Patent Application
20070166587
The present invention relates to a fuel cell.
In recent years, with the advent of an information society, as the information volume handled by electronic apparatuses such as a personal computer has been remarkably increased, the power consumption of the electronic apparatuses has been also incremented remarkably. Particularly, portable electronic apparatuses have had the problem of the increase of the power consumption accompanied by the increment of throughput capacity. Currently, in these portable electronic apparatuses, a lithium-ion cell is generally used as a power source, but the energy concentration of the lithium-ion cell is coming close to a theoretical limit. Therefore, so as to increase the continuous-use period of the portable electronic apparatuses, there had been limitation that the power consumption has to be reduced by the control of CPU driving frequency.
Under these circumstances, it is expected that instead of the lithium-ion cell, using a fuel cell having the high energy concentration and heat-exchange effectiveness as a power source of electronic apparatus remarkably improves the lifetime of the portable apparatuses.
The fuel cell is composed of a fuel electrode and an oxidizer electrode (hereinafter, they are also referred to as “catalyst electrodes”), and an electrolyte provided therebetween. A fuel is supplied to the fuel electrode and an oxidizer is supplied to the oxidizer electrode, whereby electricity is generated by the electrochemical reaction. Though hydrogen is generally used as fuel, methanol, which is easily handled and purchased at low price, is also used. A methanol reforming type fuel cell, which generates hydrogen by reforming methanol, and a direct type fuel cell, which directly uses methanol as fuel, have been well developed in recent years.
When the hydrogen is used as the fuel, the reaction at the fuel electrode is given by the following formula (1):
3H2→6H++6e−. (1)
When the methanol is used as fuel, the reaction at the fuel electrode is given by the following formula (2):
CH3OH+H2O→6H++CO2+6e−. (2)
Further, in either case, the reaction in the oxidizer electrode is given by the following formula (3):
3/2O2+6H++6e−→3H2O. (3)
Particularly, in the direct type fuel cell, since a hydrogen ion can be obtained from an aqueous methanol solution, a reforming instrument is not required, whereby the direct type fuel cell is advantageous to apply to portable apparatuses. In addition, the energy density is very high since the aqueous methanol solution is used as fuel.
Here, in general, there is a problem that the fuel cell is less reliable at its startup than other power sources. Especially, since the power generation efficiency of the direct type fuel cell decreases as the temperature drops, if the temperature is low, a desired voltage/current cannot be supplied, whereby the apparatuses may not start up.
To improve the inferiority at the startup of the fuel cell, for example, there is proposed a method for compulsorily raising the temperature up to a predetermined temperature by adding a thermo-electric heater to the fuel cell (Japanese Patent Application Laid-open No. 1-187776: Patent Document 1). Further, there is proposed a method for raising the temperature of the fuel cell up to an optimal operating temperature in a short time, for example, upon starting the fuel cell, the methanol is directly supplied to an air chamber and the methanol is combusted directly by an air electrode, thereby rapidly raising the temperature of the fuel cell (Japanese Patent Application Laid-open No. 5-307970: Patent Document 2).
However, in the conventional method for adding an electric heater, there were problems that a device to which the electric heater was added was getting larger and a power source for the electric heater was separately required. In addition, in a method for directly combusting methanol by an air electrode, since a pipe for supplying the methanol to the air electrode was needed, when the method was applied to a cell stack including a plurality of unit cells of a fuel cell, the structure thereof became complicated and the device got large.
Meanwhile, when the fuel cell is used for portable apparatuses such as a cellular phone, since the fuel cell is frequently used in the open air, the fuel cell is required to operate under the low-temperature atmosphere of approximately 0° C. Therefore, if the fuel cell is used for portable apparatuses, it is further preferable that there is provided a portable fuel cell that has a convenient mechanism for bringing up outputs to a normal level by raising the temperature of the fuel cell in a short time in spite of a low ambient temperature.
In the view of such circumstances mentioned above, an object of the present invention is to provide a technique capable of improving the availability, even if an outside air temperature not high, by providing a heating unit that raises the temperature of a fuel cell with a convenient mechanism.
According to the present invention, there is provided a fuel cell comprising a unit cell that includes a solid electrolyte membrane, a fuel electrode and an oxidizer electrode disposed on the solid electrolyte membrane, a heating means that heats the unit cell, and a fuel supplying system that supplies fuel to the fuel electrode, wherein part of the fuel is supplied from the fuel supplying system to the heating means and the heat generated when the fuel supplied to the heating means is combusted by the heating means is conducted to the unit cell, so that the unit cell is heated.
In the fuel cell of the present invention, heat of a heating means is conducted to a unit cell, thereby heating the unit cell. Further, part of fuel supplied to a fuel electrode is supplied to the heating means to be combusted. Therefore, the unit cell can be certainly heated by using the combustion heat of the fuel. Accordingly, the startup characteristic of the cell can be improved by means of a simple mechanism even when a temperature of the outside air in which the fuel cell is used is low.
The fuel cell of the present invention may have one unit cell or a plurality of unit cells.
In the fuel cell of the present invention, the heating means may be provided in contact with the unit cell. Further, in the fuel cell of the present invention, the heating means may have a heating element and a heat conductor provided in contact with the heating element. By this configuration, the heating element may be provided in contact with the unit cell directly or via the heat conductor. Therefore, combustion heat generated in the heating element is efficiently conducted to the unit cell disposed in contact with the heat conductor via the heat conductor provided in contact with the heating element, thereby heating the unit cell. Accordingly, even when the temperature of the environment where the fuel cell is used is low, the unit cell is certainly heated, whereby the startup characteristic of the fuel cell can be improved.
In the fuel cell of the present invention, the heating means may include a heating catalyst for combusting the fuel. By this configuration, the fuel can be certainly combusted by using the catalyst in the heating means. Consequently, the unit cell can be certainly heated.
In the fuel cell of the present invention, the heating element may include the heating catalyst. By this configuration, the unit cell provided in contact with the heating element directly or via the heat conductor can be easily heated.
In the fuel cell of the present invention, liquid fuel may be directly supplied to the fuel electrode. When the liquid fuel is directly supplied, although the startup characteristic is especially required to be improved under a low temperature, that requirement is satisfied in a simple configuration according to the present invention. Even when the liquid fuel is directly supplied to the fuel electrode, a unit cell can be easily heated with the simple configuration. Therefore, the fuel cell demonstrates the satisfactory output characteristic even when the outside air is at low temperature.
The fuel cell of the present invention comprises a plurality of unit cells, a plurality of first electrodes that are provided on one side of a solid electrolyte membrane and a plurality of second electrodes that are provided on the other side of the solid electrolyte membrane, where a second electrode is disposed opposite to a first electrode, wherein the unit cell may be composed of a pair of a first electrode and a second electrode opposed to each other and the solid electrolyte membrane, and the heating means may heat a plurality of the unit cells.
In the fuel cell of the present invention, the plurality of unit cells are configured to share a solid electrolyte membrane. By this configuration, a plurality of unit cells is stably disposed on a plane. In addition, in the fuel cell of the present invention, a plurality of unit cells is heated by the heating means. Therefore, each unit cell constituting the fuel cell can be heated without fail. Accordingly, the good startup characteristic can be secured even when the fuel cell is used under a low temperature.
In the fuel cell of the present invention, the heating means may be provided in contact with the solid electrolyte membrane. When the solid electrolyte membrane is provided in contact with the heating means, the solid electrolyte membrane is heated, thereby a plurality of unit cells sharing the membrane can be simultaneously heated at one dash. Accordingly, even in the fuel cell in which a plurality of unit cells is disposed two-dimensionally, each unit cell can be heated without fail. Therefore, the good startup characteristic can be obtained even when the fuel cell is used at a low temperature.
In the fuel cell of the present invention, the heating means may be provided in contact with a plurality of first electrodes. By this configuration, a plurality of unit cells can be simultaneously heated from one electrode side.
In the fuel cell of the present invention, the heating means may be provided in contact with the oxidizer electrode. Further, in the present invention, the first electrode may be the oxidizer electrode. By this configuration, even in the fuel cell in which the liquid fuel is directly supplied to the fuel electrode, the oxidizer electrode which has low heat capacity and is easily heated is heated faster, thereby heating the entire cell efficiently.
The fuel cell of the present invention may have a fuel recovering means that recovers the fuel having passed through the fuel electrode into the heating means. By this configuration, unused fuel contained in the fuel having passed through the fuel electrode may be used for the combustion in the heating means. Accordingly, the efficiency in the use of the fuel can be improved.
The fuel cell of the present invention may have an oxidizer supplying means that supplies an oxidizer to the heating means. By this configuration, the fuel reaction of the fuel can be further rapidly performed in the heating means. Therefore, the unit cell can be more rapidly heated.
The fuel cell of the present invention may have a cooling water supplying means that supplies cooling water to the heating means. By this configuration, the heating means can be certainly cooled after the unit cell is heated. Therefore, the heating means avoids being overheated, whereby the fuel cell can operate safely.
In the present invention, the fuel cell may further comprise a temperature sensor that measures a heating temperature in the heating means or temperature of the fuel cell, and a control unit that controls supply of the fuel from the fuel supplying system to the heating means based on the temperature measured by the temperature sensor. By this configuration, the heating means can be driven in response to the temperature of the fuel cell. Here, the temperature of the fuel cell may indicate the temperature of the inside, a surface, waste liquid, exhaust air of the fuel cell or outside air around the fuel cell. A certain number of these kinds of temperature may be selected and properly utilized.
In the fuel cell of the present invention, the fuel supply system may include a detachable fuel cartridge. By this configuration, even when the fuel is consumed, the cartridge can be exchanged so that the fuel can be refilled. In the fuel cell of the present invention, the fuel held in the fuel cartridge may be supplied to the heating means.
In the fuel cell of the present invention, the fuel cartridge may have a first chamber that retains first liquid fuel and a second chamber that retains second liquid fuel, wherein the first chamber may have a fuel discharging exit for discharging the first liquid fuel to the heating means and the second chamber may have the fuel discharging exit for discharging the second liquid fuel to a main body of the fuel cell.
Since the fuel cartridge has the first chamber and the second chamber, the fuel cartridge can include high-concentration fuel in addition to low-concentration fuel used for the supply. Since the high-concentration fuel is supplied to the heating means, where the fuel cell can be rapidly heated, the low-temperature startup characteristic is more improved. In the present invention, the fuel cell may have a mixing tank for mixing the first liquid fuel and the second liquid fuel.
Moreover, it is useful as an aspect of the present invention that an arbitrary combination of the above-mentioned components, or components or representation of the present invention is mutually substituted between methods and devices. For example, according to the present invention, an electronic device on which the fuel cell system is mounted can be provided.
As described above, according to the present invention, even if an outside air temperature is low, the temperature of the fuel cell can be raised and the availability of a device is improved.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. A common reference numeral is given to the same components throughout all drawings and the repetitive explanation will be omitted.
Further, the application of the fuel cell described in embodiments below is not specifically limited. For example, the fuel cell is properly used for small-sized electric apparatuses such as a cellular phone, a portable personal computer including a notebook computer, a PDA (Personal Digital Assistant), a variety of cameras, a navigation system and a portable music reproducing player.
In the fuel cell 1301, fuel 124 contained in the fuel tank 1327 is supplied to the combustion unit 1303 and a unit cell structure 101. In the fuel supplying system at this time, the pump 1329 for controlling the flow of the fuel 124 is provided between the fuel tank 1327 and the combustion unit 1303. Moreover, in the fuel cell shown in
Though not shown, the fuel 124 contained in the fuel tank 1327 may be supplied to the unit cell structure 101 and a part of the fuel 124 supplied from the fuel tank 1327 may be supplied to the combustion unit 1303. Further, the fuel 124 unused at the fuel electrode 102 may be returned to the fuel tank 1327. In addition, the fuel electrode 102 may include the fuel tank 1327 and in this case, a part of the fuel 124 supplied from the fuel electrode 102 is supplied to the combustion unit 1303.
The combustion unit 1303 has a catalyst capable of combusting the fuel 124. When the fuel 124 and a combustion oxidizer are supplied to the combustion unit 1303, the fuel 124 is combusted, thereby generating the combustion heat. And the unit cell structure 101 being in contact with the combustion unit 1303 is heated by the combustion heat. For example, air or oxygen gas may be used as a combustion oxidizer. In addition, a thermometer 1341 for controlling the combustion heat is provided in the combustion unit 1303. Moreover, in the other embodiments, the thermometer 1341 is also provided in the combustion unit 1303.
In the fuel cell 1301, since the combustion unit 1303 that produces heat by the supply of the fuel 124 is in contact with the unit cell structure 101, the unit cell structure 101 can be heated in a simple configuration. Accordingly, the unit cell structure 101 can be easily heated even if the fuel cell 1301 is used at low temperature, whereby the startup characteristic can be improved.
Further, one unit cell structure 101 is shown in
In addition, a heat transfer member for transferring the combustion heat generated in the combustion unit 1303 may be provided between the combustion unit 1303 and the unit cell structure 101. By this configuration, the combustion heat can be efficiently transferred to the unit cell structure 101. For example, metals with a high thermal conductivity such as copper, aluminum and titanium can be used as a heat transfer member.
In the fuel cell 1311, the fuel tank 1309 is provided in contact with the fuel electrode 102 constituting the unit cell structure 101, whereby the fuel 124 can be supplied directly to the fuel electrode 102. In the initial state, the fuel 124 with a concentration suitable for supplying it to the unit cell structure 101 is filled in the fuel tank 1309. The detailed configuration of the unit cell structure 101 will be described below.
In this embodiment and a following embodiment, the fuel 124 indicates liquid fuel supplied to the unit cell structure 101 and contains organic solvent and water as fuel components. Organic liquid fuel such as methanol, ethanol, dimethylether, other alcohol or liquid hydrocarbon fuel including cycloparaffin may be used as the fuel component contained in the fuel 124. Hereinafter, methanol is used in the explanation below. As the oxidizer 126, air may be generally used but oxygen gas may be supplied instead.
Further, the concentration of the fuel 124 is properly selected. For example, when the fuel component is methanol, the fuel tank 1309 may contain as the fuel 124 methanol solution with the concentration ranging between more than or equal to 3 volume % and less than or equal to 50 volume %.
It is preferable that the fuel tank 1309 is formed of materials having resistance to fuel components. The fuel tank 1309, for example, can be formed of polypropylene, polyethylene, vinyl chloride or silicon.
A part of the fuel 124 is supplied to a combustion fuel passage 1307 of the combustion unit 1303 through the combustion fuel discharging exit 1315 provided in the fuel tank 1309 via the combustion fuel supplying pipe 1313. The pump 1329 is provided on the combustion fuel supplying pipe 1313, whereby the amount of the fuel 124 supplied to the combustion unit 1303 can be controlled.
A piezoelectric device such as a small-sized piezoelectric motor with very low power consumption, for example, can be used as the pump 1329. A bimorph-type piezoelectric pump, for example, may be used. In addition, a thermometer may be provided in the fuel cell 1311 and a control unit, which is not shown in
For a thermometer, those that can measure temperature as an electric signal such as a thermocouple or a thermistor are preferable. The thermometer may be placed in a combustion unit, inside a fuel cell, or on a surface of a fuel cell. Temperature of one of waste solution from a fuel cell, exhaust from a fuel cell or outside air, or a plurality of them may be used.
On a surface of the inner wall of the combustion catalyst retention unit 1305, there are holes that lead the fuel 124 from the combustion fuel supplying pipe 1313 to the inside of the combustion catalyst retention unit 1305. It is preferable that the holes are provided all over the inner wall. The holes may be more provided on the side of the oxidizer electrode 108. By this configuration, the oxidizer electrode 108 of the unit cell structure 101 can be preferentially heated. Since the oxidizer electrode 108 has the heat capacity smaller than the fuel electrode 102 and can be easily heated, when the oxidizer electrode 108 is preferentially heated, the whole unit cell structure 101 can be efficiently heated.
A metal mesh, a porous metal sheet and a foaming metal material, for example, can be used as an inner wall material of the combustion catalyst retention unit 1305. The porous metal sheet is only required to have holes passing through the sheet and let the fuel 124 go through. Various forms and thickness may be used without a further limitation. For example, a porous thin metal plate can be used. Further, a metal fiber sheet may be used. A metallic fiber sheet only need be those made of one or more metallic fibers formed in a sheet shape and a non-woven or woven cloth of metallic fiber can be used.
It is preferable that material of the inner wall has corrosion resistance to the fuel 124. The material is preferably metal that acts as a catalyst for the combustion of the fuel 124. Further, as the inner wall material, polymer molecule, ceramic or glass can be used other than metal. Specifically, a chemical fiber sheet or a glass fiber sheet, for example, may be used.
The outer wall of the combustion catalyst retention unit 1305 has air conduction holes leading the combustion oxidizer 126, which combusts the fuel 124, into the inside of the combustion catalyst retention unit 1305. It is preferable that the air conduction holes are provided all over the exposed parts of the outer wall of the combustion catalyst retaining unit 1305. By this configuration, the fuel 124 can be efficiently combusted in the whole combustion catalyst retention unit 1305. An oxidizer 126 supplied to the electrode 108, for example, can be used as a combustion oxidizer 126.
The outer wall of the combustion catalyst retention unit 1305 may be made of porous material. As the porous material, those used for the inner wall of the combustion catalyst retention unit 1305 can be used. In addition, in the fuel cell 1311 shown in
When a conductive member such as metal is used for the outer wall, the fuel electrode 102 and the oxidizer electrode 108 are insulated against each other to prevent the electrical conduction therebetween. For example, the surface of the combustion unit 1303 can be in contact with the unit cell structure 101 via an insulating sheet having the thermal conductivity.
The combustion catalyst retention unit 1305 may have the combustion catalyst on the surface of a porous support. Steel wool, foaming metal or thin metallic wire sintered body, for example, are used as the support, and they may be filled between the inner wall and the outer wall. In addition, a method for retaining the combustion catalyst on the surface of the support includes a method that the combustion catalyst metal is sprayed onto the surface of the support and then sintered or a method that the combustion catalyst metal is plated on the surface of the support.
In addition, a catalyst capable of combusting fuel components within the fuel 124 is used as the combustion catalyst. Specifically, for example, when the methanol solution is used as the fuel 124, platinum or an alloy of platinum and ruthenium is exemplified as the combustion catalyst.
The porous supports may consist of the combustion catalyst metal. By this configuration, the fuel catalyst retention unit 1305 can be simply configured.
Further, in
In addition, so long as the combustion heat can be transferred to the unit cell structure 101, the shape of the combustion unit 1303 is not limited to a cylindrical shape shown in
Referring back to
The oxidizer 126 to the oxidizer electrode 108 may be supplied by natural suction of air or forcible suction by a fan (not shown). The oxidizer may also be supplied by means of a piezoelectric pump. When the piezoelectric pump is used, the supply amount of the oxidizer 126 from the piezoelectric pump can be favorably controlled by changing an inverter, a frequency or a voltage of the inverter. When the inverter or the frequency of the inverter is changed, the number of discharges of the pump per unit time can be changed, and when the voltage is changed, a discharge amount per one discharge is changed along with the change of displacement of the piezoelectric device.
In the unit cell structure 101 shown in
The solid electrolyte membrane 114 serves as a separation of the fuel electrode 102 and the oxidizer 108, and prevents movement of hydrogen ions therebetween. As the result, it is preferable that the solid electrolyte membrane 114 has a high conductivity for hydrogen ions. In addition, it is preferable that the membrane has a chemical stability and a high mechanical strength.
As material for the solid electrolyte membrane 114, organic polymer molecules having polar groups such as strong acid groups including sulfonic groups, phosphoric groups, phosphonic groups and phosphinic groups, or weak acid groups including carboxyl groups are preferably used. The organic polymer molecules include: polymers of the aromatic class such as sulfonate poly (4-phenoxybenzoyl-1,4-phenylene) and alkyl sulfonate poly benzimidazole group; copolymer such as polystyrene sulfonate copolymer, polyvinyl sulfonate copolymer, crosslink alkylsulfonate derivative and fluorine-containing polymer composed of fluorine resin backbone and sulfonic acid; copolymer obtained by copolymerizing acrylamides such as acrylamide-2-methylpropane sulfonic acid with acrylates such as n-butylmethacrylate; sulfonate-group-containing perfluorocarbon (NAFION manufactured by Dupont and ACIPLEX manufactured by Asahi Kasei Corporation); and carboxyl-group-containing perfluorocarbon (FLEMION S MEMBRANE (manufactured by Asahi Glass Co., LTD)). When the polymer of the aromatic class such as sulfonate poly (4-phenoxy benzoyl-1,4-phenylene) and alkyl sulfonate poly benzimidazole group is selected, the permeation of organic liquid fuel can be suppressed, whereby the reduction of the cell efficiency caused by the crossover can be suppressed.
In the fuel electrode 102 and the oxidizer electrode 108, a catalyst layer 106 of the fuel electrode and a catalyst layer 112 of the oxidizer electrode including carbon particles and solid electrolyte particles and supporting catalysts may be formed on the substrate 104 and substrate 110, respectively. Platinum or an alloy of platinum and ruthenium is exemplified as the catalyst. Either the same catalysts or different catalysts may be used in the fuel electrode 102 and oxidizer electrode 108.
A water repellent treatment may be implemented on the surfaces of substrates 104 and 110. As described above, in the case where methanol is used as the fuel 124, carbon dioxide is generated in the fuel electrode 102. If the carbon dioxide generated in the fuel electrode 102 stays in the vicinity of the fuel electrode 102, the supply of the fuel 124 to the fuel electrode 102 is blocked, whereby the power generation efficiency is lowered. Here, it is preferable that the surface treatment by means of a hydrophilic coating material or a hydrophobic coating material is performed on a surface of the substrate 104. The surface treatment by means of the hydrophilic coating material improves the fluidity of the fuel 124 on the surface of the substrate 104. This enables carbon dioxide bubbles to easily move with the fuel 124. The surface treatment by means of a hydrophobic coating material reduces the attachment of moisture that causes bubbles on the surface of the substrate 104. Accordingly, the formation of bubbles can be reduced on the surface of the substrate 104.
The hydrophilic coating materials include, for example, titanium oxide and silicon oxide. On the other hand, the hydrophobic coating materials include polytetrafluoroethylene and silane.
As described above, the unit cell structure 101 is obtained. The unit cell structure 101 is disposed in contact with the combustion unit 1303 as shown in
Next, a method for using a fuel cell 1311 will be described. When the fuel cell 1311 is used over a temperature of, for example, approximately 25° C., where the startup characteristic of the fuel cell 1311 is secured, the pump 1329 is not driven. In this case, the fuel 124 in the fuel tank 1309 is supplied only to the fuel electrode 102. When the fuel cell 1311 is used at a temperature at which the startup characteristic is favorable, the fuel 124 is selectively supplied only to the fuel electrode 102 so that the waste of the fuel electrode 102 is reduced, thereby operating the fuel cell 1311 stably.
On the other hand, when the fuel cell 1311 is used at a low temperature, the pump 1329 is driven. By this configuration, part of the fuel 124 in the fuel tank 1309 is supplied to the combustion unit 1303. In addition, the oxidizer 126 is externally supplied to the combustion unit 1303. Then, the fuel 124 is combusted by the function of the combustion catalyst retained in the support in the combustion catalyst retention unit 1305 so that the combustion heat is generated. This combustion heat is transferred to the unit cell structure 101, thereby raising the temperature of the unit cell structure 101. Therefore, by a simple configuration, the startup characteristic of the unit cell structure 101 can be improved at a low temperature.
As described above, the fuel cell 1311 can exert an excellent startup characteristic even when it is used under the condition that the outside air has a low temperature. The “low temperature” described above indicates a temperature condition under which a cell voltage of the fuel cell 1311 is not sufficiently obtained. More specifically, the startup characteristic can be improved, for example, at a low temperature of 0° C. to 20° C.
The temperature described above is just an example when the fuel cell 1311 is used. It can be properly controlled whether or not the fuel 124 is supplied to the combustion unit 1303 and how much the fuel 124 is supplied. In addition, the fuel cell of this embodiment can have a control unit that controls the operation of the pump 1329 based on a temperature measured by a thermometer 1341.
The fuel cell body 1109 includes the plurality of unit cell structures 101 disposed two-dimensionally, a fuel container 811, partition plates 853, a fuel discharging pipe 1111, a combustion fuel supplying pipe 1343, a fuel discharge pipe 1337, a pump 1117, a flow control valve 1331, a connector 1123 and the thermometer 1341.
Referring back to
In addition, it is preferable that the fuel cartridge 1103 is made of material having resistance to the fuel components. For example, the fuel cartridge 1103 can be formed of polypropylene, polyethylene, vinyl chloride or silicon.
The fuel 124 is supplied to the fuel container 811 via the fuel discharging pipe 1111. The fuel 124 in the fuel container 811 flows along a plurality of partition plates 853 provided in the fuel container 811 and is sequentially supplied to the plurality of unit cell structures 101.
A pump 1117 is provided to the fuel discharging pipe 1111. In addition, the combustion fuel supplying pipe 1343 branches out on the downstream side from the pump 1117 of the fuel discharging pipe 1111, that is, on the side of the fuel container 811, whereby part of the fuel 124 is supplied to the combustion unit 1303 from the combustion fuel supplying pipe 1343. The flow control valve 1331 is provided at a point of the fuel discharging pipe 1111 where the combustion fuel supplying pipe 1343 branches off, thereby controlling the amount of the fuel 124 supplied to the combustion unit 1303.
As the pump 1117, a piezoelectric device such as a small-sized piezoelectric motor with very low power consumption can be used as the fuel cell 1311 shown in
Catalysts that combust the fuel 124 are held in the combustion unit 1303. One end of the combustion unit 1303 is connected to the combustion fuel supplying pipe 1343. The other end of the combustion unit 1303 is connected to the combustion fuel discharge pipe 1337 and remaining fuel having passed through the combustion unit 1303 is led into the fuel container 811. Further, the remaining fuel led into the fuel container 811 is, for example, input to the fuel container 811 with carbon dioxide generated by the combustion where the remaining fuel has benn vaporized by the combustion heat of the combustion unit 1303.
As described in
Further, even in the fuel cell having the plurality of unit cell structures 101, a heat transfer member can be provided between the combustion unit 1303 and the fuel container 811.
In the fuel cell according to this embodiment, fuel components that have not been used for a cell reaction in the fuel 124 having passed through the unit cell structure 101 may be supplied to the combustion unit 1303.
In addition, the fuel cell shown in
Even in this configuration, the amount of the fuel 124 supplied to the combustion unit 1303 can be also controlled by the flow control valve 1331. In addition, the remaining fuel having passed through the combustion unit 1303 is led into the unit cell structure 101 from the fuel supplying system that connects the flow control valve 1331 and the unit cell structure 101.
In a second embodiment, though not shown, a combustion unit 1303 is provided at a side opposite to a fuel electrode 102 of the fuel cell 1301 (shown in
In the fuel cell 1345 shown in
The oxidizer 126 is supplied to the oxidizer electrode 108 through the part of the surface of the substrate 110 that is not covered by the heat transfer plate 1317 and the combustion unit 1303. Further, as described in the first embodiment, the substrate 110 also serves both as a collecting electrode and a gas diffusion layer. In addition, the substrate 110 has holes to pass the oxidizer 126 required for a cell reaction.
It is preferable that material having a high thermal conductivity is used for the heat transfer plate 1317. For example, a copper plate, an aluminum plate and a titanium plate can be used. The combustion unit 1303 can be configured as shown in the first embodiment.
In a fuel cell 1345 of this embodiment, since the heat transfer plate 1317 is provided between the combustion unit 1303 and the substrate 110, combustion heat generated in the combustion unit 1303 can be efficiently transferred to the oxidizer 108 and the oxidizer 108 can be selectively or intensively heated. The oxidizer electrode 108 itself is heated by heat generated by the chemical reaction and is rapidly heated also by combustion heat generated in the combustion unit 1303. Therefore, the heat is transferred to the entire unit cell structure 101, thereby efficiently heating the whole unit cell structure 101. Therefore, the startup characteristic of the fuel cell can be further improved under a low temperature.
In the fuel cell shown in
The configuration in which the oxidizer electrode of the unit cell structure 101 is directly heated can be applied to
In the fuel cell according to the first or second embodiment, a fuel supplying system may have a fuel container retaining a fuel 124 and a high-concentration fuel container retaining a liquid fuel having a concentration higher than that of the fuel 124 supplied to a unit cell structure 101.
The low-concentration fuel and the high-concentration fuel are properly selected. For example, when the fuel component is methanol, the low-concentration fuel can contain a methanol solution having a concentration of 50 volume % or less, or water. The high-concentration fuel tank 1335 can contain a methanol solution or methanol having a concentration higher than that of the fuel 124.
The high-concentration fuel 725 in the high-concentration fuel tank 1335 is supplied to the low-concentration fuel tank 1333 by the pump 1329. And in the unit cell structure 101, the fuel 124 adjusted to a predetermined fuel component concentration at the low-concentration fuel tank 1333 is supplied to the unit cell structure 101. In
In addition, part of the high-concentration fuel 725 in the high-concentration fuel tank 1335 is supplied to a combustion unit 1303 by the pump 1329. The high-concentration fuel 725 is supplied to the combustion unit 1303, thereby heating the unit cell structure 101 more rapidly.
In addition, in the fuel cell 1349, the combustion fuel supplying pipe 1313 connects the high-concentration fuel tank 1321 and a combustion fuel passage 1307. Therefore, the high-concentration fuel 725 having a high-concentration fuel component concentration can be directly supplied from the high-concentration fuel tank 1321 to the combustion unit 1303.
In the fuel cell 1349, since the high-concentration fuel 725 can be supplied to the combustion unit 1303, the combustion reaction can be efficiently generated in the combustion unit 1303. Accordingly, the unit cell structure 101 can be more rapidly heated and the startup characteristic at a low temperature can be further improved.
In addition,
In addition, a fuel cartridge 1103 comprises a high-concentration fuel tank 1105 and a mixing tank 1107 that are detachably connected by means of a joint (not shown). The high-concentration fuel tank 1105 and mixing tank 1107 in a connected state are connected to or disconnected from a fuel cell body 1109. In an initial state, the mixing tank 1107 is filled with a low-concentration fuel having a concentration suitable for the fuel cell body 1109 and the high-concentration fuel tank 1105 is filled with the high-concentration fuel 725 having a fuel component concentration higher than the liquid in the mixing tank 1107.
In addition, the fuel having circulated the plurality unit cell structures 101 is returned to the mixing tank 1107 via a fuel recovering pipe 1113. By this configuration, the fuel 124 not consumed in the unit cell structure 101 can be recovered suitably as recovery fuel so as to be reused.
Further, the fuel cell shown in
Further, in this embodiment, fuel components that were not used for a cell reaction and have passed the unit cell structure 101 may be supplied to the combustion unit 1303.
In addition,
The amount of the high-concentration fuel 725 supplied to the combustion unit 1303 or the low-concentration fuel tank 1333 can be controlled by the flow control valve. In addition, the fuel components not used for the fuel reaction having passed through the unit cell structure 101 is supplied to the combustion unit 1303.
The fuel cell shown in
In the fuel cell shown in
In addition, in the fuel cell shown in
A fuel cell having a low-concentration fuel tank 1333 and a high-concentration fuel tank 1335 according to the third embodiment may have a mixing tank that mixes a low-concentration fuel in the low-concentration fuel tank 1333 and a high-concentration fuel 725 in the high-concentration fuel tank 1335.
In addition, part of the high-concentration fuel 725 discharged from the high-concentration fuel tank 1335 can be supplied to the combustion unit 1303 provided in contact with the unit cell structure 101. Here, a pump 1329 is provided in a supplying system of the high-concentration fuel 725, and the high-concentration fuel 725 with a predetermined amount can be supplied to the mixing tank 1339 and combustion unit 1303 by a flow control valve 1331 provided at a downstream point from the pump 1329.
By this configuration, a concentration of the fuel 124 supplied to the unit cell structure 101 can be more precisely controlled. Therefore, a cell reaction in the unit cell structure 101 can be more stably generated. In addition, since the high-concentration fuel 725 is supplied to the combustion unit 1303, the unit cell structure 101 can be rapidly heated in a short time. Accordingly, the startup characteristic of the fuel cell at the low temperature can be improved.
The fuel components can be more efficiently used by providing these recovery paths. Therefore, the startup characteristic of the fuel cell can be improved and the fuel cell can stably operate for a long period.
In the fuel cell according to the embodiment described above, a cooling water infusion path for infusing cooling water into a combustion unit 1303 can be provided. Here, the configuration of the fuel cell shown in
When the fuel cell shown in
Further, in the fuel cell having the low-concentration fuel tank 1333 and high-concentration fuel tank 1335, even though the fuel 124 is supplied to the combustion unit 1303 from the low-concentration fuel tank 1333 instead of the cooling water, the generation of the combustion heat can be suppressed. In this case, the high-concentration fuel 725 is supplied to the combustion unit 1303 at the startup and then the fuel 124 is supplied when the unit cell structure 101 is heated to some extent. By this configuration, the fuel components can be efficiently used.
In the fuel cell according the embodiments described above, an oxidizer supplying path that actively supplies the combustion oxidizer to a combustion unit 1303 may be further provided. In the description below, the configuration of the fuel cell shown in
In the fuel cell shown in
As described above, the invention has been described based on the embodiments of the present invention. These embodiments are the examples. A variety of modified examples that can be performed in combination of components or treatment processes thereof, and modified examples that are involved within the scope of the invention are understood by those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-408643 | Dec 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/18251 | 12/8/2004 | WO | 9/11/2006 |
