JP4843906B2 - Fuel cell system and equipment - Google Patents

Description

  The present invention relates to a fuel cell system and a device including the fuel cell system.

A fuel cell takes out electric energy by electrochemically reacting fuel and oxygen continuously supplied from the outside. Fuel cells have been attracting attention in recent years because environmental problems have become more prominent because they are more efficient and emit less carbon dioxide than other power generation methods.
For example, a polymer electrolyte fuel cell (PEFC) can operate at a low temperature, has a short start-up time, and can be downsized. This polymer electrolyte fuel cell is equipped with a MEA (Membrane Electrode Assembly) having a structure in which a polymer solid electrolyte membrane is sandwiched between an air side electrode and a fuel side electrode, and supplies air (oxygen) to the air side electrode. When a fuel such as methanol or reformed hydrogen is supplied to the side electrode, an electrochemical reaction occurs and electric power is generated (see, for example, Patent Document 1).

JP-A-8-162132

Among such polymer electrolyte fuel cells, for example, a direct methanol fuel cell (DMFC) is different from PEFC in that it directly supplies methanol aqueous solution as fuel to obtain electric energy. And a reformer for reforming the fuel and taking out hydrogen are not required. Therefore, direct methanol fuel cells are attracting attention as a replacement for conventional primary batteries and secondary batteries as portable power sources for portable devices such as mobile phones and laptop computers that need to be used continuously for a long time. ing.
However, in such a direct methanol fuel cell, since an aqueous methanol solution is supplied to the fuel cell as a fuel, it is necessary to store waste liquid after completion of the reaction in the fuel cell, thereby reducing the weight of the entire fuel cell. It is difficult. Moreover, since it is necessary to secure a storage space for the waste liquid, it is difficult to promote downsizing of the fuel cell.

  An object of the present invention is to provide a fuel cell system capable of promoting reduction in size and weight, and a device including the fuel cell system.

The fuel cell system of the present invention has an electrolyte membrane, an anode side reaction chamber, and a cathode side reaction chamber, supplies a fuel to the anode side reaction chamber to obtain electric energy, and is supplied to the fuel cell system. The fuel storage means for storing the fuel to be stored, the water storage means for storing the water supplied to the fuel cell system, and the communication pipe for communicating the anode side reaction chamber and the water storage means. .
According to the present invention, since the communication pipe that communicates the anode side reaction chamber and the water storage means is provided, the solution in which the reaction is completed and the fuel is consumed in the anode side reaction chamber passes through the communication pipe. It is stored in the storage means. Since this solution is supplied again to the fuel cell system from the water storage means, the water supplied to the fuel cell can be reused, and the total amount of water reserved for the reaction in the fuel cell is minimized. The As a result, the weight of the fuel cell system can be reduced and the total amount of water can be minimized, so that the water storage means can be reduced in size. Accordingly, the fuel cell system can be reduced in size accordingly. Is done.

In the present invention, a supply control means for controlling the fuel and water supply operation and a fuel concentration detection means for detecting the fuel concentration in the water storage means are provided, and the supply control means detects the fuel concentration from the fuel concentration detection means. It is desirable that the supply amount of fuel and water be controlled so that the fuel concentration in the anode reaction chamber is within a predetermined range according to the signal.
The solution that has been reacted in the fuel cell is mostly water, but may contain a small amount of unreacted fuel due to variations in the reaction efficiency of the fuel cell. In such a case, when the water after reaction is returned to the water storage means using the fuel cell for a long time, the fuel is mixed with the water in the water storage means.
According to the present invention, since the fuel concentration detection means is provided, the concentration of the fuel contained in the water in the water storage means is detected, and the supply control means is provided in the anode side reaction chamber according to the concentration detection signal. By controlling the amount of water and fuel supplied, the fuel concentration in the anode reaction chamber is controlled within a predetermined range. Therefore, even when fuel is mixed in the water storage means, fuel with a stable fuel concentration is supplied into the anode reaction chamber. Therefore, the reaction efficiency and power generation amount of the fuel cell are stabilized.

In the present invention, it is desirable that a holding means for holding water overflowing from the water storage means is provided.
In a fuel cell system, the solution discharged from the anode side reaction chamber may contain by-products generated in the anode side reaction chamber and unreacted fuel. If accumulated in the water storage means, the amount of water in the water storage means may become excessive.
According to the present invention, since the holding means is provided, the water overflowing from the water storage means is held by the holding means without leaking to the outside, so that the handleability of the fuel cell system is improved. In addition, since the holding means is provided, the water storage means is configured to have a size that can store the amount of water required to be supplied to the fuel cell, and the holding means can store the surplus that cannot be stored in the water storage means. Since it can be held, the size of the water storage means is suppressed to the minimum necessary, and the downsizing of the water storage means is promoted.

In the present invention, it is desirable that the holding means includes a gel-like absorber that absorbs and holds water.
According to this invention, since the holding means includes the gel-like absorber, the water overflowing from the water storage means is reliably held by the gel-like absorber. Thereby, water leakage from the fuel cell system is surely prevented, the handleability of the fuel cell system is improved, and the reliability of the fuel cell system is improved.

In the present invention, it is desirable that the holding means includes an absorber that absorbs and holds water and a transpiration body that evaporates at least a part of the water into the atmosphere.
According to the present invention, since the holding means is configured to include the absorber and the transpiration body, the water overflowing from the water storage means can be absorbed by the absorber, thereby causing water leakage from the fuel cell. In addition to being prevented, at least a portion of the water is evaporated to the atmosphere by the vaporizer, thus promoting the weight reduction of the fuel cell system. In this case, since a part of the water is temporarily held by the transpiration body and is evaporated to the atmosphere, excessive water is not evaporated, and even when this fuel cell system is applied to a portable device, for example. Problems such as wetting clothes are prevented.

In the present invention, the fuel is methanol, and it is desirable that a gas-liquid separation membrane for separating carbon dioxide generated after the reaction between methanol and water is provided outside the anode side reaction chamber.
According to this invention, since the gas-liquid separation membrane is provided, carbon dioxide is separated from the solution that has been reacted in the anode reaction chamber. Therefore, high-purity water is stored by the water storage means, and a more stable fuel supply is performed.
In addition, since the gas-liquid separation membrane is provided, the carbon dioxide produced in the anode reaction chamber is well removed, so that the fuel is satisfactorily filled in the anode reaction chamber, and the reaction efficiency of the fuel cell is improved. It becomes good.

A device according to the present invention includes the above-described fuel cell system.
According to this invention, since the device includes the above-described fuel cell system, the same effect as that of the above-described fuel cell system can be obtained, and the weight reduction and miniaturization of the fuel cell system can be promoted. In connection with this, the weight reduction and size reduction of an apparatus are also promoted.

  According to the fuel cell system and apparatus of the present invention, since the communication pipe is provided, the water supplied to the anode side reaction chamber can be returned to the water storage means, and the water that must be secured in the fuel cell system. As a result, it is possible to minimize the total amount of the fuel, and it is possible to reduce the weight and size of the fuel cell system and the equipment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic diagram of a fuel cell system 100 of the present embodiment. In FIG. 1, a fuel cell system 100 includes a fuel cell 1, a methanol tank (fuel storage means) 101 that stores methanol (fuel) supplied to the fuel cell 1, and methanol diluted to a predetermined concentration. Pure water tank (water storage means) 102 that stores pure water (water) supplied to the fuel cell 1, a methanol pump 103 that supplies methanol from the methanol tank 101, and pure water that is supplied from the pure water tank 102 A pure water pump 104, a mixer 105 for mixing methanol and pure water, supplying the methanol aqueous solution having a predetermined concentration to the fuel cell 1, and a supply control means 106 for controlling the supply operation of methanol and pure water. Yes.

  FIG. 2 shows a side sectional view of the fuel cell 1. The fuel cell 1 is a direct methanol fuel cell (DMFC). As shown in FIG. 2, the fuel cell 10 is housed in a case 11. In this embodiment, in order to simplify the description, a fuel cell 1 configured by a single fuel cell 10 is illustrated as shown in FIG. 2, but of course, the fuel cell 1 includes the fuel cell 10. A stack structure in which a plurality of sheets are stacked may be used.

The fuel cell 10 is disposed on the side of the anode electrode 3, the polymer solid electrolyte membrane 2 as an electrolyte membrane, the anode electrode 3 and the cathode electrode 4 integrally formed on both surfaces of the polymer solid electrolyte membrane 2. The fuel diffusion layer 5, the air diffusion layer 6 disposed on the cathode electrode 4 side, and the fuel diffusion layer 5 and the air diffusion layer 6 are provided outside the air diffusion layer 6 and generated between the anode electrode 3 and the cathode electrode 4. Current collectors 7 and 8 for taking out the electrical energy. The fuel cell 10 is housed in a case 11 and is sandwiched from both sides of the polymer solid electrolyte membrane 2 by a gasket 12. Thereby, the inside of the case 11 is sealed and separated on the anode electrode 3 side and the cathode electrode 4 side with the polymer solid electrolyte membrane 2 interposed therebetween.
That is, the region between the inner wall of the case 11 and the anode electrode 3 is liquid-tight and serves as a fuel chamber 31 as an anode-side reaction chamber to which fuel is supplied. A region between the inner wall of the case 11 and the cathode electrode 4 is an air chamber 41 as a cathode side reaction chamber to which air is supplied. Note that a methanol (CH ₃ OH) aqueous solution is supplied as the fuel.

On the anode electrode 3 side of the case 11, a fuel supply port 111 for supplying fuel to the fuel chamber 31 and a fuel discharge port 112 for discharging the fuel that has finished the reaction at the anode electrode 3 to the outside are formed. Has been. The fuel discharge port 112 is connected to a recirculation pipe 108 as a communication pipe through which the discharged solution flows. By connecting the recirculation pipe 108 to the pure water tank 102, The pure water tank 102 communicates.
A plurality of air supply ports 113 for supplying air to the air chamber 41 are formed on the cathode electrode 4 side of the case 11. The air supply port 113 has a structure in which the air supply to the air chamber 41 is a natural intake by being opened to the atmosphere. Note that. The air supply to the air chamber 41 may be a structure for forcibly supplying air to the air chamber 41 by an air pump or the like.

  A substantially rectangular anode electrode 3 and cathode electrode 4 are integrally formed on both surfaces of the polymer solid electrolyte membrane 2 within a predetermined range separated by a predetermined width from the outer edge. The solid polymer electrolyte membrane 2 is formed by impregnating a porous solid portion of a stretched porous polytetrafluoroethylene (PTFE) film with a solid polymer electrolyte resin composed of a proton conductive polymer. It is configured. As the polymer solid electrolyte resin, for example, a perfluorosulfonic acid polymer such as Nafion (trademark of DuPont), a fluorine polymer, a hydrocarbon polymer, or the like can be employed. In some cases, a catalyst such as platinum, carbon powder, various ceramic powders and the like may be added to the solid polymer electrolyte resin as long as electronic conductivity does not occur.

  In addition, a stretched porous polytetrafluoroethylene (PTFE) film is obtained by stretching a porous PTFE mass to obtain a microscopic connection between a large number of micronodules and the micronodules three-dimensionally connected to each other. It is a porous PTFE film having a structure composed of fibers, and a large number of holes penetrating in the thickness direction are formed in this film. In the present embodiment, the stretched porous PTFE film has a thickness of 1 to 100 μm, preferably 3 to 30 μm, a pore diameter of 0.05 to 5 μm, preferably 0.5 to 2 μm, and a porosity of 60% to 98. %, Preferably 80 to 92%. If the film thickness is too thin, short circuits and gas leaks (cross leaks) are likely to occur, and if it is too thick, the electrical resistance increases. If the pore size is too small, impregnation of the polymer solid electrolyte resin becomes difficult, and if it is too large, the holding power of the polymer solid electrolyte resin becomes weak and the reinforcing effect becomes weak. If the porosity is too small, the resistance of the polymer solid electrolyte membrane is increased. If it is too large, the strength of PTFE itself is generally weakened and a reinforcing effect cannot be obtained.

The anode electrode 3 and the cathode electrode 4 are composed of a carbon catalyst electrode film carrying a catalyst for decomposing methanol. Here, platinum etc. are employable as a catalyst, for example. On the anode electrode 3 side, in order to prevent poisoning of carbon monoxide CO, which is an intermediate product generated by the reaction between methanol and the catalyst, at least the catalyst on the anode electrode 3 side includes an alloy of platinum and ruthenium, etc. Is more preferable.
Here, the polymer solid electrolyte membrane 2, the anode electrode 3, and the cathode electrode 4 are integrally formed to form a membrane electrode assembly 20.
The fuel diffusion layer 5 and the air diffusion layer 6 are porous membranes made of mesh metal foam (for example, steel wool) and diffuse the supplied fuel and oxygen to the anode electrode 3 and the cathode electrode 4, respectively. The fuel diffusion layer 5 and the air diffusion layer 6 may be made of aluminum, stainless steel or the like, respectively, a porous metal material such as sponge titanium, carbon paper supported on carbon, carbon cloth, or the like. It may be.
Further, lead wires (not shown) are connected to the current collectors 7 and 8, respectively, and are connected to an external load.

The methanol tank 101 and the pure water tank 102 include valves 101A and 102A that can open and close the flow path to the fuel chamber 31. These valves 101A and 102A are electrically connected to the supply control means 106, can be individually opened and closed by commands from the supply control means 106, and their opening degrees can also be adjusted. The methanol tank 101 and the pure water tank 102 are preferably configured so that the interior of the integral case is partitioned. For example, the methanol tank 101 and the pure water tank 102 can be easily and simultaneously formed in a so-called cartridge system. A replaceable structure is desirable.
FIG. 3 shows a schematic diagram of the methanol tank 101 and the pure water tank 102. In FIG. 3, the methanol tank 101 and the pure water tank 102 are integrally formed, and pipes communicating with the methanol pump 103 and the pure water pump 104 are connected to each other. Further, a recirculation pipe 108 communicating with the fuel chamber 31 is connected to the pure water tank 102. By this recirculation pipe 108, the solution that has been reacted in the fuel chamber 31 is stored in the pure water tank 102. Further, as shown in FIG. 1 described above, the pure water tank 102 is provided with a methanol sensor 107 as fuel concentration detection means for detecting the concentration of methanol contained in the water in the pure water tank 102. When the solution from the fuel chamber 31 is returned to the pure water tank 102 by the recirculation pipe 108, a trace amount of methanol contained in the solution accumulates over a long period of use, and the water in the pure water tank 102 contains a certain amount of methanol. It may be a methanol aqueous solution. Accordingly, the methanol sensor 107 detects the methanol concentration in the pure water tank 102 and outputs a methanol concentration detection signal (fuel concentration detection signal) to the supply control means 106.

The pure water tank 102 is formed with a capacity capable of storing an amount of water necessary for the reaction in the fuel cell 1 with respect to the amount of methanol in the methanol tank 101. The pure water tank 102 is provided with an absorption pad 9 as a holding means for absorbing and holding water overflowing from the pure water tank 102.
The absorbent pad 9 is integrally configured by laminating a transpiration layer 91 as a transpiration body and an absorption layer 92 as an absorber. The transpiration layer 91 is disposed adjacent to the pure water tank 102, that is, in contact with one side surface of the pure water tank 102, and is made of an arbitrary material having a moisture retention capability. The transpiration layer 91 is provided with a pipe 93 communicating with the pure water tank 102. When excess water overflowing from the pure water tank 102 flows into the transpiration layer 91 through the pipe 93, the transpiration layer 91 is provided. Keeps this water temporarily inside and transcribes it from the surface to the atmosphere. Therefore, it is desirable that the transpiration layer 91 is disposed so as to face the atmosphere. For example, when the entire fuel cell system 100 is accommodated in the case, the case is provided with a plurality of vents and the transpiration layer 91 is ventilated. What is necessary is just to arrange | position facing a mouth. Further, the transpiration layer 91 is desirably configured to have a large surface area in order to increase the transpiration efficiency. For example, the transpiration layer 91 has a plate shape (sheet shape) having a larger area than the side surface of the pure water tank 102 with which the transpiration layer 91 abuts. ), The transpiration layer 91 protrudes around the pure water tank 102 to increase the transpiration area.

  The absorption layer 92 is a gel-like absorber composed of, for example, a polymer absorber and absorbs moisture that cannot be absorbed and evaporated by the evaporation layer 91 and holds it inside. The dimensions of the absorption layer 92 are preferably formed in a plate shape (sheet shape) having the same area as the transpiration layer 91, and the amount of solution recovered from the fuel chamber 31, the amount of water that can be transpiration in the transpiration layer 91, and the like It is desirable to set as appropriate in consideration.

The methanol pump 103 and the pure water pump 104 are connected to the mixer 105, and send predetermined amounts of methanol and pure water from the methanol tank 101 and the pure water tank 102 to the mixer 105, respectively. These pumps 103, 104 are electrically connected to the supply control means 106, and ON / OFF of the pumps 103, 104 is controlled by a liquid feed command signal from the supply control means 106.
The mixer 105 is connected to the fuel supply port 111 and mixes methanol from the methanol tank 101 and pure water from the pure water tank 102 based on a mixing command signal from the supply control means 106, and the methanol is pure. This is a mixing means for preparing an aqueous methanol solution uniformly dispersed in water. When only methanol or pure water is supplied to the fuel chamber 31, the mixer 105 only mixes one type of liquid, and the liquid passes substantially without performing its function. Become.
Here, in this embodiment, a methanol supply means is configured by including the methanol tank 101, the valve 101A, and the methanol pump 103, and a water supply means is provided by having the pure water tank 102, the valve 102A, and the pure water pump 104. Is configured.

The supply control means 106 controls the supply amounts of methanol and water so as to maintain the concentration of the aqueous methanol solution in the fuel chamber 31 within a predetermined range set in advance. That is, the supply control means 106 adjusts the opening degree of the valves 101A, 102A to supply a methanol aqueous solution having a predetermined concentration, and opens the valves 101A, 102A based on the methanol concentration detection signal from the methanol sensor 107. The concentration of the aqueous methanol solution supplied to the fuel chamber 31 is controlled within a predetermined concentration range.
Specifically, the supply control unit 106 includes a calculation unit (not shown) that calculates the opening degree of the valve 101A based on a methanol concentration detection signal from the methanol sensor 107. For example, based on a methanol concentration detection signal, the calculation means calculates an additional amount of methanol necessary to make the water in the pure water tank 102 into a methanol solution having a predetermined concentration, and calculates the opening degree of the valve 101A. An expression is stored. The supply control means 106 controls the opening degree of the valve 101A based on the calculation result of the calculation means.
Here, the predetermined range of the concentration of the aqueous methanol solution in the fuel chamber 31 provides good reaction efficiency between methanol and the catalyst in the fuel chamber 31 and also prevents crossover of the polymer solid electrolyte membrane 2 well. It is preferably set in a range, and is set as appropriate in consideration of the capacity of the fuel cell 1, the material of the polymer solid electrolyte membrane 2, the performance, etc., for example, in the range of 3% to 5% or 1 mol / l to 8 mol / l. Set within.

Next, the operation of the fuel cell system 100 will be described.
First, when the fuel cell system 100 is activated, the methanol aqueous solution is filled in the fuel chamber 31 by an initial methanol aqueous solution supply command output from the supply control means 106. In response to this command signal, the valves 101A and 102A are opened, and methanol and pure water are fed, respectively. At this time, the opening degree of the valves 101A and 102A is set in advance so that the concentration of the methanol aqueous solution is within a predetermined range. Methanol and pure water are sent to the mixer 105 by the methanol pump 103 and the pure water pump 104, mixed uniformly by the mixer 105, and then supplied to the fuel chamber 31.

In the fuel chamber 31, the methanol aqueous solution causes an oxidation reaction of the following formula (1) by the catalyst of the anode electrode 3, and this reaction generates carbon dioxide CO ₂ , protons H ^+, and electrons e ⁻ .
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
Proton H ⁺ passes through the polymer solid electrolyte membrane 2 and moves to the cathode electrode 4 side, whereby a voltage is generated across the current collectors 7 and 8. When the proton H ⁺ reaches the cathode electrode 4 side, the proton H ⁺ and the electron e ⁻ that has reached the cathode electrode 4 after working through an external load are air in the air chamber 41 by the catalyst of the cathode electrode 4. It reacts with the oxygen O ₂ in it to produce a reduction reaction of formula (2).
3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O (2)
The solution that has been reacted on the anode electrode 3 side is stored in the pure water tank 102 through the recirculation pipe 108. This solution is mixed with pure water in the pure water tank 102 and fed again by the pure water pump 104 to be used for diluting methanol into a methanol aqueous solution having a predetermined concentration. Moreover, the water produced | generated by the cathode electrode 4 side is open | released by the air through the air supply port 113 in the state of water vapor | steam.

The solution stored in the pure water tank 102 through the recirculation pipe 108 may contain a small amount of methanol that has not reacted in the fuel chamber 31. In this case, when the fuel cell system 100 is used for a long time, methanol is accumulated in the pure water tank 102, and the water in the pure water tank 102 becomes a methanol aqueous solution having a low concentration.
Therefore, the supply control unit 106 monitors the methanol concentration detection signal from the methanol sensor 107, and the calculation unit calculates the opening degree of the valve 101A based on the methanol concentration detection signal. The supply control means 106 adjusts and controls the opening degree of the valve 101A as needed based on this calculation result.

The solution recovered from the fuel chamber 31 through the recirculation pipe 108 into the pure water tank 102 includes unreacted methanol and other products generated by the reaction of methanol and water, such as carbon dioxide, formic acid, formaldehyde, and the like. Since by-products such as carbon oxide are contained, the water in the pure water tank 102 may increase and become excessive as the fuel cell system 100 is used. When the excess water overflows from the pure water tank 102, the excess water is supplied to the transpiration layer 91 of the absorption pad 9 through the pipe 93. Water from the pipe 93 is diffused over the entire surface of the transpiration layer 91, temporarily held in the transpiration layer 91, and transpiration from the surface of the transpiration layer 91 into the atmosphere by a certain amount.
Further, a further excessive amount of water that cannot be held and evaporated in the transpiration layer 91 moves from the transpiration layer 91 to the absorption layer 92 and is absorbed and held in the absorption layer 92.
When the methanol in the methanol tank 101 runs out, methanol and pure water may be added to the methanol tank 101 and the pure water tank 102, respectively, or the methanol tank 101 and the pure water tank 102 may be replaced.
The absorption pad 9 may be replaced when a predetermined amount or more of water is absorbed. When the absorption pad 9 is provided integrally with the methanol tank 101 and the pure water tank 102, the methanol tank 101 and the pure water are used. When the tank 102 is replaced, the absorbent pad 9 may be replaced. At this time, the absorption capacity and the transpiration capacity of the absorption pad 9 are set in consideration of the amount of water generated when the methanol in the methanol tank 101 reacts in the fuel cell 1 according to the amount of methanol in the methanol tank 101. It is desirable that

According to this embodiment, the following effects can be obtained.
(1) Since the fuel chamber 31 and the pure water tank 102 are communicated with each other by the recirculation pipe 108, the solution that has finished the reaction in the fuel chamber 31 can be stored in the pure water tank 102. Therefore, the water supplied to the fuel chamber 31 can be reused for dilution of methanol, so that the water stored in the pure water tank 102 in advance can be reduced, and downsizing of the pure water tank 102 can be promoted. Therefore, the fuel cell system 100 can be reduced in size and weight.

 (2) Since the supply control means 106 controls the opening amount of the valve 101A based on the methanol concentration detection signal from the methanol sensor 107 and adjusts the supply amount of methanol, the concentration of the aqueous methanol solution in the fuel chamber 31 is set to a predetermined value. Can be controlled within range. Therefore, the reaction efficiency in the fuel chamber 31 can be stabilized, and a stable power generation amount can be obtained from the fuel cell 1.

 (3) Since the excess water overflowing from the pure water tank 102 is absorbed by the absorption pad 9, the pure water tank 102 can store only the necessary water to be used in the fuel cell 1. Capacity can be minimized. Accordingly, it is possible to promote the miniaturization of the pure water tank 102 and the miniaturization of the fuel cell system 100.

(4) Since the absorption pad 9 includes the transpiration layer 91, a part of the excess water overflowing from the pure water tank 102 can be transpiration to the atmosphere. Therefore, it is not necessary to hold the entire amount of the solution collected from the fuel chamber 31 in the fuel cell system 100, and the weight reduction of the fuel cell system 100 can be promoted. In this case, the transpiration layer 91 temporarily holds water and transcribes a certain amount of the transpiration, so that the transpiration amount can be adjusted, and problems such as wetting the outside of the fuel cell system 100 can be favorably avoided.
Moreover, since the absorption pad 9 is provided with the absorption layer 92 comprised with a gel-like absorber, the moisture which cannot be hold | maintained by the evaporating layer 91 and cannot be evaporated can be absorbed and hold | maintained by the absorption layer 92. Therefore, the absorption of moisture by the absorption pad 9 can be more reliably performed, and the transpiration amount of the transpiration layer 91 can be maintained at an appropriate amount without being excessive.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
The supply control means is not limited to one provided with a calculation means for calculating the opening degree of the valve 101A based on the methanol concentration detection signal. For example, an appropriate fuel supply amount for the fuel concentration detection signal (the valve 101A in the above embodiment). May be provided with a storage means for storing the degree of opening) as a table or a map. In this case, the supply control means may read the fuel supply amount (valve opening) corresponding to the detected fuel concentration detection signal with a table or the like stored in the storage means and control the fuel supply amount. . In this case, since the fuel supply amount with respect to the fuel concentration detection signal is stored in advance in the storage means, it is not necessary to perform calculation or the like by the supply control means, the control is simplified, and labor saving of the fuel cell system 100 is achieved. Can promote.
Further, the concentration detection by the fuel concentration detection means is not limited to being performed continuously, but may be detected, for example, every predetermined time. With this configuration, it is possible to save electric power necessary for detecting the fuel concentration, so that labor saving can be promoted.
The fuel concentration detection means is not necessarily provided. For example, when almost all of the fuel supplied to the anode side reaction chamber is used for the reaction, the solution discharged from the anode side reaction chamber contains no fuel. Is hardly contained, so that the fuel is not excessively accumulated in the water storage means.

When the holding means is configured by laminating a transpiration body and an absorber, the transpiration body is not limited to the one adjacent to or in contact with the water storage means. For example, the absorption body is adjacent to the water storage means, It may be touched. In this case, a pipe that communicates from the water storage means to the opposite transpiration body with the absorber interposed therebetween may be provided so that water overflowing from the water storage means is supplied to the transpiration body. Even in this case, if the transpiration body is disposed opposite to the atmosphere side, the transpiration of moisture from the transpiration body can be promoted. Further, since the transpiration body is not sandwiched between the water storage means and the absorber, the facing area to the atmosphere is increased, and the transpiration efficiency is improved.
The holding means may not necessarily be provided with a transpiration body. For example, the holding means may be provided with only an absorber, and the absorber may absorb and hold the entire amount of water overflowing from the water storage means. Good.
The holding means is not necessarily required. For example, if the storage capacity of the water storage means is set in consideration of the amount of the solution recovered from the anode side reaction chamber, the entire amount of the solution passes through the communication pipe to the water storage means. Since it is stored and does not overflow, it is not necessary to provide holding means.

  When the holding means includes a transpiration body, a heating means for heating the transpiration body may be provided to promote the transpiration of water from the transpiration body. In this case, as the heating means, for example, a heating element provided in the vicinity of the vaporizer may be used, or the amount of heat generated in the fuel cell may be used within a range in which the reaction efficiency of the fuel cell can be satisfactorily maintained. Moreover, as a transpiration | evaporation acceleration | stimulation means which promotes transpiration | evaporation of a transpiration | evaporation body, you may provide a ventilation means other than what provides a heating means, for example.

When the fuel is methanol, a gas-liquid separation membrane for separating carbon dioxide generated after the reaction between methanol and water may be provided outside the anode side reaction chamber. In this case, carbon dioxide produced by the reaction in the anode side reaction chamber is separated by the gas-liquid separation membrane and discharged to the outside, so that the solution from which carbon dioxide has been removed flows through the communication pipe. Therefore, gas is not mixed in the solution stored in the water storage means, water with higher purity can be returned, and the aqueous fuel solution mixed with gas can be well prevented from being supplied to the anode reaction chamber. .
In addition, since the carbon dioxide in the anode side reaction chamber is removed by the gas-liquid separation membrane, the fuel comes into good contact with the catalyst in the anode side reaction chamber, so that the reaction efficiency of the fuel cell can be improved.

The water stored in the water storage means by the communication pipe is used for diluting the fuel of the fuel cell to create an aqueous solution, for example, sending a small amount of water together with air to the cathode reaction chamber to bring the electrolyte membrane to an appropriate humidity. It may be used to hold.
Alternatively, the water stored in the water storage means by the communication pipe is supplied to the reformer, for example, in the case where the fuel cell system has a reformer in addition to the use of preparing an aqueous solution of the fuel supplied to the fuel cell. You may use for the use which produces the aqueous solution of the fuel which is.
The fuel is not limited to methanol, and any material can be adopted. In addition, when the fuel cell system includes a reformer, any material such as an organic fuel such as decalin or a borohydride fuel such as sodium borohydride is used as the fuel in addition to an alcohol fuel such as methanol. Has been.
Since the fuel cell system of the present invention can promote weight reduction and downsizing, it can be applied to portable devices such as mobile phones and notebook computers, cars, and other arbitrary devices.

The best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

1 is a schematic diagram showing a fuel cell system according to an embodiment of the present invention. The side sectional view of a fuel cell. The perspective view which shows a water storage means and a holding means.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Polymer solid electrolyte membrane (electrolyte membrane), 3 ... Anode electrode, 4 ... Cathode electrode, 9 ... Absorption pad (holding means), 31 ... Fuel chamber (anode side reaction chamber), 41 ... Air Chamber (cathode side reaction chamber), 91 ... transpiration layer (vaporizer), 92 ... absorption layer (absorber), 100 ... fuel cell system, 101 ... methanol tank (fuel storage means), 102 ... pure water tank (water storage) Means), 106 ... Supply control means, 107 ... Methanol sensor (fuel concentration detection means), 108 ... Recirculation piping (communication piping).

Claims (5)

A fuel cell having an electrolyte membrane, an anode side reaction chamber, and a cathode side reaction chamber, supplying fuel to the anode side reaction chamber to obtain electric energy;
Fuel storage means for storing fuel supplied to the fuel cell ;
Water storage means for storing water supplied to the fuel cell and used for diluting the fuel concentration in the anode reaction chamber within a predetermined range ;
A communication pipe that communicates the anode-side reaction chamber and the water storage means, and distributes the solution that has been reacted in the anode-side reaction chamber to the water storage means;
Holding means for holding water overflowing from the water storage means;
Fuel concentration detection means for detecting the fuel concentration in the water storage means;
And in response to said fuel concentration detection signal from the fuel concentration detection means, supply control means for the fuel concentration in the anode reaction chamber to control the supply amount of the fuel and the water to be within a predetermined range,
Fuel cell system comprising: a.   The fuel cell system according to claim 1, wherein the holding means includes a gel-like absorber that absorbs and holds water.   3. The fuel cell system according to claim 1, wherein the holding unit includes an absorber that absorbs and holds water, and a vaporizer that evaporates at least a part of the water into the atmosphere.   The fuel is methanol, and a gas-liquid separation membrane for separating carbon dioxide generated after the reaction between the methanol and water is provided outside the anode side reaction chamber. The fuel cell system according to claim 3.   An apparatus comprising the fuel cell system according to any one of claims 1 to 4.

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