Direct methanol fuel cell generator using industrial methanol and method of operating the same

Abstract

A direct methanol fuel cell generator using industrial methanol and its operating method are disclosed. Within a set time period, a secondary battery within the system applies voltage to the fuel cell stack via a voltage adjustment circuit, reducing byproducts that poison the catalyst. Simultaneously, the secondary battery also supplies power to the load, ensuring continuous power output from the generator. By actively controlling the output current of the fuel cell stack, the output power is gradually increased, avoiding the adverse effects of instantaneous high-current discharge on the fuel cell stack. Furthermore, a drain port is provided to facilitate solution replacement, allowing users to periodically change the solution and preventing the accumulation of toxic substances within the system. The advantages of this invention are that it can use inexpensive and readily available industrial methanol for power generation, reducing the operating cost of direct methanol fuel cells and simplifying fuel supply. It also solves the problems of power supply and battery charging for special equipment under field conditions.

Description

Technical Field

[0001] This invention relates to a direct methanol fuel cell generator using industrial methanol and its operating method, particularly a direct methanol fuel cell generator suitable for use in field or battlefield environments, and belongs to the field of fuel cells. Background Technology

[0002] Direct methanol fuel cells (DMFCs) are chemical reaction devices that directly convert the chemical energy in methanol into electrical energy. DMFCs have advantages such as simple structure, no need for fuel reforming, and reaction products mainly consisting of water and carbon dioxide, making them an environmentally friendly green energy source. They are considered one of the most ideal miniaturized and portable power sources and have broad application prospects in transportation, communication, military, and aerospace.

[0003] DMFCs primarily use high-concentration or pure chromatographically pure methanol as fuel, with a lower concentration methanol solution reacting in the electrode catalyst layer. Chromatographically pure methanol is expensive and difficult to procure due to its high purity, especially in remote areas where fuel supply is often unreliable. Industrial methanol is inexpensive and readily available, but it contains numerous impurities and generates byproducts that can poison the catalyst, leading to a rapid decline in the discharge performance of the fuel cell stack.

[0004] Chinese invention patent CN201611121218.8 discloses a method for anti-poisoning of direct methanol fuel cells. The fuel used in the direct methanol fuel cell is industrial methanol or methanol containing isopropanol impurities. During operation, the cathode gas supply is intermittent, and a voltage of -0.2-0.82V is applied to the cathode during the periods when the cathode gas supply is interrupted. This effectively solves the problem of catalyst poisoning caused by isopropanol in industrial methanol, leading to battery performance degradation. However, this method only reduces the acetone generated from isopropanol in industrial methanol impurities back to isopropanol, mitigating the poisoning effect on the catalyst. The reduced impurities still exist in the methanol solution, and their concentration increases with the continuous consumption of industrial methanol. In reality, industrial methanol also contains ethanol and other impurity ions.

[0005] In summary, existing methods for using industrial methanol in direct methanol fuel cells have certain limitations. Summary of the Invention

[0006] To address the shortcomings of the prior art, this invention provides a direct methanol fuel cell generator that can use industrial methanol and its operating method, particularly suitable for use in field or battlefield environments.

[0007] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0008] A direct methanol fuel cell generator using industrial methanol includes: a controller, a control system, and a direct methanol fuel cell system connected in sequence, and also includes a secondary battery connected to the control system.

[0009] The control system includes three controllable switches and three voltage conversion circuits, wherein:

[0010] One end of the first controllable switch is connected to the positive terminal of the secondary battery, and the other end is connected to the positive input terminal of the first voltage conversion circuit; one end of the second controllable switch is connected to the positive terminal of the fuel cell stack in the direct methanol fuel cell system, and the other end is connected to the positive input terminal of the second voltage conversion circuit; one end of the third controllable switch is connected to the positive terminal of the secondary battery, and the other end is connected to the generator output terminal; the positive output terminal of the first voltage conversion circuit is connected to the positive terminal of the fuel cell stack, and the negative input terminal is connected to the negative output terminal; the positive output terminal of the second voltage conversion circuit is connected to the positive terminal of the secondary battery, and the negative input terminal is connected to the negative output terminal; the positive input terminal of the third voltage conversion circuit is connected to the positive terminal of the secondary battery, and the positive output terminal is connected to the direct methanol fuel cell system, and the negative input terminal is connected to the negative output terminal; all three controllable switches are connected to the controller; the negative terminals of the fuel cell stack, the secondary battery, and the three voltage conversion circuits are all connected together.

[0011] The second voltage conversion circuit includes a microcontroller and peripheral circuits and a MOSFTE switching unit connected to it. The MOSFTE switching unit consists of three parallel MOSFTEs, each of which is connected to the controller.

[0012] The direct methanol fuel cell system includes: a fuel cell stack, a silencer filter, a gas pump, a gas-liquid separation assembly, a fuel circulation pump, a condenser, and a fuel pump, wherein:

[0013] The silencer filter is connected to the cathode inlet of the fuel cell stack via an air pump. The cathode outlet of the fuel cell stack is connected to the cathode recovery port of the gas-liquid separation component via a condenser. The liquid outlet of the gas-liquid separation component is connected to the anode inlet of the fuel cell stack via a fuel circulation pump. The anode outlet of the fuel cell stack is connected to the anode recovery port of the gas-liquid separation component. The fuel inlet of the gas-liquid separation component is connected to the outlet of the fuel pump.

[0014] The direct methanol fuel cell system further includes a drain port located between the fuel circulation pump and the anode inlet of the fuel cell stack, and the drain port is provided with a drain port cover.

[0015] The operating method of a direct methanol fuel cell generator using industrial methanol includes the following steps:

[0016] (1) Start timing for m minutes;

[0017] (2) When the timing ends, disconnect the second controllable switch and the three MOSFETs, and determine whether the timing time meets m minutes. If it does, proceed to the next step; otherwise, continue timing until m minutes are met.

[0018] (3) Delay for n seconds;

[0019] (4) Turn off the air pump;

[0020] (5) Delay j seconds;

[0021] (6) Close the first controllable switch;

[0022] (7) Delay k seconds;

[0023] (8) Disconnect the first controllable switch;

[0024] (9) Delay p seconds;

[0025] (10) Start the air pump;

[0026] (11) Delay for n seconds;

[0027] (12) Close the second controllable switch;

[0028] (13) Delay for n seconds;

[0029] (14) Close the first MOSFET;

[0030] (15) Delay for n seconds;

[0031] (16) Close the second MOSFET;

[0032] (17) Delay for n seconds;

[0033] (18) Close the third MOSFET and start the timer again to begin a new cycle.

[0034] The value of m ranges from 10 to 65; the value of n ranges from 2 to 10; the value of j ranges from 1 to 6; the value of k ranges from 5 to 35; and the value of p ranges from 0.5 to 5.

[0035] The present invention has the following beneficial effects and advantages:

[0036] 1. This invention can reduce byproducts and reduce the poisoning effect of impurities in industrial methanol on the catalyst.

[0037] 2. This invention can gradually increase the output power of the fuel cell stack, effectively slowing down the degradation of the fuel cell stack's discharge performance when using low-quality fuel.

[0038] 3. This invention can use inexpensive and readily available industrial methanol for power generation, reducing the operating cost of direct methanol fuel cells and the difficulty of ensuring fuel supply. Attached Figure Description

[0039] Figure 1 This invention provides a schematic diagram of a direct methanol fuel cell generator using industrial methanol.

[0040] Figure 2 This invention provides a schematic diagram of the electrical connection of a direct methanol fuel cell generator using industrial methanol.

[0041] Figure 3 This invention provides a schematic diagram of the working method of a direct methanol fuel cell generator using industrial methanol in response to industrial methanol fuel.

[0042] Figure 4 This invention provides a schematic diagram of the first voltage conversion circuit for a direct methanol fuel cell generator using industrial methanol.

[0043] Figure 5 This invention provides a schematic diagram of the second voltage conversion circuit for a direct methanol fuel cell generator using industrial methanol.

[0044] Figure 6 This invention provides a schematic diagram showing the changes in fuel cell stack voltage and output current over time after measures are taken for industrial methanol fuel in a direct methanol fuel cell generator.

[0045] Figure 7 The present invention provides a voltage variation curve of the fuel stack of a 25W direct methanol fuel cell generator using industrial methanol over time. Detailed Implementation

[0046] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0047] This invention proposes a direct methanol fuel cell generator using industrial methanol and its operating method. The invention will be described in detail below with reference to the accompanying drawings and embodiments, but the invention is not limited to the following embodiments.

[0048] Figure 1This invention provides a schematic diagram of a direct methanol fuel cell generator using industrial methanol. In the diagram, 101 is the fuel cell stack, which directly converts the chemical energy stored in the fuel into electrical energy. 102 is an air pump connected to the cathode inlet pipe of the fuel cell stack, supplying air to the cathode. 103 is a silencer filter connected to the air pump inlet pipe, filtering impurities in the air and reducing pump noise. 104 is a fan; its start and stop can be used to adjust the condenser's condensation effect. 105 is the condenser, used to condense water vapor at the cathode outlet. 106 is a gas-liquid separation assembly, equipped with a cathode recovery port, an anode recovery port, a fuel inlet, and a liquid outlet, separating carbon dioxide gas from the anode material and water from the cathode material. Simultaneously, the added high-concentration fuel or pure fuel is diluted. The cathode outlet of the fuel cell stack is connected to the cathode recovery port of the gas-liquid separation component via a condenser. The liquid outlet on the gas-liquid separation component is connected to the anode inlet of the fuel cell stack via a fuel circulation pump. The anode outlet of the fuel cell stack is connected to the anode recovery port of the gas-liquid separation component. The outlet of the fuel pump is connected to the fuel inlet of the gas-liquid separation component. 107 is the fuel circulation pump, used to deliver liquid fuel to the fuel cell stack. 108 is the drain port, through which liquid in the gas-liquid separation component can be quickly discharged after the fuel circulation pump is started. 109 is the drain port cover, which can block the drain port to ensure normal fuel circulation; it can be opened when drainage is needed. 110 is the fuel pump, which replenishes high-concentration fuel or pure fuel to the gas-liquid separation component according to the controller's output signal. 111 is the controller, which controls the operation of various electronic components. 112 is the secondary battery, which can store the electrical energy output by the fuel cell stack and can also discharge when needed.

[0049] Figure 2This invention provides an electrical connection diagram for a direct methanol fuel cell generator using industrial methanol. In the diagram, 201 is a first controllable switch, one end connected to the positive terminal of the secondary battery, and the other end connected to the positive input terminal of a first voltage conversion circuit, used to control whether the first voltage conversion circuit operates. 202 is a second controllable switch, one end connected to the positive terminal of the fuel cell stack, and the other end connected to the positive input terminal of the second voltage conversion circuit, used to control whether the second voltage conversion circuit operates. 203 is a third controllable switch, one end connected to the positive terminal of the secondary battery, and the other end connected to the generator output port, used to control whether the generator outputs electrical energy. 204 is a second voltage conversion circuit, with its positive input terminal connected to the second controllable switch and its positive output terminal connected to the positive terminal of the secondary battery, converting the output voltage of the fuel cell stack. 205 is a first voltage conversion circuit, with its positive input terminal connected to the first controllable switch and its positive output terminal connected to the positive terminal of the fuel cell stack, converting the output voltage of the secondary battery. 206 is the third voltage conversion circuit. Its positive input terminal is connected to the positive terminal of the secondary battery, and its positive output terminal is connected to components such as the air pump, fuel circulation pump, and fan, providing the required voltage to each component.

[0050] Figure 3 This invention provides a schematic diagram of the working method of a direct methanol fuel cell generator using industrial methanol in response to industrial methanol fuel.

[0051] 1. Start timing for m minutes;

[0052] 2. When the timing ends, disconnect the second controllable switch and the three MOSFETs E, F, and G. If the condition is not met, continue timing.

[0053] 3. Delay for n seconds;

[0054] 4. The air pump stops;

[0055] 5. Delay j seconds;

[0056] 6. Close the first controllable switch;

[0057] 7. Delay k seconds;

[0058] 8. Disconnect the first controllable switch;

[0059] 9. Delay p seconds;

[0060] 10. Start the air pump;

[0061] 11. Delay for n seconds;

[0062] 12. Close the second controllable switch;

[0063] 13. Delay for n seconds;

[0064] 14. Close the MOSFET numbered E;

[0065] 15. Delay for n seconds;

[0066] 16. Close the MOSFET numbered F;

[0067] 17. Delay for n seconds;

[0068] 18. Close the MOSFET numbered G and start the timer again to enter a new cycle.

[0069] The values ​​of m range from 10 to 65, n range from 2 to 10, j range from 1 to 6, k range from 5 to 35, and p range from 0.5 to 5.

[0070] Figure 4 This invention provides a schematic diagram of the first voltage conversion circuit for a direct methanol fuel cell generator using industrial methanol. In this embodiment, a low-dropout, high-efficiency linear voltage regulator LM1085-ADJ is used. The resistance of R1 in the circuit is 121Ω, and the resistance of R2 is 845Ω. The output voltage is set to 10V through these two resistors.

[0071] Figure 5 This invention provides a schematic diagram of the second voltage conversion circuit for a direct methanol fuel cell generator using industrial methanol. In this embodiment, a four-switch buck-boost controller LTC3780 is used. The resistance of resistor R1 is 10kΩ, and the resistance of resistor R2 is 196kΩ. The output voltage is set to 16.5V through resistors R1 and R2. The microcontroller controls the operating states of three MOSFETs (E, F, and G), thus controlling the maximum output current of the second voltage conversion circuit. When MOSFETs E, F, and G are open, the maximum output current of the second voltage conversion circuit is set by resistor RS1. When MOSFET G is closed, RS2 and RS1 are connected in parallel. At this time, the maximum output current of the second voltage conversion circuit is set by the resistance value of the parallel connection of RS1 and RS2. This process continues; the maximum output current of the second voltage conversion circuit changes once each MOSFET is closed.

[0072] Figure 6 This invention provides a schematic diagram illustrating the voltage and output current changes of the fuel cell stack over time after measures are taken for industrial methanol fuel in a direct methanol fuel cell generator. After the gas pump stops, the fuel cell stack voltage equals the output voltage of the first voltage conversion circuit. After the gas pump restarts and enters the discharge state, the output current of the fuel cell stack gradually increases.

[0073] Figure 7 The present invention provides a voltage variation curve of the fuel stack of a 25W direct methanol fuel cell generator using industrial methanol over time.

[0074] In this embodiment, m is 30, n is 5, j is 3, k is 20, and p is 1. The generator's cumulative test time is approximately 1134 hours. Linear fitting of the fuel cell stack voltage curve yields a stack voltage decay rate of 0.96 mV / h.

[0075] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited to the above description. Any changes or substitutions based on the technology disclosed in this invention should be covered within the scope of protection of this invention.

Claims

1. A direct methanol fuel cell generator using industrial methanol, characterized in that, include: The controller, control system and direct methanol fuel cell system are connected in sequence, and the secondary battery connected to the control system is also included. The control system includes three controllable switches and three voltage conversion circuits, wherein: One end of the first controllable switch is connected to the positive terminal of the secondary battery, and the other end is connected to the positive input terminal of the first voltage conversion circuit; one end of the second controllable switch is connected to the positive terminal of the fuel cell stack in the direct methanol fuel cell system, and the other end is connected to the positive input terminal of the second voltage conversion circuit; one end of the third controllable switch is connected to the positive terminal of the secondary battery, and the other end is connected to the generator output terminal; the positive output terminal of the first voltage conversion circuit is connected to the positive terminal of the fuel cell stack, and the negative input terminal is connected to the negative output terminal; the positive output terminal of the second voltage conversion circuit is connected to the positive terminal of the secondary battery, and the negative input terminal is connected to the negative output terminal; the positive input terminal of the third voltage conversion circuit is connected to the positive terminal of the secondary battery, and the positive output terminal is connected to the direct methanol fuel cell system, and the negative input terminal is connected to the negative output terminal; all three controllable switches are connected to the controller; the negative terminals of the fuel cell stack, the secondary battery, and the three voltage conversion circuits are all connected together; The second voltage conversion circuit includes a microcontroller and peripheral circuits and a MOSFTE switching unit connected to it respectively. The MOSFTE switching unit consists of three parallel MOSFTEs, each of which is connected to the controller. The direct methanol fuel cell system includes: a fuel cell stack, a silencer filter, an air pump, a gas-liquid separation assembly, a fuel circulation pump, a condenser, and a fuel pump.

2. The direct methanol fuel cell generator using industrial methanol according to claim 1, characterized in that, The silencer filter is connected to the cathode inlet of the fuel cell stack via an air pump. The cathode outlet of the fuel cell stack is connected to the cathode recovery port of the gas-liquid separation component via a condenser. The liquid outlet of the gas-liquid separation component is connected to the anode inlet of the fuel cell stack via a fuel circulation pump. The anode outlet of the fuel cell stack is connected to the anode recovery port of the gas-liquid separation component. The fuel inlet of the gas-liquid separation component is connected to the outlet of the fuel pump.

3. The direct methanol fuel cell generator using industrial methanol according to claim 2, characterized in that, The direct methanol fuel cell system further includes a drain port located between the fuel circulation pump and the anode inlet of the fuel cell stack, and the drain port is provided with a drain port cover.

4. The method of operating a direct methanol fuel cell generator using industrial methanol according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Start timing for m minutes; (2) When the timing ends, disconnect the second controllable switch and the three MOSFETs, and determine whether the timing time meets m minutes. If it does, proceed to the next step; otherwise, continue timing until m minutes are met. (3) Delay for n seconds; (4) Turn off the air pump; (5) Delay j seconds; (6) Close the first controllable switch; (7) Delay k seconds; (8) Disconnect the first controllable switch; (9) Delay p seconds; (10) Start the air pump; (11) Delay for n seconds; (12) Close the second controllable switch; (13) Delay for n seconds; (14) Close the first MOSFET; (15) Delay for n seconds; (16) Close the second MOSFET; (17) Delay for n seconds; (18) Close the third MOSFET and start the timer again to begin a new cycle.

5. The operating method of the direct methanol fuel cell generator using industrial methanol according to claim 4, characterized in that, The value of m ranges from 10 to 65; the value of n ranges from 2 to 10; the value of j ranges from 1 to 6; the value of k ranges from 5 to 35; and the value of p ranges from 0.5 to 5.

Images