Thermoelectric conversion module

Abstract

To generate a larger voltage even when a temperature difference between a heat receiving side and a heat releasing side is small.SOLUTION: There is provided a thermoelectric conversion module 100 including a heat receiving part and a heat releasing part and generating electricity using a temperature difference between the heat receiving part and the heat releasing part. The thermoelectric conversion module includes a base material 1 extending in a predetermined direction and a thermoelectric conversion member 2 spirally wound onto the base material 1. One side of a spiral body 20 formed by the thermoelectric conversion member 2 is formed as the heat receiving part, and the other side opposite to the one side with the base material 1 sandwiched therebetween is formed as the heat releasing part. The thermoelectric conversion module further includes a cooling part 300 that is in contact with the heat releasing part, that can hold a vaporization medium and that has an insulation layer.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, a thermoelectric conversion module made of a carbon nanotube nonwoven fabric in a spiral shape is 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. 2007-324148 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to generate a large amount of power from 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, and if a sufficient temperature difference cannot be ensured, there is a problem that the generated voltage decreases. Furthermore, if the temperature difference between the heat-receiving side and the heat-dissipating side of the thermoelectric conversion element is small, there is a problem that the temperature on the heat-dissipating side gradually increases, further reducing the power generation efficiency.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a technology that can increase the voltage generated in a thermoelectric conversion module even when the temperature difference between the heat receiving side and the heat dissipating 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 extending in a predetermined direction; 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 cooling unit that is in contact with the heat dissipation unit, is capable of holding an evaporation medium, and has an insulating layer; 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 cooling unit includes an absorption layer that absorbs the vaporization medium. The thermoelectric conversion module according to [1] or [2]. [5] The cooling unit is disposed closer to the substrate than the absorption layer and includes a blocking layer that blocks the evaporation medium. [4] The thermoelectric conversion module according to [4]. [6] The cooling unit includes a cooling plate disposed closer to the base material than the absorption layer. [4] The thermoelectric conversion module according to [4]. [7] the cooling unit includes a cooling plate that is disposed closer to the base material than the absorption layer, The insulating layer is disposed closer to the base material than the cooling plate. [4] The thermoelectric conversion module according to [4]. [8] a vaporization medium supply unit that supplies the vaporization medium to the absorption layer; [4] The thermoelectric conversion module according to [4]. [Effects of the Invention]

[0007] According to the present invention, it is possible to increase the voltage generated even when the temperature difference between the heat receiving side and the heat radiating side is small. [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 cross-sectional view illustrating the configuration of a cooling unit according to the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view illustrating the configuration of a cooling unit according to a 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 showing 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 that schematically shows 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. In the up-down direction and left-right direction, The direction perpendicular to the direction of the heat receiving portion 201 is the front-rear direction of the thermoelectric conversion module 100. 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. FIG. 1 illustrates a cross section perpendicular to the front-rear direction. 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. Note that FIG. 3 illustrates a top view with a cooling unit 300, which will be described later, transparent. Here, in FIG. 1, the direction from the heat receiving portion 201 toward the heat dissipation portion 202 (downward in this embodiment) is defined as a first direction D. The first direction D is the direction of heat transfer when heat transfers from the heat receiving portion 201 to the heat dissipation portion 202 over 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 placed on a heat source 200. The thermoelectric conversion module 100 has a cooling unit 300 on top. The heat source 200 is a heat source for supplying heat to the thermoelectric conversion module 100. The cooling unit 300 uses a vaporizable medium to release heat from the thermoelectric conversion module 100. The heat source 200 has a higher temperature than the cooling unit 300. The thermoelectric conversion module 100 has a heat receiving unit 201 that receives heat from the outside and a heat dissipation unit 202 that dissipates heat to the cooling unit 300. The heat receiving unit 201 is formed on the bottom of the thermoelectric conversion module 100 so as to be in contact with the heat source 200, and the heat dissipation unit 202 is formed on the top of the thermoelectric conversion module 100 so as to be in contact with the cooling unit 300. The heat receiving section 201 receives heat from the heat source 200, and the heat dissipation section 202 dissipates the heat to the cooling section 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.

[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." Furthermore, the shape of the substrate according to the present invention is not limited to a prismatic column with 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 with 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 long sides in the direction from the heat receiving section 201 toward 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 is in contact with the heat source 200, and the horizontal side 1d is in contact with the cooling section 300. .

[0015] [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.

[0016] 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.

[0017] 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.

[0018] 4 indicates a boundary between an end of the P-type portion 21P and an 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). 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 portion C1 is formed as a boundary portion where the P-type portion 21P and the N-type portion 21N switch over. Note that the boundary portion C1 may be made of another conductor.

[0019] 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.

[0020] As shown in FIG. 5, the P-type portion 21P forms the right half of the one turn portion 20a of the spiral 20, and the N-type portion 21N forms the left 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. By arranging the boundary portions C1 alternately in this way, the lower portion of the spiral 20 is formed as a heat receiving portion 201, and the upper 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. The heat receiving portion 201 may be a region of the spiral body 20 that contacts the lower surface of the substrate 1 corresponding to the horizontal side 1c of the substrate 1 shown in Fig. 1. The heat dissipating portion 202 may be a region of the spiral body 20 that contacts the upper surface of the substrate 1 corresponding to the horizontal side 1d of the substrate 1 shown in Fig. 1.

[0021] Each of the plurality of 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 plurality of 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 plurality of 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 the heat source 200 arranged below the thermoelectric conversion module 100, and the heat dissipation portion 202 is in contact with the cooling portion 300 arranged above the thermoelectric conversion module 100.

[0022] Doping to impart semiconducting properties to the carbon nanotube yarn 2 is performed with the carbon nanotube wire wound spirally around the substrate 1. When only N-type doping is performed, the left 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, each half turn long. When both doping and P-type doping are performed, the right half of the carbon nanotube wire wound around the substrate 1 is immersed in a solution containing a P-type doping agent, and the left 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.

[0023] 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 also be a nonwoven fabric of carbon nanotubes formed into a strip shape. This carbon nanotube nonwoven fabric may be doped with only an N-type dopant out of an N-type dopant and a P-type dopant, or may be doped with both an N-type dopant and a P-type dopant.

[0024] [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.

[0025] [Cooling section] FIG. 6 is a cross-sectional view illustrating the configuration of the cooling unit 300 according to the first embodiment. A cross section perpendicular to the front-rear direction is illustrated in FIG. 6. The cooling unit 300 is disposed above the heat dissipation unit 202 so as to be in contact with the heat dissipation unit 202. As shown in FIG. 3, the cooling unit 300 is formed to cover the spiral 20 from above in the front-rear and left-right directions of the spiral 20. However, a configuration in which a portion of the spiral 20 is not in contact with the cooling unit 300 is also possible. The lengths of the cooling unit 300 in the front-rear and left-right directions do not need to be matched to the shape of the spiral 20. For example, the length of the cooling unit 300 in the front-rear direction may be longer than the length of the spiral 20 in the front-rear direction, or the length of the cooling unit 300 in the left-right direction may be longer than the length of the spiral 20 in the left-right direction. The cooling unit 300 has, from the top down, a water absorption layer 301 (an example of the "absorption layer" according to the present invention), a cooling plate 302, a waterproof layer 303 (an example of the "blocking layer" according to the present invention), and an insulating layer 304. The water absorption layer 301 is a member capable of retaining water. The water absorption layer 301 is also configured so that the retained water evaporates. The water absorption layer 301 can be made of a material such as cloth (e.g., woven or nonwoven fabric), sponge, diatomaceous earth, or a water-absorbent polymer. However, the material of the water absorption layer 301 is not limited to these. The water absorption layer 301 can be formed of, for example, a water-absorbent material (for example, a porous material).

[0026] Water is supplied to the water absorption layer 301 by a water supply unit 400 (an example of a "vaporization medium supply unit" according to the present invention). Water is an example of a "vaporization medium" according to the present invention. However, the vaporization medium is not limited to water. For example, any liquid other than water that is easily vaporized and highly safe can be used. For example, alcohol can be used as the vaporization medium. As another example, a liquid in which water is mixed with alcohol can be used as the vaporization medium. The water supply unit 400 may include, for example, a water storage tank. The water supply unit 400 may supply water from the water storage tank to the water absorption layer 301 via, for example, a tube. As another example, the water supply unit may supply water from the water storage tank to the water absorption layer 301 by using a natural head of water. As yet another example, the water supply unit may supply water from the water storage tank to the water absorption layer 301 by dripping or by using capillary action. The water supply unit 400 is not necessarily required. For example, the cooling unit 300 may be configured so that a user can directly supply water to the water absorption layer 301. The water supply unit 400 may supply water to the water absorption layer 301 constantly or at a predetermined timing. The predetermined timing may be, for example, at predetermined intervals or when the generated voltage falls below a threshold.

[0027] The cooling plate 302 is a component with a heat transfer function. The cooling plate 302 is formed of a material with relatively high thermal conductivity to enhance heat dissipation. Examples of materials for the cooling plate 302 include metal foil, metal plate, ceramic plate, and porous metal. The ceramic plate may be a highly thermally conductive ceramic plate. If the cooling plate 302 is formed of a metal material, there is a risk of deterioration due to rust or corrosion. Therefore, the cooling plate 302 may be formed of a rust-resistant aluminum alloy or a non-metallic material (e.g., a highly thermally conductive ceramic plate). The waterproof layer 303 is a component with a waterproof function. The waterproof layer 303 blocks the flow of water, which is the evaporation medium, to prevent it from penetrating the substrate 1. This allows for sustained power generation efficiency over a long period of time. If an evaporation medium other than water is used, the waterproof layer 303 is formed of a material that blocks the evaporation medium used. Examples of materials for the waterproof layer 303 include polymer film. The insulating layer 304 is an insulating member, and may be made of a polymer film.

[0028] In the cooling unit 300 configured in this manner, heat is transferred from the heat dissipation unit 202 to the insulating layer 304, the waterproof layer 303, and the cooling plate 302, causing the temperature of the cooling plate 302 to rise. Meanwhile, as the water supplied to the water absorption layer 301 by the water supply unit evaporates, the water absorption layer 301 absorbs heat from the cooling plate 302 due to the heat of vaporization. Therefore, the evaporation of water in the water absorption layer 301 allows the temperature of the heat dissipation unit 202 to be maintained low.

[0029] In the example shown in FIG. 6 , the waterproof layer 303 and the insulating layer 304 are formed separately. However, this is not a limitation, and a single layer may be formed that combines the functions of both the waterproof layer 303 and the insulating layer 304. In the example shown in FIG. 6 , the cooling plate 302 and the waterproof layer 303 are formed separately. However, this is not a limitation, and a single layer may be formed that combines the functions of both the cooling plate 302 and the waterproof layer 303. The cooling plate 302 only needs to be located above the insulating layer 304. In the example shown in FIG. 6 , the cooling plate 302, the waterproof layer 303, and the insulating layer 304 are formed separately. However, by using, for example, highly thermally conductive ceramics, the cooling plate 302, the waterproof layer 303, and the insulating layer 304 can be formed as a single layer. In other words, by forming a single layer using highly thermally conductive ceramics that have high thermal conductivity, waterproofness, and insulating properties, all of the functions of the cooling plate 302, the waterproof layer 303, and the insulating layer 304 can be achieved. 6, the cooling plate 302 is provided, but the cooling plate 302 is not necessarily required. For example, the water absorbing layer 301 can also directly absorb heat from the waterproof layer 303.

[0030] [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 with the spiral 20 disposed between the heat source 200 and the cooling unit 300. The heat receiving unit 201 of the thermoelectric conversion module 100 is in contact with the heat source 200 and is heated by receiving heat from the heat source 200. On the other hand, the heat dissipation unit 202 of the thermoelectric conversion module 100 is in contact with the cooling unit 300 and is cooled by dissipating heat to the cooling unit 300. As a result, the heat receiving unit 201 has a higher temperature than the heat dissipation unit 202, resulting in a temperature difference between the heat receiving unit 201 and the heat dissipation unit 202. As described above, the P-type portion 21P and the N-type portion 21N constituting the carbon nanotube yarn 2 are arranged such that one end of each is included in the heat receiving unit 201 and the other end is included in the heat dissipation unit 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.

[0031] 1, in the thermoelectric conversion module 100, one side (lower part) of the spiral 20 formed by the carbon nanotube yarn 2 is formed as the heat receiving part 201, and the other side (upper part) opposite the heat receiving part 201 across the substrate 1 is formed as the heat dissipation part 202. That is, the heat receiving part 201 and the heat dissipation part 202 are formed on opposite sides (lower and upper sides) of the heat insulating substrate 1. The heat insulating substrate 1 is interposed between the heat receiving part 201 and the heat dissipation part 202, thereby suppressing heat transfer from the heat receiving part 201 to the heat dissipation part 202. Furthermore, since the heat dissipation part 202 can be cooled by the water absorption layer 301, the temperature difference between the heat receiving part 201 and the heat dissipation part 202, i.e., the temperature difference between both ends of the P-type part 21P and the N-type part 21N, can be increased. This allows for a higher generated voltage.

[0032] Furthermore, since the waterproof layer 303 is disposed below the water absorption layer 301 (i.e., on the substrate 1 side), adhesion of water to the carbon nanotube yarn 2 can be suppressed. Therefore, the P-type portion 21P and the N-type portion 21N are prevented from being electrically connected to each other at locations other than the boundary portion C1. Furthermore, since the insulating layer 304 is interposed between the waterproof layer 303 and the carbon nanotube yarn 2, the P-type portion 21P and the N-type portion 21N are prevented from being electrically connected to each other via the waterproof layer 303. In this way, the P-type portion 21P and the N-type portion 21N are maintained in an electrically connected state in series.

[0033] Furthermore, since the cooling plate 302 is disposed below the water absorption layer 301 (i.e., on the substrate 1 side), the water absorption layer 301 can more efficiently remove heat from the heat dissipation section 202. In other words, since the temperature of the heat dissipation section 202 can be further reduced, the temperature difference between both ends of the P-type section 21P and the N-type section 21N can be further increased, and the generated voltage can be increased.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] [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 the one side with the substrate 1 in between is formed as a heat dissipation portion 202. The cooling portion 300 is arranged in contact with the heat dissipation portion 202. The cooling portion 300 has a water absorbing layer 301.

[0038] In this thermoelectric conversion module 100, the water absorption layer 301 cools the heat dissipation section 202, thereby increasing the temperature difference between the heat receiving section 201 and the heat dissipation section 202, i.e., the temperature difference between both ends of the P-type section 21P and the N-type section 21N. As a result, the thermoelectric conversion module 100 according to this embodiment can generate a higher voltage. 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 section 201 and the heat dissipation section 202 due to the insulating properties of the base material 1. Therefore, the thermoelectric conversion module 100 can ensure a temperature difference between the heat receiving section 201 and the heat dissipation section 202 while increasing the electrical conductivity of the carbon nanotube yarn 2. This allows a higher voltage to be obtained. In other words, the thermoelectric conversion module 100 can achieve both high electrical conductivity and high generated voltage. 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.

[0039] 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.

[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] 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.

[0043] 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.

[0044] 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.

[0045] 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 fit 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 pipes in a factory or home to generate electricity.

[0046] Furthermore, when a mixture of two or more liquids with different vaporizabilities is used as the vaporization medium, the duration of the effect and the generated voltage can be adjusted by adjusting the mixture ratio. For example, when a mixture of water and alcohol is used as the vaporization medium, alcohol vaporizes more easily than water, so increasing the mixture ratio of alcohol shortens the duration of the effect. Increasing the mixture ratio of alcohol increases the difference between the temperatures of the heat receiving portion 201 and the heat radiating portion 202, and increases the generated voltage.

[0047] <Embodiment 2> FIG. 7 is a cross-sectional view illustrating the configuration of the cooling unit 300 according to the second embodiment. A cross section perpendicular to the front-rear direction is illustrated in FIG. 7. The configuration of other components is the same as that shown in FIG. 6. The cooling unit 300 includes, from top to bottom, a water absorption layer 301, a cooling plate 312, and an insulating layer 304. The water absorption layer 301 and the insulating layer 304 are the same as those in the first embodiment, and therefore their description will be omitted. The cooling plate 312 according to the second embodiment also functions as a waterproof layer. Aluminum is an example of a material for the cooling plate 312. Aluminum has high thermal conductivity, which makes it easy to transfer heat from the heat dissipation unit 202 to the water absorption layer 301. Furthermore, aluminum's waterproof properties prevent water from penetrating the water absorption layer 301 into the spiral 20.

[0048] As described above, according to the cooling unit 300 of the second embodiment, the heat dissipation unit 202 can be cooled by the cooling unit 300. As a result, the temperature difference between the heat receiving unit 201 and the heat dissipation unit 202 can be increased, and a high voltage can be generated. In addition, the number of parts in the cooling unit 300 can be reduced.

[0049] <Confirmation test of generated voltage> Tests were conducted to confirm the effect of improving power generation voltage for the examples and comparative examples. The examples used a thermoelectric conversion module equivalent to the thermoelectric conversion module 100 according to embodiment 2. In both the examples and comparative examples, gauze was used as the water absorption layer, a single aluminum plate was used as the cooling plate and waterproof layer, and a polymer film was used as the insulating layer. A hot plate was used as the heat source. A thermoelectric conversion module was placed on the top surface of the hot plate to apply heat to the thermoelectric conversion module. A thermocouple was placed between the aluminum plate and the polymer film to measure the temperature of the heat dissipation section. A thermocouple was also placed on the top surface of the hot plate to measure the temperature of the heat receiving section. Water and ethanol were used as evaporation media. Water or ethanol was dripped onto the gauze, allowing the gauze to absorb the water or ethanol. Data was obtained using the state before dripping the water or ethanol onto the gauze as a comparative example. When forming the thermoelectric conversion module, a polymer film was attached to the top surface of the spiral, a thermocouple was placed on the top surface of the polymer film to measure the temperature of the heat dissipation section 202, and an aluminum plate was placed on the polymer film and thermocouple. Furthermore, gauze was placed on the aluminum plate.

[0050] A temperature difference was applied to the thermoelectric conversion module by applying current to the hot plate, generating electricity. The voltage, heat receiving part temperature, and heat radiating part temperature were measured. This measurement was performed before the water or ethanol was dripped onto the gauze. After the heat receiving part temperature reached 30°C, the water or ethanol was dripped onto the gauze. The temperature of the water or ethanol at the time of dripping was approximately 22°C, which is almost the same as the air temperature. The temperature was ℃. Water or ethanol was added dropwise using a dropper. The temperature of the ethanol was approximately 22°C, but compared to the size (volume and mass) of the aluminum plate, the amount of water or ethanol dripped was only 0.3 cc, so the temperature of the evaporation medium itself had almost no effect on lowering the temperature of the heat dissipation section.

[0051] The ratio of the generated voltage to the generated voltage of the comparative example was calculated as the effectiveness rate [%]. The temperature reduction effect [%] was calculated by dividing the difference between the temperature difference between the heat receiving part and the heat radiating part in the comparative example and the temperature difference between the heat receiving part and the heat radiating part in the example. The temperature reduction effect was calculated as [°C]. Table 1 shows the efficiency rate and the temperature reduction effect in the examples and comparative examples. In Table 1, the efficiency rate before the vaporization medium is dropped shows a comparative example, and the efficiency rate after the vaporization medium is dropped shows an example. [Table 1]

[0052] As shown in Table 1, when ethanol was used as the vaporization medium, the efficiency was 279[ %], and the temperature reduction effect was -5.1 [°C]. As a result, 2.79 times the voltage was generated. Furthermore, in the Example, the temperature difference between the heat receiving section and the heat radiating section was 5.1°C greater than in the Comparative Example. Furthermore, when water was used as the vaporization medium, the efficiency rate was 247% and the temperature reduction effect was -4.1°C. In other words, in the Example, 2.47 times the voltage was generated compared to the Comparative Example. Furthermore, in the Example, the temperature difference between the heat receiving section and the heat radiating section was 4.1°C greater than in the Comparative Example. Thus, for both water and ethanol, the Example had a higher temperature reduction effect than the Comparative Example, resulting in improved power generation voltage. This confirmed that the heat of vaporization of water and ethanol improves power generation efficiency.

[0053] It was also confirmed that as the evaporation of the vaporizing medium progresses and the remaining amount decreases, the heat of vaporization decreases and the temperature of the heat dissipation section rises. It was also confirmed that ethanol vaporizes more easily than water, so the duration of its effect is shorter. With ethanol, the effect weakened after about 10 minutes, but with water, the effect continued for about 100 minutes. On the other hand, it was confirmed that the difference between the temperature of the heat receiving section and the temperature of the heat dissipation section was larger with ethanol than with water, and that the generated voltage was also larger. This confirmed that the magnitude of the latent heat of vaporization of the vaporizing medium does not affect the generated voltage.

[0054] <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]

[0055] 1: Base material 2: Carbon nanotube yarn 21N:N type part 21P :P type part 100: Thermoelectric conversion module 200: Heat source 201:Heat receiving part 202: Heat dissipation part 300: Cooling section 301: Water absorption layer 302: Cooling plate 303: Waterproof layer 304: Insulating layer

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 extending in a predetermined direction; 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 cooling unit that is in contact with the heat dissipation unit, is capable of holding an evaporation medium, and has an insulating layer; 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 cooling unit includes an absorption layer that absorbs the vaporization medium. The thermoelectric conversion module according to claim 1 or 2.

5. The cooling unit is disposed closer to the substrate than the absorption layer and includes a blocking layer that blocks the evaporation medium. The thermoelectric conversion module according to claim 4 .

6. The cooling unit includes a cooling plate disposed closer to the base material than the absorption layer. The thermoelectric conversion module according to claim 4 .

7. the cooling unit includes a cooling plate that is disposed closer to the base material than the absorption layer, The insulating layer is disposed closer to the base material than the cooling plate. The thermoelectric conversion module according to claim 4 .

8. a vaporization medium supply unit that supplies the vaporization medium to the absorption layer; The thermoelectric conversion module according to claim 4 .

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