JP5049487B2 - Fuel cell device - Google Patents

Description

  The present invention relates to a fuel cell device.

  Fuel cell devices can supply several times to nearly ten times the amount of energy that can be supplied per volume compared to conventional batteries, and by filling with fuel, small electric devices such as mobile phones and notebook PCs Is expected because it can be used continuously for a long time.

  In the fuel cell, a fuel electrode having a catalyst and an oxidant electrode having a catalyst are arranged on opposite surfaces of the electrolyte membrane, a fuel such as hydrogen gas is supplied to the fuel electrode side, and an oxygen gas or the like is supplied to the oxidant electrode side. An oxidizing agent is supplied, and these reactants are electrochemically reacted through the electrolyte membrane.

  When the relationship between current and voltage is measured for a fuel cell while changing the external load, a current-voltage curve as shown in FIG. 11 is obtained. In FIG. 11, Voc is called an open circuit voltage, and Isc is called a short circuit current. Thus, the output voltage decreases as the output current increases. For this reason, the output power has a peak with respect to the output current. Since the fuel cell normally has an electromotive force of about 1 V, a plurality of fuel cells are electrically connected in series to drive an electric device or the like.

  As a method of electrically connecting a plurality of fuel cells in series, a stacked fuel cell stack in which fuel cells are stacked via a conductive separator and a fuel cell are arranged on the same plane and separately wired or the like. And a connected planar fuel cell stack.

  FIG. 12 shows a configuration diagram of a conventional fuel cell device. The fuel cell device 121 supplies electric power to the electric device 124 using the fuel cell stack 122 described above. In order to obtain a stable output, the fuel cell device 121 has various control means 123. For example, there are a pump and a valve for stably supplying fuel to the fuel cell stack, a fan for controlling the operating temperature of the fuel cell stack, a battery for assisting activation of the fuel cell stack, and the like. These control means 123 are electrically connected in parallel with the fuel cell stack 122 and operate using part of the electric power of the fuel cell stack.

  In the fuel cell device, there is a case where nonuniformity occurs in the power generation characteristics of the fuel cell depending on the arrangement of the fuel cell, the supply method of the oxidant or fuel, and the like. For example, in Non-Patent Document 1, F.I. B. Prinz et al. Report that non-uniformity in characteristics occurs using a planar fuel cell stack. That is, the above-described short-circuit current has different characteristics among the fuel cells. The cause of this is not clear, but the short-circuit current is decreasing in the fuel cell downstream of the oxidant or fuel, and it points out problems such as pressure loss, depletion of reactants, and moisture management.

When a fuel cell stack with such non-uniformity is generated with a current greater than the short-circuit current of one of the fuel cells, a reverse current flows through the fuel cell and may deteriorate the characteristics of the fuel cell. . This is presumably because the voltage generated by another fuel cell was applied to the fuel cell, and water electrolysis occurred in the fuel cell. In order to obtain a stable output, in the fuel cell device, the output current is selected so as not to operate above the short-circuit current of each fuel cell.
“Journal of Power Sources” 112, p. 410-418, 2002

  In this way, in the fuel cell device in which a plurality of fuel cells are electrically connected in series, if non-uniformity in power generation characteristics occurs between the fuel cells, the fuel cell stack is matched to the fuel cell having a small short-circuit current. It is necessary to select the output current, and the power generation characteristics of each fuel cell cannot be fully utilized. Furthermore, since a part of the output power of the fuel cell stack is supplied to the control means, there is a problem that the power generation density of the fuel cell device is lowered.

  The present invention has been made to solve such problems of the prior art. A fuel cell stack in which a plurality of fuel cells are electrically connected in series, and the electric power output from the fuel cell stack. In a fuel cell device comprising a control means for controlling the fuel cell stack using a part of the fuel cell stack, even when the short-circuit current of each fuel cell constituting the fuel cell stack is different, the power generation characteristics of each fuel cell The present invention provides a fuel cell device that can be used sufficiently and has a high power generation density.

  A first fuel cell device that solves the above problems includes a fuel cell stack configured by electrically connecting a plurality of fuel cell cells in series, and using a part of electric power output from the fuel cell stack. Control means for controlling the fuel cell stack, and the control means is electrically connected in parallel with at least one fuel cell constituting the fuel cell stack, and is electrically connected to the control means. The short-circuit current of at least one connected fuel cell is larger than at least one short-circuit current of the fuel cell that constitutes the fuel cell stack and is not electrically connected in parallel with the control means. Features.

  A second fuel cell device that solves the above problems includes a fuel cell stack configured by electrically connecting a plurality of fuel cells in series, and a part of electric power output from the fuel cell stack. A control means for controlling the fuel cell stack; an oxidant flow path for supplying an oxidant to the plurality of fuel cells; and a fuel flow path for supplying fuel to the plurality of fuel cells. The control means is electrically connected in parallel with at least one fuel battery cell located upstream of the oxidant flow path among the plurality of fuel battery cells constituting the fuel battery stack. It is characterized by.

  A third fuel cell device that solves the above problems includes a fuel cell stack configured by electrically connecting a plurality of fuel cell cells in series, and using a part of the electric power output from the fuel cell stack. A control means for controlling the fuel cell stack; an oxidant flow path for supplying an oxidant to the plurality of fuel cells; and a fuel flow path for supplying fuel to the plurality of fuel cells. The control means is electrically connected in parallel with at least one fuel battery cell located upstream of the fuel flow path among the plurality of fuel battery cells constituting the fuel cell stack. Features.

  According to the present invention, a large electromotive force can be obtained by connecting cells in series, and at the same time, it is possible to provide a fuel cell device having a high power generation density that can fully utilize the power generation characteristics of each fuel cell.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of a fuel cell device 11 according to an embodiment of the present invention. Reference numeral 14 denotes an electric device driven by the output of the fuel cell device. Reference numeral 12 denotes a fuel cell stack in which a plurality of fuel cells are electrically connected in series. Reference numeral 13 denotes control means for controlling the fuel cell stack. The control means is electrically connected in parallel with only a part of the plurality of fuel cells. The fuel cell connected in parallel with the control means has a short-circuit current larger than that of at least one fuel cell not connected in parallel with the control means.

  In the present specification, the short-circuit current is measured when a plurality of fuel cells are electrically connected in series to form a fuel cell stack and mounted on the fuel cell device.

  The output of the fuel cell may be converted into a predetermined voltage and frequency by a power conversion device such as an inverter or a DC / DC converter and connected to an electrical device. The control means is means for controlling the operating state of the fuel cell stack. For example, a pump or valve for stably supplying fuel to the fuel cell stack, a fan for controlling the operating temperature of the fuel cell stack, a fuel cell A battery for assisting the activation of the stack.

  In FIG. 1, n fuel cells 1 to n are connected in series to supply electric power to an electrical device. The control means 13 is electrically connected in parallel with only the fuel cells 1 to k. As a result, the control means operates using part of the power output from the fuel cell stack. The fuel cells 1 to k connected in parallel to the control means 13 have a short-circuit current larger than at least one of the other fuel cells k + 1 to n.

  The output current of the fuel cell stack is selected so as not to generate power beyond the short-circuit current of any fuel cell. The fuel cells connected in parallel to the control means simultaneously generate the output current of the fuel cell stack and the current supplied to the control means. For this reason, the power generation characteristics of the fuel cells 1 to k can be fully utilized.

  As described above, according to the present invention, it is possible to electrically connect a plurality of fuel cells in series to obtain a high output voltage and to provide a fuel cell device having a high power generation density.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
FIG. 2 shows a fuel cell device 21 according to a first embodiment of the present invention. 22 is a fuel cell stack, 23 is a control means, and 24 is an electric device driven by the fuel cell device. This fuel cell device is used by being incorporated in the casing of the electric device 31 shown in FIG. 32 is an arrangement position of the fuel cell stack, and 33 is an air hole provided in the electric equipment casing.

  FIG. 4 shows a fuel cell stack used in this example. The electrolyte electrode assembly 44 has a fuel electrode 42 and an oxidant electrode 43 on both surfaces of the electrolyte membrane 41. The fuel electrode of the electrolyte electrode assembly and the oxidant electrode of the adjacent electrolyte electrode assembly are stacked so as to face each other. Conductive separators 45 are inserted between the electrolyte electrode assemblies. As described above, the electrolyte electrode assemblies are connected in series. Each separator is formed with an oxidant channel 46 for supplying an oxidant to an adjacent oxidant electrode and a fuel channel 47 for supplying fuel to an adjacent fuel electrode.

  In this embodiment, three fuel cells 25, 26, and 27 are stacked. Methanol is used as the fuel, and oxygen in the atmosphere is used as the oxidant. Fuel methanol is supplied through a pipe (not shown). Further, oxygen consumed by the oxidizer electrode is taken in through the vent hole 33 provided in the electric equipment casing.

  In FIG. 5, the current-voltage curve of each fuel cell 25, 26, 27 is shown. Each short-circuit current is indicated by an arrow in the figure. The short circuit current of the fuel cell 27 is the smallest among the three fuel cells. The cause of this is not clear, but the fuel battery cell 27 is disposed farthest from the vent hole 33, and is presumed to be caused by insufficient supply of the oxidant.

  As shown in FIG. 2, the control means is connected to the fuel cell 25 in parallel. The short circuit current of the fuel battery cell 25 is larger than the short circuit current of the fuel battery cell 27. The control means heats the electrolyte membrane using the electric power charged in the power storage unit when starting the power generation of the fuel cell device, and assists the start of the fuel cell device. The power storage unit is charged using a part of the electric power generated by the fuel battery cell 25.

  The output current of the fuel cell stack is used within a range not exceeding the short-circuit current of the fuel cell 27. A current-voltage curve of the fuel cell device is shown at 28 in FIG. Since the fuel cells are connected in series, a high output voltage can be supplied to the electrical equipment. In addition, a part of the power generated by the fuel cell 25 is used as the power used by the control means, that is, the power for charging the power storage unit, so that the fuel cell device can be stably started. As described above, the fuel cell device of this embodiment can provide a fuel cell device with high power generation density.

Example 2
The present embodiment is a fuel cell device using a planar fuel cell stack. FIG. 6 shows a schematic diagram of the fuel cell device. 62 is a fuel cell stack, 63 is a control means, and 64 is an electric device driven by the fuel cell device. This fuel cell device generates oxygen by supplying oxygen and hydrogen from the outside. The control means controls the flow rate according to the power generation amount of the fuel cell stack, and supplies oxygen and hydrogen to the fuel cell stack.

  FIG. 7A shows a cross-sectional view of each member of the planar fuel cell stack, and FIG. 7B shows a plan view. A fuel electrode 72 and an oxidant electrode 73 are formed on both surfaces of the electrolyte membrane 71 as shown in the figure. A fuel channel 74 for supplying hydrogen to the fuel electrode in contact with the fuel electrode and an oxidant channel 75 for supplying oxygen to the oxidant electrode in contact with the oxidant electrode are formed. On the substrate on which the fuel flow path and the oxidant flow path are formed, an extraction electrode 76 is provided in the shape shown in the figure. Pipes for introducing hydrogen and oxygen are connected to the inlet 77 of the fuel channel and the inlet 78 of the oxidant channel.

  FIG. 8 shows a method for producing an electrolyte electrode assembly. The electrolyte membrane uses a perfluorosulfonic acid group polymer, and the catalyst uses platinum supported on carbon. A solution in which an ion exchange resin solution and a catalyst are mixed is applied to the surface of the carbon paper 81 and dried (FIG. 8A). The carbon paper on which the catalyst layer 82 is formed is cut out into a desired shape, arranged on both surfaces of the electrolyte membrane 83, and pressure-bonded with a press device (FIG. 8B). Thus, three electrolyte electrode assemblies are formed on the same plane (FIG. 8C).

  FIG. 9 shows a manufacturing method of the flow path substrate. Amorphous silicon is formed on the glass substrate 91 as a mask by a CVD method and patterned 92 by plasma etching (FIG. 9A). A channel 93 is formed in the glass substrate by wet etching, and the mask is removed (FIG. 9B). A lead electrode pattern mask is provided, and gold 94 is sputter-deposited on the glass substrate including the flow path (FIG. 9C).

  On both sides of the electrolyte electrode assembly, a fuel flow channel plate and an oxidant flow channel plate are arranged so that the surfaces on which the flow channels are formed are opposed to the electrolyte electrode assembly, and three members are attached by a support plate (not shown). Crimp the. At this time, the extraction electrode is provided with a wiring to enable electric extraction from the fuel cell. In addition, piping is provided at the inlet of the fuel channel and the inlet of the oxidant channel so that hydrogen or oxygen can be supplied to the fuel cell. Thus, a planar fuel cell stack in which the three fuel cells 65, 66, 67 are arranged in the same plane is configured.

  FIG. 10 shows current-voltage curves of the fuel cells 65, 66, and 67 in the fuel cell stack. The short-circuit current is in the order of 65> 66> 67. The cause of the different characteristics among the fuel cells is not clear, but the short circuit current decreases in the fuel cells downstream of oxygen or hydrogen, and there are problems such as pressure loss, reactant depletion, and moisture management. It is done.

  For this reason, it is preferable that the control means is electrically connected in parallel to at least one fuel cell located upstream of the fuel flow path among the plurality of fuel cells constituting the fuel cell stack. Moreover, it is preferable that the control means is electrically connected in parallel to at least one fuel cell located upstream of the oxidant flow path among the plurality of fuel cells constituting the fuel cell stack.

  The three fuel cells 65, 66, and 67 of the fuel cell stack are connected in series by wiring and supply electric power to the electrical equipment. Since the fuel cell device connects the fuel cells in series, a high output voltage can be supplied to the electric device. The fuel cell device can supply electric power to the electric device 64 within a range that does not exceed the short-circuit current of the fuel cell 67. Furthermore, only the fuel cells 65 and 66 are connected in parallel with the control means. Thereby, the control means controls the supply of the fuel and the oxidant by the electric power supplied from the fuel cells 65 and 66, and the power generation of the fuel cell device is stably performed. As described above, the fuel cell device of this embodiment can provide a fuel cell device with high power generation density.

  The fuel cell device of the present invention obtains a large electromotive force by connecting cells in series, and at the same time, can sufficiently utilize the power generation characteristics of each fuel cell, and has a high power generation density. Can be used.

It is a block diagram which shows an example of the fuel cell apparatus in this invention. 1 is a configuration diagram of a fuel cell device in Embodiment 1. FIG. 1 is a schematic diagram of an electric device driven by a fuel cell device in Example 1. FIG. 1 is a schematic diagram of a fuel cell stack used in a fuel cell device in Example 1. FIG. It is a figure which shows the current-voltage characteristic of the fuel battery | cell apparatus in Example 1, and a fuel battery cell. FIG. 3 is a configuration diagram of a fuel cell device in Example 2. 4 is a schematic diagram of a fuel cell stack used in a fuel cell device in Example 2. FIG. 4 is a schematic diagram of a fuel cell stack used in a fuel cell device in Example 2. FIG. 6 is a diagram showing a method for producing an electrolyte electrode assembly in Example 2. FIG. FIG. 10 is a diagram showing a flow path manufacturing method in Example 2. It is a figure which shows the current voltage characteristic of the fuel battery cell in Example 2. FIG. It is a figure explaining the current voltage characteristic of a fuel cell. It is a block diagram of the conventional fuel cell apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fuel cell apparatus 12 Fuel cell stack 13 Control means 14 Electrical equipment 21 Fuel cell apparatus 22 Fuel cell stack 23 Control means 24 Electrical equipment 25, 26, 27 Fuel cell 28 Current voltage curve of fuel cell apparatus 31 Electrical equipment 32 Fuel cell Stack Arrangement Position 33 Air Vent 41 Electrolyte Membrane 42 Fuel Electrode 43 Oxidant Electrode 44 Electrolyte Electrode Assembly 45 Conductive Separator 46 Oxidant Channel 47 Fuel Channel 62 Fuel Cell Stack 63 Control Unit 64 Electric Equipment 65, 66, 67 Fuel cell 71 Electrolyte membrane 72 Fuel electrode 73 Oxidant electrode 74 Fuel channel 75 Oxidant channel 76 Extraction electrode 77 Fuel channel inlet 78 Oxidant channel inlet 81 Carbon paper 82 Catalyst layer 83 Electrolyte membrane 91 Glass substrate 92 Mask patterning 93 Flow path 94 Removal And the electrode 121 a fuel cell device 122 fuel cell stack 123 the control means 124 electrical equipment

Claims (3)

A fuel cell stack configured by electrically connecting a plurality of fuel cells in series, and a control that operates using part of the power output from the fuel cell stack and controls the operating state of the fuel cell stack And the control means is electrically connected in parallel with only a part of the fuel cells constituting the fuel cell stack, and the other part of the fuel cell constituting the fuel cell stack. not connected to the cell electrically in parallel, the short-circuit current of the control means and electrically to said portion being connected in parallel fuel cell, the fuel cell stack, and control means A fuel cell device, wherein the fuel cell device is larger than a short-circuit current of the other portion of the fuel cells that are not electrically connected in parallel. A fuel cell stack configured by electrically connecting a plurality of fuel cells in series, and a control that operates using part of the power output from the fuel cell stack and controls the operating state of the fuel cell stack means comprises an oxidant flow channel for supplying an oxidant to the plurality of fuel cells, a fuel passage for supplying fuel to the plurality of fuel cells, control means, Of the plurality of fuel cells constituting the fuel cell stack, only a part of the fuel cells including the fuel cell located upstream of the oxidant flow path is electrically connected in parallel. A fuel cell device, wherein the fuel cell device is not electrically connected in parallel with fuel cells of other parts constituting the fuel cell stack . A fuel cell stack configured by electrically connecting a plurality of fuel cells in series, and a control that operates using part of the power output from the fuel cell stack and controls the operating state of the fuel cell stack Means, an oxidant flow path for supplying oxidant to the plurality of fuel cells, and a fuel flow path for supplying fuel to the plurality of fuel cells, the control means comprising the fuel Of the plurality of fuel cells constituting the battery stack, the fuel cell is electrically connected in parallel with only some of the fuel cells including the fuel cell located at the most upstream of the fuel flow path. A fuel cell device, wherein the fuel cell device is not electrically connected in parallel with fuel cells of other parts constituting the stack .

Images