Fuel cell system

Abstract

The invention relates to a fuel cell system (100) having at least one fuel cell stack (101), an air path (10), an exhaust gas path (12) and a fuel line (20), wherein air from the environment reaches the fuel cell stack (101) via the air path (10), wherein fuel is fed to the fuel cell stack (101) via the fuel line (20). The air path (10) is connected to a cooling line (30) via a branch (33), wherein the cooling line (30) is connected to a PDU unit (32).

Description

TECHNICAL FIELD

[0001] The invention relates to a fuel cell system having the features of the preamble of claim 1. BACKGROUND

[0002] Hydrogen-based fuel cells are suitable as a future mobility concept, since they only discharge water as exhaust gas and enable faster refueling times. Fuel cells are usually assembled into fuel cell stacks. Fuel cell stacks consume oxygen, which is mostly obtained from simple air in the environment, and fuel, which is mostly hydrogen, for a chemical reaction.

[0003] In a fuel cell system, voltage tapping on the fuel cell stack is achieved and processed by a power distribution unit (PDU unit). The tasks of the PDU unit are typically: ensuring the voltage, current measurement, separating the stack voltage from the system in the event of an accident, connecting the stack voltage to a DC / DC converter and then to a battery.

[0004] The components and assemblies inside the PDU unit are exposed to a large heat release due to electrical losses and resistances. For this reason, the PDU unit has to be cooled. As a cooling possibility, a suitable fan and / or a water cooling device inside the housing of the PDU unit is known. SUMMARY

[0005] The fuel cell system according to the invention having the features of the independent claims has the advantage that the air for cooling the PDU unit is extracted from the air path (cathode path). In this way, costs can be saved, since a suitable fan does not have to be installed, which provides the necessary safety in the engine room environment and blows clean air into the housing of the PDU unit.

[0006] In contrast to a water cooling device, the components of the PDU unit can be cooled directly, whereas in a water cooling device the assemblies are only indirectly cooled by air flow, which is generated inside the housing due to temperature gradients. In contrast to direct air cooling, heat pipes and Peltier elements for cooling the PDU unit only produce a small cooling effect.

[0007] With the fuel cell system according to the invention, efficient cooling of the PDU unit can be ensured. The assemblies of the PDU unit have electrical losses, which are converted into heat, so that the internal temperature of the PDU unit always continues to rise without efficient cooling and overheats the assemblies and in the worst case fails.

[0008] Advantageous configurations and extensions of the fuel cell system according to the invention are specified in the dependent claims.

[0009] The arrangement of the branch between the compressor of the air in the compressed air path and the fuel cell stack is advantageous, because in this way a high pressure drop between the branch and the environment can be established, so that a sufficiently large air mass flow for cooling can be flowed through the cooling line to the PDU unit when required.

[0010] The heat exchanger arranged between the supercharger and the branch is advantageous, because in this way the temperature of the air flowing to the PDU unit can be further reduced.

[0011] A particular advantage is achieved by the filter arranged in the air path between the inlet and the branch, because in this way the air flowing to the PDU unit is already cleaned of dust and small particles. Pure air is an essential requirement for the electronic components inside the PDU unit.

[0012] Advantageously, an adjustable throttle valve is arranged in the cooling line, because in this way the air quantity flowing to the PDU unit can be varied. In the case of a high thermal load on the components of the PDU unit, a large amount of air can be caused to flow to the PDU unit by the adjustable throttle valve. The adjustable throttle valve can reduce its cross section in the case of a small thermal load, so that less air flows to the PDU unit.

[0013] When the air in the cooling line also has a too high temperature, in order to ensure an effective cooling, a cooler in the cooling line can further reduce the temperature, so that a higher cooling efficiency is achieved with the same air quantity.

[0014] It is advantageous here that the cooler is arranged between the adjustable throttle valve and the PDU unit, because in this way only the air flowing to the PDU unit is cooled.

[0015] In the stationary state of the fuel cell system, hydrogen gas can escape from the fuel cell stack into the air path. In order to prevent the intrusion of hydrogen gas into the PDU unit, it is advantageous to arrange a check valve in the cooling line. By means of the check valve, gas exchange between the fuel cell stack and the PDU unit is prevented in the stationary state of the fuel cell system, because the closing force of the check valve cannot be overcome by the air pressure on the branch in the stationary state. This is important, because in the PDU unit there can be ignition sources which can lead to ignition of the mixture of hydrogen gas and air.

[0016] It is advantageous that the PDU unit has a pressure equalizing element or a check valve through which air can escape into the environment. Here, the pressure equalizing element can be designed in such a way that it is permeable to gases, but prevents particles and moisture from entering the PDU unit. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A schematic topology of a fuel cell system 100 according to a first embodiment is shown. DETAILED DESCRIPTION

[0018] A fuel cell system according to the present application and a method according to the present application are explained in detail below with reference to the drawings. The fuel cell system has at least one fuel cell stack 101. The at least one fuel cell stack 101 has an air path 10, an exhaust gas path 12 and a fuel line 20. The at least one fuel cell stack 101 can be used for mobile applications with high power requirements, for example in heavy goods vehicles, or for stationary applications, for example in power generators.

[0019] The air path 10 serves as an air supply line in order to supply air from the environment to the fuel cell stack 101 via an inlet 16. Arranged in the air path 10 are components which are required for operating the fuel cell stack 101. An air compressor 11 and / or a supercharger 11 can be arranged in the air path 10, which compresses or draws air in accordance with the respective operating conditions of the fuel cell stack 101. A heat exchanger 15 can be located downstream of the air compressor 11 and / or the supercharger 11, which cools the air in the air path 10 to a lower temperature.

[0020] Further components, such as a humidifier and / or valves, can also be provided inside the air path 10. Oxygen-containing air is provided to the fuel cell stack 101 via the air path 10.

[0021] The air path 10 is connected to a cooling line 30 via a branch 33. The air in the air path 10 can reach the PDU unit 32 or a housing 31 of the PDU unit 32 via the cooling line 30. The PDU unit 32 is a power distribution unit 32, which performs a voltage tapping on the fuel cell stack 101 and processes and interconnects the voltage tapping.

[0022] Furthermore, the task of the power distribution unit (PDU unit) 32 is to ensure the voltage, the current measurement, to separate the stack voltage from the system in the event of a fault being detected, to connect the stack voltage to a DC / DC converter and / or a battery.

[0023] By means of the air in the air path 10, which reaches the housing 31 of the PDU unit 32 via the cooling line 30, components in the housing 31 of the PDU unit 32 can be cooled.

[0024] The branch 33 is preferably arranged between a supercharger 11 and the fuel cell stack 101, which supercharger compresses the air in the air path 10. In order to provide the cooling line 30 with sufficiently cold air, a heat exchanger 15 can be arranged between the supercharger 11 and the branch 33.

[0025] In the air path 10, at least one filter 13 can be arranged between the inlet 16 and the branch 33, which filter filters out particles and impurities from the air. In this way, the air flowing to the PDU unit 32 is already cleaned from undesired particles and impurities.

[0026] In order to control the air from the air path 10 into the cooling line 30 as desired, an adjustable throttle 34 can be arranged in the cooling line 30.

[0027] If the air flowing from the air path 10 into the cooling line 30 does not have the desired temperature, a cooler 35 can be arranged in the cooling line 30, which cooler further cools the air in the cooling line 30. In an embodiment, the cooler 35 can be arranged between the adjustable throttle 34 and the PDU unit 32.

[0028] Furthermore, a gas check valve 37 can be arranged in the cooling line 30, which gas check valve prevents hydrogen from spreading from the fuel cell stack 101 into the cooling line 30 in a stopped state of the fuel cell system 100.

[0029] The air reaching the housing 31 of the PDU unit 32 through the cooling line 30 can be led out into the environment again by at least one pressure equalizing element 38, which is arranged in the housing 31 of the PDU unit 32. In an embodiment, the pressure equalizing element 38 is permeable to gases, but prevents particles and moisture from entering the PDU unit.

[0030] In an alternative embodiment, a further check valve 38 is arranged in the housing 31 of the PDU unit 32, through which further check valve the air reaching the housing 31 of the PDU unit 32 through the cooling line 30 can escape into the environment.

[0031] Furthermore, the fuel cell system 100 has a waste gas path 12, in which water and further components of the air from the air path 10 are transported into the environment through the outlet 18 after passing through the fuel cell stack 101.

[0032] Furthermore, the fuel cell system 100 can have a cooling cycle, which is configured for cooling the fuel cell stack 101. The cooling cycle is not depicted in the figures, as it is not an element of the present invention.

[0033] The fuel line 20 has a high-pressure tank 21 and a stop valve 22. Further components can be arranged in the fuel line 20 in order to supply the fuel cell stack 101 with fuel as required. Furthermore, a circulation line can be provided, which is not shown in the drawing, since it is not an element of the present application.

Claims

1. A fuel cell system (100), the fuel cell system having at least one fuel cell stack (101), an air path (10), an exhaust gas path (12), and a fuel line (20), wherein, Air from the environment reaches the fuel cell stack (101) through the air path (10), wherein water passing through the fuel cell stack (101) is transported to the environment through the exhaust path (12), wherein fuel is transported to the fuel cell stack (101) through the fuel line (20), characterized in that the air path (10) is connected to the cooling line (30) through a branch (33), wherein the cooling line (30) is connected to the PDU unit (32), wherein a cooler (35) is arranged in the cooling line (30), wherein an adjustable throttle valve (34) is arranged in the cooling line (30), wherein the cooler (35) is arranged between the adjustable throttle valve (34) and the PDU unit (32).

2. The fuel cell system (100) according to claim 1, characterized in that, The branch (33) is arranged between the booster (11) and the fuel cell stack (101), the booster compressing the air in the air path (10).

3. The fuel cell system (100) according to claim 2, characterized in that, A heat exchanger (15) is arranged between the booster (11) and the branch (33).

4. The fuel cell system (100) according to claim 1 or 2, characterized in that, In the air path (10), at least one filter is arranged between the inlet (16) and the branch (33).

5. The fuel cell system (100) according to claim 1 or 2, characterized in that, A gas check valve (37) is arranged in the cooling pipe (30).

6. The fuel cell system (100) according to claim 1 or 2, characterized in that, The PDU unit (32) has a pressure balancing element (38) or a check valve (38) through which air can escape into the environment.

7. The fuel cell system (100) according to claim 6, characterized in that, The pressure balancing element (38) is permeable to gas but prevents particles and moisture from entering the PDU unit (32).

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