JP2005222840A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly warm up an electrode surface of a fuel cell without installing piping or a valve for supplying fuel gas to a cathode. <P>SOLUTION: An outside DC power source device 17 is connected to a fuel cell body 2 through a shut off switch 16. When warming-up of the fuel cell body 2 is required, a controller 15 supplies hydrogen to an anode 3, and at the same time, turns on the shut off switch 16, and supplies current from a positive electrode of the outside DC power source device 17 to the anode 3 of the fuel cell body 2. Hydrogen ionized in the anode 3 reaches a cathode having negative potential, and is re-combined with an electron to form hydrogen. The hydrogen causes burning reaction with oxygen in air and temperature of the fuel cell body 2 is raised. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system including a solid polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte, and particularly suitable for a mobile body such as a vehicle, a ship, and a portable generator. About.

  In general, a fuel cell is a power generator that directly converts chemical energy of a fuel into electrical energy by electrochemically reacting a fuel gas such as hydrogen with an oxidant gas such as air. The fuel cells are classified into various types depending on the difference in electrolytes. As one of them, a solid polymer electrolyte fuel cell using a solid polymer electrolyte as an electrolyte is known.

  The electrode reactions that proceed at the anode and cathode electrodes of the solid polymer electrolyte fuel cell are as follows.

Anode (fuel electrode): 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Cathode (oxidant electrode): 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)
When hydrogen gas is supplied to the anode, the reaction formula (1) proceeds at the anode to generate hydrogen ions and electrons. The generated hydrogen ions permeate (diffuse) through the electrolyte (in the case of a solid polymer electrolyte fuel cell, a solid polymer electrolyte membrane) in a hydrated state and reach the cathode. On the other hand, electrons reach the cathode from the anode through the external load device. When an oxygen-containing gas such as air is supplied to the cathode, the reaction formula (2) proceeds at the cathode. When the electrode reactions (1) and (2) proceed at each electrode, the fuel cell generates an electromotive force. Here, in order for hydrogen ions to move through the solid polymer electrolyte, the electrolyte needs to contain water.

  However, the presence of this water causes inconvenience when the fuel cell is operated in a sub-freezing environment. The electrolyte membrane needs to contain moisture, but if excess moisture is present on the gas flow path or electrode catalyst surface and freezes, the fuel gas and oxidant gas required for power generation are supplied to the catalyst. Can not be generated. In addition, water is generated at the cathode by power generation, but when the generated water is frozen, supply of the oxidant gas is similarly hindered and power generation cannot be performed.

For this reason, in order to start the solid polymer electrolyte fuel cell from a sub-freezing environment, a method is considered in which power generation is started in a state where the temperature of the fuel cell is raised to a temperature at which power can be generated in advance. For example, Patent Document 1 proposes a method in which hydrogen gas and oxygen-containing gas are supplied to the anode and / or cathode, hydrogen and oxygen are reacted on the electrode catalyst, and the fuel cell temperature is increased by this reaction heat. ing.
JP 2001-189164 A (page 5, FIG. 1)

  However, in the method in which hydrogen gas is introduced into the cathode gas pipe or oxidant gas is introduced into the anode gas pipe and a gas mixture of hydrogen gas and oxidant gas is supplied to the electrode catalyst, both gases are introduced and mixed. Therefore, there is a problem that the configuration of the fuel cell system becomes complicated due to the need for piping, valves and the like.

  In addition, since the mixed gas is introduced from the upstream side of the gas flow path of the fuel cell, an in-plane non-uniformity occurs in which there is a large amount of hydrogen oxidation reaction in the upstream portion of the flow path and a small amount of reaction downstream, and only in the upstream portion. When the temperature rises or is extreme, there is a problem that a heat spot is generated and the function of the electrolyte membrane is impaired.

  In order to solve the above-mentioned problems, the present invention provides a fuel cell body in which an anode and a cathode are formed on both sides of a solid polymer electrolyte membrane, a fuel supply means for supplying hydrogen gas to the anode, and an oxidant gas on the cathode. And an oxidant supply means for supplying an external DC power source connected to the fuel cell main body via a cutoff switch, and the temperature of the fuel cell main body at the start of the fuel cell system When rising is required, hydrogen gas is supplied from the fuel supply means to the anode, and a positive electrode of the external DC power source is connected to the anode and a negative electrode is connected to the cathode, and the fuel is supplied from the external DC power source. The gist is to supply current to the battery body.

  According to the present invention, hydrogen or a mixed gas containing hydrogen is supplied to the fuel cell anode, the positive electrode of the external DC power supply is connected to the anode of the fuel cell, the negative electrode of the external DC power supply is connected to the cathode of the fuel cell, A current is supplied from the positive electrode to the anode of the fuel cell.

  As a result, the hydrogen supplied to the anode becomes hydrogen ions in the electrode catalyst, and the time integral value of the current value supplied from the external power source, that is, an amount of hydrogen ions sufficient to cover the amount of electricity passes through the electrolyte membrane from the anode to the cathode. Moving. The hydrogen ions that have moved to the cathode in this way react with oxygen to produce water during normal power generation of the fuel cell. In this case, an overvoltage required for the electrochemical reaction of oxygen is required, and The cathode potential needs to be kept high.

  In the present invention, the cathode potential is kept lower than that of the anode by the connection of the external DC power supply, and hydrogen ions cannot generate an electrochemical reaction with oxygen. To change. If the reaction at each of the above electrodes is expressed by an equation, equations (3) and (4) are obtained.

Anode (fuel electrode): H ₂ → 2H ⁺ + 2e ⁻ (3)
Cathode (oxidant electrode): 2H ⁺ + 2e ⁻ → H ₂ (4)
Hereinafter, the hydrogen transport from the anode to the cathode according to the present invention is referred to as an electrochemical hydrogen transport method.

  The hydrogen gas generated in this manner stays in the cathode gas flow path or exists in the vicinity of the electrode catalyst together with oxygen supplied from the oxidant supply means, so that the oxidation reaction of hydrogen by the catalyst, that is, combustion in the equation (5) Wake up.

Cathode (oxidant electrode): H ₂ + 1 / 2O ₂ → H ₂ O (5)
In this way, the fuel cell temperature rises due to the reaction heat from the combustion of hydrogen, and the fuel cell is warmed to a temperature suitable for power generation, thereby enabling power generation from a low temperature environment of the fuel cell. Here, the external DC power source can be expected not only to a battery such as a storage battery and a generator, but also to a fuel cell provided separately.

  According to the present invention, the piping of the hydrogen gas and the oxidant gas can be realized as the piping to the anode or the cathode, and there is no need to provide the gas piping to the counterpart electrode as in the prior art. There is no complication of the configuration.

  In addition, since the hydrogen ions moving from the anode to the cathode are almost uniform in the electrode surface, the temperature rise due to hydrogen combustion at the cathode is also uniform, and the temperature rises only at the upstream portion of the hydrogen gas as in the conventional case. In such a case, a problem that a heat spot is generated and the function of the electrolyte membrane is impaired is suppressed.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram illustrating the configuration of a first embodiment of a fuel cell system according to the present invention. In FIG. 1, a fuel cell system 1 includes a fuel cell main body 2 in which an anode 3 and a cathode 4 are formed on both sides of a solid polymer electrolyte, a hydrogen tank 5 that stores hydrogen gas at a high pressure, and a high-pressure hydrogen gas in a desired operation. Hydrogen pressure regulating valve 6 that is depressurized to a pressure and supplied to anode 3, hydrogen purge valve 7 that discharges hydrogen gas containing impurities from the outlet of anode 3, and hydrogen is circulated from the outlet of anode 3 to the inlet A hydrogen circulation path 8 that is a pipe line, a hydrogen circulation pump 9 that circulates hydrogen in the anode 3 and the hydrogen circulation path 8, a compressor 10 that supplies air to the cathode 4, and an outlet from the cathode 4 are discharged out of the system. An air pressure regulating valve 11 that throttles air, a load switch 12, the fuel cell main body 2 is a load device 13 that consumes generated power, and a temperature sensor that detects the temperature of the fuel cell main body 2. 4 and supplying the current from the positive electrode of the external DC power supply 17 to the anode 3 via the cutoff switch 16 while supplying the hydrogen gas from the hydrogen tank 5 to the anode 3 by controlling the hydrogen pressure regulating valve 6 before starting the fuel cell. And a controller 15 that controls the external power supply 17 and an external DC power supply 17 that is connected to the fuel cell main body via the cutoff switch 16 and that can supply current from the positive electrode to the anode 3.

  The temperature sensor 14 is temperature detecting means for detecting or estimating the temperature in or near the fuel cell main body 2 and uses the detected value as a representative temperature. The detection value of the temperature sensor 14 is input to the controller 15, and is used by the controller to determine the stop of the DC current supply from the external DC power supply device 17 to the fuel cell body 2.

  The cutoff switch 16 is a switch using a relay, a semiconductor switch, or the like that is controlled to be turned on / off by the control of the controller 15.

  The controller 15 stops the current supply from the external DC power supply device 17 to the fuel cell main body 2 by turning off the cutoff switch 16 when the representative temperature detected by the temperature sensor 14 rises to a predetermined temperature.

  The fuel cell body 2 is configured as a stack in which a necessary number of unit cells are connected in series to obtain a voltage to be supplied to the load device 13.

  FIG. 2 is a schematic cross-sectional view for explaining the reaction of the fuel cell main body at the time of starting the fuel cell system of Example 1, and shows one unit cell constituting the stack.

  The unit battery includes a polymer electrolyte membrane 20 made of a solid polymer membrane, and an anode 3 and a cathode 4 disposed on both sides of the polymer electrolyte membrane 20 so as to sandwich the polymer electrolyte membrane 20.

  The anode 3 supplies hydrogen gas to the anode catalyst layer 3c formed on one surface of the solid polymer electrolyte 20, the anode gas diffusion layer 3b formed outside the anode catalyst layer 3c, and the anode gas diffusion layer 3b. An anode gas flow path 3a which is a flow path to be operated.

  The cathode 4 supplies a hydrogen gas to the cathode catalyst layer 4c formed on the other surface of the solid polymer electrolyte 20, the cathode gas diffusion layer 4b formed outside the cathode catalyst layer 4c, and the cathode gas diffusion layer 4b. The cathode gas flow path 4a which is a flow path to be used is provided.

  The polymer electrolyte membrane 20 is formed as a proton conductive membrane from a solid polymer material such as a fluorine-based resin.

  The anode catalyst layer 3c and the cathode catalyst layer 4c disposed on both surfaces of the polymer electrolyte membrane 20 carry platinum or fine particles of an alloy of platinum and other metals (such as Pd) with carbon. For the anode gas diffusion layer 3b and the cathode gas diffusion layer 4b, a porous conductive member such as carbon paper is used.

  The anode gas channel 3a and the cathode gas channel 4a are formed by a large number of ribs arranged on one side or both sides of a dense carbon material that is impermeable to gas, respectively. Supplied from the inlet and discharged from the gas outlet.

  Hydrogen or a fuel gas that is a gas containing hydrogen is introduced into the anode 3, and an ionization reaction of hydrogen at the anode 3 occurs. The hydrogen ions generated thereby move in the polymer electrolyte membrane 20 from the anode 3 to the cathode 4, and change into hydrogen again by the reaction at the cathode 4.

  On the other hand, electrons generated from the fuel gas by the reaction at the anode pass through a circuit including an external power source and move to the cathode, thereby contributing to the reaction at the cathode.

  At this time, oxygen is also present in the vicinity of the catalyst of the cathode, but since the cathode potential is controlled to be lower than that of the anode by an external power source, an electrochemical reaction between hydrogen ions and oxygen does not occur. The reaction of the electrons and hydrogen produces a hydrogen production reaction.

  Here, since hydrogen and oxygen are present in the vicinity of the electrode catalyst, a combustion reaction occurs, and heat is generated along with the generation of water, thereby raising the temperature of the fuel cell. At this time, it is considered that Joule heat due to the current supplied from the external DC power source to the fuel cell as well as the heat of chemical reaction due to the combustion of hydrogen contributes to the temperature rise of the fuel cell.

  Therefore, ΔT is the temperature rise of the fuel cell, c is the average specific heat of the fuel cell, M is the mass of the fuel cell, n is the number of cells through which the current supplied from the external DC power source passes, and the amount of charge supplied from the external DC power source Is Q, Faraday constant is F (= elementary charge amount e × Avogadro number NA), and the heat amount of combustion heat in the standard state of hydrogen is 286 [kJ / mol], the following equation (6) is established.

c × M × ΔT = n × (Q / F) × (1/2) × 286−α + β (6)
here,
α: Heat loss (total of conduction heat, convection heat, and radiation heat from the fuel cell body)
β: The amount of heat due to Joule heat generated by the current supplied from the external DC power source to the fuel cell body.

  Hereinafter, raising the temperature of the fuel cell body 2 before starting the power generation of the fuel cell body 2 will be referred to as warming up of the fuel cell.

  FIG. 3 is a flowchart for explaining the warm-up control of the fuel cell by the controller 15 in the first embodiment. In FIG. 3, first, in step S <b> 10, the controller 15 outputs a control signal for opening an unillustrated main valve of the hydrogen tank 5 and supplies hydrogen to the hydrogen pressure regulating valve 6 at a predetermined warm-up pressure. Output a control signal. Thereby, supply of hydrogen gas to the anode 3 of the fuel cell main body 2 is started.

  Next, the controller 15 reads the detection value T of the temperature sensor 14 in step S12, and determines whether or not the detection value T of the temperature sensor is larger than the predetermined temperature value T0 in step S14. If it is determined in step S14 that the detected value T exceeds the predetermined temperature value T0, the warm-up of the fuel cell body is unnecessary, and therefore the warm-up is terminated. The predetermined temperature value T0 is a determination value of the fuel cell representative temperature for determining whether or not the fuel cell body needs to be warmed up, and is set to 1 [° C.] or 2 [° C.], for example. After the warm-up is completed, air supply to the cathode 4 from the compressor 10 is started, and power generation is started.

If it is determined in step S14 that the detected value T is equal to or less than the predetermined temperature value T0, the process proceeds to step S16, the cutoff switch 16 is turned on, and the supply of DC current from the external DC power supply device 17 to the fuel cell body 2 is started. . The polarity at this time is such that the positive electrode of the external DC power supply device 17 is connected to the anode 3 of the fuel cell main body 2 and the negative electrode of the external DC power supply device 17 is connected to the cathode 4 of the fuel cell main body 2. Current flows from the positive electrode to the anode 3. Due to this current, hydrogen ions (H ⁺ ) move in the solid polymer electrolyte membrane from the anode 3 to the cathode 4 in the fuel cell main body 2, and electrochemical hydrogen transport is performed. The hydrogen ions that have reached the cathode 4 recombine with electrons to become hydrogen, and further, the hydrogen reacts with oxygen via the electrode catalyst of the cathode 4 to become water, releases heat of reaction, and causes the fuel cell body 2 to enter the interior. Warm up.

  Next, the controller 15 reads the detection value T of the temperature sensor 14 in step S18, and determines whether or not the detection value T of the temperature sensor is larger than the predetermined temperature value T1 in step S20. The predetermined temperature value T1 for determining whether or not the warm-up is complete may be equal to the predetermined temperature value T0 used in step S14, but when the variation in temperature rise due to the portion of the fuel cell main body 2 is large, T1 is calculated from T0. It is preferable to set a large value.

  If it is determined in step S20 that the detected value T does not exceed the predetermined temperature value T1, the process returns to step S18 to continue warming up. If it is determined in step S20 that the detected value T exceeds the predetermined temperature value T1, the process proceeds to step S22, where the controller 15 turns off the cutoff switch 16, and from the external DC power supply 17 to the anode 3 of the fuel cell body 2. Stop the current supply to. Next, in step S <b> 24, the controller 15 starts supplying purge gas to the cathode 4 and discharges the water generated at the cathode 4 to the outside of the fuel cell body 2. This purge removes moisture generated by the combustion reaction and prevents gas supply hindrance and structural destruction due to refreezing.

  In the configuration of this embodiment, the controller 15 drives the compressor 10 and uses air as the purge gas. Note that a gas cylinder for storing an inert gas as a purge gas and a pipe extending from the gas cylinder to the cathode may be provided, and the inert gas may be supplied as the purge gas under the control of the controller 15.

  Next, in step S26, the controller 15 determines whether or not a predetermined time has elapsed since the supply of the purge gas was started. If the predetermined time has not elapsed, the process waits in the self-loop of S26. If predetermined time passes, it will progress to step S28 and the controller 15 will stop supply of the purge gas gas from the compressor 10, and will complete | finish warming up of the fuel cell main body 2. FIG. When purging with an inert gas in step S24, the supply of the inert gas to the cathode 4 is stopped in step S28, and the warm-up of the fuel cell body 2 is terminated.

  Here, a process diagram in which hydrogen is continuously supplied to the anode even after the supply of current by the external power supply is stopped is illustrated, but the supply of hydrogen can be stopped anytime after the supply of current is stopped. Similarly, the purge of the cathode is started after the supply of current is stopped, but the cathode may be purged during the period when the current is supplied and the combustion reaction occurs.

  As described above, according to this embodiment, there is provided temperature detecting means for detecting or estimating the representative temperature of the fuel cell main body in or near the fuel cell main body, and the representative temperature by this temperature detecting means is the power generation of the fuel cell main body. When the temperature has risen to an appropriate temperature for the start, the current supply from the positive electrode to the anode of the external DC power supply device is stopped, and the warm-up for burning hydrogen at the cathode is terminated. Thus, there is an effect that it is possible to promptly shift to normal power generation without unnecessarily increasing the temperature of the fuel cell body.

  Further, according to this embodiment, after the current supply from the external DC power supply is stopped, the purge is performed by supplying the inert gas or air to the cathode. When hydrogen is introduced into the cathode by the electrochemical hydrogen transport method, water is not generated, but in the subsequent chemical reaction with oxygen, water is generated together with heat of reaction. If this water freezes again, the supply of oxidant gas at the cathode will be hindered and power generation will not be possible, and it may cause irrecoverable performance degradation due to ice expansion during freezing. There is. Such refreezing can be prevented by quickly removing water generated by the chemical reaction by purging in this embodiment.

  FIG. 4 is a system configuration diagram illustrating the configuration of the fuel cell system according to the second embodiment of the present invention. In FIG. 4, a fuel cell system 1 includes a fuel cell main body 2 in which an anode 3 and a cathode 4 are formed on both sides of a solid polymer electrolyte, a hydrogen tank 5 for storing hydrogen gas at high pressure, and a high-pressure hydrogen gas in a desired operation. Hydrogen pressure regulating valve 6 that is depressurized to a pressure and supplied to anode 3, hydrogen purge valve 7 that discharges hydrogen gas containing impurities from the outlet of anode 3, and hydrogen is circulated from the outlet of anode 3 to the inlet A hydrogen circulation path 8 that is a pipe line, a hydrogen circulation pump 9 that circulates hydrogen in the anode 3 and the hydrogen circulation path 8, a compressor 10 that supplies air to the cathode 4, and an outlet from the cathode 4 are discharged out of the system. An air pressure regulating valve 11 that throttles air, a load switch 12, the fuel cell main body 2 is a load device 13 that consumes generated power, and a temperature sensor that detects the temperature of the fuel cell main body 2. 4 and supplying the current from the positive electrode of the external DC power supply 17 to the anode 3 via the cutoff switch 16 while supplying the hydrogen gas from the hydrogen tank 5 to the anode 3 by controlling the hydrogen pressure regulating valve 6 before starting the fuel cell. A controller 15 for controlling the external power supply, an external DC power supply device 17 connected to the fuel cell main body via the cutoff switch 16 and capable of supplying current from the positive electrode to the anode 3, and supplied from the external DC power supply device 17 to the fuel cell main body 2. An ammeter 18 that detects and outputs the current value to the controller 15 is provided.

  The temperature sensor 14 is temperature detecting means for detecting or estimating the temperature in or near the fuel cell main body 2 and uses the detected value as a representative temperature. The detection value of the temperature sensor 14 is input to the controller 15.

  The current value detected by the ammeter 18 is input to the controller 15, and integration approximation is performed by the controller 15 by time integration or integration at regular intervals, and the electric power supplied from the external DC power supply device 17 to the fuel cell main body 2. The quantity (charge quantity) is calculated. The controller 15 determines the stop of the current supplied from the external DC power supply device 17 to the fuel cell main body 2 based on the amount of electricity thus calculated.

  The cutoff switch 16 is a switch using a relay, a semiconductor switch, or the like that is controlled to be turned on / off by the control of the controller 15.

  The controller 15 stops the current supply from the external DC power supply device 17 to the fuel cell main body 2 by turning off the cutoff switch 16 when the representative temperature detected by the temperature sensor 14 rises to a predetermined temperature.

  The fuel cell body 2 is configured as a stack in which a necessary number of unit cells are connected in series to obtain a voltage to be supplied to the load device 13.

  FIG. 5 is a flowchart for explaining the warm-up control of the fuel cell by the controller 15 in the second embodiment. In FIG. 5, the controller 15 first reads the detection value T of the temperature sensor 14 in step S40, and determines whether or not the detection value T of the temperature sensor is larger than the predetermined temperature value T0 in step S42. If it is determined in step S42 that the temperature detection value T exceeds the predetermined temperature value T0, it is not necessary to warm up the fuel cell body, so the warming up is terminated. The predetermined temperature value T0 is a determination value of the fuel cell representative temperature for determining whether or not the fuel cell body needs to be warmed up, and is set to 1 [° C.] or 2 [° C.], for example. After the warm-up is completed, air supply to the cathode 4 from the compressor 10 is started, and power generation is started.

  If it is determined in step S42 that the detected temperature value T is equal to or lower than the predetermined temperature value T0, the process proceeds to step S44, and the controller 15 calculates the amount of electricity Qr required for warming up the fuel cell body 2 based on the detected temperature value T. calculate. The required amount of electricity Qr supplied from the external DC power supply device 17 for warming up the fuel cell body 2 increases the temperature of the fuel cell from the fuel cell temperature T detected in step S40 to a predetermined temperature, for example, 1 [° C.]. If the temperature rise is ΔT, the following equation (7) is derived from the equation (6) described in the first embodiment.

Qr = (2/286) (F / n) (c × M × ΔT + α−β) (7)
here,
ΔT: Required temperature rise of fuel cell c: Average specific heat of fuel cell M: Mass of fuel cell n: Number of cells through which current supplied from external DC power supply passes F: Faraday constant α: Heat loss (from fuel cell main body Total of conduction heat, convection heat, and radiant heat)
β: The amount of heat due to Joule heat generated by the current supplied from the external DC power source to the fuel cell body.

  Since α and β are related to the time required for the temperature rise of ΔT, Qr may be calculated using an approximate function of α and β obtained experimentally.

  If there is no large variation in the approximate value of the current value supplied from the external DC power supply, Qr may be obtained using a map of the necessary amount of electricity Qr with respect to the temperature detection value T before start obtained experimentally. .

  Next, in step S46, the controller 15 outputs a control signal for opening a main valve (not shown) of the hydrogen tank 5 and outputs a control signal to supply hydrogen to the hydrogen pressure regulating valve 6 at a predetermined warm-up pressure. Output. Thereby, supply of hydrogen gas to the anode 3 of the fuel cell main body 2 is started.

In step S <b> 48, the controller 15 turns on the cutoff switch 16 and starts supplying a direct current from the external DC power supply device 17 to the fuel cell body 2. The polarity at this time is such that the positive electrode of the external DC power supply device 17 is connected to the anode 3 of the fuel cell main body 2 and the negative electrode of the external DC power supply device 17 is connected to the cathode 4 of the fuel cell main body 2. Current flows from the positive electrode to the anode 3. Due to this current, hydrogen ions (H ⁺ ) move in the solid polymer electrolyte membrane from the anode 3 to the cathode 4 in the fuel cell main body 2, and electrochemical hydrogen transport is performed. The hydrogen ions that have reached the cathode 4 recombine with electrons to become hydrogen, and further, the hydrogen reacts with oxygen via the electrode catalyst of the cathode 4 to become water, releases heat of reaction, and causes the fuel cell body 2 to enter the interior. Warm up.

  Next, in step S50, the controller 15 reads the current value i detected by the ammeter 18, and in step S52, the controller 15 integrates the current value i over time and supplies it to the fuel cell body 2 from the external DC power supply 17 so far. The amount of electricity supplied Qs is calculated. This time integration is actually performed by integrating current values for each sample time.

  In step S54, it is determined whether the supplied electricity amount Qs is larger than the necessary electricity amount Qr. If it is determined in step S54 that the supplied electricity quantity Qs does not exceed the required electricity quantity Qr, the process returns to step S50 to continue the warm-up. If it is determined in step S54 that the supplied electric quantity Qs exceeds the necessary electric quantity Qr, the process proceeds to step S56, where the controller 15 turns off the cutoff switch 16 and the anode of the fuel cell main body 2 from the external DC power supply device 17. The current supply to 3 is stopped. Next, in step S <b> 58, the controller 15 starts supplying purge gas to the cathode 4 and discharges water generated at the cathode 4 to the outside of the fuel cell main body 2. This purge removes moisture generated by the combustion reaction and prevents gas supply hindrance and structural destruction due to refreezing.

  In the configuration of this embodiment, the controller 15 drives the compressor 10 and uses air as the purge gas. Note that a gas cylinder for storing an inert gas as a purge gas and a pipe extending from the gas cylinder to the cathode may be provided, and the inert gas may be supplied as the purge gas under the control of the controller 15.

  Next, in step S60, the controller 15 determines whether or not a predetermined time has elapsed since the supply of the purge gas was started. If the predetermined time has not elapsed, the process waits in the self-loop of S60. If predetermined time passes, it will progress to step S62 and the controller 15 will stop supply of the purge gas gas from the compressor 10, and will complete | finish warming up of the fuel cell main body 2. FIG. When purging with an inert gas in step S58, the supply of the inert gas to the cathode 4 is stopped in step S62, and the warm-up of the fuel cell body 2 is terminated.

  Here, a process diagram in which hydrogen is continuously supplied to the anode even after the supply of current by the external power supply is stopped is illustrated, but the supply of hydrogen can be stopped anytime after the supply of current is stopped. Similarly, the purge of the cathode is started after the supply of current is stopped, but the cathode may be purged during the period when the current is supplied and the combustion reaction occurs.

  FIG. 6 is an example of a map for calculating the required amount of electricity Qr with respect to the temperature at the start of the fuel cell body 2 (before warming up). When the starting temperature is less than a predetermined temperature Tc (for example, Tc = 1 [° C.]), warm-up is performed. As shown in FIG. 6, as the starting temperature is lower, the amount of heat required to raise the fuel cell temperature to a predetermined temperature increases, and accordingly, the necessary amount of electricity to be supplied from the external DC power source. Qr will also increase. The fuel cell temperature is raised by electrochemical hydrogen transport and subsequent combustion, but the required amount of electricity Qr is calculated by comparing the amount of electricity supplied Qs obtained by the means for estimating the amount of electricity with the amount of electricity Qr calculated in advance. When the supplied electricity amount Qs exceeds, the current supply from the external DC power supply device is stopped, and normal power generation is started.

  According to the present embodiment, the electric quantity detecting means for detecting or estimating the electric quantity supplied to the fuel cell main body from the external DC power supply device is provided, and the end time of the electrochemical hydrogen transport method is determined based on the electric quantity information. . The temperature rise of the fuel cell body is determined by the amount of hydrogen-oxygen reaction heat at the cathode, and this amount of reaction heat depends on the amount of hydrogen introduced into the cathode and the number of hydrogen ions transferred from the anode to the cathode through the electrolyte membrane. Determined. That is, it is determined by the amount of electricity represented by the product of the current supplied to the fuel cell and its time. Therefore, by determining the end time based on the information from the electric quantity detection means, it is possible to minimize the hydrogen consumption and raise the fuel cell temperature to a temperature suitable for power generation.

  Further, according to the present embodiment, the temperature detecting means for detecting or estimating the representative temperature of the fuel cell in or near the fuel cell main body is provided, and the temperature of the fuel cell is calculated from the temperature information before the electrochemical hydrogen transport method is performed. By calculating the amount of electricity required to increase the value to an appropriate value and supplying this amount of electricity, it is possible to realize a more efficient increase in the fuel cell temperature.

  FIG. 7 is a main part configuration diagram for explaining the configuration of the fuel cell system according to the third embodiment of the present invention. Example 3 is an example in which a current is supplied from an external DC power supply to a unit battery (cell) at an end of a fuel cell stack or a part of unit batteries including the end unit battery.

  In the stacked fuel cells, the unit cells located at or near the ends tend to dissipate heat to the outside, so that the temperature tends to be lower than the unit cells located at the center. Therefore, in a sub-freezing environment, the generated water may freeze in the unit cell at the end and the supply of the oxidant gas may be hindered, and it is desirable to quickly raise the temperature to prevent the generated water from freezing.

  In the present embodiment, as shown in FIG. 7, an external DC power source is connected to the left end unit cell 32 and the right end unit cell 33 of the fuel cell stack 31 via cut-off switches 38 and 39, respectively. Devices 36 and 37 are connectable.

  The anode 32 a of the leftmost end unit cell 32 of the fuel cell stack 31 is an electrode common to the anode 3 of the fuel cell stack 31, and the positive electrode of the external DC power supply device 36 is connected to the anode 3 via a cutoff switch 38. It is connected. An auxiliary electrode 34 is provided between the cathode 32 b of the end unit cell 32 and the anode of the unit cell adjacent thereto, and the negative electrode of the external DC power supply device 36 is connected to the auxiliary electrode 34.

  Similarly, an auxiliary electrode 35 is provided between the anode 33 a of the rightmost end unit cell 33 of the fuel cell stack 31 and the cathode of the unit cell adjacent thereto, and a cutoff switch 39 is connected to the auxiliary electrode 35. The positive electrode of the external DC power supply device 37 is connected via The cathode 33 b of the end unit cell 33 is an electrode common to the cathode 4 of the fuel cell stack 31, and the negative electrode of the external DC power supply device 37 is connected to the cathode 4. Other fuel cell accessories include the same components as in FIG. 1 or FIG. 4, but are not shown in FIG. 7.

  When the fuel cell stack 31 is warmed up, control is performed to supply current from the external DC power supply devices 36 and 37 to the end unit cells 32 and 33 of the fuel cell stack 31 by controlling the cutoff switches 38 and 39 from a controller (not shown). The contents are the same as those in the first or second embodiment.

  In the present embodiment, the current is supplied from the external DC power supply to the outermost unit cell located on the outermost side of the fuel cell stack. A plurality of end unit batteries including the battery may be configured to supply current from an external DC power supply device.

  According to this embodiment, the unit cell located at the end of the stacked fuel cell stack, or several unit cell groups including the end unit cell, the electrochemical hydrogen transport method and the subsequent reaction heat Increase the temperature by In a stacked fuel cell, the unit cell located at or near the end is lower in temperature than the unit cell located in the center due to the dissipation of heat to the outside world. Easy to freeze. Therefore, it is possible to prevent the generated water from freezing by raising the temperature of the end unit battery. Furthermore, compared to the case where the electrochemical hydrogen transport method is performed on all unit cells of the stacked fuel cells, the amount of hydrogen consumed is small, and the applied voltage applied to the fuel cell body from the external DC power supply device is also small. The advantage is that

  FIG. 8 is a schematic cross-sectional view for explaining the reaction of the fuel cell main body at the time of starting the fuel cell system of Example 4, and shows one unit cell constituting the stack.

  In FIG. 8, the fuel cell includes a hydrogen oxidation catalyst 21 in a region other than the electrode, for example, the cathode gas flow channel surface. Other configurations are the same as those in the schematic diagram shown in FIG. 2 of the first embodiment, and thus the same components are denoted by the same reference numerals and redundant description is omitted.

  As the hydrogen oxidation catalyst 21, for example, a fine powder such as platinum (Pt) or an alloy of platinum and palladium (Pd) is supported on a porous material such as carbon or ceramic.

  According to the present embodiment, hydrogen that has passed without being oxidized by the electrode catalyst is burned and generated by the hydrogen oxidation catalyst 21 provided in the other region, and a more efficient temperature rise can be realized. Although only the application of the catalyst to the flow path surface is described here, the same effect can be obtained by applying the fine powder to another region, for example, the gas diffusion layer with an appropriate solvent.

1 is a system configuration diagram illustrating the configuration of a first embodiment of a fuel cell system according to the present invention. FIG. It is a schematic cross section explaining reaction of the fuel cell main body at the time of starting of the fuel cell system of Example 1, and shows one unit cell which constitutes a stack. 3 is a flowchart illustrating fuel cell warm-up control by a controller 15 according to the first embodiment. It is a system block diagram explaining the structure of Example 2 of the fuel cell system which concerns on this invention. 6 is a flowchart illustrating fuel cell warm-up control by a controller 15 according to a second embodiment. 7 is a map example showing a relationship of a required amount of electricity Qr with respect to a fuel cell temperature at start-up in Example 2. It is a principal part block diagram explaining the structure of Example 3 of the fuel cell system which concerns on this invention. It is a schematic cross section explaining the reaction of the fuel cell main body at the time of starting the fuel cell system of Example 4, and shows one unit cell constituting the stack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Fuel cell main body 3 ... Anode 4 ... Cathode 5 ... Hydrogen tank 6 ... Hydrogen pressure adjustment valve 7 ... Hydrogen purge valve 8 ... Hydrogen circulation path 9 ... Hydrogen circulation pump 10 ... Compressor 11 ... Air pressure adjustment valve DESCRIPTION OF SYMBOLS 12 ... Load switch 13 ... Load apparatus 14 ... Temperature sensor 15 ... Controller 16 ... Cutoff switch 17 ... External DC power supply device 18 ... Ammeter

Claims (7)

A fuel cell body in which an anode and a cathode are formed on both sides of a solid polymer electrolyte membrane;
Fuel supply means for supplying hydrogen gas to the anode;
An oxidant supply means for supplying an oxidant gas to the cathode;
In a fuel cell system comprising:
An external DC power source connected to the fuel cell body via a cutoff switch;
When the temperature of the fuel cell main body needs to be increased at the time of starting the fuel cell system, hydrogen gas is supplied from the fuel supply means to the anode, the positive electrode of the external DC power source is the anode, and the negative electrode is the negative electrode. A fuel cell system, characterized in that a current is supplied to the fuel cell main body from the external DC power source connected to each cathode. Temperature detecting means for detecting or estimating the temperature in or near the fuel cell main body,
2. The fuel cell system according to claim 1, wherein when the temperature value detected or estimated by the temperature detection means rises to a predetermined value, the current supply from the external DC power source to the fuel cell main body is stopped. An electric quantity detecting means for detecting or estimating an electric quantity supplied to the fuel cell main body from the external DC power source;
2. The fuel cell system according to claim 1, wherein when the amount of electricity detected or estimated by the amount of electricity detection means reaches a set value, the current supply from the external DC power supply is stopped. Temperature detecting means for detecting or estimating the temperature in or near the fuel cell body; and
Before starting the current supply from the external DC power supply, the required electric quantity calculating means for calculating the set value based on the temperature value detected or estimated by the temperature detecting means,
The fuel cell system according to claim 3, further comprising:   The fuel cell system according to any one of claims 1 to 4, wherein after the current supply is stopped, air or an inert gas is supplied to the cathode to perform a purge. The fuel cell body is a fuel cell stack in which a plurality of unit cells are stacked,
6. A current is supplied from the external DC power source to an end unit cell located at an end of the fuel cell stack or a part of unit cells including the end unit cell. The fuel cell system according to any one of the above.   7. The fuel cell system according to claim 1, further comprising a hydrogen oxidation catalyst in a region other than the electrode catalyst of the fuel cell main body.

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