Portable hydrogen fuel cell system and heating control method

Abstract

The application discloses a portable hydrogen fuel cell system, comprising a fuel cell stack, a hydrogen generator for providing a hydrogen production reaction site, and a heat exchange pipeline which is communicated with an air flow channel of the fuel cell stack after passing through the hydrogen generator, and heat generated by the hydrogen production reaction is introduced into the air flow channel by air flowing through the inside of the heat exchange pipeline. The application makes full use of the heat generated by the hydrogen production reaction to heat the electric pile in a cold start state, avoids additional hydrogen loss, and improves energy utilization and endurance time. External auxiliary heating in the form of heat conduction is realized by embedding an electric heating sheet in a battery monomer, so that the temperature rising speed of the battery and the temperature distribution consistency are improved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and specifically to a portable hydrogen fuel cell system and heating control method. Background Technology

[0002] Hydrogen-air fuel cells generate electricity directly through an electrochemical reaction between hydrogen and oxygen in the air, eliminating the need for combustion. This results in significant advantages such as high energy conversion efficiency, low operating noise, and clean emissions. However, the engineering application of portable hydrogen fuel cells in complex environments still faces numerous technical challenges, with cold start-up in low-temperature environments being particularly prominent. Hydrogen-air fuel cells produce water during operation, and this water is highly susceptible to freezing in low-temperature environments (especially below 0°C). This freezing can clog the pores in the gas diffusion layer and flow channels, hindering the transport of reactant gases. Furthermore, ice crystal formation can puncture the membrane electrode structure, causing irreversible damage to core components. This leads to difficulties in starting the fuel cell, severe degradation of output characteristics, or even complete failure. This problem is especially severe in portable applications lacking external insulation.

[0003] To address the aforementioned cold-start challenge, those skilled in the art have proposed various solutions. Some existing technologies employ a forced reaction heat generation method, which involves introducing excess hydrogen into the fuel cell and artificially creating an oxygen-deficient environment, causing the fuel cell voltage to drop to 0V and converting all chemical energy into heat energy. From an energy conservation perspective, this solution essentially converts the chemical energy that should have been delivered to the load into heat energy prematurely. For portable devices with fixed battery capacity, while heating can achieve startup, it severely reduces the system's effective runtime, making it undesirable in portable scenarios where energy density is already limited.

[0004] Some existing technologies use electric heating elements to heat hydrogen-producing materials to promote hydrogen release, but this approach essentially requires the energy stored in the battery to maintain the hydrogen production reaction rate. Other solutions directly wrap the fuel cell stack with a heating element, but the energy consumed in these solutions also ultimately comes from the battery or fuel cell itself. In these cases, before the fuel cell stack starts up, the heating energy relies entirely on the limited amount of electricity pre-stored in the battery. This not only increases the system's auxiliary power consumption but also causes cold starts to fail if the battery is low on power (a common condition for portable devices in the field).

[0005] A few other technical solutions attempt to recover the heat generated by the compressed air from the air compressor to preheat the incoming air. However, the air compressor itself is an energy-consuming component, and the electrical energy it consumes also comes from the system's limited energy storage. From a thermodynamic perspective, this method is a passive utilization of a low-grade heat source. Furthermore, the air compressor has relatively low power in portable devices, and the heat it generates is insufficient in extremely low-temperature environments, failing to meet the needs of rapid defrosting.

[0006] Looking at the existing technical solutions mentioned above, although their implementation paths differ, they are all constrained by a common technical bias: the assumption that the heat required for low-temperature startup must come from additional hydrogen consumption or external electrical energy. Whether it is electric heating for hydrogen production or various PTC auxiliary heating schemes, their essence is to degrade the chemical energy or stored electrical energy in the system into thermal energy to achieve defrosting, which directly results in a net reduction in the total energy of the system. Summary of the Invention

[0007] This application provides a portable hydrogen fuel cell system and its heating control method. It utilizes the large amount of heat released by the reaction of calcium hydride and water in the hydrogen generator to heat the air entering the fuel cell stack, thereby raising the temperature of the fuel cell stack. This can effectively utilize the waste heat generated during hydrogen production and solve the cold start problem of fuel cells in low-temperature environments without increasing additional hydrogen consumption. In addition, by embedding electric heating elements in the battery cells to achieve heat conduction heating, the battery temperature rise rate and temperature distribution uniformity are further improved.

[0008] To achieve the above objectives, the first aspect of this application provides the following technical solution: A portable hydrogen fuel cell system includes a fuel cell stack; a hydrogen generator for providing a site for hydrogen production reaction; and a heat exchange pipeline that passes through the hydrogen generator and connects to an airflow channel of the fuel cell stack, wherein heat generated by the hydrogen production reaction is introduced into the airflow channel by air flowing through the heat exchange pipeline.

[0009] Furthermore, it also includes a circulation switching valve group, which includes an air pump, an air circulation solenoid valve, an air intake solenoid valve, and an air exhaust solenoid valve; the outlet end of the air pump is connected to the inlet end of the heat exchange pipeline, and the outlet end of the heat exchange pipeline is connected to the air flow channel inlet of the fuel cell stack. The air outlet of the fuel cell stack is connected to the air inlet of the air circulation solenoid valve and the air outlet of the air exhaust solenoid valve, respectively; the air outlet of the air circulation solenoid valve and the air outlet of the air intake solenoid valve meet and are connected to the air inlet of the air pump; the air inlet of the air intake solenoid valve is open to the atmosphere, and the air outlet of the air exhaust solenoid valve is open to the atmosphere.

[0010] Furthermore, the portion of the heat exchange pipeline that passes through the hydrogen generator is a serpentine tube.

[0011] Furthermore, the fuel cell stack is formed by stacking multiple individual cells, and each individual cell is equipped with an electric heating element.

[0012] Furthermore, the circulation switching valve group has a cold start state and a heating state; in the cold start state, the air intake solenoid valve is closed, the air circulation solenoid valve is open, and the air exhaust solenoid valve is closed, and the air pump drives the air to circulate in a closed loop formed by the air pump, the heat exchange pipeline, the air flow channel of the fuel cell stack and the air circulation solenoid valve connected in sequence. During the heating state, the air intake solenoid valve is open, the air circulation solenoid valve is closed, and the air exhaust solenoid valve is open. Air flows sequentially through the air intake solenoid valve, the air pump, the heat exchange pipeline, and the air flow channel of the fuel cell stack before being discharged into the atmosphere.

[0013] Furthermore, when the temperature of the fuel cell stack is lower than or equal to the first temperature threshold, the cycle switching valve group is controlled to be in the cold start state, and the electric heating element is de-energized. When the temperature of the fuel cell stack is higher than the first temperature threshold and lower than the second temperature threshold, the cycle switching valve group is controlled to switch to the heating state, and the electric heating element is energized to generate heat.

[0014] Furthermore, the first temperature threshold is -5°C to 5°C, and the second temperature threshold is 45°C to 55°C.

[0015] The second aspect of this application provides the following technical solution: A heating control method for a portable hydrogen fuel cell system, applied to the system described in the first aspect, includes the following steps: S1: The hydrogen generator starts the hydrogen production process, releasing heat and producing hydrogen. S2: Obtain the current temperature T of the fuel cell stack. When the temperature T of the fuel cell stack is less than or equal to the first temperature threshold, the system enters the cold start state, and the operation process is shown in S3. When the temperature of the fuel cell stack is between the first temperature threshold and the second temperature threshold, the system enters the heating state, and the operation process is shown in S4. When the temperature of the fuel cell stack is greater than the second temperature threshold, the system enters the normal operation state, and the operation process is shown in S5.

[0016] S3: Execute cold start heating mode: Control the circulation switching valve group to be in cold start state, so that air circulates between the heat exchange pipeline and the fuel cell stack, and transfers the heat released by the exothermic chemical reaction to the fuel cell stack. During this stage, the electric heating element does not work. S4: Execute auxiliary rapid heating mode: control the cycle switching valve group to switch to the heating state and connect the power supply circuit of the electric heating element, so that the electric heating element is driven by the electrical energy generated by the fuel cell stack to heat the battery cell through heat conduction. S5: Execute normal operation mode: cut off the power supply to the electric heating element, so that the fuel cell stack can maintain its operating temperature by relying on the heat released by the exothermic chemical reaction and its own electrochemical reaction heat.

[0017] Furthermore, in the cold start heating mode, the hydrogen generated by the hydrogen generator is not supplied to the fuel cell stack, and the fuel cell stack is in an open circuit state and does not output electrical energy.

[0018] Furthermore, it also includes a shutdown and purging step: S6: After receiving the shutdown command, the system controls the fuel cell stack to output a constant small current, opens the hydrogen solenoid valve and allows hydrogen to purge through the anode channel; starts the air pump, closes the air circulation solenoid valve, and opens the air intake solenoid valve and the air exhaust solenoid valve to purge through the cathode channel; after purging, the power supply is stopped and all valves and the air pump are closed.

[0019] Working principle and beneficial effects of the present invention: (1) In the preheating stage below the freezing point of the fuel cell stack, the present invention directly recovers the waste heat of the hydrogen production reaction through the air circulation loop, realizing a true “zero external energy consumption thawing” and completely eliminating the dependence on the stored energy of the battery. This technical effect is something that existing technologies cannot achieve.

[0020] (2) By expanding the hydrogen generator from a single hydrogen supply function to a hydrogen supply + heating dual-function composite, and combining it with a switchable air circuit, the energy is optimized in a time dimension, fundamentally solving the energy paradox of low-temperature startup of portable power supplies.

[0021] (3) Since it can start up without relying on an external power source, the system of the present invention still has reliable starting capability under extreme conditions such as long-term storage in the field and battery depletion, which greatly expands the application scope of portable hydrogen fuel cells in military, emergency, scientific research and other fields. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the portable hydrogen fuel cell heating system of the present invention; Figure 2 This is a schematic diagram of the internal structure of a fuel cell stack.

[0023] The reference numerals in the accompanying drawings are as follows: fuel cell stack 1, hydrogen generator 2, hydrogen proportional valve 301, hydrogen solenoid valve 302, heating DC / DC converter 401, charging DC / DC converter 402, battery 403, air circulation solenoid valve 501, air intake solenoid valve 502, air pump 503, air exhaust solenoid valve 504, membrane electrode 101, anode plate 102, cathode plate 103, anode metal current collector 104, electric heating element 105, cathode metal current collector 106, anode fixed end plate 107, cathode fixed end plate 108, temperature probe 109, hydrogen generator 2, temperature sensor 201, pressure sensor 202, water inlet 203, air outlet 204, discharge port 205, heat exchange serpentine tube 206. Detailed Implementation

[0024] The following detailed description illustrates the specific implementation method: Example 1: This Example 1 provides a portable hydrogen fuel cell system, referring to... Figure 1 and Figure 2 The components include: fuel cell stack 1, hydrogen generator 2, hydrogen proportional valve 301, hydrogen solenoid valve 302, heating DC / DC converter 401, charging DC / DC converter 402, battery 403, air circulation solenoid valve 501, air intake solenoid valve 502, air pump 503, and air exhaust solenoid valve 504. The components of fuel cell stack 1 include membrane electrode 101, anode plate 102, cathode plate 103, anode metal current collector 104, electric heating element 105, cathode metal current collector 106, anode fixed end plate 107, cathode fixed end plate 108, and temperature probe 109. The components of hydrogen generator 2 include temperature sensor 201, pressure sensor 202, water inlet 203, air outlet 204, discharge port 205, and heat exchange serpentine tube 206.

[0025] The functions of each part are as follows: 1) Fuel Cell Stack 1: Energy Conversion Device, the site where hydrogen energy is converted into electrical energy. The peripheral auxiliary systems of a portable hydrogen fuel cell system typically include a hydrogen supply system and an air supply system. The stack structure, composed of individual cells, is as follows: Figure 2 As shown, the battery stack is composed of an anode fixed end plate 107, an anode metal current collector 104, a temperature probe 109, an anode plate 102, a membrane electrode 101, a cathode plate 103, an electric heating element 105, a cathode metal current collector 106, and a cathode fixed end plate 108 stacked sequentially. The battery stack composed of multiple battery cells is formed by repeatedly stacking the temperature probe 109, anode plate 102, membrane electrode 101, cathode plate 103, and electric heating element 105, and then stacking the anode metal current collector 104 and anode fixed end plate 107 on the anode side, and stacking the cathode metal current collector 106 and cathode fixed end plate 108 on the cathode side.

[0026] The membrane electrode assembly 101 is the core component of the fuel cell, serving as the site of chemical reactions. The anode plate 102 has hydrogen flow channels to provide the necessary hydrogen for the reaction. A temperature probe 109 is placed between the anode plate 102 and the anode metal current collector 104 to monitor the temperature of the individual cells. The cathode plate 103 has air flow channels to provide the necessary oxygen for the reaction. An annular electric heating element 105 is nested on the back of the anode plate 103 to electrically heat the cell while ensuring sufficient contact between the cathode plate 103 and the cathode metal current collector 106. The anode metal current collector 104 and the cathode metal current collector 106 collect and transfer current. The anode fixed end plate 107 and the cathode fixed end plate 108 secure the entire fuel cell stack.

[0027] 2) Hydrogen Generator 2: The device for generating hydrogen required by the fuel cell system. Its main body is a pressure-resistant, sealed metal canister. Before use, calcium hydride solid powder is filled into the canister through the discharge port 205. During use, a certain amount of water is first added into the canister through the water inlet 203. The calcium hydride reacts with the water to generate hydrogen gas and produces a large amount of heat. The temperature sensor 201 installed at the bottom of the hydrogen generator 2 is used to monitor the solution temperature, and the pressure sensor 202 installed at the top of the hydrogen generator 2 is used to monitor the gas pressure inside the canister. The generated gas enters the fuel cell stack 1 from the gas outlet 204 through the hydrogen proportioning valve 301. A heat exchange serpentine tube 206 is installed at the bottom of the hydrogen generator 2 to heat the air flowing out from the air pump 503. After the reaction is completed, the generated waste is discharged from the discharge port 205, and new calcium hydride powder is added.

[0028] 3) Hydrogen supply system: The function of hydrogen proportional valve 301 is to regulate the hydrogen pressure entering fuel cell stack 1 by adjusting the valve opening. The function of hydrogen solenoid valve 302 is to control the dead end operation mode. It is closed when the system is running normally. By periodically opening, it discharges the water and nitrogen accumulated in the anode flow channel and improves the performance of the fuel cell.

[0029] 4) Air Supply System: The function of air pump 503 is to pressurize the air. The compressed gas enters the air channel of fuel cell stack 1 through heat exchange serpentine tube 206 to provide oxygen for the electrochemical reaction. During the cold start heating process, air circulation solenoid valve 501 opens, air intake solenoid valve 502 closes, air exhaust solenoid valve 504 closes, and air pump 503 starts. Circulating air acts as a heat transfer medium to transfer the reaction heat of hydrogen production to fuel cell stack 1. After the cold start heating process is completed, the system enters normal operation. Air pump 503 starts, air circulation solenoid valve 501 closes, air intake solenoid valve 502 opens, and air exhaust solenoid valve 504 closes and periodically pulses open.

[0030] 5) Energy conversion device: The charging DC / DC 402 converts the DC power output from the fuel cell into a relatively constant voltage and outputs it to the storage battery 403, which then provides electrical energy to the load.

[0031] 6) Electric heating device: The heating DC / DC 401 converts the DC power output from the fuel cell into a relatively constant voltage and outputs it to the electric heating element 105 to improve the battery temperature rise rate.

[0032] The process is as follows: S1: In the shutdown state, the hydrogen generator 2 contains dry calcium hydride powder.

[0033] S2: After receiving the system start signal, a certain amount of water is introduced through the inlet 203. The working state of the start-up process is determined according to the temperature value fed back by the temperature probe 109. When the temperature of fuel cell stack 1 is ≤ the first temperature threshold, the system enters the cold start state, and the operation process is shown in S3. When the temperature of fuel cell stack 1 is between the first temperature threshold and the second temperature threshold, the system enters the heating state, and the operation process is shown in S4. When the temperature of fuel cell stack 1 is > the second temperature threshold ℃, the system enters the normal operation state, and the operation process is shown in S5.

[0034] S3: In the cold start state, the temperature of fuel cell stack 1 is lower than the first temperature threshold, and the battery cannot work normally. At this time, the hydrogen proportional valve 301 is closed, the air pump 503 is started, the air circulation solenoid valve 501 is opened, the air intake solenoid valve 502 is closed, and the air exhaust solenoid valve 504 is closed. The circulating air is used as a heat transfer medium to transfer the reaction heat of hydrogen production to fuel cell stack 1. When the temperature rises above the first temperature threshold, it enters the heating state.

[0035] S4: In the heating state, fuel cell stack 1 can output power, but its performance is low due to temperature. It is necessary to use the electrical energy generated by the fuel cell to accelerate the temperature rise of the battery through electric heating. At this time, the hydrogen proportional valve 301 is open, and the opening degree is adjusted according to the set hydrogen pressure. The hydrogen solenoid valve 302 is periodically pulsed open, the air pump 503 is started, the air circulation solenoid valve 501 is closed, the air intake solenoid valve 502 is open, and the air exhaust solenoid valve 504 is open. The heating DC / DC 401 outputs power to the electric heating element 105 in a constant current input manner. After the stack temperature rises above the second temperature threshold, it enters the normal operation state.

[0036] S5: In operation, fuel cell stack 1 maintains its temperature by generating heat from the hydrogen production reaction and the electrochemical reaction within the stack, without requiring additional electrical energy for heating. At this time, the hydrogen proportional valve 301 is open, and its opening degree is adjusted according to the set hydrogen pressure. The hydrogen solenoid valve 302 is periodically pulsed open, the air pump 503 is started, the air circulation solenoid valve 501 is closed, the air intake solenoid valve 502 is open, and the air exhaust solenoid valve 504 is open. The charging DC / DC 402 outputs power to the battery 403 and the load in a constant current input manner.

[0037] S6: The system receives a shutdown command and enters the shutdown state. The charging DC / DC converter 402 controls the fuel cell stack 1 to output a constant small current. The hydrogen solenoid valve 302 opens, and the hydrogen proportional valve 301 adjusts its opening according to the set pressure. Hydrogen flows through the anode channel to purge it. The air pump 503 starts, the air circulation solenoid valve 501 closes, the air intake solenoid valve 502 opens, and the air exhaust solenoid valve 504 opens. Air flows through the cathode channel to purge it. After purging, the charging DC / DC converter 402 stops working, all solenoid valves close, and the air pump 503 stops working.

[0038] S7: If the pressure signal detected by the pressure sensor 202 is low during system use, after shutdown, check in time whether all the calcium hydride material has been consumed, discharge the waste through the discharge port 205, and add new calcium hydride powder.

[0039] In summary, this invention targets the application scenario of portable hydrogen fuel cell systems. Addressing the problems of increased hydrogen consumption, reduced remaining available energy, and the inability to utilize external auxiliary heating due to the lack of cooling channels in existing technologies, this invention proposes a portable hydrogen fuel cell system and its heating device. This invention fully utilizes the heat generated by the hydrogen production reaction to heat the fuel cell stack during cold start-up, avoiding additional hydrogen loss and improving energy efficiency and driving range. Furthermore, by embedding electric heating elements within the individual cells to achieve external auxiliary heating through heat conduction, it improves the rate of temperature rise and the uniformity of temperature distribution within the fuel cell.

[0040] The above description is merely a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A portable hydrogen fuel cell system, characterized in that: This includes fuel cell stacks; hydrogen generators, which provide a site for hydrogen production reactions; The heat exchange pipeline passes through the hydrogen generator and connects to the air channel of the fuel cell stack. The heat generated by the hydrogen production reaction is introduced into the air channel by the air flowing through the heat exchange pipeline.

2. The system according to claim 1, characterized in that: It also includes a circulation switching valve group, which includes an air pump, an air circulation solenoid valve, an air intake solenoid valve, and an air exhaust solenoid valve; the outlet end of the air pump is connected to the inlet end of the heat exchange pipeline, and the outlet end of the heat exchange pipeline is connected to the air flow channel inlet of the fuel cell stack. The air outlet of the fuel cell stack is connected to the air inlet of the air circulation solenoid valve and the air outlet of the air exhaust solenoid valve, respectively; the air outlet of the air circulation solenoid valve and the air outlet of the air intake solenoid valve meet and are connected to the air inlet of the air pump; the air inlet of the air intake solenoid valve is open to the atmosphere, and the air outlet of the air exhaust solenoid valve is open to the atmosphere.

3. The system according to claim 2, characterized in that: The portion of the heat exchange pipeline that passes through the hydrogen generator is a serpentine tube.

4. The apparatus according to claim 3, characterized in that: The fuel cell stack is formed by stacking multiple individual cells, and each individual cell is equipped with an electric heating element.

5. The system according to claim 4, characterized in that, The cycle switching valve group has a cold start state and a heating state; in the cold start state, the air intake solenoid valve is closed, the air circulation solenoid valve is open, and the air exhaust solenoid valve is closed, and the air pump drives the air to circulate in a closed loop formed by the air pump, the heat exchange pipeline, the air flow channel of the fuel cell stack and the air circulation solenoid valve connected in sequence. During the heating state, the air intake solenoid valve is open, the air circulation solenoid valve is closed, and the air exhaust solenoid valve is open. Air flows sequentially through the air intake solenoid valve, the air pump, the heat exchange pipeline, and the air flow channel of the fuel cell stack before being discharged into the atmosphere.

6. The system according to claim 5, characterized in that, When the temperature of the fuel cell stack is lower than or equal to the first temperature threshold, the cycle switching valve group is controlled to be in the cold start state, and the electric heating element is de-energized. When the temperature of the fuel cell stack is higher than the first temperature threshold and lower than the second temperature threshold, the cycle switching valve group is controlled to switch to the heating state, and the electric heating element is energized to generate heat.

7. The system according to claim 6, characterized in that, The first temperature threshold is -5°C to 5°C, and the second temperature threshold is 45°C to 55°C.

8. A heating control method for a portable hydrogen fuel cell system, applied to the system as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: The hydrogen generator starts the hydrogen production reaction, releasing heat and producing hydrogen. S2: Obtain the current temperature T of the fuel cell stack. When the temperature T of the fuel cell stack is less than or equal to the first temperature threshold, the system enters the cold start state, and the operation process is shown in S3. When the temperature of the fuel cell stack is between the first temperature threshold and the second temperature threshold, the system enters the heating state, and the operation process is shown in S4. When the temperature of the fuel cell stack is greater than the second temperature threshold, the system enters the normal operation state, and the operation process is shown in S5. S3: Execute cold start heating mode: Control the circulation switching valve group to be in cold start state, so that air circulates between the heat exchange pipeline and the fuel cell stack, and transfers the heat released by the exothermic chemical reaction to the fuel cell stack. During this stage, the electric heating element does not work. S4: Execute auxiliary rapid heating mode: control the cycle switching valve group to switch to the heating state and connect the power supply circuit of the electric heating element, so that the electric heating element is driven by the electrical energy generated by the fuel cell stack to heat the battery cell through heat conduction. S5: Execute normal operation mode: cut off the power supply to the electric heating element, so that the fuel cell stack can maintain its operating temperature by relying on the heat released by the exothermic chemical reaction and its own electrochemical reaction heat.

9. The heating control method according to claim 8, characterized in that, In the cold start heating mode, the hydrogen generated by the hydrogen generator is not supplied to the fuel cell stack, and the fuel cell stack is in an open circuit state and does not output electrical energy.

10. The heating control method according to claim 9, characterized in that, It also includes a shutdown and purging procedure: S6: After receiving the shutdown command, the system controls the fuel cell stack to output a constant small current, opens the hydrogen solenoid valve and allows hydrogen to purge through the anode channel; starts the air pump, closes the air circulation solenoid valve, and opens the air intake solenoid valve and the air exhaust solenoid valve to purge through the cathode channel; after purging, the power supply is stopped and all valves and the air pump are closed.

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