JPS63200468A - Normal temperature type acidic methanol fuel cell - Google Patents

Abstract

PURPOSE:To facilitate operation of a cell even if an environmental temperature is low below 0 deg.C for a long period by disposing a heat-radiating part of a heat pipe at the inside or in the vicinity of the cell and disposing a part of the heat pipe at a vertical depth of 1 m or more below the earth surface and performing a heat retaining process sufficiently therebetween. CONSTITUTION:A cell body is composed of an element cell 1, a fuel tank 2 made of polyethylene, and an exhaustion stopcock equipped with a gas/liquid separating film. When a carbon dioxide gas produced by a discharge reaction at a negative electrode is exhausted from the tank, fuel is prevented from leaking. A methanol aqueous solution of 20 volume% in its methanol concentration is used as the fuel 4. A heated part 42 of a heat pipe 40 is disposed at a vertical depth of about 2 m from the earth surface, and a heat-radiating part 41 of the heat pipe 40 is disposed in the fuel 4 which exists in the fuel tank 2 of the cell 31. A part between the heat-radiating part 41 and heating part 42 of the heat pipe 40 is covered with a heat retaining material 43 such as glass wool so as to be in a heat retaining state. Hence, the cell can be operated even if an environmental temperature is low below 0 deg.C.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a room temperature acidic methanol fuel cell.

[Conventional technology]

In room-temperature methanol fuel cells that use an acidic electrolyte, platinum-based catalysts are preferably used as catalysts for both the positive and negative electrodes, with the positive electrode using oxygen in the air as a reactant, and the negative electrode using a mixture of methanol (CH2OI The mixture is used as a reactant, and the positive electrode is called an air electrode and the negative electrode is called a methanol electrode.Then, the discharge reaction at the positive electrode is 3/20g + 6H" + 68- → 3HzO
At the negative electrode, CHsOH+ Hto-4c Ox + 6 H” +
68-, and the entire battery is a reaction between methanol and oxygen as shown below.

2C) (20H+30□→2COz+4HtOAnd, as a result of the above discharge reaction, water is generated in gaseous form at the positive electrode,
Carbon dioxide gas is generated at the negative electrode.

By the way, the water vapor generated at the positive electrode is formed on the catalyst layer of the positive electrode, so if the ambient temperature in which the battery is used is below 0°C for a long period of time, the generated water vapor cools and condenses near the positive electrode catalyst. It freezes and blocks the catalyst surface and the passage through which oxygen diffuses, making it impossible for the electromotive reaction to proceed. In other words, the room temperature acid methanol fuel cell has a problem in that it cannot basically be used at an ambient temperature where the electrode temperature is below O'C.

In addition, one of the conditions for the three-phase interface on the positive electrode catalyst to function is that it is infiltrated with water, and this water is
A cation exchange membrane with a gel-like polystyrene sulfonic acid film formed on both sides is used as an electrolyte layer in room-temperature acid methanol fuel cells. Similarly to the three-phase interface on the positive electrode catalyst, one of the conditions for it to function is that it is infiltrated with water, and if this water freezes at an ambient temperature below 0°C, it will no longer be able to function. However, there is a problem in that even if the battery is placed in a closed circuit state, the electromotive reaction cannot proceed.

[Problem that the invention seeks to solve]

This invention solves the problem that when the vicinity of the positive electrode catalyst is substantially below O''CC, the reaction product water or the water near the catalyst freezes and the electromotive reaction cannot proceed, and the ambient temperature is below O''CC. The purpose of the present invention is to provide a room-temperature acid methanol fuel cell that can operate even at low temperatures.

[Means for solving problems]

The present invention utilizes the earth's heat as a large-capacity heat source, transports the earth's heat to the inside of the battery or the vicinity of the battery through a heat pipe, heats the battery with the earth's heat, and lowers the temperature near the positive electrode catalyst to 0°C. The battery is maintained at or above O'CC, and the battery can operate even if the environmental temperature drops below O'CC for a long period of time.

That is, the present invention arranges the heat dissipating part of the heat pipe inside or near the battery, and also arranges the heating part of the heat pipe at a vertical depth of 1 m or less in the earth, and maintains sufficient heat between the parts of the earth. The battery is heated using heat as a heat source, allowing the battery to operate even if the environmental temperature drops below 0°C for a long period of time.

To heat the battery using the heat of the earth as described above, specifically, the heating part of the heat pipe is placed in the earth at a vertical depth of 1 m or less, and, for example, the heat dissipating part of the heat pipe is placed in the fuel tank of the battery. Alternatively, the battery can be placed in a water tank or a tank containing a heat medium, and the heat dissipation part of the heat pipe can be placed in the water tank or heat medium tank, or the battery can be placed in a container and the heat pipe This can be achieved by arranging a heat dissipation section in the space of the container.

At that time, by wrapping the entire battery or the entire heating system, including the heating system, with a heat insulating material, the heating effect of the earth's heat can be more efficiently exerted.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is an explanatory diagram showing a first embodiment of the room temperature acid methanol fuel cell of the present invention, which can be heated by the heat of the earth, and FIG. FIG. 3 is an explanatory diagram showing the main constituent members of a unit cell of a room-temperature acid methanol fuel cell.

First, the main body of the battery will be explained based on Fig. 2.
1 is a unit cell, and 2 is a polyethylene fuel tank. 3
is an exhaust plug equipped with a gas-liquid separation membrane, which discharges carbon dioxide generated at the negative electrode by the discharge reaction to the outside of the tank, but prevents fuel from leaking out of the tank. 4 is a fuel, and in this example, a methanol aqueous solution with a methanol concentration of 20% by volume is used.

Next, the main components of the unit cell will be explained based on FIG. A catalyst layer made of platinum black as a catalyst on one side of the substrate 1) a made of high quality carbon paper 1)
b. The other side of the carbon paper base 1) a of the positive electrode 1) has a thickness of about 51) I.
A positive electrode current collector plate 14 made of a hard carbon plate of I1) is disposed, and a catalyst 1 of the positive electrode 1) is disposed on this positive electrode current collector plate 14.
) 1b has holes 14a to facilitate the diffusion of oxygen from the atmosphere.
As many as are permissible in terms of strength and current collection.

12 is an electrolyte layer, 13 is a negative electrode, and this negative electrode 13 is made of porous carbon paper with a thickness of about 2 mm treated with water repellent using polytetrafluoroethylene dispersion. A catalyst layer 13b is formed using ruthenium black as a catalyst. A negative electrode current collector 15 made of a hard carbon plate is disposed on the other side of the carbon paper base 13a of the negative electrode 13, and fuel is supplied to the side of the negative electrode current collector 15 in contact with the negative electrode 13. A groove 15a is provided for this purpose.

The electrolyte layer 12 disposed between the positive electrode 1) and the negative electrode 13 is
This electrolyte layer 1 is produced by forming a gel-like polystyrene sulfonic acid graft polymer membrane 12b, which is a proton conductor, on both sides of a cation exchange membrane 12a.
2 also functions as a separator. Then, when these unit cell components are attached to a fuel tank and tightened, the gel-like polystyrene sulfonic acid graft polymer membrane adheres tightly to the catalyst of the electrode without any gaps between the positive electrode 1), the electrolyte layer 12, the negative electrode 13, and the electrolyte layer. 12 in close contact with each other without any gaps.

Note that 16 is a conducting wire on the positive electrode side, and 17 is a conducting wire on the negative electrode side.

Next, a first embodiment of the present invention, which can be heated using the heat of the earth, will be described with reference to FIG.

Figure 1 shows a normal temperature acid methanol fuel cell installed outdoors. In Figure 1, 31 is a methanol fuel cell, and 32 is a stand on which to place the battery 31. For example, the installation surface (normally , the surface of the earth) 38 to the bottom of the battery 31 is generally set to lθ~100c1), and in this embodiment is set to 50 cs.

33 is a conductive wire, 34 is a device or instrument that uses the battery 31 as a driving power source, and the battery 31 and the device or meter M34 are connected by the conductive wire 33. Reference numeral 35 denotes a container, which protects the battery 31 and others from outdoor wind, rain, and sunlight, and is provided with air inlets and outlets 36 and 37. As for the air inlets and outlets 36 and 37, the lower opening indicated by 37 is usually the air inlet.
The upper opening indicated by 36 serves as an air outlet, but depending on wind or other influences, 37 may serve as an outlet and 36 may serve as an inlet. Although not shown in the drawings, this container 35 is coated with glass wool having a thickness of approximately 2 CI1 as a heat insulating material on the inner surface in order to more efficiently exhibit the heating effect of the earth's heat.

40 is a heat pipe, and the length of the one in this example is about 2.5 mm.
Freon 1) (trade name, trichlorofluoromethane (CC1, F)) is used as the working medium, and the heating part 42 of the heat pipe 40 is placed at a vertical depth of about 2 m from the ground surface. The heat radiation part 41 of the battery 3
It is arranged in the fuel 4 in the fuel tank 2 of 1. and,
A portion of the heat pipe 40 between the heat dissipating section 41 and the heating section 42 is covered with a heat insulating material 43 such as glass wool to maintain heat. In addition, 41a is a fin part for efficiently dissipating heat in the heat dissipation part 41, and 42a is a fin part for efficiently dissipating heat in the heat dissipation part 41.
This is a fin section for efficiently receiving heat at

The temperature below 1m underground, especially from below 2m underground to 20m below ground, varies slightly depending on the region, but the temperature is constant throughout the year.
It has a constant temperature of 5 to 18°C, and its heat capacity can be considered infinite. Therefore, the working medium Freon 1
) (trade name) is heated by the earth's heat in the heating section 42 and evaporates, moves through the heat pipe 4° and radiates heat in the heat radiating section 41 to warm the fuel 4 in the fuel tank 2 of the battery 31. Then, the working medium that has been condensed into liquid due to heat radiation in the heat radiation section 41 flows down the inner wall surface of the heat pipe 40 and returns to the heating section 42 .

As a result of a decrease in the temperature outside the container 35, when the battery temperature decreases and becomes lower than the ground temperature, the battery is heated by the heat pipe 4o using the heat of the ground as a heat source. Even if the temperature decreases, the temperature near the ground is kept close to the ground temperature, and the temperature near the positive electrode 1) never drops below 0°C (therefore, the water near the positive electrode 1) does not freeze (and the discharge does not occur). I can continue.

FIG. 4 shows an example of operation of the methanol fuel cell when the winter nighttime temperature is at least 5.0°C and the daytime temperature is about 12°C.

Curve a in FIG. 4 shows the voltage change of a single cell (that is, per unit cell) over time when the battery of the first embodiment of the present invention is continuously discharged at a discharge current of 50 mA. It is something. Curve d in FIG. 4 shows the change in the single cell over time when the conventional battery shown in FIG. 10 is discharged under the same conditions as the battery according to the first embodiment of the present invention. This shows voltage changes. The battery of this conventional example is one in which the battery is installed outdoors, as in the case of the first embodiment of the present invention, and the battery 31 is placed on a stand 32 as shown in FIG.
A conductive wire 33 connects the battery 31 and the device or instruments 34, and the whole is covered with a container 35 having air inlets and outlets 36 and 37, and extends from the installation surface 38 to the bottom of the battery 31. The distance is 50 cm as in the case of the first embodiment of the present invention. In other words, this conventional battery is
This is a methanol fuel cell installed outdoors without a heating device such as a heat vibrator that uses earth's heat.

However, although not shown, glass wool with a thickness of about 2 am is applied as a heat insulating material to the inner surface of the container 35 as in the case of the previous embodiment.

In the conventional battery shown in Fig. 10, as shown by curve d in Fig. 4, the water near the positive electrode is not frozen during the day, so it can discharge and generate voltage, but at night, as the temperature drops, As the voltage decreases and the temperature near the positive electrode drops below 0° C. and the water near the positive electrode freezes, it becomes impossible to discharge, and the voltage suddenly drops to OV. Then, the next day, the outside air temperature rises and discharge is not possible until the frozen part near the positive electrode thaws, but after the freeze thaws, energization is resumed and the voltage rises as the temperature rises. However, when the outside temperature drops again at night and the water near the positive electrode freezes, it becomes impossible to discharge, and the voltage becomes Ov. In other words, discharge can only occur intermittently.

In contrast, in the battery of the first embodiment of the present invention, the fuel is heated using a heat pipe that uses the heat of the earth as a heat source, so the fuel temperature is maintained at 13 to 15°C even at night. As shown by curve a in FIG. 4, the discharge can continue without being stopped. Moreover, the voltage can also be maintained high. Even if the outside temperature drops further to about -10°C, the discharge will continue without stopping, although the voltage may drop.

Therefore, except in certain cold regions, discharge can continue throughout the entire winter under normal weather conditions.

FIG. 5 is an explanatory diagram showing a second embodiment of the present invention that can be heated using the heat of the earth.

In this second embodiment, a metal water tank 52 is used in place of the stand 32 in the first embodiment, the battery 31 is placed on the water tank 52, and the heat dissipation part 41 of the heat pipe 40 is connected to the water in the water tank 52. It is located in 53. The rest of the structure is almost the same as that of the first embodiment, and members common to both are given the same reference numerals as in FIG. 1 showing the first embodiment.

Also in this second embodiment, when the outside temperature decreases,
The working medium in the heat vibrator 40 is heated by the earth's heat in the heating section 42, evaporates, and moves upward in the heat pipe 40.
Heat is radiated to warm the water, thereby warming the battery 31 placed on the water tank 52. The working medium, which has become a liquid due to heat radiation in the heat radiation part 41, flows down along the inner wall surface of the heat pipe 40 and returns to the heating part 42. is repeated continuously until it approaches the desired value.

As a result, with this battery, even if the atmospheric temperature drops, the battery is warmed by the heat of the earth and can continue to discharge.

In order to efficiently heat the battery using the heat of the earth, it is preferable to keep the portion of the water tank 52 in contact with the battery 31 warm with glass wool or the like.In the embodiment shown in FIG. Glass wool with a thickness of about 2aI is used as a heat insulator 54
It is used to keep the water tank 52 warm. It is also desirable to increase the area of the aquarium wall that is in contact with the battery, for example, the sixth
As shown in the figure, a recess 52a is provided on the top surface of the water tank 52,
The battery 31 is placed in the recess 52a, and a metal piece 55 is inserted into the gap between the wall of the recess 52a and the battery 31 to improve the contact between the battery 31 and the water tank 52, so that the water tank 52 is warmed by the heat of the earth. It is preferable that the heat inside the battery be efficiently transferred to the battery 31.

FIG. 7 shows a battery according to the second embodiment of the present invention shown in FIG. 5 above and a conventional battery shown in FIG. Sometimes the discharge current is 50
It shows the voltage change of a single cell over time when discharging at mA.

The curve d in FIG. 7 shows the voltage change over time of the conventional battery shown in FIG. 10, as in the case explained based on FIG. 4, and in the case of FIG. Similarly,
This shows that the battery shown in FIG. 10 could not discharge at night when the atmospheric temperature was low, and could only discharge intermittently.

In contrast, the battery according to the second embodiment of the present invention shown in FIG. 5 does not stop discharging even when the outside temperature drops at night, as shown by the curve in FIG. It was possible to continue discharging. In addition, in this embodiment, it is relatively easy to increase the capacity of the water tank, so by increasing the water volume by increasing the water tank as shown in FIG. can be easily achieved.

In addition, in place of the above-mentioned water, an aqueous solution of an inorganic substance such as sulfuric acid with a large specific heat, ethanol (C, H80H) can be used as a heat medium.
), an aqueous solution of an organic substance such as glycerin, or oil, but water is the safest and cheapest.

FIG. 8 is an explanatory diagram showing a third embodiment of the present invention that can be heated using the heat of the earth.

In this third embodiment, like the first embodiment shown in FIG. 1 and the second embodiment shown in FIG.
The heat dissipating portion 41 of the heat pipe 40 is placed in the space inside the container 35 (in the embodiment shown in FIG. 8, the space inside the stand 32 is the space inside the stand 32). Therefore, the stand 32 is made of metal so that the heat of the warm air inside the stand 32 is easily transmitted to the battery 31. Except for the above, the structure of this third embodiment is almost the same as that of the first embodiment, and the parts common to both are the same as those of the first embodiment. The same reference numerals as in the figure are given.

Also in this third embodiment, when the outside temperature decreases,
The working medium in the heat pipe 40 is heated by the earth's heat in the heating section 42, evaporates, moves upward in the heat pipe 40, and is radiated in the heat radiating section 41 arranged in the space of the stand 32 of the container 35. to warm the air within the platform 32 of the container 35, thereby warming the battery 31 on the platform 32. The working medium, which has become a liquid due to the heat dissipation in the heat dissipation section 41, flows down along the inner wall surface of the heat pipe 40 and returns to the heating section 42. As a result, even if the atmospheric temperature drops, the battery is warmed by the earth's heat and can continue discharging. In order to heat the battery efficiently, it is preferable to apply glass wool or the like as a heat insulating material to the container 35.Although not shown in the drawings, in this embodiment as well, a thickness of about 2all is applied to the inner surface of the container 35. Glass wool is applied as a heat insulator.

FIG. 9 shows the battery according to the third embodiment of the present invention shown in FIG. 8 above and the conventional battery shown in FIG. When the discharge current is 5
It shows the voltage change of a single cell over time when discharging at 0 mA.

The curve d in FIG. 9 shows the voltage change over time of the conventional battery shown in FIG. 10, as in the case explained based on FIG. 4. Fourth
As in the case shown in the figure, discharge was not possible at night when the atmospheric temperature was low, indicating that discharge could only occur intermittently.

In contrast, the battery according to the third embodiment of the present invention shown in FIG. 8 was able to continue discharging even when the outside temperature dropped at night, as shown by curve C in FIG. .

〔Effect of the invention〕

As explained above, the present invention utilizes the earth's heat as a heat source, uses a heat pipe to carry the earth's heat into or near the battery, and uses the earth's heat to heat the battery. , it is now possible to continue discharging even when the outside temperature drops.

[Brief explanation of the drawing]

Figure 1 shows the first diagram of the room-temperature acid methanol fuel cell of the present invention.
FIG. 2 is an explanatory diagram showing an example, and FIG. 2 is a schematic cross-sectional view showing a cell main body portion of a room temperature acid methanol fuel cell. FIG. 3 is an explanatory diagram showing the main constituent members of a unit cell of a room-temperature acid methanol fuel cell. FIG. 4 is a diagram showing the discharge characteristics of the battery according to the first embodiment of the present invention and the conventional battery. FIG. 5 shows the second diagram of the room-temperature acid methanol fuel cell of the present invention.
FIG. 6 is an explanatory diagram showing an embodiment, and FIG. 6 is a diagram in which the shape of the water tank of the second embodiment shown in FIG. 5 is changed. FIG. 7 is a diagram showing the discharge characteristics of a battery according to a second embodiment of the present invention and a conventional battery. FIG. 8 is an explanatory diagram showing a third embodiment of the room temperature acid methanol fuel cell of the present invention. FIG. 9 is a discharge characteristic diagram of a battery according to a third embodiment of the present invention and a conventional battery. FIG. 10 is an explanatory diagram showing a conventional battery. l...Battery, 2...Fuel tank, 4...Fuel,
1)... Positive electrode, 12... Electrolyte layer, 13...
Negative electrode, 31... Methanol fuel cell, 35... Container, 40... Heat pipe, 41... Heat radiation part, 4
2...Heating part, 43...Heat insulation material, 52...Water tank, 53...Water Figure 3 Figure 4 f14 (Special Ift) No. 60 No. 70

Claims (4)

[Claims] (1) A room-temperature acid methanol fuel cell comprising a positive electrode as an air electrode, a negative electrode as a methanol electrode, and a unit cell having an acidic electrolyte attached to a fuel tank, and using an aqueous methanol solution as fuel, the interior of the cell Alternatively, the heat dissipation section of the heat pipe is placed nearby, and the heating section of the heat pipe is placed at a vertical depth of 1 m or less in the ground, and the part between the heating section of the heat pipe and the heat dissipation section is kept warm. A room-temperature acid methanol fuel cell that is characterized by being able to operate while being heated by the heat of the earth. (2) The room-temperature acid methanol fuel cell according to claim 1, characterized in that the heat dissipation section of the heat pipe is disposed within the fuel tank of the cell. (3) The room-temperature acid methanol fuel cell according to claim 1, wherein the battery is placed on a water tank, and the heat dissipation part of the heat pipe is placed inside the water tank. (4) The room temperature acid methanol fuel cell according to claim 1, wherein the battery is placed in a container, and a heat dissipation section of a heat pipe is arranged in a space inside the container.