JP2015210968A - Microbial fuel system, power storage method of microbial fuel cell, and power storage circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a microbial fuel system in which an output of a microbial fuel cell is adjusted to a predetermined voltage in order to appropriately perform power generation; a power storage method of a microbial fuel cell; and a power storage circuit.SOLUTION: A microbial fuel system 100 according to the present invention includes a constant voltage circuit 300 provided between an anode and a cathode of a microbial fuel cell 200 and configured to adjust an output of the microbial fuel cell 200 to a predetermined voltage. The microbial fuel system 100 further includes a capacitor 500 for storing electrical charges from the microbial fuel cell 200 and a back-flow preventive circuit 400 provided between the microbial fuel cell 200 and the capacitor 500.

Description

  The present invention relates to a microbial fuel system, a microbial fuel cell storage method, and a storage circuit.

  In recent years, microbial fuel cells have been developed. For example, in Non-Patent Document 1, a large load resistance is used according to the behavior of the microbial fuel cell, or a small load resistance is used according to the behavior of the microbial fuel cell. Is disclosed.

Morio Miyahara, Kazuhito Hashimoto, and Kazuya Watanabe Use of cassette-electrode microbial fuel cell for wastewater treatment

  Specifically, as shown in FIG. 2A of Non-Patent Document 1, each resistance having a resistance value of 10 K ohms, a resistance value of 1 K ohms, a resistance value of 100 ohms, a resistance value of 20 ohms, and a resistance value of 10 ohms is applied to the microbial fuel cell They are replaced according to their behavior.

  Thus, in Non-Patent Document 1, it is necessary to constantly monitor the voltage of the microbial fuel cell to monitor the state of the microbial fuel cell. And when it becomes a predetermined electric current value, it is necessary to change a resistance value with a human hand.

Also, if the resistance value is changed when the resistance value change period is exceeded or not reached, the growth of power generation bacteria (microorganisms) constituting the microbial fuel cell is impaired, and the function as a microbial fuel cell is not fulfilled. There is a problem of becoming.
That is, when functioning as a microbial fuel cell, it takes time to perform the function as a battery, and it takes time and effort to function, making it impractical.

  An object of the present invention is to provide a microbial fuel system, a microbial fuel cell storage method, and a storage circuit that adjust the output of a microbial fuel cell to a predetermined voltage in order to appropriately generate power.

(1)
A microbial fuel system according to one aspect includes a microbial fuel cell and a constant voltage unit that is provided between an anode and a cathode of the microbial fuel cell and adjusts the output of the microbial fuel cell to a predetermined voltage.

In this case, the output of the microbial fuel cell can be adjusted to a predetermined voltage by the constant voltage unit. As a result, the electron transfer of microorganisms can always be in an optimum state, and the growth state of microorganisms in the microbial fuel cell can be maintained well. In particular, for the growth of microorganisms, it is preferable to keep the voltage constant. Therefore, the microbial fuel cell can generate power efficiently by the constant voltage unit.
Here, the predetermined voltage is in the range of 0 to 1 volt, particularly in the range of 0.5 to 0.7 volt, and is in the vicinity of 0.6 volt.

(2)
A microbial fuel system according to a second aspect of the present invention is the microbial fuel system according to one aspect, wherein a capacitor for storing electric charges from the microbial fuel cell and a backflow prevention unit between the microbial fuel cell and the capacitor may be provided.

  In this case, since the backflow prevention unit is provided between the microbial fuel cell and the capacitor, the current stored in the capacitor can be prevented from flowing back to the microbial fuel cell. As a result, it is possible to prevent the charge generated by the microorganisms from being wasted.

(3)
A microbial fuel system according to a third aspect is the microbial fuel system according to one aspect or the second aspect, wherein the constant voltage unit may include a rectifying element.

In this case, since the constant voltage part of the microbial fuel system includes a rectifying element, it can be set to a constant voltage using the characteristics of the element itself. That is, a constant voltage can be realized by using the forward voltage characteristics.
Here, the rectifying element may be either a diode or a Schottky barrier diode or a combination of both.

(4)
The microbial fuel system according to a fourth aspect of the present invention is the microbial fuel system according to the second or third aspect of the present invention, wherein the constant voltage unit may be arranged with one or more stages of Schottky barrier diodes.

In this case, a predetermined voltage can be adjusted by arranging one or more Schottky barrier diodes. For example, 0.3 volts can be realized by arranging one stage of a Schottky barrier diode. In addition, 0.6 volt can be realized by arranging two stages, and 0.9 volt can be realized by arranging three stages.
In the microbial fuel system, it is particularly preferable that the voltage is 0.6 volts in a two-stage arrangement.

(5)
The microbial fuel system according to a fifth aspect of the present invention is the microbial fuel system according to the second to fourth aspects of the present invention, wherein the backflow prevention unit may include a PNP transistor element.

In this case, since the backflow prevention unit includes the PNP transistor element, backflow of current can be prevented up to 0.6 volts due to the characteristics of the base voltage. As a result, current can be prevented from flowing to the microbial fuel cell side.
In general, a backflow prevention unit can be formed by a diode. However, since the amount of power generated from the microbial fuel cell is 0.6 volts, a voltage drop of 50% or more is generated by the diode, which is not preferable. .
Therefore, by using the PNP transistor element, it is possible to appropriately prevent the reverse flow of the voltage of 0.6 volts accumulated in the capacitor.

(6)
The microbial fuel system according to a sixth aspect of the present invention is the microbial fuel system according to the first to fifth aspects of the present invention, further comprising a load section connected in parallel with the capacitor, wherein the load section is at least one of a booster section and a communication section. May be included.

  In this case, since the load unit includes at least one of the boosting unit and the communication unit, the power from the microbial fuel cell can be boosted by the boosting unit. Moreover, the electric power by a microbial fuel cell can be used for communication of a communication part.

(7)
The method for storing a microbial fuel cell according to another aspect may include a constant voltage step that is provided between the anode and the cathode of the microbial fuel cell and adjusts the output of the microbial fuel cell to a predetermined voltage.

In this case, the output of the microbial fuel cell can be adjusted to a predetermined voltage by the constant voltage process. As a result, the growth state of microorganisms in the microbial fuel cell can be favorably maintained. Therefore, the amount of power generation can be increased efficiently.
Here, the predetermined voltage is in the range of 0 to 1 volt, particularly in the range of 0.5 to 0.7 volt, and is in the vicinity of 0.6 volt.

(8)
According to an eighth aspect of the present invention, there is provided a method for storing a microbial fuel cell according to another aspect, comprising: a storage step for storing a charge from a microbial fuel cell; and a storage step from the microbial fuel cell to a storage step. A backflow prevention step for preventing backflow may be provided.

  In this case, it is possible to prevent the current stored in the capacitor from flowing back to the microbial fuel cell by the backflow prevention step. As a result, it is possible to prevent the charge generated by the microorganisms from being wasted.

(9)
A power storage circuit according to still another aspect is a power storage circuit used in an environment of 1 volt or less, and includes a constant voltage unit that adjusts a predetermined voltage by a rectifying element.

  In this case, since it is in an environment of 1 volt or less, it can be adjusted to a predetermined voltage by the rectifying element of the constant voltage unit. The predetermined voltage is in the range of 0 to 1 volt, particularly in the range of 0.5 to 0.7 volt, and is in the vicinity of 0.6 volt.

  The rectifying element is connected in parallel with the capacitor for storing electricity, the anode of the rectifying element is connected to the plus side, and the cathode side of the rectifying element is connected to the minus side. Further, when the rectifying element is a Schottky barrier diode, a series multi-stage connection configuration is employed.

(10)
In a power storage circuit according to a tenth aspect of the present invention, in the power storage circuit according to still another aspect, when charge is stored from the power storage unit to the power storage capacitor, the backflow prevention unit may be formed by a circuit including a PNP transistor.

In this case, since the backflow prevention unit includes the PNP type transistor element, it is possible to prevent backflow of a current of 0.6 volts due to the base voltage. As a result, it is possible to prevent the current from flowing back to the power generation side.
In particular, when storing weak electric power, a problem of a loss ratio of electric power stored due to a voltage drop occurs in a general diode backflow prevention circuit.
Therefore, the PNP transistor element can prevent backflow and reduce the accumulated power loss, thereby efficiently storing power.

  In particular, the emitter terminal of the PNP transistor element is connected to the cathode on the power generation unit side, the base terminal is connected to the anode on the power generation unit side, and the collector terminal is connected to the positive side of the capacitor. Further, a resistance element may be provided between the emitter base.

It is a schematic diagram which shows an example of the microbial fuel system concerning this Embodiment. It is a schematic diagram which shows an example of a constant voltage circuit. It is a schematic diagram which shows an example of a backflow prevention circuit. It is a schematic diagram which shows an example of the result of a microbial fuel system. It is a schematic diagram which shows an example of the result of a microbial fuel system. It is a schematic diagram which shows an example of the result of the conventional microbial fuel system. It is a schematic diagram which shows an example of the result of the conventional microbial fuel system. It is a schematic diagram which shows an example of the result of the conventional microbial fuel system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<Microbial fuel system>
FIG. 1 is a schematic diagram showing an example of a microbial fuel system 100 according to the present embodiment.

  As shown in FIG. 1, the microbial fuel system 100 includes a microbial fuel cell 200, a constant voltage circuit 300, a backflow prevention circuit 400, a capacitor 500, and a load 600.

As shown in FIG. 1, a constant voltage circuit 300 is provided between an anode (negative electrode) and a cathode (positive electrode) of a microbial fuel cell 200 described later.
A capacitor 500 is provided in parallel with the constant voltage circuit 300.
The backflow prevention circuit 400 is provided between the microbial fuel cell 200 and the capacitor 500.

  The load 600 is provided in parallel with the capacitor 500 on the capacitor 500 side of the backflow prevention circuit 400.

<Microbial fuel cell 200>
Next, an example of the microbial fuel cell 200 will be described. The microbial fuel cell 200 has an anode (negative electrode), a cathode (positive electrode), and an ion permeable membrane sandwiched between the anode and the cathode, and a liquid containing an organic substance by the action of microorganisms. It is possible to recover electrical energy directly from
Hereinafter, the outline of the microbial fuel cell 200 will be described with respect to the anode, the cathode, the ion permeable membrane, and the microorganism.

<Anode (negative electrode)>
The anode (negative electrode) is made of a material capable of supporting microorganisms and allowing a liquid containing an organic substance to pass therethrough. The anode (negative electrode) is a working electrode. Microorganisms may or may not be supported on the anode (negative electrode).

Further, when microorganisms are not supported on the anode (negative electrode), the microorganisms are supported on the anode (negative electrode) before or during use of the membrane-electrode assembly. By attaching microorganisms to the anode (negative electrode), hydrogen ions (H ⁺ ) and electrons (e ⁻ ) can be generated from organic substances by the microorganisms. If necessary, a mediator (electron carrier) may be supported on the anode (negative electrode), and a mediator (electron carrier) may be added to the microorganism.

  The anode (negative electrode) preferably has pores and is preferably porous. The material of the anode (negative electrode) is not particularly limited as long as it is a conductive material capable of supporting microorganisms. Examples of the conductive material include carbon fibers or various conductive metals such as titanium. Examples of the form of the anode (negative electrode) include a net, a woven fabric, a non-woven fabric, a cloth, and a felt. The anode (negative electrode) may be surface-treated in order to increase the specific surface area.

<Cathode (Positive electrode)>
Further, the cathode (positive electrode) is a counter electrode and can contact air.
The material of the cathode (positive electrode) is not particularly limited as long as it is a conductive material. Examples of the material for the positive electrode (cathode) include the same materials as the materials for the anode (negative electrode). Examples of the form of the cathode (positive electrode) include those exemplified as the form of the anode (negative electrode). The cathode (positive electrode) may be coated with a catalyst such as platinum.

<Ion permeable membrane>
The ion permeable membrane can transmit hydrogen ions (H ⁺ ) generated from the anode (negative electrode), and is preferably an electrolyte membrane. The ion permeable membrane preferably does not transmit air.
In this case, air does not reach the anode (negative electrode) through the ion permeable membrane from the cathode (positive electrode) side, and contact between the anode (negative electrode) and air is suppressed. The material of the ion permeable membrane is not particularly limited, but a fluororesin ion exchange membrane (cation exchange membrane) having a sulfonic acid group is preferably used. Other ion permeable membranes may be used.
Further, as a cheaper ion permeable membrane, a fluororesin ion exchange membrane in which only the main chain portion is fluorinated or an aromatic hydrocarbon membrane can be used. When the organic substance and the cathode (positive electrode) are separated by a cation exchange membrane, hydrogen ions generated by the reaction at the anode (negative electrode) are transferred to the cathode (positive electrode) through the cation exchange membrane. Effectively supplied and used effectively for oxygen reduction at the cathode (positive electrode).

<Microorganism>
Examples of the microorganism according to the present embodiment include an anaerobic microorganism and an aerobic microorganism, but an anaerobic microorganism is preferable. Anaerobic microorganisms can grow under anaerobic conditions. As the microorganism, a microorganism that does not terminate the electron transfer system in the cell membrane of the microorganism is desirable, and a microorganism that easily captures electrons outside the cell membrane at the anode (negative electrode) and catalyzes electron transfer to the anode (negative electrode) is used. It is more desirable. As the microorganism, sulfur S (0) reducing bacteria, trivalent iron Fe (III) reducing bacteria, manganese dioxide MnO ₂ reducing bacteria, dechlorinating bacteria, and the like are preferably used.

  In addition, it is desirable to supply a medium suitable for the growth of these microorganisms into the microorganism reaction chamber at the start of use of the microbial fuel cell. Furthermore, it is more desirable to promote the growth of these microorganisms at the anode (negative electrode) by keeping the potential of the anode (negative electrode) high. Examples of a method for culturing these microorganisms (groups) in a preculture or in a microorganism reaction chamber include a medium containing slurry-like sulfur, trivalent iron, manganese dioxide and the like as an electron acceptor.

<Constant voltage circuit>
Next, the constant voltage circuit 300 will be described. FIG. 2 is a schematic diagram illustrating an example of the constant voltage circuit 300.

A constant voltage circuit 300 shown in FIG. 2 includes a resistor 310 and a Schottky barrier diode 320. In the present embodiment, the resistor 310 may be omitted, but the circuit shown in FIG. 2 is configured to detect the current generated by the microbial fuel cell, and is, for example, 0.33 ohm (Ω) . A resistance value that causes a voltage drop of about several mV with respect to the flowing current may be selected, and may be, for example, 0.1 ohm (Ω) depending on the amount of power generation.
The constant voltage circuit 300 is formed by connecting a resistor 310 and a Schottky barrier diode 320 in series.

  The Schottky barrier diode 320 is formed so as to be configured by one stage, two stages, or three stages (multistage). In FIG. 2, it has shown about the case where it comprises by 2 steps | paragraphs in series.

  As shown in FIG. 2, one end side of the resistor 310 is connected to the cathode side of the microbial fuel cell 200, and the other end side of the resistor is connected to the anode side of one Schottky barrier diode 320. The cathode side of one Schottky barrier diode 320 is connected to the anode side of another Schottky barrier diode 320. The cathode side of another Schottky barrier diode 320 is connected to the anode side of the microbial fuel cell 200.

  In FIG. 2, the Schottky barrier diode 320 has been described. However, the two-stage configuration of the Schottky barrier diode 320 may be replaced with a general one-stage configuration having a voltage drop of 0.6 volts. However, it is more preferable that the reverse recovery time is short and suitable for high-frequency rectification.

<Backflow prevention circuit>
FIG. 3 is a schematic diagram illustrating an example of the backflow prevention circuit 400.

  The backflow prevention circuit 400 includes a PNP transistor element 410 and a resistor 420. In the present embodiment, the resistance value 420 is, for example, 10,000 ohms (Ω). This resistance value needs to be set depending on the characteristics of the PNP transistor used, but in this configuration, it is set to 10,000 ohms (Ω) so that the voltage drop between the emitter and collector of the transistor is about 0.1 V or less. Configured.

  The emitter terminal of the PNP transistor element 410 is connected to the cathode side of the microbial fuel cell 200, the base terminal is connected to the anode side of the microbial fuel cell 200, and the collector terminal is connected to the capacitor 500 side.

<Load>
The load 600 shown in FIG. 1 includes a booster circuit and / or a communication circuit and / or a control circuit. In the case of a booster circuit, the power stored in the capacitor 500 can be boosted.
When a communication circuit or a control circuit is included, communication with other devices can be performed by a boosted power source. When a control circuit is included, for example, the state of treated water by a sensor is detected and analyzed, and communication is performed. The circuit can be controlled and transmitted to the outside.
As a booster circuit, a DC / DC converter using a transformer is generally used, but a charge pump system that boosts voltage by switching capacitors in series may be used. As the communication circuit, a low power consumption specific low power radio station system or a ZigBee short-range radio communication standard widely used for a center network may be used.

<Comparison result>
4 and 5 are schematic diagrams showing an example of the result of the microbial fuel system 100, and FIGS. 6, 7 and 8 are schematic diagrams showing an example of the result of the conventional microbial fuel system 900. FIG.

The vertical axis in FIG. 4 shows the voltage change, and the vertical axis in FIG. 5 shows the current change. Further, the vertical axis in FIG. 6 represents a change in resistance value, the vertical axis in FIG. 7 represents a voltage change, and the vertical axis in FIG. 8 represents a current change.
Note that the horizontal axes of FIGS. 4 to 8 all indicate the passage of time (day).

  First, as shown in FIG. 7, when the voltage value is monitored and the voltage change reaches from 0.05 to 0.6 volts, the resistance value is manually increased from 10,000 ohms (Ω) as shown in FIG. Vary low to 100 ohms (Ω). As a result, the current value can be increased as shown in FIG.

  Subsequently, as shown in FIG. 7, when the voltage change reaches 0.2 volt to 0.6 volt, the resistance value is manually changed from 100 ohm (Ω) to 10 ohm (Ω) as shown in FIG. Vary to low. As a result, the current value increases as shown in FIG.

By repeating this operation, each time the microorganism grows, the resistance value is changed to 10 ohms (Ω) to promote the transfer of electrons of the microorganism, thereby controlling the increase of microorganisms.
That is, the performance of the microbial fuel cell 200 greatly depends on the composition of the biofilm bacteria in the initial stage. By changing the resistance value to make the voltage constant and properly drawing out the current, it is possible to properly grow the power generation bacteria (microorganisms).

On the other hand, in this embodiment, as shown in FIG. 4, the voltage can be changed from 0.4 volts to 0.6 volts, and there is no need to replace the resistance value.
Further, as shown in FIGS. 4 and 5, even if the voltage is relatively constant, the current change varies from 0 milliampere to 60 milliamperes. The current value is not limited to 60 milliamperes, and the voltage value is about 0.6 V and can be kept at about 0.7 V or less regardless of whether it is 100 milliamperes or 200 milliamperes. Although the current value varies depending on the electrode area of the microbial fuel cell and the volume capacity of the treated water, generally, when the capacity of the treated water is large and the electrode area is large, the generated power is large, that is, the current increases.

In addition, unlike the case where the resistance value is changed as shown in FIGS. 6 to 8, in the case shown in FIGS. 4 and 5 according to the present embodiment, the time for stabilizing the voltage to 0.6 volts and the current 60 mA is about It can be stabilized early around 2 days.
In the present embodiment, since an error in switching timing does not occur, microorganisms can be appropriately grown. Therefore, it is estimated that the power generation amount can be stabilized at an early stage.

  In FIG. 2, the case where a voltage of 0.6 volts (V) is applied to the capacitor 500 has been described. However, the present invention is not limited to this. Are arranged in one stage and 0.9 volt (V), the Schottky barrier diode 320 may be attached to the part α in FIG.

  As described above, in the present embodiment, in the microbial fuel system 100, the current can be changed without requiring several to ten times of switching until the power generation amount of the microorganism is stabilized as in the conventional case. Regardless of the voltage, the voltage can always be constant, the electron transfer of microorganisms can always be in an optimum state, and the power generation amount of the microorganism fuel cell 200 can be stabilized.

  That is, it is possible to completely eliminate the possibility of inhibiting the growth of microorganisms when the conventional switching timing of several to ten times is forgotten.

  Further, since the current stored in the capacitor 500 can be prevented from flowing back to the microbial fuel cell 200, adverse effects on the microorganism can be prevented. Further, the constant voltage can be easily set using the characteristics of the element itself that uses the forward voltage characteristics of the Schottky barrier diode 320. In addition, since a plurality of Schottky barrier diodes 320 can be arranged, the voltage can be easily changed.

  Furthermore, in the present embodiment, by using the PNP transistor element 410, it is possible to appropriately prevent the backflow of the 0.6 volt voltage accumulated in the capacitor 500.

  In the present invention, the microbial fuel cell 200 corresponds to a “microbial fuel cell”, 0 V to 1 V, preferably 0.3 V to 0.9 V corresponds to a “predetermined voltage”, and the constant voltage circuit 300 is “ The microbial fuel system 100 corresponds to “a microbial fuel system and a microbial fuel cell storage method”, and the capacitor 500 corresponds to a “capacitor and a storage process”. The backflow prevention circuit 400 corresponds to “a backflow prevention unit, a PNP transistor element, a backflow prevention process”, the load 600 corresponds to “at least one of a load unit, a boosting unit, and a communication unit”, and a Schottky The barrier diode 320 and / or the PNP-type transistor element 410 correspond to the “storage circuit”, and the Schottky barrier diode 320 Corresponds to "constant voltage unit", PNP-type transistor element 410 corresponds to the "backflow prevention unit".

  A preferred embodiment of the present invention is as described above, but the present invention is not limited thereto. It will be understood that various other embodiments may be made without departing from the spirit and scope of the invention. Furthermore, in this embodiment, although the effect | action and effect by the structure of this invention are described, these effect | actions and effects are examples and do not limit this invention.

DESCRIPTION OF SYMBOLS 100 Microbial fuel system 200 Microbial fuel cell 300 Constant voltage circuit 320 Schottky barrier diode 400 Backflow prevention circuit 410 PNP type transistor element 500 Capacitor 600 Load

Claims (10)

A microbial fuel cell;
A microbial fuel system provided with a constant voltage unit that is provided between an anode and a cathode of the microbial fuel cell and adjusts an output of the microbial fuel cell to a predetermined voltage. A capacitor for storing charge from the microbial fuel cell;
The microbial fuel system according to claim 1, wherein a backflow prevention unit is provided between the microbial fuel cell and the capacitor.   The microbial fuel system according to claim 1, wherein the constant voltage unit includes a rectifying element.   The microbial fuel system according to claim 2 or 3, wherein the constant voltage section includes one or more stages of Schottky barrier diodes.   The microbial fuel system according to any one of claims 2 to 4, wherein the backflow prevention unit includes a PNP transistor element. A load unit connected in parallel with the capacitor;
The microbial fuel system according to any one of claims 1 to 5, wherein the load unit includes at least one of a boosting unit and a communication unit.   A method for storing a microbial fuel cell, comprising a constant voltage step provided between an anode and a cathode of the microbial fuel cell and adjusting an output of the microbial fuel cell to a predetermined voltage. A power storage step for storing electric charge from the microbial fuel cell;
The microbial fuel cell storage method according to claim 7, further comprising: a backflow prevention step for preventing backflow with respect to power storage from the microbial fuel cell to the power storage step. A storage circuit used in an environment of 1 volt or less,
A power storage circuit including a constant voltage unit that adjusts to a predetermined voltage by a rectifying element.   The electric storage circuit according to claim 9, wherein when a charge is stored from the electric storage unit to the electric storage capacitor, the backflow prevention unit is formed by a circuit including a PNP transistor.

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