Thermoelectric conversion module

Abstract

To provide technique enabling thermoelectric conversion efficiency to be improved in a thermoelectric conversion module.SOLUTION: A thermoelectric conversion module comprises a base material and a thermoelectric conversion member spirally wrapped around the base material. One side portion of a spiral body formed by the thermoelectric conversion member is formed as a heat receiving portion. The other side portion opposite to the one side portion with the base material interposed therebetween is formed as a heat radiating portion. In the base material, a heat insulating hole forming a heat insulating layer extends along an extending direction of the base material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion module. [Background technology]

[0002] Conventionally, thermoelectric conversion elements that generate electromotive force by connecting a P-type semiconductor and an N-type semiconductor and applying a temperature difference between both ends through the Seebeck effect, and thermoelectric conversion modules equipped with such elements have been widely used. In this regard, thermoelectric conversion elements made of fibrous carbon nanotubes are known (for example, Patent Document 1). Thermoelectric conversion elements are used, for example, to generate electricity by utilizing waste heat from automobiles, factories, homes, body heat, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-207766 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-207392 [Patent Document 3] Japanese Patent Application Publication No. 2017-195232 [Patent Document 4] Patent No. 4620183 [Patent Document 5] Patent No. 7183794 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to generate a large amount of power using a thermoelectric conversion element, it is necessary to ensure a large temperature difference between the heat-receiving side and the heat-dissipating side of the thermoelectric conversion element. If a sufficient temperature difference cannot be ensured, there is a problem in that the thermoelectric conversion efficiency decreases.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a technology that enables efficient power generation in a thermoelectric conversion module without reducing thermoelectric conversion efficiency even when the temperature difference between the heat receiving side and the heat dissipation side is small. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention employs the following means. That is, the gist of the present invention is as follows. [1] A thermoelectric conversion module having a heat receiving portion and a heat dissipating portion, which generates electricity by utilizing a temperature difference between the heat receiving portion and the heat dissipating portion, A substrate; a thermoelectric conversion member spirally wound around the substrate, one side of the spiral formed by the thermoelectric conversion member is formed as the heat receiving portion, and the other side opposite to the one side across the base material is formed as the heat dissipation portion, The base material has heat insulating holes that form a heat insulating layer extending along the extending direction of the base material. Thermoelectric conversion module. [2] the thermoelectric conversion member includes a plurality of P-type portions formed as P-type semiconductors and a plurality of N-type portions formed as N-type semiconductors, the P-type portions and the N-type portions are alternately arranged and continuously formed in the extension direction of the thermoelectric conversion member, The P-type portion and the N-type portion are arranged such that one end of each is included in the heat receiving portion and the other end of each is included in the heat dissipation portion. [1] The thermoelectric conversion module according to [1]. [3] The thermoelectric conversion member is a carbon nanotube yarn formed into a thread shape from carbon nanotubes. The thermoelectric conversion module according to [1] or [2]. [4] the thermoelectric conversion member is formed of a nonwoven fabric of carbon nanotubes; A thermoelectric conversion module according to any one of [1] to [3]. [5] The substrate is composed of a plurality of members, The heat insulating holes are formed between the plurality of members. A thermoelectric conversion module according to any one of [1] to [4]. [6] the base material is configured to include a first member and a second member having a thermal conductivity higher than that of the first member, The second member is disposed closer to the heat dissipation portion than the first member. A thermoelectric conversion module according to any one of [1] to [5]. [7] The base material has a cooling flow path formed therein, the cooling flow path extending along the extending direction of the base material and allowing a cooling medium to flow therethrough. A thermoelectric conversion module according to any one of [1] to [6]. [8] The cooling flow path is formed between the heat insulating hole and the heat dissipation portion. [7] The thermoelectric conversion module according to [7]. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve the thermoelectric conversion efficiency in a thermoelectric conversion module. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically showing a state in which a thermoelectric conversion module according to Embodiment 1 is used. [Figure 2] 1 is a right side view of a thermoelectric conversion module according to a first embodiment. [Figure 3] 1 is a top view of a thermoelectric conversion module according to a first embodiment. [Figure 4] 1 is a diagram illustrating the configuration of a carbon nanotube yarn according to a first embodiment. FIG. [Figure 5]3 is a schematic diagram illustrating the relationship between a substrate and carbon nanotube yarns in the thermoelectric conversion module according to the first embodiment. FIG. [Figure 6] FIG. 2 is a perspective view of a substrate used in a thermoelectric conversion module according to a modified example of the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view schematically showing a state in which a thermoelectric conversion module according to a second embodiment is used. [Figure 8] FIG. 10 is a perspective view of a substrate used in a thermoelectric conversion module according to a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configurations described in the following embodiments are not intended to limit the technical scope of the invention unless otherwise specified. In this specification, "insulating" refers to electrical insulating properties unless otherwise specified.

[0010] <Embodiment 1> 1 to 3 are diagrams illustrating a thermoelectric conversion module 100 according to a first embodiment. As will be described in detail later, the thermoelectric conversion module 100 is configured by spirally winding a carbon nanotube yarn 2 around a substrate 1. FIG. 1 is a cross-sectional view schematically illustrating a state in which the thermoelectric conversion module 100 according to the first embodiment is in use. In FIG. 1, the up-down direction, left-right direction, and front-rear direction of the thermoelectric conversion module 100 are shown. The front-rear direction of the thermoelectric conversion module 100 is a direction perpendicular to the up-down direction and left-right direction. However, these directions are defined for convenience of explanation and are not intended to limit the orientation of the thermoelectric conversion module according to the present invention. In FIG. 1, a cross section perpendicular to the front-rear direction is illustrated. FIG. 2 is a right side view of the thermoelectric conversion module 100 according to the first embodiment. FIG. 3 is a top view of the thermoelectric conversion module 100 according to the first embodiment. In FIG. 1, the direction from the heat receiving portion 201 toward the heat dissipating portion 202 (downward in this embodiment) is referred to as a first direction D. The first direction D is the direction in which heat moves from the heat receiving portion 201 to the heat radiating portion 202 in the shortest distance.

[0011] [Overall configuration] As shown in FIGS. 1 to 3, the thermoelectric conversion module 100 has a generally rectangular pillar-like outer shape extending in the front-to-rear direction. The thermoelectric conversion module 100 is used while being disposed between a hot heat source 200 and a cold heat source 300 disposed above and below. The hot heat source 200 and the cold heat source 300 are heat sources for applying a temperature difference to the thermoelectric conversion module 100, with the hot heat source 200 having a higher temperature than the cold heat source 300. The thermoelectric conversion module 100 has a heat receiving section 201 that receives heat from the outside and a heat dissipation section 202 that dissipates heat to the outside. The heat receiving section 201 is formed on the upper part of the thermoelectric conversion module 100 so as to be in contact with the hot heat source 200, and the heat dissipation section 202 is formed on the lower part of the thermoelectric conversion module 100 so as to be in contact with the cold heat source 300. The heat receiving section 201 receives heat from the hot heat source 200, and the heat dissipation section 202 dissipates heat to the cold heat source 300, resulting in a temperature difference between the heat receiving section 201 and the heat dissipation section 202. As will be described in detail later, the thermoelectric conversion module 100 generates electricity by utilizing the temperature difference between the heat receiving section 201 and the heat dissipation section 202. The thermoelectric conversion module 100 may be worn on the human body when in use. In this case, the thermoelectric conversion module 100 can generate electricity by utilizing the temperature difference between the body temperature of the human body and the air temperature, with the human body being the hot heat source 200 and the atmosphere (air) being the cold heat source.

[0012] 1 to 3, the thermoelectric conversion module 100 includes a substrate 1, a carbon nanotube yarn 2 (an example of a "thermoelectric conversion member" according to the present invention), and an insulating wire 3. Each component of the thermoelectric conversion module 100 will be described below.

[0013] [Base material 1] The substrate 1 is a core material around which the carbon nanotube yarn 2 is wound. The substrate 1 is formed in a prismatic shape extending in the front-rear direction and having a substantially rectangular cross section. The substrate 1 has heat-insulating, insulating, and flexibility properties. For example, a flexible material with low thermal conductivity and electrical conductivity can be used for the substrate 1. The substrate 1 according to this embodiment is formed from silicone rubber and has heat-insulating, insulating, and flexibility properties. However, the material of the substrate 1 is not limited thereto. The substrate 1 can be formed from at least one of silicone rubber, nitrile rubber, styrene butadiene rubber, ethylene propylene rubber, natural rubber, fluororubber, polyimide, and cross-linked polyethylene, for example. The substrate according to the present invention does not need to be flexible and may be formed from, for example, a ceramic material. The substrate according to the present invention does not need to be entirely made of a material having heat-insulating and insulating properties. For example, the substrate may be formed by coating the surface of a core material with the above-mentioned material having heat-insulating and insulating properties. In this case, the configuration including the core material and the coating material corresponds to the "substrate." In addition, as long as heat insulation is ensured by the heat insulating holes described below, it is essential that the base material itself has heat insulation properties. The substrate does not have to be made of a heat insulating material. Furthermore, the shape of the substrate according to the present invention is not limited to a prism having a substantially rectangular cross section. The cross section of the substrate may be a polygon other than a rectangle, and the substrate may be formed in a cylindrical shape having a substantially circular cross section.

[0014] As shown in FIG. 1, the substrate 1 has a rectangular cross-sectional shape including a pair of opposing vertical sides 1a, 1b and a pair of opposing horizontal sides 1c, 1d. The substrate 1 is arranged so that the vertical sides 1a, 1b are parallel to the up-down direction. The vertical sides 1a, 1b are longer than the horizontal sides 1c, 1d. In other words, the cross-sectional shape of the substrate 1 is a rectangle with its longer sides in the direction from the heat receiving section 201 to the heat dissipation section 202 (first direction D). The cross-sectional shape of the substrate 1 may also be square. The horizontal side 1c of the substrate 1 contacts the hot heat source 200, and the horizontal side 1d contacts the cold heat source 300.

[0015] As shown in FIG. 1 , the base material 1 has hollow insulation holes 4 formed in the extension direction of the base material 1. The insulation holes 4 retain and retain an insulating medium, forming an insulating layer inside the insulation holes 4. In this embodiment, air is used as the insulating medium, and this air layer functions as the insulating layer. The cross-sectional shape of the insulation holes 4 is a rectangle elongated in the left-right direction. Furthermore, the insulation holes 4 are positioned closer to the heat receiving portion 201 than the center position of the base material 1 in the vertical direction, and extend continuously from one end to the other end in the extension direction of the base material 1. However, the shape and position of the insulation holes and the insulating medium according to the present invention are not limited to those described above. The cross-sectional shape of the insulation holes may be circular or may have various other shapes. The insulation holes may be positioned closer to the heat dissipation portion than the center position of the base material in the vertical direction, or may be positioned in the center. Furthermore, the insulation holes do not have to be formed across both ends of the base material, as long as they are formed in at least a portion of the region of the base material around which the thermoelectric conversion member is wrapped. The insulating holes may also be formed inside a cylindrical member such as a tube inserted into a hollow hole in the substrate. The insulating holes may also be pores in a porous material, in which case the porous material may be dispersed in the substrate, or the substrate itself may be a porous material. The insulating medium is not limited to air, but may also be krypton gas or argon gas. In addition, the insulating medium is not essential in the present invention. For example, a heat insulating layer may be formed by evacuating the inside of the insulating holes.

[0016] [Carbon nanotube yarn] The carbon nanotube yarn 2 is a flexible and conductive wire material formed by forming carbon nanotubes (also referred to as CNTs) into a thread-like shape. FIG. 4 is a diagram for explaining the configuration of the carbon nanotube yarn 2 according to the first embodiment. As shown in the enlarged view A1 of FIG. 4, the carbon nanotube yarn 2 contains a plurality of fibrous carbon nanotubes 211, which are bonded together by intermolecular attraction to form a single thread. The carbon nanotubes constituting the carbon nanotube yarn 2 may be multi-walled carbon nanotubes (MW carbon nanotubes), single-walled carbon nanotubes (SW carbon nanotubes), or a composite material in which these are mixed. The carbon nanotube yarn 2 may also be graphitized. By electrically heating the carbon nanotube yarn 2 placed in a graphitization furnace, a peak at around 1590 cm-1 in Raman spectroscopy of the carbon nanotube yarn 2 is observed. The G-Band is a peak that appears at 1350 cm-1, and the DB peak is a peak that appears at 1350 cm-1. The peak intensity ratio IG / ID (G / D ratio) of the G-Band to the D-Band can be increased from 1-2 before graphitization to 10-40. Increasing the G / D ratio of the carbon nanotube yarn 2 can reduce the electrical resistance of the carbon nanotube yarn 2. Both ends of the carbon nanotube yarn 2 are electrically connected via an external load (not shown). Current flows along the stretching direction (length direction) D1 of the carbon nanotube yarn 2. In other words, the direction in which current flows through the carbon nanotube yarn 2 is the stretching direction D1.

[0017] In the carbon nanotube yarn 2, a plurality of carbon nanotubes 211 are oriented in a predetermined direction, thereby forming a path for electron movement (i.e., a path for current flow). As shown in the enlarged view A1 of FIG. 4, in the carbon nanotube yarn 2 according to this embodiment, the plurality of carbon nanotubes 211 are bundled together without twisting and are oriented in the stretching direction D1. Specifically, as shown in the enlarged view A1 of FIG. 4, the alignment direction D2 of the plurality of carbon nanotubes 211 is parallel to the stretching direction D1 of the carbon nanotube yarn 2. In other words, the carbon nanotube yarn 2 according to this embodiment is formed as a non-twisted yarn in which the plurality of carbon nanotubes 211 are oriented in one direction and aggregated. As a result, because the plurality of carbon nanotubes 211 are oriented in one direction, electrical resistance can be reduced compared to when they are not oriented in one direction. However, the present invention is not limited to this, and the carbon nanotube yarn may be formed as a twisted yarn.

[0018] The carbon nanotube yarn 2 is configured so that P-type characteristics and N-type characteristics alternate in the extension direction D1. Specifically, as shown in FIG. 4 , the carbon nanotube yarn 2 includes a plurality of P-type portions 21P formed as P-type semiconductors and a plurality of N-type portions 21N formed as N-type semiconductors, which are alternately arranged and continuously formed in the extension direction D1. The P-type portions 21P and N-type portions 21N are formed over a predetermined range in the extension direction D1 of the carbon nanotube yarn 2 by doping the carbon nanotubes 211 that constitute the carbon nanotube yarn 2. Note that, because carbon nanotubes tend to become P-type semiconductors due to the influence of oxygen molecules contained in the air, doping the P-type portions 21P is not essential. In the carbon nanotube yarn 2 according to this embodiment, the lengths of the P-type portions 21P and the N-type portions 21N are equal in length in the extension direction D1 of the carbon nanotube yarn 2. However, the present invention is not limited to this, and the P-type portion and the N-type portion may have different lengths.

[0019] 4 indicates the boundary between the end of the P-type portion 21P and the end of the N-type portion 21N. In this example, the P-type portion 21P and the N-type portion 21N are continuously formed (PN junction), so the P-type portion 21P and the N-type portion 21N are adjacent to each other in the extension direction of the carbon nanotube yarn 2, and the boundary C1 is formed as the boundary where the P-type portion 21P and the N-type portion 21N switch over. Note that the boundary C1 may be made of another conductor.

[0020] FIG. 5 is a schematic diagram illustrating the relationship between the substrate 1 and the carbon nanotube yarn 2 in the thermoelectric conversion module 100 according to the first embodiment. As shown in FIG. 5, the carbon nanotube yarn 2 is wound spirally around the substrate 1. More specifically, the carbon nanotube yarn 2 is wound spirally around the side surface of the substrate 1. The carbon nanotube yarn 2 wound spirally around the substrate 1 forms a spiral 20 surrounding the substrate 1. The central axis of the spiral, designated by reference symbol CA1, extends along the extension direction of the substrate 1 (the front-rear direction in this example). Hereinafter, the direction in which the central axis CA1 extends may also be referred to as the axial direction. Hereinafter, the portion of the spiral 20 designated by reference symbol 20a in FIG. 5, which corresponds to one turn of the spiral 20, is referred to as the one-turn portion. In this case, as shown in FIG. 5, the P-type portion 21P and the N-type portion 21N are alternately arranged in half turns (half the circumference of the one-turn portion 20a) in the spiral 20. In other words, in the stretching direction of the carbon nanotube yarn 2, the length of the P-type portion 21P and the length of the N-type portion 21N are equal to half a turn of the helix 20. Therefore, the helix 20 is configured so that each turn 20a includes one P-type portion 21P and one N-type portion 21N. In other words, each turn 20a of the helix 20 is formed by one P-type portion 21P and one N-type portion 21N. Note that, in the present invention, the length of the P-type portion or N-type portion does not have to be half a turn of the helix. In the present invention, the length of the P-type portion or the N-type portion in the stretching direction of the carbon nanotube yarn may be shorter than the length of one turn of the helix in the stretching direction.

[0021] As shown in FIG. 5, the P-type portion 21P forms the left half of the one turn portion 20a of the spiral 20, and the N-type portion 21N forms the right half of the one turn portion 20a of the spiral 20. Therefore, each of the multiple boundary portions C1 is located at either the upper or lower portion of the spiral 20. More specifically, of two boundary portions C1 adjacent to each other in the axial direction of the spiral 20 (in this example, the front-to-rear direction), one is located at the upper portion of the spiral 20, and the other is located at the lower portion of the spiral 20. In this way, by alternately arranging the boundary portions C1 above and below, the upper portion of the spiral 20 is formed as a heat receiving portion 201, and the lower portion of the spiral 20 is formed as a heat dissipation portion 202. As shown in FIG. 5, the heat receiving portion 201 and the heat dissipation portion 202 are formed on opposite sides of the substrate 1 (in this example, the upper and lower sides of the substrate 1) as regions including multiple boundary portions C1 aligned in the axial direction.

[0022] Each of the multiple boundaries C1 included in the carbon nanotube yarn 2 is disposed in either the heat receiving portion 201 or the heat dissipation portion 202. Therefore, as shown in FIG. 5, one end of each of the multiple P-type portions 21P is included in the heat receiving portion 201 and the other end is included in the heat dissipation portion 202. Similarly, each of the multiple N-type portions 21N is included in the heat receiving portion 201 and the other end is included in the heat dissipation portion 202. As shown in FIG. 1, the heat receiving portion 201 is in contact with a hot heat source 200 disposed above the thermoelectric conversion module 100, and the heat dissipation portion 202 is in contact with a cold heat source 300 disposed below the thermoelectric conversion module 100. Note that if the hot heat source 200 is at a higher temperature than the ambient temperature around the thermoelectric conversion module 100, the cold heat source 300 may be the atmosphere (air).

[0023] Doping to impart semiconducting properties to the carbon nanotube yarn 2 is performed while the carbon nanotube wire is wound around the substrate 1 in a spiral shape. When only N-type doping is performed, the right half of the carbon nanotube wire wound around the substrate 1 is immersed in a solution containing an N-type doping agent. This results in a spiral 20 in which P-type portions 21P and N-type portions 21N are alternately arranged on the left and right sides, each half-turn long. When both N-type and P-type doping are performed, the left half of the carbon nanotube wire wound around the substrate 1 is immersed in a solution containing a P-type doping agent, and the right half is immersed in a solution containing an N-type doping agent. In this way, the carbon nanotube yarn 2 may be doped with only the N-type doping agent, or may be doped with both the N-type doping agent and the P-type doping agent. The doping method is not limited to immersion, and various methods such as vapor deposition, sputtering, printing, and brush coating may also be used. Examples of N-type doping agents include known N-type doping agents such as dppe (1,2-bis(diphenylphosphino)ethane), DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), DODMAC (dimethyldioctadecylammonium chloride), n-DMBI (4-(1,3-dimethyl-2,3-dihydro-1H-benzimidazol-2-yl)-N,N-dimethylaniline), PEI (polyethyleneimine), PVP (polyvinylpyrrolidone), tpp (triphenylphosphine), TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene), TMG (1,1,3,3-tetramethylguanidine), tris(p-methoxyphenyl)phosphine, dppp (1,3-bis(diphenylphosphino)propane), and indole. Examples of the P-type doping agent include known P-type doping agents such as 9H-carbazole, 9H-carbazole-4-ol, and pyrazine. This can be done.

[0024] In addition, in this embodiment, a carbon nanotube yarn formed into a thread shape from carbon nanotubes is used as the thermoelectric conversion member, but the thermoelectric conversion member according to the present invention is not limited to a carbon nanotube yarn. The thermoelectric conversion member may be a nonwoven fabric of carbon nanotubes formed into a strip shape. This carbon nanotube nonwoven fabric may contain an N-type doping agent and The semiconductor layer may be doped with only an N-type dopant out of a P-type dopant, or may be doped with both an N-type dopant and a P-type dopant.

[0025] [Insulating wire] The insulating wire 3 is an insulating wire, and as shown in Figures 2 and 3, it is wound around the side of the substrate 1 together with the carbon nanotube yarn 2. Examples of materials for the insulating wire 3 include insulating synthetic fibers such as nylon, but are not limited to these as long as they have heat resistance and durability in the environment in which the thermoelectric conversion module 100 is used. The insulating wire 3 is wound spirally around the substrate 1 so as to be interposed between adjacent one-turn portions 20a, 20a of the spiral 20 of the carbon nanotube yarn 2. In this way, the thermoelectric conversion module 100 has a double spiral structure in which the carbon nanotube yarn 2 and the insulating wire 3 are alternately arranged along the axial direction of the spiral 20.

[0026] [Power generation by thermoelectric conversion module] Power generation by the thermoelectric conversion module 100 will be described below with reference to FIG. 1. As shown in FIG. 1, the thermoelectric conversion module 100 is used in a state where it is disposed between a hot heat source 200 and a cold heat source 300 that are disposed above and below it. The heat receiving portion 201 of the thermoelectric conversion module 100 is in contact with the hot heat source 200 and is heated by receiving heat from the hot heat source 200. On the other hand, the heat dissipation portion 202 of the thermoelectric conversion module 100 is in contact with the cold heat source 300 and is cooled by dissipating heat to the cold heat source 300. As a result, the heat receiving portion 201 becomes hotter than the heat dissipation portion 202, resulting in a temperature difference between the heat receiving portion 201 and the heat dissipation portion 202. Here, as described above, the P-type portion 21P and the N-type portion 21N that constitute the carbon nanotube yarn 2 are disposed such that one end of each is included in the heat receiving portion 201 and the other end of each is included in the heat dissipation portion 202. Therefore, the heat receiving portion 201 becomes hotter than the heat dissipation portion 202, and one end of the P-type portion 21P (the end included in the heat receiving portion 201) becomes hotter than the other end (the end included in the heat dissipation portion 202), causing a temperature difference between both ends of the P-type portion 21P. As a result, in the P-type portion 21P, positive charges are transported from the heat receiving portion 201 side toward the heat dissipation portion 202 side, causing a potential difference between the heat receiving portion 201 side and the heat dissipation portion 202 side. Similarly, one end of the N-type portion 21N (the end included in the heat receiving portion 201) becomes hotter than the other end (the end included in the heat dissipation portion 202), causing a temperature difference between both ends of the N-type portion 21N. As a result, in the N-type portion 21N, negative charges are transported from the heat receiving portion 201 side toward the heat dissipation portion 202 side, causing a potential difference between the heat receiving portion 201 side and the heat dissipation portion 202 side. In this way, thermoelectric power due to the Seebeck effect is generated in the P-type portion 21P and the N-type portion 21N. Then, by connecting an external load to both ends of the carbon nanotube yarn 2, a current flows through the carbon nanotube yarn 2, and electric power can be extracted. As shown in Fig. 1, in the P-type portion 21P, a current flows from the heat receiving portion 201 side to the heat dissipation portion 202 side, and in the N-type portion 21N, a current flows from the heat dissipation portion 202 side to the heat receiving portion 201 side.

[0027] As shown in FIG. 1 , in the thermoelectric conversion module 100, one side (upper portion) of the spiral 20 formed by the carbon nanotube yarn 2 is formed as a heat receiving portion 201, and the other side (lower portion) opposite the heat receiving portion 201 across the substrate 1 is formed as a heat dissipation portion 202. That is, the heat receiving portion 201 and the heat dissipation portion 202 are formed on opposite sides (upper and lower sides) of the heat insulating substrate 1. The heat insulating substrate 1 is interposed between the heat receiving portion 201 and the heat dissipation portion 202, thereby suppressing heat transfer from the heat receiving portion 201 to the heat dissipation portion 202. Furthermore, the heat insulating holes 4 are formed in the substrate 1, so that an air layer that functions as a heat insulating layer is interposed between the heat receiving portion 201 and the heat dissipation portion 202. The heat insulating holes 4 further suppress heat transfer from the heat receiving portion 201 to the heat dissipation portion 202. As a result, the temperature difference between the heat receiving portion 201 and the heat dissipating portion 202, that is, the temperature difference between both ends of the P-type portion 21P and the N-type portion 21N, is ensured, and the thermoelectric conversion efficiency is improved.

[0028] Moreover, since the base material 1 has insulating properties as described above, the P-type portion 21P and the N-type portion 21N included in the carbon nanotube yarn 2 are prevented from being electrically connected via the base material 1. Furthermore, since the insulating wire material 3 having insulating properties is interposed between adjacent one-turn portions 20a, 20a of the helical body 20, the P-type portion 21P and the N-type portion 21N are prevented from being electrically connected at any point other than the boundary portion C1. This maintains the P-type portion 21P and the N-type portion 21N electrically connected in series.

[0029] As described above, the carbon nanotube yarn 2 according to this example is formed as an untwisted yarn in which multiple carbon nanotubes 211 are bundled without being twisted, and the orientation direction D2 of the multiple carbon nanotubes 211 is parallel to the extension direction D1 of the carbon nanotube yarn 2, which is the direction in which current flows. This can increase the electrical conductivity of the thermoelectric conversion module 100. When comparing heat transfer in the orientation direction D2 of the carbon nanotube yarn 2 with heat transfer in a direction perpendicular to the orientation direction D2 (the direction indicated by symbol D3 in the enlarged view A1 of FIG. 4), heat tends to be less transferred in the direction D3 perpendicular to the orientation direction D2.

[0030] 1, the orientation direction D2 and the first direction D are perpendicular to each other in the heat receiving portion 201. Similarly, the orientation direction D2 and the first direction D are perpendicular to each other in the heat dissipation portion 202. This is because the carbon nanotube yarn 2 is formed as an untwisted yarn. Since the orientation direction D2 and the first direction D are perpendicular to each other in the heat receiving portion 201 and the heat dissipation portion 202, the heat transfer from the heat receiving portion 201 to the heat dissipation portion 202 is further suppressed. This ensures a more suitable temperature difference between the heat receiving portion 201 and the heat dissipation portion 202.

[0031] [Actions and Effects] As described above, the thermoelectric conversion module 100 according to this embodiment includes the substrate 1 extending in a predetermined direction, and the carbon nanotube yarn 2 as a thermoelectric conversion member, which is formed in a thread-like shape from carbon nanotubes 211 and wound spirally around the substrate 1. One side of the spiral 20 formed from the carbon nanotube yarn 2 is formed as a heat receiving portion 201, and the other side opposite to the one side across the substrate 1 is formed as a heat dissipation portion 202. The substrate 1 has heat insulating holes 4 that form an air layer extending in the extension direction of the substrate 1.

[0032] In the thermoelectric conversion module 100, the substrate 1 having the insulating holes 4 formed therein and having thermal insulation properties is interposed between the heat receiving portion 201 and the heat dissipation portion 202, thereby ensuring a temperature difference between the heat receiving portion 201 and the heat dissipation portion 202, i.e., a temperature difference between both ends of the P-type portion 21P and the N-type portion 21N. As a result, the thermoelectric conversion module 100 according to this embodiment can improve thermoelectric conversion efficiency. Furthermore, even if the thermal conductivity of the carbon nanotube yarn 2 is increased by increasing the electrical conductivity of the carbon nanotube yarn 2, the thermoelectric conversion module 100 can ensure a temperature difference between the heat receiving portion 201 and the heat dissipation portion 202 due to the insulating properties of the substrate 1. Therefore, the thermoelectric conversion module 100 can ensure a temperature difference between the heat receiving portion 201 and the heat dissipation portion 202 while increasing the electrical conductivity of the carbon nanotube yarn 2. This allows for a higher thermoelectric conversion efficiency. In other words, the thermoelectric conversion module 100 can achieve both high electrical conductivity and improved thermoelectric conversion efficiency. Furthermore, this invention can contribute to the achievement of Goal 7 "Affordable and clean energy," Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization," and Goal 12 "Responsible consumption and production" out of the 17 goals of the Sustainable Development Goals (SDGs) led by the United Nations. Furthermore, this invention can reduce the amount of rare metals used while ensuring the high functionality of the thermoelectric conversion module.

[0033] The carbon nanotube yarn 2 according to this embodiment includes a plurality of P-type portions 21P formed as P-type semiconductors and a plurality of N-type portions 21N formed as N-type semiconductors. The P-type portions 21P and the N-type portions 21N are alternately arranged and continuously formed in the extension direction of the carbon nanotube yarn 2. The lengths of the P-type portions 21P and the N-type portions 21N in the extension direction of the carbon nanotube yarn 2 are shorter than the length of one turn 20a of the spiral 20. The P-type portions 21P and the N-type portions 21N are arranged such that one end of each is included in the heat receiving portion 201 and the other end is included in the heat dissipation portion 202. This allows the thermoelectric conversion module 100 to generate electricity by utilizing the temperature difference between the heat receiving portion 201 and the heat dissipation portion 202.

[0034] Furthermore, since the thermoelectric conversion module 100 employs a structure in which the carbon nanotube yarn 2 is wound around the substrate 1, the number of series connections between the P-type portions 21P and the N-type portions 21N can be easily increased simply by increasing the number of turns of the carbon nanotube yarn 2. This makes it possible to obtain a high voltage with a compact module.

[0035] Furthermore, since the thermoelectric conversion module 100 according to this embodiment uses the thread-like carbon nanotube yarn 2, the number of turns can be increased and a higher voltage can be obtained compared to when a strip-like carbon nanotube nonwoven fabric, which has a larger width per turn, is used. Furthermore, the carbon nanotube yarn 2 has the advantage of being more flexible than the carbon nanotube nonwoven fabric.

[0036] Furthermore, the thermoelectric conversion module 100 according to this embodiment includes an insulating wire 3, the base material 1 has insulating properties, and the insulating wire 3 is spirally wound around the base material 1 so as to be interposed between adjacent one-turn portions 20a, 20a of the helix 20 of the carbon nanotube yarn 2. This allows the P-type portion 21P and the N-type portion 21N to be maintained electrically connected in series, thereby enabling a high voltage to be obtained.

[0037] It is not essential for the present invention that the thermoelectric conversion module include insulating wires or that the substrate have insulating properties. For example, if the P-type and N-type parts are maintained electrically connected in series by, for example, covering the carbon nanotube yarn with an insulating material, the thermoelectric conversion module does not need to include insulating wires, and the substrate does not need to have insulating properties.

[0038] Furthermore, the carbon nanotube yarn 2 of the thermoelectric conversion module 100 according to this embodiment is formed as an untwisted yarn in which a plurality of carbon nanotubes 211 are oriented in one direction and aggregated. By using an untwisted yarn in which a plurality of carbon nanotubes 211 are oriented in the extension direction D1 of the carbon nanotube yarn 2 as the carbon nanotube yarn 2, the electrical conductivity of the carbon nanotube yarn 2 can be improved. Furthermore, by using an untwisted yarn for the carbon nanotube yarn 2, the first direction D, which is the direction from the heat receiving section 201 to the heat dissipation section 202, is perpendicular to the orientation direction D2 of the carbon nanotubes 211 in the heat receiving section 201 and the heat dissipation section 202. This more suitably ensures a temperature difference between the heat receiving section 201 and the heat dissipation section 202. However, the carbon nanotube yarn according to the present invention does not necessarily have a plurality of carbon nanotubes oriented in one direction, and does not necessarily have to be an untwisted yarn. When the carbon nanotube yarn 2 is twisted, the twist angle θ1 formed by the extension direction D1 of the carbon nanotube yarn 2 and the orientation direction D2 of the carbon nanotubes is preferably θ1≦4°. This makes it possible to appropriately ensure the temperature difference between the heat receiving section 201 and the heat dissipation section 202. From the viewpoint of ensuring the temperature difference, it is more preferable to ensure θ1≦3°, and even more preferable to ensure θ1≦2°. However, the present invention is not limited to this.

[0039] Furthermore, in the thermoelectric conversion module 100 according to this embodiment, the base material 1 is formed from a flexible material. By providing flexibility (pliability) to the base material 1, the thermoelectric conversion module 100 can be flexibly deformed to accommodate the installation target, thereby improving convenience. For example, the thermoelectric conversion module 100 can be wrapped around a heat source such as an automobile muffler or a pipe in a factory or home to generate electricity, or can be worn on the human body to generate electricity as an independent power source for a wearable device.

[0040] [Modification of the first embodiment] Fig. 6 is a perspective view of a base material 1A used in a thermoelectric conversion module according to a modified example of embodiment 1. As shown in Fig. 6, the base material 1A is made up of multiple members, with heat insulating holes 4 formed between the multiple members. The multiple members making up the base material 1A include a first member 11 and a second member 12 that have different thermal conductivities.

[0041] 6, in the base material 1A according to the modification, the first member 11 is arranged on the upper side (the heat receiving portion 201 side) and the second member 12 is arranged on the lower side (the heat dissipation portion 202 side) of the heat insulation hole 4 in the vertical direction. In other words, the second member 12 is arranged closer to the heat dissipation portion 202 than the first member 11.

[0042] The first member 11 and the second member 12 are block-shaped members that have a substantially L-shaped cross section and extend in the extension direction of the base material 1A. The first member 11 and the second member 12 are joined together with an adhesive or the like to form the base material 1A. A gap with a square cross section is formed between the step portion of the first member 11 and the step portion of the second member 12, and this gap forms the insulation hole 4. Note that the insulation hole according to the present invention may be formed inside a cylindrical member such as a tube that is inserted into the gaps between multiple members, for example.

[0043] As shown in FIG. 6 , in the base material 1A according to the modified example, the first member 11 is disposed on the upper side (the heat receiving portion 201 side) and the second member 12 is disposed on the lower side (the heat dissipation portion 202 side) in the vertical direction. That is, the first member 11 is disposed on the heat receiving portion 201 side and the second member 12 is disposed on the heat dissipation portion 202 side, with the heat insulation hole 4 sandwiched between them. The first member 11 and the second member 12 have different thermal conductivities, with the second member 12 having a higher thermal conductivity than the first member 11. Examples of materials for the first member 11 include silicone rubber (thermal conductivity: 0.2 [W / (m·K)]) and natural rubber (thermal conductivity: 0.13 [W / (m·K)]). Examples of materials for the second member 12 include PPS resin (high thermal conductivity grade, thermal conductivity: 1.2 [W / (m·K)]). However, the materials for the first and second members according to the present invention are not limited to those described above. Furthermore, although there are no particular limitations on the values ​​of the thermal conductivity, it is preferable that the thermal conductivity of the first member 11 be equal to or greater than 0.1 [W / (m·K)] and equal to or less than 0.9 [W / (m·K)], and that the thermal conductivity of the second member 12 be equal to or greater than 1.0 [W / (m·K)] and equal to or less than 3.0 [W / (m·K)].

[0044] As described above, in the modified example of the first embodiment, the base material 1A is made up of multiple components, and the heat insulating holes 4 are formed between the multiple components. This reduces processing costs compared to forming heat insulating holes by drilling holes in a single component. It also increases the degree of freedom in the shape and size of the base material 1A, and is expected to improve shape accuracy and dimensional accuracy. Furthermore, the interfaces between the multiple components act as resistance to heat conduction, enhancing the heat insulating effect.

[0045] In a modification of the first embodiment, the base material 1A is configured to include a first member 11 and a second member 12 having a higher thermal conductivity than the first member 11, and the second member 12 is disposed closer to the heat dissipation section 202 than the first member 11. By disposing the first member 11, which has a relatively low thermal conductivity, on the heat receiving section 201 side, heat transfer from the heat receiving section 201 to the heat dissipation section 202 is suppressed while By disposing the second member 12, which has a relatively high thermal conductivity, on the heat dissipation section 202 side, it is possible to promote heat dissipation from the heat dissipation section 202. This makes it possible to increase the temperature difference between the heat receiving section 201 and the heat dissipation section 202. As a result, a thermoelectric conversion module according to a modification of the first embodiment, which includes the base material 1A, can achieve higher thermoelectric conversion efficiency.

[0046] In this modification, the base material 1A is made up of two members (the first member 11 and the second member 12), but the number of members constituting the base material is not particularly limited in the present invention. The base material may be made up of a combination of three or more members.

[0047] <Embodiment 2> Fig. 7 is a cross-sectional view schematically illustrating a state in which a thermoelectric conversion module 100B according to embodiment 2 is used. Like Fig. 1, Fig. 7 illustrates a cross section perpendicular to the front-rear direction. As shown in Fig. 7, the thermoelectric conversion module 100B according to embodiment 2 differs from the thermoelectric conversion module 100 according to embodiment 1 in that a cooling flow path 5 is formed in the base material 1B. Hereinafter, the second embodiment will be described, focusing on the differences from the first embodiment, and similar components will be denoted by the same reference numerals and will not be described in detail.

[0048] As shown in FIG. 7, the base material 1B according to the second embodiment has a plurality of layers extending in the extending direction of the base material 1B. The cooling flow path 5 is formed through the insulating hole 4 and the heat dissipation portion 202, and extends continuously from one end to the other end in the extension direction of the base material 1B. In other words, the cooling flow path 5 penetrates the base material 1B along the extension direction of the base material 1B. In the second embodiment, the cooling flow path 5 is formed by the inner wall of a through hole with a substantially circular cross section formed in the base material 1B. Note that the cooling flow path according to the present invention may be formed inside a cylindrical member such as a tube inserted into a hollow hole in the base material. Furthermore, the cross-sectional shape of the cooling flow path is not limited to a circle and may be a square, and various other shapes may be adopted.

[0049] A cooling medium supply source (not shown) is connected to the cooling flow path 5 via a conduit, and when the thermoelectric conversion module 100B is in use, the cooling medium is continuously supplied to the cooling flow path 5. The cooling medium continuously flows through the cooling flow path 5, thereby cooling the heat dissipation unit 202. The cooling medium flowing through the cooling flow path 5 may be a liquid such as water, or a gas such as air. The temperature of the cooling medium is not particularly limited as long as it is a temperature that can ensure a temperature difference between the heat receiving unit 201 and the heat dissipation unit 202, and specifically, it is preferably lower than the temperature of the heat source.

[0050] As described above, in the thermoelectric conversion module 100B according to the second embodiment, the cooling flow paths 5 extending in the extension direction of the base material 1B and allowing a cooling medium to flow are formed in the base material 1B, thereby making it possible to actively cool the heat dissipation section 202. Furthermore, by forming the cooling flow paths 5 between the insulation holes 4 and the heat dissipation section 202, it is possible to cool the heat dissipation section 202 while suppressing cooling of the heat receiving section 201. As a result, in the thermoelectric conversion module 100B according to the second embodiment, it is possible to increase the temperature difference between the heat receiving section 201 and the heat dissipation section 202, thereby achieving higher thermoelectric conversion efficiency.

[0051] [Modification of the second embodiment] Fig. 8 is a perspective view of a substrate 1C used in a thermoelectric conversion module according to a modified example of embodiment 2. As shown in Fig. 8, the substrate 1C is made up of multiple members, similar to the above-described substrate 1A, and heat-insulating holes 4 are formed between the multiple members. The substrate 1C is made up of a first member 11 and a second member 12, which have different thermal conductivities. The second member 12, which has a higher thermal conductivity than the first member 11, is arranged closer to the heat dissipation section 202 than the first member 11.

[0052] As shown in FIG. 8, the first member 11 forms the heat insulating hole 4, and the second member 12 forms the cooling flow path 5. The first member 11 includes a block 11a having a generally U-shaped cross section with a groove formed on its underside, and a plate 11b disposed below the block 11a. The gap between the block 11a and the plate 11b (the space surrounded by the block 11a and the plate 11b) forms the heat insulating hole 4. The second member 12 includes blocks 12a, 12a disposed on both the left and right sides of the tube 6 that forms the cooling flow path 5 therein, and a plate 12b disposed below the tube 6. The tube 6 is held by the blocks 12a, 12a, and the plate 12b. The block 11a, the plate 11b, the blocks 12a, 12a, and the plate 12b are joined together with an adhesive or the like to form the base material 1C. In order to increase the thermal conductivity between the substrate 1C and the tube 6, the tube 6 may be covered with a metal tape, or a highly thermally conductive adhesive or the like may be filled in the gap between the substrate 1C and the tube 6. However, the tube 6 is not essential in the present invention, and the cooling flow path may be formed by the inner wall of the substrate.

[0053] According to the modified example of the second embodiment, similar to the above-described base material 1A, the base material 1C is made of multiple members, and the heat insulating holes 4 are formed between the multiple members, thereby reducing processing costs and improving shape accuracy and dimensional accuracy. Furthermore, according to the modified example of the second embodiment, the second member 12, which has a higher thermal conductivity than the first member 11, is disposed closer to the heat dissipation member 202 than the first member 11, thereby increasing the temperature difference between the heat receiving member 201 and the heat dissipation member 202. As a result, a thermoelectric conversion module according to the modified example of the second embodiment, which includes the base material 1C, can achieve higher thermoelectric conversion efficiency.

[0054] <Confirmation test of generated voltage> Tests were conducted to confirm the effect of improving power generation voltage for Examples and Comparative Examples. Example 1 used a thermoelectric conversion module equivalent to the thermoelectric conversion module 100 according to Embodiment 1. Example 2 used a thermoelectric conversion module equivalent to the thermoelectric conversion module 100B according to Embodiment 2. The Comparative Example differs from Examples 1 and 2 in that neither the heat insulating holes 4 nor the cooling channels 5 are formed in the substrate, but in other respects uses a thermoelectric conversion module similar to Examples 1 and 2.

[0055] In the confirmation test, Examples 1 and 2 and the Comparative Example were placed on a hot plate. A temperature difference was applied to the thermoelectric conversion module by using the hot plate as a heat source and the atmosphere (air) as a cold source, thereby generating electricity. The temperature of the hot plate was set to 45°C. Tap water at approximately 18°C ​​was continuously passed through the cooling channel of Example 2 as a cooling medium. For Example 1 and the Comparative Example, the average voltage values ​​measured every 1 second for 30 seconds when the generated voltage was stable were calculated. For Example 2, the average voltage values ​​measured every 1 second for 30 seconds after the start of the tap water flow and the time (140 seconds) when the generated voltage was determined to have stabilized were calculated. The ratio (effectiveness [%]) of the generated voltage of each Example 1, 2, and the Comparative Example to the generated voltage of the Comparative Example was then calculated. Table 1 shows the effectiveness of the generated voltage in Examples 1 and 2 and the Comparative Example. [Table 1]

[0056] As shown in Table 1, in Example 1, the efficiency rate was 116% compared to the comparative example, and the improvement in generated voltage due to the insulation of the insulation holes was 16%. In Example 2, the efficiency rate was 162% compared to the comparative example, and the improvement in generated voltage due to the insulation of the insulation holes and the flow of tap water was 62%. [%]. The generated voltage was higher in the example than in the comparative example due to the insulation by the insulation holes or the insulation by the insulation holes and the flow of tap water. This confirmed that the power generation efficiency was improved by the insulation holes or the insulation holes and the flow of cooling water.

[0057] <Other> Although the preferred embodiments of the present invention have been described above, the various embodiments described above can be combined as much as possible. [Explanation of symbols]

[0058] 1, 1A, 1B, 1C: Base material 2: Carbon nanotube yarn 21P:P type part 21N:N type part 211: Carbon nanotubes 3: Insulating wire 4: Heat insulation hole 5: Cooling channel 20: Spiral 20a: 1st turn 201:Heat receiving part 202: Heat dissipation part 100, 100B: Thermoelectric conversion module

Claims

1. A thermoelectric conversion module having a heat receiving portion and a heat dissipating portion, which generates electricity by utilizing a temperature difference between the heat receiving portion and the heat dissipating portion, A substrate; a thermoelectric conversion member spirally wound around the substrate, one side of the spiral formed by the thermoelectric conversion member is formed as the heat receiving portion, and the other side opposite to the one side across the base material is formed as the heat dissipation portion, The base material has heat insulating holes that form a heat insulating layer extending along the extending direction of the base material. Thermoelectric conversion module.

2. the thermoelectric conversion member includes a plurality of P-type portions formed as P-type semiconductors and a plurality of N-type portions formed as N-type semiconductors, the P-type portions and the N-type portions are alternately arranged and continuously formed in the extending direction of the thermoelectric conversion member, the P-type portion and the N-type portion are arranged such that one end of each is included in the heat receiving portion and the other end of each is included in the heat dissipation portion. The thermoelectric conversion module according to claim 1 .

3. The thermoelectric conversion member is a carbon nanotube yarn formed into a thread shape from carbon nanotubes. The thermoelectric conversion module according to claim 1 or 2.

4. the thermoelectric conversion member is formed of a nonwoven fabric of carbon nanotubes; The thermoelectric conversion module according to claim 1 or 2.

5. The substrate is composed of a plurality of members, The heat insulating holes are formed between the plurality of members. The thermoelectric conversion module according to claim 1 .

6. the base material includes a first member and a second member having a higher thermal conductivity than the first member, The second member is disposed closer to the heat dissipation portion than the first member. The thermoelectric conversion module according to claim 1 or 5.

7. The base material has a cooling flow path formed therein, the cooling flow path extending along the extending direction of the base material and allowing a cooling medium to flow therethrough. The thermoelectric conversion module according to claim 1 or 2.

8. The cooling flow path is formed between the heat insulating hole and the heat dissipation portion. The thermoelectric conversion module according to claim 7 .

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