Fuel cell stack structure capable of stably operating in low-temperature environment

Abstract

A fuel cell stack structure capable of stably operating in a low-temperature environment comprises a shell, a stack is arranged in the shell, a first air inlet channel is arranged between the top of the stack and the shell, a second air inlet channel is arranged between the bottom of the stack and the shell, and an exhaust fan is arranged at an air outlet of the stack. And two baffles and two baffle rotation driving devices are arranged on the outer side of a gas outlet of the electric pile. According to the invention, the first air inlet channel and the second air inlet channel are respectively arranged between the top and the bottom of the electric pile and the shell, and waste heat and waste gas generated by the reaction of the electric pile are returned through the baffle, so that the first end plate and the second end plate of the electric pile are surrounded by high-temperature air in a low-temperature environment, and stable operation in the low-temperature environment is ensured. The stable operation of the galvanic pile in a low-temperature environment is further improved by arranging plugging structures in part of air grooves on the bipolar plates on the two sides or enabling the cross sectional area of the air grooves to be smaller, or changing the number and the area of small heat dissipation holes of the bipolar plates on the two sides.

Description

Technical Field

[0001] This invention relates to the field of chemistry, and more particularly to fuel cells, especially a fuel cell stack structure that can operate stably in low-temperature environments. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are devices that directly convert the chemical energy of hydrogen and oxygen from the air into electrical energy. They offer advantages such as high energy conversion efficiency, zero pollution, low noise, and high safety and reliability, attracting widespread attention and finding extensive applications in many fields. Existing fuel cell structures are mainly divided into two categories: open-cathode fuel cells and closed-cathode fuel cells. Closed-cathode fuel cells have dedicated cooling channels, water pumps, radiators, and cooling water tanks, resulting in better environmental adaptability and stability. However, the cooling system significantly increases the complexity of the stack structure and control system, and they are generally used in larger fuel cell systems, such as those used in vehicles or as backup power sources. Open-cathode fuel cells, also known in the industry as air-cooled fuel cells, utilize a special structural design. Air is drawn in by a fan, serving not only as the reactant gas but also carrying away the heat generated during the reaction to cool the cell. This combines air supply and system heat dissipation, simplifying the system and making it particularly suitable for weight-sensitive applications such as portable fuel cells and drones. However, the stoichiometric ratio of airflow on the cathode side of such batteries is generally very high, with airflow exceeding ten or even hundreds of times the stoichiometric ratio. This makes these fuel cells highly susceptible to ambient temperature fluctuations, especially in low-temperature environments. The intake of large amounts of cooler air leads to excessive heat dissipation, preventing the fuel cell from maintaining a suitable operating temperature. When the fuel cell stack operates at excessively low temperatures, moisture generated on the air side cannot be promptly drained from the cathode, causing cathode flooding, performance degradation, and even reverse polarity. It can also lead to icing on the cathode side, preventing prolonged operation at low temperatures.

[0003] The fuel cell stack consists of two end plates and several individual cells connected in series in the middle. Each individual cell includes a bipolar plate, a MEA (membrane electrode assembly), etc. During operation, the individual cells closest to the two end plates are exposed to the external environment, resulting in uneven temperature distribution on both sides and potentially causing performance degradation. Since the individual cells in the fuel cell stack are connected in series, a problem with one cell will affect the output of the entire stack. Therefore, it is necessary to improve the performance reliability of the individual cells closest to the two end plates.

[0004] Secondly, the bipolar plates of the open-cathode stack are made of graphite plates or metal sheets. Graphite plates dissipate heat and receive air through the same air channel, while metal sheets dissipate heat and receive air through different air channels. Sometimes, to increase heat dissipation efficiency and reaction uniformity, small heat dissipation holes are made on the surface of the air channels. However, in the prior art, because the air channels and heat dissipation holes increase the heat dissipation effect, they further lead to uneven temperature on both sides of the individual plates near the two end plates. Existing technologies use insulation or heating of the end plates to ensure the performance of the individual plates near the end plates, but this method increases the complexity of system accessories and control, as well as the system size. Summary of the Invention

[0005] The purpose of this invention is to provide a fuel cell stack structure that can operate stably in low-temperature environments. This fuel cell stack structure that can operate stably in low-temperature environments aims to solve the technical problem of uneven temperature on both sides of a single plate near the end plate in the prior art.

[0006] The present invention discloses a fuel cell stack structure capable of stable operation in low-temperature environments, comprising a housing, a fuel cell stack disposed within the housing, a first air inlet channel between the top of the fuel cell stack and the housing, a second air inlet channel between the bottom of the fuel cell stack and the housing, an air inlet at one end of the fuel cell stack, and an air outlet at the other end of the fuel cell stack. The air inlet of the fuel cell stack faces the closed end of the housing and communicates with the first and second air inlet channels. An exhaust fan is disposed at the air outlet of the fuel cell stack. Two baffles and two baffle rotation drive devices are disposed on the outer side of the air outlet of the fuel cell stack. The positions of the two baffles correspond to the positions of the first and second air inlet channels, respectively. The power output terminals of the two baffle rotation drive devices are respectively connected to the two baffles, and the control terminals of the baffle rotation drive devices are connected to a controller.

[0007] Furthermore, the baffle rotation drive device includes a motor, the output shaft of which is connected to the baffle via a rotating shaft, the axis of which is perpendicular to the axis of the fuel cell outlet.

[0008] Furthermore, the fuel cell stack includes a first end plate, a second end plate, and multiple individual plates disposed between the first end plate and the second end plate. Each individual plate includes a bipolar plate, and each bipolar plate has multiple air grooves.

[0009] Furthermore, the bipolar plate is made of a corrugated metal sheet, which forms multiple air grooves with different opening directions. A sealing structure is provided in part of the air grooves on the bipolar plate adjacent to the first end plate and the bipolar plate adjacent to the second end plate. The sealing structure is located at one end near the air inlet of the fuel cell stack, or extends from one end of the air groove to the other end to seal the entire air groove.

[0010] Furthermore, the number of air grooves on the bipolar plate adjacent to the first end plate and the bipolar plate adjacent to the second end plate is less than the number of air grooves on any other bipolar plate.

[0011] Furthermore, the total cross-sectional area of ​​the air grooves on the bipolar plates adjacent to the first end plate and the bipolar plates adjacent to the second end plate is less than the total cross-sectional area of ​​the air grooves on any other bipolar plate.

[0012] Furthermore, each bipolar plate has multiple small heat dissipation holes on the sidewall of its air groove.

[0013] Furthermore, the number of heat dissipation holes on the bipolar plate adjacent to the first end plate and the bipolar plate adjacent to the second end plate is less than the number of heat dissipation holes on any other bipolar plate.

[0014] Furthermore, the total area of ​​the heat dissipation holes on the bipolar plate adjacent to the first end plate and the total area of ​​the heat dissipation holes on the bipolar plate adjacent to the second end plate are respectively smaller than the total area of ​​the heat dissipation holes on any other bipolar plate.

[0015] Furthermore, a heating device is provided inside the housing, outside the air inlet of the fuel cell stack.

[0016] Compared with the prior art, the present invention has positive and obvious effects. The present invention sets a first air inlet channel and a second air inlet channel between the top and bottom of the fuel cell stack and the shell, respectively. The waste heat gas from the fuel cell stack reaction is returned through a baffle, so that the outside of the first end plate and the second end plate of the fuel cell stack is surrounded by air with a higher temperature in a low-temperature environment. The temperature difference between the two sides of the single plate adjacent to the first end plate and the second end plate is reduced, ensuring stable operation in a low-temperature environment.

[0017] Furthermore, by setting sealing structures in some air grooves on the bipolar plates adjacent to the first end plate and the bipolar plates adjacent to the second end plate, or by designing and calculating to ensure that the total cross-sectional area of ​​the intake air grooves on the bipolar plates adjacent to the first end plate and the bipolar plates adjacent to the second end plate is less than the total cross-sectional area of ​​the air grooves on any other bipolar plate, or by changing the number and area of ​​heat dissipation holes on the air grooves on the bipolar plates adjacent to the first end plate and the bipolar plates adjacent to the second end plate, the stable operation of the fuel cell stack in low-temperature environments can be further improved. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a fuel cell stack structure that can operate stably in a low-temperature environment according to the present invention.

[0019] Figure 2 This is a schematic diagram of the internal structure of a fuel cell stack structure that can operate stably in a low-temperature environment according to the present invention.

[0020] Figure 3 This is a schematic diagram of a bipolar plate made of graphite plates in a fuel cell stack structure that can operate stably in a low-temperature environment according to the present invention.

[0021] Figure 4 This is a schematic diagram of the first type of air trench on a bipolar plate made of metal sheets in a fuel cell stack structure that can operate stably in a low-temperature environment according to the present invention.

[0022] Figure 5 This is a schematic diagram of a second type of air groove on a bipolar plate made of metal sheets in a fuel cell stack structure that can operate stably in a low-temperature environment according to the present invention.

[0023] Figure 6 This is a schematic diagram showing the sealing of air channels in the bipolar plates of a fuel cell stack structure capable of stable operation in low-temperature environments according to the present invention.

[0024] Figure 7 This is a schematic diagram of the heat dissipation holes of the bipolar plate in a fuel cell stack structure that can operate stably in a low-temperature environment according to the present invention.

[0025] Figure 8 This is a schematic diagram showing the sealing of the front end of the air trench in a fuel cell stack structure that can operate stably in a low-temperature environment according to the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments, but the present invention is not limited to these embodiments. Any similar structures and similar variations of the present invention should be included within the scope of protection of the present invention. The use of directions such as up, down, front, back, left, and right in the present invention is only for the convenience of clear description and is not intended to limit the technical solution of the present invention.

[0027] like Figures 1-8 As shown, a fuel cell stack structure capable of stable operation in low-temperature environments according to the present invention includes a housing 1, a fuel cell stack 2 disposed within the housing 1, a first air inlet channel 3 disposed between the top of the fuel cell stack 2 and the housing 1, a second air inlet channel 4 disposed between the bottom of the fuel cell stack 2 and the housing 1, an air inlet 5 disposed at one end of the fuel cell stack 2, and an air outlet 6 disposed at the other end of the fuel cell stack 2. The air inlet 5 of the fuel cell stack 2 is disposed facing the closed end of the housing 1 and is connected to the first air inlet channel 3 and the second air inlet channel 4. An exhaust fan 7 is disposed at the air outlet 6 of the fuel cell stack 2. Two baffles 8 and two baffle rotation drive devices (not shown in the figure) are disposed on the outside of the air outlet 6 of the fuel cell stack 2. The positions of the two baffles 8 correspond to the positions of the first air inlet channel 3 and the second air inlet channel 4, respectively. The power output ends of the two baffle rotation drive devices are respectively connected to the two baffles 8, and the control ends of the baffle rotation drive devices are connected to a controller.

[0028] According to the controller's operating algorithm, when the ambient temperature is high or the intake air temperature is high and no adjustment is needed, the motor drives the two baffles 8 to flatten, and air enters the fuel cell stack 2 from the first air intake channel 3 and the second air intake channel 4. A small portion of the air oxygen enters the fuel cell stack 2 and is consumed by the fuel cell stack 2. As a reactant, it passes through the gas diffusion layer and enters the fuel cell cathode to undergo an electrochemical reaction and generate water. The rest of the air undergoes heat exchange, which removes the waste heat generated in the fuel cell stack 2 and carries away the heat of the fuel cell stack 2. Then, it is discharged from the air outlet 6 of the fuel cell stack 2 through the exhaust fan.

[0029] In low-temperature environments, temperature sensors are installed at various locations, including the external environment, the fuel cell stack's air intake, and the fuel cell stack's exhaust. After a successful low-temperature start-up of the fuel cell, these sensors monitor the ambient temperature, fuel cell stack air intake temperature, fuel cell stack temperature, and fuel cell stack exhaust temperature in real time. A motor adjusts the angles of two baffles 8 in real time, redirecting some or all of the hot air exhausted from the fuel cell stack 2 into the first and second air intake channels 3 and 4, where it mixes with fresh air before being drawn back into the fuel cell stack 2. By adjusting the positions of the two baffles 8, the mixing ratio of fresh air intake and hot air exhaust from the fuel cell stack 2 can be achieved, thereby controlling the intake temperature of the fuel cell stack 2 and ensuring stable operation of the fuel cell stack 2 in low-temperature environments. Different fuel cell stacks 2, different power outputs, and different ambient temperatures will require different mixing ratios of hot and cold air, necessitating adjustments to the baffles 8 based on actual conditions.

[0030] In this invention, a first air inlet channel 3 and a second air inlet channel 4 are respectively provided between the top and bottom of the fuel cell stack 2 and the shell 1. The waste heat gas from the reaction of the fuel cell stack 2 is returned through the baffle 8, so that the outside of the first end plate 9 and the second end plate 10 of the fuel cell stack 2 are surrounded by air with a higher temperature in a low-temperature environment. The temperature difference between the two sides of the single plate adjacent to the first end plate 9 and the second end plate 10 is reduced, ensuring stable operation in a low-temperature environment.

[0031] Furthermore, each of the baffle rotation drive devices includes a motor, and the output shaft of the motor is connected to the baffle 8 through a rotating shaft (not shown in the figure). The axial direction of the rotating shaft is perpendicular to the axial direction of the gas outlet 6 of the fuel cell stack 2.

[0032] Furthermore, the fuel cell stack 2 includes a first end plate 9, a second end plate 10, and multiple single plates disposed between the first end plate 9 and the second end plate 10. Each single plate includes a bipolar plate 11, and each bipolar plate 11 is provided with multiple air grooves 12.

[0033] Furthermore, the bipolar plate 11 is made of a corrugated metal sheet, which forms multiple air grooves 12 with different opening directions. A sealing structure 16 is provided in part of the air grooves 12 on the bipolar plate 11 adjacent to the first end plate 9 and the bipolar plate 11 adjacent to the second end plate 10. The sealing structure 16 is located at one end near the air inlet 5 of the fuel cell stack 2, or extends from one end of the air groove 12 to the other end to seal the entire air groove 12.

[0034] By sealing the air groove 12, the amount of cold air entering is reduced, thus reducing the temperature difference between the two sides of the bipolar plates 11. Figure 8 As shown, when the sealing structure 16 is located at one end near the air inlet 5 of the fuel cell stack 2, air cannot enter the air groove 12 from the front end. However, air can enter from the other unsealed air grooves 12 to be heated, and then enter the sealed air groove 12 from the rear end in the opposite direction to maintain the temperature.

[0035] Specifically, the sealing structure can be achieved by processing the bipolar plate or by adding an external sealing material.

[0036] Furthermore, the number of air grooves 12 on the bipolar plate 11 adjacent to the first end plate 9 and the bipolar plate 11 adjacent to the second end plate 10 is less than the number of air grooves 12 on any other bipolar plate 11.

[0037] Furthermore, the total cross-sectional area of ​​the air grooves 12 on the bipolar plate 11 adjacent to the first end plate 9 and the bipolar plate 11 adjacent to the second end plate 10 is less than the total cross-sectional area of ​​the air grooves 12 on any other bipolar plate 11.

[0038] Furthermore, each bipolar plate 11 has multiple small heat dissipation holes 13 on the side wall of the air groove 12.

[0039] Furthermore, the number of heat dissipation holes 13 on the bipolar plate 11 adjacent to the first end plate 9 and the bipolar plate 11 adjacent to the second end plate 10 is less than the number of heat dissipation holes 13 on any other bipolar plate 11.

[0040] Furthermore, the total area of ​​the heat dissipation holes 13 on the bipolar plate 11 adjacent to the first end plate 9 and the total area of ​​the heat dissipation holes 13 on the bipolar plate 11 adjacent to the second end plate 10 are respectively smaller than the total area of ​​the heat dissipation holes 13 on any other bipolar plate 11.

[0041] By reducing, eliminating, or blocking the air grooves 12 or heat dissipation holes 13 on the bipolar plates 11 adjacent to the first end plate 9 and the second end plate 10, the entry of cold air is reduced, heat dissipation is reduced, the temperature difference between the two monolithic bipolar plates 11 is reduced, and the operational stability of the fuel cell stack in a low-temperature environment is improved.

[0042] Furthermore, a heating device 14 is provided outside the air inlet of the fuel cell stack 2 within the housing 1. The heating device can be a heating wire mesh, a perforated heating element, or other porous heating device, which can preheat the intake air during fuel cell stack startup to ensure normal low-temperature startup. The control of the heating device 14 depends on the ambient temperature, the fuel cell stack intake temperature, the internal temperature of the fuel cell stack, and the fuel cell stack exhaust temperature. The heating device can be located in different positions within the housing depending on the design, and all such devices should be included within the scope of protection of this invention.

[0043] Specifically, in this embodiment, the housing 1, exhaust fan 7, baffle rotation drive device, first end plate 9, air groove 12, heat dissipation holes 13, heating device 14, etc., all adopt well-known solutions in the prior art, which are already understood by those skilled in the art and will not be described in detail here. The single piece also includes structures such as film electrode 15.

Claims

1. A fuel cell stack structure capable of stable operation in low-temperature environments, characterized in that: The device includes a housing, within which an electric fuel cell stack is housed. A first air inlet channel is provided between the top of the electric fuel cell stack and the housing, and a second air inlet channel is provided between the bottom of the electric fuel cell stack and the housing. An air inlet is provided at one end of the electric fuel cell stack, and an air outlet is provided at the other end. The air inlet of the electric fuel cell stack faces the closed end of the housing and is connected to the first and second air inlet channels. An exhaust fan is provided at the air outlet of the electric fuel cell stack. Two baffles and two baffle rotation drive devices are provided on the outside of the air outlet of the electric fuel cell stack. The positions of the two baffles correspond to the positions of the first and second air inlet channels, respectively. The power output terminals of the two baffle rotation drive devices are connected to the two baffles, respectively, and the control terminals of the baffle rotation drive devices are connected to a controller.

2. The fuel cell stack structure capable of stable operation in low-temperature environments according to claim 1, characterized in that: The fuel cell stack includes a first end plate, a second end plate, and multiple individual plates disposed between the first end plate and the second end plate. Each individual plate includes a bipolar plate, and each bipolar plate has multiple air grooves.

3. The fuel cell stack structure capable of stable operation in low-temperature environments according to claim 2, characterized in that: The bipolar plate is made of a corrugated metal sheet, which forms multiple air grooves with different opening directions. A sealing structure is provided in part of the air grooves on the bipolar plate adjacent to the first end plate and the bipolar plate adjacent to the second end plate. The sealing structure is located at one end near the air inlet of the fuel cell stack, or extends from one end of the air groove to the other end to seal the entire air groove.

4. A fuel cell stack structure capable of stable operation in low-temperature environments according to claim 2, characterized in that: The number of air grooves on the bipolar plate adjacent to the first end plate and the bipolar plate adjacent to the second end plate is less than the number of air grooves on any other bipolar plate.

5. A fuel cell stack structure capable of stable operation in a low-temperature environment according to claim 2, characterized in that: The total cross-sectional area of ​​the air grooves on the bipolar plates adjacent to the first end plate and the bipolar plates adjacent to the second end plate is less than the total cross-sectional area of ​​the air grooves on any other bipolar plate.

6. A fuel cell stack structure capable of stable operation in a low-temperature environment according to claim 2, characterized in that: Each bipolar plate has multiple heat dissipation holes on the sidewall of its air groove. The number of heat dissipation holes on the bipolar plate adjacent to the first end plate and the bipolar plate adjacent to the second end plate is less than the number of heat dissipation holes on any other bipolar plate.

7. A fuel cell stack structure capable of stable operation in a low-temperature environment according to claim 2, characterized in that: The total area of ​​the heat dissipation holes on the bipolar plate adjacent to the first end plate and the total area of ​​the heat dissipation holes on the bipolar plate adjacent to the second end plate are respectively smaller than the total area of ​​the heat dissipation holes on any other bipolar plate.

8. A fuel cell stack structure capable of stable operation in low-temperature environments according to claim 1, characterized in that: A heating device is provided outside the air inlet of the fuel cell stack in the housing.

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