JP4100096B2 - Polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer electrolyte fuel cell.
[0002]
[Prior art]
The polymer electrolyte fuel cell has advantages such as high output, long life, little deterioration due to start / stop, low operating temperature (about 70-80 ° C), and no need for precise differential pressure control. Therefore, it is expected to be used in a wide range of applications such as electric power sources for electric vehicles, distributed power sources for business use and home use.
[0003]
Among these applications, a distributed power source (for example, a cogeneration power generation system) equipped with a polymer electrolyte fuel cell takes out electricity from the polymer electrolyte fuel cell, and at the same time, generates heat from the battery during power generation with hot water. It is a system that tries to make effective use of energy by collecting as
[0004]
Therefore, in such a distributed power supply, it is important how to reduce the heat loss from the fuel cell. However, from such a viewpoint, there is no technique for preventing heat dissipation from the polymer electrolyte fuel cell.
[0005]
[Problems to be solved by the invention]
Usually, the heat from the fuel cell is deprived by contact with the atmosphere, so there is a problem that the amount of heat that can be recovered as hot water decreases. In order to solve this problem, it is conceivable to coat the fuel cell with a heat insulating material.
[0006]
However, since the polymer electrolyte fuel cell uses a combustible gas containing hydrogen, in the unlikely event that hydrogen leaks from the fuel cell, the hydrogen stays in the vicinity of the fuel cell due to the insulation used for the coating. Therefore, simply covering the fuel cell with a heat insulating material has a problem in practicality.
[0007]
Furthermore, in a normal polymer electrolyte fuel cell, a large number of single cells contributing to power generation are arranged in series, and two electrically conductive separators constituting each single cell are exposed to the outside. For this reason, when the separator is dewed due to temperature fluctuation, there is a possibility that an external short circuit may occur between the separators due to the voltage of a single cell, and simply covering the fuel cell with a heat insulating material has a problem in practicality.
[0008]
Therefore, the present invention intends to make it possible to prevent such external short-circuiting due to retention of flammable gas or condensation.
[0009]
[Means for Solving the Problems]
A polymer electrolyte fuel cell is a single cell based on a solid polymer electrolyte membrane having a function of permeating hydrogen ions, electrode layers formed on both sides of the membrane, and a separator disposed so as to sandwich the electrode layer. In general, a plurality of single cells are connected in series to obtain sufficient power.
[0010]
A solid polymer electrolyte membrane having a function of permeating hydrogen ions is generally a polymer membrane in which a part of fluorine of a fluorine-based polymer is replaced with sulfonic acid, and is a polymer membrane having a function of moving hydrogen ions. If it exists, it is applicable to the present invention. For example, a fluorine chain contained in a polymer chain having tetrafluoroethylene as a basic unit is passed through about 2 to 5 alkyl chains (—CF ₂ CF ₂ —, —CF ₂ CF ₂ (CF ₃ ) —, etc.). Thus, there is a polymer membrane having a sulfonic acid group (—SO ₃ H) at the end of an alkyl chain.
[0011]
The electrode layer is a layer having platinum or an alloy of different elements such as platinum and ruthenium as an electrode catalyst, and having the electrode catalyst, carbon powder, and a binder.
[0012]
The fuel gas supplied to the polymer electrolyte fuel cell is pure hydrogen or a gas containing hydrogen, and this hydrogen is oxidized by an oxidation reaction (formula 1) on the electrode catalyst. At the same time, the oxygen reduction reaction (formula 2) proceeds on the opposite electrode catalyst. Hydrogen ions generated by the oxidation reaction of hydrogen are transferred to the solid polymer electrolyte membrane, and the hydrogen ions are combined with oxygen in the opposite electrode layer to generate water.
[0013]
H ₂ → 2H ⁺ + 2e ⁻ (Formula 1)
2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O (Formula 2)
Due to this battery reaction, the electromotive force of a single cell is about 1.2 V, and when a power is generated with a load connected, a voltage of about 0.5 to 0.7 V can be obtained. By doing so, a voltage of tens to hundreds of volts can be taken.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The contents of the present invention will be described below with reference to examples. In addition, this invention is not limited to the Example described below.
[0015]
The configuration of the polymer electrolyte fuel cell is shown in FIG. The power generation unit is a single cell 101, and usually DC power is taken out by a multi-layered cell of several tens or more cells. This single cell 101 includes a membrane-electrode assembly (a film made of 102 and 103 in the enlarged view) in which electrode layers are provided on both surfaces of a solid polymer electrolyte membrane 102, and two single cell separators sandwiching the membrane-electrode assembly. The gasket 105 is inserted between the single cell separators 104.
[0016]
An enlarged view of the periphery of this membrane-electrode assembly is shown in FIG. On one side of the single cell separator 104, a groove through which the fuel gas flows is processed. On the other side of the single cell separator 104, a groove through which an oxidant gas, usually air, flows is processed.
[0017]
These are laminated and the positive electrode current collector plate 113 and the negative electrode current collector plate 114 are disposed at the ends. Pressure is applied from the outside of the current collector plates 113 and 114 by the end plate 109 through the insulating plate 107. Parts for fixing the end plate 109 are a bolt 116, a disc spring 117, and a nut 118.
[0018]
The conditions for fixing the laminated body composed of the single battery (single cell) 101, the separator for cooling water 108, the end plate 109, the current collecting plates 113 and 114, etc., with the fastening parts including the bolt 116, the disc spring 117, and the nut 118 are as follows: The laminated body sandwiched between the two end plates is compressed by a hydraulic press and left as it is for 5 hours, and then the nut 118 is tightened.
[0019]
Fuel gas, oxidant gas, and cooling water are supplied from connectors 110, 111, and 112 provided on the end plate 109, and are discharged from a connector provided on the other end plate 109. DC power (output) can be obtained from the positive current collector 113 and the negative current collector 114.
[0020]
In the polymer electrolyte fuel cell, the single cell separator 104 constituting each single cell is usually exposed to the outside. Therefore, there is a problem that the heat recovery rate is reduced due to heat radiation from the fuel cell. In this embodiment, the problem is solved by the following means.
[0021]
The means can be realized by covering a part or the whole of the outside of the fuel cell with the heat insulating component 121.
[0022]
The property required of the heat insulating material constituting the heat insulating part 121 is that the thermal conductivity is small, and is preferably smaller than the thermal conductivity (0.4 W / mK) of glass wool generally used as a heat insulating material.
[0023]
In consideration of use in a cold region, the thermal conductivity of the heat insulating material is more preferably less than 0.1 W / mK, for example, in the vicinity of 0.02 to 0.03 W / mK.
[0024]
In order to realize such excellent heat insulating properties, since the thermal conductivity of air is small in a closed state without convection, a material having many independent bubbles in which the heat insulating material does not connect to the outside is suitable.
[0025]
Further, the heat insulating component 121 has not only independent bubbles but also a hole penetrating the heat insulating component 121, which can be achieved by covering a part or the entire surface of the fuel cell.
[0026]
The reason for providing such a through hole is that by covering the fuel cell with the heat-insulating component 121, it is possible to easily release the staying combustible gas and to discharge condensed water to the outside.
[0027]
The shape and size of the through-hole are arbitrary, but in order to prevent heat dissipation due to convection in the atmosphere, a through-hole capable of transmitting a combustible gas or the like is required. 10 to 1000 μm is desirable for permeation of combustible gas, and 1 to 10 mm for permeation of condensed water.
[0028]
In general, since hydrogen has a lower specific gravity than air, it tends to diffuse upward, and heated air also tends to move upward. A part having a through hole that is mainly considered to be transparent can be arranged.
[0029]
On the other hand, since dew condensation water tends to accumulate on the bottom surface due to gravity, a heat insulating part covering the bottom surface or side surface of the fuel cell can be provided with a part having a through-hole mainly considering the permeation of dew condensation water.
[0030]
As an alternative method, a plurality of plate-like heat-insulating parts are arranged on the bottom surface of the fuel cell, and a 1-10 mm gap is provided between these parts, thereby using heat-insulating parts with no through holes. It is also possible to do.
[0031]
Examples of materials applicable to the heat insulating parts described above include polyurethane foam, styrene foam, and foamed rubber.
[0032]
Further, a foamed rubber material imparted with flame retardancy, nonflammability, and self-extinguishing functions can also be applied to the present invention.
[0033]
The heat insulating component is not particularly limited to the presence or absence of foaming and the type of material, and it is sufficient that the heat insulating component has a thermal conductivity smaller than 0.4 W / mK.
[0034]
Note that a fluorine-based electrolyte membrane is used for the solid polymer electrolyte membrane 102 in FIG. 1, and a platinum-based catalyst is used for the catalyst of the catalyst layer 103. As the gas diffusion layer 106, carbon paper having a thickness of 200 μm is used.
[0035]
An anode gas channel having a width of 1 mm and a depth of 0.5 mm is provided on the anode side separator surface, and a cathode gas channel having a width of 1 mm and a depth of 0.8 mm is provided on the cathode side separator surface.
[0036]
The polymer electrolyte fuel cell of the present embodiment has a configuration in which a plurality of 50 single cells are connected in series, and a cooling water separator 108 in which a cooling water flow path is formed is inserted every two cells.
[0037]
This is because the cooling water is supplied to the cooling water separator 108 by a pump installed outside the battery, and the heat generated inside the battery by the heat exchanger provided in the middle of the cooling water pipe connecting the pump and the battery. It is for recovering.
[0038]
Polyurethane foam is used for the heat insulating part 121. These are installed so as to cover the side surfaces (four surfaces) of the fuel cell, and the side surfaces of the heat insulating component 121 are fixed with an adhesive.
[0039]
In order to reduce heat radiation from the end plate 109, an end plate 109 made of ABS resin having a thickness of 40 mm was used. Although not shown in FIG. 1, the end plate 109 may be made of metal, and a heat insulating part may be installed outside the end plate 109 to cover the entire surface of the polymer electrolyte fuel cell.
[0040]
The positive and negative current collector plates 113 and 114 with output terminals were formed by protruding the terminal portions of the current collector plates from the holes of the heat insulating component 121. By connecting this terminal to an external load, electric power can be taken out. These current collector plates were made of nickel. An insulating plate 107 was inserted between the current collecting plates 113 and 114 and the end plate 109 to achieve electrical insulation.
[0041]
In this example, the electrode effective area capable of generating power was 100 cm ² and the output was measured at a current of 50 A. The gas supplied to the anode was hydrogen, the gas supplied to the cathode was air, and the pressure was normal pressure (one atmospheric pressure). The utilization rates of hydrogen and oxygen were 70% and 40%, respectively. The temperature of the cooling water supplied to the cell was set to 70 ± 2 ° C. The battery of this example is designated as S1.
[0042]
The heat-insulating part 132 having no through holes used in the above-described embodiment and the heat-insulating part 131 having four fine holes per 100 cm ² with a diameter of 0.1 mm in the heat-insulating part used in the above-described embodiment. Then, three types of parts made of the heat insulating part 133 in which holes having a diameter of 3 mm and four holes per 100 cm ² were formed in the heat insulating part used in the above-described embodiment were manufactured.
[0043]
Since the heat insulating component 132 is intended only to prevent heat dissipation, it is disposed on the side surface of the fuel cell as shown in FIG. Since the heat insulating component 131 is assumed to be a case where flammable gas leaks, the heat insulating component 131 is disposed on the upper part of the fuel cell. The heat insulating component 133 is disposed on the bottom surface of the fuel cell in order to discharge condensed water. These heat insulating parts and between the heat insulating parts and the end plate 119 were fixed with an epoxy resin adhesive. The battery of this example is designated S2.
[0044]
As a comparative example, a conventional type fuel cell that does not consider heat insulation was manufactured by removing the heat insulating parts used in the above-described polymer electrolyte fuel cell. Let R be the battery of the comparative example.
[0045]
A device in which the batteries S1 and S2 and the battery R of the comparative example were incorporated in the power generation system shown in FIG. 3 was manufactured. A device equipped with the battery S1 is designated as A1, a device equipped with the battery S2 is designated as A2, and a device equipped with the battery R is designated as A3. These devices differ only in the type of battery, but the other components and configurations are the same.
[0046]
In FIG. 3, 1001 is natural gas, 1002 is air, 1003 is a reformer, 1005 is a fuel cell stack, 1006 is distilled water, 1007 is a hot water tank, 1008 is a pump for anode gas, and 1009 is a pump for cathode gas. 1010 is a circulating water pump, 1011 is a heat exchanger, 1012 is a fuel cell, 1013 is a cathode gas discharge pipe, and 1014 is an anode gas discharge pipe.
[0047]
In each apparatus, a fuel gas having a hydrogen concentration of 70% was introduced into the anode by reforming the city gas, and air was supplied to the cathode.
[0048]
The water temperature of the hot water storage tank 1007 at the start of power generation was 40 ° C., and the temperature of the circulating water supplied to the fuel cell 1012 was also 40 ° C. The test was carried out in a constant temperature laboratory having an air conditioner so that the outside air temperature was constant at 10 ° C.
[0049]
The utilization rates of hydrogen and oxygen were 70% and 40%, respectively, and were constant for each current. The gas pressure was normal pressure.
[0050]
The current density was set to 0.5 mA / cm ² and a continuous power generation test was performed.
[0051]
The apparatuses A1 and A2 of the present invention were able to obtain 60 ° C. hot water after about 4 hours by continuous power generation. On the other hand, in the case of the apparatus A3 equipped with the battery R of the comparative example, it took about 5 hours to obtain the same hot water, so that the heat recovery efficiency was obtained when the apparatuses A1 and A2 of the present invention were used. We were able to prove that
[0052]
【The invention's effect】
The heat-recovery component of the present invention improves the efficiency of heat recovery from the polymer electrolyte fuel cell.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a fuel cell in which a heat insulating component of the present invention is arranged.
FIG. 2 is a plan view of a fuel cell in which the heat insulating parts of the present invention are arranged.
FIG. 3 is a diagram of a power generation system equipped with the polymer electrolyte fuel cell of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Single cell, 102 ... Solid polymer electrolyte membrane, 103 ... Catalyst layer, 104 ... Single cell separator, 105 ... Gasket, 106 ... Gas diffusion layer, 107 ... Insulating plate, 108 ... Cooling water separator, 109 ... End Plate 110, connector for anode gas piping, 111 ... connector for cooling water piping, 112 ... connector for cathode gas piping, 113, 114 ... current collector plate, 116 ... bolt, 117 ... disc spring, 118 ... nut, 121 ... heat insulation 1001 ... Natural gas, 1002 ... Air, 1005 ... Fuel cell stack, 1006 ... Distilled water, 1007 ... Hot water storage tank, 1008 ... Anode gas pump, 1009 ... Cathode gas pump, 1010 ... Circulating water pump DESCRIPTION OF SYMBOLS 1011 ... Heat exchanger, 1012 ... Fuel cell, 1013 ... Cathode gas discharge piping, 1014 ... Ano Gas discharge pipe.

Claims (3)

The entire surface or a part of a laminate in which a plurality of unit cells each having a membrane-electrode assembly having a catalyst layer and a hydrogen ion conductive polymer membrane sandwiched between two single cell separators having gas flow grooves are laminated. Is coated with a heat insulating component having a thermal conductivity of less than 0.4 W / mK, and has a through-hole penetrating the heat insulating component that releases a combustible gas .   2. The polymer electrolyte fuel cell according to claim 1, wherein the heat insulating component has a nonflammability, flame retardancy, or self-extinguishing function.   A power generation system in which an apparatus for continuously producing a gas containing hydrogen or an apparatus for storing hydrogen and a polymer electrolyte fuel cell are connected to each other via a pipe through which a gas containing hydrogen is circulated. 3. The power generation system according to claim 1, wherein the molecular fuel cell is a solid polymer fuel cell according to claim 1, wherein power is generated using a gas containing hydrogen supplied from the device.

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