Thermoelectric conversion module

Abstract

To provide a technique of improving the thermoelectric conversion efficiency of a thermoelectric conversion module.SOLUTION: The thermoelectric conversion module includes a base material and a thermoelectric conversion member wound helically around the base material. A first-side part of the helical body formed of the thermoelectric conversion member is formed as a heat receiving part, while a second-side part on the opposite side of the substrate to the side where the first-side part is formed is formed as a heat radiating part. The substrate has a groove part extending along the extending direction of the substrate and forming a gap between the thermoelectric conversion member and the substrate, the groove part being formed in at least one of a contact site in contact with the heat receiving part and a contact site in contact with the heat radiating part.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 modules made of fibrous carbon nanotubes are known (for example, Patent Document 1). Thermoelectric conversion modules 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] Patent No. 6529097 Summary of the Invention [Problem to be solved by the invention]

[0004] A thermoelectric conversion module has a structure in which, for example, P-type and N-type thermoelectric conversion members are alternately arranged, spirally wound around a substrate. The thermoelectric conversion member is obtained by doping a wire formed from a conductive fibrous material to impart semiconducting properties. Examples of doping methods for alternately arranging P-type and N-type thermoelectric conversion members include an immersion method in which one side of the wire, while spirally wound around the substrate, is immersed in a doping solution, and an application method in which a doping solution is applied to a portion of the wire spirally wound around the substrate.

[0005] At this time, if capillary action occurs between the wire and the substrate, causing the doping liquid to excessively penetrate (seep out) into areas where doping is not required, the interface between the P-type and N-type will not be formed as desired, and the distinction between the P-type and N-type will be insufficient, which may result in a decrease in the electromotive force of the thermoelectric conversion member.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technique capable of improving the thermoelectric conversion efficiency in a thermoelectric conversion module. [Means for solving the problem]

[0007] 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, a plurality of P-type portions and a plurality of N-type portions are formed in the thermoelectric conversion member by a doping process, and 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, The base material has a groove portion extending along an extending direction of the base material and forming a gap between the thermoelectric conversion member and the base material, the groove portion being formed in at least one of a contact portion with the heat receiving portion and a contact portion with the heat dissipation portion. Thermoelectric conversion module. [2] the grooves are formed in both a contact portion with the heat receiving portion and a contact portion with the heat dissipating portion of the base material; [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] a boundary between the P-type portion and the N-type portion is formed at a position facing the groove portion; A thermoelectric conversion module according to any one of [1] to [3]. [5] the thermoelectric conversion member is wound around the base material at intervals of 0.12 mm or more in the extending direction of the base material; A thermoelectric conversion module according to any one of [1] to [4]. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve the thermoelectric conversion efficiency in a thermoelectric conversion module. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating a state in which a thermoelectric conversion module according to an embodiment is used. [Figure 2] FIG. 2 is a top view of the thermoelectric conversion module according to the embodiment. [Figure 3] FIG. 2 is a right side view of the thermoelectric conversion module according to the embodiment. [Figure 4] FIG. 2 is a cross-sectional view of a substrate according to an embodiment. [Figure 5] 1A and 1B are diagrams for explaining the configuration of a carbon nanotube yarn according to an embodiment. [Figure 6] 3A and 3B are schematic diagrams illustrating the relationship between a substrate and carbon nanotube yarns in a thermoelectric conversion module according to an embodiment. [Figure 7] 1 is a schematic diagram for explaining a doping treatment for a carbon nanotube yarn. FIG. [Figure 8]FIG. 10 is a cross-sectional view of a substrate used in a thermoelectric conversion module according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] 1 to 3 are diagrams illustrating a thermoelectric conversion module 100 according to an 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 an 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 top view of the thermoelectric conversion module 100 according to an embodiment. FIG. 3 is a right side view of the thermoelectric conversion module 100 according to an embodiment. Here, in FIG. 1, the direction from the heat receiving portion 201 toward the heat dissipating portion 202 (leftward 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.

[0012] [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 on the left and right sides. The hot heat source 200 and the cold heat source 300 are heat sources for creating a temperature difference in 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 right side 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 left side 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 outside air temperature, with the human body as the hot heat source 200 and the atmosphere (air) as the cold heat source.

[0013] 1 to 3, the thermoelectric conversion module 100 includes a substrate 1 and carbon nanotube yarns 2 (an example of a "thermoelectric conversion member" according to the present invention). Each component of the thermoelectric conversion module 100 will be described below.

[0014] [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." The substrate itself does not necessarily have to be thermally insulating, and the substrate does not have to be made of a thermally 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, or the substrate may be formed in a cylindrical shape having a substantially circular cross section.

[0015] As shown in FIG. 1, the substrate 1 has a pair of side surfaces 1a and 1b arranged vertically and parallel to each other, and a pair of side surfaces 1c and 1d arranged horizontally and parallel to each other, and has a rectangular cross-sectional shape. The substrate 1 is arranged so that the side surfaces 1a and 1b are parallel to the left-right direction. The left-right width of the side surfaces 1a and 1b is longer than the left-right width of the side surfaces 1a and 1b and the up-down width of the side surfaces 1c and 1d. In other words, the cross-sectional shape of the substrate 1 is a rectangle with its longer sides in the left-right direction. The substrate 1 1, the side surface 1c is a portion that comes into contact with the heat receiving portion 201, and the side surface 1d is a portion that comes into contact with the heat radiating portion 202. As shown in FIG.

[0016] FIG. 4 is a cross-sectional view of the substrate 1 according to this embodiment. FIG. 4 illustrates a cross section perpendicular to the extension direction of the substrate 1. As shown in FIG. 4, grooves 3 extending along the extension direction of the substrate 1 are formed on the side surfaces 1c and 1d of the substrate 1. The grooves 3 have a trapezoidal cross-sectional shape and are located at the center of the side surfaces 1c and 1d in the vertical direction. The grooves 3 are formed by a bottom surface 3a recessed relative to the side surfaces 1c and 1d of the substrate 1 and sidewalls 3b connecting the bottom surface 3a to the side surfaces 1c and 1d. As shown in FIG. 3, the grooves 3 extend over a predetermined range of the substrate 1. The grooves 3 may be formed over both ends of the substrate 1, but only need to be formed in at least a portion of the region of the substrate 1 around which the carbon nanotube yarn 2 is wound.

[0017] 4, the vertical width of the substrate 1 is designated as X, the lateral width of the substrate 1 as Y, the opening width (vertical width) of the groove 3 as H, the depth of the groove 3 as D, and the inclination angle of the side wall 3b with respect to the side surfaces 1c and 1d of the substrate 1 as θ. In this case, it is preferable that 5 mm≦X≦10 mm, 5 mm≦Y≦10 mm, 0.5 mm≦H≦3 mm, 0.5 mm≦D≦2 mm, and 34°≦θ≦90°.

[0018] However, the shape, position, and dimensions of the grooves 3 are not limited to the embodiment shown in FIG. 4. The cross-sectional shape of the grooves 3 may be a polygon such as a triangle, a semicircle, or various other shapes. The grooves 3 on the side surface 1c and the grooves 3 on the side surface 1d may have different shapes and positions. The grooves 3 may be formed only on either the side surface 1c or the side surface 1d. The grooves 3 may also be formed as slits that penetrate the substrate 1 in the left-right direction.

[0019] 1, grooves 3 are formed in the substrate 1, thereby forming gaps between the carbon nanotube yarns 2 and the substrate 1. In other words, in the areas where the grooves 3 exist, the substrate 1 and the carbon nanotube yarns 2 are not in contact with each other.

[0020] [Carbon nanotube yarn] The carbon nanotube yarn 2 is a flexible and conductive wire made of carbon nanotubes (also referred to as CNTs) formed into a thread-like shape. FIG. 5 is a diagram illustrating the configuration of the carbon nanotube yarn 2 according to an embodiment. As shown in the enlarged view A1 of FIG. 5, 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, the peak intensity ratio IG / ID (G / D ratio) of the G-Band, which is a peak that appears around 1590 cm-1, to the D-Band, which is a peak that appears around 1350 cm-1 in Raman spectroscopy analysis of the carbon nanotube yarn 2, 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. Note that 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.

[0021] 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. 5, in the carbon nanotube yarn 2 according to this embodiment, the plurality of carbon nanotubes 211 are bundled together without twisting and oriented in the stretching direction D1. More specifically, as shown in the enlarged view A1 of FIG. 5, 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.

[0022] 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. 5 , 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 doping the P-type portions 21P is not essential because they tend to become P-type semiconductors due to the influence of oxygen molecules in the air, etc. 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 the extension direction D1 of the carbon nanotube yarn 2. However, the present invention is not limited to this, and the lengths of the P-type portions and the N-type portions may be different.

[0023] 5 indicates a boundary between an end of the P-type portion 21P and an end of the N-type portion 21N. In this embodiment, the P-type portion 21P and the N-type portion 21N are continuously formed (PN junction), so that 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 a 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.

[0024] FIG. 6 is a schematic diagram illustrating the relationship between a substrate 1 and a carbon nanotube yarn 2 in a thermoelectric conversion module 100 according to an embodiment. As shown in FIG. 6, the carbon nanotube yarn 2 is wound spirally around the substrate 1. More specifically, the carbon nanotube yarn 2 is wound around the side 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 embodiment). 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. 6, which corresponds to one turn of the spiral 20, is referred to as the one-turn portion. In this case, as shown in FIG. 6, P-type portions 21P and N-type portions 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.

[0025] As shown in FIG. 6, the P-type portion 21P forms an upper half of the one-turn portion 20a of the spiral 20, and the N-type portion 21N forms a lower half of the one-turn portion 20a of the spiral 20. Therefore, each of the multiple boundary portions C1 is located on either the right or left side of the spiral 20. More specifically, of two boundary portions C1 adjacent to each other in the axial direction of the spiral 20 (in the front-to-rear direction in this embodiment), one is located on the right side of the spiral 20, and the other is located on the left side of the spiral 20. In this way, by alternately arranging the boundary portions C1 on the left and right sides, the right side of the spiral 20 is formed as the heat receiving portion 201, and the left side of the spiral 20 is formed as the heat dissipation portion 202. As shown in FIG. 6, the heat receiving portion 201 and the heat dissipation portion 202 are formed on opposite sides of the substrate 1 (in this embodiment, the right and left sides of the substrate 1) as regions including multiple boundary portions C1 aligned in the axial direction. 1, in a cross section perpendicular to the extending direction of the base material 1, a P-type portion 21P and an N-type portion 21N are formed on opposite sides of a groove portion 3 in the up-down direction. A boundary portion C1 between the P-type portion 21P and the N-type portion 21N is formed in a position facing the groove portion 3. The heat receiving portion 201 faces the groove portion 3 formed in the side surface 1c, which is one side portion of the base material 1, and the heat dissipating portion 202 faces the groove portion 3 formed in the side surface 1d, which is the other side portion of the base material 1.

[0026] Each of the multiple boundaries C1 included in the carbon nanotube yarn 2 is located in either the heat receiving portion 201 or the heat dissipation portion 202. Therefore, as shown in FIG. 6, 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 located to the right of the thermoelectric conversion module 100, and the heat dissipation portion 202 is in contact with a cold heat source 300 located to the left of the thermoelectric conversion module 100. Note that if the hot heat source 200 is hotter than the ambient temperature around the thermoelectric conversion module 100, the cold heat source 300 may be the atmosphere (air).

[0027] [Doping process] Examples of partial doping methods for imparting semiconductor properties to the carbon nanotube yarn 2 and arranging the P-type portions 21P and the N-type portions 21N alternately include a dipping method in which one side of the carbon nanotube yarn 2 is immersed in a doping solution while it is spirally wound around the substrate 1, a coating method in which the doping solution is applied to a portion of the wire spirally wound around the substrate 1, and a dripping method in which the doping solution is dripped onto a portion of the wire spirally wound around the substrate 1. In doping, a solution containing a doping agent (doping solution) is supplied to the carbon nanotube yarn 2 from a direction perpendicular to the extension direction of the substrate 1 and the first direction D. The carbon nanotube yarn 2 may be doped with only the N-type doping agent out of the N-type doping agent and the P-type doping agent, or may be doped with both the N-type doping agent and the P-type doping agent. Examples of N-type doping agents include known N-type doping agents such as polyethyleneimine, polyvinylpyrrolidone, triphenylphosphine, tris(p-methoxyphenyl)phosphine, 1,3-bis(diphenylphosphino)propane, indole, etc. Examples of P-type doping agents include known P-type doping agents such as 9H-carbazole, 9H-carbazol-4-ol, pyrazine, etc.

[0028] FIG. 7 is a schematic diagram illustrating a doping process for a carbon nanotube yarn 2. FIG. 7 illustrates, as an example, a state in which the carbon nanotube yarn 2 is subjected to an N-type doping process by a dipping method. An N-type doping liquid is contained in a container 400 in FIG. 7. As shown in FIG. 7, the carbon nanotube yarn 2 is spirally wound around a substrate 1, and the lower surface of the wound carbon nanotube yarn 2 is immersed in the N-type doping liquid, thereby supplying the N-type doping liquid to the carbon nanotube yarn 2. As a result, the N-type doping liquid permeates the portion of the carbon nanotube yarn 2 facing the side surface 1b. The N-type doping liquid that has permeated the carbon nanotube yarn 2 also rises along the side surfaces 1c and 1d of the substrate 1. As a result, the N-type doping liquid permeates partway through the portion of the carbon nanotube yarn 2 facing the side surfaces 1c and 1d. After the N-type doping liquid has permeated, the substrate 1 is pulled up and dried, thereby completing the N-type doping. When both N-type doping and P-type doping are performed, the carbon nanotube wire is wound spirally around the substrate 1, and the bottom surface (one surface) is immersed in an N-type doping solution, the substrate 1 is pulled up and dried, and then the top surface (the other surface) is immersed in a P-type doping solution, and the substrate 1 is pulled up and dried. In this manner, a spiral 20 can be obtained in which P-type portions 21P and N-type portions 21N are arranged alternately on the left and right, each half turn long.

[0029] Here, when the doping liquid is permeated into the carbon nanotube yarn 2, if capillary action occurs between the carbon nanotube yarn 2 and the substrate 1, the doping liquid may excessively permeate (seep out) into areas of the carbon nanotube yarn 2 that do not require doping, such as by wrapping around to the surface opposite to the surface to which the doping liquid is supplied. If this happens, the boundary C1 between the P-type portion 21P and the N-type portion 21N may not be formed as desired in the heat receiving portion 201 or the heat dissipation portion 202, and the P-type portion 21P and the N-type portion 21N may not be sufficiently separated (dyed). As a result, there is a concern that the electromotive force of the carbon nanotube yarn 2 may decrease.

[0030] In contrast, the substrate 1 according to this embodiment has grooves 3 formed at positions facing the heat receiving portion 201 and the heat dissipation portion 202. This creates gaps between the substrate 1 and the portions of the carbon nanotube yarn 2 where the heat receiving portion 201 and the heat dissipation portion 202 are to be formed, preventing contact between the substrate 1 and the carbon nanotube yarn 2. This prevents capillary action from occurring between the carbon nanotube yarn 2 and the substrate 1 during doping. This prevents the doping solution that has permeated the carbon nanotube yarn 2 from crossing the grooves 3, thereby preventing the doping solution from seeping out. This makes it easier for the boundary C1 between the P-type portion 21P and the N-type portion 21N to be formed at a position facing the grooves 3, allowing the P-type portion 21P and the N-type portion 21N to be appropriately dyed differently. As a result, the electromotive force of the carbon nanotube yarn 2 is increased compared to when the substrate 1 does not have the grooves 3, thereby improving the power generation efficiency of the thermoelectric conversion module 100.

[0031] [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.

[0032] 1, in the thermoelectric conversion module 100, one side (right side) of the spiral 20 formed by the carbon nanotube yarn 2 is formed as the heat receiving portion 201, and the other side (left side) opposite the heat receiving portion 201 across the substrate 1 is formed as the heat dissipation portion 202. In other words, the heat receiving portion 201 and the heat dissipation portion 202 are formed on opposite sides (right and left 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. As a result, the temperature difference between the heat receiving portion 201 and the heat dissipation portion 202, i.e., 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.

[0033] Furthermore, 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. This maintains the state in which the P-type portion 21P and the N-type portion 21N are electrically connected in series.

[0034] As described above, the carbon nanotube yarn 2 according to this embodiment 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 in 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. 5), heat tends to be less transferred in the direction D3 perpendicular to the orientation direction D2.

[0035] 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.

[0036] [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 from carbon nanotubes 211 in a thread-like shape and wound spirally around the substrate 1. The carbon nanotube yarn 2 has a plurality of P-type portions 21P and a plurality of N-type portions 21N formed by a doping process. The P-type portions 21P and the N-type portions 21N are alternately and continuously arranged in the extension direction of the carbon nanotube yarn 2, and 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. The substrate 1 also has grooves 3 extending along the extension direction of the substrate 1 and defining gaps between the carbon nanotube yarn 2 and the substrate 1, formed at both the contact portion with the heat receiving portion 201 and the contact portion with the heat dissipation portion 202.

[0037] According to such a thermoelectric conversion module 100, by forming the grooves 3 in the substrate 1, During doping of the carbon nanotube yarn 2, the portions of the carbon nanotube yarn 2 where the heat receiving portion 201 and the heat dissipation portion 202 are to be formed can be kept out of contact with the substrate 1. This prevents the doping solution from seeping out due to capillary action between the carbon nanotube yarn 2 and the substrate 1, making it possible to appropriately dye the P-type portion 21P and the N-type portion 21N differently. As a result, the electromotive force of the carbon nanotube yarn 2 is improved compared to when no grooves are formed in the substrate 1, thereby improving the power generation efficiency of the thermoelectric conversion module 100. Here, the grooves 3 may be formed in at least one of the portions of the substrate 1 that contact the heat receiving portion 201 and the portions that contact the heat dissipation portion 202, but it is preferable to form the grooves 3 in both, which allows the P-type portion 21P and the N-type portion 21N to be more appropriately dyed differently.

[0038] Here, the carbon nanotube yarn 2 is preferably wound around the substrate 1 at intervals of 0.12 mm or more in the extension direction of the substrate 1. Specifically, the pitch P (see Figures 2 and 3), which is the surface distance between adjacent portions of the carbon nanotube yarn 2 in the extension direction of the substrate 1 and at the same circumferential position, is preferably 0.12 mm or more. This makes it possible to suppress seepage of the doping solution due to capillary action between adjacent portions of the carbon nanotube yarn 2 in the extension direction of the substrate 1 during doping. As a result, it becomes possible to more appropriately dye the P-type portion 21P and the N-type portion 21N. Note that, from the viewpoint of ensuring the number of turns of the carbon nanotube yarn 2 and ensuring power generation efficiency, it is preferable to set the pitch P to 1 mm or less.

[0039] Furthermore, in the thermoelectric conversion module 100 according to this embodiment, by interposing the base material 1 having thermal insulation between the heat receiving portion 201 and the heat dissipation portion 202, 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, can be ensured. As a result, the thermoelectric conversion efficiency can be improved. 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 thermal insulation properties of the base material 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.

[0040] 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.

[0041] 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.

[0042] Moreover, the carbon nanotube yarn 2 of the thermoelectric conversion module 100 according to this embodiment is , and is formed as an untwisted yarn in which a plurality of carbon nanotubes 211 are oriented in one direction and aggregated. Accordingly, by using an untwisted yarn in which a plurality of carbon nanotubes 211 are oriented in the drawing 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 making the carbon nanotube yarn 2 an untwisted yarn, in the heat receiving section 201 and the heat dissipating section 202, the first direction D, which is the direction from the heat receiving section 201 to the heat dissipating section 202, is perpendicular to the orientation direction D2 of the carbon nanotubes 211, so that the temperature difference between the heat receiving section 201 and the heat dissipating section 202 can be more suitably ensured. However, the carbon nanotube yarn according to the present invention does not need to have a plurality of carbon nanotubes oriented in one direction, and it does not need 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.

[0043] 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.

[0044] [Variations] The following describes substrates 1A to 1E used in thermoelectric conversion modules according to modifications of the embodiment. The following description focuses on differences from the substrate 1 described above, and omits a description of similarities with the substrate 1. FIG. 8 is a cross-sectional view of substrates 1A to 1E used in thermoelectric conversion modules according to modifications of the embodiment, corresponding to modifications 1 to 5 of the embodiment. The substrate 1A according to modification 1 shown in FIG. 8(A) has a semicircular cross-sectional shape of the groove 3. The substrate 1B according to modification 2 shown in FIG. 8(B) has C-chamfered corners, and the substrate 1C according to modification 3 shown in FIG. 8(C) has R-chamfered corners. The substrate 1D according to modification 4 shown in FIG. 8(D) has a hexagonal cross-sectional shape. The substrate 1E according to modification 5 shown in FIG. 8(E) has a circular cross-sectional shape.

[0045] <Confirmation test of generated voltage> A test was conducted to confirm the effect of passing cooling water on improving the generated voltage for the example and comparative example. The example used a thermoelectric conversion module equivalent to the thermoelectric conversion module 100 according to the embodiment. The comparative example differed from the example in that the grooves 3 were not formed in the substrate 1, but in other respects used a thermoelectric conversion module similar to the example.

[0046] In the confirmation test, examples and comparative examples were produced by doping using the immersion method, and the generated voltage (electromotive force) of each was measured. For doping, one side of a substrate (hereinafter referred to as a wound body) with a carbon nanotube yarn was brought into contact with an N-type doping solution in a tray for approximately 5 minutes, and then the wound body was inverted and the other side (the side opposite to the one side) was brought into contact with a P-type doping solution in a tray for approximately 5 minutes. The generated voltage was measured by sandwiching the examples and comparative examples between two Peltier controllers and applying a load of 50 to 55 [N]. One Peltier controller was used as a hot heat source, and the other Peltier controller was used as a cold heat source, creating a temperature difference in the thermoelectric conversion module to generate electricity. The temperature of the Peltier controller serving as the hot heat source was set to 45 [°C], and the temperature of the Peltier controller serving as the cold heat source was set to 25 [°C].

[0047] Table 1 shows the generated voltages in the example and the comparative example. As a result of the measurement, the generated voltage in the example was 82 [μV / K]. The generated voltage in the comparative example was 2.2 [μV / K]. The generated voltage in the example was about 37 times that of the comparative example. This confirmed the effect of improving power generation efficiency by forming the grooves 3 in the substrate 1. [Table 1]

[0048] <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]

[0049] 1: Base material 2: Carbon nanotube yarn 21P:P type part 21N:N type part 211: Carbon nanotubes 3: Groove 20: Spiral 20a: 1st turn 201:Heat receiving part 202: Heat radiation part 100: 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, a plurality of P-type portions and a plurality of N-type portions are formed in the thermoelectric conversion member by a doping process, and the P-type portions and the N-type portions are alternately arranged and continuously formed in an 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, The base material has a groove portion extending along an extending direction of the base material and forming a gap between the thermoelectric conversion member and the base material, the groove portion being formed in at least one of a contact portion with the heat receiving portion and a contact portion with the heat dissipation portion. Thermoelectric conversion module.

2. the grooves are formed in both a contact portion with the heat receiving portion and a contact portion with the heat dissipating portion of the base material; 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. a boundary between the P-type portion and the N-type portion is formed at a position facing the groove portion; The thermoelectric conversion module according to claim 1 or 2.

5. the thermoelectric conversion member is wound around the base material at intervals of 0.12 mm or more in the extending direction of the base material; The thermoelectric conversion module according to claim 1 or 2.

Images