JP5222589B2 - Fuel cell system and control method - Google Patents

Description

The present invention relates to a fuel cell system using a direct methanol fuel cell (DMFC) capable of driving an electronic device as a power generation unit and a control method thereof.

With recent advances in electronic technology, a wide variety of portable electronic devices are rapidly spreading. In the future, a fuel cell power source that can be easily refueled is attracting attention as a power source having a long continuous driving time in response to an increasing amount of information of mobile electronic devices and higher speed and higher functionality.

  Among fuel cells, a direct methanol fuel cell using liquid fuel has a high volumetric energy density of fuel and is easy to handle.

The fuel cell system generates power by a chemical reaction between an aqueous methanol solution and oxygen gas in a direct methanol fuel cell (DMFC stack). The reaction is accelerated by the concentration and temperature of the aqueous methanol solution, and heat is generated from the DMFC stack. However, at the start of operation of the fuel electronic system, the aqueous methanol solution and DMFC stack are at room temperature (the outside temperature of the fuel cell system (environmental temperature)), the reaction in the DMFC stack is difficult to proceed, and the output voltage of the fuel cell system is However, there is a problem that it takes time to reach the required voltage (rated voltage) and to start steady operation.

  There is no literature that focuses on such a startup time of the fuel cell system as a problem.

  An object of the present invention is to shorten the startup time of the fuel cell system (the time from the start of power generation until the start of steady operation).

  Another object of the present invention is to realize stable control in order to shorten the startup time of the fuel cell system.

  Still another object of the present invention is to simply configure a control program for controlling the startup time of the fuel cell system.

  Still another object of the present invention is to make it possible to control the startup time of the fuel cell system according to the outside air temperature.

A fuel cell system and a control method thereof according to the present invention include a DMFC stack that supplies an aqueous methanol solution of a predetermined concentration from the anode side, supplies air of a predetermined air volume from the cathode side, and generates electric power of a rated voltage by a chemical reaction thereof, In response to the start of operation of the stack, there is provided a mixing tank for supplying a methanol aqueous solution having a concentration higher than a predetermined concentration from the anode side, and an air pump for supplying air having an air volume smaller than the predetermined air volume from the cathode side.

  Another desirable aspect of the present invention further includes a blower having an air volume that cools the methanol aqueous solution having a predetermined concentration in the mixing tank to a predetermined temperature, and the air volume of the blower is higher than the predetermined concentration in response to the start of operation of the DMFC stack. The flow rate is controlled to maintain the concentration of the aqueous methanol solution at a temperature higher than a predetermined temperature.

  Still another desirable aspect of the present invention is that the concentration of a high-concentration aqueous methanol solution is directed to a predetermined concentration from the start of operation of the DMFC stack to the generation of power at a rated voltage, and an air flow smaller than a predetermined air flow of the air pump is predetermined. Control is performed stepwise toward the air volume and the air volume maintained at a temperature higher than the predetermined temperature of the blower toward the air volume that is cooled to the predetermined temperature.

  Still another desirable aspect of the present invention is that each of the stepwise controls is executed so that the difference between the steps becomes small with the lapse of time from the start of operation of the DMFC stack to the generation of power of the rated voltage.

  In still another desirable aspect of the present invention, each stepwise control is executed based on predetermined control data.

  According to still another desirable aspect of the present invention, a set of control data is selected from a plurality of predetermined sets of control data in response to an outside air temperature (environment temperature) of the fuel cell system.

According to the present invention, the startup time of the fuel cell system can be shortened.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a fuel cell system 1 of the present embodiment. A DMFC stack (power generation unit of a direct methanol fuel cell) 4 with an electrolyte membrane / electrode assembly in the fuel cell system 1 generates power by a chemical reaction between an aqueous methanol solution supplied to the anode and oxygen supplied to the cathode.

The aqueous methanol solution reacts according to the formula (1) on the anode side and dissociates into hydrogen ions, electrons and carbon dioxide.
_{CH 3 OH + H 2 O →} 6H + + 6e - + CO 2 (1)
The generated hydrogen ions move to the cathode side through the electrolyte membrane, and react with oxygen gas diffused from the air supplied to the cathode and electrons on the electrode according to the formula (2) to generate water.
^{6H + + 6e - + 3 /} 2O 2 → 3H 2 O (2)
Further, in the direct type methanol fuel cell, a phenomenon called methanol crossover occurs in which methanol on the anode side passes through the electrolyte membrane and moves to the cathode side. As shown in the formula (3), the methanol that has moved to the cathode side becomes a combustion reaction of methanol in which methanol is oxidized by oxygen to generate carbon dioxide and water, and generates heat.
CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O (3)
The methanol aqueous solution supplied to the anode of the DMFC stack 4 includes methanol supplied from the fuel cartridge 2 and purified water supplied from the purified water cartridge 3 (hereinafter sometimes simply referred to as water) in the mixing tank 9. It is mixed to a predetermined concentration (about 3%) and stored in the mixing tank 9. Methanol supplied from the fuel cartridge 2 is supplied to the mixing tank 9 via the electromagnetic valve 7 by the mixing pump 5. The water supplied from the purified water cartridge 3 is supplied to the mixing tank 9 via the electromagnetic valve 8 by the mixing pump 6. In order to obtain a methanol aqueous solution having a predetermined concentration in the mixing tank 9, the mixing pumps 5 and 6 and the electromagnetic valves 7 and 8 are controlled by the controller 13 (broken line in the figure). The methanol aqueous solution passes through the methanol concentration sensor 10 and is supplied to the anode of the DMFC stack 4 by the fuel pump 11. The oxygen supplied to the cathode of the DMFC stack 4 is oxygen gas diffused from the air by the air pump 12.

  The controller 13 controls accessories such as the DMFC stack 4 and the mixing pump 5 based on various sensor outputs (one-dot chain line in the figure) (broken line in the figure). The sensors are a concentration sensor 10 that monitors the concentration of methanol supplied to the DMFC stack 4, a temperature sensor 15 that monitors the temperature of the DMFC stack 4, a temperature sensor 16 that monitors the aqueous methanol solution temperature in the mixing tank 9, and a fuel cell system 1. Temperature sensor 17 for monitoring the internal temperature (environment temperature), remaining amount sensor 18 for monitoring the remaining amount of methanol in the combustion cartridge 2, remaining amount sensor 19 for monitoring the remaining amount of water in the purified water cartridge 3, and DMFC stack 4 Is a voltmeter 21 that monitors the voltage that is being generated. The temperature detected by the temperature sensor 17 is the same internal temperature as the external temperature before the operation of the fuel cell system 1 (after stopping for a while). Control targets by the controller 13 are mixing pumps 5 and 6, solenoid valves 7 and 8, a fuel pump 11, an air pump 12 and a blower 22 for cooling the mixing tank 9.

  The chemical reaction in the DMFC stack 4 is not only accelerated by the concentration of the aqueous methanol solution, but also accelerated by the temperature of the aqueous methanol solution. In order not only to keep the output power of the DMFC stack 4 stable, but also to avoid overheating of the DMFC stack 4, the temperature of the aqueous methanol solution in the mixing tank 9 is monitored by the temperature sensor 26 to cool the mixing tank 9 The blower 22 is controlled by the controller 13. The air pump 12 that supplies oxygen gas to the cathode side of the DMFC stack 4 also functions as a cooling device for avoiding overheating of the DMFC stack 4 and maintaining stable output power.

  The controller 13 is an output interface (connector) 20 for supplying the electric power generated by the DMFC stack 4 to the connected electronic equipment, and an external for input / output of control information and display information etc. outside the fuel cell system 1 The interface 23 and the Li (lithium) battery 14 are connected. The Li battery 14 supplies power for the operation of the controller 13 and the like when the fuel cell system 1 is started up (starts operation). When the fuel cell system 1 enters steady operation, the power generated by the DMFC stack 4 is used. Charged.

The control by the controller at the start of operation of the fuel cell system (at the start of power generation) will be described with reference to FIG. When the concentration C _{n of} the aqueous methanol solution in the steady state of the fuel cell system, the air volume Q _n of the air pump 12 and the air volume q _{n of the} blower 22 are set and the operation of the fuel cell system is started (start time: t = 0), DMFC output voltage V of the stack 4 (t), as shown by the broken line in FIG. 2 (a), the dead time via the (dead time) T _d, increases according to an exponential function of the time constant tau _a, constant at time t ₆ it reaches a state of a voltage (rated voltage) V _n (equation 4).
V (t) = V _n {1−exp (− (t−T _d ) / τ _A )} (4)
This time t ₆ (= t ₆ −0) is a waiting time for a user of the fuel cell system that cannot electrically connect a load such as a portable electronic device. In particular, it is desirable that this waiting time be short when using a portable electronic device in an emergency or emergency.

Therefore, in this embodiment, control is performed so that the time until the rated voltage V _n is reached is t ₅ (t ₅ <t ₆ ) (formula (5)). τ _B is a time constant, and τ _B <τ _A.
V (t) = V _n {1−exp (− (t−T _d ) / τ _B )} (5)
In order to control in this way, the concentration C (t) of the aqueous methanol solution, the air volume Q (t) of the air pump 12, and the air volume q (t) of the blower 22 are set according to the passage of time from the start of operation of the fuel cell system. It changes like Formula (6)-Formula (8).
C (t) = C _n + (C ₀ −C _n ) · exp (−t / τ _C ) (6)
Q (t) = Q ₀ + (Q _n −Q ₀ ) · {1−exp (−t / τ _C )} (7)
q (t) = q _n · {1−exp (−t / τ _C )} (8)
Here, C ₀ is the initial value of the concentration of the aqueous methanol solution, Q ₀ is the initial value of the air volume of the air pump 12, and supplies the minimum oxygen gas necessary for the reaction of formula (2) in the DMFC stack 4 to proceed The air volume that can be produced, τ _C is a time constant, and τ _B <τ _C <τ _A. Expressions (6) to (8) are shown as exponential function curves (thin solid lines) in FIGS. 2 (b) to (d).

  In the start-up operation from the start of operation of the fuel cell system to the start of steady operation, Equation (6) means that a methanol aqueous solution having a concentration higher than the predetermined concentration of the methanol aqueous solution during steady operation is supplied. Equation (7) And the equation (8) means that the air volumes of the air pump 12 and the blower 22 are controlled to an air volume smaller than a predetermined air volume at the time of steady operation. As will be described later, when the temperature of the aqueous methanol solution in the mixing tank 9 is appropriately maintained by the outside air temperature, it is not necessary to control the air volume q (t) of the blower 22 for cooling the aqueous methanol solution. . In short, it is sufficient that the temperature of the aqueous methanol solution can be maintained at a predetermined temperature or higher than a predetermined temperature during start-up operation.

  In order to control the concentration and the air volume according to the theoretical curves of the equations (6) to (8), the methanol concentration sensor 10, the temperature sensor 16, a sensor for measuring the air volume of the air pump 12 (not shown), and the DMFC stack 4 A control system that feeds back the value of the voltmeter 21 for measuring the generated power voltage must be configured, and the control system becomes complicated. In order to realize this control by a program executed by a processor, the number of control (program) steps is increased.

Here, as shown in FIGS. 2 (b) to (d) (step-shaped thick solid line), the methanol concentration C (t), the air volume Q (t) of the air pump, and the methanol aqueous solution in the mixing tank 9 are cooled. The air volume q (t) of the blower 22 is changed stepwise with time. The methanol concentration C (t), time 0 to t ₁ in _{C 1 (C 0> C 1} ≧ C (t 1), for example, _{C 1 = (C 0 + C} (t 1)) / 2), times t ₁ ~ At t ₂ , control is performed as follows: C ₂ (C (t ₁ )> C ₂ ≧ C (t ₂ ), for example, C ₂ = (C (t ₁ ) + C (t ₂ )) / 2). Air volume Q (t) of the air pump 12, time 0 to t ₁ in _{Q 1 (Q 0 ≦ Q 1} <Q (t 1), for example, _{Q 1 = (Q 0 + Q} (t 1)) / 2), time From t _{1 to} t ₂ , control is performed as Q ₂ (Q (t ₁ ) ≦ Q ₂ <Q (t ₂ ), for example, Q ₂ = (Q (t ₁ ) + Q (t ₂ )) / 2). The air volume q (t) of the blower 22 is similarly controlled.

For such control, control data C _i , Q _i , q _i (i = 1, 2, 3,...) Is held in a memory and switched at predetermined time intervals, and the control program is simplified.

  Although it has been described that the methanol concentration C (t), the air volume Q (t) of the air pump 12 and the air volume q (t) of the blower 22 are controlled in synchronization, it is not always necessary to synchronize. In addition, there are restrictions on the control conditions and control accuracy of the pump and blower devices, and synchronous control cannot always be realized. The power generation voltage and concentration of methanol aqueous solution by the DMFC stack 4 are monitored in preparation for occurrence of malfunctions or abnormalities in control, so feedback is provided as necessary to achieve desirable control including fine adjustment. .

When the methanol concentration C (t), the air volume Q (t) of the air pump 12 and the air volume q (t) of the blower 22 can be controlled in synchronization, the time interval Δt between times t ₁ , t ₂ , t ₃ ,. It is desirable that (Δt = t _{i + 1} −t _i , (i = 1, 2, 3,...)) Be constant. This is because the control program may be started at the timings t ₁ , t ₂ , t ₃ ,. In addition, although it has been described above that the time until reaching the rated voltage V _n is controlled to be t ₅ (t ₅ <t ₆ ), it does not mean that a steady state is reached at time Δt × 5 (subscripts are explained) Is attached for)
As an alternative, the step difference (step (step)) of each control amount of the methanol concentration C (t) to be changed stepwise, the air volume Q (t) of the air pump, and the air volume q (t) of the blower 22 (for example, C (t ₂ ) There is a method of keeping −C (t ₁ )) constant. Since the time interval in this case depends on the characteristics of the exponential function, the time interval is small immediately after the start of operation of the fuel cell system 1, and increases as the steady state is approached. As another alternative, there is a method in which the steps are determined in a straight line instead of an exponential function (the step difference of the control amount and the time interval are constant).

  Compared with these alternatives, the above-described control with a constant time interval has the following advantages in addition to the ease of realizing the control (program). In the control with a constant time interval, the change in the control amount (step difference) is large immediately after the start of operation of the fuel cell system 1 (the absolute value of the differential coefficient of the exponential function is large and the action of differential control works). The amount of change in the control amount (step difference) is small as the steady state is approached (the absolute value of the derivative of the exponential function is small and the action of integral control works), and the fuel cell system 1 Is stabilized to a steady state (the output voltage is not overshooted). In the above alternative, the operations of the differential control and the integral control are reversed, and not only the control becomes complicated, but also the control becomes unstable. Further, another alternative is based on proportional control, and not only can the advantages of the control of the present embodiment be obtained immediately after the start of operation, but also the stability advantages when approaching a steady state. Comparison with the above alternatives is a case where the methanol concentration C (t) etc. can be controlled in an almost ideal state, and depending on the restrictions of the specific equipment to be used, alternatives or other alternative controls may be selected or combined. You may not get.

  A schematic diagram of the controller 13 for realizing the above control is shown in FIG. The controller 13 includes a processor 30, a rewritable nonvolatile memory 31 such as an EEPROM (Electrically Erasable and Programmable Read Only Memory) that stores a control program, and a RAM (Random Access Memory) that stores detection data and control data from each sensor. Such as rewritable memory 32, timer 33, sensor interface 34 for sending / receiving data (control data, detection data) to / from each sensor, data (control data, DMFC stack 4 and pumps) Via the control interface 35 for transmitting / receiving the status data), the external interface 23 or the input / output interface 36 for inputting / outputting data with the DIP switch 23 provided remotely, and the communication connector 24 provided for the external interface 23, A computer such as a personal computer or a device equivalent to a computer (hereinafter referred to as a computer) A communication interface 37 for communicating according to the communication protocol. Each interface has been described functionally divided, but may be configured to be integrated or further separated for mounting.

FIG. 4 shows a process flowchart of the control program. The control program is so-called firmware stored in the nonvolatile memory 31 together with constants such as control data C _i , Q _i , q _i (i = 1, 2, 3,...). The control program is activated by a periodic timer set in the timer 33. The period set in the period timer is, for example, the aforementioned time interval Δt. When the time interval between the start-up from the start of operation and the time of steady operation is different, the system is started at the shorter time interval. The detection data from each sensor is read (step 40). It is determined whether or not the operation is a steady operation (step 41). To determine whether or not the operation is steady, the time count value described later in step 43 is set as the time until the start of steady operation, for example, exceeds t ₅ in FIG. 2, or the output reaches the rated voltage. If so, it will be in steady operation. It is determined whether the read sensor data indicates a normal value (step 42). If the sensor data is not normal, the process branches to step 47.

  In the case of start-up operation, the time is counted (step 43). Normally, when the operation is started, the controller 13 is supplied with electric power from the Li battery 14 and is reset. When reset, the volatile memory 32 is cleared to zero. Since the value of a predetermined area (time count area) of the memory 32 is also cleared to zero as a time counter, it is counted (+1) every time the process of step 43 is entered. By multiplying the time count area by the time interval Δt, the elapsed time from the start of operation of the fuel cell system (more precisely, the reset of the controller 13) can be obtained. According to the elapsed time, the methanol concentration C (t) described with reference to FIG. 2 is controlled, and the air volume Q (t) of the air pump and the air volume q (t) of the blower are set.

  The methanol concentration C (t) is determined by the mixing ratio of methanol from the fuel cartridge 2 and water from the purified water cartridge 3. Therefore, the controller 13 performs mixing so that the deviation between the sensor data of the concentration sensor 10 for monitoring the concentration of the aqueous methanol solution (the concentration of the aqueous methanol solution in the mixing tank 9) and the predetermined methanol concentration C (t) becomes zero. Controls pumps 5 and 6 and solenoid valves 7 and 8. Although the methanol concentration C (t) is realized by so-called feedback control, a dead time as a control system occurs due to a response delay of the mixing pumps 5 and 6 and the solenoid valves 7 and 8. If this dead time affects the start-up process of the fuel cell system 1 (start-up time becomes longer than the desired time), shorten the control program start cycle and cancel the dead time in advance of the predetermined time. Control of the next stage may be started, or a concentration (C (t) + ΔC) higher than a predetermined methanol concentration C (t) may be controlled as a target value.

  In the case of steady operation, it is determined whether the read sensor data indicates a normal value (step 45), and if not normal, the process branches to step 47. If it is normal, the steady operation is performed (step 46). The process of steady operation is as follows: (1) Control the concentration of aqueous methanol solution and the air volume of the air pump 12 so that the voltage generated by the DMFC stack 4 indicated by the voltmeter 21 is stable against load fluctuations. (2) Steady operation Immediately after starting operation, the power supply of the controller 13 and the pump and the like is switched from the Li battery 14 to the output from the DMFC stack 4, (3) monitoring the remaining amount of the fuel cartridge 2 and the purified water cartridge 3, (4) abnormality Monitoring and abnormality processing. In the case of an abnormal state, abnormality processing (emergency stop of the fuel cell system, lighting of the abnormality display lamp 25, etc.) corresponding to the content of the abnormality is executed (step 47). A detailed description of the steady operation process and the abnormality process will be omitted.

  Note that after determining whether the operation is steady in step 41, whether it is normal or not is determined separately in step 42 and step 45 because it is set as appropriate (normal) during start-up operation This is because the concentration of the aqueous methanol solution may be abnormal during steady operation. That is, the normal / abnormal judgment criteria are different between the startup operation and the steady operation.

  Next, typical operation modes of the fuel cell system 1 will be described. Typical operation modes are a battery operation mode, an external control mode, and a rewrite mode, which are operation modes attached to the DIP switch 26 of FIG. First, a battery operation mode that is a normal operation of the fuel cell system 1 will be described. The DIP switch 26 in FIG. 3 represents a state in which the switch of bit 0 is ON and the battery operation mode is set. When the operation switch of the switch / display 25 is turned on in the state set in this way, power is supplied from the Li battery 14 to the controller 13 and each device, and the controller 13 and reset processing are performed by a reset circuit (not shown). Necessary equipment is reset. The operation after reset is as described with reference to FIG.

  An external control mode when bit 1 of the DIP switch 26 is ON will be described. The external control mode is a mode in which the fuel cell system is controlled instead of executing the control program stored in the nonvolatile memory 31 by a program executed by a computer connected via the communication interface 37 and the communication connector 24. . In this case, a control program part related to input / output and control with each interface of the controller 13 is operated, and this part is controlled in cooperation with a computer via the communication interface 37 and the communication connector 24. There is a method of providing an interface for pulling out the bus (control bus, address bus, data bus) of the controller 13 to the outside, and connecting a computer via this interface. When the latter method is adopted, the processor 30 and the nonvolatile memory 31 of the controller 13 are electrically disconnected from the bus (for example, brought into a high impedance state when viewed from the bus).

By adopting such a configuration, the execution of the control program can be emulated by a computer connected to the outside of the fuel cell system 1. With this emulation, a logic test of the control program can be executed. Emulation is not limited to various parameters during steady operation, but is also necessary for determining control data C _i , Q _i , q _i (i = 1, 2, 3,...) In this embodiment. It has been explained that the chemical reaction in the DMFC stack 4 of the fuel cell system 1 is not only accelerated by the concentration of the aqueous methanol solution but also accelerated by the temperature of the aqueous methanol solution. The fuel cell system 1 connected to the portable electronic device is used in places such as cold regions and tropical regions, and is also used outdoors. Therefore, not only the control data C _i , Q _i , q _i (i = 1, 2, 3,...) Under normal temperature conditions, but also, for example, control data adapted to an outside temperature of 0 ° C., −20 ° C., etc. Must also be prepared. Emulation is also useful for experimentally determining these control data values. Depending on the extreme environment, the logic of the control program may need to be changed.

  A rewrite mode when bit 2 of the DIP switch 26 is ON will be described. The rewrite mode is a mode in which a control program and control data tested in the external control mode are newly written into a rewritable nonvolatile memory 31 such as an EEPROM from an external computer. For this purpose, a loader that reads from an external computer according to a predetermined communication protocol via a communication interface and writes to the nonvolatile memory 31 is stored in a predetermined area of the nonvolatile memory 31 (an area different from the control program storage area) in advance. Store it. It is set so that the processor 30 executes the loader in response to detection of the rising edge of bit 2 of the DIP switch 26 (change from OFF to ON). The rise of bit 2 of DIP switch 26 is ON. When the operation is started by switch 25 after setting bit 2 to ON, the input / output interface (specifically, register) is reset by the aforementioned reset signal (OFF state) ) Subsequently, since the ON state to bit 2 is reflected in the register, this change is detected. If the operation is started by the switch 25 and then the ON state is set to the bit 2, it can be detected at the set timing.

Note that when a plurality of sets of control data C _i , Q _i , q _i (i = 1, 2, 3,...) Are prepared according to the outside air temperature by emulation or the like, the rewritable nonvolatile memory 31 can be used. In accordance with the temperature data from the temperature sensor 17 that monitors the environmental temperature of the fuel cell system 1, the control program selects and processes one of the control data. If the outside air temperature of the place of use is known in advance, the outside air temperature stage is set using the spare bit of the DIP switch 26, and the control program controls according to the setting of the spare bit of the DIP switch 26. Data may be selected.

  According to this embodiment, the startup time of the fuel cell system can be shortened.

  According to the present embodiment, the control amount is changed according to the exponential function, so that the startup time can be shortened immediately after the start of operation, and the steady state can be stabilized as the steady state is approached.

  According to the present embodiment, the control program is simply configured because it is activated by the periodic timer and executes the process of switching and setting the control data.

According to the present embodiment, a mode for emulation is provided, and it is easy to test the logic of the control program and determine control data C _i , Q _i , q _i (i = 1, 2, 3,...). .

  According to the present embodiment, since the control program selects and processes one of a plurality of sets of control data, control according to the outside air temperature is possible.

It is a block diagram of a fuel cell system. It is a figure explaining control by a controller. It is a block diagram of a controller. It is a processing flowchart of a control program.

Explanation of symbols

1: Fuel cell system, 2: Fuel cartridge, 3: Purified water cartridge, 4: DMFC stack, 5, 6: Mixing pump, 7, 8: Solenoid valve, 9: Mixing tank, 10: Concentration sensor, 11: Fuel pump , 12: Air pump, 13: Controller, 14: Li battery, 15, 16, 17: Temperature sensor, 18, 19: Remaining sensor, 20: Output interface, 21: Voltmeter, 22: Blower, 23: External interface 24: Communication connector 25: Switch / display 26: DIP switch 30: Processor 31, 32: Memory 33: Timer 34: Sensor interface 35: Control interface 36: Input / output interface 37: Communication interface.

Claims (9)

A DMFC (Direct Methanol Fuel Cell) stack that supplies an aqueous methanol solution of a predetermined concentration from the anode side, supplies air of a predetermined air volume from the cathode side, and generates electric power of the rated voltage through its chemical reaction,
In response to the start of operation of the DMFC stack, a mixing tank for supplying a methanol aqueous solution having a concentration higher than the predetermined concentration supplied from the anode side, and
In response to the start of operation of the DMFC stack, an air pump that supplies air of an air volume smaller than the predetermined air volume from the cathode side,
Having an air volume for cooling the methanol aqueous solution of the predetermined concentration in the mixing tank to a predetermined temperature;
In response to the start of operation of the DMFC stack, the air volume has a blower configured to maintain an air volume of methanol higher than the predetermined concentration at a temperature higher than the predetermined temperature,
From the start of operation of the DMFC stack until the generation of electric power of the rated voltage is reached, the concentration of the high concentration aqueous methanol solution in the mixing tank is controlled stepwise toward the predetermined concentration, and the predetermined air volume of the air pump A smaller air volume is controlled stepwise toward the predetermined air volume, and an air volume maintained at a temperature higher than the predetermined temperature of the blower is controlled stepwise toward the air volume cooled to the predetermined temperature. fuel cell system that. The stepwise control is executed such that a difference between the steps is reduced as time elapses from the start of operation of the DMFC stack to the generation of power of the rated voltage. 1. The fuel cell system according to 1 . The stepwise control of the concentration of aqueous methanol solution, according to claim 2, wherein the controller executes the air volume of stepwise control of the stepwise control and the blower of the air volume of the air pump, and further comprising Fuel cell system. The controller performs stepwise control of the concentration of the aqueous methanol solution, stepwise control of the air volume of the air pump, and stepwise control of the air volume of the blower based on predetermined control data by a control program. The fuel cell system according to claim 3 , wherein the fuel cell system is executed. 5. The fuel cell system according to claim 4 , wherein the control program selects the predetermined control data from a plurality of predetermined control data in response to an outside air temperature of the fuel cell system. Responding to the start of operation of the DMFC stack that generates power of rated voltage by a chemical reaction between a methanol aqueous solution of a predetermined concentration supplied from the anode side and a predetermined air volume of air supplied from the cathode side, cooled to a predetermined temperature,
Supplying a methanol aqueous solution having a concentration higher than the predetermined concentration from the anode side;
Supplying air from the cathode side with an air volume less than the predetermined air volume;
Maintaining a methanol aqueous solution having a concentration higher than the predetermined concentration at a temperature higher than the predetermined temperature;
From the start of operation of the DMFC stack until the generation of power at the rated voltage is reached, the concentration of the high-concentration aqueous methanol solution is controlled stepwise toward the predetermined concentration, and the predetermined air volume of air supplied to the cathode side A step of controlling a smaller amount of air toward the predetermined amount of air, and a step of controlling an amount of air that maintains the aqueous methanol solution at a temperature higher than the predetermined temperature toward the amount of air that is cooled to the predetermined temperature. method of controlling a fuel cell system that. The DMFC depending from the operation start of the stack to the elapsed time reaches the power generation of the power of the rated voltage, according to claim 6, wherein the performing each of the stepwise control such that the difference of each phase is reduced Control method for the fuel cell system of the present invention. 8. The fuel cell system according to claim 7 , wherein the concentration of the aqueous methanol solution, the amount of air supplied to the cathode, and the amount of air for cooling the aqueous methanol solution are controlled stepwise based on predetermined control data. Control method. 9. The control method for a fuel cell system according to claim 8, wherein the predetermined control data is selected from a plurality of predetermined control data in response to an outside air temperature of the fuel cell system.

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