Cathode closed air-cooled fuel cell system and control method thereof

Abstract

This invention provides a cathode-enclosed air-cooled fuel cell system and its control method. This system possesses high-efficiency start-up capability and is particularly suitable for low-temperature environments. The system includes a fuel cell, an oxidant gas supply unit, a fuel gas supply unit, a temperature management unit, and a control and conversion unit (FDC). The oxidant gas supply unit has the functions of internal recirculation and heating of the reaction air, enabling rapid preheating of the fuel cell. The temperature management unit has the functions of internal cooling air recirculation and heating. Under the premise of internal recirculation, when heating is activated, it constitutes an auxiliary heating cycle mode; when heating and fuel cell power generation and heat generation are activated simultaneously, it constitutes a mixed cycle mode; and when fuel cell power generation and heat generation are activated, it constitutes a self-heating cycle mode. The system and method of this invention improve the start-up efficiency, operational stability, and environmental adaptability of the fuel cell.

Description

Technical Field

[0001] This invention relates to the field of air-cooled fuel cell system technology, and in particular to a cathode-enclosed air-cooled fuel cell system. Background Technology

[0002] A fuel cell is an energy conversion device that directly converts the chemical energy stored in fuel gas and oxidant gas (hereinafter referred to as "reactant gas") into electrical energy through an electrochemical reaction. It has the advantages of high energy conversion efficiency and low environmental pollution, and has broad application prospects.

[0003] Fuel cells typically have a stacked structure composed of multiple individual cells, collectively referred to in the industry as a fuel cell stack (hereinafter referred to as "fuel cell"). Each individual cell has the following structure: a membrane electrode assembly (MEA) and a bipolar plate (BP), with a flow field formed between them for supplying reactant gases along the surface of the MEA. The reactant gases flow from a supply manifold located at the outer edge of one side of the bipolar plate across the surface of the MEA and toward an exhaust manifold located at the outer edge of the other side of the bipolar plate. An electrochemical reaction occurs by supplying fuel gas to the anode electrode surface and oxidant gas to the cathode electrode surface, thereby generating electricity. Its working principle is as follows:

[0004] Anode: H2 → 2H + +2e -

[0005] Cathode: 1 / 2O2 + H + +2e - →H2O

[0006] Fuel cell reaction: H2 + 1 / 2O2 → H2O

[0007] Fuel cells can be classified into air-cooled fuel cells (hereinafter referred to as "air-cooled fuel cells" or "fuel cells") and liquid-cooled fuel cells (hereinafter referred to as "liquid-cooled fuel cells") based on their cooling methods.

[0008] Patent Document 1: Invention Patent with Application Publication Number CN115441011.

[0009] Patent Document 1 describes a method for circulating cooling air using the heat generated during fuel cell power generation to raise the temperature to a suitable level for fuel cell power generation. Utilizing the heat generated by fuel cell power generation for preheating requires the fuel cell itself to have a certain heat generation capacity. In low-temperature environments, if the air-cooled fuel cell does not yet have sufficient heat generation capacity, starting the air-cooled fuel cell will become very slow or even fail.

[0010] Because the heat capacity of air as a refrigerant is much lower than that of water as a refrigerant, air-cooled fuel cells are more prone to thermal runaway, and their operating conditions are more demanding in low-temperature environments. On the other hand, unlike liquid-cooled fuel cells, air-cooled fuel cells do not require coolant preservation or insulation when stored at low temperatures. Therefore, a highly efficient low-temperature start-up system for air-cooled fuel cells needs to be designed. Summary of the Invention

[0011] This invention addresses the aforementioned problems by providing an air-cooled fuel cell system capable of efficient startup. It possesses the following advantages: the system enables efficient startup in low-temperature environments, solving the problem of difficult low-temperature startup in traditional air-cooled fuel cells; the integrated control and conversion unit (FDC) simplifies the system structure and improves control and energy conversion efficiency; the temperature management unit ensures the fuel cell operates at its optimal temperature, enhancing system stability and efficiency; the system supports multi-mode control, flexibly switching between auxiliary heating cycle, mixed heating cycle, and self-heating cycle modes to adapt to different ambient temperatures and operating conditions; the design of a rapid preheating circulating air passage shortens startup time; the application of a heater improves system preheating efficiency and temperature control capabilities; precise control of the thermostatic valve enhances cooling efficiency and temperature control flexibility; the system design considers low-temperature adaptability, eliminating the need for coolant storage or insulation; and the use of filters ensures the quality of air entering the system, improving system lifespan and performance. These features collectively result in significant advantages for this air-cooled fuel cell system in terms of startup efficiency, operational stability, environmental adaptability, and energy conversion efficiency.

[0012] Specifically, the air-cooled fuel cell system of the present invention is characterized in that the air-cooled fuel cell system comprises: a fuel cell, which is a membrane power generation device that uses fuel gas and oxidant gas to carry out an electrochemical reaction; an oxidant gas supply unit that supplies reaction air to the fuel cell; a fuel gas supply unit that supplies reaction hydrogen to the fuel cell; a temperature management unit that provides the fuel cell with an optimal operating temperature; and a control and conversion unit (hereinafter referred to as "FDC") that integrates a fuel cell controller and a DC-DC converter for controlling the fuel cell and controlling the load output.

[0013] The aforementioned oxidant gas supply unit includes: a reaction air supply passage, a reaction air exhaust passage, and a reaction air circulation passage.

[0014] Specifically, the reaction air supply path includes: a first filter for purifying the reaction air entering the oxidant supply unit; an oxidant actuator for providing driving force for the reaction air to enter, exit, and circulate in the fuel cell; a first valve for controlling the opening of the reaction air inlet of the fuel cell; and a first temperature sensor for collecting the reaction air temperature at the fuel cell inlet.

[0015] Specifically, the reaction air emission path includes a second valve that controls the opening of the aforementioned fuel cell reaction air exhaust port.

[0016] Specifically, the reaction air circulation path includes: a third valve to control the opening of the reaction air circulation path; and a first heater to heat the reaction gas entering the reaction air circulation path.

[0017] The aforementioned reactive air supply path is connected to both the atmospheric end and the temperature control unit at its front end, and to the fuel cell reactive air inlet at its rear end. The aforementioned reactive air exhaust path is connected to the fuel cell reactive air exhaust port at its front end, and to the atmospheric end at its rear end. The aforementioned reactive air circulation path is connected to the fuel cell reactive air exhaust port at its front end, and to the oxidizer driver at its rear end. The aforementioned reactive air supply path and the aforementioned reactive air exhaust path together constitute the reactive air exhaust path during fuel cell power generation. The aforementioned reactive air supply path and the aforementioned reactive air circulation path together constitute the circulating air path for rapid preheating of the fuel cell. The aforementioned FDC controls the opening and closing of the first heater using the temperature collected by the aforementioned first temperature sensor.

[0018] The temperature management unit described above includes: a cooling air supply path, a cooling air exhaust path, a cooling air circulation path, and a cooling air bypass.

[0019] Specifically, the cooling air supply path includes: a second filter to purify the cooling air entering the temperature management unit; a fourth valve to control the opening of the cooling air inlet of the fuel cell; and a second temperature sensor to collect the temperature of the cooling air at the fuel cell inlet.

[0020] Specifically, the cooling air exhaust path includes: a third temperature sensor to collect the temperature of the fuel cell; a coolant driver to provide driving force for the cooling air to enter, exit and circulate in the fuel cell; and a thermostatic valve to control the opening ratio of the fuel cell cooling air exhaust port toward two different paths, the two paths being connected to the atmospheric end and the front end of the cooling air circulation path, respectively.

[0021] Specifically, the cooling air circulation path includes a second heater, which heats the cooling gas entering the cooling air circulation path.

[0022] Specifically, the cooling air bypass includes a fifth valve that controls the opening degree of the fuel cell cooling air exhaust port connected to the front end of the reaction air supply passage.

[0023] The aforementioned cooling air supply passage is connected to the atmosphere at its front end and to the fuel cell cooling air inlet at its rear end. The aforementioned cooling air exhaust passage is connected to the fuel cell cooling air exhaust port at its front end and to both the atmosphere and the front end of the aforementioned cooling air recirculation passage at its rear end. The aforementioned cooling air recirculation passage is connected to the rear end of the aforementioned cooling air exhaust passage and to the fuel cell cooling air inlet at its rear end. The aforementioned cooling air bypass is connected to the rear end of the aforementioned coolant driver and to the rear end of the aforementioned reaction air supply passage at its rear end.

[0024] The aforementioned cooling air supply path and cooling air exhaust path together constitute the cooling air exhaust path during fuel cell power generation. The aforementioned cooling air supply path, cooling air exhaust path, and cooling air circulation path together constitute the circulating air path for rapid preheating of the fuel cell. The aforementioned FDC uses the temperature collected by the aforementioned third temperature sensor to control the fuel cell system to switch between auxiliary heating cycle mode, mixed heating cycle mode, and self-heating cycle mode. The aforementioned FDC achieves the switching between different modes by controlling the aforementioned actuators. Attached Figure Description

[0025] Appendix Figure 1 This is a simplified structural diagram of an air-cooled fuel cell system described in this application;

[0026] Appendix Figure 2 This is a control flowchart of the oxidant gas supply unit of an air-cooled fuel cell system as described in this application;

[0027] Appendix Figure 3 This is a flowchart illustrating the start-up control of an air-cooled fuel cell system as described in this application.

[0028] The attached figures are labeled as follows:

[0029] 10-Fuel cell; 100-Oxidant gas supply unit; 101-First filter; 102-Oxidant actuator; 103-First valve; 104-First temperature sensor; 105-Second valve; 106-Third valve; 107-First heater; 200-Fuel gas supply unit; 201-Hydrogen source; 202-Pressure regulating valve; 203-Heat exchanger; 204-Safety valve; 205-Ejector; 206-Fourth temperature sensor; 207-Moisture separator; 208-Solenoid valve; 209-Check valve; 300-Temperature management unit; 301-Second filter; 302-Fourth valve; 303-Second temperature sensor; 304-Third temperature sensor; 305-Coolant actuator; 306-Thermostatic valve; 307-Second heater; 308-Fifth valve; 90-FDC. Detailed Implementation

[0030] The present application will now be described in further detail with reference to the accompanying drawings.

[0031] Figure 1 This is a simplified structural diagram of an air-cooled fuel cell system according to this application. The air-cooled fuel cell system of the present invention is characterized by comprising: a fuel cell 10, which is a membrane power generation device that uses fuel gas and oxidant gas to perform an electrochemical reaction; an oxidant gas supply unit 100, which supplies reaction air to the fuel cell; a fuel gas supply unit 200, which supplies reaction hydrogen to the fuel cell; a temperature management unit 300, which provides the fuel cell with an optimal operating temperature; and an FDC 90, which integrates a fuel cell controller and a DC-DC converter for controlling the fuel cell and controlling the load output.

[0032] The aforementioned oxidant gas supply unit 100 includes: a reaction air supply passage, a reaction air exhaust passage, and a reaction air circulation passage.

[0033] Specifically, the reaction air supply path includes: a first filter 101, which purifies the reaction air entering the oxidant supply unit; an oxidant driver 102, which provides driving force for the reaction air to enter, exit and circulate in the fuel cell; a first valve 103, which controls the opening of the reaction air inlet of the fuel cell; and a first temperature sensor 104, which collects the temperature of the reaction air at the fuel cell inlet.

[0034] Specifically, the reaction air emission path includes: a second valve 105, which controls the opening of the reaction air exhaust port of the fuel cell.

[0035] Specifically, the reaction air circulation path includes: a third valve 106, which controls the opening of the reaction air circulation path; and a first heater 107, which heats the reaction gas entering the reaction air circulation path.

[0036] The aforementioned reactive air supply path is connected to the atmosphere and a temperature control unit at its front end, and to the fuel cell reactive air inlet at its rear end. The aforementioned reactive air exhaust path is connected to the fuel cell 10 reactive air exhaust port at its front end, and to the atmosphere at its rear end. The aforementioned reactive air circulation path is connected to the fuel cell 10 reactive air exhaust port at its front end, and to the oxidant driver 102 at its rear end. The aforementioned reactive air supply path and reactive air exhaust path together constitute the reactive air exhaust path during fuel cell 10 power generation. The aforementioned reactive air supply path and reactive air circulation path together constitute the circulating air path during rapid preheating of fuel cell 10. The FDC90 controls the opening and closing of the first heater 107 based on the temperature collected by the first temperature sensor 104.

[0037] Specifically, when the temperature value T3 collected by the third temperature sensor 304 is less than the first temperature threshold, the atmospheric reaction air passes through the first filter 101 and enters the oxidant actuator 102 for pressurization. The first valve 103 and the third valve 106 are open, and the second valve 105 is closed. After entering the fuel cell 10, the reaction air is preheated by the first heater 107 and returns to the oxidant actuator 102 for pressurization. The reaction air circulates repeatedly in the above-mentioned path, forming an auxiliary heating cycle mode, which enables the fuel cell 10 to heat up rapidly. When the temperature value T3 collected by the third temperature sensor 304 is greater than or equal to the first temperature threshold, the atmospheric reaction air passes through the first filter 101 and enters the oxidant actuator 102 for pressurization. The first valve 103 and the second valve 105 are open, and the third valve 106 is closed. After entering the fuel cell 10, the reaction air is discharged after passing through the second valve 105, thus forming the reaction air discharge path when the fuel cell 10 generates electricity.

[0038] Figure 2 This is a control flowchart of the oxidant gas supply unit of an air-cooled fuel cell system as described in this application.

[0039] The FDC90 controls the opening degree of the first valve 103, the second valve 105 and the third valve 106 based on the temperature value T1 collected by the first temperature sensor 104.

[0040] Specifically, when the oxidant gas supply unit 100 is in auxiliary heating cycle mode, and the value T1 collected by the first temperature sensor 104 is less than the fourth temperature threshold, the first heater 107 is turned on to heat the circulating reaction air. When the value T1 collected by the first temperature sensor 104 is greater than or equal to the fourth temperature threshold, the first heater 107 is turned off to stop heating the circulating reaction air.

[0041] Specifically, when the oxidant gas supply unit 100 is in auxiliary heating cycle mode, the reaction air is heated by the first heater 107. Since the reaction air directly contacts the membrane electrode surface after entering the fuel cell 10, the temperature is transferred more directly, and the fuel cell 10 is preheated faster. In auxiliary heating cycle mode, no electrochemical reaction occurs in the fuel cell 10, and the oxygen in the reaction air is not consumed.

[0042] The temperature management unit 300 described above includes: a cooling air supply passage, a cooling air exhaust passage, a cooling air circulation passage, and a cooling air bypass.

[0043] Specifically, the cooling air supply path includes: a second filter 301, which purifies the cooling air entering the temperature management unit 300; a fourth valve 302, which controls the opening of the cooling air inlet of the fuel cell 10; and a second temperature sensor 303, which collects the temperature of the cooling air at the inlet of the fuel cell 10.

[0044] Specifically, the cooling air exhaust path includes: a third temperature sensor 304, which collects the temperature of the fuel cell 10; a coolant driver 305, which provides driving force for the cooling air to enter, exit and circulate in the fuel cell 10; and a thermostatic valve 306, which controls the opening ratio of the cooling air exhaust port of the fuel cell 10 toward two different paths, the two paths being connected to the atmospheric end and the front end of the cooling air circulation path, respectively.

[0045] Specifically, the cooling air circulation path includes a second heater 307, which heats the cooling gas entering the cooling air circulation path.

[0046] Specifically, the cooling air bypass includes: a fifth valve 308, which controls the opening degree of the fuel cell cooling air exhaust port connected to the front end of the reaction air supply passage.

[0047] The cooling air supply passage is connected to the atmosphere at its front end and to the cooling air inlet of the fuel cell 10 at its rear end. The cooling air exhaust passage is connected to the cooling air exhaust port of the fuel cell 10 at its front end and to both the atmosphere and the front end of the cooling air circulation passage at its rear end. The cooling air circulation passage is connected to the rear end of the cooling air exhaust passage at its front end and to the cooling air inlet of the fuel cell 10 at its rear end. The cooling air bypass is connected to the rear end of the coolant driver 305 at its front end and to the front end of the reaction air supply passage at its rear end.

[0048] The aforementioned cooling air supply passage and the aforementioned cooling air exhaust passage together constitute the cooling air exhaust passage during the power generation of the aforementioned fuel cell 10. The aforementioned cooling air supply passage, cooling air exhaust passage, and cooling air circulation passage together constitute the circulating air passage for the rapid preheating of the aforementioned fuel cell 10.

[0049] The FDC90 mentioned above controls the airflow direction and opening degree of the thermostatic valve 306 based on the temperature value T2 collected by the second temperature sensor 303. In this application, the thermostatic valve 306 is in the direction of connecting the end of the cooling air exhaust passage and the front end of the cooling air circulation passage, and the opening degree is 100%. The thermostatic valve 306 can be a thermostat, a reversing valve, a louver, etc.

[0050] Specifically, the cooling air in the atmosphere passes through the second filter 301 and the fourth valve 302, enters the cooling air inlet of the fuel cell 10, and after being pressurized by the coolant driver 305 from the cooling air outlet of the fuel cell 10, it is preheated by the second heater 307 and returns to the cooling air inlet of the fuel cell 10. The cooling air circulates repeatedly in the above-mentioned path, forming a cooling air circulation path.

[0051] Specifically, the auxiliary heating cycle mode is configured such that the fuel cell 10 is preheated by preheating the circulating reaction air with the first heater 107 and the circulating cooling air with the second heater 307. The mixed heating cycle mode is configured such that the fuel cell 10 is preheated by generating heat from electricity produced by the fuel cell 10 and the circulating cooling air with the second heater 307. The self-heating cycle mode is configured such that the fuel cell 10 is preheated by generating heat from electricity produced by the fuel cell 10 and the circulating cooling air with the second heater 307.

[0052] In addition, after a certain volume of cooling air enters the cooling air circulation path, closing the fourth valve 302 and the fifth valve 308 can reduce the amount of unheated cooling air entering the cooling air circulation path and improve the preheating efficiency of the fuel cell 10.

[0053] Figure 3 This is a flowchart illustrating the start-up control of an air-cooled fuel cell system as described in this application.

[0054] The FDC90 mentioned above controls the fuel cell system to switch between auxiliary heating cycle mode, mixed heating cycle mode and self-heating cycle mode based on the temperature value T3 collected by the third temperature sensor 304.

[0055] When the temperature value T3 collected by the third temperature sensor 304 is less than the first temperature threshold, the FDC90 executes the auxiliary heating cycle mode.

[0056] When the temperature value T3 collected by the third temperature sensor 304 is greater than or equal to the first temperature threshold and less than the second temperature threshold, the FDC90 executes the mixed heat cycle mode.

[0057] When the temperature value T3 collected by the third temperature sensor 304 is greater than or equal to the second temperature threshold and less than the third temperature threshold, the FDC90 executes the self-heating cycle mode.

[0058] When the temperature value T3 collected by the third temperature sensor 304 is greater than or equal to the third temperature threshold, FDC90 exits the loop mode.

[0059] The first temperature threshold can be set to -25℃, -15℃, -5℃, etc., with -15℃ being the preferred setting.

[0060] The second temperature threshold can be set to 0℃, 5℃, 10℃, etc., with 5℃ being the preferred setting.

[0061] The third temperature threshold can be set to 50℃, 55℃, 60℃, etc., with 55℃ being the preferred setting.

[0062] The fourth temperature threshold can be set to 50℃, 60℃, 70℃, etc., with 60℃ being the preferred setting.

[0063] The first valve 103, the second valve 105, the third valve 106, and the fifth valve 308 mentioned above can be throttle valves, solenoid valves, louvers, etc., and this application preferably uses throttle valves.

[0064] The aforementioned fourth valve 302 and thermostatic valve 30 can be a throttle valve, solenoid valve, reversing valve, louver, etc., and this application preferably uses a louver.

[0065] The first heater 107 and the second heater 307 mentioned above can be PTC modules, heating wire modules, etc., and this application preferably uses PTC modules.

[0066] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A cathode-enclosed air-cooled fuel cell system, characterized in that, include: The oxidant gas supply unit has the function of internally circulating and heating the reaction air to rapidly preheat the fuel cell; The temperature management unit has the function of internally circulating cooling air and heating it; The control and conversion unit (FDC) is used to control the oxidant gas supply unit and the temperature management unit.

2. The system according to claim 1, characterized in that, Under the premise of internal circulation, the temperature management unit forms an auxiliary heat circulation mode when heating is turned on, a hybrid circulation mode when heating and fuel cell power generation and heat generation are turned on simultaneously, and a self-heating circulation mode when fuel cell power generation and heat generation are turned on.

3. The system according to claim 1, characterized in that, The oxidant supply unit controls the circulation of reaction air through a first valve, a second valve, a third valve, and a reaction air actuator.

4. The system according to claim 1, characterized in that, The FDC controls the first heater to turn on and off based on the value collected by the first temperature sensor and the fourth temperature threshold, so as to control the temperature of the circulating reaction air to not exceed the fourth temperature threshold.

5. The system according to claim 1, characterized in that, The temperature control unit controls the internal circulation of cooling air through a temperature-regulating valve, a fourth valve, a fifth valve, and a cooling air actuator.

6. The system according to claim 1, characterized in that, The FDC controls the second heater and fuel cell to generate electricity based on the values ​​collected by the third temperature sensor, the first temperature threshold, the second temperature threshold, and the third temperature threshold, so as to control the switching between auxiliary heating cycle mode, hybrid cycle mode and self-heating cycle mode, and ensure efficient preheating of fuel cell.

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