JP7308481B2 - Cathodic protection device and cathodic protection method for steel materials in concrete structures - Google Patents

Description

TECHNICAL FIELD The present invention relates to an cathodic protection device and cathodic protection method for steel materials in concrete structures.

In a concrete structure, internal permeation of oxygen, water, chloride ions, etc., causes corrosion of steel materials such as reinforcing bars disposed therein. When such steel corrosion occurs, the volume expansion of the corrosion products that accompanies it causes cracks in the concrete, further accelerating the corrosion, causing a reduction in the cross section of the steel, etc., and ultimately reducing the strength of the structure. performance is reduced. Therefore, various means have been developed to prevent the corrosion of steel materials in concrete structures, and one of them is the cathodic protection method.

In the cathodic protection method, the steel material (steel material to be protected against corrosion) in the concrete structure is used as a cathode, and the cathode and the anode (electrode for cathodic protection) installed on the surface of the concrete structure or in a groove cut on the surface. This is a method of preventing corrosion by passing an electric current (anticorrosion current) between them to change the potential of the steel material (cathode) to be protected against corrosion in the negative direction.

There are known galvanic anode method and external power supply method for the electric corrosion protection method. In the galvanic anode method, an anode (electrode for cathodic protection) made of a metal with a lower self-potential than the steel to be protected is installed on the surface of concrete, etc., and the anode and the steel to be protected are electrically connected by a wire or the like. In this method, corrosion of steel materials is prevented by generating an anti-corrosion current between the anode and the steel material to be protected against corrosion by means of a battery action using concrete as an electrolyte. The galvanic anode cathodic protection method does not require an external power supply, but the anode (electrode for cathodic protection) needs to be replaced periodically.

On the other hand, in the external power supply method, the anode (electrode for cathodic protection) installed in the surface of the concrete structure or a groove cut in the surface is connected to the positive electrode of the external power supply, and the steel material to be protected against corrosion is connected to the external power supply. It is a method to prevent corrosion by connecting to the negative electrode and applying an anti-corrosion current between the anode and the steel material to be protected from corrosion by an external power supply device. The cathodic protection method using an external power supply system can obtain stable power over a long period of time by using an external power supply, but on the other hand, it is necessary to constantly supply power from the external power supply, which tends to increase the cost required for cathodic protection. .

In relation to this, an external power source type cathodic protection method using a solar battery as a power source has been proposed (see, for example, Patent Document 1). However, in the case of the external power supply system using a solar battery as a power supply, there are problems such as unstable power supply at night or in bad weather, and difficulty in applying it to structures that are not exposed to sunlight.

JP-A-7-316850

In addition, Patent Document 1 discloses a method for constantly preventing corrosion by switching a pre-installed sacrificial anode circuit from an external power source to operate when sunlight is insufficient. It is necessary to combine different corrosion protection methods.

The present invention has been made in view of the above problems, and its object is to eliminate the need to supply commercial power from the outside by using self-generated power, and to use it at night or in bad weather. To provide a cathodic protection technique for steel materials in a concrete structure capable of stably supplying electric power.

The present invention for solving the above problems employs the following means. That is, the present invention provides an electric corrosion protection device for preventing corrosion of a steel material to be corrosion-protected in a concrete structure by applying an anti-corrosion current from an anode material installed in the concrete structure to the steel material to be corrosion-protected in the concrete structure, wherein the anode material a power generation unit that generates electric power for supplying an anticorrosion current to the steel material to be protected from corrosion, wherein the power generation unit includes an n-type thermoelectric conversion element and a p-type thermoelectric conversion element alternately and via electrodes and It is characterized by including thermoelectric conversion modules electrically connected in series.

In the present invention, each of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element may have a phononic crystal structure. Moreover, the thermoelectric conversion module may have a thin film shape, or may have a bulk shape. Here, the p-type thermoelectric conversion element and the n-type thermoelectric conversion element may be formed with a large number of pores having a diameter of submicro order or nano order penetrating through the element in the thickness direction.

Moreover, in the present invention, the power generation section may include a plurality of the thermoelectric conversion modules.

Moreover, in the present invention, the thermoelectric conversion modules may be electrically connected in parallel or in series.

Further, in the present invention, the thermoelectric conversion module is arranged on a support substrate made of an electrically insulating material, and the electrodes are disposed on both ends of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element in the heat conduction direction. The low temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element are supported by a support portion provided on the support substrate, and the n-type thermoelectric conversion element and the p The high-temperature side end of the thermoelectric conversion element may be out of contact with the support substrate.

Further, the thermoelectric conversion module exhibits a π-type shape by alternately connecting the n-type thermoelectric conversion elements and the p-type thermoelectric conversion elements in series via the electrodes, and has a plurality of thermoelectric conversion modules arranged in parallel to each other. wherein in the plurality of π-shaped portions, a pair of mutually adjacent π-shaped portions are connected via a connecting portion, and a set of π-shaped portions connected via the connecting portion are projected from the support substrate and supported by a pair of support portions spaced apart from each other, so that the pair of π-shaped portions are bridged between the pair of support portions, and the coupling The low-temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element included in a pair of π-shaped portions connected via a portion are supported by the support portion, and the high-temperature side end portions may be connected by the connecting portion.

Moreover, in the present invention, the power generation unit may be installed on the concrete surface of the concrete structure.

Further, the present invention can be specified as a method for cathodic protection of steel materials in concrete structures. That is, the present invention provides a cathodic protection method for protecting a steel material to be corrosion-protected in a concrete structure by applying an anti-corrosion current from an anode material installed in the concrete structure to the steel material to be corrosion-protected in the concrete structure. In a power generation unit having a thermoelectric conversion module in which conversion elements and p-type thermoelectric conversion elements are alternately and electrically connected in series via electrodes, the high temperature side of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element Electricity is generated by utilizing the temperature difference between the end portion and the low-temperature side end portion, and the generated electric power is used to flow an anti-corrosion current from the anode material to the anti-corrosion target steel material.

According to the present invention, self-generated electric power is used to eliminate the need to supply commercial electric power from the outside, and it is possible to stably supply electric power even at night or in bad weather. Cathodic protection of steel materials in concrete structures We can provide technology.

FIG. 1 is a schematic side view of a reinforced concrete structure to which the cathodic protection device and cathodic protection method according to Embodiment 1 are applied. 2 is a cross-sectional view of a bridge girder according to Embodiment 1. FIG. FIG. 3 is a diagram for explaining the cathodic protection device according to Embodiment 1. FIG. 4 is a front view of a power generating device installed on an installation target surface of a main girder according to Embodiment 1. FIG. 5 is a front view of the power generation panel according to Embodiment 1. FIG. 6 is a diagram schematically illustrating a planar structure of the thermoelectric conversion unit according to Embodiment 1. FIG. 7 is a diagram schematically showing a cross-sectional structure of a thermoelectric conversion unit according to Embodiment 1. FIG. FIG. 8 is a diagram for explaining the bridge structure of the thermoelectric conversion module according to Embodiment 1. FIG. FIG. 9 is a schematic diagram for explaining a current flowing due to a potential difference caused by the Seebeck effect in the thermoelectric conversion module according to Embodiment 1. FIG. FIG. 10 is an electron microscope image of a part of the fabricated thermoelectric conversion module. FIG. 11 is a diagram showing an example of installing a power generation panel of a power generation device on the inner wall surface of a tunnel.

BEST MODE FOR CARRYING OUT THE INVENTION An cathodic protection device and a cathodic protection method for steel materials in concrete structures according to embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1>
FIG. 1 is a schematic side view of a bridge girder 1 as an example of a reinforced concrete structure to which the cathodic protection device and cathodic protection method according to Embodiment 1 are applied. The bridge girder 1 spans between bridge piers 2, 2, as shown in FIG. FIG. 2 is a cross-sectional view of the bridge girder 1 according to Embodiment 1. FIG. The bridge girder 1 is formed by arranging a plurality of main girders 10 substantially in parallel. In the example shown in FIG. 2, the main girder 10 of the bridge girder 1 has a substantially T-shaped cross-section, and a PC slab 11 is installed between the upper floor slabs 10a of the adjacent main girder 10. As shown in FIG. An RC floor slab 12 is placed on site on the upper floor slab portion 10a of the main girder 10 and the PC slab 11 to form a continuous concrete floor slab. A road surface is formed on the upper surface of this concrete floor slab by pavement 13 or the like. As shown in FIG. 2, cross beams 14 are provided at the ends of the main girders 10. A plurality of main girders 10 are integrated and supported on the piers 2 by bearings 15. .

FIG. 3 is a diagram illustrating the cathodic protection device 100 according to the first embodiment. In FIG. 3, the lower area of the main girder 10 is illustrated. Reference numeral 4 in FIG. 3 illustrates reinforcing bars (main bars) of the main girder 10 . The reinforcing bars 4 extend along the longitudinal direction (bridge axis direction) of the main girder 10 . Reference numeral 5 in FIG. 3 is concrete. The cathodic protection device 100 in this embodiment includes the anode material 6, the power generation device 7, and the like. In the present embodiment, a description will be given of a mode in which the reinforcing bars 4 of the main girder 10 are treated as steel materials to be protected against corrosion by the electrostatic protection device 100 .

In the example shown in FIG. 3, the anode material 6 adopts the planar anode method and is installed on the surface (bottom surface in this example) of the main girder 10 which is a concrete structure. The anode material 6 may be titanium mesh or the like, for example. The power generation device 7 is attached to the installation target surface 5A, which is the concrete surface of the main girder 10 . In this embodiment, an example in which the concrete side surface forming the side surface of the main girder 10 is set as the installation target surface 5A will be described, but the power generation device 7 may be installed on the concrete surface of other portions.

4 is a front view of the power generator 7 installed on the installation target surface 5A of the main girder 10 according to Embodiment 1. FIG. The power generation device 7 includes a plurality of power generation panels 70 and external connection devices 80 . The external connection device 80 has a positive terminal 80A and a negative terminal 80B as external terminals. The power generation panel 70 includes a support substrate 71 made of an electrically insulating material, a power generation portion 72 formed on the support substrate 71, a positive electrode terminal 73A and a negative electrode terminal 73B as external terminals provided on the support substrate 71, and the like. have. The positive electrode terminal 73A and the negative electrode terminal 73B of each power generation panel 70 are connected to the positive electrode terminal 80A and the negative electrode terminal 80B of the external connection device 80 via lead wires (not shown) and the like, respectively. In FIG. 4 , an area surrounded by a dashed line indicates an area of the power generation panel 70 in which the power generation section 72 is formed.

Here, the power generation panel 70 and the external connection device 80 in the power generation device 7 are attached to the installation target surface 5A of the main girder 10 using an appropriate method. In this embodiment, the back surface of the support substrate 71 of each power generation panel 70 is adhered to the installation target surface 5A of the main girder 10 via a thermally conductive adhesive. Although the detailed structure of the power generation section 72 in the power generation panel 70 will be described later, the power generation section 72 in this embodiment includes a large number of thermoelectric conversion modules that generate power by a thermoelectric conversion method. Electric power generated in each power generation panel 70 is supplied to the external connection device 80 via a lead wire or the like.

Further, as shown in FIG. 3, the positive electrode terminal 80A of the external connection device 80 in the power generation device 7 is connected via a lead wire 81 to the anode material 6 installed on the concrete surface of the main girder 10. Conducting with the anode material 6 . In addition, the negative electrode terminal 80B of the external connection device 80 is connected to each reinforcing bar 4 as a steel material to be protected against corrosion in the main girder 10 via a lead wire 82, thereby being electrically connected to each reinforcing bar 4. The power generation device 7 uses power generated in each power generation panel 70 to supply a direct current to the anode material 6 from the positive electrode terminal 80A of the external connection device 80 . Here, since the concrete 5 is an electrolyte, the DC current supplied from the power generator 7 to the anode material 6 passes through the concrete 5 and is connected to the negative electrode terminal 80B of the external connection device 80. It flows on the surface of the target steel). In this way, by applying the anti-corrosion current to the surface of the reinforcing bar 4 as the steel material to be protected from corrosion, the corrosion reaction of the reinforcing bar 4 can be stopped and the corrosion can be suppressed.

Next, the power generation section 72 in the power generation panel 70 will be described in detail. FIG. 5 is a front view of the power generation panel 70 according to Embodiment 1. FIG. The power generation section 72 in the power generation panel 70 is a power generation region in which a large number of planar thermoelectric conversion units 9 are arranged on the surface of the support substrate 71 . As shown in FIG. 5, the plurality of thermoelectric conversion units 9 in the power generation section 72 are arranged in a grid on the surface of the support substrate 71 along the vertical and horizontal directions. Although the planar shape and size of the thermoelectric conversion unit 9 are not particularly limited, in the illustrated example, the thermoelectric conversion unit 9 has a rectangular planar shape with each side of several millimeters to ten and several millimeters. Also, the planar shape and size of the support substrate 71 of the power generation panel 70 are not particularly limited, but in the illustrated example, the support substrate 71 has a rectangular planar shape with each side of about several tens of centimeters.

FIG. 6 is a diagram schematically illustrating the planar structure of the thermoelectric conversion unit 9 according to Embodiment 1. FIG. FIG. 7 is a diagram schematically showing a cross-sectional structure of the thermoelectric conversion unit 9 according to Embodiment 1. FIG. The thermoelectric conversion unit 9 in this embodiment includes one or more thermoelectric conversion modules 3 . That is, in the present embodiment, the number of thermoelectric conversion modules 3 included in the thermoelectric conversion unit 9 is not particularly limited, and when one thermoelectric conversion unit 9 includes a plurality of thermoelectric conversion modules 3, the Each thermoelectric conversion module 3 included in one thermoelectric conversion unit 9 may be electrically connected in series or may be electrically connected in parallel. Further, between the plurality of thermoelectric conversion units 9 included in the power generation section 72, the respective thermoelectric conversion modules 3 may be connected in series or in parallel.

Here, a mode in which the thermoelectric conversion unit 9 includes a single thermoelectric conversion module 3 will be described as an example. As shown in FIG. 6 and the like, in the thermoelectric conversion module 3, n-type thermoelectric conversion elements 31 having a phononic crystal structure and p-type thermoelectric conversion elements 32 having a phononic crystal structure are alternately and electrically connected via electrodes 34A and 34B. It is a thin-film thermoelectric conversion module that exhibits a so-called π (pi) shape, which is connected in series. Here, the phononic crystal structure will be described in detail later. Note that FIG. 6 is a partially enlarged view of the thermoelectric conversion module 3, and only a part of the thermoelectric conversion module 3 is illustrated.

Reference numeral 33 in FIG. 6 denotes a “π-shaped portion” included in the thermoelectric conversion module 3 . In the example shown in FIG. 6, the thermoelectric conversion module 3 includes a plurality of π-shaped portions 33 electrically connected in series. However, in this embodiment, the thermoelectric conversion module 3 may be formed by a single π-shaped portion 33 . In the example shown in FIG. 6, each π-shaped portion 33 in the thermoelectric conversion module 3 extends in the same direction. Hereinafter, the extending direction of each π-shaped portion 33 is referred to as "π-shaped portion extending direction D1". Here, each π-shaped portion 33 in the thermoelectric conversion module 3 is arranged parallel to each other. More specifically, the π-shaped portions 33 in the thermoelectric conversion module 3 are arranged side by side in the “π-shaped portion arrangement direction D2” orthogonal to the π-shaped portion extending direction D1. Therefore, as the module as a whole, the thermoelectric conversion module 3 is formed by arranging the n-type thermoelectric conversion elements 31 and the p-type thermoelectric conversion elements 32 in a matrix. Although the sizes of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 are not particularly limited, they may have, for example, a rectangular shape with a side of several tens of micrometers.

In each π-shaped portion 33 of the thermoelectric conversion module 3, the n-type thermoelectric conversion elements 31 and the p-type thermoelectric conversion elements 32 are alternately arranged adjacent to each other along the π-shaped portion extending direction D1. Ends of the conversion element 31 and the p-type thermoelectric conversion element 32 are joined by electrodes 34A and 34B. Here, reference numerals 31A and 32A shown in FIG. 6 denote high temperature side ends of a pair of n-type thermoelectric conversion elements 31 and p-type thermoelectric conversion elements 32 connected to each other via electrodes 34A. Reference numerals 31B and 32B shown in FIG. 6 denote low-temperature side ends of a pair of n-type thermoelectric conversion elements 31 and p-type thermoelectric conversion elements 32 connected in series with each other via electrodes 34B.

The electrodes 34A and 34B are arranged in a state of being shifted by one thermoelectric conversion element. formed. In the present embodiment, the positions of the high temperature side end portion 31A of the n-type thermoelectric conversion element 31 and the high temperature side end portion 32A of the p-type thermoelectric conversion element 32 included in each π-type portion 33 are mutually aligned in the π-type portion arrangement direction D2. Aligned. In addition, the positions of the low-temperature side end portions 31B of the n-type thermoelectric conversion elements 31 and the low-temperature side end portions 32B of the p-type thermoelectric conversion elements 32 included in each π-type portion 33 are aligned in the π-type portion arrangement direction D2. . In the thermoelectric conversion module 3 according to the present embodiment, heat conduction is performed from the high temperature side end portion 31A toward the low temperature side end portion 31B of the n-type thermoelectric conversion element 31 based on the temperature difference between the two, and the p-type thermoelectric conversion is performed. Heat is conducted from the high temperature side end portion 32A of the conversion element 32 toward the low temperature side end portion 32B based on the temperature difference therebetween. Hereinafter, the direction connecting the high temperature side end portion 31A and the low temperature side end portion 31B of the n-type thermoelectric conversion element 31 and the direction connecting the high temperature side end portion 32A and the low temperature side end portion 32B of the p-type thermoelectric conversion element 32 will be referred to as "thermal called the conduction direction. The direction of heat conduction in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 coincides with the π-shaped portion arrangement direction D2.

In FIG. 6, of the n-type thermoelectric conversion elements 31 and the p-type thermoelectric conversion elements 32 shown, only some of the high temperature side ends 31A and 32A and the low temperature side ends 31B and 32B are sign is indicated. Moreover, in FIG. 6, only some of the electrodes 34A and 34B are labeled with these symbols.

Next, the cross-sectional structure of the thermoelectric conversion unit 9 will be described with reference to FIG. As shown in FIG. 7 , the thermoelectric conversion module 3 in the thermoelectric conversion unit 9 is arranged on a support substrate 71 . Further, as shown in FIG. 7 , a plurality of support portions 710 are protruded from the support substrate 71 so as to protrude, and the thermoelectric conversion module 3 is supported by the support portions 710 . 7 shows a cross section taken along the line AA in FIG. A support portion 710 projecting from the support substrate 71 is arranged to extend along the π-shaped portion extending direction D1 in the thermoelectric conversion unit 9 . Further, the support portions 710 are arranged at regular intervals in the π-shaped portion arrangement direction D2. Further, on the surface of the support substrate 71 , a recessed surface region 711 is formed in a region sandwiched between the support portions 710 so that the surface is recessed relative to the support portions 710 . Therefore, the rear surface S1 of the thermoelectric conversion module 3 is supported by the supporting portion 710 on which the surface of the support substrate 71 is raised, so that the space between the rear surface S1 of the thermoelectric conversion module 3 and the concave surface region 711 in the support substrate 71 is , a cavity 712 is formed.

The support substrate 71 in this embodiment is made of an electrically insulating material as described above. In this embodiment, the support substrate 71 is formed of a silicon substrate, but other materials such as semiconductors other than silicon, metals such as copper and aluminum, ceramics such as silicon carbide, carbon-based materials, and high thermal conductive resins may be used. The support substrate 71 may be formed of any material. Also, the support part 710 is formed of, for example, a thin silicon dioxide (SiO ₂ ) insulating film laminated on a silicon substrate forming the support substrate 71 . In this embodiment, the support substrate 71 may be electrically conductive as long as the support portion 710 is made of an insulating material.

Reference numeral 300 in FIG. 7 denotes a silicon thin film material for forming the thermoelectric conversion module 3 . The silicon thin film material 300 includes doped regions R1 and undoped regions R2 forming the n-type thermoelectric conversion elements 31 and the p-type thermoelectric conversion elements 32 in the thermoelectric conversion module 3 . The doped region R1 is a region doped n-type or p-type by mixing dopants into silicon atoms. That is, the n-type thermoelectric conversion element 31 in the thermoelectric conversion module 3 is formed of a region doped n-type by implanting a pentavalent atom such as phosphorus (P) as a dopant into silicon atoms, for example. It is a semiconductor element using as a carrier. On the other hand, the p-type thermoelectric conversion elements 32 in the thermoelectric conversion module 3 are formed of p-type doped regions by implanting trivalent atoms such as boron (B) into silicon atoms as dopants. It is a semiconductor element that uses a hole) as a carrier. On the other hand, the undoped region R2 in the silicon thin film material is a region in which silicon atoms are not doped, and is formed as an intrinsic semiconductor. In this embodiment, an insulating film is formed in the non-doped region R2 of the silicon thin film material 300 . The electrodes 34A and 34B connecting the ends of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in the thermoelectric conversion module 3 are formed by vapor-depositing, for example, aluminum electrodes on the doped region R1 of the silicon thin film material 300. and so on.

Here, as shown in FIG. 7, the thermoelectric conversion module 3 includes n-type thermoelectric conversion elements 31 and p
The low-temperature side ends 31B and 32B of the thermoelectric conversion element 32 are placed on a support portion 710 of the support substrate 71 and supported. On the other hand, the high-temperature side end portions 31A and 32A of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 are separated from the concave surface region 711 located between the support portions 710 of the support substrate 71. Located on top of 711. That is, the high temperature side ends 31A and 32A of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 are arranged in a non-contact state with the support substrate 71 .

Further, in the thermoelectric conversion module 3 of the present embodiment, a pair of π-shaped portions 33 adjacent to each other in the π-shaped portion arrangement direction D2 are connected via a connecting portion 310 formed by an undoped region R2 in the silicon thin film material 300. It is The connecting portion 310 connects the high temperature side end portion 31A of the n-type thermoelectric conversion element 31 in one of the pair of π-shaped portions 33 adjacent to each other in the π-shaped portion arrangement direction D2 and the other π-shaped portion 33 in the other π-shaped portion 33 . , the high-temperature side ends 32A of the p-type thermoelectric conversion elements 32 are connected to each other. In the thermoelectric conversion module 3 configured as described above, the pair of π-shaped portions 33 connected via the connecting portion 310 are supported by the support portion 710, so that the concave surface region 711 (cavity portion 712) It has a bridge structure.

FIG. 8 is a diagram for explaining the bridge structure of the thermoelectric conversion module 3 according to Embodiment 1. FIG. According to such a bridge structure, the high-temperature side ends 31A and 32A of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in the thermoelectric conversion module 3 are arranged in a non-contact state with the support substrate 71. Therefore, it is likely to be exposed to the external environment (external atmosphere) through the air. On the other hand, the low-temperature side end portions 31B and 32B of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in the thermoelectric conversion module 3 are supported by the support portion 710, thereby allowing the main girder 10 to move through the support substrate 71. The temperature of the installation target surface 5A in the (concrete structure) is easily transmitted. As a result, using the temperature difference between the surface temperature of the installation target surface 5A in the main girder 10 (concrete structure) and the surrounding ambient temperature (for example, the outside air temperature), n-type thermoelectric conversion in the thermoelectric conversion module 3 A temperature difference can be generated between the high temperature side end portion 31A and the low temperature side end portion 31B of the element 31 . Similarly, a temperature difference can be generated between the high temperature side end portion 32A and the low temperature side end portion 32B of the p-type thermoelectric conversion element 32 . As a result, the Seebeck effect can generate a potential difference (voltage) proportional to the temperature difference across the thermoelectric conversion element. In this embodiment, a cavity 712 is formed between the support substrate 71 and the silicon thin film material 300 to allow air to enter the cavity 712. A structure in which the hollow portion 712 is filled with a low thermal conductivity material having a low thermal conductivity may be adopted, and by adopting such a structure, the high temperature A temperature difference can be favorably generated between the side ends 31A, 32A and the low temperature side ends 31B, 32B.

In this embodiment, the power generation panel 70 of the power generation device 7 is attached to the installation target surface 5A, which is the concrete surface of the main girder 10, using a thermally conductive adhesive. Also, it is generally considered that the concrete surface temperature is lower than the outside air temperature. Therefore, in each thermoelectric conversion unit 9 (thermoelectric conversion module 3) arranged in the power generation section 72 of the power generation panel 70, the low temperature side end 31B of the n-type thermoelectric conversion element 31 is relatively higher than the high temperature side end 31A. The temperature becomes low, and heat conduction occurs from the high temperature side end portion 31A toward the low temperature side end portion 31B. Similarly, the low temperature side end 32B of the p-type thermoelectric conversion element 32 becomes relatively colder than the high temperature side end 32A, and heat conduction occurs from the high temperature side end 32A toward the low temperature side end 32B.

FIG. 9 is a schematic diagram for explaining a current flowing due to a potential difference caused by the Seebeck effect in the thermoelectric conversion module 3 according to Embodiment 1. FIG. Since the number of negatively charged electrons in the n-type thermoelectric conversion element 31 is larger than the number of positively charged holes (positive holes), the temperature difference between the high temperature side end 31A and the low temperature side end 31B increases. Electrons diffuse from the side end portion 31A toward the low temperature side end portion 31B (indicated by the dashed arrow in FIG. 9). As a result, n
In the type thermoelectric conversion element 31, the high temperature side end portion 31A has a higher potential than the low temperature side end portion 31B.

On the other hand, the p-type thermoelectric conversion element 32 has more holes than electrons. Holes are diffused toward the portion 32B (indicated by chain-line arrows in FIG. 9). As a result, in the p-type thermoelectric conversion element 32, the low temperature side end portion 32B becomes a higher potential than the high temperature side end portion 32A. Due to the mechanism as described above, the thermoelectric conversion module 3 in this embodiment causes current to flow in the direction of the solid line arrow shown in FIG. 9 . In FIG. 9, the meandering thick solid line schematically shows the flow of electric current that flows through the thermoelectric conversion elements 31 and 32 and the electrodes 34A and 34B of the thermoelectric conversion module 3 as electrical paths.

Here, reference numeral 91 shown in FIG. 9 is a positive electrode terminal in each thermoelectric conversion unit 9 (thermoelectric conversion module 3), and reference numeral 92 is a negative electrode terminal in each thermoelectric conversion unit 9 (thermoelectric conversion module 3). . The positive electrode terminal 91 is a thermoelectric conversion element forming the end located on the high potential side in the thermoelectric conversion module 3 (in the example shown in FIG. 9, the p-type thermoelectric conversion element indicated by reference numeral 32 (X) corresponds to ) (electrode 34B in the example shown in FIG. 9). The negative electrode terminal 92 is connected to the thermoelectric conversion element (in the example shown in FIG. 9, the n-type thermoelectric conversion element indicated by 31(X)) forming the end portion located on the low potential side in the thermoelectric conversion module 3. corresponding) (in the example shown in FIG. 9, the electrode 34B corresponds). The positive electrode terminal 91 and the negative electrode terminal 92 of each thermoelectric conversion unit 9 (thermoelectric conversion module 3) are connected to the positive electrode terminal 73A and the negative electrode terminal 73B of the power generation panel 70 shown in FIG. are connected to each. Thereby, the power generated by each thermoelectric conversion unit 9 (thermoelectric conversion module 3 ) can be transmitted to the external connection device 80 . In the description here, the case where all the thermoelectric conversion units 9 (thermoelectric conversion modules 3) included in one power generation panel 70 are connected in parallel is described as an example, but some or all of them are connected in series. It may be connected.

Next, the phononic crystal (PnC) structure of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in the thermoelectric conversion module 3 will be described. Here, the phononic crystal structure is an artificial crystal composed of a periodic structure of heterogeneous elastic bodies. In addition, the phononic crystal structure can also be said to be a crystal structure in which heterogeneous elastic bodies are periodically arranged with a length on the order of the wavelength of phonons. Here, phonons (sometimes called “thermal phonons”) are particles that transport heat in a solid. is done. In this embodiment, the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in the thermoelectric conversion module 3 are formed with a large number of through-holes that are periodically aligned in submicro order or nano order, thereby n-type thermoelectric conversion The element 31 and the p-type thermoelectric conversion element 32 have a phononic crystal structure.

FIG. 10 is an electron microscope image of a part of the fabricated thermoelectric conversion module 3 . As shown in FIG. 10, the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 have a large number (plurality) of pores C arranged periodically. The pores C pass through the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in the thickness direction, and are formed as circular holes having a circular cross-sectional shape in this embodiment. The diameter of the pore C is designed to have sub-micro order or nano order dimensions. Formation of the pores C in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 can be performed using a semiconductor microfabrication technology. Although the pores C in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 are schematically shown in FIG. 8, the pores C are not shown in FIGS. omitted.

By the way, the figure of merit ZT of thermoelectric conversion is the Seebeck coefficient S, electrical conductivity σ, thermal conductivity k
, the temperature difference T is expressed as the following equation (1).
ZT=S ² ×σ×T/k (1)
Here, S [V / K]: Seebeck coefficient, σ [1 / Ωm]: electrical resistivity, k [W / (mK)]: thermal conductivity

Therefore, in order to increase the thermoelectric conversion efficiency in the thermoelectric conversion module 3, reducing the thermal conductivity is an important factor. On the other hand, in the thermoelectric conversion module 3 of the present embodiment, the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 have a phononic crystal structure, and many pores C are arranged. According to this, in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32, when phonons are transported from the high temperature side end portion 31A toward the low temperature side end portion 31B, the phonons are scattered by the pores C. Therefore, phonon transport can be significantly inhibited. As a result, the thermal conductivity of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in the thermoelectric conversion module 3 can be significantly reduced, and therefore the temperature difference generated between both ends of the thermoelectric conversion material increases, Thermoelectric conversion efficiency (power generation efficiency) can be increased.

In addition, in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 in this embodiment, the interval between the pores C is preferably set to a dimension smaller than the mean free path of phonons. The mean free path of a phonon is defined as the average distance (free path) that a phonon can travel without being disturbed by scattering (collision) by a scattering source. For example, the distance between the pores C in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 may be several tens of nm to 100 nm. By setting the interval between the pores C to a dimension smaller than the mean free path of phonons, phonons can be further scattered in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 . As a result, the thermoelectric conversion efficiency (power generation efficiency) of the thermoelectric conversion module 3 can be further improved.

According to the power generation device 7 having the thermoelectric conversion module 3 configured as described above and the cathodic protection device 100 having the power generation device 7, electric power is supplied to the surface of the reinforcing bar 4 (steel material to be protected against corrosion) to supply the anti-corrosion current. , the thermoelectric conversion module 3 can suitably generate power. Therefore, it is not necessary to constantly supply electric power from an external power supply device, and the cost required for cathodic protection of the reinforcing bars 4 can be reduced. In addition, unlike the cathodic protection method using the galvanic anode method, there is no need to periodically replace the anode (electrode for cathodic protection), and maintenance is excellent.

In addition, the thermoelectric conversion module 3 in this embodiment can generate power by utilizing the temperature difference between the concrete surface temperature of the concrete structure and the ambient temperature (for example, the outside air temperature). It is possible to stably generate power without being affected by the weather. That is, according to the cathodic protection device 100 according to the present embodiment, the anti-corrosion current can always be stably applied to the surface of the reinforcing bar 4 (steel material for anti-corrosion protection) even at night or in bad weather. In particular, since the thermoelectric conversion module 3 in this embodiment employs the phononic crystal structure as described above, the thermoelectric conversion efficiency (power generation efficiency) can be favorably increased.

Furthermore, according to the power generation device 7 of the cathodic protection device 100 of the present embodiment, the thermoelectric conversion module 3 generates power using the temperature difference, so the power generation panel 70 can be installed anywhere. High degree of freedom. That is, even if it is installed in a place where sunlight cannot reach, such as the bottom surface of the main girder 10, it is possible to stably generate power using the environmental temperature difference. Therefore, in the example shown in FIG. A panel 70) may be installed.

Further, in the power generation device 7 of the cathodic protection device 100 in this embodiment, the power generation panel 7
0 can be directly attached to the concrete surface of the concrete structure including the reinforcing bars 4 (steel to be protected against corrosion), so power transmission loss is suppressed compared to the case of transmitting power from an external power supply device far from the concrete structure. can.

Next, the power generation capacity that can be generated by the thermoelectric conversion module 3 included in the power generation device 7 in this embodiment will be evaluated.

Here, according to the electrochemical corrosion protection method design and construction guidelines (draft) [Japan Society of Civil Engineers] (hereinafter simply referred to as the "design and construction guidelines"), in the cathodic corrosion protection method, the current density of the anticorrosion current required for corrosion protection of steel materials is 0 It is described that the current is generally about 0.001 to 0.03 A/m ² (0.1 to 3 μA/cm ² ), and that the applied voltage of the anticorrosive current is generally about 1 to 5V.

On the other hand, the temperature difference (environmental temperature difference) between the surface temperature of the installation target surface 5A in the concrete structure on which the power generation panel 70 of the power generation device 7 is installed and the surrounding ambient temperature (for example, the outside air temperature) is 2 °C, and assuming that the temperature difference between the high-temperature side ends 31A, 32A and the low-temperature side ends 31B, 32B of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 is ¹ °C, A simulation result that electric power can be obtained was obtained.

Further, when the temperature difference between the high temperature side end portions 31A and 32A and the low temperature side end portions 31B and 32B of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 is 1° C., a pair of thermoelectric conversion elements (one set A result is obtained that a potential difference of about 300 μV is generated per n-type thermoelectric conversion element 31 and p-type thermoelectric conversion element 32). As shown in FIG. 10, the actually produced thermoelectric conversion module 3 has a pair of thermoelectric conversion elements (one set of n-type thermoelectric conversion element 31 and p-type thermoelectric conversion element 32) with a short side dimension of about 30 μm. Since the long side dimension is about 40 μm, it is possible to cover 80,000 pairs of thermoelectric conversion elements per 1 cm ² . In this case, by connecting 80,000 pairs of thermoelectric conversion elements in series, a potential difference of about 24 V can be generated (80000 pairs×300 μV×10 ⁻⁶ =24 V).

The 24V calculated as described above is larger than the 1 to 5V required as the energizing voltage of the anticorrosion current in this design and construction guideline. Therefore, by adjusting the number of sets (number of stages) in which the thermoelectric conversion element pairs (the number of sets of n-type thermoelectric conversion element 31 and p-type thermoelectric conversion element 32) are connected in series, the anticorrosion current required in this design and construction guideline can be easily obtained. Practically, a plurality of thermoelectric conversion modules 3 are arranged per 1 cm ² (for example, one thermoelectric conversion module 3 is arranged for each 5 mm square area), and these plurality of thermoelectric conversion modules 3 are connected in parallel. Therefore, it is preferable to adjust the potential difference generated in each thermoelectric conversion module 3 to be in the range of 1 to 5V.

Next, when calculating the current density of the current obtained by the thermoelectric conversion module 3, the temperature of the high temperature side ends 31A and 32A and the low temperature side ends 31B and 32B of the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 is Assuming that the difference is 1° C., and the number of pairs of thermoelectric conversion elements is adjusted so that the applied current voltage is in the range of 1 to 5 V, the following formula (2) gives power W=30 μW/cm ² , Substituting a voltage of V=1-5 V, it can be seen that a current of A=6-30 μA/cm ² is obtained.
A (current) = W (power)/V (voltage) (2)

Therefore, it can be seen that the thermoelectric conversion module 3 can easily obtain the current density of the anti-corrosion current required in this design and construction guideline (6 to 30 μA/cm ² >0.1 to 3 μA/cm ² ).

As described above, according to the thermoelectric conversion module 3 according to the present invention having a phononic crystal structure, it is possible to easily obtain a current that satisfies the applied voltage and current density required by this design and construction guideline.

In this embodiment, an example in which the pores C arranged in the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 are circular holes has been described, but the shape of the pores C is not particularly limited. Further, in the present embodiment, the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 each have a phononic crystal structure, but they do not necessarily have a phononic crystal structure. . If the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 do not employ a phononic crystal structure, the pores C need not have periodicity like the phononic crystal. Further, in the present embodiment, the n-type thermoelectric conversion element 31 and the p-type thermoelectric conversion element 32 are formed by doping silicon atoms in the silicon thin film material 300 to n-type or p-type. For example, Ge, SiGe, CrSi ₂ , FeSi ₂ , MnSi, Mg ₂ Si, Mg ₂ Ge, CoSb ₃ , AgSbTe ₂ , SnTe, PbT, etc. may be used. In addition, in this embodiment, although the form which formed the thermoelectric conversion module 3 in the shape of a thin film was demonstrated as an example, it is not limited to this. For example, the thermoelectric conversion module 3 may be formed in bulk.

Moreover, the power generator 7 of the present embodiment may include a booster (booster circuit) for boosting the voltage of the anticorrosion current obtained by using the temperature difference in the thermoelectric conversion module 3 . As a result, it is possible to easily secure the voltage required by the above design and construction guidelines even under conditions where the environmental temperature difference is small. Moreover, the power generator 7 may include a rectifier (rectifier circuit). As a result, even when the surface temperature of the installation target surface 5A on which the power generation panel 70 of the power generation device 7 is installed becomes higher than the surrounding ambient temperature (for example, the outside temperature), the anti-corrosion current flows in the opposite direction. It can be suppressed.

In addition to the thermoelectric conversion unit 9 (thermoelectric conversion module 3), the power generation device 7 of the cathodic protection device 100 in this embodiment may further include a solar power generation device or a vibration power generation device. By utilizing the sunlight or the vibration of the concrete structure in which the cathodic protection device 100 is installed, it is possible to stably supply the anti-corrosion current to the steel material to be anti-corrosion. The above-described vibration power generation device may employ, for example, one having a piezoelectric element. Moreover, the cathodic protection device 100 in this embodiment may further include a power storage device such as a capacitor or a secondary battery for storing the electric power generated by the power generation device 7 . According to these, the anti-corrosion current can be more stably supplied to the steel material to be anti-corrosion-protected.

In the above-described embodiment, an example in which the reinforcing bars 4 of the main girder 10 are steel materials to be corrosion-protected has been described, but the present invention is not limited to this. That is, the cathodic protection device 100 in this embodiment can be applied to cathodic protection of steel materials in various concrete structures. For example, the cathodic protection device 100 according to the present embodiment may be used to cathodic protect steel materials such as reinforcing bars contained in the lining concrete 210 of the tunnel 200 shown in FIG. 11 . In this case, it is preferable to install the power generator 7 (power generation panel 70 ) on the inner wall surface 220 on the inner air side of the tunnel 200 . That is, the inner space side of the tunnel 200 has a relatively high temperature due to, for example, the influence of the exhaust gas of vehicles passing through the tunnel 200, and it is easy to secure a temperature difference from the inner wall surface 220 of the tunnel 200. As a result, a sufficient environmental temperature difference can easily be secured, and the thermoelectric conversion efficiency (power generation efficiency) in the thermoelectric conversion module 3 can be favorably increased.

Although the embodiments of the present invention have been described above, various modifications can be adopted for the cathodic protection device and cathodic protection method for steel materials in concrete structures according to the present invention.

Reference Signs List 1 Bridge girder 2 Bridge pier 3 Thermoelectric conversion module 4 Rebar 5 Concrete 6 Anode material 7 Power generator 9 Thermoelectric conversion unit C Pore 31...n-type thermoelectric conversion element 32...p-type thermoelectric conversion element 33...π-type portion 70...power generation panel 71...support substrate 72...power generation portion 80...outside Connecting device 310 Connecting portion 710 Supporting portions 31A, 32A High temperature side ends 31B, 32B Low temperature side ends 34A, 34B Electrodes

Claims (9)

An cathodic protection device for preventing corrosion of a steel material to be protected from corrosion by applying an anti-corrosion current from an anode material installed in a concrete structure to the steel material to be protected from corrosion in the concrete structure,
A power generation device having a power generation unit that generates power for supplying an anti-corrosion current from the anode material to the steel material to be anti-corrosion,
The power generation unit includes a thermoelectric conversion module in which n-type thermoelectric conversion elements and p-type thermoelectric conversion elements are alternately and electrically connected in series via electrodes,
The power generation unit is installed on a concrete surface of the concrete structure,
The thermoelectric conversion module is arranged on a support substrate made of an electrically insulating material,
The electrodes are arranged at both ends of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element in a heat conduction direction,
The low-temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element are supported by a support portion provided on the support substrate, and the high temperature of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element the side edge is out of contact with the supporting substrate;
Cathodic protection device for steel materials in concrete structures. An cathodic protection device for preventing corrosion of a steel material to be protected from corrosion by applying an anti-corrosion current from an anode material installed in a concrete structure to the steel material to be protected from corrosion in the concrete structure,
A power generation device having a power generation unit that generates power for supplying an anti-corrosion current from the anode material to the steel material to be anti-corrosion,
The power generation unit includes a thermoelectric conversion module in which n-type thermoelectric conversion elements and p-type thermoelectric conversion elements are alternately and electrically connected in series via electrodes,
The thermoelectric conversion module is arranged on a support substrate made of an electrically insulating material,
The electrodes are arranged at both ends of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element in a heat conduction direction,
The low-temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element are supported by a support portion provided on the support substrate, and the high temperature of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element The side end is out of contact with the support substrate,
The thermoelectric conversion module exhibits a π-type by alternately connecting the n-type thermoelectric conversion elements and the p-type thermoelectric conversion elements in series via the electrodes, and has a plurality of π-types arranged in parallel to each other. including the mold part,
In the plurality of π-shaped portions, a pair of π-shaped portions adjacent to each other are connected via a connecting portion, and the pair of π-shaped portions connected via the connecting portion protrude from the support substrate. The pair of π-shaped parts are bridged between the pair of support parts by being supported by a pair of support parts arranged apart from each other,
The low temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element included in a pair of π-shaped portions connected via the connection portion are supported by the support portion, and the high temperature side end portions are supported by the support portion. The ends are connected by the connecting part,
Cathodic protection device for steel materials in concrete structures. 3. The cathodic protection device for steel materials in concrete structures according to claim 1 , wherein said n-type thermoelectric conversion element and said p-type thermoelectric conversion element each have a phononic crystal structure. The n -type thermoelectric conversion element and the p -type thermoelectric conversion element are formed with a large number of pores having a diameter of submicro order or nano order penetrating through the element in the thickness direction.
The cathodic protection device for steel materials in a concrete structure according to any one of claims 1 to 3 . The cathodic protection device for steel materials in a concrete structure according to any one of claims 1 to 4 , wherein the power generation unit includes a plurality of the thermoelectric conversion modules. The cathodic protection device for steel materials in a concrete structure according to claim 5 , wherein said thermoelectric conversion modules are electrically connected in parallel or in series. The power generation unit is installed on the concrete surface of the concrete structure,
The cathodic protection device for steel materials in a concrete structure according to claim 2 . A cathodic protection method for protecting a steel material to be protected from corrosion by applying an anti-corrosion current from an anode material installed in a concrete structure to the steel material to be protected from corrosion in the concrete structure,
In a power generation unit having a thermoelectric conversion module in which n-type thermoelectric conversion elements and p-type thermoelectric conversion elements are alternately and electrically connected in series via electrodes, the n-type thermoelectric conversion element and the p-type thermoelectric conversion element A cathodic protection method in which electric power is generated by utilizing the temperature difference between the high-temperature side end and the low-temperature side end of the step, and the generated power is used to flow an anti-corrosion current from the anode material to the steel material to be anti-corrosion,
The power generation unit is installed on a concrete surface of the concrete structure,
The thermoelectric conversion module is arranged on a support substrate made of an electrically insulating material,
The electrodes are arranged at both ends of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element in a heat conduction direction,
The low-temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element are supported by a support portion provided on the support substrate, and the high temperature of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element the side edge is out of contact with the supporting substrate;
Cathodic protection method for steel materials in concrete structures. A cathodic protection method for protecting a steel material to be protected from corrosion by applying an anti-corrosion current from an anode material installed in a concrete structure to the steel material to be protected from corrosion in the concrete structure,
In a power generation unit having a thermoelectric conversion module in which n-type thermoelectric conversion elements and p-type thermoelectric conversion elements are alternately and electrically connected in series via electrodes, the n-type thermoelectric conversion element and the p-type thermoelectric conversion element A cathodic protection method in which electric power is generated by using the temperature difference between the high temperature side end and the low temperature side end in the electric corrosion protection method, and the electric power generated is used to flow the anticorrosion current from the anode material to the steel material to be anticorrosion,
The thermoelectric conversion module is arranged on a support substrate made of an electrically insulating material,
The electrodes are arranged at both ends of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element in a heat conduction direction,
The low-temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element are supported by a support portion provided on the support substrate, and the high temperature of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element The side end is out of contact with the support substrate,
The thermoelectric conversion module exhibits a π-type by alternately connecting the n-type thermoelectric conversion elements and the p-type thermoelectric conversion elements in series via the electrodes, and has a plurality of π-types arranged in parallel to each other. including the mold part,
In the plurality of π-shaped portions, a pair of π-shaped portions adjacent to each other are connected via a connecting portion, and the pair of π-shaped portions connected via the connecting portion protrude from the support substrate. The pair of π-shaped parts are bridged between the pair of support parts by being supported by a pair of support parts arranged apart from each other,
The low temperature side end portions of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element included in a pair of π-shaped portions connected via the connection portion are supported by the support portion, and the high temperature side end portions are supported by the support portion. The ends are connected by the connecting part,
Cathodic protection method for steel materials in concrete structures.

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