JP2008218164A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of efficiently removing moisture in a fuel cell, while suppressing energy consumption. <P>SOLUTION: The fuel cell system is equipped with a fuel cell 10 and a coolant circulation line 4 for circulating a coolant to the fuel cell 10, and a coolant storing part 61 capable of storing the coolant in a hot state and stored coolant supply control parts 5, 53, 62 controlling the supply of the coolant from the coolant storing part 61 to the fuel cell 10 are installed in the coolant circulation line 4, and the stored coolant supply control parts 5, 53, 62 supply the coolant from the coolant storing part 61 to the fuel cell 10, prior to scavenging treatment or during the scavenging treatment of the fuel cell 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell and a refrigerant circulation system for circulating a refrigerant in the fuel cell.

Currently, a fuel cell system including a fuel cell that receives a supply of reaction gas (fuel gas and oxidizing gas) and generates electric power has been proposed and put into practical use. In such a fuel cell system, power is generated by an electrochemical reaction of a reaction gas supplied to the fuel cell, and water is generated at that time. If such generated water remains in the fuel cell even after power generation is stopped, it freezes when the outside air temperature decreases, and the efficiency at the next power generation start is reduced.
For this reason, when the fuel cell power generation is started, the refrigerant heated by the heater is supplied to the fuel cell to release the freeze of the generated water, or immediately after the fuel cell power generation is stopped, the dry gas is supplied to the fuel cell to generate the generated water. A technique of performing a scavenging process for discharging in advance has been proposed (see, for example, Patent Document 1).
JP 2002-208422 A

  By the way, when performing the scavenging process as described above, a higher water removal efficiency can be obtained if the fuel cell is maintained at a high temperature, and the scavenging process can be completed in a short time. For example, when the power generation is stopped at a relatively low temperature, the water removal efficiency in the subsequent scavenging process may decrease because the temperature rises and falls inside. For this reason, it is conceivable to use an electric heater to raise the temperature of the refrigerant of the fuel cell and maintain the fuel cell at a high temperature to perform the scavenging process, but extra energy consumption is required for the temperature rise. End up.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel cell system capable of efficiently removing moisture from the fuel cell while suppressing energy consumption.

  In order to achieve the above object, a fuel cell system according to the present invention is a fuel cell system comprising a fuel cell and a refrigerant circulation system for circulating a refrigerant in the fuel cell, wherein the refrigerant circulation system includes: A refrigerant storage unit capable of storing the refrigerant in a heat-retaining state; and a stored refrigerant supply control unit configured to control supply of the refrigerant from the refrigerant storage unit to the fuel cell, wherein the stored refrigerant supply control unit includes the fuel cell The refrigerant is supplied from the refrigerant reservoir to the fuel cell before or during the scavenging process.

According to such a configuration, in the refrigerant storage section provided in the refrigerant circulation system, the high-temperature refrigerant that has been heated by heat exchange during power generation is stored in a warm state, and before the scavenging process after the fuel cell power generation is stopped or When the stored refrigerant supply control unit supplies this refrigerant to the fuel cell during the scavenging process, for example, even when power generation is stopped when the temperature of the fuel cell is relatively low, the fuel can be used without using an electric heater or the like. The scavenging process can be performed while maintaining the battery at a high temperature.
The stored refrigerant supply control unit supplies the refrigerant to the fuel cell when the temperature of the fuel cell is lower than the temperature of the refrigerant stored in the refrigerant storage unit.

  According to such a configuration, when power generation is stopped in a state where the temperature of the fuel cell is relatively high, it is possible to prevent the temperature of the fuel cell from being lowered due to the refrigerant stored in the refrigerant storage unit.

  According to the present invention, since the fuel cell can be maintained at a temperature suitable for the scavenging process even after power generation is stopped without using an electric heater or the like, the moisture removal of the fuel cell by the scavenging process is efficiently performed while suppressing energy consumption. Can be done well.

  Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an example in which the present invention is applied to an on-vehicle power generation system of a fuel cell vehicle (moving body) will be described.

  As shown in FIG. 1, the fuel cell system 1 according to the present embodiment includes a fuel cell 10 that generates electric power upon receiving a supply of reaction gas (oxidation gas and fuel gas), and the fuel cell 10 has an oxidant gas. An oxidant gas piping system (reactive gas supply system) 2 for supplying the air, a hydrogen gas piping system (reactive gas supply system) 3 for supplying hydrogen gas as a fuel gas to the fuel cell 10, and a coolant such as cooling water are allowed to flow. A refrigerant piping system (refrigerant circulation system) 4 that adjusts the temperature of the fuel cell 1, a control device (storage refrigerant supply control unit) 5 that integrally controls the entire system, and the like are provided.

  The fuel cell 10 has a stack structure in which a required number of unit cells that receive a reaction gas and generate electric power through an electrochemical reaction are stacked. The electric power generated by the fuel cell 10 is supplied to a PCU (Power Control Unit) 11. The PCU 11 includes an inverter, a DC-DC converter, and the like that are disposed between the fuel cell 10 and the traction motor 12. Further, the fuel cell 10 is provided with a current sensor 13 for detecting a current during power generation.

  The oxidant gas piping system 2 includes an air supply passage 21 that supplies the oxidant gas (air) humidified by the humidifier 20 to the fuel cell 10, and an air exhaust that guides the oxidant off-gas discharged from the fuel cell 10 to the humidifier 20. A flow path 22 and an exhaust flow path 23 for guiding the oxidizing off gas from the humidifier 20 to the outside are provided. The air supply passage 21 is provided with a compressor 24 that takes in the oxidizing gas in the atmosphere and pumps it to the humidifier 20. The humidifier 20 can supply the fuel cell 10 via the air supply channel 21 without humidifying the oxidizing gas by switching the internal channel.

  The hydrogen gas piping system 3 includes a hydrogen tank 30 as a fuel supply source storing high-pressure (for example, 70 MPa) hydrogen gas, and hydrogen as a fuel supply passage for supplying the hydrogen gas from the hydrogen tank 30 to the fuel cell 10. A supply flow path 31 and a circulation flow path 32 for returning the hydrogen off-gas discharged from the fuel cell 10 to the hydrogen supply flow path 31 are provided.

  Instead of the hydrogen tank 30, a reformer that generates a hydrogen-rich reformed gas from a hydrocarbon-based fuel, a high-pressure gas tank that stores the reformed gas generated by the reformer in a high-pressure state, and Can also be employed as a fuel supply source. A tank having a hydrogen storage alloy may be employed as a fuel supply source.

  The hydrogen supply flow path 31 is provided with a shutoff valve 33 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 30, a regulator 34 that adjusts the pressure of the hydrogen gas, and an injector 35. A primary pressure sensor 41 and a temperature sensor 42 that detect the pressure and temperature of the hydrogen gas in the hydrogen supply flow path 31 are provided on the upstream side of the injector 35. Further, on the downstream side of the injector 35 and upstream of the junction between the hydrogen supply flow path 31 and the circulation flow path 32, a secondary side pressure sensor 43 that detects the pressure of the hydrogen gas in the hydrogen supply flow path 31. Is provided.

  The regulator 34 is a device that regulates the upstream pressure (primary pressure) to a preset secondary pressure. In the present embodiment, a mechanical pressure reducing valve that reduces the primary pressure is employed as the regulator 34. The mechanical pressure reducing valve has a structure in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. Thus, a publicly known configuration for the secondary pressure can be employed.

  The injector 35 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and gas pressure by driving the valve body directly with a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. The injector 35 includes a valve seat having an injection hole for injecting gaseous fuel such as hydrogen gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is movably accommodated and opens and closes the injection hole.

  In this embodiment, the valve body of the injector 35 is driven by a solenoid that is an electromagnetic drive device, and the opening area of the injection hole is made two or more stages by turning on and off the pulsed excitation current supplied to the solenoid. It can be switched. The gas injection time and gas injection timing of the injector 35 are controlled by a control signal output from the control device 5, whereby the flow rate and pressure of hydrogen gas are controlled with high accuracy.

  Injector 35 changes the opening area (opening) and the opening time of the valve body provided in the gas flow path of injector 35 in order to supply the required gas flow rate downstream thereof, thereby reducing the downstream flow rate. The gas flow rate (or hydrogen molar concentration) supplied to the side (fuel cell 10 side) is adjusted.

  Since the gas flow rate is adjusted by opening and closing the valve body of the injector 35 and the gas pressure supplied downstream of the injector 35 is reduced from the gas pressure upstream of the injector 35, the injector 35 is controlled by a pressure regulating valve (pressure reducing valve, regulator). In this embodiment, the pressure adjustment amount (pressure reduction amount) of the upstream gas pressure of the injector 35 is set so as to match the required pressure within a predetermined pressure range in accordance with the gas demand. It can also be interpreted as a modulatable pressure valve that can be varied.

  In the present embodiment, the injector 35 is arranged on the upstream side of the junction A1 between the hydrogen supply channel 31 and the circulation channel 32. Further, as shown by a broken line in FIG. 1, when a plurality of hydrogen tanks 30 are employed as the fuel supply source, the hydrogen gas supplied from each hydrogen tank 30 joins more than the part (hydrogen gas joining part A2). The injector 35 is arranged on the downstream side.

  A discharge flow path 38 is connected to the circulation flow path 32 via a gas-liquid separator 36 and an exhaust drain valve 37. The gas-liquid separator 36 recovers moisture from the hydrogen off gas. The exhaust / drain valve 37 operates according to a command from the control device 5 to discharge (purge) moisture collected by the gas-liquid separator 36 and hydrogen off-gas containing impurities in the circulation flow path 32 to the outside. Is.

  In addition, the circulation channel 32 is provided with a hydrogen pump 39 that pressurizes the hydrogen off gas in the circulation channel 32 and sends it to the hydrogen supply channel 31 side. The hydrogen off-gas discharged through the exhaust / drain valve 37 and the discharge passage 38 is diluted by the diluter 40 and merges with the oxidizing off-gas in the exhaust passage 23.

  The refrigerant piping system 4 is connected to a refrigerant piping 51 that connects an inlet 50 a and an outlet 50 b of a cooling channel provided in the fuel cell 10 on the outside of the fuel cell 10, and an intermediate position of the refrigerant piping 51 (for example, an intermediate position). A radiator 52 that cools the refrigerant discharged from the fuel cell 10 is provided, and the refrigerant pipe 51 is provided at a position closer to the inlet 50a than the radiator 52 and close to the inlet 50a. A refrigerant pump (stored refrigerant supply control unit) 53 that sucks in from the 50b side and discharges to the inlet 50a side, and an outlet refrigerant temperature sensor 54 that detects the refrigerant temperature in the vicinity of the outlet 50b in the refrigerant pipe 51 are provided.

  The refrigerant piping system 4 includes a bypass pipe 56 that bypasses the radiator 52 by directly connecting the outlet 50b side of the refrigerant pipe 51 to the outlet 50b side and a portion between the radiator 52 and the refrigerant pump 53, a bypass pipe 56, and a refrigerant. A three-way switching valve 57 provided at a junction position between the radiator 52 and the refrigerant pump 53 in the pipe 51 is provided. The three-way switching valve 57 closes the bypass pipe 56 to connect the radiator 52 side of the refrigerant pipe 51 and the refrigerant pump 53 side, and closes the radiator 52 side of the refrigerant pipe 51 to bypass the bypass pipe 56 and the refrigerant pipe. The state is switched to the state in which the refrigerant pump 53 side of 51 is connected.

  In the present embodiment, the refrigerant piping system 4 directly connects the outlet 50b side of the refrigerant piping 51 to the outlet 50b side and the portion between the three-way switching valve 57 and the refrigerant pump 53, so that the radiator 52 and the bypass piping 56 are connected. The bypass pipe 60 for further bypassing, the heat storage tank (refrigerant storage part) 61 provided in the bypass pipe 60, and the joining position of the bypass pipe 60 and the refrigerant pipe 51 between the three-way switching valve 57 and the refrigerant pump 53. And a provided three-way switching valve (stored refrigerant supply control unit) 62.

  Here, the three-way switching valve 62 closes the bypass pipe 60 to connect the three-way switching valve 57 side of the refrigerant pipe 51 and the refrigerant pump 53 side, and closes the three-way switching valve 57 side of the refrigerant pipe 51. The state is switched to a state in which the bypass pipe 60, that is, the heat storage tank 61, and the refrigerant pump 51 side of the refrigerant pipe 51 are connected.

  The heat storage tank 61 has, for example, a double-structured hot water pot that has a storage part that can store a refrigerant on the inside and a vacuum layer on the outside, and retains the refrigerant stored in the storage space by heat insulation by the vacuum layer. . A check valve 63 is provided on the bypass pipe 60 on the opposite side of the heat storage tank 61 from the three-way switching valve 62. The check valve 63 allows the refrigerant to flow into the heat storage tank 61, while suppressing the reverse flow of the refrigerant from the heat storage tank 61. The heat storage tank 61 is provided with a stored refrigerant temperature sensor 64 that detects the temperature of the refrigerant in the storage unit.

  The control device 5 detects an operation amount of an acceleration operation device (accelerator or the like) provided in the vehicle, receives control information such as an acceleration request value (for example, a required power generation amount from a load device such as the traction motor 12), Control the operation of various devices in the system. In addition to the traction motor 12, the load device is an auxiliary device (for example, a compressor 24, a hydrogen pump 39, a cooling pump motor, or the like) necessary for operating the fuel cell 10, and various types of vehicles involved in traveling of the vehicle. It is a collective term for power consumption devices including actuators used in devices (transmissions, wheel control devices, steering devices, suspension devices, etc.), occupant space air conditioners (air conditioners), lighting, audio, and the like.

  The control device 5 is configured by a computer system (not shown). Such a computer system includes a CPU, ROM, RAM, HDD, input / output interface, display, and the like, and various control operations are realized by the CPU reading and executing various control programs recorded in the ROM. It is like that.

  When an ignition switch (not shown) is turned on, hydrogen gas is supplied from the hydrogen tank 30 to the fuel electrode of the fuel cell 10 via the hydrogen supply channel 31, and the humidified air passes through the air supply channel 21. Then, power is generated by being supplied to the oxidation electrode of the fuel cell 10. At this time, the power (required power) to be drawn from the fuel cell 10 is calculated by the control device 5, and hydrogen gas and air in an amount corresponding to the amount of power generation are supplied into the fuel cell 10.

  The control device 5 always compares the detected temperature Tfc detected by the outlet refrigerant temperature sensor 54 with the detected temperature Ta detected by the stored refrigerant temperature sensor 64 while the ignition switch is on, and the detected temperature Tfc detected by the outlet refrigerant temperature sensor 54 is When the temperature is higher than the temperature Ta detected by the stored refrigerant temperature sensor 64, the three-way switching valve 62 is closed on the three-way switching valve 57 side of the refrigerant pipe 51, and the refrigerant pump 53 of the bypass pipe 60, that is, the heat storage tank 61 and the refrigerant pipe 51. Connect to the side.

  Then, when the refrigerant pump 53 is driven, the refrigerant discharged from the outlet 50 b of the fuel cell 10 flows into the bypass pipe 60 and is introduced into the heat storage tank 61. Thereby, the refrigerant stored in the heat storage tank 61 is replaced with a refrigerant having a higher temperature and stored.

  On the other hand, the control device 5 closes the three-way switching valve 62 and the bypass pipe 60 when the detected temperature Tfc detected by the outlet refrigerant temperature sensor 54 is equal to or lower than the detected temperature Ta detected by the stored refrigerant temperature sensor 64 while the ignition switch is on. Thus, the three-way switching valve 57 side of the refrigerant pipe 51 and the refrigerant pump 53 side are connected. Then, when the refrigerant pump 53 is driven, the refrigerant discharged from the outlet 50 b of the fuel cell 10 is not introduced into the heat storage tank 61, and passes through the bypass pipe 56 or the radiator 52 depending on the switching state of the three-way switching valve 57. Return to the fuel cell 10.

  That is, when the temperature detected by the outlet refrigerant temperature sensor 54 is higher than the predetermined temperature, the control device 5 closes the bypass pipe 56 and connects the radiator 52 side of the refrigerant pipe 51 and the refrigerant pump 53 side to the refrigerant. When the temperature detected by the outlet refrigerant temperature sensor 54 is equal to or lower than the predetermined temperature, the radiator 52 side of the refrigerant pipe 51 is closed to close the bypass pipe 56 and the refrigerant pipe 51. The refrigerant is returned to the fuel cell 10 as it is in a state where the refrigerant pump 53 side is connected. At this time, the refrigerant stored in the heat storage tank 61 is not replaced with the refrigerant having a lower temperature and stored.

  Then, when the ignition switch is switched from the on state to the off state, the control device 5 stops the supply of the hydrogen gas from the hydrogen tank 30 to the fuel electrode, while the compressor 24 is in the driving state, and the inside of the humidifier 20 By switching the flow path, a scavenging process for supplying the oxidizing gas to the oxidation electrode of the fuel cell 10 via the air supply flow path 21 without humidifying the oxidizing gas is performed. As a result, dry air that has not been humidified is sent to the oxidation electrode of the fuel cell 10, and is discharged including the moisture generated at the oxidation electrode, thereby removing the moisture of the oxidation electrode of the fuel cell 10. When the removal of moisture from the oxidation electrode is confirmed by the impedance management of the fuel cell 10 or the like, the control device 5 ends the scavenging process and stops the compressor 24.

  At the start of the scavenging process, the control device 5 temporarily closes the three-way switching valve 57 on the radiator 52 side of the refrigerant pipe 51 and connects the bypass pipe 56 and the refrigerant pump 53 side of the refrigerant pipe 51 to each other. The three-way switching valve 62 is closed so that the bypass pipe 60 is closed and the three-way switching valve 57 side and the refrigerant pump 53 side of the refrigerant pipe 51 are connected to each other, and the refrigerant of the fuel cell 10 is driven by the radiator pump 53. Thus, the fuel cell 10 is returned to the fuel cell 10 through the bypass pipe 56 without cooling.

  Then, the detection temperature Tfc detected by the outlet refrigerant temperature sensor 54 and the detection temperature Ta detected by the stored refrigerant temperature sensor 64 are compared, and when the detected temperature Tfc detected by the outlet refrigerant temperature sensor 54 is equal to or higher than the detection temperature Ta detected by the stored refrigerant temperature sensor 64. When the detected temperature Tfc detected by the outlet refrigerant temperature sensor 54 is lower than the detected temperature Ta detected by the stored refrigerant temperature sensor 64, the three-way switching valve 62 is connected to the three-way switching valve 57 side of the refrigerant pipe 51. And the bypass pipe 60, that is, the heat storage tank 61, and the refrigerant pump 51 side of the refrigerant pipe 51 are connected.

  Then, the refrigerant pump 53 is driven, and the high-temperature refrigerant stored in the heat storage tank 61 is sent to the fuel cell 10. Thereby, the scavenging process can be performed while maintaining the fuel cell 10 at a high temperature.

  As described above, according to the present embodiment, the high-temperature refrigerant raised in temperature by heat exchange during power generation is stored in the heat storage tank 61 provided in the refrigerant piping system 4 in a heat-retaining state, and the power generation of the fuel cell 10 is performed. When the temperature of the fuel cell 10 is low during the scavenging process after the stop, the three-way switching valve 62, the refrigerant pump 53, and the control device 5 supply the high-temperature refrigerant in the heat storage tank 61 to the fuel cell 10.

  Therefore, since the fuel cell 10 can be maintained at a high temperature without using an electric heater or the like, it is possible to efficiently remove water from the fuel cell 10 by the scavenging process after stopping power generation while suppressing energy consumption. The scavenging process can be completed in a short time.

  In the above description, the case where the fuel cell 10 is heated by flowing a high-temperature refrigerant in the heat storage tank 61 simultaneously with the scavenging process when the temperature of the fuel cell 10 is low has been described. When the temperature of the battery 10 is low, the scavenging process may be performed after flowing the high-temperature refrigerant in the heat storage tank 61 to the fuel cell 10 and heating the fuel cell 10. However, it is more preferable to perform the heating and the scavenging process simultaneously from the viewpoint of the temperature drop of the fuel cell 10 due to latent heat of vaporization.

  In the above description, the case where the bypass pipe 60 and the heat storage tank 61 are provided in parallel to the fuel cell 10 side of the radiator 52 of the refrigerant pipe 51 has been described as an example. However, the fuel cell 10 and the radiator 52 of the refrigerant pipe 51 are connected to the fuel cell 10. Alternatively, the bypass pipe 60 and the heat storage tank 61 may be provided in parallel on the opposite side.

  However, in this case, since the refrigerant from the radiator 52 may enter the heat storage tank 61 when the refrigerant is discharged from the heat storage tank 61 toward the fuel cell 10, the fuel cell 10 is more than the radiator 52 in the refrigerant pipe 51. A bypass pipe 60 and a heat storage tank 61 are preferably provided on the side. From the viewpoint of suppressing heat dissipation due to the length of the pipe, it is preferable to provide the bypass pipe 60 and the heat storage tank 61 on the fuel cell 10 side of the radiator 52 of the refrigerant pipe 51.

  Furthermore, instead of using the power of the battery, a heater for heating using the regenerative energy of the traction motor 12 may be provided in the heat storage tank 61.

  In addition, even when the fuel cell 10 is generating power, if the temperature of the refrigerant in the heat storage tank 61 is higher than the temperature of the fuel cell 10 (according to the stored refrigerant temperature sensor 64 than the temperature Tfc detected by the outlet refrigerant temperature sensor 54). When the detected temperature Ta is high), the refrigerant in the heat storage tank 61 may be sent to the fuel cell 10 to heat the fuel cell 10 and be used to improve power generation efficiency.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 4 ... Refrigerant piping system (refrigerant circulation system), 5 ... Control apparatus (stored refrigerant supply control part), 10 ... Fuel cell, 53 ... Refrigerant pump (stored refrigerant supply control part), 61 ... Heat storage tank (Refrigerant storage part), 62 ... three-way switching valve (reserved refrigerant supply control part).

Claims (2)

A fuel cell system comprising: a fuel cell; and a refrigerant circulation system for circulating a refrigerant in the fuel cell,
The refrigerant circulation system includes a refrigerant storage unit capable of storing the refrigerant in a heat-retaining state, and a stored refrigerant supply control unit that controls supply of the refrigerant from the refrigerant storage unit to the fuel cell,
The stored refrigerant supply control unit is a fuel cell system that supplies refrigerant from the refrigerant storage unit to the fuel cell before or during the scavenging process of the fuel cell. The fuel cell system according to claim 1, wherein
The stored refrigerant supply control unit is a fuel cell system that supplies the refrigerant to the fuel cell when the temperature of the fuel cell is lower than the temperature of the refrigerant stored in the refrigerant storage unit.

Images