Fuel cell system

Abstract

The present invention provides a fuel cell system that can supply a fuel cell with air humidified to an appropriate humidity level. [Solution] The first temperature-controlled liquid circulates between the stack 31 and the heat exchanger 32. The heat exchanger 32 transfers heat from the first temperature-controlled liquid, which is heated by the heat generated by the chemical reaction in the stack 31, to air introduced from the outside. The air is heated and then further heated by the heater 34. The humidifier 37 humidifies the air so that the amount of water vapor in the air at the heated temperature becomes the saturation water vapor amount. Therefore, the solid polymer electrolyte membrane of the stack 31 is humidified by the air humidified by the humidifier 37 and maintained in a moist state. In addition, by adjusting the amount of water vapor in the air to the saturation water vapor amount, the solid polymer electrolyte membrane does not become excessively wet.

Description

Technical Field

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

[0002] The fuel cell system described in Patent Document 1 includes a heat exchanger and a humidifier. The heat exchanger heats off-gas flowing through an oxidant discharge passage with heat from oxidant gas flowing through an oxidant supply passage. The humidifier humidifies the oxidant gas flowing through the oxidant supply passage with moisture contained in the off-gas flowing through the oxidant discharge passage. Humidification of the oxidant gas promotes humidification of an electrolyte membrane of the fuel cell. Prior Art Literature Patent Literature

[0003] Patent Literature 1 Japanese Unexamined Patent Application Publication No. 2012-221657 Summary of the Invention Problems to be Solved by the Invention

[0004] The oxidant gas in Patent Document 1 is air taken in from outside air by a compressor. Since the dew point of air varies depending on temperature, the humidification state of air varies depending on the outside air temperature. When the outside air temperature is low and the dew point is low, air cannot be brought into a sufficiently wet state even after humidification by the humidifier, and thus the electrolyte membrane of the fuel cell cannot be sufficiently humidified. When the outside air temperature is high and the dew point is high, excessive humidification by the humidifier will cause the air to be excessively moist, and if water accumulates inside the fuel cell, power generation efficiency may decrease. Although Patent Document 1 humidifies air, it does not consider the humidification state.

[0005] An object of the present invention is to provide a fuel cell system that can supply air humidified to an appropriate humidity to a fuel cell. Means for Solving the Problems

[0006] According to one aspect of the present invention, a fuel cell system is provided comprising a fuel cell, a first supply path, a first flow path, a first heat exchanger, a heater, and a humidifier. The fuel cell is a device capable of generating electricity by reacting hydrogen and oxygen and supplying power to an electrical load. The first supply path is a flow path for supplying oxygen-containing air introduced from the outside to the fuel cell. The first flow path is a flow path through which a first heat medium, which is a heat medium for heat exchange, flows.

[0007] The first heat exchanger is a device that exchanges heat between the first heat transfer medium flowing through the first flow passage and the air introduced into the first supply passage. The heater is a device that heats the air that has passed through the first heat exchanger. The humidifier is a device that humidifies the air heated by the heater.

[0008] The air introduced into the first supply line is heated by heat exchange with the first heat transfer medium in the first heat exchanger. The air heated in the first heat exchanger is further heated by a heater. The air heated by the heater is humidified by a humidifier. In other words, the air, heated to the appropriate temperature by the heater, is humidified by the humidifier to the appropriate humidity. Therefore, the fuel cell system can supply air humidified to the appropriate humidity to the fuel cell. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram of fuel cell system 1. [Modes for carrying out the invention]

[0010] One embodiment of the present invention is described below. The referenced drawings are used to illustrate the technical features that the present invention may adopt. That is, the configurations, controls, etc., shown in the drawings are not intended to limit the invention to those shown, but are merely illustrative examples.

[0011] The fuel cell system 1 shown in Figure 1 can generate electricity by reacting a fuel with an oxidizer and supply power to an electrical load 4. An example of a fuel is hydrogen. An example of an oxidizer is oxygen from the air.

[0012] The fuel cell system 1 comprises a fuel unit 2 and a power generation unit 3. The fuel unit 2 comprises multiple MH (Metal Hydride) containers 21 and a regulator 22. The MH containers 21 are hydrogen sources and are filled with hydrogen storage alloys. Hydrogen storage alloys are materials that can absorb hydrogen into the gaps created by metal atoms and release the absorbed hydrogen through an endothermic reaction when heated.

[0013] The MH container 21 has a temperature control member 23. The temperature control member 23 is positioned in contact with the MH container 21, and a second temperature control liquid, which is a heat transfer medium, flows through it. The second temperature control liquid is water or antifreeze and circulates between the heat exchanger 41 and the temperature control member 23. The heat exchanger 41 will be described later. The second temperature control liquid is heated in the heat exchanger 41 and heats the MH container 21 by circulating through the temperature control member 23.

[0014] Each of the multiple MH containers 21 is connected to a regulator 22 via a shut-off valve. The regulator 22 adjusts the pressure of the hydrogen supplied to the power generation unit 3 to a predetermined pressure.

[0015] The power generation unit 3 includes a stack 31, heat exchangers 32, 41, 42, a pump 33, a control unit 5, a heater 34, a switch 35, a measuring instrument 36, a humidifier 37, and a diluent 38. The power generation unit 3 further includes a bypass valve 39, a heat transfer medium tank 40, and a heat radiator 43. In addition, the power generation unit 3 includes a hydrogen supply passage 81, a hydrogen discharge passage 82, air supply passages 52-56, air discharge passages 57, 58, circulation passages 61-63, 65-67, 71-74, and a bypass passage 64.

[0016] Stack 31 is a structure formed by stacking multiple flat unit cells. Each unit cell has two separators, two plate-shaped electrodes, and one solid polymer electrolyte membrane. The unit cell is configured with the solid polymer electrolyte membrane placed between the two separators, and further, electrodes placed between each separator and the solid polymer electrolyte membrane. The anode electrode 31A and the cathode electrode 31C are plate-shaped electrodes. The separators have channels through which hydrogen gas or air flows.

[0017] Hydrogen gas supplied from the fuel section 2 through the hydrogen supply passage 81 flows through the separator passage 31B located at the anode electrode 31A and comes into contact with the anode electrode 31A. Hydrogen gas refers to gaseous hydrogen molecules. At the anode electrode 31A, the hydrogen gas releases electrons and becomes hydrogen ions. The hydrogen ions move to the cathode electrode 31C by passing through the solid polymer electrolyte membrane. Electrons move from the anode electrode 31A to the cathode electrode 31C by passing through the electrical load 4 connected to the anode electrode 31A and the cathode electrode 31C.

[0018] Air flows through air supply passages 52-56 and enters the separator channel 31D located at the cathode electrode 31C. The air flowing through the separator channel 31D comes into contact with the cathode electrode 31C. Oxygen in the air receives electrons that have moved to the cathode electrode 31C and becomes oxygen ions. These oxygen ions combine with hydrogen ions that have passed through the solid polymer electrolyte membrane to produce water. The unit cell generates electricity as electrons move from the anode electrode 31A through the electrical load 4 to the cathode electrode 31C.

[0019] The generated water is discharged to the outside along with the air off-gas, which is discharged from the air discharge passages 57 and 58 connected to the outlet of the separator's flow path 31D. The air off-gas is air that flows through the separator's flow path 31D and is discharged outside the stack 31 from the outlet of the flow path 31D.

[0020] The hydrogen supply path 81 is a hydrogen gas flow path for supplying hydrogen gas fed from the fuel section 2 to the stack 31. One end of the hydrogen supply path 81 is connected to the regulator 22 of the fuel section 2. The other end of the hydrogen supply path 81 is connected to the inlet of the flow path 31B of the separator of the anode electrode 31A of the stack 31.

[0021] The hydrogen discharge path 82 is a hydrogen off-gas flow path for introducing hydrogen off-gas discharged from the stack 31 into the diluter 38. The hydrogen off-gas is hydrogen gas that flows through the separator flow path 31B and is discharged out of the stack 31 from the outlet of the flow path 31B. The hydrogen off-gas includes surplus hydrogen gas remaining after the chemical reaction with oxygen, water adhering to the separator flow path 31B, and water vapor obtained by vaporization of the water. Note that the water contained in and suspended in the hydrogen off-gas and hydrogen gas is referred to as moisture.

[0022] One end of the hydrogen discharge path 82 is connected to the outlet of the flow path 31B of the separator of the anode electrode 31A of the stack 31. The other end of the hydrogen discharge path 82 is connected to the diluter 38, which will be described later. A gas-liquid separator is connected to the hydrogen discharge path 82. The gas-liquid separator is a device for separating moisture contained in the hydrogen off-gas from the hydrogen off-gas and discharging the moisture to the outside of the fuel cell system 1.

[0023] The air supply paths 52 to 56 are air flow paths for supplying air introduced from the outside to the stack 31. A heat exchanger 32, a pump 33, a heater 34, a switch 35, a measuring instrument 36, and a humidifier 37 are connected to the air supply paths 52 to 56.

[0024] The chemical reaction in the stack 31 is accompanied by heat generation, and the stack 31 is heated to a third temperature higher than the environmental temperature, which is the temperature outside the fuel cell system 1. The heat exchanger 32 is a device that transfers heat of a first temperature-adjusting liquid, which is a heating medium heated to the third temperature in the stack 31, to the air flowing through the heat exchanger 32.

[0025] The heat exchanger 32 is, for example, a known plate heat exchanger. A plate heat exchanger has a plurality of heat transfer plates. The plurality of heat transfer plates are each arranged at intervals, and air and the first temperature adjustment fluid flow alternately between the respective heat transfer plates. The plate heat exchanger performs heat exchange between the air flowing between the heat transfer plates and the first temperature adjustment fluid.

[0026] The first temperature adjustment fluid is water or antifreeze, and circulates between the heat exchanger 32 and the stack 31. The first temperature adjustment fluid is heated in the stack 31, and heats the air via the heat transfer plates when flowing through the heat exchanger 32. Air introduced from the outside is heated to a first temperature higher than the environmental temperature by flowing through the heat exchanger 32. Note that the first temperature is lower than a third temperature generated by a chemical reaction in the stack 31.

[0027] The air supply path 52 connects the heat exchanger 32 and the pump 33, and sends the air that has flowed through the heat exchanger 32 to the pump 33. The pump 33 is an air pump that applies pressure to introduced air and sends the air out. The control unit 5 can control the driving of the pump 33 to change the flow rate of air flowing through the air supply paths 52 to 56. The air supply path 53 connects the pump 33 and the heater 34, and sends the air delivered from the pump 33 to the heater 34. By increasing the flow rate of air using the pump 33 and increasing the amount of air supplied to the stack 31, the stack 31 can efficiently generate power and improve output.

[0028] The heater 34 is a device that heats introduced air. A switch 35 is connected to the heater 34. The switch 35 is, for example, a semiconductor switch, and switches on and off the power supply to the heater 34. The control unit 5 operates the switch 35 through feedback control based on an air temperature measurement result obtained by a thermometer included in a measuring instrument 36 described later, to turn the heater 34 on and off. Specifically, the control unit 5 turns off the heater 34 when the temperature of air is equal to or higher than the second temperature, and turns on the heater 34 when the temperature of air is lower than the second temperature.

[0029] The air introduced into the heater 34 is heated by the heat exchanger 32 to a first temperature higher than the ambient temperature. The air is then heated by the heater 34 to a second temperature higher than the first temperature. The second temperature is within a certain range, lower than the third temperature produced by the chemical reaction in the stack 31. This range is, for example, a predetermined temperature ± 4 degrees. By preheating the air from the ambient temperature to the first temperature using the heat exchanger 32, the heater 34 can heat the air to the second temperature more efficiently than when heating from the ambient temperature, and power consumption can be reduced.

[0030] Furthermore, a thermostat is connected to the heater 34. The thermostat closes the power supply circuit to the heater 34, allowing power to be supplied, if the temperature is below the operating temperature. When the temperature of the heater 34 itself exceeds the operating temperature, the thermostat opens the power supply circuit to the heater 34, making power supply impossible. The operating temperature is a temperature set in advance to prevent the heater 34 from overheating, and is higher than the second temperature, and consequently higher than the third temperature. The operating temperature is set according to the heat resistance temperature of the components that make up the heater 34.

[0031] The air supply passage 54 connects the heater 34 and the measuring instrument 36, and supplies air heated by the heater 34 to the measuring instrument 36. The measuring instrument 36 includes a flow meter and a thermometer. The flow meter measures the flow rate of air flowing through the air supply passage 54 and introduced into the measuring instrument 36. The thermometer measures the temperature of air flowing through the air supply passage 54 and introduced into the measuring instrument 36.

[0032] The ambient temperature is expected to fluctuate, for example, within a range of -20°C to 45°C. The first temperature of the air flowing through the heat exchanger 32 fluctuates within a temperature range corresponding to the ambient temperature. The air is heated to a second temperature by the heater 34, but if the ambient temperature is low and the amount of air flowing to the pump 33 is large, the air may not reach the second temperature. The control unit 5 obtains the magnitude of the current flowing from the stack 31 to the electrical load 4 as the output of the stack 31. The control unit 5 controls the amount of air flowing from the pump 33 by feedback control according to the output of the stack 31. The first temperature of the air flowing through the heat exchanger 32 changes further depending on the amount of air flowing. The control unit 5 feedback controls the heater 34 so that the air temperature reaches the second temperature.

[0033] The air supply passage 55 connects the measuring instrument 36 and the humidifier 37, sending the air that has passed through the measuring instrument 36 to the humidifier 37. The humidifier 37 is a device that is heated by a heater 34 and humidifies the air introduced through the air supply passage 55. As will be described later, since the air off-gas discharged from the stack 31 flows through the humidifier 37, the humidifier 37 is heated to a temperature higher than the second temperature and lower than the third temperature. Therefore, the air flowing through the humidifier 37 is further heated in the humidifier 37. The air is heated by the humidifier 37 to a temperature higher than the second temperature and lower than the third temperature. In addition, to prevent the air introduced into the stack 31 from having an excessive amount of water vapor, the temperature of the air flowing through the humidifier 37 is adjusted to be closer to the second temperature than the third temperature.

[0034] The humidifier 37 humidifies the air so that the amount of water vapor in the air is greater than the saturation water vapor amount at the second temperature, that is, the amount of water vapor that results in 100% humidity at the second temperature. In other words, by circulating through the humidifier 37, the air is reliably introduced into the stack 31 containing the saturation water vapor amount at the second temperature.

[0035] The air supply passage 56 connects the humidifier 37 to the inlet of the separator channel 31D of the cathode electrode 31C of the stack 31, and sends humidified air from the humidifier 37 to the stack 31. Therefore, the humidified air containing the amount of water vapor at saturation at the second temperature flows through the separator channel 31D. The solid polymer electrolyte membrane is humidified by the air humidified in the humidifier 37 and maintained in a moist state. Furthermore, by adjusting the amount of water vapor in the air to the amount of water vapor at saturation at the second temperature, the solid polymer electrolyte membrane does not become excessively wet.

[0036] The air discharge passages 57 and 58 are air passages for discharging air that has flowed through the flow path 31D within the stack 31 to the outside. A humidifier 37 and a diluent 38 are connected to the air discharge passages 57 and 58.

[0037] The air discharge passage 57 connects the outlet of the flow path 31D of the separator at the cathode electrode 31C of the stack 31 to the humidifier 37, sending the air off-gas that has flowed through the flow path 31D to the humidifier 37. The air off-gas is heated to a third temperature by the heat generated by the chemical reaction in the stack 31 as it flows through the flow path 31D of the stack 31. The heat of the air off-gas flowing through the air discharge passage 57 and introduced to the humidifier 37 is used to generate water vapor to humidify the air that flows through the air supply passage 55 and is introduced to the humidifier 37.

[0038] The air discharge passage 58 connects the humidifier 37 and the diluent 38, sending the air off-gas that has flowed through the humidifier 37 to the diluent 38. The diluent 38 dilutes the hydrogen contained in the hydrogen off-gas that flows through the hydrogen discharge passage 82 and is introduced to the diluent 38 with the air off-gas that flows through the air discharge passage 58 and is introduced to the diluent 38. The diluent 38 reduces the concentration of hydrogen contained in the hydrogen off-gas to a concentration that does not cause a chemical reaction. The hydrogen off-gas diluted by the diluent 38 is discharged to the outside of the power generation unit 3.

[0039] Next, circulation paths 61-63 and 65-67 are flow paths for circulating the first temperature-controlled liquid between the stack 31 and the heat exchanger 32. The stack 31, heat transfer fluid tank 40, bypass valve 39, and heat exchangers 32, 41, and 42 are connected to circulation paths 61-63 and 65-67. Circulation paths 61-63 are the forward paths through which the first temperature-controlled liquid flows from the stack 31 to the heat exchanger 32. Circulation paths 65-67 are the return paths through which the first temperature-controlled liquid flows from the heat exchanger 32 to the stack 31.

[0040] Stack 31 has a flow path 31E through which a first temperature-controlled liquid flows. As the first temperature-controlled liquid flows through the flow path 31E, it is heated to a third temperature by the heat generated by chemical reactions in stack 31. Circulation path 61 connects the outlet of flow path 31E to a heat medium tank 40, sending the first temperature-controlled liquid, heated to the third temperature in flow path 31E, to the heat medium tank 40. The heat medium tank 40 stores the first temperature-controlled liquid and adjusts the flow rate of the first temperature-controlled liquid circulating through circulation paths 61-63, 65-67 and bypass path 64.

[0041] Circulation path 62 connects the heat transfer fluid tank 40 to the bypass valve 39, and circulation path 63 connects the bypass valve 39 to the heat exchanger. The bypass valve 39 is a valve that switches the path through which the first temperature-controlled fluid flows to either the first path through circulation path 63 or the second path through bypass path 64. A thermometer 39A for measuring the ambient temperature is connected to the bypass valve 39.

[0042] If the ambient temperature is below a predetermined temperature, the bypass valve 39 switches the flow path to which the first temperature-controlled liquid is delivered to the first path, the circulation path 63. The predetermined temperature is a temperature set in advance within the range of ambient temperature and is lower than the first temperature. The first temperature-controlled liquid flows through the circulation path 63 and then through the heat exchanger 32. The heat exchanger 32 transfers the heat from the first temperature-controlled liquid to the air, heating the air to the first temperature. As a result, the heater 34 only needs to heat the air from the first temperature, which is higher than the ambient temperature, to the second temperature, thus reducing power consumption.

[0043] The circulation path 65 connects heat exchanger 32 and heat exchanger 41, and sends the first temperature-controlled liquid that has flowed through heat exchanger 32 to heat exchanger 41. The bypass path 64 connects bypass valve 39 and circulation path 65. The bypass path 64 sends the first temperature-controlled liquid discharged from bypass valve 39 to heat exchanger 41 via circulation path 65 without passing through heat exchanger 32.

[0044] If the ambient temperature is above a predetermined temperature, the bypass valve 39 switches the flow path to which the first temperature-controlled liquid is delivered to the second path, the bypass path 64. The first temperature-controlled liquid flows through the bypass path 64 and the circulation path 65, and flows through the heat exchanger 41 without passing through the heat exchanger 32. If the ambient temperature is above a predetermined temperature, the air introduced into the stack 31 is at the same temperature as or close to the first temperature, and there is little need to heat it with the heat exchanger 32. Therefore, the air introduced from the outside does not get overheated even when flowing through the heat exchanger 32, and reaches an appropriate temperature that can be adjusted to the second temperature by heating with only the heater 34.

[0045] The heat exchanger 41 is, for example, a known plate heat exchanger, and is a device that transfers heat from the first temperature-controlled liquid to the second temperature-controlled liquid. The second temperature-controlled liquid flows through circulation paths 71 and 72, circulating between the heat exchanger 41 and the temperature-controlled member 23 of the MH container 21. Circulation path 71 is the forward path through which the second temperature-controlled liquid flows from the heat exchanger 41 to the temperature-controlled member 23. Circulation path 72 is the return path through which the second temperature-controlled liquid flows from the temperature-controlled member 23 to the heat exchanger 41. The MH container 21 is heated via the temperature-controlled member 23 by the heat transferred from the first temperature-controlled liquid, which is heated in the stack 31, to the second temperature-controlled liquid by the heat exchanger 41.

[0046] The circulation path 66 connects heat exchanger 41 and heat exchanger 42, and sends the first temperature-controlled liquid that has flowed through heat exchanger 41 to heat exchanger 42. Heat exchanger 42 is, for example, a known plate heat exchanger, and is a device that transfers heat from the first temperature-controlled liquid to the third temperature-controlled liquid. The third temperature-controlled liquid flows through circulation paths 73 and 74, circulating between heat exchanger 42 and radiator 43. Circulation path 73 is the forward path through which the third temperature-controlled liquid flows from heat exchanger 42 to radiator 43. Circulation path 74 is the return path through which the third temperature-controlled liquid flows from radiator 43 to heat exchanger 42.

[0047] The radiator 43 is a device that transfers heat from the third temperature-controlled liquid to a heat sink connected to a flow pipe through which the third temperature-controlled liquid flows, and then releases the heat into the air. The circulation path 67 connects the heat exchanger 42 to the inlet of the flow path 31E of the stack 31, and sends the first temperature-controlled liquid that has flowed through the heat exchanger 42 to the stack 31. The first temperature-controlled liquid is cooled in the heat exchanger 42 by transferring heat to the third temperature-controlled liquid, which is cooled by the heat dissipation from the radiator 43. Therefore, the stack 31 is cooled by the first temperature-controlled liquid, which has transferred the heat generated by the chemical reaction, circulating through the heat exchangers 32, 41, and 42.

[0048] In this fuel cell system 1, heat is transferred in the heat exchanger 32 from the first temperature-controlled liquid, which has been heated to a third temperature by the heat generated in the stack 31, to the air introduced from the outside. The temperature of the air rises to a first temperature, which is higher than the ambient temperature, as it flows through the heat exchanger 32. The air flows through air supply passages 52 and 53 and is sent to the heater 34, where it is heated to a second temperature, which is higher than the first temperature. The air flows through air supply passages 54 and 55 and is sent to the humidifier 37, where it is humidified, and the amount of water vapor in the air at the second temperature becomes the saturation water vapor amount. In this state, the air flows through air supply passage 56 and is sent to the stack 31, so that the solid polymer electrolyte membrane of the stack 31 is maintained in a moist state without becoming excessively moist.

[0049] Furthermore, the heat from the first temperature-controlled liquid is transferred in the heat exchanger 41 to the second temperature-controlled liquid, which circulates between the heat exchanger 41 and the temperature-controlled member 23. As the second temperature-controlled liquid flows through the temperature-controlled member 23, the MH container 21 in contact with the temperature-controlled member 23 is heated. The hydrogen storage alloy filled in the MH container 21 smoothly releases hydrogen through an endothermic reaction. The hydrogen gas flows through the hydrogen supply passage 81 and is supplied to the stack 31, where it reacts with oxygen in the air, causing the stack 31 to generate electricity.

[0050] The hydrogen off-gas that has flowed through stack 31 flows through hydrogen discharge passage 82 and is sent to diluter 38. The air off-gas that has flowed through stack 31 is heated by the heat generated in stack 31 and flows through air discharge passage 57 and is sent to humidifier 37. The heat from the air off-gas is used in humidifier 37 to generate water vapor for humidifying the air. Furthermore, the air off-gas flows through air discharge passage 58 and is sent to diluter 38 and used to dilute the hydrogen off-gas.

[0051] The heat from the first temperature-controlled liquid is transferred to the third temperature-controlled liquid circulating between the heat exchanger 42 and the heat sink 43 in the heat exchanger 42. As a result, the first temperature-controlled liquid is cooled and returns to the stack 31 via the circulation path 67, where it cools the stack 31, whose temperature has risen due to the heat generated.

[0052] As explained above, the air introduced into the air supply passages 52-56 is heated by heat exchange with the first temperature-controlled liquid in the heat exchanger 32. The air heated in the heat exchanger 32 is further heated by the heater 34. The air heated by the heater 34 is humidified by the humidifier 37. In other words, the air is heated to an appropriate temperature by the heater 34 and then humidified by the humidifier 37 to an appropriate humidity. Therefore, the fuel cell system 1 can supply air humidified to an appropriate humidity to the stack 31.

[0053] The air introduced from the outside into the air supply passages 52-56 is first heated by heat exchange with the first temperature-controlled liquid in the heat exchanger 32, and then heated by the heater 34. Therefore, the temperature to which the heater 34 heats the air to the appropriate temperature is lower than in the case where heating by the heat exchanger 32 does not occur. Consequently, the fuel cell system 1 can suppress the power consumption of the heater 34.

[0054] The air off-gas is heated by the heat generated by the stack 31 and discharged from the stack 31. The humidifier 37 can humidify the air using the heat from the air off-gas. Therefore, the fuel cell system 1 can supply air humidified to the appropriate humidity to the stack 31 while suppressing power consumption compared to when a heater or the like is used as the heat source for the humidifier 37.

[0055] The diluent 38 can utilize the air off-gas, which was used as a heat source for the humidifier 37, to dilute the hydrogen in the hydrogen off-gas. Therefore, the fuel cell system 1 can dilute excess hydrogen and discharge it more safely.

[0056] The second temperature-controlled liquid is heated by heat exchange with the first temperature-controlled liquid via the heat exchanger 41. The MH container 21 is heated via the temperature-controlled member 23 by the second temperature-controlled liquid circulating through the circulation paths 71 and 72, thereby enabling smooth hydrogen release. Thus, the fuel cell system 1 can efficiently utilize the heat generated by the stack 31 to generate electricity.

[0057] By increasing the amount of air supplied to the stack 31 by the pump 33, the stack 31 can generate electricity more efficiently.

[0058] When the ambient temperature is high, it is not necessary to heat the air supplied to the stack 31 in the heat exchanger 32. In this case, the air can be brought to an appropriate temperature by circulating the first temperature-controlled liquid through the bypass passage 64. When the ambient temperature is low, the air can be heated in the heat exchanger 32 and brought to an appropriate temperature by circulating the first temperature-controlled liquid through the circulation passage 63.

[0059] By turning the heater 34 on and off according to the temperature, the air can be heated to a certain temperature range. Therefore, the air, heated to the appropriate temperature, is humidified by the humidifier 37 to the appropriate humidity. Thus, the fuel cell system 1 can supply air humidified to the appropriate humidity to the stack 31.

[0060] In the above embodiment, stack 31 is an example of the fuel cell of the present invention. Air is an example of the air of the present invention. Air supply passages 52-56 are an example of the first supply passage of the present invention. The first temperature-controlled liquid is an example of the first heat transfer medium of the present invention. Circulation passages 61-63, 65-67 are an example of the first flow passage of the present invention.

[0061] Heat exchanger 32 is an example of the first heat exchanger of the present invention. Air off-gas is an example of the air off-gas of the present invention. Air discharge passage 57 is an example of the second supply passage of the present invention. Air discharge passage 58 is an example of the third supply passage of the present invention. Heat exchanger 41 is an example of the second heat exchanger of the present invention.

[0062] MH container 21 is an example of a hydrogen storage container of the present invention. The second temperature-controlled liquid is an example of a second heat transfer medium of the present invention. Circulation paths 71 and 72 are examples of a second flow path of the present invention. Circulation paths 61 to 63 are examples of a forward flow path of the present invention. Circulation paths 65 to 67 are examples of a return flow path of the present invention.

[0063] Furthermore, the circulation route 63 is an example of the first route of the present invention. The bypass route 64 is an example of the second route of the present invention.

[0064] The present invention is not limited to the above embodiments and various modifications are possible. The fuel section 2 has three MH containers 21 as an example, but it may have one, two, or four or more. A flow path is provided that circulates from the hydrogen discharge path 82 to the hydrogen supply path 81, and the excess hydrogen off-gas discharged from the stack 31 due to the chemical reaction may be circulated again through the flow path 31B.

[0065] The control unit 5 may maintain a constant driving speed of the pump 33 so that the amount of air flowing is sufficient to heat the heater 34 to the second temperature even when the ambient temperature is low. In this case, the control unit 5 does not need to perform feedback control based on the measurement results of the measuring instrument 36.

[0066] The heat exchangers 32, 41, and 42 are not limited to plate heat exchangers; other types of heat exchangers such as shell tube or spiral heat exchangers may also be used. The pump 33 is optional, and air may be supplied to the stack 31 by natural intake. The heater 34 is optional, and the air may be sufficiently heated in the heat exchanger 32. In this case, the control unit 5 may adjust the air to the third temperature by controlling the flow rate of the first temperature-controlled liquid circulating through the heat exchanger 32 using a flow control valve or the like, based on the temperature detection result of the measuring instrument 36.

[0067] Furthermore, if a flow control valve is used instead of the bypass valve 39, the bypass passage 64 may always be used to circulate the first temperature-controlled liquid. The flow control valve may also control the amount of the first temperature-controlled liquid circulating through the circulation passage 63 according to the ambient temperature.

[0068] The humidifier 37 may generate water vapor for humidification by heating with a heater, for example, instead of being heated by an air off-gas. The diluent 38 may be omitted. In this case, the hydrogen off-gas may be released into the air and diluted with air. The thermometer 39A may not be directly connected to the bypass valve 39, but may be connected to the control unit 5, for example. In this case, the control unit 5 may compare the ambient temperature measured by the thermometer 39A with a predetermined temperature and perform control to switch the destination of the first temperature-controlled liquid delivered by the bypass valve 39 to the first or second path.

[0069] The control unit 5 switched the heater 34 on and off using feedback control based on the measurement results from the thermometer. A thermistor may be used instead of a thermometer. In this case, the switch 35 may not switch the heater 34 on and off according to the control unit 5, but rather control the magnitude of the current supplied to the heater 34 according to the resistance value of the thermistor. That is, by controlling the amount of current supplied to the heater 34 according to the air temperature, the switch 35 can efficiently heat the air to the second temperature while suppressing power consumption.

[0070] The heated air off gas in the stack 31 may be circulated through the heat exchanger 32 to heat the air introduced from the outside. Alternatively, the heated air off gas in the stack 31 may be circulated through the heat exchanger 41 to heat the second temperature-controlled liquid. Or, the heated air off gas in the stack 31 may be circulated through the temperature-controlled member 23 to heat the MH container 21. [Explanation of symbols]

[0071] 1. Fuel cell system 4. Electrical load 21 MH container 31 stacks 32,41,42 Heat exchanger 33 pumps 34 Heater 35 switches 37 Humidifier 38 Diluter 39 Bypass valve 52-56 Air supply path 57, 58 Air exhaust channel 61~63,65~67,71~74 Circulation path 64 Bypass

Claims

1. A fuel cell that generates electricity by reacting hydrogen and oxygen and can supply power to an electrical load, A first supply path for supplying oxygen-containing air introduced from the outside to the fuel cell, A first flow passage through which a first heat transfer medium, which is a heat transfer medium for heat exchange, A first heat exchanger that exchanges heat between the first heat transfer medium flowing through the first flow passage and the air introduced into the first supply passage, A heater that heats the air that has passed through the first heat exchanger, A humidifier that humidifies the air heated by the heater, A fuel cell system characterized by having the following features.

2. The first flow path is a flow path through which the first heat transfer medium circulates between the fuel cell and the first heat exchanger. The first heat transfer medium is heated by the heat generated by the fuel cell, flows through the first flow passage, and heats the air in the first heat exchanger. A fuel cell system according to claim 1, characterized by the following:

3. The system includes a second supply path for supplying air off-gas, which is air discharged from the fuel cell, to the humidifier. The humidifier humidifies the air by utilizing the heat of the air off-gas heated by the heat generated by the fuel cell. A fuel cell system according to claim 1 or 2, characterized by the above.

4. A diluent for diluting hydrogen contained in the hydrogen off-gas discharged from the fuel cell, A third supply channel supplies the air off-gas that has passed through the humidifier to the diluent. Equipped with, The diluent dilutes hydrogen with the air off-gas that has passed through the humidifier. The fuel cell system according to claim 3, characterized by the following:

5. A second heat exchanger connected to the first flow passage through which the first heat medium that has passed through the first heat exchanger flows, A second flow passage through which the second heat transfer medium circulates between the second heat exchanger and the hydrogen storage container for storing hydrogen. Equipped with, The hydrogen storage container includes a hydrogen storage alloy that releases the hydrogen through an endothermic reaction. The second heat transfer medium is heated in the second heat exchanger by heat exchange with the first heat transfer medium, flows through the second flow passage, and heats the hydrogen storage container. The fuel cell system according to claim 2, characterized by the following:

6. In the first supply path, a pump is provided between the first heat exchanger and the heater to send the air flowing through the first supply path toward the fuel cell. A fuel cell system according to claim 1 or 2, characterized by the above.

7. The first flow path includes a forward path from the fuel cell to the first heat exchanger and a return path from the first heat exchanger to the fuel cell. A bypass path connects the forward path and the return path without passing through the first heat exchanger, A bypass valve is positioned in the forward path and switches the path of the first heat transfer medium to either a first path that goes from the forward path through the first heat exchanger to the return path, or a second path that goes from the forward path through the bypass path to the return path. The fuel cell system according to claim 2, characterized by comprising:

8. The heater is provided with a switch that turns it on and off according to the temperature of the air flowing through the first supply path. A fuel cell system according to claim 1 or 2, characterized by the above.

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