Fuel cell system

Abstract

This technology enables warm-up operation with a higher heat output. [Solution] The fuel cell system comprises a fuel cell stack, a secondary battery, an acquisition unit for acquiring the allowable charging power of the secondary battery, and a control unit for controlling the fuel cell system. The control unit causes the fuel cell system to perform a first warm-up operation when a heat generation amount less than a predetermined threshold heat generation amount is required, and when a heat generation amount greater than or equal to the threshold heat generation amount is required and the allowable charging power is greater than or equal to a predetermined threshold power, the control unit causes the fuel cell system to perform a second warm-up operation when the heat generation amount per unit time of the fuel cell stack is greater than that of the first warm-up operation and at least a portion of the power generated by the fuel cell stack is supplied to the secondary battery.

Description

Technical Field

[0001] This disclosure relates to a fuel cell system.

Background Art

[0002] As a fuel cell system, when the temperature of a fuel cell stack starts below the freezing point, auxiliary components such as an air compressor and valves provided in the flow path of the oxidant gas are controlled, and the oxidant gas supplied to the fuel cell stack, for example, the supply amount of air is reduced to perform power generation with low efficiency, and a warm-up operation for warming the fuel cell stack is performed. A fuel cell system is known. Patent Document 1 describes a technique for charging a battery with surplus power from a fuel cell stack based on the remaining capacity (SOC) of a secondary battery to perform a warm-up operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There has been a demand for performing a warm-up operation with a larger calorific value.

Means for Solving the Problems

[0005] This disclosure has been made to solve the above problems and can be realized in the following forms.

[0006] A fuel cell system is provided according to the embodiment of the present disclosure. The fuel cell system comprises a fuel cell stack, a secondary battery, an acquisition unit for acquiring the allowable charging power of the secondary battery, and a control unit for controlling the fuel cell system. The control unit causes the fuel cell system to perform a first warm-up operation when a heat generation amount less than a predetermined threshold heat generation amount is required, and when a heat generation amount equal to or greater than the threshold heat generation amount is required and the allowable charging power is equal to or greater than a predetermined threshold power, the control unit causes the fuel cell system to perform a second warm-up operation in which the heat generation amount per unit time of the fuel cell stack is greater than that of the first warm-up operation, and at least a portion of the power generated by the fuel cell stack is supplied to the secondary battery. With this type of fuel cell system, the surplus power generated by the fuel cell stack can be supplied to the secondary battery, allowing for a second warm-up operation that generates a large amount of heat.

[0007] Furthermore, this disclosure can be implemented in various forms, for example, as a power generation device equipped with a fuel cell system, a vehicle equipped with a fuel cell system, or a control method for a fuel cell system. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating the schematic configuration of a fuel cell system. [Figure 2] This flowchart shows an example of a rapid warm-up process. [Modes for carrying out the invention]

[0009] A. First Embodiment: Figure 1 shows a schematic configuration of an example of a fuel cell system 100 in one embodiment of the present disclosure. The fuel cell system 100 comprises a fuel cell stack 10, a secondary battery 20, an oxidizer gas supply unit 30, a fuel gas supply unit 40, a cooling unit 50, a hot water supply unit 60, and a control unit 70. The fuel cell system 100 of this embodiment is mounted, for example, in a fuel cell vehicle.

[0010] The fuel cell stack 10 is a polymer electrolyte fuel cell that generates electricity by receiving fuel gas (e.g., hydrogen gas) and oxidizer gas (e.g., air) as reaction gases. The fuel cell stack 10 is composed of multiple fuel cell cells 11 stacked on top of each other. The fuel cell stack 10 includes terminal plates, end plates, housings, etc., which are not shown. Each fuel cell 11 is a power generation element that can generate electricity on its own, and has a membrane electrode gas diffusion layer assembly in which gas diffusion layers are arranged on both sides of a membrane electrode assembly having an electrolyte membrane, and separators arranged on both outer sides of the membrane electrode gas diffusion layer assembly. The electrolyte membrane is composed of a solid polymer thin film that exhibits good proton conductivity when in a wet state containing moisture inside.

[0011] The secondary battery 20 is a battery that temporarily stores electricity generated by the fuel cell stack 10 and regenerative power from a motor (not shown). The electricity stored in the secondary battery 20 is used as driving power for each component of the fuel cell system 100, such as the air compressor, motor, and auxiliary equipment.

[0012] The oxidant gas supply unit 30 supplies oxidant gas to the fuel cell stack 10. In this embodiment, the oxidant gas supply unit 30 supplies air taken in from the outside to the fuel cell stack 10. The oxidant gas supply unit 30 includes, for example, piping through which air flows, an air flow meter, a compressor, an on / off valve, etc.

[0013] The fuel gas supply unit 40 supplies fuel gas to the fuel cell stack 10. In this embodiment, the fuel gas supply unit 40 supplies hydrogen gas from a fuel gas tank to the fuel cell stack 10. The fuel gas supply unit 40 includes, for example, piping through which hydrogen gas flows, on-off valves, regulators, injectors, etc.

[0014] The cooling unit 50 adjusts the temperature of the fuel cell stack 10 by circulating a cooling medium through the fuel cell stack 10. The cooling unit 50 includes, for example, piping through which the cooling medium flows, a radiator, a pump, a three-way valve, etc. As the cooling medium, for example, water or antifreeze containing ethylene glycol, etc., can be used.

[0015] The hot water supply unit 60 heats water using electricity generated by the fuel cell stack 10 and waste heat generated by the fuel cell stack 10, and supplies the resulting hot water to the outside. The hot water supply unit 60 includes, for example, pipes through which water flows, shut-off valves, a water storage tank, a hot water pump, a heat exchanger, an electric water heater, etc.

[0016] The control unit 70 is configured as a computer comprising a CPU, memory, and interface circuits to which each component of the fuel cell system 100 is connected. The control unit 70 outputs signals for controlling the oxidizer gas supply unit 30, the fuel gas supply unit 40, the cooling unit 50, and the hot water supply unit 60, as well as signals for controlling power generation by the fuel cell stack 10. By executing a control program stored in memory, the control unit 70 controls the oxidizer gas supply unit 30 and the fuel gas supply unit 40 to control the flow rates of the oxidizer gas and fuel gas. The control unit 70 also controls the power generation of the fuel cell stack 10. Through these controls, the control unit 70 causes the fuel cell system 100 to perform a warm-up operation. Details of the warm-up operation will be described later. The control unit 70 also functions as an acquisition unit 71. However, some or all of the functions of these units may be implemented by hardware circuits.

[0017] Warm-up operation is an operating state of the fuel cell system 100 in which the fuel cell stack 10 is actively heated so that its temperature reaches a predetermined temperature range. The control unit 70 controls the fuel cell stack 10 so that the output voltage is a predetermined voltage lower than that during normal power generation when not in warm-up operation, and controls the oxidant gas supply unit 30 so that the amount of oxidant gas supplied is a predetermined amount less than that during normal power generation when not in warm-up operation. The control unit 70 can cause the fuel cell system 100 to perform a first warm-up operation and a second warm-up operation. The second warm-up operation is a warm-up operation in which the amount of heat generated per unit time by the fuel cell stack 10 is greater than that during the first warm-up operation, and a portion of the power generated by the fuel cell stack 10 is supplied to the secondary battery 20. The control unit 70 controls the oxidant gas supply unit 30 so that the amount of oxidant gas supplied is less than that during the first warm-up operation when in the second warm-up operation.

[0018] The acquisition unit 71 acquires the allowable charging power of the secondary battery 20. The allowable charging power is a value defined as the upper limit of the charging power of the secondary battery 20, and is a value that indicates the charging performance of the secondary battery 20. The larger the allowable charging power, the more power can be charged. For example, the acquisition unit 71 determines the allowable charging power based on a map or function that defines the relationship between the State of Charge (SOC) of the secondary battery 20 and the temperature of the secondary battery 20 and the allowable charging power.

[0019] Figure 2 is a flowchart showing an example of rapid warm-up processing. This process involves the control unit 70 instructing the fuel cell system 100 to perform warm-up operation upon request. This process is repeatedly executed by the control unit 70 while the fuel cell system 100 is in operation, for example, every 100ms.

[0020] In step S100, the control unit 70 determines whether a warm-up operation is required. For example, the control unit 70 determines that a warm-up operation is required when the temperature of the fuel cell stack 10 is lower than a predetermined threshold temperature or when it is detected that water has been added to the water storage tank of the hot water supply unit 60 during hot water supply by the hot water supply unit 60. When a warm-up operation is required, the control unit 70 proceeds to the process of step S110. On the other hand, when a warm-up operation is not required, the control unit 70 ends the rapid warm-up process.

[0021] In step S110, the control unit 70 determines whether a second warm-up operation is required. More specifically, the control unit 70 determines whether the required heating value, which is the required heat generation amount, is equal to or greater than a predetermined threshold heating value. Whether the required heating value is equal to or greater than the threshold heating value is determined, for example, by the control unit 70 using the required heating value obtained based on a map or function in which the relationship between the temperature of the fuel cell stack 10 and the required heating value is defined. Also, when the control unit 70 detects that water equal to or greater than a predetermined threshold amount has been added to the water storage tank of the hot water supply unit 60, it may determine that the required heating value is equal to or greater than the threshold heating value.

[0022] When a second warm-up operation is required, that is, when the required heating value is equal to or greater than the threshold heating value, the control unit 70 proceeds to the process of step S120. On the other hand, when a second warm-up operation is not required, that is, when the required heating value is less than the threshold heating value, the control unit 70 proceeds to the process of step S135 and starts the first warm-up operation for the fuel cell system 100.

[0023] In step S120, the control unit 70 determines whether the surplus power generated by the warm-up operation can be supplied to the secondary battery 20. More specifically, the control unit 70 determines whether the allowable charging power of the secondary battery 20 acquired by the acquisition unit 71 is equal to or greater than a predetermined threshold power. The threshold power is a predetermined value, for example, the remaining power obtained by subtracting the power consumed by various auxiliary machines and the like provided in the fuel cell system 100 from the power generated by the fuel cell stack 10 in the second warm-up operation.

[0024] If surplus power can be supplied to the secondary battery 20, that is, if the allowable charging power is equal to or greater than the threshold power, the control unit 70 proceeds to step S130 and causes the fuel cell system 100 to start a second warm-up operation. On the other hand, if surplus power cannot be supplied to the secondary battery 20, that is, if the allowable charging power is less than the threshold power, the control unit 70 proceeds to step S135 and causes the fuel cell system 100 to start a first warm-up operation.

[0025] In step S140, the control unit 70 determines whether the request for warm-up operation has been resolved. For example, the control unit 70 determines that the request for warm-up operation has been resolved if it detects that the temperature of the fuel cell stack 10 has risen to a predetermined threshold temperature or that the water temperature in the water storage tank of the hot water supply unit 60 has risen to a predetermined threshold temperature. If the request for warm-up operation has been resolved, the control unit 70 terminates the warm-up operation that was started in step S130 or S135 and ends the warm-up operation process. On the other hand, if the request for warm-up operation has not been resolved, the control unit 70 returns to the process in step S140. In other words, the control unit 70 repeats the process in step S140 and continues to have the fuel cell system 100 perform a warm-up operation until the request for warm-up operation is resolved.

[0026] According to the fuel cell system 100 of this embodiment described above, the control unit 70 performs a second warm-up operation when the allowable charging power is equal to or greater than the threshold power when a heat generation amount equal to or greater than the threshold heat generation amount is required. In other words, the surplus power generated by the fuel cell stack 10 is supplied to the secondary battery 20, allowing a second warm-up operation with a large heat generation amount to be performed.

[0027] B. Other embodiments: (B1) In the above-described embodiment, the control unit 70 supplies a portion of the power generated by the fuel cell stack 10 to the secondary battery 20 during the second warm-up operation. However, the control unit 70 may also supply all of the power generated by the fuel cell stack 10 to the secondary battery 20 during the second warm-up operation.

[0028] (B2) In the above-described embodiment, the control unit 70 may perform the first warm-up operation for a predetermined time before performing the second warm-up operation. In this case, the change in the oxidizer gas supplied to the fuel cell stack 10 is less than when transitioning from a normal power generation operation state (not a warm-up operation) to the second warm-up operation. Therefore, it is possible to suppress abrupt changes in the voltage and output current of the fuel cell stack 10, and abrupt changes in the power supply from the fuel cell stack 10 to the secondary battery 20, which can lead to overcharging.

[0029] (B3) In the embodiments described above, the control unit 70 may determine in step S100 whether or not there is a request for warm-up operation depending on whether or not a request for warm-up operation has been received. Also, the control unit 70 may determine in step S110 whether or not there is a request for a second warm-up operation depending on whether or not a request for a second warm-up operation has been received. Also, the control unit 70 may determine in step S140 whether or not the request for warm-up operation has been resolved depending on whether or not an instruction to end the warm-up operation has been received.

[0030] (B4) In the embodiment described above, the control unit 70 determines whether it can supply the surplus power generated by the warm-up operation in step S120 to the secondary battery 20 by using whether the allowable charging power of the secondary battery 20 is equal to or greater than a threshold power. However, the control unit 70 may also make the determination by using whether the SOC of the secondary battery 20 is equal to or greater than a predetermined threshold energy amount. The threshold energy amount may be determined according to the total capacity of the secondary battery 20 and the required heat generation amount. For example, the threshold energy amount may be the value obtained by subtracting the amount of power supplied to the secondary battery 20 in the second warm-up operation from the total capacity of the secondary battery 20, or more specifically, the value obtained by subtracting the expected power consumption of the auxiliary equipment from the amount of power generated by the fuel cell stack 10, whose heat generation amount due to the second warm-up operation is the required heat generation amount, from the total capacity of the secondary battery 20.

[0031] (B5) In the embodiment described above, when the control unit 70 proceeds from step S130 to step S140, it continues to have the fuel cell system 100 perform the second warm-up operation until the request for warm-up operation is resolved. Not limited to this, the control unit 70 may also transition the fuel cell system 100 from the second warm-up operation to the first warm-up operation when predetermined conditions are met. The predetermined conditions are determined to be met when, for example, the temperature of the fuel cell stack 10 rises to or above a predetermined condition temperature that is below a threshold temperature, or when it is detected that the water temperature in the water storage tank of the hot water supply unit 60 has risen to or above a predetermined condition temperature that is below a threshold water temperature.

[0032] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve the problems described above or to achieve some or all of the effects described above. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0033] 10…Fuel cell stack, 11…Fuel cell cell, 20…Secondary battery, 30…Oxidizer gas supply unit, 40…Fuel gas supply unit, 50…Cooling unit, 60…Hot water supply unit, 70…Control unit, 71…Acquisition unit, 100…Fuel cell system

Claims

[Claim 1] A fuel cell system, Fuel cell stack and Rechargeable batteries and An acquisition unit for acquiring the allowable charging power of the secondary battery, The system comprises a control unit for controlling the fuel cell system, The control unit, If a heat generation amount below a predetermined threshold heat generation amount is required, the fuel cell system is made to perform a first warm-up operation. A fuel cell system that, when a heat generation amount greater than or equal to the threshold heat generation amount is required, and the allowable charging power is greater than or equal to a predetermined threshold power, causes the fuel cell system to perform a second warm-up operation in which the heat generation amount per unit time of the fuel cell stack is greater than that of the first warm-up operation, and supplies at least a portion of the power generated by the fuel cell stack to the secondary battery.

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