comparison with internal combustion engines, the exhaust gas of a fuel cell removes a much smaller portion of the waste heat which is produced during operation of the fuel cell. Fuel cells therefore have a much higher cooling requirement, which must be met by powerful cooling circuits.An object of the present invention is to provide a method of operating a fuel cell system and a fuel cell system having an improved cooling function.This object is achieved by a method having the features of claim 1 and a fuel cell system having the features of claim 6. Preferred features are the subject of the dependent claims. Further advantages and features can be gathered from the general description and from the exemplary embodiments.The method according to the invention for operating a fuel cell system having a fuel cell, a cooler for providing cooling fluid, with which the fuel cell is cooled, and an exhaust line leading away from the fuel cell, is characterized in that water is separated out of an exhaust gas flowing through the exhaust line and the separated water is supplied to a cooling body of the cooler in order to cool the latter.The invention makes use of the finding that the exhaust gas of the fuel cell contains a large amount of moisture. The invention is based on the concept of dehumidifying the exhaust gas of the fuel cell and using the separated liquid to increase the cooling capacity of the cooling circuit of the fuel cell. The separated water is supplied to the cooling body of the cooler, which cools the latter. Preferably, an outer surface of the cooling body is sprayed and / or sprayed with the water. The water interacts with the outer surface of the cooling body and extracts energy from the latter, which promotes the cooling performance of the cooling system.The fuel cell system may be equipped with a special water separator for dehumidification or water separation. Furthermore, the fuel cell system may be equipped with a means for exciting and / or spraying the water onto an outer surface of the heat sink. Suitable means for the excitation and / or spraying are, for example, perforated tubes or nozzles.In a preferred embodiment of the invention, the water is separated from the exhaust gas in a muffler of the fuel cell system installed in the exhaust line. Mufflers for fuel cells are frequently connected upstream of water separators because an excessively high moisture content in the exhaust gas reduces the noise-reducing function of the mufflers. Hybrid silencers also exist in which a water separator is integrated. From a prior application of the applicant (application no. DE 10 2022 212 595) discloses such a hybrid silencer for fuel cells. The separated water has hitherto usually been discharged into the environment, i.e. for example onto the road. According to the present invention, the muffler is used as a water source with which the cooling performance can be improved.In a further preferred embodiment of the invention, the silencer has a water collection container in which the water separated from the exhaust gas is collected. In this way, a water reservoir is obtained from which water can be taken as required for cooling the cooler. The water collection container preferably has a fill level sensor, wherein the separated water is supplied to the cooling body when the fill level in the water collection container determined by the fill level sensor exceeds a predetermined threshold value. As a result, for example, a cooling of the cooler can also be initiated when an excess of water is present or the water collection container is too full.According to the description already given above and below, the object set at the beginning is also achieved by a fuel cell system having the features of claim 6, wherein the device is designed for carrying out the method described above or below. The advantages realized with the method according to the invention can be achieved in an analogous manner with the fuel cell system according to the invention.In particular, the fuel cell system has a control unit which controls the fuel cell system for carrying out the method according to the invention. For this purpose, the control unit can be connected to the sensors, actuators and / or further components of the fuel cell system necessary for this purpose in a signal-conducting manner.In particular, if the fuel cell system is part of a vehicle and the cooling body of the cooler is likewise cooled by the relative wind, the fuel cell system preferably has an exhaust air hood for channeling the exhaust air flow outgoing from the cooler. In this way, the moisture released onto the heat sink is prevented from being deposited on other components of the fuel cell system or vehicle.It is expressly pointed out that the embodiments of the invention explained above can each be combined with one another individually or in any technically meaningful combination, in each case with the subject matter of the independent claims.Modifications and embodiments of the invention and further advantages and details of the invention can be gathered from the following description and the drawing. The schematic figure shows: FIG. 1 shows an exemplary embodiment of a fuel cell system according to the invention.Individual technical features of the exemplary embodiments described below can also be combined in combination with exemplary embodiments described above and the features of the independent claims and any further claims to form articles according to the invention.FIG. 1 shows an exemplary embodiment of a fuel cell system 1 according to the invention. The fuel cell system 1 has a fuel cell 2, in the present case a hydrogen-oxygen fuel cell, to which hydrogen 20 and oxygen-containing air 21 are supplied. During operation of the fuel cell 2, heat is generated, which is why the fuel cell system 1 is equipped with a cooler 3 which provides a cooling fluid 30 with which the fuel cell 2 can be cooled. The cooler 3 is generally part of a larger cooling circuit, which is not shown here for reasons of clarity.The exhaust gas 40 formed during the power generation reaction, which is discharged in particular from the cathode of the fuel cell 2, contains water 5 (usually in the form of water vapor and water droplets). This water 5 is separated from the exhaust gas 40 in an exhaust line 4 leading away from the fuel cell 2 and fed to a cooling body 31 of the cooler 3 in order to cool the latter. The dehumidified exhaust gas 41 is discharged to an environment of the fuel cell system.In the present case, the separation of the water 5 takes place in a hybrid silencer 6 arranged in the exhaust system 4, which is designed both for noise reduction and for previous dehumidifying of the exhaust gas 40. The water 5 is collected in a water collection container 7 of the muffler 6. If the cooling requirement is increased and / or if a fill level sensor 8 of the water collection container 7 senses a predetermined amount of water in the water collection container 7, the separated water 5 is supplied to a means 10 for spraying the cooling body 31 by opening a controllable valve 9. The means 10 for spraying the cooling body 31 can direct the water 5 in the form of a spray 50 onto an outer surface of the cooling body. In this way, the cooling capacity of the cooling system can be easily increased.In addition, it should be noted that "having" does not exclude other elements or steps and "a" or "an" does not exclude a plurality.The scope of the present invention is given by the claims and is not limited by the features explained in the description or shown in the figures.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2022 212 595

[0009]

Claims

Method for operating a fuel cell system (1) having a fuel cell (2), a cooler (3) for providing cooling fluid (30), with which the fuel cell (2) is cooled, and an exhaust line (4) outgoing from the fuel cell (2), characterized in that water (5) is separated out of an exhaust gas (40) flowing through the exhaust line (4) and the separated water (5) is fed to a cooling body (31) of the cooler (3) in order to cool the latter.Method according to Claim 1, wherein the water (5) is separated from the exhaust gas (40) in a silencer (6) installed in the exhaust line (4).Method according to claim 2, wherein the silencer (6) comprises a water collection container (7) in which the water separated from the exhaust gas (40) is collected.Method according to Claim 3, wherein the water collecting container (7) has a fill level sensor (8), wherein the separated water (5) is fed to the cooling body if the fill level determined by the fill level sensor (8) exceeds a predetermined threshold value.Method according to one of the preceding claims, wherein an outer surface of the cooling body (31) is sprayed and / or sprayed with the water.Fuel cell system (1) having a fuel cell (2), a cooler (3) for providing cooling fluid (30), with which the fuel cell (2) is cooled, and an exhaust line (4) which leads away from the fuel cell (2), characterized in that the fuel cell system (1) is designed and configured to carry out the method according to one of the preceding claims.Fuel cell system (1) according to Claim 6, wherein the fuel cell system (1) has a silencer (6) installed in the exhaust line (4) for separating the water (5) from the exhaust gas (40).The fuel cell system (1) according to claim 7, wherein the muffler (6) includes a water collection container (7) for collecting the water (5) separated from the exhaust gas (40).Fuel cell system (1) according to Claim 8, wherein the water collecting container (7) has a fill level sensor (8), wherein the fuel cell system is designed and configured to supply the separated water (5) to the cooling body (31) if the fill level of the water collecting container (7) determined by the fill level sensor (8) exceeds a predetermined threshold value.Fuel cell system (1) according to one of the preceding claims, having a means (10) for exciting and / or spraying an outer surface of the cooling body (31) with the water (5).

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