Fuel cell system

Abstract

Provided is a fuel cell system capable of maintaining the output of the fuel cell system. The fuel cell system is provided with a fuel cell stack, a cooling flow path, a radiator, a bypass flow path, a switching valve for switching the flow of cooling water to the radiator or to the bypass flow path, a power source for supplying power to the switching valve, a voltmeter for measuring the voltage of the power source, and a secondary battery. When the voltage of the power supply measured by the voltmeter is equal to or greater than a predetermined voltage, the upper limit of the output from the secondary battery is set as a first output, and when the voltage of the power supply is less than the predetermined voltage, the upper limit of the output from the secondary battery is set as a second output greater than the first output.

Description

Technical Field

[0001] The present disclosure relates to fuel cell systems. Background Art

[0002] Various technologies have been proposed regarding fuel cells (FC) such as those disclosed in Patent Documents 1 and 2.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2009-170378

[0004] Patent Document 2: Japanese Patent Application Publication No. 2008-130424

[0005] In the prior art, in order to control the cooling water temperature of the fuel cell, the fuel cell water temperature is controlled in a circuit using a water pump and a switching valve. In the fuel cell system, the motor torque of the cooling water switching valve varies according to the power supply voltage. Therefore, when the power supply voltage decreases, the motor torque cannot be fully output, and the responsiveness of the switching valve decreases. Due to the decrease in the responsiveness of the switching valve, the output of the fuel cell decreases, and the output of the fuel cell system decreases. Summary of the invention

[0006] The present disclosure has been made in view of the above-mentioned actual situation, and its main object is to provide a fuel cell system capable of maintaining the output of the fuel cell system.

[0007] In a first embodiment of the present disclosure, a fuel cell system is provided, wherein the fuel cell system comprises: a fuel cell stack; a cooling flow path for circulating cooling water for cooling the fuel cell stack inside and outside the fuel cell stack; a radiator disposed on the cooling flow path; a bypass flow path for branching from the cooling flow path at a position upstream of the radiator, bypassing the radiator, and merging with the cooling flow path at a position downstream of the radiator; a switching valve disposed at a branch point of the cooling flow path with the bypass flow path for switching the cooling water discharged from the fuel cell stack to flow to the radiator or to flow to the bypass flow path; a power supply for supplying power to the switching valve; a voltmeter for measuring the voltage of the power supply; and a secondary battery, wherein when the voltage of the power supply measured by the voltmeter is greater than a specified voltage, the upper limit of the output from the secondary battery is set to a first output, and when the voltage of the power supply is less than the specified voltage, the upper limit of the output from the secondary battery is set to a second output greater than the first output.

[0008] In the second embodiment of the present disclosure, it can also be constructed as follows: on the basis of the first embodiment, the response time of the above-mentioned switching valve is estimated based on the voltage of the above-mentioned power supply measured by the above-mentioned voltmeter, and the temperature of the above-mentioned cooling water flowing into the above-mentioned fuel cell group is estimated based on the above-mentioned response time. When the estimated temperature of the above-mentioned cooling water is below the specified temperature, the upper limit of the output from the above-mentioned secondary battery is set to the above-mentioned second output.

[0009] The fuel cell system of the present disclosure is capable of maintaining the output of the fuel cell system. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a graph showing an example of the relationship among the pulse rate, the driving torque, and the power supply voltage.

[0011] Figure 2 This is a diagram showing an example of the ratio of the output of the fuel cell to the output of the secondary battery when the power supply voltage is high and the ratio of the output of the fuel cell to the output of the secondary battery when the power supply voltage is low.

[0012] Figure 3 1 is a system configuration diagram showing an example of a fuel cell system of the present disclosure.

[0013] Figure 4 1 is a flowchart showing an example of control of the fuel cell system of the present disclosure.

[0014] Description of Reference Numerals

[0015] 10…fuel cell stack; 50…cooling system; 51…cooling flow path; 52…radiator; 53…bypass flow path; 54…switching valve; 55…storage tank; 56…cooling water pump; 57…ion exchanger; 58…intercooler; T…temperature sensor. DETAILED DESCRIPTION

[0016] The following describes the embodiments of the present disclosure. In addition, matters required for the implementation of the present disclosure other than matters specifically mentioned in this specification (for example, the general structure and manufacturing process of the fuel cell system that does not characterize the present disclosure) can be understood as design matters based on the prior art by those skilled in the art in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field.

[0017] In addition, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships.

[0018] In the present disclosure, the gas supplied to the anode of the fuel cell is the fuel gas (anode gas), and the gas supplied to the cathode of the fuel cell is the oxidant gas (cathode gas). The fuel gas is a gas mainly containing hydrogen, and may also be hydrogen. The oxidant gas is a gas containing oxygen, and may also be oxygen, air, etc.

[0019] In the present disclosure, a fuel cell system is provided, the fuel cell system comprising: a fuel cell stack; a cooling flow path for circulating cooling water for cooling the fuel cell stack inside and outside the fuel cell stack; a radiator disposed on the cooling flow path; a bypass flow path for branching from the cooling flow path at a position upstream of the radiator, bypassing the radiator, and merging with the cooling flow path at a position downstream of the radiator; a switching valve disposed at a branch point of the cooling flow path with the bypass flow path for switching the cooling water discharged from the fuel cell stack to flow to the radiator or to flow to the bypass flow path; a power supply for supplying power to the switching valve; a voltmeter for measuring the voltage of the power supply; and a secondary battery, when the voltage of the power supply measured by the voltmeter is greater than a specified voltage, the upper limit of the output from the secondary battery is set to a first output, and when the voltage of the power supply is less than the specified voltage, the upper limit of the output from the secondary battery is set to a second output greater than the first output.

[0020] Figure 1 This is a graph showing an example of the relationship among the pulse rate, the driving torque, and the power supply voltage.

[0021] In a fuel cell system, Figure 1 As shown in FIG. 1 , the motor torque (driving torque) of the cooling water switching valve varies according to the power supply voltage. Therefore, when the power supply voltage decreases, the motor torque cannot be fully output, the pulse rate of the cooling water switching valve decreases, and the responsiveness decreases. If the responsiveness of the switching valve decreases, the switching of the cooling water from the radiator side to the bypass flow path side that bypasses the radiator becomes slower, and the temperature rise of the cooling water becomes slower than before the responsiveness decreases. As a result, the temperature of the cooling water flowing into the fuel cell decreases, the inlet water temperature and the outlet water temperature of the fuel cell become lower, and the output of the fuel cell decreases when a mobile body such as a vehicle is accelerated.

[0022] Figure 2 This is a diagram showing an example of the ratio of the output of the fuel cell to the output of the secondary battery when the power supply voltage is high and the ratio of the output of the fuel cell to the output of the secondary battery when the power supply voltage is low.

[0023] In the present disclosure, when the voltage of the power source supplying electric power to the switching valve is less than the specified voltage, a larger output than usual is supplied from the secondary battery (Bat), thereby compensating for the reduced output of the fuel cell, thereby maintaining the output of the entire system and obtaining the specified system output, and normally suppressing the output from the secondary battery to a lower level to suppress the degradation of the secondary battery.

[0024] The fuel cell system of the present disclosure may be mounted on a mobile object such as a vehicle for use. In addition, the fuel cell system of the present disclosure may be mounted on a fixed power generation system such as a generator that supplies power to the outside of the fuel cell system for use.

[0025] The vehicle may be a fuel cell vehicle, etc. Examples of mobile bodies other than vehicles include trains, ships, and airplanes.

[0026] Furthermore, the fuel cell system of the present disclosure may be mounted on and used in a mobile object such as a vehicle that can be driven by the electric power of the secondary battery.

[0027] A mobile object or a fixed power generation system may also include the fuel cell system of the present disclosure.

[0028] The mobile object may include a drive unit such as a motor, an inverter, and a hybrid control system.

[0029] The hybrid control system may be a system that causes a moving object to travel by using the output of a fuel cell and the electric power of a secondary battery together.

[0030] The fuel cell system comprises: a fuel cell, in which hydrogen and oxygen react to generate electricity; a fuel gas system, which supplies a fuel gas containing hydrogen required for the power generation of the above-mentioned fuel cell to the fuel cell; an oxidant gas system, which supplies an oxidant gas containing oxygen to the above-mentioned fuel cell; and a cooling system, etc., which supplies cooling water to the above-mentioned fuel cell to cool the heat generated by the power generation.

[0031] The fuel cell may be a single cell (battery cell) having only one fuel cell, or may be a stacked body (battery stack) in which a plurality of cells are stacked.

[0032] In the present disclosure, there are cases where both a battery cell and a fuel cell stack are referred to as a fuel cell.

[0033] The number of stacked cells in the fuel cell stack is not particularly limited, and may be, for example, 2 to several hundred.

[0034] The fuel cell stack may have a current collecting plate, a pressure plate, etc. at the end portions in the stacking direction.

[0035] The battery cell may have a power generation unit.

[0036] In a plan view, the shape of the power generation unit may be a rectangle.

[0037] The power generation unit may be a membrane electrode assembly (MEA) including an electrolyte membrane and two electrodes.

[0038] The electrolyte membrane may also be a solid polymer electrolyte membrane. As the solid polymer electrolyte membrane, for example, a fluorine electrolyte membrane such as a film of perfluorosulfonic acid containing water, and a hydrocarbon electrolyte membrane may be cited. As the electrolyte membrane, for example, a Nafion membrane (manufactured by DuPont) may also be used.

[0039] One of the two electrodes is the anode (fuel electrode) and the other is the cathode (oxidant electrode).

[0040] The electrode includes a catalyst layer and may include a gas diffusion layer as necessary, and the power generation unit may be a membrane electrode gas diffusion layer assembly (MEGA).

[0041] The catalyst layer may include a catalyst including a catalyst metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, and a carrier having electron conductivity.

[0042] As the catalyst metal, for example, platinum (Pt) and alloys composed of Pt and other metals (for example, Pt alloys mixed with cobalt and nickel, etc.) can be used. The catalyst metal used as the cathode catalyst and the catalyst metal used as the anode catalyst may be the same or different.

[0043] The electrolyte may be a fluorine-based resin or the like. For example, a Nafion solution or the like may be used as the fluorine-based resin.

[0044] The above-mentioned catalyst metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalyst metal (catalyst-supporting carrier) and the electrolyte may be present in a mixed state.

[0045] Examples of the carrier for supporting the catalyst metal include carbon materials such as generally available carbon.

[0046] The gas diffusion layer may be a conductive member having pores or the like.

[0047] Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous members such as metal mesh and foamed metal.

[0048] The cells of the fuel cell may also include a membrane.

[0049] The diaphragm collects the current generated by power generation and functions as a partition. In the battery cell of the fuel cell, the diaphragm is usually arranged on both sides of the stacking direction of the power generation part in a way that a pair of diaphragms sandwich the power generation part. One side of the pair of diaphragms is the anode diaphragm and the other side is the cathode diaphragm.

[0050] The anode separator may have grooves serving as fuel gas flow paths on the surface on the power generation unit side.

[0051] The cathode separator may have grooves serving as oxidant gas flow paths on the surface on the power generation unit side.

[0052] The separator may have holes constituting a manifold such as a supply hole and a discharge hole for allowing the fluid to flow in the stacking direction of the battery cells.

[0053] The separator may be, for example, dense carbon obtained by compressing carbon to be airtight, or press-formed metal (for example, iron, titanium, stainless steel, etc.).

[0054] The battery cell may also include an insulating resin frame disposed on the outside (periphery) of the surface direction of the membrane electrode assembly between the anode separator and the cathode separator. The resin frame is formed in a plate-shaped and frame-shaped manner using a thermoplastic resin, and the anode separator and the cathode separator are sealed in a state where the membrane electrode assembly is maintained in its central area. As the resin frame, for example, resins such as PE, PP, PET, and PEN can be used. The resin frame may also be a three-layer sheet consisting of three layers with an adhesive layer disposed on the surface.

[0055] The fuel cell system may include a control device. The control device may control the oxidant gas system, the fuel gas system, the cooling system, etc. to control the entire fuel cell system.

[0056] Physically, the control device has, for example, a processing unit such as a CPU (central processing unit), a ROM (read-only memory) for storing control programs and control data processed by the CPU, a storage device such as a RAM (random access memory) mainly used as various work areas for control processing, and an input / output interface, and may also be an ECU (electronic control unit), etc.

[0057] The cooling system supplies cooling water as a cooling medium to the fuel cell.

[0058] Examples of the cooling water include water and ethylene glycol, and a mixed liquid thereof may be used.

[0059] The cooling system includes a cooling flow path, a radiator, a bypass flow path, a switching valve, and may also include a storage tank, a cooling water pump, an ion exchanger, an intercooler, a temperature sensor, etc. as needed.

[0060] The cooling flow path is a flow path that circulates cooling water for cooling the fuel cell stack inside and outside the fuel cell stack.

[0061] The radiator is arranged on the cooling flow path.

[0062] The bypass flow path branches off from the cooling flow path at a position upstream of the radiator, bypasses the radiator, and merges with the cooling flow path at a position downstream of the radiator.

[0063] The switching valve is disposed at a branch point between the cooling flow path and the bypass flow path, and switches the flow path so that the cooling water discharged from the fuel cell stack flows to the radiator or to the bypass flow path. The switching valve may also include an electric motor such as an electric actuator for switching the flow path.

[0064] The cooling water pump adjusts the flow rate of cooling water supplied to the fuel cell.

[0065] The fuel cell system includes a power source, which supplies electric power to the switching valve.

[0066] The fuel cell system includes a voltmeter. The voltmeter measures the voltage of the power supply.

[0067] The fuel cell system includes a secondary battery.

[0068] As long as the secondary battery can be charged and discharged, for example, a nickel-metal hydride secondary battery, a lithium-ion secondary battery and other previously known secondary batteries can be cited. In addition, the secondary battery may also include a storage element such as a double-layer capacitor. The secondary battery may also be a structure in which a plurality of batteries are connected in series. The secondary battery supplies power to a power supply, an air compressor and the like. For example, the secondary battery may also be charged from a power supply external to the fuel cell system such as a household power supply. The secondary battery may also be charged by the output of the fuel cell. The charging and discharging of the secondary battery may also be controlled by a control device.

[0069] When the voltage of the power supply measured by the voltmeter is above the specified voltage, the fuel cell system sets the upper limit of the output from the secondary battery to the first output. On the other hand, when the voltage of the power supply measured by the voltmeter is less than the specified voltage, the fuel cell system sets the upper limit of the output from the secondary battery to the second output that is greater than the first output. The first output and the second output are not particularly limited as long as the second output is greater than the first output, and can be appropriately set in consideration of the maximum output of the secondary battery, the maximum output of the fuel cell, etc.

[0070] The fuel cell system may also estimate the response time of the switching valve based on the voltage of the power supply measured by the voltmeter. If the voltage of the power supply decreases, the response time of the switching valve becomes longer. Therefore, the fuel cell system may also be configured to prepare a data group indicating the relationship between the voltage of the power supply and the response time of the switching valve in advance, and estimate the response time of the switching valve by comparing the voltage of the power supply measured by the voltmeter with the data group.

[0071] The fuel cell system may also estimate the temperature of the cooling water flowing into the fuel cell stack based on the estimated response time of the switching valve. If the response time of the switching valve becomes longer, the switching of the cooling water from the radiator side to the bypass flow path side that bypasses the radiator becomes slower, and the temperature rise of the cooling water becomes slower compared to before the response time becomes longer (the responsiveness becomes lower). As a result, the temperature of the cooling water flowing into the fuel cell stack decreases, the inlet water temperature and the outlet water temperature of the fuel cell stack become lower, and the output of the fuel cell stack decreases. Therefore, the fuel cell system may also be configured as follows: a data group representing the relationship between the response time of the switching valve and the temperature of the cooling water flowing into the fuel cell stack is prepared in advance, and the estimated response time of the switching valve is compared with the data group to estimate the temperature of the cooling water flowing into the fuel cell stack.

[0072] The fuel cell system may be configured such that when the estimated temperature of the cooling water is equal to or lower than a predetermined temperature, the fuel cell stack output is regarded as being reduced and the upper limit of the output from the secondary battery is set to the second output.

[0073] In the present disclosure, the output assistance in the secondary battery can be performed more accurately without adding a temperature sensor by using the water temperature of the cooling water based on the determination of whether the output assistance in the secondary battery is required.

[0074] The oxidant gas system supplies oxidant gas to the fuel cell and adjusts the flow rate of the oxidant gas. The oxidant gas system may include an oxidant gas supply mechanism, oxidant gas piping, an inlet-side sealing valve at the oxidant gas inlet of the fuel cell, and an outlet-side sealing valve at the oxidant gas outlet of the fuel cell.

[0075] The oxidant gas supply mechanism may be an air compressor or the like.

[0076] The fuel gas system supplies fuel gas to the fuel cell and adjusts the flow rate of the fuel gas.

[0077] The fuel gas system may also include a fuel gas tank, a fuel gas inlet valve, an injector, a gas-liquid separator, a fuel gas purification valve, an ejector for fuel gas circulation, a fuel gas pump for fuel gas circulation, and fuel gas piping.

[0078] Figure 31 is a system configuration diagram showing an example of a fuel cell system of the present disclosure.

[0079] Figure 3 The fuel cell system shown in the figure includes a fuel cell stack 10, a cooling system 50, and a temperature sensor T. Although not shown in the figure, the fuel cell system includes a power supply, a voltmeter, a secondary battery, an oxidant gas system, and a fuel gas system. The cooling system 50 includes a cooling flow path 51, a radiator 52, a bypass flow path 53, a switching valve 54, a storage tank 55, a cooling water pump 56, an ion exchanger 57, and an intercooler 58.

[0080] Figure 4 1 is a flowchart showing an example of control of the fuel cell system of the present disclosure.

[0081] The operation of the fuel cell system is started, and it is determined whether the supply voltage V from the power supply is equal to or higher than a predetermined voltage threshold value Vc.

[0082] When the supply voltage from the power source is equal to or higher than Vc, the output Wout from the secondary battery is set to the output upper limit Wlow.

[0083] On the other hand, when the supply voltage from the power source is less than Vc, the output Wout from the secondary battery is set to an output upper limit Wup greater than the output upper limit Wlow, and when the supply voltage from the power source is low, the output from the secondary battery is increased.

[0084] The fuel cell system may continue to check the power supply voltage V at a predetermined cycle until the operation is stopped, or the control may be terminated when the operation is stopped.

Claims

1. A fuel cell system, wherein: The fuel cell system comprises: Fuel cell stack; A cooling flow path, so that cooling water for cooling the fuel cell stack circulates inside and outside the fuel cell stack; A radiator, arranged on the cooling flow path; a bypass flow path that branches from the cooling flow path at a position upstream of the radiator, bypasses the radiator, and merges with the cooling flow path at a position downstream of the radiator; a switching valve disposed at a branch point between the cooling flow path and the bypass flow path, and switching the cooling water discharged from the fuel cell stack to flow to the radiator or to flow to the bypass flow path; a power source for supplying power to the switching valve; a voltmeter, for measuring the voltage of the power supply; as well as Secondary batteries, When the voltage of the power supply measured by the voltmeter is greater than a specified voltage, the upper limit of the output from the secondary battery is set to a first output. When the voltage of the power supply is less than the specified voltage, the upper limit of the output from the secondary battery is set to a second output greater than the first output.

2. The fuel cell system according to claim 1, wherein: estimating a response time of the switching valve based on the voltage of the power supply measured by the voltmeter, estimating the temperature of the cooling water flowing into the fuel cell stack based on the response time, When the estimated temperature of the cooling water is equal to or lower than a predetermined temperature, an upper limit of the output from the secondary battery is set to the second output.

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