JP5774403B2 - Fuel cell system and operation method thereof - Google Patents

Description

  Embodiments described herein relate generally to a fuel cell system and an operation method thereof.

  The fuel cell system includes a fuel cell including a pair of catalyst electrodes provided with an electrolyte interposed therebetween. Power generation by a fuel cell system generally supplies a hydrogen-containing gas to the fuel electrode of the fuel cell, supplies oxidant air to the oxidant electrode, and places an external load between the fuel electrode and the oxidant electrode. This is done by connecting. On the other hand, the stoppage of power generation generally stops the supply of hydrogen-containing gas and air simultaneously with the stop of the external load.

  The catalyst layer of the oxidant electrode is composed of a catalyst such as platinum and carbon that supports the catalyst. When the potential of the oxidant electrode rises to a high potential, the catalyst layer of the oxidant electrode corrodes, the catalyst activity decreases and the oxygen diffusion performance in the oxidant electrode decreases, and the fuel cell deteriorates.

  In the power generation of the fuel cell system, in starting and stopping and storing the power generation, it is likely that a current does not sufficiently flow between the oxidant electrode and the fuel electrode, and oxygen in the oxidant electrode is not sufficiently consumed. The pole is likely to have a high potential.

  In the fuel cell system, when the stack voltage falls below a predetermined voltage, the booster for auxiliary power cannot be boosted. In addition, the inverter that supplies power to the grid also has a minimum operating stack voltage. Therefore, when power generation is stopped, oxygen in the space communicating with the oxidizer electrode cannot be consumed sufficiently only by the inverter output and auxiliary machine power.

  When power is output from the fuel cell stack, the number of hydrogen molecules present in the space communicating with the fuel electrode is more than twice as large as the number of electrons (output current) (Formula 1 and Formula 2). In order to consume oxygen, it is better to output more current than to output more electric power, which is the integration of voltage and current (Equations 1 and 2).

Formula 1 H ₂ → 2H ⁺ + 2e ⁻ (fuel electrode)
Formula 2 O ₂ + 4H ⁺ + 4e → 2H ₂ O (oxidizer electrode)
If there is no hydrogen more than twice, if an electric current is taken out by the inverter output or auxiliary power, the electrode of the fuel cell is corroded and the fuel cell is greatly deteriorated.

JP 2007-109529 A

  The problem to be solved by the present invention is to provide a fuel cell system capable of suppressing deterioration of the fuel cell and an operation method thereof.

The fuel cell system according to the embodiment includes a fuel cell stack in which unit cells including a fuel electrode and an oxidant electrode are stacked, a hydrogen supply means for supplying a hydrogen-containing gas to the fuel electrode, and an oxidant electrode. An oxygen supply means for supplying an oxygen-containing gas; a power adjustment means for adjusting the power output from the fuel cell stack; a resistor and a switch; and when the switch is closed, Forming a current path for passing a current between the resistor and the oxidant electrode, and sealing a space communicating with the oxidant electrode and power consuming means for consuming power by the resistor In order to stop the power output from the oxidant electrode sealing means and the fuel cell stack, the oxygen supply means is stopped, and then the space communicating with the oxidant electrode is sealed by the oxidant electrode sealing means. Shi Control means including closing the switch and then performing control for stopping the power adjustment means, wherein the power adjustment means is an inverter output for outputting power to a power system. And an auxiliary machine power supply means for supplying electric power to the hydrogen supply means, and the control means includes: an inverter output means and an auxiliary power supply means for stopping the power adjustment means. Either one stops first.

An operation method of the fuel cell system of the embodiment includes a fuel cell stack formed by stacking unit cells including a fuel electrode and an oxidant electrode, a hydrogen supply means for supplying a hydrogen-containing gas to the fuel electrode, and the oxidation An oxygen supply means for supplying an oxygen-containing gas to the agent electrode, a power adjustment means for adjusting the power output from the fuel cell stack, a resistor and a switch, and when the switch is closed, A current path is formed between the fuel electrode, the resistor, and the oxidizer electrode, and a power consuming means for consuming power by the resistor and a space communicating with the oxidizer electrode are sealed. An oxidizer electrode sealing means for performing the operation, wherein the power adjustment means is an inverter output means for outputting power to an electric power system, and an auxiliary power supply means for supplying power to the hydrogen supply means. Tool An operation method for stopping the electric power output from the fuel cell stack includes the step of stopping the oxygen supply means, and then the oxidant electrode sealing means. Including the steps of sealing the space communicating with the oxidant electrode, then closing the switch, and then stopping the power adjustment means, wherein the power adjustment means is stopped, Either the inverter output means or the auxiliary power supply means is stopped first.

1 is a schematic configuration diagram illustrating a fuel cell system according to a first embodiment. It is a flowchart for demonstrating the operating method of the fuel cell system of 1st Embodiment. It is a figure for demonstrating the cell voltage behavior of the fuel cell of embodiment. It is a figure which shows an example of the cell voltage behavior of a fuel cell at the time of performing electric power output stop and resistance connection simultaneously. It is a schematic block diagram which shows the fuel cell system of 2nd Embodiment. It is a flowchart for demonstrating the operating method of the fuel cell system of 2nd Embodiment. It is a flowchart for demonstrating the operating method of the fuel cell system of 3rd Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a fuel cell system of the present embodiment.

The fuel cell system 100 of the present embodiment is
A fuel cell stack 3 formed by stacking unit cells each including a fuel electrode 1 and an oxidant electrode 2;
A hydrogen supply device 4 for supplying a hydrogen-containing gas to the fuel electrode 1;
An oxidant supply device 5 for supplying an oxidant gas to the oxidant electrode 2;
A power adjustment mechanism 6 for adjusting the power output from the fuel cell stack 3;
A resistor 7 and a switch 8 are provided, and when the switch 8 is closed, a current path is formed between the fuel electrode 1, the resistor 7, and the oxidant electrode 2, and power is consumed by the resistor 7. Power consumption mechanism 9 for
An oxidant electrode sealing valve 10 for sealing a space communicating with the oxidant electrode 2;
A hydrogen supply device 4, an oxidant supply device 5, a power adjustment mechanism 6, a switch 8, and a control device 11 for controlling the operation of the oxidant electrode sealing valve 10.

  The power adjustment mechanism 6 includes an auxiliary power supply device 12 that outputs electric power (auxiliary power) to the hydrogen supply device 4, an inverter output device (power conversion means) 13 that outputs electric power to the system, and a reverse that consumes electric power. And a tide prevention device 14.

  The control device 11 stops the oxidant supply device 5 (supply of oxidant gas to the oxidant electrode 2) in order to stop the power output from the fuel cell stack 3, and then the oxidant electrode sealing valve 10. This includes sealing the space communicating with the oxidant electrode 2 (stopping oxygen supply), then closing the switch 8 and then performing control for stopping the power adjustment mechanism 6.

  When the resistor 7 is connected between the fuel electrode 1 and the oxidant electrode 2 and the fuel electrode 1 and the oxidant electrode 2 are electrically connected, the hydrogen in the fuel electrode 1 moves to the oxidant electrode 2. The electrolyte sandwiched between the fuel electrode 1 and the oxidant electrode 2 not only passes through and reaches hydrogen but can also reach in the form of protons, and can consume oxygen electrochemically. Yes (see Equations 1 and 2 above).

  Therefore, when the resistor 7 is connected and the fuel electrode 1 and the oxidant electrode 2 are electrically connected, the fuel electrode 1 and the oxidant electrode 2 are not electrically connected, and the permeation through the electrolyte is performed. Compared to the case where only hydrogen can move (see Equation 3 below), oxygen consumption is faster.

Formula 3 H ₂ + 1 / 2O ₂ = H ₂ O
Therefore, as in this embodiment, the supply of oxygen is stopped, the space communicating with the oxidant electrode 2 is sealed, and then the fuel electrode 1 and the oxidant electrode 2 are connected by the resistor 7 to consume power. As a result, an increase in the potential of the oxidant electrode 2 is suppressed, and the oxidant electrode 2 is prevented from becoming a high potential.

  Immediately after the supply of oxygen to the oxidant electrode 2 is stopped, the external load is stopped without sufficiently consuming oxygen in the space communicating with the oxidant electrode 2, and the fuel electrode 1 and the oxidant electrode 2 are resisted. 7, when the oxygen of the oxidant electrode 2 is consumed, the potential increase of the oxidant electrode 2 is faster than the consumption of oxygen by the resistor 7, and the oxidant electrode 2 may be at a high potential.

In FIG. 1, 15 is a hydrogen-containing fuel supply device for supplying a hydrogen-containing fuel (for example, CH ₄ ) to the hydrogen supply device 4, 16 is a fuel system pipe for connecting the hydrogen supply device 4 and the fuel electrode 1, Reference numeral 17 denotes an oxidant piping for connecting the oxidant electrode sealing valve 10 and the oxidant electrode 2, 18 a voltmeter for measuring the voltage of the fuel cell stack 3, 20 a fuel electrode manifold, and 21 an oxidant. The pole manifold is shown. The voltmeter 18 is controlled by the control device 11. Here, the hydrogen supply device 4 is a reformer that reforms a hydrogen-containing fuel (for example, CH ₄ ) into a hydrogen-containing gas.

The fuel cell system 100 outputs power from the fuel cell stack 3 by the power adjustment mechanism 6 during power generation. The backflow prevention device 14 includes, for example, an energizing heater. The oxidant supply device 5 includes, for example, an air blower, and the hydrogen supply device 4 includes, for example, a reformer. When the reformer is included, the hydrogen supply device 4 reforms the hydrogen-containing fuel (for example, CH ₄ ) supplied by the hydrogen-containing fuel supply device 15 to generate a hydrogen-containing gas.

  The fuel cell stack 3 is connected to an inverter output device 13. The inverter output device 13 consumes the electric power generated by the fuel cell stack 3. For example, when the fuel cell system 100 is mounted on a vehicle, the inverter output device 13 corresponds to an electric motor that drives wheels.

  The control device 11 functions as a control center that controls the operation of the fuel cell system 100, and includes a CPU, a storage device, an input / output device, and the like necessary for a computer that controls various operation processes based on a program, for example. Etc.

  The control device 11 reads signals from each sensor (not shown) in the fuel cell system 100, and based on the read various signals and control logic (program) stored in advance in advance, the hydrogen supply device 4, the oxidant supply A command is sent to each component including the device 5, and all operations necessary for operation / stop of the fuel cell system 100 are integrated and controlled. The control logic included in the control device 11 includes control logic using elapsed time.

  For example, the control device 11 detects the demand power, and supplies hydrogen so that the power corresponding to the demand power including the power (auxiliary power) for moving the hydrogen supply device 4 and the oxidant supply device 5 can be generated. The device 4 supplies hydrogen, the oxidant supply device 5 supplies oxidant gas (for example, air) to the fuel cell stack 3, and the inverter output device 13 outputs demand power to the power system 19.

  Although not shown here for simplification, the fuel cell system 100 may include an oxidizing gas discharge mechanism. Further, the oxidant electrode sealing valve 10 including the discharge mechanism seals the oxidant electrode 2. Further, a mechanism for discharging the hydrogen-containing gas may be provided.

  The fuel cell system 100 may supply power to the outside of the fuel cell system such as a secondary battery instead of the power system 19. The auxiliary machine power supply device 12 may supply electric power (auxiliary power) to the oxygen agent supply device 4. The backflow prevention device 14 may supply power to auxiliary equipment such as the hydrogen supply device 4. The voltage monitoring may be a cell voltage or a block voltage instead of the stack voltage.

  In addition, although the electric power which performs inverter output to the electric power grid | system 19 exists in the fuel cell stack 3, when electric power for demand is less than it, electric power is supplied to the backflow prevention apparatus 14, and the fuel cell system 100 inside Power consumption.

  FIG. 2 is a flowchart for explaining an operation method of the fuel cell system 100 of the present embodiment. Each step is performed based on a command from the control device 11.

[Step S1]
An oxidant gas is supplied to the oxidant electrode 2 by the oxidant supply device 5, a hydrogen-containing gas is supplied to the fuel electrode 1 by the hydrogen supply device 4, and the required power is supplied to the power system by the power adjustment mechanism 6. 19 is output.

[Step S2]
When the stop of the power output is started, first, the power output to the system power 18 is lowered to a predetermined minimum value (set minimum value). Accordingly, the supply amount of the hydrogen-containing gas from the hydrogen supply device 4 to the fuel electrode 1 is reduced, and the power supplied from the auxiliary power supply device 12 to the hydrogen supply device 4 is reduced. The set minimum value is, for example, the minimum voltage required for generating a hydrogen-containing hydrogen-containing gas by the reformer.

[Step S3]
The oxidant supply device 5 is stopped, the supply of the oxidant is stopped, and the oxidant electrode 2 is sealed by the oxidant electrode sealing valve 10.

[Step S4]
The switch 8 is closed to form a current path for passing a current between the fuel electrode 1, the resistor 7, and the oxidant electrode 2. As a result, the electric power generated in the fuel cell stack 3 is consumed by the resistor 7 and consumption of oxygen remaining in the oxidant electrode 2 is started.

[Step S5]
It is determined whether or not the stack voltage is lower than a predetermined voltage Vc1. The voltage Vc1 is, for example, the lowest stack voltage at which inverter output can be performed.

[Step S6]
When the determination result in step S5 is Yes (stack voltage <Vc1), the inverter output device 13 is stopped. The determination in step S5 is repeated until Yes.

[Step S7]
When the inverter output stops, it is determined whether or not the stack voltage is lower than Vc2 (<Vc1). Vc2 is, for example, a stack voltage corresponding to a cell voltage of 0.6V.

[Step S8]
If the determination result in step S7 is Yes (stack voltage <Vc2), the auxiliary machine power supply device 12 (supply of auxiliary machine power) is stopped. As a result, power (oxygen) is consumed only by the resistor 7. The determination in step S7 is repeated until Yes. The voltage Vc2 is, for example, the minimum stack voltage necessary for the auxiliary machine power supply device 12 to supply auxiliary machine power.

  According to this embodiment, since the level of the stack voltage is evaluated in steps S5 and S7, it can be determined whether or not the fuel cell is deficient in hydrogen, and cell deterioration due to deficiency in hydrogen can be prevented.

  That is, if it is determined that the stack voltage has reached the minimum stack voltage Vc1 at which inverter output is possible (step S5), the inverter output is stopped, oxygen is consumed by the auxiliary power supply device 12 and the resistor 7, and the stack voltage is further increased. Is determined to have reached the minimum stack voltage Vc2 required for supplying auxiliary power (step S7), the auxiliary power supply device 12 is stopped and oxygen is consumed only by the resistor 7.

  The effect of this embodiment will be further described.

  In steps S5 to S7, oxygen is sufficiently consumed by the power output and the resistance connection to the power system 19, the backflow prevention device 14, and the auxiliary machine power. Therefore, in step S8, even if the power output is stopped and the consumption of oxygen becomes only the resistor 7, the potential of the oxidizer electrode 2 is prevented from rising and the potential of the oxidizer electrode 2 is prevented from becoming high. it can.

  In step S2, the power output from the fuel cell stack 3 is reduced by lowering the output to the set minimum value. In this case, even if a reforming failure occurs in the reformer due to power shortage or the like, and hydrogen shortage occurs, the output current is small, so damage to the battery can be kept small.

  In steps S3 to S7, since hydrogen supply continues, even if oxygen is consumed by power output or resistance connection, there is no shortage of hydrogen in the fuel electrode 1, and corrosion of the electrode of the fuel cell (catalyst of the fuel electrode) is caused. Can be prevented. Hereinafter, the shortage of hydrogen in the fuel cell system will be described.

  In general, in a fuel cell system, about 80% of the hydrogen component in the fuel gas supplied to the fuel cell stack is consumed by the power generation reaction, and the remaining fuel gas containing about 20% of the hydrogen component is used as the fuel off-gas. The heat balance of the reformer is maintained by being supplied to the combustion burner of the reformer.

  In the operation when the fuel cell power generation system using the reformer as the hydrogen-containing gas supply means is stopped, the power generation voltage decreases as the supply of the oxidant gas to the oxidant electrode is stopped. The reactions shown in Formula 1 and Formula 2 are less likely to occur. As a result, the hydrogen gas consumed in the fuel cell stack is reduced, and the flow rate (energy) of the fuel off gas supplied to the combustion burner of the reformer is increased.

  If the increase in the flow rate of the fuel off-gas is short, the temperature change of the reformer may be small, but the supply of the fuel gas to the fuel electrode must be continued until at least oxygen in the oxidizer electrode is consumed. When excessive fuel off gas is supplied to the reformer combustion burner for a long time, there is a problem that an abnormal temperature rise of the reformer occurs.

  In order to prevent the problem of abnormal temperature rise of the reformer, if the reformer is stopped immediately by stopping the fuel off-gas supply and stopping the combustion of the combustion burner, the fuel gas is supplied from the reformer to the fuel electrode. Stops. As a result, when the fuel electrode hydrogen is consumed to remove oxygen from the oxidizer electrode or to generate hydrogen at the oxidizer electrode, hydrogen depletion occurs at the fuel electrode. There is a problem of deterioration.

Formula 4 C + H ₂ O → 2H ⁺ + CO + 2e ⁻
The consumption of oxygen is not an integrated power amount but an integrated current amount. In the oxygen consumption of the oxidizer electrode 2, the voltage of the fuel cell decreases as the oxygen decreases. As shown in FIG. 3, when the inverter output device 13, the auxiliary power supply device 12 and the resistor 7 are used, the auxiliary power supply device 12 and the resistor 7 are used, or only the resistor 7 is used. The fuel cell outputs more power than the case. Therefore, by changing the power output (auxiliary power + resistance → resistance) in two stages with respect to the elapsed time as in steps S5 to S8, more current can be taken and more oxygen can be taken. Can be consumed.

  Further, since the electric energy of the fuel cell obtained from the remaining oxygen and hydrogen can be output to the system power 18 after the oxygen supply is stopped (step S3), the fuel cell system 100 operates with high energy efficiency. .

  Further, when stopping the output power of the inverter output device 13 that is an external load and connecting the resistor 7 at the same time, it may take time to complete the connection of the resistor 7. During the time lag, there is a possibility that a non-current state in which no current is output from the fuel cell may occur, or the potential of the oxidizer electrode 2 increases to become a high potential. In order to avoid this, the time required for the connection of the resistor 7 is acquired in advance, and the connection of the resistor 7 is started faster by that amount. That is, by starting the connection of the resistor 7 before the output power is stopped, the connection of the resistor 7 is prevented from being completed after the output power is stopped.

  FIG. 4 is a diagram showing an example of the cell voltage behavior of the fuel cell when the power output stop and the resistance connection are simultaneously performed. This is an example when the fuel cell stack 3 is composed of several tens of cells. The battery current I drops from 35 [A] to 0 [A] after some time (time lag) elapses from the time when the external load is stopped and the resistor is connected simultaneously (elapsed time 0.0 seconds).

  After step S4, since the resistor 7 is connected, even if a large amount of air has invaded momentarily during storage of the fuel cell system 100, the resistor 7 can quickly consume oxygen.

  When the fuel electrode 1 and the oxidant electrode 2 are connected via the resistor 7, the hydrogen in the fuel electrode 1 passes through the electrolyte as hydrogen as it moves to the oxidant electrode 2 as in power generation. As well as moving the electrolyte in the form of protons. As a result, oxygen present in the oxidant electrode 2 is easily consumed, and a high potential state of the oxidant electrode 2 is easily prevented. Therefore, it is possible to prevent the oxidizer electrode 2 from increasing in potential and becoming high potential.

  As described above, according to the present embodiment, it is possible to prevent the oxidizer electrode 2 from increasing in potential when it is stopped at a high efficiency to become a high potential, and even if a large amount of air intrudes during storage, the catalyst Since the deterioration can be prevented, it is possible to provide the fuel cell system 100 whose performance is not deteriorated by starting, stopping and storing.

  As a stopping method that does not use resistance, a method of preventing the oxidant electrode from rising to a high potential by consuming the oxygen of the oxidant electrode by an external load (electronic load device) after stopping the oxygen supply. There is. The external load at this time is an electronic load device that operates using a power system, is not supplied with power from the fuel cell stack, and can operate without being influenced by the voltage of the fuel cell stack.

  The above-described method that does not use the resistor requires a device that operates the electronic load device using the system power to lower the stack voltage, which increases the size of the system. Moreover, since system power is used, the system is inefficient.

  The oxygen consumption during the period when the external load is stopped depends on the permeation of hydrogen through the electrolyte (Equation 3), and the electrochemical oxygen consumption (Equation 3) is such that hydrogen is transferred by protons through the electrolyte. 1 and Equation 2) cannot be performed, so oxygen consumption is slow and the potential rises and tends to be high. Therefore, after the external load is disconnected, the potential of the oxidant electrode is likely to increase and become a high potential. In addition, the space communicating with the fuel electrode and the oxidant electrode cannot always be in a reducing atmosphere, the oxidant electrode or the catalyst layer of the fuel electrode cannot be prevented from becoming a high potential, and is formed on the oxidant electrode. The oxidized oxide on the surface of the catalyst cannot be reduced.

(Second Embodiment)
FIG. 5 is a schematic configuration diagram showing the fuel cell system of the present embodiment. In the following drawings, the same reference numerals as those in the previous drawings are attached to portions corresponding to those in the previous drawings, and detailed description thereof is omitted.

  The fuel cell system according to the present embodiment is different from the fuel cell system according to the first embodiment in that the volume of the fuel system manifold 20a is larger than that of the fuel system manifold 20. The number of hydrogen molecules (N1) in the space of the fuel electrode 1 including the fuel system manifold 20a is equal to the number of oxygen molecules in the space of the oxidant electrode 2 including the oxidant system manifold 21 sealed by the oxidant electrode sealing valve 10. The size of the volume of the fuel system manifold 20a is selected so as to be at least twice the number (N2) (N1 ≧ N2).

  Instead of making the fuel system manifold 20a thicker than the fuel system pipe 16, the volume of the oxidant system manifold 21 may be reduced to realize the above condition (N1 ≧ N2).

  FIG. 6 is a flowchart for explaining an operation method of the fuel cell system 100 of the present embodiment.

[Step S21]
Similarly to step S <b> 1, an oxidant and a hydrogen-containing gas are supplied, and the required power is output to the power system 19 by the power adjustment mechanism 6.

[Step S22]
Similarly to step S2, the output to the grid power 18 is reduced to the set minimum value. Accordingly, the supply amount of the hydrogen-containing gas from the hydrogen supply device 4 is reduced, and the power supply amount to the hydrogen supply device 4 of the auxiliary power supply device 12 is reduced.

[Step S23]
The oxidant supply device 5 is stopped, the supply of the oxidant is stopped, and the oxidant electrode 2 is sealed by the oxidant electrode sealing valve 10. Further, the supply of the hydrogen-containing gas to the fuel electrode 1 is also stopped.

[Step S24]
Similar to step S <b> 4, the fuel electrode 1 and the oxidant electrode 2 are connected by a resistor 7.

[Step S25]
The voltage of the fuel cell stack 3 is measured by a voltmeter 18 (not shown), and it is determined whether the voltage of the fuel cell stack 3 is equal to or higher than the minimum voltage value Vc (for example, the average cell voltage is 0.6 V) based on the measured voltage. Is done.

[Step S26]
When the determination result of step S25 is Yes (stack voltage ≧ Vc), the power output is continued.

[Step S27]
When the determination result of step S25 is No (stack voltage <Vc), the power output is stopped.

  When hydrogen is abundant, a cell voltage of less than 0.6 V means that oxygen is sufficiently consumed. On the other hand, if the cell voltage is less than 0.6 V despite the sufficient oxygen, there is a high possibility of hydrogen shortage. In either case, even if the power output from the stack is reduced, the potential of the oxidizer electrode is unlikely to rise.

  Since the cell voltage of the fuel cell decreases as long as oxygen is consumed, if the fuel electrode 1 contains more than twice as much hydrogen as oxygen molecules, the sealed oxidant can be used without supplying new hydrogen. The oxygen at the pole 2 can be consumed.

In step S 23, by stopping the supply of hydrogen to the fuel electrode 1, without consuming power due to the oxygen consumption (electric energy) to auxiliary power associated with hydrogen supply may be the inverter output power In the output stop process, a highly efficient fuel cell system can be provided.

  In addition, since the generation of hydrogen is stopped before the oxygen consumption is finished, the time during which a large amount of off-gas hydrogen is supplied to the reformer can be minimized, and an abnormal temperature rise of the reformer can be prevented. It can be minimized.

  The hydrogen supply device 4 is very easily out of balance, becomes unstable in step S23, and hydrogen may not be generated properly.

  When hydrogen is not properly generated, the gas containing almost no hydrogen exhausts the hydrogen-rich gas that was in the fuel electrode 1, so that not only the hydrogen in the fuel electrode 1 is deficient, but also the carbon C contained in the raw fuel. May become CO and poison the fuel electrode 1 catalyst. In order to avoid them, the fuel cell can be protected by stopping the hydrogen supply in step S23.

  In addition, you may supply electric power to a secondary battery etc. instead of an electric power grid | system.

(Third embodiment)
The fuel cell system of this embodiment has the same configuration as the fuel cell system of the first embodiment, but the operation method is different.

  FIG. 7 is a flowchart for explaining an operation method of the fuel cell system 100 of the present embodiment.

[Step S31]
A hydrogen-containing gas is supplied to the fuel electrode 1 by the hydrogen supply device 4.

[Step S32]
Similar to step S <b> 4, the fuel electrode 1 and the oxidant electrode 2 are connected by a resistor 7.

[Step S33]
Oxidant gas (air) is supplied to the oxidant electrode 2, and power output is started by the power adjustment mechanism 6. The power is gradually increased from zero. For example, it increases from 0 to 250 [W] within 2 minutes or 5 minutes.

  By the way, when the fuel cell system is not provided with a hydrogen concentration meter for cost reduction, a gas unknown as being hydrogen-rich is supplied to the fuel electrode 1. Whether the hydrogen concentration is appropriate is determined based on the stack voltage by further supplying air to the oxidizer electrode 2 and taking the current from the fuel cell stack 3.

[Step S34]
The stack voltage is measured by the voltmeter 18 and it is determined whether or not the measured voltage is equal to or higher than Vc3. Here, Vc3 is, for example, a minimum stack voltage corresponding to a cell voltage of 0.8V.

[Step S35]
When the determination result in step S34 is No (stack voltage ≧ Vc3), the resistance connection (step S33) is continued.

[Step S36]
If the determination result in step S34 is Yes (stack voltage <Vc3), it is determined whether or not the stack voltage <Vc4. Here, Vc4 is, for example, a stack voltage corresponding to a cell voltage of 0 to 0.6V.

[Step S37]
If the determination result in step S36 is Yes (stack voltage <Vc4), the power output is stopped. The determination in step S36 is repeated until Yes.

  In the present embodiment, after step S32 of the resistance connection, step S33 for supplying an oxidant and outputting electric power is performed. Therefore, in order to avoid inconvenience (for example, electrode corrosion) due to hydrogen shortage, when power is gradually increased from 0 (when the current increase rate of the external load is slow), in fact, in case of hydrogen shortage Even if the hydrogen concentration is appropriate, oxygen can be consumed because more current can be obtained by the resistance connection. As a result, it is possible to suppress the oxidizer electrode 2 from being at a high potential and corroding the catalyst layer of the oxidizer electrode 2, thereby suppressing the performance deterioration of the fuel cell. Since the external load is stopped when the stack voltage is lower than a predetermined value, it is safer that the current increase rate is slower.

  When the fuel electrode 1 and the oxidant electrode 2 are connected by the resistor 7, the reforming is not performed well and even if the fuel electrode 1 is deficient in hydrogen, there is no significant deterioration. The rise can be suppressed.

  Further, while gradually increasing the power output from 0, the stack voltage can be monitored as in step S36 to protect the fuel cell from hydrogen shortage.

  In step S34, when the cell voltage is sufficiently lower than 0.9V, the amount of power lost by the resistor 7 can be minimized by performing the resistor connection release (step S35).

  According to at least one embodiment described above, deterioration of the fuel cell can be suppressed.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Fuel electrode, 2 ... Oxidizer electrode, 3 ... Fuel cell stack, 4 ... Hydrogen supply apparatus, 5 ... Oxidant supply apparatus, 6 ... Power adjustment mechanism, 7 ... Resistance, 8 ... Switch, 9 ... Power consumption mechanism, DESCRIPTION OF SYMBOLS 10 ... Oxidizer pole sealing valve, 11 ... Control apparatus, 12 ... Auxiliary power supply apparatus, 13 ... Inverter output apparatus, 14 ... Backflow prevention apparatus, 15 ... Hydrogen-containing fuel supply apparatus, 16, 16a ... Fuel system piping, DESCRIPTION OF SYMBOLS 17 ... Oxidant system piping, 18 ... Voltmeter, 19 ... Electric power system, 20, 20a ... Fuel electrode manifold, 21 ... Oxidant electrode manifold, 100 ... Fuel cell system.

Claims (4)

A fuel cell stack formed by stacking unit cells including a fuel electrode and an oxidant electrode;
Hydrogen supply means for supplying a hydrogen-containing gas to the fuel electrode;
Oxygen supply means for supplying an oxygen-containing gas to the oxidant electrode;
Power adjusting means for adjusting the power output from the fuel cell stack;
A resistor and a switch are provided, and when the switch is closed, a current path is formed between the fuel electrode, the resistor, and the oxidant electrode, and power is consumed by the resistor. Power consumption means,
An oxidant electrode sealing means for sealing a space communicating with the oxidant electrode;
In order to stop the power output from the fuel cell stack, the oxygen supply means is stopped, and then the space communicating with the oxidant electrode is sealed by the oxidant electrode sealing means, and then the switch is turned on. closed, Ri then name comprises a control means comprising performing control to stop the power adjustment means,
The power adjustment means comprises inverter output means for outputting power to a power system, and auxiliary power supply means for supplying power to the hydrogen supply means,
The control means, when stopping the power adjustment means, first stops either the inverter output means or the auxiliary power supply means . A fuel cell stack formed by stacking unit cells including a fuel electrode and an oxidant electrode;
Hydrogen supply means for supplying a hydrogen-containing gas to the fuel electrode;
Oxygen supply means for supplying an oxygen-containing gas to the oxidant electrode;
Power adjusting means for adjusting the power output from the fuel cell stack;
A resistor and a switch are provided, and when the switch is closed, a current path is formed between the fuel electrode, the resistor, and the oxidant electrode, and power is consumed by the resistor. Power consumption means,
An oxidant electrode sealing means for sealing a space communicating with the oxidant electrode ;
An operation method of a fuel cell system, wherein the power adjustment means comprises inverter output means for outputting power to a power system and auxiliary power supply means for supplying power to the hydrogen supply means. And
An operation method for stopping the power output from the fuel cell stack is as follows:
Stopping the oxygen supply means;
Next, sealing the space communicating with the oxidant electrode by the oxidant electrode sealing means;
Next, closing the switch;
Then look including the step of stopping the power conditioning unit,
In the step of stopping the power adjustment means, one of the inverter output means and the auxiliary power supply means is stopped first, and the operating method of the fuel cell system. The hydrogen supply means comprises a reforming means for reforming the fuel to produce a hydrogen-containing gas,
The operation method for stopping the power output from the fuel cell system includes:
Before the step of closing the switch, stopping the hydrogen supply means;
Further comprising the step of stopping the hydrogen supply means and the step of reducing the power output from the power adjustment means to a power system before the step of stopping the oxygen supply means to a predetermined minimum value. The operating method of the fuel cell system according to claim 2 , wherein In the step of sealing the space communicating with the oxidant electrode by the oxidant electrode sealing means, the number of hydrogen molecules in the space communicating from the hydrogen supply means to the fuel electrode is determined by the oxidant electrode sealing means. The number of oxygen molecules in the space communicating with the sealed oxidant electrode is set to be twice or more,
3. The operation method for stopping power output from the fuel cell system further includes a step of stopping the hydrogen supply unit before the step of closing the switch. Method of operating the fuel cell system.

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