Fuel cell system with improved separation between coolant medium and hydrogen

Abstract

To provide a fuel cell system with improved separation between hydrogen and coolant media.SOLUTION: A fuel cell system includes a fuel cell stack, a housing, a first coolant port, a second coolant port, and a cooling device having a coolant pump and a heat exchanger in fluid communication with the coolant pump. The housing includes an upper side and a bottom side. The fuel cell stack is arranged inside the housing. The first coolant port and the second coolant port each comprise a coolant tube having an inner tube, an outer tube and a gap between the inner tube and the outer tube. Each of the first coolant port and the second coolant port extends through the housing such that an inner end is closer to the upper side than an outer end is. The first coolant port and the second coolant port are coupled to the cooling device and a first coolant path of the fuel cell stack to form a coolant loop.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fuel cell system and a vehicle having such a fuel cell system.

Background Art

[0002] Fuel cell systems for generating electric power on vehicles are well known. In the fuel cell process, hydrogen supplied to the anode side and oxygen supplied to the cathode side combine to form water, while generating an electric current and heat. In order to maintain an appropriate operating state, each fuel cell is cooled by a cooling device. For example, the cooling device circulates a coolant, and the coolant absorbs heat in the cooling path of the fuel cell stack and releases the heat through a heat exchanger.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Liquid-cooled fuel cell systems having a solid polymer electrolyte membrane (PEM) often use flammable or potentially flammable coolants such as ethylene glycol water mixtures. Since space applications need to consider additional safety compared to ground vehicles or applications, an object of the present invention is to propose a fuel cell system including improved separation between a cooling medium-containing zone and a hydrogen-containing zone of the fuel cell system.

Means for Solving the Problems

[0004] This object is achieved by a fuel cell system having the features of independent claim 1. Advantageous embodiments and further improvements can be apparent from the dependent claims and the following description.

[0005] A fuel cell system is proposed comprising a fuel cell stack, a housing, a first coolant port, a second coolant port, a coolant pump, and a cooling device having a heat exchanger in fluid communication with the coolant pump, wherein the housing includes an upper and a bottom, the fuel cell stack is disposed within the housing, the first and second coolant ports each include a coolant tube having an inner tube, an outer tube, and a gap between the inner and outer tubes, each of the first and second coolant ports extends through the housing in such a manner that its inner end is inclined to be closer to the top than its outer end, and the first and second coolant ports are coupled to the cooling device and a first coolant path of the fuel cell stack to form a coolant loop.

[0006] A fuel cell stack includes an arrangement of individual fuel cells, which are electrically connected to each other, such as in series. By providing an appropriate number of individual fuel cells and appropriate interconnections, a desired voltage level and current can be achieved. It is also conceivable to provide multiple groups of fuel cells and connect those groups in series and / or parallel to achieve a desired current and voltage, as well as a desired maximum output.

[0007] Individual fuel cells can be realized as solid polymer electrolyte membrane fuel cells, which include an arrangement consisting of an anode, a membrane, and a cathode. The operating temperature of such PEM fuel cells can generally be in the range of 50 to about 80°C or 90°C. High-temperature PEM fuel cells with higher operating temperatures exist. Fuel cell stacks can be provided in the form of a stack of bipolar plates and membranes placed between them, resulting in a series connection of multiple individual PEM fuel cells. It is obvious that bipolar plates include flow regions on each of their sides for the distribution of hydrogen, oxygen or air and water or water vapor. Bipolar plates may include an internal coolant distribution flow region to achieve a cooling function within the fuel cell stack.

[0008] The housing is interpreted as an enclosure that at least surrounds the fuel cell stack. It defines a hydrogen-containing space or envelope, as hydrogen can only be present in the immediate vicinity of the fuel cell stack. By providing a housing that surrounds the fuel cell stack, the hydrogen-containing atmosphere is confined to a defined space.

[0009] The first and second coolant ports provide connections between the incoming chilled coolant and the outgoing heated coolant and the fuel cell stack. Thus, both coolant ports enter the internal space of the housing from the outside and extend to the fuel cell stack. Since the inner end is positioned closer to the upper side of the housing, the coolant flows downwards through the gap between the inner and outer tubes according to its slope and is moved solely by gravity. Therefore, if the housing is positioned in a specific orientation, leaked coolant can always flow out of the housing. Thus, it is a very simple but effective method of separating the coolant from the hydrogen-containing atmosphere inside the housing.

[0010] The coolant pump and heat exchanger may be located outside the housing. Therefore, the majority of the coolant-containing components are outside the housing. The risk of coolant leaking into the housing is further reduced. The distance between the fuel cell stack and the adjacent wall (through which one of the coolant ports extends) is to be as small as possible. Therefore, each section of the coolant port inside the housing is to be as short as possible to further reduce the risk of leaked coolant entering the housing.

[0011] The first coolant port may be located downstream of the coolant pump, and the inner tube of the first coolant port is in fluid communication with the coolant pump and connected to the first inlet of the first coolant path, while the inner tube of the second coolant port is connected to the first outlet of the first coolant path and is in fluid communication with the heat exchanger. The first inlet and first outlet may be located as close together as possible in the housing wall to reduce the length of the coolant path to the fuel cell stack. Both the inner and outer tubes are connected to the fuel cell stack, and the inner tube is dedicated to guiding the coolant to the fuel cell stack.

[0012] The fuel cell system may further include a hydrogen circulation pump that is in fluid communication with the anode outlet and anode inlet of the fuel cell stack, the hydrogen circulation pump including a second coolant path having a second coolant inlet and a second coolant outlet, the second coolant inlet and second coolant outlet located in a bypass of the coolant loop. The hydrogen circulation pump may be located in the wall of the housing, and the pump heat exchanger may be accessible from outside the housing. For example, the pump may be located directly in the side wall within the housing. The pump heat exchanger having the second coolant path may be located outside each wall, and the pump and pump heat exchanger are thermally coupled. The material of the pump heat exchanger, pump housing, mounting surface and / or at least local sections of the housing may be selected to have good thermal conductivity, such as copper, aluminum or magnesium. Also, the distance between the heat generating element of the pump and the pump heat exchanger can be reduced as much as possible. This further improves the separation of hydrogen and coolant.

[0013] As described above, the section of the circulation pump including the second coolant path may be located on the outside of the housing, while the section of the circulation pump that comes into contact with hydrogen may be located on the inside of the housing. The circulation pump may include a multi-component pump housing, where one of the components may include the second coolant path and be mounted on the outside of the housing, while the other components of the pump housing may be mounted on the inside of the housing of the fuel cell system.

[0014] It is further conceivable that the housing within the fuel cell system may include a hydrogen release opening on its upper side or adjacent to it. Therefore, hydrogen reaching the internal space of the housing, being lighter than air, can escape from the housing through the release opening.

[0015] Furthermore, in the fuel cell system, at least one of the first coolant port, the second coolant port, and the coolant leading components of the coolant loop includes a fire-resistant shield. The fire-resistant shield may include an additional layer of suitable material that can extend the melt-down time. Thus, the fire-resistant shield protects the coolant tube from hydrogen for a given time frame. This shield allows the tube to withstand a hydrogen flame for a given time and prevents further leakage of the coolant fluid into the hydrogen-containing region.

[0016] For example, the fire shield may include a coating and / or an additional metal shield. The coating may be primarily composed of flame-retardant materials, such as minerals, organohalogen compounds, organophosphorus compounds, organic compounds, polymer composites, and others, which may be filled with metal derivatives. The metal shield may include foil or sheet metal made from steel, molybdenum, nickel, platinum, titanium, tungsten, or others. Alternatively, metal compound nanoparticles such as zinc oxide, zinc borate, magnesium hydroxide, and layered double hydroxides may be used to provide effective flame retardants. The fire shield may preferably be placed on the outer tube.

[0017] Furthermore, at least one hydrogen processing balance element of the plant component may be located within the housing to supply hydrogen to the fuel cell stack. The plant balance element is understood to be a set of auxiliary equipment items that enable the fuel cell system to operate. It may include a cooler and coolant guide tubes and lines. Furthermore, it may include a hydrogen circuit configured to supply hydrogen to the fuel cell. If the fuel cell system is an air-supplied fuel cell system, the plant balance element may also include an air circuit configured to supply air to the fuel cell. It is conceivable that as many hydrogen processing components as possible be located within the housing. Thus, an even more improved separation of hydrogen and coolant is achieved.

[0018] The fuel cell system may further include at least one leak sensor designed to detect coolant, the at least one leak sensor communicating with a signaling device for indicating a leak, and the at least one leak sensor being in fluid communication with the gap between a first coolant port and / or a second coolant port. Thus, when coolant reaches the gap between the tubes, each leak sensor will detect the leak and an alarm signal may be transmitted to an alarm device. This may include displaying a message on a screen, storing an entry in an electronic maintenance book, and transmitting an electronic message to a workshop or, if the aircraft includes the fuel cell system according to the present invention, to a ground station.

[0019] The present invention further relates to a vehicle comprising at least one electrical consumer and the above-described at least one fuel cell system. The at least one electrical consumer may be any type of electrical consumer. The vehicle may include at least one electric motor for providing propulsion in the vehicle or for performing a specific function. The at least one electrical consumer may also include lighting, galley equipment, entertainment equipment and others.

[0020] The vehicle can be an airplane. The fuel cell system may, by way of example, replace an auxiliary power unit and / or a generator, and is connected to the main power bus inside the airplane. The fuel cell system may be dedicated to providing several discrete functions, such as providing power to a galley or a group of galleys or a propulsion unit.

[0021] At least one fuel cell system may be arranged in a pressurized area of the airplane. However, it is also conceivable that at least one fuel cell system may be arranged in a non-pressurized area of the airplane.

[0022] Exemplary embodiments are shown in more detail hereinafter using the attached drawings. The drawings are schematic and not to scale. The same reference numbers refer to identical or similar elements.

Brief Description of the Drawings

[0023] [Figure 1] Shows a fuel cell system. [Figure 2] Shows a fuel cell system including peripheral components. [Figure 3] Shows an airplane.

Modes for Carrying Out the Invention

[0024] Figure 1a shows a fuel cell system 2 including a fuel cell stack 4, a housing 6, a first coolant port 8, and a second coolant port 10. The fuel cell stack 4 includes a plurality of individual fuel cells, which are not shown in detail here. The fuel cell stack 4 is supplied with hydrogen from a hydrogen source 12 and air from an air source 14. Those sources are connected to the fuel cell stack 4 and reach it partially through the housing 6. A cooling device 16 is provided, which includes a coolant pump 18 and a heat exchanger 20, which are coupled to the first coolant port 8 and the second coolant port 10. The coolant ports 8 and 10 are connected inside the fuel cell stack 4 to a first coolant path 22. Thus, a coolant loop is provided.

[0025] The housing 6 defines an internal space 24, where a hydrogen-rich atmosphere may exist during the operation of the fuel cell stack 4. The hydrogen source 12 may include arrangements such as valves, supply lines, sensors, etc., and as many hydrogen processing components as possible are arranged within the internal space 24 to provide separation between the coolant and hydrogen.

[0026] The first coolant port 8 is a double tube and has an inner tube 26 and an outer tube 28, which are shown enlarged in Figure 1b. The inner tube 26 and the outer tube 28 are preferably arranged concentrically with each other. The outer tube 28 exemplarily includes a refractory shield 29 in the form of a metal foil. However, a coating of non-metallic material may also be possible.

[0027] The inner end 30 of the first coolant port 8 is arranged closer to the upper side 32 of the housing 6 than the outer end 34, and the upper side 32 is opposite to the bottom side 33. The same applies to the second coolant port 10. Thus, the first coolant port 8 and the second coolant port 10 are tilted, and as a result, the coolant reaching the gap 36 between the inner tube 26 and the outer tube 28 flows out of the housing 6 and is moved only by gravity.

[0028] The inner tube 26 is connected to a coolant supply line 38, and the line 38 is arranged downstream of the coolant pump 18, and the pump is arranged downstream of the heat exchanger 20 and is in fluid communication with it. The inner tube 26 of the second coolant port 10 is connected to the heat exchanger 20. Thus, the first coolant path 22 results in the heating of the coolant, and the coolant then flows through the heat exchanger 20 and dissipates heat. The coolant pump 18 pumps the chilled coolant through the coolant supply line 38 to the inner tube 26, which then reaches the first coolant path 22 again. This is done continuously to provide continuous cooling of the fuel cell stack 4.

[0029] A hydrogen outlet 40 is provided on the upper side 32 of the housing 6. A discharge pipe 42 may be arranged here, and the discharge pipe 42 enables hydrogen to flow out of the internal space 24 to the surrounding environment or to a further remote location. Since hydrogen is lighter than air, it automatically reaches the hydrogen outlet 40.

[0030] As shown in Figure 2, the fuel cell system 2 includes a hydrogen circulation pump 56, which has a second coolant path 57 having a second coolant inlet 59 and a second coolant outlet 61, and the second coolant path 57 is connected to a bypass 54 of the coolant supply line 38. Thus, the hydrogen circulation pump 56 can also be cooled with coolant.

[0031] Exemplary, a leak sensor 35 is positioned in the gap 36 and coupled to a signaling device 37, the signaling device 37 may be a screen that notifies the user of the fuel cell system 2 or the user of another physical object in which the fuel cell system 2 is installed of a potential leak.

[0032] Figure 2 shows the fuel cell system 2 in more detail. Here, the fuel cell 44 is shown very schematically in a block-oriented diagram. It includes an anode 46, a cathode 48, a first cooling path 22, and an electrical connector 50, the electrical connector 50 representing an electrical interface, i.e., a connection terminal, that is connected to a power bus or rail. An electrical consumer 52 is connected to the fuel cell 44 and supplied with current.

[0033] The first cooling path 22 is connected to the coolant pump 18 and the heat exchanger 20. Between the first cooling path 22 and the coolant pump 18, a bypass 54 is provided to allow cooling of the hydrogen circulation pump 56. The hydrogen circulation pump 56 allows excess hydrogen from the anode outlet 58 to be returned to the hydrogen supply flow and circulated to the anode inlet 60. Upstream of the hydrogen circulation pump 56, a water separator 62 is provided, designed to remove water from the anode exhaust gas. A purge valve 64 actively purges the anode 46, and the purge valve 64 is connected to the hydrogen outlet 40, i.e., the outlet pipe 42.

[0034] A hydrogen supply valve 66 is located downstream of the hydrogen source 12, allowing for the selective supply of hydrogen to the anode inlet 60. The cathode 48 receives air from an air supply source 14, and a humidifier 68 humidifies the supply air using moist cathode exhaust gas 70 from the cathode outlet 72. The air supply source can be interrupted by a first shut-off valve 74 located immediately upstream of the cathode inlet 76. The cathode outlet 72 is directly coupled to a second shut-off valve 78. Excess exhaust is released from the exhaust outlet 80. The housing 6 may enclose most of the components related to hydrogen processing, including the supply valve 66, the hydrogen circulation pump 56, the water separator 62, and the purge valve 64.

[0035] Figure 3 shows an aircraft 82 including a pressurized fuselage 84. The fuel cell system 2 may be located inside the pressurized fuselage 84. [Explanation of Symbols]

[0036] 2. Fuel cell system 4 Fuel cell stack 6 Housing 8. First coolant port 10. Second coolant port 12 Hydrogen sources 14. Air source 16 Cooling device 18 Coolant pump 20 Heat exchanger 22 First coolant pathway 24 Interior space 26 Inner tube 28 Outer tube 29 Fire-resistant shield 30 Inner end 32 Upper side 33 Bottom 34 Outer edge 35 Leak Sensor 36 Gap 37 Signaling device 38 Coolant supply line 40 Hydrogen outlet 42 Release tube 44 Fuel Cell 46 Anodes 48 Cathode 50 Electrical connection device 52 Electricity consumption 54 Detour 56 Hydrogen circulation pump 57 Second coolant pathway 58 Anode Exit 59 Second coolant inlet 60 Anode entrance 61 Second coolant outlet 62 Water separation equipment 64 Purge valve 66 Hydrogen supply valve 68 Humidifier 70 Cathode exhaust gas 72 Cathode Outlet 74 First shut-off valve 76 Cathode entrance 78 Second shut-off valve 80 Exhaust outlet 82 Airplane 84 Torso

Claims

1. Fuel cell stack (4), Housing (6) and The first coolant port (8) and A second coolant port (10) and A cooling device (16) having a coolant pump (18) and a heat exchanger (20) that is in fluid communication with the coolant pump (18), A fuel cell system (2) including, The housing (6) includes an upper side (32) and a bottom side (33), The fuel cell stack (4) is located inside the housing (6). The first coolant port (8) and the second coolant port (10) each include a coolant tube having an inner tube (26), an outer tube (28), and a gap (36) between the inner tube (26) and the outer tube (28). Each of the first coolant port (8) and the second coolant port (10) extends through the housing (6) in such a manner that its inner end (30) is inclined to be closer to the upper side (32) than its outer end (34). The first coolant port (8) and the second coolant port (10) are connected to the first coolant path (22) of the cooling device (16) and the fuel cell stack (4) to form a coolant loop. The fuel cell stack (4) further includes a hydrogen circulation pump (56) that is in fluid communication with the anode outlet (58) and anode inlet (60), The hydrogen circulation pump (56) includes a second coolant path (57) having a second coolant inlet (59) and a second coolant outlet (61), The second coolant inlet (59) and the second coolant outlet (61) are located in the bypass (54) of the coolant loop. The section of the circulation pump (56) containing the second coolant path (57) is located outside the housing (6), The section of the circulation pump (56) that comes into contact with hydrogen is located inside the housing (6). Fuel cell system (2).

2. The coolant pump (18) and the heat exchanger (20) are arranged on the outside of the housing (6). The fuel cell system (2) according to claim 1.

3. The first coolant port (8) is located downstream of the coolant pump (18), The inner tube (26) of the first coolant port (8) is in fluid communication with the coolant pump (18) and is connected to the first inlet of the first coolant path (22), The inner tube (26) of the second coolant port (10) is connected to the first outlet of the first coolant path (22) and is in fluid communication with the heat exchanger (20). The fuel cell system (2) according to claim 1.

4. The housing (6) includes a hydrogen release opening (40) on or adjacent to the upper side (32), The fuel cell system (2) according to claim 1.

5. The first coolant port (8), the second coolant port (10) of the coolant loop, and at least one of the coolant guide components include a fire shield (29). The fuel cell system (2) according to claim 1.

6. The fire-resistant shield (29) includes a coating and / or additional metal shield (29), The fuel cell system (2) according to claim 5.

7. At least one hydrogen processing balance element of the plant components is located within the housing (6) to supply hydrogen to the fuel cell stack (4), The fuel cell system (2) according to claim 1.

8. The system further includes at least one leak sensor (35) designed to detect coolant, The at least one leak sensor (35) is in communication with a signaling device (37) for indicating a leak. The at least one leak sensor (35) is in fluid communication with the gap (36) of the first coolant port (8) and / or the second coolant port (10). The fuel cell system (2) according to claim 1.

9. A vehicle (82) comprising at least one electrical consumer (52) and at least one fuel cell system (2) according to any one of claims 1 to 8.

10. The vehicle (82) according to claim 9, which is an airplane (82).

11. The vehicle (82) according to claim 10, wherein at least one of the fuel cell systems (2) is located in the pressurized area of ​​the aircraft (82).

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