Thermoelectric power generation module

Abstract

To provide a thermoelectric power generation module with excellent thermoelectric power generation efficiency using a flexible substrate with good thermal conductivity. [Solution] A thermoelectric power generation module comprising: an anodized aluminum substrate having an anodized layer on one side of an aluminum plate and being flexible; a plurality of lower electrodes arranged on the side of the anodized aluminum substrate having the anodized layer; a thermoelectric conversion material arranged on the side of the lower electrodes opposite to the side with the anodized layer; and an upper electrode arranged on the side of the thermoelectric conversion material opposite to the lower electrode, wherein the thermoelectric conversion material is connected in series by the upper electrode and the lower electrode, the anodized aluminum substrate is fixed in contact with a heating element or heat sink, and both ends of the upper electrode of the thermoelectric conversion material connected in series have conductors for extracting the voltage generated by the thermoelectric conversion material as power.

Description

Technical Field

[0001] The present disclosure relates to a thermoelectric power generation module.

Background Art

[0002] In recent years, attention has been focused on the utilization of renewable energy and clean energy in response to the issues of stable energy supply and the transition to a decarbonized society. Thermoelectric power generation has attracted attention as one aspect of clean energy. Thermoelectric power generation is a mechanism that converts thermal energy into electrical energy and generates electricity when heat moves from a high-temperature part to a low-temperature part. Therefore, it has the characteristic that clean power generation can be performed in various applications according to the location where there is a temperature difference, such as natural heat sources (geothermal heat, ocean heat, human body heat, solar heat, etc.) and artificial heat sources (industrial waste heat, automobile waste heat, waste incinerator waste heat, etc.). In thermoelectric power generation, it is possible to generate electricity with a temperature difference of about several tens of K when actually generating electricity, and the range of heat source temperatures that can generate electricity extends from -200°C to about 2000°C. Also, when generating electricity, since there are no mechanical moving parts, it is also an advantage that problems such as component wear and deterioration rarely occur.

[0003] <​​​​​​​​​​​​Compared to an aluminum plate, the resistance is about 1 / 1000th, and because the heat-receiving part acts as a thermal resistance, it is not possible to provide a sufficient temperature difference to the thermoelectric conversion material, and a large electromotive force cannot be expected. A thermoelectric power generation module has been proposed that is flexible and can be used in vehicle exhaust pipes, comprising a graphite sheet with an insulating layer formed on it, a substrate having a specific coefficient of thermal expansion, two spaced-apart lower electrodes formed on the surface of the insulating layer of the substrate, an n-type thermoelectric conversion layer and a p-type thermoelectric conversion layer formed on the surfaces of the two lower electrodes, and an upper electrode connecting these thermoelectric conversion layers, preferably having a flexible upper electrode (see Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-225346 [Overview of the project] [Problems that the invention aims to solve]

[0005] Graphite sheets are known to have high thermal conductivity under certain conditions. However, in the thermoelectric conversion module described in Patent Document 1, the upper electrode is flexible, which limits the curvature of the module and presents problems such as the difficulty in selecting and manufacturing materials for the flexible upper electrode.

[0006] One embodiment of this disclosure aims to solve the problem of providing a thermoelectric power generation module with excellent thermoelectric power generation efficiency using a flexible substrate with good thermal conductivity. [Means for solving the problem]

[0007] The following embodiments are included as specific means for solving the above problems. <1> A thermoelectric power generation module comprising: an anodized aluminum substrate having an anodized layer on one side of an aluminum plate and being flexible; a plurality of lower electrodes disposed on the side of the aluminum substrate having the anodized layer; a thermoelectric conversion material disposed on the side of the lower electrodes opposite to the side with the anodized layer; and an upper electrode disposed on the side of the thermoelectric conversion material opposite to the lower electrode, wherein the thermoelectric conversion material is connected in series by the upper electrode and the lower electrode, the aluminum substrate is fixed in contact with a heating element or heat sink, and both ends of the upper electrode of the series-connected thermoelectric conversion material have conductors for extracting the voltage generated by the thermoelectric conversion material as power. <2> The thermoelectric conversion material includes a p-type thermoelectric conversion material and an n-type thermoelectric conversion material. <1> The thermoelectric power generation module described above. <3> The lower electrode is one or more selected from an indium layer, an indium-containing alloy layer, and a laminate having indium layers on both sides of a copper layer. <1> or <2> The thermoelectric power generation module described above.

[0008] <4> The total thickness of the anodized aluminum substrate is 0.3 mm to 1.0 mm, and the thickness of the anodized layer is 15 μm to 30 μm. <1> ~ <3> A thermoelectric power generation module as described in one of the following. <5> The side of the anodized aluminum substrate opposite to the side having the anodized layer is used in contact with a curved heating element or heat sink. <1> ~ <4> A thermoelectric power generation module as described in one of the following. <6> The thermoelectric conversion material is connected in series via the upper electrode in a direction perpendicular to the curvature direction of the curved heating element. <1> ~ <5> A thermoelectric power generation module as described in one of the following. [Effects of the Invention]

[0009] According to one embodiment of the present disclosure, a thermoelectric power generation module with excellent thermoelectric power generation efficiency is provided, using a flexible substrate with good thermal conductivity. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a partial schematic diagram showing one embodiment of the thermoelectric conversion material portion in the thermoelectric power generation module of this disclosure. [Figure 2] Figure 2 is a partial schematic diagram showing one embodiment of a thermoelectric element in the thermoelectric power generation module of this disclosure, which is a laminate comprising a lower electrode, a thermoelectric conversion material, and an upper electrode. [Figure 3] Figure 3 is a partially schematic diagram showing one embodiment of an aluminum substrate in the thermoelectric power generation module of the present disclosure. [Figure 4] Figure 4 is a schematic diagram showing one embodiment of the thermoelectric power generation module of this disclosure. [Figure 5A] Figure 5A is a schematic plan view of the thermoelectric power generation module shown in Figure 4. [Figure 5B] Figure 5B is a model diagram showing one embodiment of a cylindrical heating element or heat sink to which the thermoelectric power generation module shown in Figure 5 is attached. [Figure 6] Figure 6 is a graph showing the relationship between the heat supplied and the amount of electricity generated by that heat in the thermoelectric power generation modules of Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0011] The thermoelectric power generation module of this disclosure will be described in detail below. The requirements described below may be based on a typical embodiment of this disclosure, but this disclosure is not limited to such embodiments and may be modified as appropriate within the scope of the purposes of this disclosure.

[0012] In this disclosure, a numerical range indicated using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, "normal temperature" or "room temperature" refers to the ambient temperature in a state where temperature is not controlled, usually in the range of 20°C to 35°C, and "normal temperature" or "room temperature" under experimental conditions refers to 25°C unless otherwise specified. In the present disclosure, the thickness of each layer is a value measured using a micrometer unless otherwise specified. In the present disclosure, the "ductility" of the anodic aluminum oxide substrate refers to the property that even when the anodic aluminum oxide substrate is bent to a curvature radius of 5 mm by stress, the anodic oxide layer and the aluminum plate do not peel off.

[0013] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved. Components denoted by the same reference numerals in each drawing mean the same components. For overlapping components and reference numerals in each drawing, the description may be omitted. The ratio of dimensions in the drawings does not necessarily represent the ratio of actual dimensions.

[0014] [Thermoelectric power generation module] The thermoelectric power generation module of the present disclosure (hereinafter also referred to as "the module of the present disclosure") includes an anodic aluminum oxide substrate having an anodic oxide layer on one surface of aluminum and having ductility, a plurality of lower electrodes disposed on the surface of the aluminum substrate having the anodic oxide layer, a thermoelectric conversion material disposed on the side of the lower electrode opposite to the anodic oxide layer side, and an upper electrode disposed on the side of the thermoelectric conversion material opposite to the lower electrode. The thermoelectric conversion materials are connected in series by the upper electrode and the lower electrode. The aluminum substrate is fixed in contact with a heating body or a heat dissipating body. Conductive wires for taking out the voltage generated by the thermoelectric conversion materials as electric power are provided at both end portions of the upper electrode of the thermoelectric conversion materials connected in series. In the following, the laminate comprising the lower electrode, thermoelectric conversion material, and upper electrode may be referred to as a thermoelectric conversion element.

[0015] Figure 1 shows a partial schematic diagram of one embodiment of module 10 of this disclosure. Module 10 has a flexible aluminum plate 12, and the aluminum plate 12 has an anodic oxide layer 14 on one side that functions as an insulating layer. A lower electrode (also called a mounting electrode) 16 is placed on one side of the anodic oxide layer 14, and a p-type thermoelectric conversion material 18 and an n-type thermoelectric conversion material 20 are provided on the surface of the lower electrode 16. Figure 1 shows an embodiment having two laminates, each having a p-type thermoelectric conversion material 18 and an n-type thermoelectric conversion material 20 on the lower electrode 16. The p-type thermoelectric conversion material 18 and the n-type thermoelectric conversion material 20 provided on the adjacent lower electrode 16 are electrically connected by an upper electrode (also called a connecting electrode) 22 to form a thermoelectric conversion element 24. Figure 2 is a schematic partial diagram showing one embodiment of a thermoelectric element 24, which is a laminate comprising a lower electrode 16, a p-type thermoelectric material 18, an n-type thermoelectric material 20, and an upper electrode 22. This laminate is also called a Π-shaped element. Multiple of these laminates 24 are connected in series via the upper electrode 22 to constitute a thermoelectric power generation module 10.

[0016] In the module of this disclosure, multiple sets of p-type thermoelectric materials and n-type thermoelectric materials are connected in series, for example, by upper and lower electrodes, so that the voltage generated by the thermoelectric elements is added up and increased. When an external load is connected through the conductors of the module of this disclosure, which has multiple sets of thermoelectric elements connected in series, current flows and an output is obtained.

[0017] The following describes the constituent elements of each module of this disclosure.

[0018] (Anodized aluminum substrate) As shown in Figure 1, the anodized aluminum substrate 12 in the module of this disclosure has an anodized layer 14 on one side of an aluminum plate 12A. The anodic oxide layer can be formed by performing anodic oxidation on an aluminum plate, which is a metal substrate. Anodizing can be performed on an aluminum plate by using an oxalic acid aqueous solution, a phosphoric acid aqueous solution, or the like as an electrolyte, and applying a voltage of 40V to 70V for 10 to 90 minutes while maintaining the bath temperature at 25°C to 40°C.

[0019] From the viewpoint of achieving both flexibility and insulation, the total thickness of the anodized aluminum substrate (i.e., the total thickness of the aluminum plate and the anodized layer) is preferably in the range of 0.3 mm to 1.0 mm, and the thickness of the anodized layer on the aluminum substrate is preferably 15 μm to 30 μm. More preferably, the total thickness of the aluminum substrate is in the range of 0.5 mm to 0.8 mm, the thickness of the anodized layer is more preferably 16 μm to 25 μm, and even more preferably 16 μm to 22 μm.

[0020] The anodic oxide layer is a layer formed directly on the aluminum plate and is an aggregate of porous layers. Figure 3 shows a schematic diagram of the anodic oxide layer 14 formed on the aluminum plate 12A in the anodic oxide aluminum substrate 12. As shown in the schematic diagram, the anodic oxide layer 14, when viewed from the surface (the side opposite to the side in contact with the aluminum plate 12), is an aggregate of hexagonal film cells 28, each having a micropore 26 in the center. The size of the formed film cells and the size of the micropore in the center can be appropriately controlled by the electrolysis conditions.

[0021] From the viewpoint of maintaining the insulating properties of the aluminum substrate in this disclosure, it is preferable that the diameter of the film cell 28 is in the range of 100 nm to 300 nm, the diameter of the micropore 26 is in the range of 10 nm to 20 nm, and the height of the film cell 28, i.e., the thickness of the anodic oxide layer 14, is 16 μm to 22 μm. The micropores 26 formed in the center of the film cell 28 do not penetrate the film cell 28, and there is a gap between the bottom surface of the micropores 26 and the aluminum plate 12. It is believed that the anodic oxide coating portion between the micropores 26 formed in the film cell 28 that constitutes the anodic oxide layer 14 and the aluminum plate 12A contributes to ensuring insulation.

[0022] According to the inventors' research, it has been confirmed that an anodic oxidation layer of approximately 16 μm can be formed by using a 0.3 M oxalic acid aqueous solution as the anodic oxidation conditions, with a bath temperature of 30°C and an applied voltage of 50 V, and performing anodic oxidation on aluminum for 25 minutes. From the perspective of achieving a better balance between flexibility and insulation in an anodized coating, using a 0.3M oxalic acid aqueous solution, an anodized layer that maintains insulation properties can be formed by performing anodizing for 25 to 60 minutes. When using a 0.3M phosphoric acid aqueous solution, an anodized layer that maintains insulating properties is formed by performing anodizing for approximately 12 times longer than when using a 0.3M oxalic acid aqueous solution.

[0023] When focusing on the thickness of the anodized layer, from the viewpoint of exhibiting good flexibility, when the thickness of the anodized layer derived from the oxalic acid aqueous solution is in the range of 15 μm to 20 μm, cracks due to bending stress are unlikely to occur even when placed on a curved surface with a radius of curvature of 5 mm to 16 mm. Furthermore, at a radius of curvature of 30 mm, some cracks occur, but it has been confirmed that delamination between the anodized layer and the aluminum plate does not occur, and the insulating properties are not impaired. In the case of anodized films derived from an aqueous phosphoric acid solution, using a 0.3M aqueous phosphoric acid solution, an anodized film of 1μm to 2μm thickness is formed after 60 minutes of anodizing treatment. Even when placed on a curved surface with a radius of curvature of 5mm, cracks due to bending stress are unlikely to occur. Furthermore, at radii of curvature of 10mm to 30mm, some cracks may occur, but it has been confirmed that delamination between the anodized layer and the aluminum plate does not occur, and the insulating properties are not impaired.

[0024] The flexibility of the aluminum substrate under bending stress will be evaluated under the following conditions. The evaluation equipment used includes the AUTOGRAPH AG-I (Shimadzu Corporation), the ECLIPSE L200N optical microscope (Nikon Corporation), and the JCM-6000PLUS scanning electron microscope (JEOL Ltd.), and the evaluation was performed under conditions of curvature radii of 5 mm to 20 mm. The evaluation method involves observing the surface morphology after the three-point bending test and checking for delamination between the bent anodic oxide film (anodic oxide layer) and the aluminum plate using an optical microscope, scanning electron microscope, etc. Five samples were evaluated, and the median value was used as the evaluation result.

[0025] (Lower electrode) The module of this disclosure comprises a plurality of lower electrodes (mounted electrodes) on the side of the aluminum substrate that has an anodized layer. A soft material, such as a soft metal like indium, is preferred as the lower electrode. Alternatively, a thin metal electrode having a resistance value similar to that of indium may be used. In particular, from the viewpoint of having flexibility that can follow the flexibility of the aluminum substrate, it is preferable that the lower electrode be one or more selected from an indium layer, an indium-containing alloy layer, and a laminate having indium layers on both sides of a copper layer. The indium layer is soft and conforms well to the shape of the anodized layer formed on the aluminum plate, even when the module of this disclosure is placed on a curved surface. It is also resistant to peeling and possesses the necessary conductivity. The lower electrode can be provided on the surface of the anodic oxide layer by soldering. There are no particular restrictions on the method of forming the lower electrode. For example, it can be formed using a general-purpose soldering iron by depositing a gold thin film onto an anodized aluminum support. Alternatively, the lower electrode can be formed without a gold deposition film by using an ultrasonic soldering iron. The thickness of the lower electrode is not particularly limited as long as it has sufficient conductivity, but from the viewpoint of flexibility, it can be 0.2 mm to 0.5 mm thick, and 0.3 mm to 0.4 mm is preferred. Furthermore, the size (size in plan view) of the lower electrode formed on the anodized aluminum substrate can be appropriately selected according to the installation location of the module, its intended use, and the required electromotive force. For example, in one embodiment where the module is applied to a heat dissipation pipe with a curvature of 10 mm, the lower electrode can be 3 mm to 5 mm in width and 7 mm to 9 mm in length.

[0026] (Thermoelectric conversion materials) In the module of this disclosure, a thermoelectric conversion material is provided on the surface of the lower electrode opposite to the side in contact with the anodic oxide layer. Thermoelectric materials are generally elements that generate an electromotive force by joining two different metals or semiconductors to create a temperature difference across their ends. From the viewpoint of obtaining a larger potential difference, it is preferable that the thermoelectric material includes both a p-type thermoelectric material and an n-type thermoelectric material. By having a thermoelectric conversion material that is a pair of thermoelectric conversion elements including a p-type thermoelectric conversion material and an n-type thermoelectric conversion material, the heat supplied to the module of this disclosure can be converted into electricity more efficiently. As the p-type thermoelectric conversion material and n-type thermoelectric conversion material, known p-type semiconductors and n-type semiconductors can be used. The materials constituting the thermoelectric conversion material are appropriately selected depending on the temperature applied to the module. For example, bismuth-tellurium (Bi-Te) systems may be selected from room temperature to 500K (227°C), lead-tellurium (Pb-Te) systems from 500K to 800K (527°C), and silicon-germanium (Si-Ge) systems from 800K to 1000K (727°C). Commercially available reagents may be used to form p-type and n-type thermoelectric materials. Examples of commercially available reagents include bismuth telluride-based compounds and Co-Sb-based skutterudite compounds.

[0027] p-type and n-type thermoelectric materials are formed by coating the lower electrode material onto an aluminum substrate and then arranging it while heating. According to the above method, the bottom portions of the p-type thermoelectric material and the n-type thermoelectric material are arranged to be embedded in the lower electrode. Therefore, the preferred thickness of the lower electrode of 0.2 mm to 0.5 mm mentioned earlier is the thickness of the region without the p-type and n-type thermoelectric materials, and the thickness of the lower electrode in the portion where the p-type and n-type thermoelectric materials are embedded is approximately 0.02 mm to 0.05 mm. Even at this thickness, the conductivity of the lower electrode is not impaired, and it is considered that stable fixation between the p-type and n-type thermoelectric materials and the lower electrode is achieved.

[0028] There are no particular restrictions on the size of the p-type and n-type thermoelectric materials. The size of the p-type and n-type thermoelectric conversion materials is determined appropriately by the area ratio based on the thermal conductivity and electrical resistivity of each material. If the materials have similar thermal conductivity and electrical resistivity, a rectangular prism-shaped material with dimensions of 1mm to 3mm in width, 1mm to 3mm in length, and 2mm to 5mm in height is generally preferred. If the radius of curvature of the heat source is small, it is preferable to reduce the above values, i.e., to use a smaller size.

[0029] (Top electrode) The module of this disclosure includes an upper electrode. By connecting thermoelectric conversion elements, which are mounted on the surface of the lower electrode, with the upper electrode, the voltage generated by individual thermoelectric materials can be increased. There are no particular limitations on the configuration of the upper electrode; any conductive material can be used without restriction. Examples of upper electrodes include copper foil and aluminum foil. From the viewpoint of heat dissipation and reduction of electrical loss, copper foil with a thickness of about 0.5 mm is preferably used for the upper electrode. The size of the upper electrode is not particularly limited as long as it is large enough to connect adjacent thermoelectric conversion materials, but from the viewpoint of preventing short circuits, the width can be set to about 3 mm to 4 mm and the length to about 6.5 mm to 7.5 mm to match the thermoelectric conversion material.

[0030] The module of this disclosure has a plurality of laminates on one side of an aluminum substrate, each laminate having a thermoelectric conversion material and an upper electrode described later on the lower electrode surface, i.e., a plurality of thermoelectric conversion elements. The thermoelectric conversion materials in the plurality of thermoelectric conversion elements are connected to adjacent thermoelectric conversion elements in the laminate by the upper electrodes described later, thereby increasing the current or voltage by addition. In the module of this disclosure, when heat is applied to the aluminum substrate, heat is transferred to the thermoelectric element having a lower electrode, a thermoelectric conversion material, and an upper electrode via the aluminum substrate, which has good thermal conductivity. The application of heat generates a voltage in the thermoelectric material due to the Seebeck effect. That is, each individual p-type, n-type, or other thermoelectric conversion material becomes a so-called miniature battery.

[0031] Since the module of this disclosure uses a flexible anodized aluminum substrate, the side of the aluminum substrate opposite to the side having the anodized layer can be used in contact with a curved heating element or heat sink. When the module of this disclosure is brought into contact with a heating element or heat sink on a curved surface, it is preferable that the thermoelectric conversion material be connected in series by the upper electrode in a direction perpendicular to the curvature direction of the curved heating element, from the viewpoint of achieving better shape conformity to the curved surface.

[0032] By connecting thermoelectric materials in series using upper and lower electrodes, the voltages are added together and become larger. Therefore, by connecting an external load to the module of this disclosure via conductors provided at both ends of the upper electrode of the module of this disclosure, which are used to extract the voltage generated by the thermoelectric materials as power, current flows and output is obtained. On the other hand, the above current value increases when thermoelectric materials are connected in parallel. Therefore, the power output to the external load should be determined by deciding whether voltage or current is dominant, so as to obtain an output suitable for the application of the module disclosed herein. Thermoelectric conversion materials obtain a temperature difference, i.e., a heat flow, whether they receive heat by contacting a heat-generating element and dissipate it to the surroundings, or receive heat from the surroundings and dissipate it by contacting a heat sink that is at a lower temperature than the surroundings. For this reason, the thermoelectric power generation module of this disclosure can obtain an electromotive force by contacting a heat-generating element or a heat sink.

[0033] (conductor) The module of this disclosure includes a conductor for recovering the electric current generated by a thermoelectric material. The conductors can be selected and used from known types as appropriate. The conductors are provided at both ends of a plurality of thermoelectric materials connected in series or parallel, and supply power generated from the module of this disclosure to the outside.

[0034] Figure 4 is a schematic diagram showing one embodiment of the module 10 of this disclosure, which is formed by connecting a plurality of thermoelectric materials in series. As shown in Figure 4, the module 10 has a lower electrode 16, a p-type thermoelectric material 18, and an n-type thermoelectric material 20 on an anodized aluminum substrate 12 made of an aluminum plate 12A on which an anodized layer 14 is formed. Adjacent p-type thermoelectric material 18 and n-type thermoelectric material 20 have a plurality of thermoelectric elements 24 connected in series by an upper electrode 22 and a lower electrode 16. Output wires 30 are provided at both ends of the upper electrode 22 of the series-connected thermoelectric elements 24 to extract the voltage generated by the thermoelectric material as power.

[0035] Figure 5A is a schematic plan view of the thermoelectric power generation module shown in Figure 4. The thermoelectric power generation module 10 shown in Figure 4 is connected in series via the lower electrode 16 and the upper electrode 22, as shown in the schematic plan view in Figure 5A. In a preferred embodiment, the thermoelectric power generation module 10 has a thermoelectric conversion material (not shown) connected in series via a lower electrode 16 and an upper electrode 22 in a direction perpendicular to the curvature direction of a curved heating element or heat sink. Figure 5B shows a model diagram illustrating one embodiment of a cylindrical heating element or heat sink to which the thermoelectric power generation module 10 shown in Figure 5A is attached. The module 10 shown in Figure 4 can be attached by directly contacting the anodized aluminum substrate 12 of the module 10 with the curved surface of the cylindrical heating element or heat sink 32 as schematically shown in Figure 5B, in the direction indicated by the arrow in the figure. Since the lower electrode 16 is in close proximity to the heating element or heat sink 32 and in close contact with the aluminum oxide substrate 12, even if it is connected parallel to the curvature direction, it is less affected by the curved surface compared to the upper electrode 22. Furthermore, as described above, in one embodiment, the lower electrode 16 contains a soft metal such as indium, which improves the conformability of the lower electrode to the curved surface. On the other hand, the upper electrode 22 is located at a distance from the heating element or heat sink 32 and is susceptible to the effects of curved surfaces. Therefore, it is preferable that it be connected in series in a direction perpendicular to the curvature direction. In Figure 5B, the thermoelectric conversion material is mainly connected in series via the upper electrode 22 in a direction perpendicular to the curvature direction of the curved heating element or heat sink 32, as indicated by the arrows. This arrangement reduces the influence of curved surfaces on the performance of the module 10.

[0036] The module of this disclosure can be installed on curved surfaces, offering a high degree of flexibility in installation locations. For this reason, it can be installed, for example, on high-temperature pipes in factories, pipes for supplying hot springs, and household hot water piping, and these can be used as heating elements to generate electromotive force without requiring any special energy. Furthermore, the module of this disclosure can be installed in pipes through which chilled water flows, metal pillars driven into the ground, etc., and by using these as low-temperature heat sources, i.e., heat radiators, electromotive force can be obtained without requiring any special energy. As previously described, the module of this disclosure has a low environmental impact, can utilize energy efficiently, and offers a high degree of flexibility in installation location, thus having a wide range of applications. [Examples]

[0037] The manufacturing method of this disclosure will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing procedures, etc., shown in the following examples can be modified as appropriate without departing from the spirit of this disclosure. Therefore, the thermoelectric power generation module relating to this disclosure should not be interpreted restrictively by the specific examples shown below. Unless otherwise specified, the percentages "%" below refer to mass.

[0038] The module related to this disclosure will be explained in more detail below.

[0039] [Fabrication of anodized aluminum substrates] An anodized aluminum substrate was obtained by anodic oxidation of one side of a 99.99% pure aluminum plate (thickness: 0.5 mm, size: 25 mm x 25 mm) using a 0.3 M oxalic acid aqueous solution as the electrolyte, with an electrode distance of 20 mm, a bath temperature of 30°C, and an applied voltage of 50 V, over a period of 25 minutes, forming an anodized layer of approximately 16 μm.

[0040] [Evaluation of the flexibility of anodized aluminum substrates] The obtained anodized aluminum substrates were evaluated using an AUTOGRAPH AG-I (Shimadzu Corporation) under conditions of curvature radius from 5 mm to 30 mm. As part of the evaluation, the surface morphology after the three-point bending test and the presence or absence of delamination between the bent anodized film (anodic oxide layer) and the aluminum plate were observed using an optical microscope ECLIPSE L200N (Nikon Corporation) and a scanning electron microscope JCM-6000PLUS (JEOL Ltd.). Three samples were evaluated for each method.

[0041] As a result, no cracks occurred at a radius of curvature of 30 mm, but cracks did occur at radii of curvature between 5 mm and 16 mm. However, no delamination of the anodic oxide layer was observed under any of the conditions.

[0042] The insulating properties of the anodized aluminum substrate were evaluated by placing aluminum electrodes between the anodized and unanodized surfaces of an aluminum plate and measuring the voltage V-current I characteristics using an ultra-high resistance / micro-current meter 8340A (ADC Corporation). As a result, the obtained anodized aluminum substrates exhibited insulating properties under all anodizing conditions.

[0043] [Formation of the lower electrode and thermoelectric conversion element] On the anodized layer side of the obtained anodized aluminum substrate, indium was applied as the lower electrode material in an amount that resulted in a film thickness of 0.3 mm, using an ultrasonic soldering iron, in accordance with the shape of the lower electrode (size: 5 mm x 11 mm). A p-type thermoelectric conversion material and an n-type thermoelectric conversion material were placed on the coated surface while being heated to approximately 200°C. When the thermoelectric conversion material was placed on the lower electrode material, it penetrated into the lower electrode layer at the placement location, and the thickness of the lower electrode in the region containing the thermoelectric conversion material was measured with a micrometer and found to be 0.032 mm. Two rows of lower electrodes and thermoelectric conversion elements were formed in the width direction and one row in the length direction of the aluminum substrate.

[0044] [Formation of the upper electrode] The two thermoelectric materials formed as described above were joined in series using an upper electrode. The upper electrode was made of copper foil with a thickness of 0.1 mm and a size of 6 mm x 10 mm coated with indium. The thermoelectric elements were connected in series by connecting a p-type thermoelectric material and an n-type thermoelectric material formed on different lower electrodes of adjacent thermoelectric materials.

[0045] [Wire connection] By connecting wires to both ends of the upper electrodes of the thermoelectric conversion elements connected in series, the thermoelectric power generation module of Example 1 was obtained.

[0046] [Evaluation of thermoelectric power generation modules] The thermoelectric power generation module of Example 1 obtained was attached to a heat source with a radius of curvature of 20 mm, and the conductors of the thermoelectric power generation module were connected to an external electromotive force measuring device. The temperature of the hot water flowing through the pipe was changed to 40°C to 80°C, and after maintaining the temperature for 20 minutes, the temperature of the flowing hot water and the electromotive force were measured using a memory HiLogger LR8431 (HIOKI E.C. Corporation). The current I-voltage V characteristics were measured using a 2400 source meter (Keithley, now Tektronix & Fluke Corporation) and a 7352 digital multimeter (ADC Corporation). The effective maximum output (Pmax) in Figure 6 is calculated using the following formula. Formula:P max =E 2 / (4r) In the above equation, E is the thermoelectric power and r is the internal resistance.

[0047] The results are shown in Figure 6. Figure 6 is a graph showing the relationship between the upper electrode temperature (electrode temperature on the heat source side) and the effective maximum output, which is the amount of electricity generated by heat, in the thermoelectric power generation module of Example 1. As is clear from Figure 4, the thermoelectric power generation module of Example 1 provides an electromotive force corresponding to the temperature of the heating element, and it was found that the higher the temperature, the higher the output.

[0048] [Comparative Example 1] A thermoelectric power generation module having two thermoelectric conversion elements was obtained in the same manner as in Example 1, except that a 0.5 mm thick alumina substrate (aluminum oxide substrate) was used instead of the anodized aluminum substrate of Example 1, and was evaluated under the same conditions as in Example 1. Alumina is hard and inflexible, so when it was attached to a heat source pipe with a radius of curvature of 20 mm, the contact area was small. The thermoelectric power generation module of Comparative Example 1 was installed and evaluated in the same manner as in Example 1. The results are shown in Figure 4. As is clear from Figure 4, the thermoelectric power generation module of Comparative Example 1 had a narrow contact area, so it was not possible to obtain an electromotive force corresponding to the temperature, and it was found that the output was extremely low compared to Example 1. [Explanation of Symbols]

[0049] 10 Thermoelectric power generation modules 12 Anodized aluminum substrate 12A Aluminum Plate 14. Anodized layer 16 Lower electrode 18 p-type thermoelectric materials 20 n-type thermoelectric materials 22 Upper electrode 24. Laminate (thermoelectric conversion element) 26 Micropore 28 coated cells 30 conductor 32 Heat-generating element or heat sink (model diagram)

Claims

1. An anodized aluminum substrate having an anodized layer on one side of an aluminum plate and being flexible, A plurality of lower electrodes are arranged on the side of the anodized aluminum substrate that has the anodized layer. A thermoelectric conversion material is disposed on the side of the lower electrode opposite to the anodic oxide layer, and The thermoelectric conversion material is provided with an upper electrode positioned on the opposite side from the lower electrode, The thermoelectric conversion material is connected in series by an upper electrode and a lower electrode. The anodized aluminum substrate is fixed in contact with a heating element or heat sink. A thermoelectric power generation module having conductors at both ends of the upper electrodes of the thermoelectric materials connected in series for extracting the voltage generated by the thermoelectric materials as power.

2. The thermoelectric power generation module according to claim 1, wherein the thermoelectric conversion material includes a p-type thermoelectric conversion material and an n-type thermoelectric conversion material.

3. The thermoelectric power generation module according to claim 1, wherein the lower electrode is one or more selected from an indium layer, an indium-containing alloy layer, and a laminate having indium layers on both sides of a copper layer.

4. The thermoelectric power generation module according to claim 1, wherein the total thickness of the anodized aluminum substrate is 0.3 mm to 1.0 mm, and the thickness of the anodized layer is 15 μm to 30 μm.

5. The thermoelectric power generation module according to claim 1, wherein the side of the anodized aluminum substrate opposite to the side having the anodized layer is used in contact with a curved heating element or heat sink.

6. The thermoelectric power generation module according to claim 1, wherein the thermoelectric conversion material is connected in series via the upper electrode in a direction perpendicular to the curvature direction of the curved heating element.

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