Fuel cell module

Abstract

To suppress deterioration of a fuel cell stack due to a dry state inside the fuel cell stack while suppressing damage to components constituting an air compressor, even when a fuel cell module is used in an environment having a relatively low atmospheric pressure.SOLUTION: A fuel cell module FCM is configured to include an air regulating valve ARV and a control unit Cnt for controlling operation of the air regulating valve ARV so that a pressure detected by a pressure detection unit Sp does not exceed an upper limit value Pmax. When determining that the inside of a fuel cell stack FCS is in a dry state, the control unit Cnt sets the upper limit value Pmax to a first pressure corresponding to a temperature of an air compressor ACP. When determining that the inside of the fuel cell stack FCS is not in the dry state, the control unit Cnt sets the upper limit value Pmax to a second pressure lower than the first pressure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell module. [Background technology]

[0002] Some fuel cell modules use a pressure regulator valve to adjust the pressure in a flow path upstream of the fuel cell stack so that the pressure in the flow path of oxidant gas supplied to the fuel cell stack does not exceed an upper limit.

[0003] Incidentally, when a fuel cell module is used in an environment where the atmospheric pressure is relatively low, such as at high altitudes, a relatively high compression ratio is required in the air compressor. However, if the components that make up the air compressor cannot withstand that high compression ratio, there is a risk that the components will be damaged.

[0004] Therefore, it is possible to reduce the compression ratio of the air compressor by lowering the upper limit of the pressure in the upstream flow path of the fuel cell stack, but this could result in the flow rate of the oxidant gas supplied to the fuel cell stack not reaching the target flow rate, causing the fuel cell stack to become dry and leading to deterioration of the fuel cell stack. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2014-148153 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of one aspect of the present invention is to suppress damage to components that make up the air compressor, while suppressing deterioration of the fuel cell stack due to the inside of the fuel cell stack becoming dry, even when the fuel cell module is used in an environment with relatively low atmospheric pressure. [Means for solving the problem]

[0007] One embodiment of the fuel cell module according to the present invention comprises a fuel cell stack, an air compressor that supplies oxidant gas to the fuel cell stack via an upstream flow path of the fuel cell stack, a pressure regulating valve that is provided in the downstream flow path of an overall flow path that leads to the downstream flow path of the fuel cell stack without branching from the upstream flow path and that adjusts the pressure in the overall flow path, a pressure detection unit that detects the pressure in the upstream flow path, and a control unit that controls the operation of the air compressor and also controls the operation of the pressure regulating valve so that the pressure detected by the pressure detection unit does not exceed an upper limit value.

[0008] When the control unit determines that the inside of the fuel cell stack is in a dry state, it sets the upper limit value to a first pressure corresponding to the temperature of the air compressor, and when it determines that the inside of the fuel cell stack is not in a dry state, it sets the upper limit value to a second pressure lower than the first pressure.

[0009] As a result, even when the fuel cell module is used in an environment with relatively low atmospheric pressure, as long as the fuel cell stack is not dry, the upper limit of the pressure in the upstream flow path of the fuel cell stack can be set to a second pressure lower than the first pressure, i.e., a relatively low upper limit. This allows the compression ratio of the air compressor to be reduced, thereby preventing damage to components constituting the air compressor. Furthermore, even if the fuel cell stack is dry, if the temperature of the air compressor is relatively low and there is sufficient time before it reaches the temperature at which the output current of the fuel cell stack is limited, the upper limit can be set to a relatively high first pressure. This allows the flow rate of oxidant gas supplied to the fuel cell stack to be increased, preventing the fuel cell stack from becoming dry and preventing deterioration of the fuel cell stack. In other words, damage to components constituting the air compressor can be prevented while also preventing deterioration of the fuel cell stack.

[0010] Furthermore, the fuel cell module may include a temperature detection unit that detects the temperature of the air compressor, and when the control unit determines that the inside of the fuel cell stack is in a dry state, it may refer to information that corresponds the temperature of the air compressor with an upper limit value of the pressure in the upstream flow path, and set the upper limit value corresponding to the temperature detected by the temperature detection unit as the first pressure, and the upper limit value in the information may gradually increase as the temperature of the air compressor gradually decreases.

[0011] This allows the upper limit value to be changed gradually when the fuel cell stack is in a dry state and the temperature of the air compressor changes gradually, thereby preventing the flow rate of oxidant gas from overshooting or undershooting due to a sudden change in the upper limit value. [Effects of the Invention]

[0012] According to the present invention, even when a fuel cell module is used in an environment with a relatively low atmospheric pressure, it is possible to suppress damage to the components that make up the air compressor while suppressing deterioration of the fuel cell stack due to the interior of the fuel cell stack becoming dry. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating an example of a fuel cell module according to an embodiment; [Figure 2] 10 is a flowchart illustrating an example of the operation of a control unit. [Figure 3] FIG. 10 is a diagram showing an example of information indicating the correspondence relationship between the temperature of the air compressor and the upper limit value of the pressure in the upstream flow path of the fuel cell stack. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0015] FIG. 1 is a diagram illustrating an example of a fuel cell module according to an embodiment.

[0016] The fuel cell module FCM shown in FIG. 1 is mounted on a vehicle such as a forklift, a towing tractor, or an automatic guided vehicle (AGV), and supplies power to a load Lo mounted on the vehicle. In this configuration, the load Lo is, for example, an inverter circuit that drives a loading device or a travel motor. The fuel cell module FCM may also be provided in a stationary generator such as an industrial stationary generator, a home stationary generator, or an emergency stationary generator. In this configuration, the load Lo is, for example, industrial machinery or a home appliance.

[0017] The fuel cell module FCM also includes a fuel cell stack FCS, which is the main unit, and a number of types of auxiliary units for causing the fuel cell stack FCS to generate electricity.

[0018] That is, the fuel cell module FCM includes a fuel tank HT and an injector INJ as fuel gas system accessories.

[0019] The fuel cell module FCM also includes, as oxidant gas system accessories, an air compressor ACP, a pressure sensor Sp (pressure detection unit), an air pressure regulating valve ARV (pressure regulating valve), and a diluter DIL.

[0020] The fuel cell module FCM also includes cooling system accessories such as an intercooler IC, a radiator R, a fan F, and a water pump WP.

[0021] The fuel cell module FCM also includes a DC-DC converter CNV and a power storage device B as electrical auxiliaries.

[0022] The fuel cell module FCM further includes a memory unit Stg and a control unit Cnt.

[0023] The fuel cell stack FCS is composed of multiple fuel cell cells connected in series, and generates electricity through an electrochemical reaction between the hydrogen contained in the fuel gas (hydrogen gas) and the oxygen contained in the oxidant gas (air).

[0024] The fuel tank HT is a storage container for fuel gas. The fuel gas stored in the fuel tank HT is supplied to the fuel cell stack FCS via the injector INJ.

[0025] The injector INJ adjusts the flow rate of the fuel gas supplied to the fuel cell stack FCS.

[0026] The air compressor ACP is, for example, a Roots-type air compressor, and supplies oxidant gas to the fuel cell stack FCS via an intercooler IC and an upstream flow path FU of the fuel cell stack FCS. The air compressor ACP also includes a pump Pu, a motor M, an inverter INV, a temperature detection unit St, and a control unit Cnti.

[0027] The pump Pu compresses the oxidant gas present around the fuel cell module FCM and supplies it to the fuel cell stack FCS via the intercooler IC and the upstream flow path FU.

[0028] The motor M adjusts the flow rate of the oxidant gas supplied to the fuel cell stack FCS.

[0029] The inverter INV drives the motor M.

[0030] The temperature detection unit St is configured by, for example, an outside air temperature sensor or a thermistor, detects the temperature of a switching element (not shown) that configures the inverter INV or the temperature of the motor M, and sends the detected temperature to the control unit Cnti.

[0031] The control unit Cnti controls the operation of the inverter INV. For example, the control unit Cnti controls the on / off of each of the switching elements constituting the inverter INV so that the rotation speed of the motor M follows the target rotation speed sent from the control unit Cnt. Note that the higher the target rotation speed, the greater the flow rate of the oxidant gas supplied to the fuel cell stack FCS.

[0032] Furthermore, the control unit Cnti sends the temperature detected by the temperature detection unit St to the control unit Cnt.

[0033] The pressure sensor Sp detects the pressure P in the upstream flow path FU of the fuel cell stack FCS (the pressure of the oxidant gas input to the fuel cell stack FCS or the pressure of the oxidant gas output from the intercooler IC) and sends the detected pressure P to the control unit Cnt.

[0034] The air pressure regulating valve ARV is provided in the downstream flow path FD of the overall flow path that does not branch off from the upstream flow path FU of the fuel cell stack FCS but leads through the fuel cell stack FCS to the downstream flow path FD of the fuel cell stack FCS, and adjusts the pressure within the overall flow path.

[0035] The intercooler IC exchanges heat between the oxidant gas, which has been heated by compression, and a refrigerant such as cooling water flowing through the intercooler IC.

[0036] The radiator R exchanges heat between the refrigerant, which has been heated by the heat generated by the fuel cell stack FCS, and the outside air.

[0037] Fan F increases the amount of heat dissipated by radiator R.

[0038] The water pump WP supplies the refrigerant cooled by the radiator R to the fuel cell stack FCS via the intercooler IC. That is, the temperature in the upstream flow path FU of the fuel cell stack FCS is adjusted by the refrigerant supplied to the fuel cell stack FCS by the intercooler IC, radiator R, fan F, and water pump WP.

[0039] The DC-DC converter CNV is connected to the rear of the fuel cell stack FCS and converts the voltage output from the fuel cell stack FCS to a predetermined voltage (for example, 48 V). The power output from the DC-DC converter CNV is supplied to auxiliary equipment such as the air compressor ACP and the water pump WP, the load Lo, and the power storage device B.

[0040] The power storage device B is configured with a lithium ion capacitor or the like, and is connected between the DC-DC converter CNV and the load Lo. When the supply power corresponding to the difference between the power output from the DC-DC converter CNV and the total value of the power supplied to the auxiliary devices is greater than the requested power requested from outside the fuel cell module FCM (for example, a vehicle-side control unit or a stationary generator-side control unit that controls the operation of the load Lo), a portion of the supplied power equal to the requested power is supplied to the load Lo, and the remaining power is supplied to the power storage device B. When power is supplied from the DC-DC converter CNV to the power storage device B, the power storage device B is charged, and the charging rate of the power storage device B (the ratio [%] of the remaining capacity to the full charge capacity of the power storage device B) increases. Furthermore, when regenerative power supplied from the load Lo to the fuel cell module FCM is supplied to the power storage device B, the power storage device B is charged, and the charging rate of the power storage device B increases. Furthermore, if the supply power corresponding to the difference between the power output from the DC-DC converter CNV and the total value of the power supplied to the auxiliary devices is smaller than the required power requested from outside the fuel cell module FCM, the supply power is supplied to the load Lo, and the shortfall in power is supplied to the load Lo from the power storage device B. When power is supplied from the power storage device B to the load Lo, the power storage device B is discharged and the charging rate of the power storage device B decreases.

[0041] The storage unit Stg is configured by a non-volatile memory such as a ROM (Read Only Memory), a flash memory, etc. It is assumed that the storage unit Stg stores information D, which will be described later, and the like.

[0042] The control unit Cnt is configured with a microcomputer or the like and controls the power generation of the fuel cell stack FCS. For example, when controlling the power generation of the fuel cell stack FCS, the control unit Cnt gradually changes the target power generation Pt in accordance with the result of comparing the state of charge of the power storage device B with multiple thresholds, and controls the operation of each auxiliary device (such as the air compressor ACP and air pressure regulating valve ARV) using PI (Proportional-Integral) control or the like so that the power generation of the fuel cell stack FCS follows the target power generation Pt. For example, the control unit Cnt controls the operation of the air compressor ACP so that the rotational speed of the motor M follows a target rotational speed corresponding to the target power generation Pt. The control unit Cnt also controls the operation of the air pressure regulating valve ARV so that the pressure detected by the pressure sensor Sp does not exceed an upper limit value Pmax. Note that the control unit Cnt sets the upper limit value Pmax relatively low when controlling the power generation of the fuel cell stack FCS so that the components of the air compressor ACP will not be damaged even in an environment with relatively low atmospheric pressure.

[0043] Furthermore, when the temperature of the air compressor ACP exceeds the temperature threshold, the control unit Cnt controls the power generation of the fuel cell stack FCS so as to limit the current output from the fuel cell stack FCS. For example, the control unit Cnt determines the temperature of the switching element or motor M sent from the control unit Cnti as the temperature of the air compressor ACP. Alternatively, the control unit Cnt determines the temperature of the air compressor ACP by multiplying the temperature of the switching element or motor M sent from the control unit Cnti by a constant. The temperature threshold is also set to the rated temperature of the air compressor ACP. In this way, when the temperature of the air compressor ACP is relatively high, the output current of the fuel cell stack FCS is limited. This reduces the load on the air compressor ACP, suppresses the temperature rise of the air compressor ACP, and prevents the components constituting the air compressor ACP from being damaged by heat. On the other hand, when the temperature of the air compressor ACP is relatively low, the components constituting the air compressor ACP are less likely to be damaged by heat, so there is room to increase the output current of the fuel cell stack FCS.

[0044] The control unit Cnt also sets an upper limit value Pmax according to the dry state (dry-up state) inside the fuel cell stack FCS and the temperature of the air compressor ACP. For example, if the output impedance of the fuel cell stack FCS calculated by the DC-DC converter CNV is smaller than an impedance threshold, the control unit Cnt determines that the inside of the fuel cell stack FCS is not dry, and if the output impedance of the fuel cell stack FCS is equal to or greater than the impedance threshold, the control unit Cnt determines that the inside of the fuel cell stack FCS is dry. The impedance threshold is, for example, the minimum value of the output impedance of the fuel cell stack FCS when the inside of the fuel cell stack FCS is dry.

[0045] Fig. 2 is a flowchart showing the operation of the control unit Cnt when setting the upper limit value Pmax. The flowchart shown in Fig. 2 is assumed to be executed, for example, at each power generation control cycle of the fuel cell stack FCS.

[0046] When the control unit Cnt determines that the inside of the fuel cell stack FCS is dry (step Stp1: Yes), it sets the upper limit value Pmax to a first pressure corresponding to the temperature of the air compressor ACP (step Stp2). For example, the control unit Cnt references information D that associates the temperature of the air compressor ACP with the upper limit value Pmax, and sets the upper limit value Pmax corresponding to the temperature detected by the temperature detection unit St as the first pressure. For example, the first pressure is set to the maximum value of the pressure in the upstream flow path FU when the output current of the fuel cell stack FCS is not limited by the temperature of the air compressor ACP.

[0047] On the other hand, if the control unit Cnt determines that the inside of the fuel cell stack FCS is not dry (step Stp1: No), it sets the upper limit value Pmax to a second pressure lower than the first pressure (step Stp3). For example, the second pressure is set to the minimum value of the pressure in the upstream flow path FU when the output current of the fuel cell stack FCS is not limited by the temperature of the air compressor ACP.

[0048] Fig. 3 is a diagram showing an example of information D. Note that the horizontal axis of the two-dimensional coordinate system shown in Fig. 3 represents temperature [°C], and the vertical axis represents pressure [kpaA]. The solid line shown in Fig. 3 is information D that indicates the correspondence relationship between the temperature of the air compressor ACP and the upper limit value Pmax.

[0049] In the information D shown in FIG. 3, when the temperature of the air compressor ACP is equal to or lower than the temperature TL, the upper limit of the pressure in the upstream flow path FU is pressure PH, and when the temperature of the air compressor ACP is equal to or higher than the temperature TH, the upper limit of the pressure in the upstream flow path FU is pressure PL. When the first pressure is set using the information D shown in FIG. 3, the second pressure is lower than pressure PL. For example, temperature TH is the maximum temperature of the air compressor ACP when the output current of the fuel cell stack FCS is not limited, and pressure PL is the pressure in the upstream flow path FU when the temperature of the air compressor ACP is at temperature TH. For example, pressure PH is the pressure in the upstream flow path FU when the temperature of the air compressor ACP is at temperature TL, and is the maximum pressure in the upstream flow path FU when the atmospheric pressure is relatively low and the pressure applied to the components that make up the air compressor ACP is equal to or lower than the rated pressure.

[0050] 3, the upper limit value of the pressure in the upstream flow path FU gradually increases from pressure PL to pressure PH as the temperature of the air compressor ACP gradually decreases from temperature TH to temperature TL. In other words, when the temperature of the air compressor ACP changes within the range from temperature TL to temperature TH, the upper limit value of the pressure in the upstream flow path FU changes linearly within the range from pressure PL to pressure PH. This allows the upper limit value Pmax to be changed gradually when the inside of the fuel cell stack FCS is dry and the temperature of the air compressor ACP changes gradually, thereby preventing the flow rate of the oxidant gas from overshooting or undershooting due to a sudden change in the upper limit value Pmax.

[0051] Incidentally, when the fuel cell module FCM is used in an environment where the atmospheric pressure is relatively low, such as a high-altitude environment, a relatively high compression ratio is required for the air compressor ACP. However, if the components that make up the air compressor ACP cannot withstand that high compression ratio, there is a risk that the components will be damaged.

[0052] Therefore, it is possible to consider setting the upper limit value Pmax of the pressure in the upstream flow path FU relatively low. However, simply setting the upper limit value Pmax of the pressure in the upstream flow path FU relatively low will reduce the compression ratio in the air compressor ACP, thereby preventing damage to the components that make up the air compressor ACP. However, there is a risk that the flow rate of the oxidant gas input to the fuel cell stack FCS will not reach the target flow rate, causing the fuel cell stack FCS to become dry, resulting in deterioration of the fuel cell stack FCS.

[0053] Therefore, in the fuel cell module FCM of the embodiment, if it is determined that the inside of the fuel cell stack FCS is in a dry state, the upper limit value Pmax is set to a first pressure corresponding to the temperature of the air compressor ACP, and if it is determined that the inside of the fuel cell stack FCS is not in a dry state, the upper limit value Pmax is set to a second pressure lower than the first pressure.

[0054] As a result, even when the fuel cell module FCM is used in an environment with relatively low atmospheric pressure, as long as the fuel cell stack FCS is not dry, the upper limit value Pmax of the pressure in the upstream flow path FU of the fuel cell stack FCS can be set to a second pressure lower than the first pressure, i.e., the upper limit value Pmax can be set to a relatively low pressure. This allows the compression ratio of the air compressor ACP to be reduced, thereby preventing damage to components constituting the air compressor ACP. Furthermore, even if the fuel cell stack FCS is dry, if the temperature of the air compressor ACP is relatively low and there is a margin for the temperature of the air compressor ACP to reach the temperature at which the output current of the fuel cell stack FCS is limited, the upper limit value Pmax can be set to a relatively high first pressure. This allows the flow rate of oxidant gas supplied to the fuel cell stack FCS to be increased, preventing the fuel cell stack FCS from becoming dry and preventing deterioration of the fuel cell stack FCS. In other words, damage to components constituting the air compressor ACP can be prevented while also preventing deterioration of the fuel cell stack FCS.

[0055] Furthermore, in the fuel cell module FCM of the embodiment, when the fuel cell stack FCS is in a dry state, the upper limit value Pmax is set to a relatively low pressure, which reduces the power generation efficiency of the fuel cell stack FCS, but reduces the energy consumption of the air compressor ACP, thereby increasing the efficiency of the entire fuel cell module FCM.

[0056] The present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the spirit and scope of the present invention.

[0057] <Modification> In the control unit Cnt of the above embodiment, when it is determined that the inside of the fuel cell stack FCS is in a dry state, the first pressure is calculated based on one of the temperature of the switching elements constituting the inverter INV and the temperature of the motor M, but the first pressure may also be calculated based on both the temperature of the switching elements constituting the inverter INV and the temperature of the motor M.

[0058] For example, when the control unit Cnt determines that the inside of the fuel cell stack FCS is in a dry state, it may calculate an upper limit value using information D' in which the temperature of the switching elements constituting the inverter INV is correlated with the upper limit value Pmax, and may also calculate an upper limit value using information D'' in which the temperature of the motor M is correlated with the upper limit value Pmax, and may determine the higher of these two upper limit values ​​as the first pressure.

[0059] Even with this configuration, even when the fuel cell module FCM is used in an environment with relatively low atmospheric pressure, damage to the components that make up the air compressor ACP can be suppressed, while deterioration of the fuel cell stack FCS due to the inside of the fuel cell stack FCS becoming dry can be suppressed. [Explanation of symbols]

[0060] FCM Fuel Cell Module Lo load FCS fuel cell stack HT fuel tank INJ injector ACP Air Compressor ARV Air Pressure Regulating Valve DIL Diluter R radiator F Fan WP water pump IC intercooler CNV DC / DC converter B Energy storage device Sp pressure sensor Stg storage Cnt control unit Pu pump Medium motor INV Inverter Cnti control unit

Claims

1. a fuel cell stack; an air compressor that supplies an oxidant gas to the fuel cell stack via an upstream flow path of the fuel cell stack; a pressure regulating valve provided in the downstream flow path of an entire flow path that does not branch from the upstream flow path but leads to the downstream flow path of the fuel cell stack via the fuel cell stack, and that adjusts the pressure in the entire flow path; a pressure detection unit that detects a pressure in the upstream flow path; a control unit that controls the operation of the air compressor and also controls the operation of the pressure regulating valve so that the pressure detected by the pressure detecting unit does not exceed an upper limit value; Equipped with The control unit When it is determined that the inside of the fuel cell stack is in a dry state, the upper limit value is set to a first pressure corresponding to the temperature of the air compressor, If it is determined that the inside of the fuel cell stack is not dry, the upper limit value is set to a second pressure that is lower than the first pressure. Fuel cell module.

2. 10. The fuel cell module of claim 1, a temperature detection unit for detecting the temperature of the air compressor; When the control unit determines that the inside of the fuel cell stack is in a dry state, the control unit references information that associates the temperature of the air compressor with an upper limit value of the pressure in the upstream flow path, and sets the upper limit value corresponding to the temperature detected by the temperature detection unit as the first pressure; The upper limit value in the information gradually increases as the temperature of the air compressor gradually decreases. Fuel cell module.

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