WO2010073962A1

WO2010073962A1 - Fuel cell system and fuel cell

Info

Publication number: WO2010073962A1
Application number: PCT/JP2009/071048
Authority: WO
Inventors: 亮介八木; 康子乗富; 貴博鈴木; 裕輔佐藤; 典裕吉永
Original assignee: 株式会社東芝
Priority date: 2008-12-26
Filing date: 2009-12-17
Publication date: 2010-07-01

Abstract

A fuel cell system (101) is comprised of a power generating portion (5) having a plurality of laminated cells; a fuel supply portion (4) for supplying fuel to the cells, which can adjust the amount of fuel to be supplied; a voltage monitoring portion (8) for monitoring the output voltage of at least one specific cell (51) selected among the plural cells; a power supply portion (13) for temporarily supplying electric power to the specific cell; and a control portion (9) which detects a voltage difference between the minimum value of the output voltage occurring after electric power is supplied to the specific cell and the response value of the output voltage after the output voltage is reduced to the minimum value, and which controls the amount of fuel to be supplied in accordance with the voltage difference.

Description

Fuel cell system and fuel cell

The present invention relates to a fuel cell system and a fuel cell for controlling a polymer electrolyte fuel cell using liquid as a fuel.

The solid polymer fuel cell is known as a fuel cell that uses a polymer membrane having proton conductivity, sometimes called a proton exchange membrane fuel cell, as an electrolyte. One of the polymer electrolyte fuel cells (PEFC) is a direct methanol fuel cell (DMFC). This direct methanol fuel cell is portable because it does not require an auxiliary device such as a vaporizer or a humidifier, it is easier to handle methanol than a gaseous fuel such as hydrogen, and it can be operated at low temperatures. Development is progressing as a small power source for industrial equipment.

A direct methanol fuel cell has a membrane electrode assembly (MEA). The membrane electrode assembly includes an anode electrode (also referred to as a fuel electrode), a cathode electrode (also referred to as an air electrode), and a solid polymer membrane that is sandwiched between them and transmits protons. An aqueous methanol solution is supplied to the anode electrode, and air is supplied to the cathode electrode.

At the anode of MEA, the reaction of the following formula (1) occurs, and carbon dioxide, protons, and electrons are generated by the electrochemical reaction between methanol and water.

Further, the reaction of the following formula (2) occurs at the cathode electrode of MEA, and water is generated by the electrochemical reaction of protons, electrons, and oxygen.

The water generated by the reaction of the formula (2) is removed from the cathode electrode by diffusion into the air supplied to the cathode electrode or moving through the solid polymer membrane to the anode electrode, but remains without being removed. Water accumulates inside the cathode. If this accumulated water is not properly removed, the air diffusivity is lowered, causing a reduction in output voltage.

Further, in the direct methanol fuel cell, methanol crossover occurs in which part of methanol contained in the methanol aqueous solution supplied to the anode electrode moves directly from the anode electrode to the cathode electrode. In addition to the reaction, the reaction of the following formula (3) occurs.

If the methanol at the anode electrode is consumed by the methanol crossover reaction shown in Formula (3), the fuel utilization efficiency decreases. Therefore, in order to increase the fuel utilization efficiency, it is desirable to control the amount of methanol supplied to the power generation unit by the fuel concentration, the fuel flow rate, etc., and to keep the methanol crossover within a predetermined range.

In addition, since water is generated by the methanol crossover reaction in addition to the reaction of the formula (2) at the cathode electrode, the amount of water at the cathode electrode increases unless air is appropriately removed from the cathode electrode. The diffusion resistance increases and the output voltage decreases. A decrease in output voltage causes a decrease in power generation efficiency.

Therefore, in order to increase the output voltage obtained from the power generation section, it is desirable to detect water accumulation (flooding) in the cathode electrode in advance and suppress it.

Here, the fuel utilization efficiency is defined by the reaction of the formula (2) / {the reaction of the formula (2) + the formula (3)}, and the higher the methanol crossover value of the formula (3), the higher the methanol (fuel). The utilization efficiency of is reduced.

Also, the power generation efficiency is defined as MEA voltage / theoretical voltage × fuel utilization efficiency, and the higher the MEA voltage, the higher the power generation efficiency.

Therefore, in Patent Document 1, the load of the power generation unit is switched from a closed circuit to an open circuit in order to keep the methanol crossover within a predetermined range and increase the two efficiency of fuel use efficiency and power generation efficiency, and after switching, the constant A method for detecting the methanol concentration based on the output voltage after time has been proposed. In this method, since the output voltage value of the power generation unit is used as an evaluation value, there is an advantage that a concentration sensor is not required and the apparatus can be downsized.

In a power generation unit configured by stacking a plurality of cells, a methanol aqueous solution having a predetermined concentration is supplied to the anode electrode of each cell through a fuel supply unit. The cell in the central region and the cell in the end region with respect to the power generation unit stacking direction may be affected by environmental factors such as the outside air temperature, resulting in a difference in cell temperature. Thus, when temperature variation occurs between cells, in a cell having a high temperature, the methanol crossover of Formula (3) becomes high, and the fuel utilization efficiency decreases. Therefore, the power generation efficiency decreases.

On the other hand, an aqueous methanol solution having the same concentration as that of the high temperature cell is supplied. However, in the low temperature cell due to factors of the external environment, the overvoltage of the formula (1) increases and the voltage decreases. Power generation efficiency will decrease. Further, compared with a cell having a high temperature, the fuel diffusibility of the anode is lowered in a cell having a low temperature, so that the load current that can be taken out from the cell is reduced. In this case, there arises a problem that the power generation amount decreases.

For example, when the power generation unit is started up in a low temperature environment, among the stacked cells, the cell at the end adjacent to the outside air may be affected by the outside air temperature and the temperature rise rate may be slow. At this time, in the end cell having a low temperature, the load current that can be taken out decreases due to the decrease in the fuel diffusibility. In this case, the maximum load that can be taken out from the power generation unit is limited by the load of the end cell. Therefore, there is a problem that the power generation amount and the starting speed are reduced from the low temperature start to the steady state where a predetermined power generation amount is obtained.

Therefore, in Patent Document 2, a device has been devised in which a conductive dummy cell having heat insulation is arranged at the end of the power generation unit to suppress a temperature drop in the end region and to suppress temperature variation between the cells. Moreover, in patent document 3, the device is provided with a resistor in at least one end region of both ends in the stacking direction of the power generation unit to suppress a temperature drop in the end region and suppress a temperature variation between cells. ing. Furthermore, in Patent Document 4, fuel having a lower heat capacity than that during normal operation is supplied to the anode at startup, and fuel at the anode outlet is circulated again to the anode inlet, thereby speeding up startup of the power generation cell.

JP 2005-285628 A JP 2007-250338 A JP-A-2005-174600 JP 2008-257945 A

As described above, there is a problem in that the power generation efficiency and the power generation amount of the entire power generation unit are reduced under conditions where the temperature characteristics and output (voltage) characteristics between the cells of the power generation unit are different. In addition, in order to increase the power generation efficiency of the power generation unit, it is necessary to simply detect the methanol crossover of the power generation unit and keep the methanol crossover within a predetermined range.

The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide a fuel cell system and a fuel cell capable of stable operation over a long period of time.

One aspect of the present invention includes a power generation unit having a plurality of stacked cells, a fuel supply unit capable of supplying fuel to the cells, the fuel supply amount being adjustable, and at least one specific cell among the plurality of cells. A voltage monitoring unit that monitors the output voltage, a power supply unit that temporarily supplies power to the specific cell, a minimum value of the output voltage that appears after the power is supplied to the specific cell, and the output voltage A fuel cell system is provided that includes a control unit that detects a voltage difference from the response value of the output voltage after the value reaches a minimum value and controls the fuel supply amount according to the voltage difference.

In another aspect of the present invention, a power generation unit having a plurality of stacked cells, a temperature monitoring unit that monitors the temperature of at least one specific cell among the plurality of cells, and temporarily supplying power to the specific cell. A fuel cell system is provided, comprising: a power supply unit that supplies the power to the specific cell, and a control unit that supplies the power to the specific cell according to the temperature.

According to another aspect of the present invention, a power generation unit having a plurality of stacked cells, a voltage monitoring unit that monitors a voltage of at least one specific cell among the plurality of cells, and temporarily supplying power to the specific cell. A fuel cell system is provided, comprising: a power supply unit that supplies the power to the specific cell, and a control unit that supplies the power to the specific cell according to the voltage.

In another aspect of the present invention, the power generation unit includes a plurality of stacked cells, and a power supply unit that temporarily supplies power to at least one specific cell among the plurality of cells. A fuel cell is provided.

Therefore, according to the present invention, it is possible to provide a fuel cell system and a fuel cell that enable stable operation over a long period of time.

FIG. 1 is a diagram illustrating a configuration example of a fuel cell system according to the first embodiment. FIG. 2 is a diagram illustrating details of the configuration of the power generation unit illustrated in FIG. 1. FIG. 3 is a diagram showing the response characteristics of the cell voltage. FIG. 4 is a diagram illustrating an example of the relationship between the air flow rate and the time evaluation value. FIG. 5 is a flowchart illustrating a processing procedure of the system according to the first embodiment. FIG. 6 is a diagram showing the response characteristics of the cell voltage. FIG. 7 is a flowchart illustrating a processing procedure of the system according to the second embodiment. FIG. 8 is a flowchart illustrating the processing procedure of the system according to the third embodiment. FIG. 9 is a diagram illustrating a configuration example of a fuel cell system according to the fourth embodiment. FIG. 10 is a diagram illustrating details of the configuration of the power generation unit according to the fourth embodiment. FIG. 11 is a diagram relating to a system control method according to the fourth embodiment. FIG. 12 is a flowchart illustrating a processing procedure of the control unit according to the fourth embodiment. FIG. 13 is a diagram illustrating a configuration example of a fuel cell system according to the fifth embodiment. FIG. 14A is a graph showing a load current and an external power supply current to a specific cell in Example 1. FIG. 14B is a graph showing the output voltage of the power generation unit and the voltage of a specific cell in Example 1. FIG. 15A is a graph showing the load current in Comparative Example 1. FIG. 15B is a graph showing the output voltage of the power generation unit and the voltage of a specific cell in Comparative Example 1. FIG. 16 is a diagram illustrating a configuration example of a fuel cell system according to the sixth embodiment. FIG. 17A is a diagram illustrating details of the configuration of the power generation unit according to the sixth embodiment. FIG. 17B is a diagram illustrating a configuration of a specific cell unit. FIG. 17C is a diagram illustrating a configuration of cells other than the specific cell. FIG. 18 is a diagram relating to a system control method according to the sixth embodiment. FIG. 19 is a flowchart illustrating a processing procedure of the control unit according to the sixth embodiment. FIG. 20A is a diagram illustrating details of the configuration of the power generation unit according to the seventh embodiment. FIG. 20B is a diagram illustrating a configuration of a specific cell. FIG. 20C is a diagram illustrating a configuration of cells other than the specific cell. FIG. 21 is a flowchart illustrating a processing procedure of the control unit according to the seventh embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a configuration of a fuel cell system 1 according to a first embodiment of the present invention. The fuel cell system 1 includes a power generation unit 5 having a cell stack structure 50 as shown in FIG. 2 and a fuel tank that stores liquid fuel such as high-concentration methanol or a mixed solution of methanol fuel and a small amount of water (methanol aqueous solution). 3, the auxiliary devices 2 that support the power generation in the power generation unit 5, and the electric power generated by the power generation unit 5 are controlled by the external power source (for example, a lithium ion battery) and the power extracted from the power generation unit 5. A power adjustment unit 10.

The auxiliary devices 2 include a fuel supply unit 4 that supplies fuel from the fuel tank 3 to the power generation unit 5, an air supply unit 6 that supplies air to the power generation unit 5, and a load that adjusts the load current extracted from the power generation unit 5. The adjustment unit 7, the cell voltage monitoring unit 8 that monitors the output voltage of each cell of the cell stack structure 50, and the control unit 9 for controlling each unit in the auxiliary devices 2 are provided.

The control unit 9 includes a detection processing unit 9a that detects the state of each unit of the auxiliary devices 2, and a database 9b in which control information for controlling each unit according to the detected information is stored in advance. The control unit 9 detects necessary information from each unit of the power generation unit 5 and the auxiliary devices 2 and processes or calculates the detected information. Further, the control unit 9 gives control signals to the fuel supply unit 4, the power generation unit 5, the load adjustment unit 7, and the air supply unit 6 according to the result of this processing or calculation. As will be described later, the database 9b includes a database that describes in advance how each part of the auxiliary equipment 2 is controlled based on values measured from the cells.

The power generation unit 5 is connected to the load power 11 through the load adjustment unit 7 and the power adjustment unit 10. The load power 11 corresponds to, for example, an electronic device driven by power generated by the fuel cell system 1. The power adjustment unit 10 supplies the power generated by the power generation unit 5 to the load power 11. Adjustment of the electric power taken out from the power generation unit 5 is performed by the load adjustment unit 7 adjusting the load current. When the power generated by the power generation unit 5 is insufficient with respect to the power required for the load power 11, the power adjustment unit 10 is not shown in the figure, but from an external power source (for example, a lithium ion battery or a capacitor). Make up for the power shortage. The power adjustment unit 10 includes a switching circuit that turns on or off the supply of power generated by the power generation unit 5 to the load power 11. The power adjustment unit 10 is configured to be connected to the load power 11 in the on state to be in a closed circuit state, disconnected from the load power 11 in the off state, and to be in an open circuit state on the output side.

The power generation unit 5 and the auxiliary devices 2 are connected by a fluid piping system. In this fluid piping system, the fuel tank 3 and the fuel supply unit 4 are connected by a fuel supply line L1. The fuel supply unit 4 and the power generation unit 5 are connected by a fuel supply line L2. The fuel in the fuel tank 3 is supplied to the anode electrode of the power generation unit 5 by adjustment in the fuel supply unit 4. The air supply unit 6 and the power generation unit 5 are connected by an air supply line L <b> 3, and air is sent to the cathode electrode of the power generation unit 5 by adjustment in the air supply unit 6.

In the system shown in FIG. 1, the fuel in the fuel tank 3 is directly supplied to the power generation unit 5. However, the present invention is not limited to this, and the fuel in the fuel tank 3 is diluted with fuel. You may make it the system which mixes with the fuel remaining in the electric power generation in the power generation part 5 by supplying in the mixing tank to store.

In addition, the power generation unit 5 and the auxiliary devices 2 are connected by a signal and current wiring system. The control unit 9 is connected to the fuel supply unit 4 via the signal line E1. The power generation unit 5 and the control unit 9 are connected by a signal line E2. The load adjustment unit 7 and the control unit 9 are connected by a signal line E3. The cell voltage monitoring unit 8 and the control unit 9 are connected by a signal line E4. The air supply unit 6 and the control unit 9 are connected by a signal line E5.

The flow rate of fuel supplied from the fuel supply unit 4 to the power generation unit 5 is measured. The fuel flow rate information representing the measured flow rate is sent to the control unit 9 via the signal line E1. A supply amount control signal that determines the supply flow rate is sent from the control unit 9 to the fuel supply unit 4 via the signal line E1. Fuel is supplied from the fuel supply unit 4 to the power generation unit 5 in accordance with the supply amount control signal. Here, the fuel supplied to each cell 51 may be adjusted for each cell 51 by providing a fuel flow rate adjustment valve (not shown) in the flow path of the fuel flowing into each cell 51.

In addition, information representing the stack voltage (the voltage of the entire cell) generated and output from the cell stack structure 50 in the power generation unit 5 is sent to the control unit 9 via the signal line E2 as voltage information. The power adjustment unit 10 is connected to the load adjustment unit 7 via a line E6. The load adjustment unit 7 applies a load to the power generation unit 5 through the signal line E3. The value of the load current detected by the load adjustment unit 7 is sent to the control unit 9 via the signal line E3 as load current information. The load control signal set by the control unit 9 is given from the control unit 9 to the load adjustment unit 7 via the signal line E3. Therefore, the load adjustment unit 7 connects a load corresponding to the set load determined according to the load control signal to the power generation unit 5, and the load current flowing through the set load is detected and sent to the control unit 9 as load current information. .
Note that the power adjustment unit 10 can be omitted by providing the load adjustment unit 7 with the role of the power adjustment unit 10. In this case, the load power 11 is connected to the load adjustment unit 7.

The cell voltage monitoring unit 8 includes a cell voltage detection circuit (not shown) that detects a voltage generated in at least one predetermined cell, and the cell stacked structure 50 in the power generation unit 5 via the signal line E4. Are connected to the above cells. The voltage generated in each cell is measured by the cell voltage detection circuit, and the measured cell voltage value is sent to the control unit 9 as voltage information. Here, the predetermined cells are all the cells 51 included in the cell stack structure 50, but in addition to this, only a plurality of cells 51 are selected from the cell stack structure 50, and those cells 51 are selected. It can also be a combined voltage. Alternatively, only a specific cell 51 can be selected as a predetermined cell. For example, when the cell stack 50 has a large number of cells 51, the cell voltage monitoring unit 8 does not detect the voltages of all the cells 51, but selects two to three adjacent cells 51, Can be the voltage at a predetermined cell.

The power generation unit 5 includes a cell stack structure 50 as shown in FIGS. 2 (a) and 2 (b). As shown in FIG. 2A, the cell stack structure 50 includes a plurality of cells 51 stacked between the anode current collector plate 12 and the cathode current collector plate 14, and each cell 51 includes the anode current collector plate 12. The cathode current collector plate 14 is electrically connected in series. The cell 51 stacked between the anode current collector plate 12 and the cathode current collector plate 14 is disposed between a pair of clamping

plates

18A and 18B, and is clamped and fixed by

fixtures

19A and 19B between the clamping

plates

18A and 18B. Has been. The anode current collecting plate 12 and the cathode current collecting plate 14 are connected to the load adjusting unit 8, respectively, and the current generated by the cell stack structure 50 is collected by the cathode current collecting plate 14 and supplied to the load adjusting unit 7.

The cell 51 includes a membrane electrode assembly (referred to as MEA) 20 as shown in FIG. An anode flow path plate 22 is provided on one side of the membrane electrode assembly 20, and a cathode flow path plate 24 is provided on the other side. The MEA 20 is sandwiched between the anode flow path plate 22 and the cathode flow path plate 24 and formed in a structure sealed with a gasket 26 connected to the anode flow path plate 22 and the cathode flow path plate 24. The anode flow path plate 22 and the cathode flow path plate 24 are insulated by the gasket 26, and the leakage of fuel and air from the MEA 20 to the outside is prevented by the gasket 26. The MEA 20 has an anode electrode formed on one side of the electrolyte membrane and a cathode electrode formed on the other side of the electrolyte membrane.

The anode flow path plate 22 of each cell 51 is electrically and mechanically connected to the cathode flow path plate 24 of the adjacent cell 51, and the cathode flow path plate 24 of each cell 51 is the anode flow path of the adjacent cell 51. The stacked cells 51 that are electrically and mechanically connected to the plate 22 are connected in series to each other. The cell 51 connected to the cell voltage monitoring unit 8 is provided with

output terminals

22A and 24A on the anode flow path plate 22 and the cathode flow path plate 24 in order to monitor the voltage generated by the cell 51 from the outside. ing. The

output terminals

22A and 24A are connected to the voltage detection circuit of the cell voltage monitoring unit 8 through the cell voltage signal line E4, and the cell voltage monitoring unit 8 monitors (monitors) the voltage of each cell 51. From the cell voltage monitoring unit 8, voltage information representing a voltage value corresponding to a voltage generated in a predetermined cell is supplied to the detection processing unit 9a of the control unit 9 via the signal line E4.

The anode channel plate 22 faces the anode electrode side of the MEA 20 and is formed with a channel through which fuel such as methanol and aqueous methanol solution is circulated. The fuel is supplied to the MEA 20 through this flow path, and the gas generated by the reaction in the MEA 20 is discharged through the flow path of the anode flow path plate 22. The cathode channel plate 24 is formed with a channel through which air flows while facing the cathode electrode side of the MEA 20. Air is supplied to the MEA 20 through the channel, and is generated by a reaction in the MEA 20. The water that has passed through is discharged through the channel of the cathode channel plate 24.

The membrane electrode assembly (MEA) 20 forms a catalyst layer by applying a catalyst layer on both sides of a solid polymer membrane, and smoothly collects current, supplies fuel, and discharges a reaction product outside the catalyst layer. It is formed by joining gas diffusion layers for the purpose. As the solid polymer membrane, for example, an ion exchange membrane made of Nafion (registered trademark) manufactured by DuPont can be used. As the anode catalyst (anode electrode film) and the cathode catalyst (cathode electrode film), a commercially available Pt—Ru catalyst, Pt catalyst, or the like can be used. Commercially available carbon paper, carbon fiber, and carbon nonwoven fabric can be used as the gas diffusion layer. These diffusion layers may be provided with a dense layer (Micro Porous Layer) mainly composed of carbon and a water-repellent material.
The anode flow channel plate 22 and the cathode flow channel plate 24 are respectively supplied with fuel and discharge of the reaction product to the anode electrode of the MEA 20, supply of air and discharge of the reaction product to the cathode electrode, and electricity generated by the reaction. The anode channel plate 22 and the cathode channel plate 24 can have any shape as long as this purpose is achieved. For example, a serpentine channel plate can be used for the anode channel plate 22.

Next, the operation of the fuel cell system 1 shown in FIG. 1 will be described.
When starting power generation, the fuel supply unit 4 supplies a methanol aqueous solution (fuel) having a predetermined concentration from the fuel tank 3 to the anode flow path plate 22 via the flow paths L1 and L2 under the control of the control section 9. Supply. The air supply unit 6 supplies air to the cathode flow path plate 24 through the flow path L3 under the control of the control unit 9. Thereby, on the anode side of the anode flow path plate 22, the fuel penetrates from the flow path through which the fuel flows to the anode electrode. On the cathode side of the cathode channel plate 24, air is permeated from the channel through which air flows into the cathode electrode.

When a load connected to the cell stack structure 50 is applied by the load adjusting unit 7, the methanol oxidation reaction represented by the formula (1) occurs on the anode electrode, that is, the anode side of the MEA 20. At the cathode electrode, that is, the cathode side of the MEA 20, the oxygen reduction reaction represented by the formula (2) occurs. The electrons (e−) flow to the load adjusting unit 7.

The protons (H +) generated by the anode catalyst flow from the anode electrode to the cathode electrode through the solid polymer membrane. At this time, methanol flows simultaneously with protons through the solid polymer membrane to the cathode electrode. The methanol flowing to the cathode electrode undergoes the reaction of the formula (3) on the cathode side, and water is generated at the cathode electrode (methanol crossover). When water is contained in the fuel in the fuel tank 3, water also flows into the cathode electrode through the solid polymer membrane simultaneously with protons. If power generation is continued in this way, water accumulates in the cathode electrode, and if the accumulated water is not properly removed from the cathode electrode, air diffusibility is reduced. Thus, when the air diffusibility is lowered, the diffusion resistance is increased, so that the output voltage from each cell 51 is lowered and the power generation efficiency is lowered. Therefore, in the first embodiment, the power generation efficiency is improved by providing a process for improving the air diffusibility of the cell 51. The method will be described below.

With reference to FIG. 3, the process which detects the cell 51 in which the air diffusibility fell and improves the air diffusibility of the said cell is demonstrated.
FIG. 3 shows the cell voltage output from each cell 51 when the load is switched by the load adjusting unit 7 and the load current I taken out from the cell stack structure 50 is changed stepwise from the load current I1 to the load current I2. Response characteristics CR ¹ , CR ² , CR ³ , CR ⁴ are shown. These CR ¹ , CR ² , CR ³ , and CR ⁴ represent the cell voltage characteristics measured in the ^four cells 51 ¹ to 514 in the cell stack structure 50 in which the ^four cells 51 ¹ to 51 ⁴ are stacked. ing. Each of the cells 51 ¹ to 51 ⁴ is connected to the cell voltage monitoring unit 8, the voltages of the cells 51 ¹ to 51 ⁴ are individually monitored, and voltage information is supplied to the detection processing unit 9a.

In FIG. 3, superscript suffixes (subscripts) 1 to 4 indicate the cell numbers 1 to 4 of the four cells 51, and the subscript suffix “1” denotes the minimum voltage value V ₁ (minimum voltage value). ) And the time point T _{1 at} which the minimum voltage value V ₁ is reached.

In the graph shown in FIG. 3, during the period before time T = T ₀ , the load adjustment unit 7 selects the first load, and the load current I = I 1 is extracted from the cell stack structure 50. At time T = T ₀ , the load in the load adjusting unit 8 is changed from the first load to the second load, and the load current I to be extracted is increased in a stepped manner from I = I1 to I = I2. As the load current I fluctuates, at time T = T ₁ ⁿ immediately after switching to the second load, the cell voltage V of the ^nth cell (n is 1 to 4) is V = V ₁ ⁿ . The minimum voltage value (minimum voltage value) is reached, and then each voltage V gradually converges to a substantially constant value after reaching the maximum voltage value. Here, a time ΔT ₁ ⁿ = T ₁ ⁿ −T ₀ until the output voltage of each cell reaches the minimum value from the start of load fluctuation is defined as a time evaluation value, and each cell is defined using this time evaluation value ΔT ₁ ^n. The air flow rate of 51 is estimated. One of the first load and the second load may be in a no-load state.

Under the same conditions and the same environment such as the same fuel flow rate, air flow rate, and temperature in all the cells 51, the time evaluation value ΔT ₁ ⁿ of each cell 51 is almost the same value. However, when a specific failure (abnormality) occurs in a specific cell 51, such as a decrease in local air inflow due to an uneven air distribution or water accumulation (flooding) in the cathode electrode (hereinafter referred to as “abnormality”). This is simply referred to as cell abnormality), and the time evaluation value ΔT ₁ ⁿ of each cell varies.

Hereinafter, the cell voltage is monitored by the cell voltage monitoring unit 8, the time evaluation value ΔT ₁ ^{n of} each cell is obtained by the detection processing unit 9a, and the air supply unit 6 is controlled based on the time evaluation value ΔT ₁ ^n. Will be explained.

FIG. 4 is an example in which the relationship between the air inflow amount of the cell 51 and the time evaluation value ΔT ₁ ⁿ is obtained by experiments. In FIG. 4, in a cell 51 in the cell stack structure 50, the methanol concentration of the fuel supplied to the anode electrode is 1.6 mol / L, and the air flow rate per unit area supplied to the cathode electrode is 4 to 10 cc / min / in the case of changing cm ^2, and the results obtained by plotting the response time evaluation value [Delta] T ₁ ^n. FIG. 4 shows that ΔT ₁ ⁿ increases as the air flow rate decreases, and conversely, when the air flow rate is increased beyond a certain level, ΔT ₁ ⁿ changes less with changes in the air flow rate. If the operation is continued in a state where the air flow rate is reduced, the discharge of water from the cathode electrode is lowered, so that the air diffusibility is lowered and the output voltage is lowered. In addition, when the discharge of water decreases for a long period of time, water accumulation (flooding) occurs in the cathode electrode, causing a further decrease in output voltage. Therefore, ΔT ₁ ⁿ is detected by the method shown in FIG. 3, and the air flow rate supplied to the cell 51 is estimated using the detected value, and a process for keeping the flow rate within a predetermined range is incorporated.

FIG. 5 shows a processing procedure of the system in the first embodiment. The control operation of the control unit 9 will be described with reference to FIG.
When the control operation is started in the control unit 9 (step S01), the detection processing unit 9a gives an instruction for load variation processing to the load adjustment unit 7 (step S02). In accordance with this instruction, the load adjustment unit 7 adjusts the load current extracted from the power generation unit 5 from the first value to the second value (step S03). Simultaneously with the change to the second value by the load adjustment unit 7, the cell voltage monitoring unit 8 measures the voltage value of each cell 51 with the time by the voltage detection circuit in the cell voltage monitoring unit 8 (step S04). As a result, voltage information that varies with time for each cell 51 is input from the cell voltage monitoring unit 8 to the detection processing unit 9a. The detection processing unit 9a detects the minimum voltage value V ₁ ⁿ from the input voltage information, and detects the time ΔT ₁ ⁿ from the load fluctuation start T ₀ until the minimum voltage value V ₁ ⁿ is obtained (step S05). . The detected time ΔT ₁ ⁿ is stored in the ΔT ₁ ⁿ detection database 9b-1 of the database 9b.

The detection processing unit 9a determines whether ΔT ₁ ⁿ is within a predetermined range (step S06). Here, as a method for determining ΔT ₁ ⁿ stored in the ΔT ₁ ⁿ detection database 9b-1, a predetermined minimum time value ΔT _min (ΔT _min includes 0) as shown in the following equation (4). ) And the maximum time value ΔT _max is determined as a normal cell, and when it is not satisfied, it is determined as an abnormal cell.

In addition, a frequency distribution S (ΔT ₁ ⁿ ) is calculated from ΔT ₁ ⁿ obtained in each cell 51, and from the frequency distribution, a cell whose variance is within a predetermined range is determined as a normal cell, and the range A cell that is not within can be determined as an abnormal cell. When the calculated frequency distribution S (ΔT ₁ ⁿ ) has two or more peaks, the value of the peak with the smaller ΔT ₁ ⁿ or the average value thereof can be used. In addition, when ΔT ₁ ⁿ is equal to or smaller than a predetermined reference value, it is determined as a normal cell, and when ΔT ₁ ⁿ is larger than the reference value, it may be determined as an abnormal cell.

If there is an abnormal cell in step S06, the detection processing unit 9a instructs a process for recovering the abnormal cell (step S07). The timing of the recovery process may be, for example, at the end of the fuel cell system 1, may be performed immediately during operation, or at least M (M: any natural number) or more cells. It may be performed only when an abnormality occurs.

When the recovery processing command is issued in step S07, the detection processing unit 9a outputs a control signal instructing an increase in the air supply amount to the air supply unit 4 (step S08). In order to determine the conditions for increasing the air supply amount, ΔT ₁ ⁿ -supply amount control database 9b-2 stored in advance in the database 9b is used. Based on this ΔT ₁ ⁿ -supply amount control database 9b-2, the control unit 9 sends a supply amount control signal to the air supply unit 6, and the air supply unit 6 adjusts the air supply amount (step S09). .

In the conventional method, the load of the power generation unit is switched from a closed circuit to an open circuit in order to keep the methanol crossover within a predetermined range and improve the fuel utilization efficiency and the power generation efficiency, and the output after a certain time after switching The methanol concentration was detected based on the voltage. However, since it takes time from the time when the load of the power generation unit is switched from the closed circuit to the open circuit until the output voltage is stabilized, it has been a problem to increase the detection speed of the methanol concentration. In addition, since the output voltage of the power generation unit changes due to deterioration over time and the like, there is a problem of stability in detection accuracy of methanol concentration. In addition, when the power generation unit is composed of a plurality of cells, the output voltage characteristics of each cell vary, and therefore the methanol concentration detection varies depending on which cell voltage value is used.

Therefore, in the first embodiment, a power generation unit having a plurality of stacked cells, a fuel supply unit that supplies fuel to the cells, a fuel supply amount that can be adjusted, and supplies air to the cells. An air supply unit capable of adjusting an air supply amount; a voltage monitoring unit that monitors an output voltage of at least one of the plurality of cells; an adjustment unit that adjusts a load current extracted from the power generation unit; and the load A time measuring unit that measures a time from when the current is adjusted from the first value to the second value until the output voltage reaches the minimum value; and, depending on the time, the air supply amount and the fuel supply amount Provided is a fuel cell system including a control unit that controls at least one of them.

That is, in the first embodiment, the time ΔT ₁ ⁿ until the output voltage of each cell reaches the minimum value from the start of load fluctuation is detected, and air supply is performed so that the value of ΔT ₁ ⁿ falls within a predetermined range. Control the amount. By doing in this way, it becomes possible to suppress the fall of the output voltage by the fall of the air diffusibility in the cathode pole of the cell 51, and can improve electric power generation efficiency.

(Second Embodiment)
The second embodiment estimates the methanol crossover by using the method for detecting the time ΔT ₁ ⁿ described in the first embodiment, thereby improving not only the power generation efficiency but also the fuel utilization efficiency. Provide a system.

With reference to FIG. 6, the estimation method of methanol crossover is demonstrated.
FIG. 6 shows the cell voltage output from each cell 51 when the load is switched by the load adjusting unit 7 and the load current I taken out from the cell stack structure 50 is changed stepwise from the load current I1 to the load current I2. Response characteristics CR ¹ , CR ² , CR ³ , CR ⁴ are shown. These CR ¹ , CR ² , CR ³ , and CR ⁴ represent the cell voltage characteristics measured in the ^four cells 51 ¹ to 514 in the cell stack structure 50 in which the ^four cells 51 ¹ to 51 ⁴ are stacked. ing. Each of the cells 51 ¹ to 51 ⁴ is connected to the cell voltage monitoring unit 8, the voltages of the cells 51 ¹ to 51 ⁴ are individually monitored, and the cell voltage signal is supplied to the detection processing unit 9a.

In FIG. 6, the superscript suffixes (subscripts) 1 to 4 indicate the cell numbers 1 to 4 of the four cells 51, and the subscript suffix “1” denotes the minimum voltage value V ₁ (minimum voltage value). ) And the time point T _{1 at} which the minimum voltage value V ₁ is reached. The subscript suffix "2" indicates a maximum voltage value when T ₂ to be and the maximum voltage value (maximum value of the voltage) to output応値appearing after the minimum voltage. The subscript “3” indicates the steady voltage V ₃ that is the output response that appears after the minimum voltage and the time T ₃ when the steady voltage V ₃ is reached.

In the time period before time T = T ₀ in the graph shown in FIG. 6, the load adjustment unit 8 selects the first load, and the load current I = I 1 is taken out from the cell stack structure 50. At time T = T ₀ , the load in the load adjusting unit 8 is changed from the first load to the second load, and the load current I to be extracted is increased in a stepped manner from I = I1 to I = I2. As the load current I fluctuates, at time T = T ₁ ⁿ immediately after switching to the second load, the cell voltage V of the ^nth cell (n is 1 to 4) is V = V ₁ ⁿ . After reaching the minimum voltage value (minimum voltage value), each cell voltage V reaches the maximum voltage value V ₂ ⁿ (maximum voltage value) and then gradually becomes a substantially constant value (steady voltage V ₃ ⁿ ). To converge.

Here, a first voltage difference ΔV ₂ ⁿ (ΔV ₂ ⁿ = V ₂ ⁿ −V ₁ ⁿ ) is generated between the minimum voltage value V ₁ ⁿ and the maximum voltage value V ₂ ⁿ . Further, a second voltage difference ΔV ₃ ⁿ (ΔV ₃ ⁿ = V ₃ ⁿ −V ₁ ) between the minimum voltage value V ₁ ⁿ and a steady voltage V ₃ ⁿ after a certain time (for example, T = T ₃ ) has elapsed. ⁿ ). The methanol crossover of each cell 51 is estimated using the first voltage difference ΔV ₂ ⁿ and the second voltage difference ΔV ₃ ⁿ . One of the first load and the second load may be in a no-load state.

In the following description, the time point T ₁ ⁿ is defined as the time when the nth cell 51 ⁿ becomes the minimum voltage value V ₁ ⁿ immediately after the load change. The time point T ₂ ⁿ is determined as the time when the n-th cell 51 ⁿ reaches the maximum voltage value V ₂ ⁿ immediately after the load change. The time T ₃ is defined as the time when all the cells 51 ¹ to 51 ⁿ converge to the steady voltage V ₃ ⁿ after reaching the minimum voltage value V ₁ ⁿ and the maximum voltage value V ₂ ⁿ . The time T ₃ can be all n cells is arbitrarily set as long as it is after the lapse of the minimum voltage value V _{1 ^n,} the maximum voltage value V ₂ ^n. Here, although the time T ₁ ⁿ varies for each cell 51 ⁿ , the tendency observed within 10 seconds after the load change has been confirmed by experiments. Therefore, for example, the time point T3 can be determined between 10 seconds and 60 seconds after the load change.

The relationship between the first voltage difference ΔV ₂ ⁿ output from each cell 51 and the methanol crossover when all the cells 51 are placed under the same conditions and the same environment such as the same fuel flow rate, air flow rate and even the same temperature. Can be approximated by a generally unique linear relationship. Further, the relationship between the second voltage difference V ₃ ⁿ and the methanol crossover can also be approximated to a substantially unique linear relationship.

However, when an increase or decrease in the air flow rate due to air distribution or accumulation (flooding) of water inside the cathode electrode occurs in a specific cell 51, the relationship between the first voltage difference ΔV ₂ ⁿ and the methanol crossover, and The relationship between the second voltage difference ΔV ₃ ⁿ and the methanol crossover does not become a unique linear relationship, and the methanol crossover cannot be correctly estimated. Therefore, the time evaluation value ΔT ₁ ⁿ detected in the first embodiment is taken in, and the methanol cross using the time evaluation value ΔT ₁ ⁿ , the first voltage difference ΔV ₂ ^n, and the second voltage difference ΔV ₃ ^n. Control over.

Thereafter, the cell voltage is monitored by the cell voltage monitoring unit 8, and a first voltage difference ΔV ₂ ⁿ between the minimum voltage value V ₁ ⁿ and the maximum voltage value V ₂ ^{n that} is an output response appearing after the minimum voltage is detected. A basic principle of processing for estimating and controlling methanol crossover based on the first voltage difference ΔV ₂ ⁿ obtained by the processing unit 9a will be described.

FIG. 7 shows a processing procedure of the system in the second embodiment. The control operation of the control unit 9 will be described with reference to FIG. In FIG. 7, the same parts as those in FIG.
When the control operation is started in the control unit 9 (step S01), the detection processing unit 9a gives an instruction for load variation processing to the load adjustment unit 7 (step S02). In accordance with this instruction, the load adjustment unit 7 adjusts the load current extracted from the power generation unit 5 from the first value to the second value (step S03). Simultaneously with the change to the second value by the load adjustment unit 7, the cell voltage monitoring unit 8 measures the voltage value of each cell 51 with the time by the voltage detection circuit in the cell voltage monitoring unit 8 (step S04). As a result, voltage information that varies with time for each cell 51 is input from the cell voltage monitoring unit 8 to the detection processing unit 9a.

The detection processing unit 9a detects the minimum voltage value V ₁ ⁿ from the input voltage information, and detects the time ΔT ₁ ⁿ from the load fluctuation start T ₀ until the minimum voltage value V ₁ ⁿ is obtained (step S05). . The detected time ΔT ₁ ⁿ is stored in the ΔT ₁ ⁿ detection database 9b-1 of the database 9b. Furthermore, the detection processing unit 9a detects the maximum voltage value V ₂ ⁿ from the input voltage information, and determines the difference between the detected minimum voltage value V ₁ ⁿ and the maximum voltage value V ₂ ⁿ as the first voltage. The difference ΔV ₂ ⁿ is detected (step S20). The detected first voltage difference ΔV ₂ ⁿ is stored in the ΔV ₂ ⁿ detection database 9b-3 of the database 9b.

Next, the detection processing unit 9a determines whether or not ΔT ₁ ^{n of} each cell stored in the ΔT ₁ ⁿ detection database 9b-1 is within a predetermined range (step S06). In this determination, a cell in which ΔT ₁ ⁿ is in an appropriate range is determined as a normal cell, and a cell in which ΔT ₁ ⁿ is not in a predetermined range is determined as a cell whose air inflow amount is not in an appropriate range, that is, an abnormal cell. Then, classification is performed (step S21).

Next, the detection processing unit 9a of the first voltage difference [Delta] V ₂ ⁿ stored in the [Delta] V ₂ ⁿ detection database 9b-3, with the first voltage difference [Delta] V ₂ ⁿ of only normal cells, methanol cross Over is estimated (step S22). Here, when a variation occurs between the first voltage differences ΔV ₂ ⁿ of normal cells, the value of only a specific cell among them is measured as a representative value, and an average of a plurality of first voltage differences ΔV ₂ ⁿ Or the dispersion of the first voltage difference ΔV ₂ ⁿ of the normal cell is measured, and the value of the first voltage difference ΔV ₂ ⁿ of the cell whose dispersion is within a predetermined range can be used.

In ^order to estimate the methanol crossover value from the obtained first voltage difference ΔV ₂ ^{n, the} crossover conversion database 9b-4 stored in the database 9b is used. Information for converting the first voltage difference ΔV ₂ ⁿ into a methanol crossover value is stored in advance in the crossover conversion database 9b-4. Specifically, a positive correlation is given between ΔV ₂ ⁿ and the methanol crossover value, and when ΔV ₂ ⁿ is larger than a predetermined value, the methanol crossover value is larger than the predetermined value. On the other hand, if ΔV ₂ ⁿ is smaller than a predetermined value, it is determined that the methanol crossover value is smaller than a predetermined value. After estimating the methanol crossover value, the detection processing unit 9a gives an instruction to control the fuel supply amount based on this value (step S23). Here, for the relationship between the estimated methanol crossover value and the fuel supply amount, the crossover supply amount control database 9b-5 stored in advance in the database 9b is used. Based on the crossover supply amount control database 9b-5, the control unit 9 sends a supply amount control signal to the fuel supply unit 4, and the fuel supply unit 4 controls the fuel supply amount (step S24). Specifically, a negative correlation is given between the methanol crossover value and the fuel supply amount, and when the methanol crossover value is larger than a predetermined value, the fuel supply amount is set to be greater than the predetermined value. Decrease. Conversely, if the methanol crossover value is smaller than a predetermined value, the fuel supply amount is increased from a predetermined value.

That is, when the voltage difference ΔV ₂ ⁿ is larger than a predetermined value, the fuel supply amount is decreased from a predetermined value. When the voltage difference ΔV ₂ ⁿ is smaller than a predetermined value, the fuel supply amount is increased from a predetermined value.

The second embodiment includes a power generation unit having a plurality of stacked cells, a fuel supply unit capable of supplying fuel to the cells, the fuel supply amount being adjustable, and at least one cell among the plurality of cells. A voltage monitoring unit that monitors the output voltage of the power generation unit, an adjustment unit that adjusts the load current extracted from the power generation unit, and the output voltage that is minimum since the load current is adjusted from the first value to the second value. A time measuring unit that measures a time until a value is reached, a voltage difference measuring unit that measures a voltage difference between the minimum value and a maximum value after the output voltage has reached a minimum value, the time and the voltage There is provided a fuel cell system including a control unit that controls the fuel supply amount according to a difference.

In addition, the second embodiment includes a power generation unit having a plurality of stacked cells, a fuel supply unit that supplies methanol fuel to the cells, the fuel supply amount being adjustable, and at least one of the plurality of cells. A voltage monitoring unit that monitors an output voltage of one cell; an adjustment unit that adjusts a load current extracted from the power generation unit; and the output from the time when the load current is adjusted from a first value to a second value. A time measurement unit that measures a time until the voltage reaches a minimum value, a voltage difference measurement unit that measures a voltage difference between the minimum value and a maximum value after the output voltage reaches a minimum value, and the time A fuel cell system comprising: a calculation unit that calculates a methanol crossover value using the voltage difference between cells in a range within a predetermined range.

That is, in the method of FIG. 7 described above, when the methanol crossover is estimated from the first voltage difference ΔV ₂ ⁿ of each cell at the time of load change, the output voltage of the cell is from the start of load change to the minimum value. Time ΔT ₁ ⁿ is detected simultaneously. Then, it is determined from the value of ΔT ₁ ⁿ whether or not the air inflow amount flowing into each cell 51 is in an appropriate range, and methanol crossover is estimated using the first voltage difference ΔV ₂ ⁿ of only normal cells. Like to do. In this way, since it is determined in advance whether or not the air inflow amount to each cell 51 is in an appropriate range, it is possible to eliminate the influence of fluctuations in the air inflow amount that causes a large methanol crossover estimation error. Is possible. Therefore, the estimation accuracy of methanol crossover can be improved and the fuel utilization efficiency can be increased.

(Third embodiment)
In the second embodiment, ΔT ₁ ⁿ at the time of load change is measured, a cell 51 whose value is not within a predetermined range is determined as an abnormal cell, and the first voltage difference ΔV ₂ ⁿ of only normal cells is used. A method for estimating methanol crossover was performed. However, in this method, when the number of abnormal cells increases from that of normal cells, the power generation efficiency of the abnormal cells decreases, and at the same time, the number of cells that can be used as normal cells decreases. Usage efficiency may be reduced. Therefore, it is possible to incorporate a process for recovering an abnormal cell in the course of operation for controlling methanol crossover.

FIG. 8 shows a processing procedure of the system in the third embodiment. The control operation of the control unit 9 will be described with reference to FIG. FIG. 8 shows the processing after step S21 in the flowchart of FIG.

Step S21 corresponds to an abnormal cell detection step in the flowchart of FIG. Here, cells [Delta] T ₁ ⁿ as described in the second embodiment is determined not in the predetermined range is determined to be abnormal cells, cell [Delta] T ₁ ⁿ is judged to be within a predetermined range It is determined as a normal cell (step S210). If it is determined that the cell is normal, it is used for methanol crossover control. (Step S22).

On the other hand, if it is determined in step 21 that the cell is abnormal, it is determined whether ΔT ₁ ⁿ is larger or smaller than a predetermined value (step S211). When ΔT ₁ ⁿ is larger than the predetermined value, the control unit 9 instructs the air supply unit 6 to increase the air supply amount in step S212 (step S212). Thereby, the air supply part 6 is controlled and the air flow rate supplied to each cell 51 in the power generation part 5 is increased. By increasing the flow rate of air supplied to the cell 51, water accumulated in the cathode electrode is removed, and the power generation efficiency can be recovered.

On the other hand, if ΔT ₁ ⁿ is smaller than the predetermined value in the determination in step S211, the control unit 9 instructs the fuel supply unit 4 to increase the fuel supply amount (step S214). Thereby, the fuel supply part 4 is controlled and the fuel supply amount supplied to each cell 51 in the power generation part 5 is increased. By increasing the amount of fuel supplied to the cell 51, carbon dioxide accumulated in the anode electrode is removed, and the power generation efficiency can be recovered. Here, the increase amount of the air supply amount and the increase amount of the fuel supply in steps S211 and S213 are determined in advance in the database of the control unit 9b, and in addition to performing the above steps only on abnormal cells, the output of normal cells It is possible to apply to all the cells within a range that does not give a predetermined output reduction to the reduction.

As described above, in the system according to the embodiment of the present invention, normal cells are used for crossover estimation, while malfunctions can be recovered by applying appropriate processing to abnormal cells. Both efficiency and power generation efficiency can be increased.

In the third embodiment, the fuel circulation unit supplies the fuel in the fuel tank 3 to the mixing tank that stores the diluted fuel, and mixes it with the fuel remaining in the power generation in the power generation unit 5. Applicable. In this case, in order to increase the fuel supply amount supplied to the power generation unit 5 in step S214 in FIG. 8, the fuel circulation unit can be operated to increase the fuel circulation amount.

(Fourth embodiment)
The fourth embodiment of the present invention temporarily supplies power to a specific cell among the cells stacked in the power generation unit, estimates a methanol crossover by causing a load fluctuation only in the specific cell, and generates the power generation unit. The amount of fuel supplied to the is controlled.

FIG. 9 shows a configuration example of the fuel cell system 101 according to the fourth embodiment of the present invention. The fuel cell system 101 includes a power generation unit 5 having a cell stack structure 50 as shown in FIG. 10 and a fuel tank that stores liquid fuel such as high-concentration methanol or a mixed solution of methanol fuel and a small amount of water (methanol aqueous solution). 3, the auxiliary devices 2 that support the power generation in the power generation unit 5, and the electric power generated by the power generation unit 5 are controlled by the external power source (for example, a lithium ion battery) and the power extracted from the power generation unit 5. A power adjustment unit 10.

The auxiliary devices 2 include a fuel supply unit 4 that supplies fuel from the fuel tank 3 to the power generation unit 5, an air supply unit 6 that supplies air to the power generation unit 5, and a load that adjusts the load current extracted from the power generation unit 5. The adjustment unit 7, the cell voltage monitoring unit 8 that monitors the output voltage of each cell of the cell stack structure 50, the external power supply unit 13, and the control unit 9 for controlling each unit in the auxiliary devices 2 are provided. .

The control unit 9 includes a detection processing unit 9a that detects the state of each unit of the auxiliary devices 2, and a database 9b in which control information for controlling each unit according to the detected information is stored in advance. The control unit 9 detects necessary information from each unit of the power generation unit 5 and the auxiliary devices 2 and processes or calculates the detected information. Further, the control unit 9 gives control signals to the fuel supply unit 4, the power generation unit 5, the load adjustment unit 7, the external power supply unit 13, and the air supply unit 6 according to the result of this processing or calculation. As will be described later, the database 9b includes various databases described in advance on how to control each part of the auxiliary equipment 2 based on the values measured from the cells.

The power generation unit 5 is connected to the load power 11 through the load adjustment unit 7 and the power adjustment unit 10. The load power 11 corresponds to, for example, an electronic device driven by power generated by the fuel cell system 101. The power adjustment unit 10 supplies the power generated by the power generation unit 5 to the load power 11. The power is adjusted by adjusting the load current by the load adjusting unit 7. When the power generated by the power generation unit 5 is insufficient with respect to the power required for the load power 11, the power adjustment unit 10 is not shown in the figure, but from an external power source (for example, a secondary battery or a capacitor). Make up for the power shortage. The power adjustment unit 10 includes a switching circuit that turns on or off the supply of power generated by the power generation unit 5 to the load power 11. The power adjustment unit 10 is configured to be connected to the load power 11 in the on state to be in a closed circuit state, disconnected from the load power 11 in the off state, and to be in an open circuit state on the output side.

In the system shown in FIG. 9, the fuel in the fuel tank 3 is directly supplied to the power generation unit 5. However, the present invention is not limited to this, and the fuel in the fuel tank 3 is diluted with fuel. You may make it the system which mixes with the fuel remaining in the electric power generation in the power generation part 5 by supplying in the mixing tank to store. Moreover, when a fan is used for the air supply part 6, the fluid piping L3 can be used as an air introduction path | route. In the case of the breathing method, the air supply unit 6 is not necessary.

The power generation unit 5 and the auxiliary devices 2 are connected by a signal and current wiring system. The control unit 9 is connected to the fuel supply unit 4 via the signal line E1. The power generation unit 5 and the control unit 9 are connected by a signal line E2. The load adjustment unit 7 and the control unit 9 are connected by a signal line E3. The cell voltage monitoring unit 8 and the control unit 9 are connected by a signal line E4. The air supply unit 6 and the control unit 9 are connected by a signal line E5. The power generation unit 5 and the load adjustment unit 7 are connected by a current wiring line E61, and the load adjustment unit 7 and the power adjustment unit 10 are connected by a current wiring line E62. Furthermore, the external power supply unit 13 is connected to the power generation unit 5 through a current supply line E7, and is connected to the control unit 9 through a signal line E8.

The load adjustment unit 7 applies a load to the power generation unit 5 through the signal line E3. The value of the load current detected by the load adjustment unit 7 is sent to the control unit 9 via the signal line E3 as load current information. The load control signal set by the control unit 9 is given from the control unit 9 to the load adjustment unit 7 via the signal line E3. Therefore, the load adjustment unit 7 connects a load corresponding to the set load determined according to the load control signal to the power generation unit 5, and the load current flowing through the set load is detected and sent to the control unit 9 as load current information. .
Note that the power adjustment unit 10 can be omitted by providing the load adjustment unit 7 with the role of the power adjustment unit 10. In this case, the load power 11 is connected to the load adjustment unit 7.

The cell voltage monitoring unit 8 includes a cell voltage detection circuit (not shown) that detects a voltage generated in at least one specific cell 51 determined in advance, and the cell stack in the power generation unit 5 via the signal line E4. Connected to the specific cell 51 of the structure 50. Here, as the specific cell 51, it is preferable to select a cell having an average output and temperature among the cells included in the cell stacked structure 50. Here, the average cell means a cell that is not easily influenced by external environmental factors. For example, a cell in the central region in the cell stacking direction, or a cell whose temperature distribution is measured and whose temperature is closest to the average can be adopted as the average cell. By adopting such an average cell as the specific cell 51, it is possible to stably obtain the cell characteristics even when the external environment changes. The voltage generated in the specific cell 51 is measured by the cell voltage detection circuit, and the measured cell voltage value is sent to the control unit 9 as voltage information. Here, as the specific cell 51, in addition to selecting one of the cells included in the cell stack structure 50, a plurality of cells are selected from the cell stack structure 50, and the voltage average is measured to obtain voltage information. May be sent to the control unit 9.

Then, the external power supply unit 13 is connected to the specific cell 51 to which the cell voltage monitoring unit 8 is connected via the current supply line E7 in an electrically parallel manner. The external power supply unit 13 gives a predetermined current to the specific cell 51.

The power generation unit 5 includes a cell stack structure 50 as shown in FIGS. 10 (a) and 10 (b). As shown in FIG. 10A, the cell stack structure 50 includes a plurality of cells stacked between the anode current collector plate 12 and the cathode current collector plate 14, and each cell has the anode current collector plate 12 and the cathode. The current collector 14 is electrically connected in series. The cells stacked between the anode current collector plate 12 and the cathode current collector plate 14 are disposed between a pair of clamping

plates

18A and 18B, and are clamped and fixed by

fixtures

19A and 19B between the clamping

plates

18A and 18B. ing. The anode current collecting plate 12 and the cathode current collecting plate 14 are connected to the load adjusting unit 7, respectively, and the current generated in the cell stack structure 50 is collected by the cathode current collecting plate 14 and supplied to the load adjusting unit 7.

FIG. 10B shows the configuration of the specific cell 51. The cells other than the specific cell 51 include a membrane electrode assembly (MEA) 20, an anode flow channel plate 22, a cathode flow channel plate 24, and a gasket 26.

The anode channel plate 22 is provided on one side of the MEA 20, and the cathode channel plate 24 is provided on the other side. The MEA 20 is sandwiched between the anode flow path plate 22 and the cathode flow path plate 24 and formed in a structure sealed with a gasket 26 connected to the anode flow path plate 22 and the cathode flow path plate 24. The anode flow path plate 22 and the cathode flow path plate 24 are insulated by the gasket 26, and the leakage of fuel and air from the MEA 20 to the outside is prevented by the gasket 26. The MEA 20 has an anode electrode formed on one side of the electrolyte membrane and a cathode electrode formed on the other side of the electrolyte membrane.

The specific cell 51 is provided with

output terminals

22A and 24A on the anode flow path plate 22 and the cathode flow path plate 24 in order to monitor the voltage of the specific cell 51 from the outside. The

output terminals

22A and 24A are connected to the voltage detection circuit of the cell voltage monitoring unit 8 via the cell voltage signal line E4, and the voltage of the specific cell 51 is monitored (monitored) by the cell voltage monitoring unit 8. From the cell voltage monitoring unit 8, voltage information indicating a voltage value corresponding to the voltage generated in the specific cell 51 is supplied to the detection processing unit 9a of the control unit 9 via the signal line E4.

Furthermore, the specific cell 51 is provided with

input terminals

22B and 24B on the anode flow path plate 22 and the cathode flow path plate 24, respectively. The

input terminals

22B and 24B are electrically connected in parallel to the current circuit of the external power supply unit 13 through the current supply line E7. The external power supply unit 13 receives a signal for supplying power to the specific cell 51 from the control unit 9 via the signal line E8.

The anode flow path plate 22 faces the anode electrode side of the MEA 20 and supplies methanol and a methanol aqueous solution. The cathode flow path plate 24 faces the cathode side of the MEA 20 and supplies air. Both the anode flow path plate 22 and the cathode flow path plate 24 can take any shape as long as the above purpose is achieved.

Next, the operation of the fuel cell system 101 shown in FIG. 9 will be described.
When starting power generation, the fuel supply unit 4 supplies a methanol aqueous solution (fuel) having a predetermined concentration from the fuel tank 3 to the anode flow path plate 22 via the flow paths L1 and L2 under the control of the control section 9. Supply. The air supply unit 6 supplies air to the cathode flow path plate 24 through the flow path L3 under the control of the control unit 9.

During the above power generation, there is a problem that methanol flows to the cathode electrode through the solid polymer membrane (methanol crossover). Since an increase in the methanol crossover value or an extreme decrease in the methanol causes a decrease in power generation efficiency and fuel utilization efficiency, processing for controlling the methanol crossover value within a predetermined range is performed.

Referring to FIG. 11, the flow of estimating the methanol crossover and controlling the amount of methanol supplied to the power generation unit 5 so that the value falls within a predetermined range will be described.

In the graph shown in FIG. 11, in the period before time T = T ₀ , the load adjustment unit 7 selects the first load, the load current I = I 0 is extracted from the cell stack structure 50, and power generation is performed. Yes. During this period, power (current) is not supplied from the external power supply unit 13 to the specific cell 51.

Next, at a time point T = T ₀ , power that is a predetermined current (I2) is supplied to the specific cell 51 from the external power supply unit 13 that is electrically connected to the specific cell 51 in parallel. Therefore, the cell current I taken out from the specific cell 51 decreases when the current taken out from the entire power generation unit 5 by the load adjusting unit 7 is constant (I0), and the cell current taken out from the specific cell 51 is I1 = I0−I2. It becomes.

Particular cell 51 is operated at a cell current I1 to the time T = T _1, at time T = T _1, to stop the supply of electric power (current) from an external power supply unit 13. Therefore, at time T = T ₁ , the current I extracted from the specific cell 51 increases from I1 to I0.

With this load current I1 to the load change on I0, the time T = T ₂ immediately after switching to the second load, the cell voltage V, the minimum voltage value V = V ₂ (minimum value of the voltage), and Thereafter, at time T = T ₃ , the maximum voltage value (maximum voltage value) is taken at V = V ₃ and then converges to a constant voltage.

Here, a voltage difference between the minimum voltage value V ₂ and the maximum voltage value V ₃ is defined as a first voltage difference ΔV ₃ (ΔV ₃ = V ₃ −V ₂ ). Further, the voltage difference between the minimum voltage value V ₂ and the steady voltage V ₄ after elapse of a certain time (for example, T = T ₄ ) is defined as a _second voltage difference ΔV ₄ (ΔV ₄ = V ₄ −V ₂ ). To do. The methanol crossover of the specific cell 51 is estimated using the first voltage difference ΔV ₃ and the second voltage difference ΔV ₄ .

Hereinafter, a cell voltage of a particular cell 51 in the cell voltage monitor unit 8 is monitored, first between the maximum voltage value V ₃ of the output応値(response value of the output voltage) appearing after the minimum voltage value V ₂ and the minimum voltage 1 of the voltage difference [Delta] V ₃ is determined by the detection processing section 9a, the estimation of the methanol crossover on the basis of the first voltage difference [Delta] V _3, the basic principle of the process for controlling explaining. Note that the following methanol crossover estimation and control method is the same based on the second voltage difference ΔV ₄ .

FIG. 12 shows a processing procedure of the system in the fourth embodiment. The control operation of the control unit 9 will be described with reference to FIG.

When the control operation is started in the control unit 9 (step S101), the detection processing unit 9a instructs the external power supply unit 13 to perform load fluctuation processing for supplying predetermined power (current I2) (step S102). . In accordance with this instruction, the external power supply unit 13 supplies a current (I2) to the specific cell 51 (step S103). Then, after a certain time has elapsed, the supply of power from the external power supply unit 13 is stopped. At the same time, the cell voltage monitoring unit 8 measures the voltage value of the specific cell 51 with the time by the voltage detection circuit in the cell voltage monitoring unit 8 (step S104). As a result, voltage information that varies with time is input from the cell voltage monitoring unit 8 to the specific cell 51 to the detection processing unit 9a.

Detection processing unit 9a detects the maximum voltage value V ₃ appearing thereafter from the voltage information that is input to the minimum voltage value V _2, the difference between the minimum voltage value V ₂ and the maximum voltage value V _3, which is the detected detecting a first voltage difference [Delta] V ₃ (step S105).

In order to estimate the methanol crossover value from the obtained first voltage difference ΔV _{3, the} crossover conversion database 9b-11 stored in the database 9b is used (step S106). Crossover terms database 9b-11 is information for converting a first voltage difference [Delta] V ₃ in methanol crossover values are stored in advance. After estimating the methanol crossover value, the detection processing unit 9a gives an instruction to control the fuel supply amount based on this value. Here, as the relationship between the estimated methanol crossover value and the fuel supply amount, the crossover supply amount control database 9b-12 stored in advance in the database 9b is used (step S107). Based on the crossover supply amount control database 9b-12, the control unit 9 sends a supply amount control signal to the fuel supply unit 4, and the fuel supply unit 4 controls the fuel supply amount (step S108).

As described above, in the fourth embodiment, the load fluctuation is caused only to the specific cell 51 due to the power supply from the external power supply unit 13, and the methanol crossover is estimated. Therefore, compared with the method of changing the load of the entire power generation unit 5, it is not necessary to reduce the power generation amount of the entire power generation unit 5, and the power generation efficiency can be increased over a long period of time. In addition, the unsteady temperature fluctuation of the power generation unit 5 due to the load fluctuation causes an error in the process of estimating the methanol crossover and controlling the fuel supply amount. Does not change, that is, the calorific value does not change. As a result, temperature fluctuations of the power generation unit 5 are suppressed, and the above influence can be suppressed.

(Fifth embodiment)
In the fourth embodiment, the external power supply unit 13 is electrically connected in parallel only to the specific cell 51 of the cells constituting the power generation unit 5, and the power supplied from the external power supply unit 13 to the specific cell 51 is supplied. It was characterized by estimating methanol crossover by controlling. Here, the external power supply unit 13 can be used in combination with other auxiliary devices as long as it serves the purpose of supplying constant power to the specific cell 51 for a predetermined time.

FIG. 13 shows a configuration example of the fuel cell system 102 according to the fifth embodiment of the present invention. The fuel cell system 102 has a configuration in which the external power supply unit 13 is removed from the fuel cell system 1 shown in FIG. The specific cell 51 included in the power adjustment unit 10 and the power generation unit 5 is electrically connected through the line E70. Further, the power adjustment unit 10 and the control unit 9 are connected through a line E80. Further, the operation of the detection processing unit 9a in the control unit 9 is different. Since other configurations are the same as those in FIG. 9, the same components as those in FIG. 9 are denoted by the same reference numerals and detailed description thereof is omitted.

When the power generated by the power generation unit 5 is insufficient with respect to the power required for the load power 11, the power adjustment unit 10 is not shown in the figure, but from an external power source (for example, a lithium ion battery or a capacitor). Since the power adjustment unit 10 has the function of the external power supply unit 13 illustrated in FIG. 9 because the power adjustment unit 10 has an adjustment function that compensates for the shortage of power, the system configuration can be simplified. The operation method of the fuel cell system 102 of FIG. 13 is the same as that of the fourth embodiment if the function of the external power supply unit 13 of FIG. To do.

In the fourth and fifth embodiments, the fuel in the fuel tank 3 is supplied by the fuel circulation unit into the mixing tank that stores the diluted fuel, and mixed with the fuel remaining in the power generation in the power generation unit 5. It can also be applied to the method.

Example 1
In Example 1, an attempt was made to obtain the voltage difference V ₃ between the minimum voltage value and the output response value (maximum voltage value) as an evaluation value by using the method of the fourth embodiment.

The power generation section 5 used 20 cells stacked in series. Among the cells included in the power generation unit 5, the tenth set of cells counted from the anode electrode side is set as a predetermined set of specific cells 51, and only the specific cell 51 includes the voltage monitoring unit 8 and the external power supply unit 13. Is connected to enable monitoring of the cell voltage of the specific cell 51 and power supply to the specific cell 51. The remaining 19 cells are not connected to the voltage monitoring unit 8 and the external power supply unit 13. The air supply amount to the power generation unit 5 was performed by an air pump, and the air supply flow rate was fixed during the measurement. The fuel supply to the power generation unit 5 was performed by a fuel pump and fixed at a predetermined fuel concentration and fuel flow rate. Control was performed so that the temperature of the power generation unit 5 was kept constant by a separate temperature adjusting means.

FIG. 14A is a graph showing the load current and the current supplied from the external power supply unit 13 to the specific cell 51, and FIG. 14B is a graph showing the output voltage of the power generation unit 5 and the cell voltage of the specific cell 1. It is.

Under the above operating conditions, as shown in FIG. 14A, the load current taken out from the power generation unit 5 is fixed at I0 = 1.07 A, and the specific cell 51 to which the external power supply unit 13 is connected has an external power supply unit. 13, a current fixed at I2 = 0.95 A at T = T ₀ is supplied only for 35 seconds, current supply from the external power supply unit 13 is terminated at T = T ₁ after 35 seconds, and the load changes Drove driving. Then, it was determined and the minimum voltage observed at T = T _2, the voltage difference V ₃ between the maximum voltage observed at T = T _3.

(Comparative Example 1)
In order to compare with the first embodiment, the first comparative example varies the load of the entire power generation unit 5. FIG. 15A is a graph showing the load current, and FIG. 15B is a graph showing the output voltage of the power generation unit 5 and the cell voltage of each cell.

As shown in FIG. 15A, the load current extracted from the power generation unit 5 is switched from I0 = 1.07 A to I0 = 0.12 A at T = T ₀ , held for 35 seconds, and then again at T = T ₁ I0 = 1 The operation which gives load change to 0.07A was performed. Then, the difference between the minimum voltage observed at T = T ₂ and the maximum voltage observed at T = T ₃ was obtained. The results are shown in FIGS. 15A and 15B.

Figure 14A, the 14B, for driving the load current I = I0 taken out from power generating unit 5, the 19 pieces of cells other than the specific cell 51 enables power generation by the I = I0, T = from _{_T 0 T} = _T ₁ It became possible to maintain the power generation output of the power generation unit 5 in the period up to. On the other hand, in FIGS. 15A and 15B, the load current is reduced to 0.12 A during the period from T = T ₀ to T = T _1, so that the power that can be taken out from the power generation unit 5 has decreased. .

The voltage difference _{V 3} obtained in the method of Example 1 was 0.043V, the voltage difference _{V 3} obtained in Comparative Example 1 approach is also 0.043V, there was no difference in the voltage difference _{V 3} in both. Therefore, according to the method of the first embodiment, it is possible to measure a voltage difference without intermittently reducing the power generation output of the power generation unit 5, and a stable power generation with a high output over a long time can be achieved. I was able to confirm that it would be possible.

(Sixth embodiment)
In the sixth embodiment of the present invention, the external power supply unit 13 is connected to a specific cell such as an end of the cells stacked on the power generation unit 5 and the external power supply unit 13 is operated according to the temperature of the specific cell. It is what you do.

FIG. 16 shows a configuration example of the fuel cell system 103 according to the sixth embodiment of the present invention. The fuel cell system 103 includes a cell temperature monitoring unit 81 instead of the cell voltage monitoring unit 8 of the fuel cell system 101 shown in FIG. Further, the operation of the detection processing unit 9a in the control unit 9 and the data items stored in the database 9b are different. Since other configurations are the same as those in FIG. 9, the same components are denoted by the same reference numerals, and detailed description thereof is omitted.

The cell temperature monitoring unit 81 includes a cell temperature detection circuit (not shown) that detects the temperature of at least one predetermined cell among the cells included in the cell stack structure 50 in the power generation unit 5, and the signal line E40. Connected to the cell via The cell temperature is measured by a cell temperature detection circuit and sent to the control unit 9 as cell temperature information. Here, the cell to which the cell temperature monitoring unit 81 is connected is the cell at the end where the temperature is the lowest in the cell stack structure 50. Hereinafter, the configuration of the power generation unit 5 in which two cells at both ends of the cell stack structure 50 are specified cells 511 and the cell temperature monitoring unit 81 is connected will be described.

The power generation unit 5 includes a cell stack structure 50 as shown in FIGS. 17A, 17B and 17C. As shown in FIG. 17A, the cell stack structure 50 includes a specific cell 511 stacked between the anode current collector plate 12 and the cathode current collector plate 14 and a specific cell arranged inside the specific cell 511. Cell 510. The specific cell 511 and the cell 510 are electrically connected in series to the anode current collector plate 12 and the cathode current collector plate 14. The specific cell 511 and the cell 510 are disposed between the pair of

fastening plates

18A and 18B, and are fastened and fixed by the

fixtures

19A and 19B between the

fastening plates

18A and 18B. The anode current collecting plate 12 and the cathode current collecting plate 14 are connected to the load adjusting unit 7, respectively, and the current generated in the cell stack structure 50 is collected by the cathode current collecting plate 14 and supplied to the load adjusting unit 7.

Further, the specific cell 511 and the cell 510 include a membrane electrode assembly (MEA) 20 as shown in FIGS. 17B and 17C. An anode flow path plate 22 is provided on one side of the MEA 20, and a cathode flow path plate 24 is provided on the other side. The MEA 20 is sandwiched between the anode flow path plate 22 and the cathode flow path plate 24 and formed in a structure sealed with a gasket 26 connected to the anode flow path plate 22 and the cathode flow path plate 24. The anode flow path plate 22 and the cathode flow path plate 24 are insulated by the gasket 26, and the leakage of fuel and air from the MEA 20 to the outside is prevented by the gasket 26. The MEA 20 has an anode electrode formed on one side of the electrolyte membrane and a cathode electrode formed on the other side of the electrolyte membrane.

The specific cell 511 is provided with a cell temperature detection sensor 22C or 24C on the anode flow path plate 22 or the cathode flow path plate 24 in order to monitor the cell temperature. Information of the temperature detection sensor is sent to the temperature detection circuit of the cell temperature monitoring unit 81 via the signal line E40. From the cell temperature monitoring unit 81, the temperature information of the specific cell 511 is supplied to the detection processing unit 9a of the control unit 9 via the signal line E40. For example, a thermocouple can be used as the temperature detection sensor.

Furthermore, in the specific cell 511,

electrical input terminals

22B and 24B are provided on the anode channel plate 22 and the cathode channel plate 24, respectively. The

input terminals

22B and 24B are electrically connected in parallel to the current circuit of the external power supply unit 13 through the current supply line E7.

Next, the operation of the fuel cell system 103 shown in FIG. 16 will be described.
When starting power generation, the fuel supply unit 4 supplies a methanol aqueous solution (fuel) having a predetermined concentration from the fuel tank 3 to the anode flow path plate 22 via the flow paths L1 and L2 under the control of the control section 9. Supply. The air supply unit 6 supplies air to the cathode flow path plate 24 through the flow path L3 under the control of the control unit 9.

During the above power generation, the power generation unit is operated at a predetermined temperature in order to keep the power generation efficiency and power generation amount of the power generation unit at a predetermined value. At this time, a temperature distribution is generated between the power generation cells of the power generation unit due to the influence of the outside air temperature and the like. In particular, the temperature of the specific cell 511 at the end of the power generation unit 5 that is most susceptible to the influence of outside air is the lowest. In this case, there is a problem that the fuel diffusibility at the anode electrode of the specific cell 511 is lowered, and the same load as the central cell 510 having a higher temperature than the specific cell 511 cannot be taken out. In this case, if the power generation unit 5 is generated with a load that can be taken out at the temperature of the specific cell 511 at the end, the other cells 510 are also reduced in accordance with the load of the specific cell 511 to generate power. The power generation amount of the entire power generation unit 5 is reduced. Moreover, in cells other than the specific cell 511, there exists a problem that methanol crossover increases by load reduction and power generation efficiency falls.

Therefore, in the sixth embodiment, the cell temperature monitoring unit 8 and the external power supply unit 13 are connected to the specific cell 511 at the end in contact with the anode current collector 18A and the cathode current collector 18B to solve the above problem. The method to do is explained.

With reference to FIG. 18, an operation method of the fuel cell system 103 according to the sixth embodiment will be described.
FIG. 18 shows the change over time of the temperature of the specific cell 511 when the outside air temperature is changed within a certain range. When the outside air temperature decreases, the temperature of the specific cell 511 decreases accordingly.

Here, when the control unit 9 determines that the temperature of the specific cell 511 is lower than the predetermined lower limit temperature T _lim during the power generation time x = x ₁ based on the temperature information supplied from the cell temperature monitoring unit 81. The external power supply unit 13 is electrically connected in parallel to the specific cell 511 via the current supply line E7. When the external power supply unit 13 is connected to the specific cell 511 via the current supply line E7, the external power supply unit 13 supplies constant power (current I2) to the specific cell 511. As a result, even if the load current of the power generation unit 5 is constant I = I0 during the power generation time, the load current I1 extracted from the specific cell 511 is constantly reduced as I1 = I0−I2. Thereafter, when the control unit 9 determines that the specific cell 511 temperature has become higher than the lower limit temperature T _lim during the power generation time x = x ₂ , the supply of power from the external power supply unit 13 is stopped. Thereby, the load current I1 taken out from the specific cell 511 becomes the same load I1 = I0 as the power generation unit load I0.

FIG. 19 shows a processing procedure of the system in the sixth embodiment. The control operation of the control unit 9 will be described with reference to FIG.

When the control operation is started in the control unit 9 (step S111), the detection processing unit 9a measures the temperature of the specific cell 511 (step S112). In accordance with this instruction, the cell temperature monitoring unit 81 detects the temperature of the specific cell 511 (step S113). Then, based on the cell temperature database 9b-111 stored in advance in the database 9b, it is determined whether or not the measured temperature of the specific cell 511 is within a predetermined range (step S114). In the cell temperature database 9b-111, information indicating a temperature range (at least one of an upper limit value and a lower limit value) in which the cell can normally generate power is stored in advance. When the temperature of the specific cell 511 is within the predetermined range, the detection processing unit 9a proceeds to step S112, and repeatedly measures the temperature of the specific cell 511 (step S114: YES).

On the other hand, when the measured temperature of the specific cell 511 is not within the predetermined range (step S114: NO), the detection processing unit 9a uses the external power supply amount database 9b-112 stored in advance in the database 9b. An instruction to supply external power to the power supply unit 13 is given (step S115). Information for converting the measured cell temperature into the supply amount of electric power (current) from the external power supply unit 13 is stored in advance in the external power supply database 9b-112. Thereby, power is supplied to the specific cell 511 from the external power supply unit 13 electrically connected to the specific cell 511 in parallel (step S116).

As described above, in the sixth embodiment, during steady power generation, the temperature of the specific cell 511 is lowered from a predetermined temperature due to external environmental factors such as outside air temperature, and the load current that can be extracted from the specific cell 511 is reduced. However, the load current of the entire power generation unit 5 can be kept constant by supplying power (current) from the external power supply unit 13 to the specific cell 511. Therefore, in the fuel cell system, even when there is temperature variation between cells included in the power generation unit, it is possible to improve the power generation efficiency and the power generation amount.

Further, the sixth embodiment can be applied not only to steady power generation, which generates a predetermined amount of power, but also to startup. At the time of start-up, it is preferable to shorten the time until a predetermined power generation amount can be obtained by shortening the time required for the cell temperature to reach a predetermined temperature. Applying the method of the sixth embodiment, when the fuel cell system is started up, if the specific cell 511 cannot be taken out because of the low temperature of the specific cell 511, external power is supplied only to the specific cell 511. The unit 13 is electrically connected in parallel, and the load current taken out from the specific cell 511 is reduced. By doing in this way, cells other than the specific cell 511 can be operated with a predetermined load, and the starting speed from a low temperature can be increased.

(Seventh embodiment)
In the sixth embodiment, the cell temperature monitoring unit 81 and the external power supply unit 13 are connected to the specific cell 511 having the lowest temperature, and the external power supply unit 13 is operated according to the cell temperature. In the embodiment, the external power supply unit 13 is connected to a cell having a low output voltage in the power generation unit 5, and the external power supply unit 13 is operated according to the cell output voltage.

The configuration of the fuel cell system according to the seventh embodiment is the same as that of the fuel cell system 101 shown in FIG. 9, and will be described with reference to FIG. However, in the seventh embodiment, the configuration of the power generation unit 5, the operation of the detection processing unit 9a in the control unit 9, and the data items stored in the database 9b are different.

The power generation unit 5 includes a cell stack structure 50 as shown in FIGS. 20A, 20B and 20C. As shown in FIG. 20A, the cell stack structure 50 includes a specific cell 521 that is stacked between the anode current collector plate 12 and the cathode current collector plate 14 and connected to the cell voltage monitor unit 8, and a cell voltage monitor unit. Cell 520 other than the specific cell to which 8 is not connected. The specific cell 521 and the cell 520 are electrically connected to the anode current collector plate 12 and the cathode current collector plate 14 in series. The ratio between the specific cell 521 and the cell 520 can be arbitrarily set as long as the specific cell 521 has one or more cells. FIG. 20A shows an example in which specific cells 521 and cells 520 are stacked at an interval of one cell. The specific cell 521 and the cell 520 stacked between the anode current collector plate 12 and the cathode current collector plate 14 are disposed between the pair of clamping

plates

18A and 18B, and a fixture is provided between the clamping

plates

18A and 18B. It is fastened and fixed by 19A and 19B. The anode current collecting plate 12 and the cathode current collecting plate 14 are connected to the load adjusting unit 7, respectively, and the current generated in the cell stack structure 50 is collected by the cathode current collecting plate 14 and supplied to the load adjusting unit 7.

The specific cell 521 and the cell 520 include a membrane electrode assembly (MEA) 20 as shown in FIGS. 20B and 20C. An anode flow path plate 22 is provided on one side of the MEA 20, and a cathode flow path plate 24 is provided on the other side. The MEA 20 is sandwiched between the anode flow path plate 22 and the cathode flow path plate 24 and formed in a structure sealed with a gasket 26 connected to the anode flow path plate 22 and the cathode flow path plate 24. The anode flow path plate 22 and the cathode flow path plate 24 are insulated by the gasket 26, and the leakage of fuel and air from the MEA 20 to the outside is prevented by the gasket 26.

The specific cell 521 is provided with

electric wirings

22D and 24D for cell voltage detection on the anode flow path plate 22 and the cathode flow path plate 24 in order to monitor the cell voltage. The

electric wirings

22D and 24D for cell voltage detection are connected to the voltage detection circuit of the cell voltage monitoring unit 8 through the signal line E4. From the cell voltage monitoring unit 8, voltage information representing the voltage value of the specific cell 521 detected by the voltage detection circuit is supplied to the detection processing unit 9a of the control unit 9 via the signal line E4.

Furthermore, in the specific cell 521 to which the voltage detection circuit of the cell voltage monitoring unit 8 is connected,

input terminals

22B and 24B are provided on the anode flow path plate 22 and the cathode flow path plate 24, respectively. The

input terminals

FIG. 21 shows the processing procedure of the system in the seventh embodiment. The control operation of the control unit 9 will be described with reference to FIG.

When the control operation is started in the control unit 9 (step S121), the detection processing unit 9a measures the cell voltage of the specific cell 521 (step S122). In accordance with this instruction, the cell voltage monitoring unit 8 individually detects the cell voltage of the specific cell 521 (step S123). Then, based on the cell voltage database 9b-121 stored in advance in the database 9b, it is determined whether or not the measured voltage of each cell is within a predetermined range (step S124). In the cell voltage database 9b-121, information indicating a voltage range (at least one of an upper limit value and a lower limit value) in which it is determined that the cell is normally generating power is stored in advance. When the voltages of all the specific cells 521 are within the predetermined range, the detection processing unit 9a proceeds to step S122 and repeatedly measures the voltage of the specific cell 521 (step S124: YES).

On the other hand, when the voltage of the specific cell 521 is not within the predetermined range (step S124: NO), the detection processing unit 9a is stored in advance in the database 9b only for the specific cell 521 whose voltage is not at the predetermined value. Based on the external power supply amount database 9b-122, a power supply instruction is given from the external power supply unit 13 (step S125). The external power supply amount database 9b-122 stores in advance information for converting the measured cell voltage value into the supply amount of power (current) from the external power supply unit 13. As a result, power is supplied from the external power supply unit 13 electrically connected in parallel to only the specific cell 521 whose voltage is not in the predetermined range among the specific cells 521 (step S126).

Normally, not all cells included in the power generation unit 50 have the same characteristics, and the cell voltage varies under the same load condition due to the supply state of fuel, air, cell temperature, and other deterioration. When there is a cell in which the cell voltage is extremely reduced, there is a problem in that the amount of power generation is reduced if the load current is reduced based on the cell voltage.

In the method of the seventh embodiment, since the individual voltage of the specific cell 521 is detected and external power is supplied according to the voltage value, the specific cell 521 is taken out of the cell whose cell voltage is extremely lowered. The load can be arbitrarily adjusted. Therefore, even if the power generation amount of only the cell whose cell voltage is extremely reduced is reduced, the power generation amount of the entire power generation unit 50 is not reduced.

That is, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in each embodiment. Furthermore, you may combine suitably the component covering different embodiment.

Claims

A power generation unit having a plurality of stacked cells;
A fuel supply unit for supplying fuel to the cell, the fuel supply amount being adjustable; and
A voltage monitoring unit that monitors an output voltage of at least one specific cell among the plurality of cells;
A power supply unit for temporarily supplying power to the specific cell;
Detecting a voltage difference between a minimum value of the output voltage that appears after the power is supplied to the specific cell and a response value of the output voltage after the output voltage has reached a minimum value, and according to the voltage difference A fuel cell system including a control unit for controlling the fuel supply amount.
The fuel cell system according to claim 1, wherein the response value corresponds to a steady value that is maintained substantially constant after the output voltage reaches a minimum value.
The fuel cell system according to claim 1, wherein the response value corresponds to a maximum value that appears after the output voltage reaches a minimum value.
The fuel cell system according to claim 1, wherein the control unit supplies the electric power to the specific cell in a state where a load taken out from the power generation unit is constant.
The fuel cell system according to claim 1, wherein the power supply unit includes a capacitor or a secondary battery.
A power generation unit having a plurality of stacked cells;
A temperature monitoring unit that monitors the temperature of at least one specific cell of the plurality of cells;
A power supply unit for temporarily supplying power to the specific cell;
A fuel cell system comprising: a control unit that supplies the power to the specific cell when the temperature is equal to or lower than a reference value.
The fuel cell system according to claim 6, wherein the specific cell corresponds to a cell at an end of the power generation unit.
A power generation unit having a plurality of stacked cells;
A voltage monitoring unit that monitors the voltage of at least one specific cell among the plurality of cells;
A power supply unit for temporarily supplying power to the specific cell;
A fuel cell system comprising: a control unit configured to supply the power to the specific cell when the specific cell voltage is equal to or lower than a reference value.
A power generation unit having a plurality of stacked cells;
A fuel cell comprising: a power supply unit that temporarily supplies power to at least one specific cell among the plurality of cells.