Fuel cell air compressor energy recovery device

Abstract

The invention discloses a fuel cell air compressor energy recovery device. The fuel cell air compressor energy recovery device comprises a two-stage turbine mechanism, a controllable bypass mechanism, an energy storage mechanism and an air compressor, the two-stage turbine mechanism comprises a first turbine mechanism and a second turbine mechanism; the first turbine mechanism and the second turbine mechanism are respectively connected with a first generator and a second generator; the controllable bypass mechanism comprises a first tee joint, a second tee joint and a bypass electromagnetic valve and is used for controlling the path of air flowing through the turbine mechanism. The air compressor is connected with a humidifier, and the humidifier is sequentially connected with a first throttle valve, a fuel cell stack and a second throttle valve; the humidifier is connected with the first tee joint; and the energy storage mechanism is used for storing the recycled electric energy and supplying power to electric equipment. According to the device, efficient recovery of air compression energy under all working conditions is achieved, the energy utilization rate of the system is improved, the air pressure and flow can be independently controlled, and the energy storage mechanism is used for storing electric energy to supply power to electric equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen fuel cells, and in particular to an energy recovery device for a fuel cell air compressor. Background Art

[0002] Against the backdrop of rising global demand for renewable energy, fuel cells, with their significant advantages such as high power density, low operating temperature, and zero emissions, have become a highly anticipated research hotspot and development direction in the energy sector. Among these, proton exchange membrane fuel cells, which use hydrogen as fuel and efficiently convert chemical energy into electrical energy, stand out among many fuel cell types and are currently the most widely researched and applied. However, fuel cells cannot operate independently and must be constructed with a series of auxiliary components to form a complete fuel cell system that provides the stringent conditions required for the reaction, such as flow rate, pressure, temperature, and humidity. In a fuel cell system, the air compressor is the largest energy consumer. Especially under high current density conditions, the air needs to be pressurized to meet the reaction requirements, which significantly increases the energy consumption of the air compressor. Therefore, efficiently recovering the energy consumed by the air compressor has become a key technology for improving the energy efficiency of fuel cell systems.

[0003] Currently, several typical patent solutions exist in the prior art related to fuel cell air compressor energy recovery. Patent CN 103441291 B discloses an air supply system and energy recovery device for a fuel cell system. This system utilizes the energy-rich gas from the fuel cell stack reaction to drive the impeller, which in turn drives the high-speed motor, thereby saving the high-speed motor's electrical energy consumption. Patents CN 108590771 B and CN 109378503 B both disclose fuel cell air compressors with energy recovery devices. A power conversion device converts the pressurized gas energy generated by the fuel cell reaction unit into mechanical energy, which is then transmitted to the motor in the air compressor unit via a power transmission device, thereby reducing the motor's power requirements. Patent CN 115020758 B discloses a fuel cell system and cathode energy recovery control method that utilizes a turbine to power the air compressor, effectively reducing its power consumption. However, these patent solutions all directly convert compressed air energy into mechanical energy. While this improves the efficiency of the air supply system and energy recovery, the recovered energy is only used for the air compressor itself and cannot be converted into electrical energy for other auxiliary components.

[0004] Some other patents utilize turbine-driven generators for power generation, such as the fuel cell vehicle exhaust system energy recovery structure disclosed in patent CN 106945560 B and the fuel cell power generation system with exhaust gas energy recovery disclosed in patent CN 111261897 B. Both employ turbine-driven generators in the exhaust air line to generate electricity. These solutions have significant drawbacks. First, the turbine-driven generator structure is fixed, and its power generation efficiency has a specific high-efficiency range. When the air flow rate is too high or too low, the power generation efficiency decreases significantly. Second, the air-side flow resistance cannot be flexibly adjusted, resulting in the coupling of air pressure and flow, making independent control impossible. While the fuel cell energy recovery device and control method disclosed in patent CN 114198157 B achieves cascaded utilization of exhaust energy, it still fails to fully address these two drawbacks.

[0005] In summary, the current existing fuel cell air compressor energy recovery technologies have the following main shortcomings: First, most technologies directly convert compressed air energy into mechanical energy for the air compressor's rotation, which limits the scope of utilization of the recovered energy and is only used for the air compressor itself. It is unable to convert the stored energy into electrical energy to meet the power needs of other auxiliary components. This is because the existing technologies do not consider the further conversion and distribution of recovered energy in the design of the energy recovery path, which limits the application scenarios of the recovered energy and prevents its full value from being realized. Second, the technology that uses turbines to drive generators for power generation is limited by the fixed structure of the turbine mechanism, resulting in unstable power generation efficiency. In addition, the air-side flow resistance is not adjustable, resulting in the inability to independently control the air pressure and flow, making it difficult to meet the diverse operating requirements of the fuel cell system, such as the different requirements for flexible and independent adjustment of air pressure and flow under different current density and other operating conditions, as well as the adaptation requirements when switching between complex operating conditions in actual operation. Summary of the Invention

[0006] The present invention aims to provide a fuel cell air compressor energy recovery device to solve the problems of low system energy utilization caused by high power consumption of existing fuel cell air compressors and the inability to decouple air pressure and flow in traditional energy recovery methods.

[0007] A fuel cell air compressor energy recovery device in this solution includes a two-stage turbine mechanism, a controllable bypass mechanism, an energy storage mechanism and an air compressor;

[0008] The two-stage turbine mechanism includes a first turbine mechanism and a second turbine mechanism, wherein the first turbine mechanism and the second turbine mechanism are respectively connected to a first generator and a second generator;

[0009] The controllable bypass mechanism includes a first three-way valve, a second three-way valve and a bypass solenoid valve, and is used to control the path of air flowing through the turbine mechanism;

[0010] The air compressor is connected to a humidifier, which is sequentially connected to a first throttle valve, a fuel cell stack, and a second throttle valve; the humidifier is connected to a first three-way valve;

[0011] The energy storage mechanism is used to store the recovered electrical energy and supply power to electrical equipment.

[0012] The working principle and beneficial effects of this scheme are as follows: the two-stage turbine mechanism realizes efficient recovery under all working conditions. Under low-power and low-pressure working conditions, the second turbine mechanism is mainly used to recover energy; under high-power and high-pressure working conditions, the two turbine mechanisms work simultaneously to realize the cascade utilization of energy; the controllable bypass system realizes flexible control, and by adjusting the switching state of the bypass solenoid valve, the path of air flowing through the turbine mechanism is controlled to adapt to the energy recovery needs under different working conditions; the independent air compressor and the second throttle valve improve the flexibility of the system, and the air flow is controlled by the air compressor, and the air pressure is controlled by the second throttle valve to realize the decoupling control of pressure and flow; the energy storage mechanism stores the recovered energy into electrical energy and supplies power to electrical equipment; the air humidifier improves the efficiency of the system, and uses the heat and water vapor in the exhaust air to improve the state of the air entering the fuel cell stack and improve the performance of the fuel cell.

[0013] Furthermore, an air flow meter is connected to the air inlet of the air compressor. The air flow meter is used to measure the air flow entering the air compressor. The air compressor compresses the air and then outputs it to the humidifier.

[0014] Furthermore, a pressure sensor is connected to the pipeline between the first throttle valve and the fuel cell stack. The first throttle valve can adjust the opening and closing of the air passage and the flow rate, and the pressure sensor is used to detect the air pressure.

[0015] Furthermore, the energy storage mechanism includes a first power converter and a second power converter, the first power converter and the second power converter being connected to the first generator and the second generator, respectively, and the first power converter and the second power converter being connected to a battery. The first power converter converts the AC power generated by the first generator into DC power and charges the battery, while the second power converter converts the AC power generated by the second generator into DC power and charges the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a structural schematic diagram of a fuel cell air compressor energy recovery device of the present invention. DETAILED DESCRIPTION

[0017] The following is a further detailed description through specific implementation methods:

[0018] The figure marks in the drawings of the specification include: fuel cell stack 1, air flow meter 2, air compressor 3, humidifier 4, first throttle valve 5, pressure sensor 6, second throttle valve 7, first three-way valve 8, first turbine mechanism 9, second three-way valve 10, bypass solenoid valve 11, second turbine mechanism 12, first generator 13, second generator 14, first power converter 15, second power converter 16, battery 17.

[0019] The embodiment is basically as shown in the attached Figure 1 As shown: A fuel cell air compressor energy recovery device includes a two-stage turbine mechanism, a controllable bypass mechanism, an energy storage mechanism and an air compressor 3;

[0020] The two-stage turbine mechanism includes a first turbine mechanism 9 and a second turbine mechanism 12, and the first turbine mechanism 9 and the second turbine mechanism 12 are connected to a first generator 13 and a second generator 14 respectively;

[0021] The air inlet of the air compressor 3 is connected to an air flow meter 2, and the air outlet of the air compressor 3 is connected to a humidifier 4. After the humidifier 4, the first throttle valve 5, the pressure sensor 6 and the fuel cell stack 1 are connected in sequence. The second throttle valve 7 is connected between the fuel cell stack 1 and the humidifier 4. The humidifier 4, the first throttle valve 5, the fuel cell stack 1 and the second throttle valve 7 form a loop.

[0022] The air compressor 3 is a key component of the air supply system. Its function is to pressurize the air in the surrounding environment and deliver it to the fuel cell stack 1. In conventional fuel cell systems, the air compressor 3 consumes a large amount of energy to compress the air. However, the compressed air after the reaction is directly discharged, causing energy to be dissipated into the environment in the form of eddy currents, resulting in low energy utilization.

[0023] Humidifier 4 provides a place for heat and material exchange between the air entering the stack and the exhaust gas leaving the stack. The exhaust gas from the fuel cell stack 1 carries a large amount of heat and water vapor. Through the diaphragm inside the humidifier 4, this heat and water are transferred to the air entering the air compressor 3. On the one hand, this increases the humidity of the air entering the stack, thereby improving fuel cell performance; on the other hand, it adjusts the temperature of the air entering the stack to be closer to the stack temperature, effectively preventing flooding or membrane drying.

[0024] The first throttle valve 5 is a butterfly valve with adjustable opening. When the fuel cell is operating normally, the first throttle valve 5 is fully open, allowing air to pass through smoothly. After the fuel cell is shut down, the first throttle valve 5 is fully closed. Its main function is to isolate the cathode chamber of the fuel cell stack 1 from the ambient air and prevent pollutants from entering.

[0025] Pressure sensor 6 measures the air pressure entering the fuel cell stack. The fuel cell's air pressure setpoint is determined by the stack's output current. Generally, the higher the stack current, the faster the gas consumption rate, and the higher the required air pressure. The actual pressure measured by pressure sensor 6 is transmitted as feedback to the fuel cell controller. The controller adjusts the opening of the second throttle valve 7 to change the air line flow resistance, bringing the measured air pressure closer to the setpoint.

[0026] The second throttle valve 7 is also a butterfly valve with adjustable opening. During normal operation of the fuel cell, the second throttle valve 7 adjusts its opening in real time based on the air pressure set value and feedback value. After the fuel cell is shut down, the second throttle valve 7 is fully closed, isolating the cathode chamber of the fuel cell stack 1 from the ambient air.

[0027] The fuel cell stack 1 is the core energy conversion device, responsible for converting hydrogen oxidized chemical energy into electrical energy. Its peripheral auxiliary systems include the hydrogen supply system, air supply system, and thermal management system. This invention primarily improves the air supply system, so other subsystems are omitted in the system diagram. During high-power operation, the rate of hydrogen and oxygen consumption accelerates. To improve battery performance, pressurization of the cathode and anode reactant gases is typically required.

[0028] The humidifier 4 is connected to a controllable bypass mechanism, which includes a first three-way valve 8, a second three-way valve 10 and a bypass solenoid valve 11. The first three-way valve 8 is located on the air inlet side of the first turbine mechanism 9, and the second three-way valve 10 is located on the air outlet side of the first turbine mechanism 9. The bypass solenoid valve 11 is used to control the on-off of the second three-way valve 10, and the second three-way valve 10 is connected to the air inlet side of the second turbine mechanism 12;

[0029] The first tee 8 is located on the air inlet side of the first turbine mechanism 9, providing a bypass channel for it. The first turbine mechanism 9 can use the compressed air energy to drive the turbine mechanism blades to rotate, thereby driving the first generator 13 to rotate and generate electricity. Compared with the second turbine mechanism 12, the first turbine mechanism 9 has a larger rated power and pressure drop, which is suitable for high-power and high-pressure conditions of fuel cells; for example, the rated power is greater than 30kw and the operating pressure is greater than 30kPa.

[0030] The second three-way valve 10 is located on the outlet side of the first turbine mechanism 9 and also provides a bypass for it. The bypass solenoid valve 11 is used to control the on and off of the bypass of the first turbine mechanism 9. Under the low-power and low-pressure working conditions of the fuel cell (rated power is less than 30kW, operating pressure is less than 30kPa), the bypass solenoid valve 11 is opened, and most of the tail exhaust air directly enters the second turbine mechanism 12 through the bypass. At this time, the air pressure drop is small, and the low-pressure and small-flow air drives the second turbine mechanism 12 to generate electricity; under the high-power and high-pressure working conditions of the fuel cell (rated power is greater than 30kW, operating pressure is greater than 30kPa), the bypass solenoid valve 11 is closed, and the tail exhaust air flows through the first turbine mechanism 9 and the second turbine mechanism 12 in turn. The gas pressure drop is large, and the two turbine mechanisms simultaneously drive their respective generators to generate electricity;

[0031] The second turbine mechanism 12 also utilizes air compression energy to rotate its blades, driving the second generator 14 to generate electricity. Compared with the first turbine mechanism 9, the second turbine mechanism 12 has a lower rated power and pressure drop, making it suitable for low-power and low-pressure operating conditions of fuel cells.

[0032] The energy storage mechanism includes a first power converter 15 and a second power converter 16 , the first power converter 15 and the second power converter 16 are connected to the first generator 13 and the second generator 14 respectively, and the first power converter 15 and the second power converter 16 are connected to a battery 17 ;

[0033] The first power converter 15 converts the AC power generated by the first generator 13 into DC power and charges the battery 17. The second power converter 16 converts the AC power generated by the second generator 14 into DC power and also charges the battery 17. The battery 17 is used to store the electrical energy generated by the first generator 13 and the second generator 14 and to supply power to electrical devices.

[0034] When the fuel cell is in shutdown mode, the first throttle valve 5 and the second throttle valve 7 are both in a closed state. At this time, the cathode chamber of the fuel cell stack 1 is isolated from the air, and pollutants in the surrounding environment cannot enter the fuel cell stack 1 through the air pipe to cause pollution;

[0035] When the fuel cell is in working condition, the first throttle valve 5 is fully open, allowing air to pass through. The fuel cell controller automatically calculates and adjusts the speed of the air compressor 3 according to the set value and feedback value of the air flow in the air flow meter 2. The fuel cell controller automatically calculates and continuously adjusts the opening of the second throttle valve 7 according to the set value and feedback value of the air pressure in the pressure sensor 6, and realizes independent control of the air flow and pressure through the two actuators of the air compressor 3 and the second throttle valve 7. When the fuel cell is in working condition, its output power changes with the load demand. Pressurizing the fuel cell at low current density has little effect on the performance improvement, but pressurizing at high current density has a significant performance improvement. Therefore, the operating pressure of the fuel cell usually increases with the increase of current or power.

[0036] Under the low-power operation condition of the fuel cell, the set air flow and set air pressure of the fuel cell stack 1 are both small, the power generation efficiency of the first turbine mechanism 9 is low, and the power generation efficiency of the second turbine mechanism 12 is high. In addition, enabling the first turbine mechanism 9 will increase the flow resistance and pressure drop of the air tail pipe, thereby increasing the operating pressure of the fuel cell. Therefore, the bypass solenoid valve 11 is opened at low power to reduce the flow resistance at the front end of the second turbine mechanism 12, allowing the air to drive the second turbine mechanism 12 to rotate, and the second turbine mechanism 12 drives the second generator 14 to rotate to generate AC power. The second power converter 16 converts the AC power into DC power and charges the battery 17. Under high-power fuel cell operation, the set air flow and set air pressure of the fuel cell stack 1 are both relatively high. The power generation efficiency of the first turbine mechanism 9 is relatively high, while the power generation efficiency of the second turbine mechanism 12 is relatively low. Activating the first turbine mechanism 9 increases the flow resistance and pressure drop of the exhaust air pipeline, fully utilizing the compression energy of the stack exhaust air. Therefore, at high power, the bypass solenoid valve 11 is closed, allowing air to pass through the first and second turbine mechanisms 9, 12 in sequence. The first turbine mechanism 9 drives the first generator 13 to generate AC power, which the first power converter 15 converts into DC power and charges the battery 17. The air discharged from the first turbine mechanism 9 experiences a significant pressure drop, recovering most of the compression energy. The lower-pressure compressed air then enters the second turbine mechanism 12 and drives the second generator 14 to generate electricity, further recovering excess energy and improving energy utilization. The compression energy in the exhaust air is ultimately converted into chemical energy and stored in the battery 17. This energy can be used to power auxiliary units of the air supply system, other auxiliary components, or external devices.

[0037] Efficient Energy Recovery: A two-stage turbine mechanism and generator design—the first turbine mechanism 9 and the second turbine mechanism 12, respectively adapted for the fuel cell's high-power, high-pressure operating conditions and low-power, low-pressure operating conditions—enables efficient recovery of compressed air energy under both high- and low-power conditions, significantly improving system energy utilization. Under varying operating conditions, the exhaust air's energy can be fully utilized for power generation, providing more comprehensive energy recovery than existing technologies.

[0038] Independent control: Using two actuators, air compressor 3 and throttle valves (first throttle valve 5 and second throttle valve 7), independent control of air pressure and flow is achieved. The fuel cell controller can precisely adjust the air flow and pressure according to the stack's needs, avoiding the coupling of air pressure and flow, and improving the stability and reliability of the fuel cell system.

[0039] Performance improvement: The air humidifier 4 is used to effectively recover the heat and water vapor in the tail exhaust air and transfer it to the air entering the fuel cell stack, which not only increases the air humidity but also regulates the air temperature, improves the fuel cell stack performance, reduces the occurrence of problems such as flooding and membrane drying, and extends the service life of the fuel cell.

[0040] Energy storage and sharing: Through the energy storage battery 17, the compressed air recovery energy is stored and energy is supplied to other auxiliary components or external components, which broadens the scope of energy utilization and improves the comprehensive energy utilization efficiency of the entire fuel cell system.

[0041] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A fuel cell air compressor energy recovery device, characterized by: The invention comprises a two-stage turbine mechanism, a controllable bypass mechanism, an energy storage mechanism and an air compressor; the two-stage turbine mechanism comprises a first turbine mechanism and a second turbine mechanism, the first turbine mechanism and the second turbine mechanism being connected to a first generator and a second generator respectively; the controllable bypass mechanism is used to control the path of air flowing through the turbine mechanism, and the controllable bypass mechanism comprises a first three-way valve, a second three-way valve and a bypass solenoid valve connected in sequence; The air compressor is connected to a humidifier, which is sequentially connected to a first throttle, a fuel cell stack, and a second throttle; the humidifier is connected to a first three-way valve; the energy storage mechanism is used to store the electrical energy generated by the first generator and the second generator and supply power to electrical equipment.

2. The fuel cell air compressor energy recovery device according to claim 1, characterized in that: The air inlet end of the air compressor is connected to an air flow meter.

3. The fuel cell air compressor energy recovery device according to claim 2, characterized in that: A pressure sensor is connected to the pipeline between the first throttle valve and the fuel cell stack.

4. The fuel cell air compressor energy recovery device according to claim 3, characterized in that: The energy storage mechanism includes a first power converter and a second power converter. The first power converter and the second power converter are connected to the first generator and the second generator respectively. The first power converter and the second power converter are connected to batteries.

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