Fuel cell system

Abstract

The invention provides a fuel cell system capable of improving efficiency. The fuel cell system is provided with a fuel cell, a cooling system provided with a cooling water pump and a storage tank, and a control device that performs temperature rise control for raising the temperature of the cooling water to a target temperature when the temperature of the cooling water is equal to or less than a low temperature determination threshold value. The control device cools the temperature of the cooling water to a normal use temperature lower than a target temperature after the temperature rise control, and the target temperature is set on the basis of at least one of the withstand pressure of the cooling system and the operating pressure of the storage tank.

Description

Technical Field

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

[0002] Regarding fuel cells (FCs) disclosed in Patent Documents 1 and 2, various techniques have been proposed.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-150018

[0004] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-296326

[0005] In Patent Document 1, a fuel cell system is disclosed. The fuel cell system is configured to calculate an upper limit flow rate of cooling water based on the opening degree of a three-way valve, calculate a target flow rate of cooling water corresponding to the power generation amount of the fuel cell, and drive a cooling water pump (W / P) based on these calculation results, thereby controlling within the pressure resistance of the cooling system.

[0006] It is necessary to control the flow rate of cooling water so as not to exceed the pressure resistance of the cooling system. As a result, since the cooling water does not flow at the desired flow rate, it is necessary to suppress the power generation amount of the fuel cell, and there may be a situation where the required power of the fuel cell system cannot be responded to.

[0007] If the pressure resistance of the cooling system is increased, cost increases and the size becomes larger, and the design freedom on the user side is also reduced.

[0008] In the case of not increasing the pressure resistance of the cooling system, in order to maintain the desired power generation amount of the fuel cell, it is necessary to make the pressures of the fuel gas system and the oxidant gas system higher than the cooling system, and thus it is necessary to excessively supply reaction gases to the fuel cell. As a result, the efficiency of the fuel cell system is reduced. Summary of the Invention

[0009] The present disclosure has been made in view of the above actual situation, and its main object is to provide a fuel cell system capable of improving efficiency.

[0010] That is, the present disclosure includes the following aspects.

[0011] <1> A fuel cell system, wherein the fuel cell system includes a fuel cell, a cooling system, and a control device. The cooling system includes a cooling water pump and a storage tank. When the temperature of the cooling water is below a low temperature determination threshold, the control device performs temperature increase control to raise the temperature of the cooling water to a target temperature. After the temperature increase control, the control device cools the temperature of the cooling water to a normal use temperature lower than the target temperature. The target temperature is set based on at least any one of the pressure resistance of the cooling system and the operating pressure of the storage tank.

[0012] <2> The fuel cell system according to <1>, wherein the control device monitors a temperature history of the cooling water, and when the temperature history becomes equal to or lower than the low temperature determination threshold, the control device performs the heating control.

[0013] The fuel cell system of the present disclosure can improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a graph showing the relationship between the temperature of the cooling water and the pressure in the cooling system.

[0015] Figure 2 It is a flowchart showing an example of the control of the fuel cell system of the present disclosure.

[0016] Figure 3 It is a flowchart showing another example of the control of the fuel cell system of the present disclosure. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present disclosure will be described. In addition, matters required for implementing the present disclosure other than those specifically mentioned in this specification (for example, general structures and manufacturing processes of fuel cell systems that do not give features to the present disclosure) can be understood as design matters of those skilled in the art based on the prior art in this field. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in this field.

[0018] In addition, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships.

[0019] In the present disclosure, the reaction gas supplied to the anode of the fuel cell is a fuel gas (anode gas), and the reaction gas supplied to the cathode of the fuel cell is an 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.

[0020] In the present disclosure, there is provided a fuel cell system, wherein the fuel cell system includes a fuel cell, a cooling system, and a control device, the cooling system includes a cooling water pump and a storage tank, when the temperature of the cooling water is equal to or lower than a low temperature determination threshold, the control device performs a heating control to raise the temperature of the cooling water to a target temperature, and after the heating control, the control device cools the temperature of the cooling water to a normal operating temperature lower than the target temperature, and the target temperature is set based on at least any one of the pressure resistance of the cooling system and the operating pressure of the storage tank.

[0021] In general control, the cooling water is set to the same target temperature to operate the fuel cell. On the other hand, in the present disclosure, the target temperature of the cooling water is made variable.

[0022] Figure 1 It is a graph showing the relationship between the temperature of the cooling water and the pressure in the cooling system.

[0023] Along with the heat generation of the fuel cell formed by the operation of the fuel cell, the temperature of the cooling water rises. Moreover, according to the flow rate of the cooling water formed by the drive of the cooling water pump, the outlet pressure of the cooling water pump rises. For example, when the temperature of the cooling water is A°C below the low-temperature determination threshold, if the fuel cell is directly operated, before the temperature of the cooling water reaches the normal use temperature T°C, the pressure in the cooling system reaches the working pressure of the storage tank. If the fuel cell is operated when the temperature of the cooling water is B°C or C°C, even if the temperature of the cooling water reaches the normal use temperature T°C, the pressure in the cooling system will not reach the working pressure of the storage tank, but there will be a situation where the output of the cooling water pump has to be restricted. Therefore, the fuel cell is not operated, the pressure in the cooling system is not changed, and the temperature of the cooling water is intentionally raised to D°C as the target temperature. The target temperature is a temperature higher than the normal use temperature T°C of the cooling water and taking into account at least either the pressure resistance of the cooling system or the working pressure of the storage tank. Thereafter, the temperature of the cooling water is cooled to the normal use temperature T°C to operate the fuel cell.

[0024] Thus, even if the cooling water pump is driven, the pressure in the cooling system will not exceed the pressure resistance of the cooling system.

[0025] Therefore, according to the present disclosure, without restricting the working range of the cooling water pump, the cooling system can be maintained in a manner that does not exceed the pressure resistance of the cooling system.

[0026] In addition, according to the heating control of the present disclosure, there is no need to perform a pressure resistance design for the worst case, the cooling system can be made low-cost, and the cooling water with a desired flow rate can be supplied to the fuel cell, so that the power generation restriction of the fuel cell can also be avoided.

[0027] In the present disclosure, without restricting the working range of the cooling water pump, the cooling system can be maintained in a manner that does not exceed the pressure resistance of the cooling system.

[0028] In the present disclosure, unnecessary heating control of the cooling water can be avoided.

[0029] The fuel cell system of the present disclosure can also be used by being mounted on a moving body such as a vehicle. In addition, the fuel cell system of the present disclosure can also be used by being mounted on a fixed power generation system such as a generator that supplies power to the outside of the fuel cell system.

[0030] The vehicle may also be a fuel cell vehicle or the like. As a moving body other than a vehicle, for example, a train, a ship, an airplane, etc. can be cited.

[0031] In addition, the fuel cell system of the present disclosure can also be mounted on a moving body such as a vehicle that can also travel using the power of a secondary battery for use.

[0032] A moving body and a stationary power generation system may also include the fuel cell system of the present disclosure.

[0033] The moving body may also have drive units such as a motor, an inverter, and a hybrid control system.

[0034] The hybrid control system may also use the output of the fuel cell and the power of the secondary battery together to make the moving body travel.

[0035] The fuel cell system includes a fuel cell that generates electricity by the reaction of hydrogen and oxygen, a control device, and a cooling system that supplies cooling water for cooling the heat generated by power generation to the above fuel cell. The fuel cell system may also include a fuel gas system that supplies fuel gas containing hydrogen required for the power generation of the above fuel cell to the fuel cell, and an oxidant gas system that supplies oxidant gas containing oxygen to the above fuel cell, etc.

[0036] The fuel cell system includes a fuel cell.

[0037] The fuel cell may also be a fuel cell stack (battery stack) that is a laminate of multiple fuel cells as a single cell.

[0038] In the present disclosure, there are cases where both a cell and a fuel cell stack are referred to as a fuel cell.

[0039] The number of stacked cells in the fuel cell stack is not particularly limited. For example, it may be 2 to several hundred.

[0040] The fuel cell stack may also have a current collector plate, a pressure plate, etc. at the end in the stacking direction.

[0041] The cell may also have a power generation part.

[0042] The shape of the power generation part may be rectangular in a top view.

[0043] The power generation part may also be a membrane electrode assembly (MEA) including an electrolyte membrane and two electrodes.

[0044] The electrolyte membrane may also be a solid polymer electrolyte membrane. As the solid polymer electrolyte membrane, for example, a fluorine-based electrolyte membrane such as a thin film of perfluorosulfonic acid containing moisture, and a hydrocarbon-based electrolyte membrane, etc. can be cited. As the electrolyte membrane, for example, a Nafion membrane (manufactured by DuPont) etc. may also be used.

[0045] One of the two electrodes is an anode (fuel electrode), and the other is a cathode (oxidant electrode).

[0046] The electrode includes a catalyst layer, and may also include a gas diffusion layer as needed. The power generation unit may also be a membrane electrode gas diffusion layer assembly (MEGA).

[0047] It may also be configured such that the catalyst layer contains a catalyst, and the catalyst includes a catalyst metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, a carrier having electron conductivity, and the like.

[0048] As the catalyst metal, for example, platinum (Pt), an alloy composed of Pt and other metals (such as a Pt alloy 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.

[0049] As the electrolyte, a fluororesin or the like may also be used. As the fluororesin, for example, a Nafion solution or the like can be used.

[0050] The above catalyst metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalyst metal (catalyst-supported carrier) and the electrolyte may be mixed and present.

[0051] Examples of the carrier for supporting the catalyst metal include carbon materials such as commercially available carbon.

[0052] The gas diffusion layer may also be a conductive member having pores or the like.

[0053] 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.

[0054] The battery cell may also include a separator.

[0055] The separator collects the current generated by power generation and functions as a partition wall. The separator is usually arranged on both sides in the stacking direction of the power generation unit in such a way that a pair of separators sandwich the power generation unit. One of the pair of separators is an anode separator, and the other is a cathode separator.

[0056] The anode separator may have a groove that forms a fuel gas flow path on the surface on the power generation unit side.

[0057] The cathode separator may have a groove that forms an oxidant gas flow path on the surface on the power generation unit side.

[0058] The separator may also have holes such as supply holes and discharge holes for allowing a fluid to flow in the stacking direction of the battery cell to form a manifold.

[0059] As the separator, for example, it can also be a carbon compressed into an airtight dense carbon, a stamped metal (e.g., iron, titanium, stainless steel, etc.), and the like.

[0060] The cell can also include an insulating resin frame disposed on the outer side (periphery) in the plane direction of the membrane electrode assembly between the anode separator and the cathode separator. The resin frame is formed into a plate-like and frame shape using a thermoplastic resin, and seals between the anode separator and the cathode separator while holding the membrane electrode assembly in its central region. As the resin frame, for example, resins such as PE, PP, PET, and PEN can be used. The resin frame can also be a three-layer sheet composed of three layers with an adhesive layer disposed on the surface layer.

[0061] The cooling system supplies cooling water to the fuel cell as a cooling medium.

[0062] The cooling water can be water, ethylene glycol, etc., and can also be a mixture thereof.

[0063] The cooling system includes a cooling water pump, a storage tank, and, as needed, can also include a cooling flow path, a radiator, a bypass flow path, a rotary valve, an ion exchanger, an intercooler, etc.

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

[0065] The storage tank is a tank that temporarily accumulates the cooling water overflowing from the cooling flow path whose internal pressure has increased due to the temperature rise of the cooling water.

[0066] The cooling flow path is a flow path that circulates the cooling water that cools the fuel cell inside and outside the fuel cell.

[0067] The radiator is disposed on the cooling flow path and cools the cooling water.

[0068] The bypass flow path branches from the cooling flow path at a position upstream of the radiator in the cooling flow path, bypasses the radiator, and merges with the above cooling flow path at a position downstream of the radiator in the cooling flow path.

[0069] The rotary valve is disposed at the branch point from the cooling flow path to the bypass flow path. The rotary valve switches the flow path to make the cooling water discharged from the fuel cell flow to the radiator or to the bypass flow path. The rotary valve can also include an electric motor such as an electric actuator for performing the flow path switching.

[0070] The oxidant gas system supplies oxidant gas to the fuel cell and adjusts the flow rate of the above oxidant gas. The oxidant gas system can also include an oxidant gas supply mechanism, oxidant gas piping, an inlet side seal valve at the oxidant gas inlet of the fuel cell, and an outlet side seal valve at the oxidant gas outlet of the fuel cell, etc.

[0071] The oxidant gas supply mechanism may also be an air compressor or the like.

[0072] The fuel gas system supplies fuel gas to the fuel cell and adjusts the flow rate of the fuel gas.

[0073] The fuel gas system may also include a fuel gas tank, a fuel gas inlet valve, an injector, a gas-liquid separator, an exhaust and drain valve, an ejector for fuel gas circulation, a fuel gas pump for fuel gas circulation, and fuel gas piping.

[0074] The fuel cell system may also include a secondary battery.

[0075] The secondary battery only needs to be able to charge and discharge. For example, known secondary batteries such as nickel-metal hydride secondary batteries and lithium-ion secondary batteries can be cited. In addition, the secondary battery may also include a power storage element such as an electric double layer capacitor. The secondary battery may also be configured such that a plurality of them are connected in series. The secondary battery supplies power to an air compressor or the like. For example, the secondary battery may be able to be charged from an external power source such as a household power supply of the fuel cell system. The secondary battery may also be charged by the output of the fuel cell. The charge and discharge of the secondary battery may be controlled by the control device.

[0076] The fuel cell system includes a control device. The control device may control the oxidant gas system, the fuel gas system, the cooling system, etc., and control the entire fuel cell system.

[0077] Physically, the control device has, for example, an arithmetic processing device such as a CPU (central processing unit), a ROM (read-only memory) that stores a control program and control data processed by the CPU, and a RAM (random access memory) that is mainly used as various working areas for control processing, and an input / output interface, and may be an ECU (electronic control unit) or the like.

[0078] When the temperature of the cooling water is below the low-temperature determination threshold, the control device performs temperature-raising control to raise the temperature of the cooling water to the target temperature. In order to control the reference pressure of the cooling system, the control device temporarily raises the temperature of the cooling water to the target temperature.

[0079] For the temperature-raising control, a heater may be provided at an arbitrary position in the cooling system, and the temperature of the cooling water may be raised by the heater.

[0080] After the above temperature-raising control, the control device cools the cooling water to a normal operating temperature lower than the target temperature.

[0081] The above target temperature only needs to be higher than the usually used temperature. The above target temperature is set based on at least any one of the pressure resistance of the above cooling system and the working pressure of the above storage tank.

[0082] The low-temperature determination threshold can be set based on at least any one of the pressure resistance of the above cooling system and the working pressure of the above storage tank, or can be below the freezing point.

[0083] Regarding the pressure resistance of the cooling system, it is also possible to prepare a data group related to the pressure resistance in advance and set it with reference to the data group related to the pressure resistance.

[0084] Regarding the working pressure of the storage tank, it is also possible to prepare a data group representing the relationship between the pressure resistance of the cooling system and the working pressure of the storage tank in advance and set it based on the pressure resistance of the cooling system.

[0085] The fuel cell system may also include a temperature sensor.

[0086] The temperature of the cooling water can also be measured by the temperature sensor.

[0087] The control device can also determine whether the temperature of the cooling water measured by the temperature sensor is below the low-temperature determination threshold.

[0088] When the temperature of the cooling water measured by the temperature sensor is below the low-temperature determination threshold, the control device can also perform the above-mentioned heating control.

[0089] The control device can also determine whether the temperature of the cooling water measured by the temperature sensor is below the low-temperature determination threshold at the start of the fuel cell system or always.

[0090] The control device can also monitor the temperature history of the cooling water temperature.

[0091] When the above temperature history becomes below the above low-temperature determination threshold, the control device can also perform the above-mentioned heating control.

[0092] The control device can also have a temperature monitor for monitoring the temperature of the cooling water.

[0093] Figure 2 It is a flowchart showing an example of the control of the fuel cell system of the present disclosure.

[0094] The control device performs heating control and intentionally raises the temperature of the cooling water to the target temperature (target water temperature).

[0095] The control device determines whether the temperature of the cooling water reaches the target temperature.

[0096] After determining that the temperature of the cooling water has reached the target temperature, the control device cools the temperature of the cooling water to the normal operating temperature and shifts to the normal operation of the fuel cell.

[0097] Figure 3 It is a flowchart showing another example of the control of the fuel cell system of the present disclosure.

[0098] The control device monitors the temperature history of the cooling water (water temperature confirmation).

[0099] The control device determines whether the temperature of the cooling water measured by the temperature sensor is below the low temperature determination threshold.

[0100] When it is determined that the above temperature history has exceeded the above low temperature determination threshold, the control device does not perform the temperature increase control and sets the temperature of the cooling water to the normal operating temperature.

[0101] On the other hand, when it is determined that the above temperature history is below the above low temperature determination threshold, the control device performs the temperature increase control and raises the temperature of the cooling water to the target temperature.

[0102] The control device determines whether the temperature of the cooling water has reached the target temperature.

[0103] After determining that the temperature of the cooling water has reached the target temperature, the control device cools the temperature of the cooling water to the normal operating temperature, shifts to the normal operation of the fuel cell, and ends the control. It is also possible to repeatedly perform the low temperature determination after the control ends.

[0104] Thereby, it is possible to avoid the implementation of unnecessary temperature increase control, and thus it is excellent from the viewpoints of the efficiency of the fuel cell system and the durability of the fuel cell.

Claims

1. A fuel cell system, wherein: The fuel cell system comprises a fuel cell, a cooling system and a control device. The cooling system includes a cooling water pump and a storage tank. When the temperature of the cooling water is lower than a low temperature determination threshold, the control device performs temperature increase control to increase the temperature of the cooling water to a target temperature. The control device cools the temperature of the cooling water to a normal use temperature lower than the target temperature after the temperature increase control. The target temperature is set based on at least one of the withstand pressure of the cooling system and the operating pressure of the storage tank.

2. The fuel cell system according to claim 1, wherein: The control device monitors the temperature history of the temperature of the cooling water, The control device performs the temperature increase control when the temperature history becomes equal to or lower than the low temperature determination threshold.

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