Patent Application
20100326487
The present invention relates to thermoelectric elements and thermoelectric devices that convert thermal energy into electrical energy.
Thermoelectric generation technology is a technology for directly converting thermal energy into electrical energy using the Seebeck effect, in which an electromotive force is generated in proportion to a temperature difference created between both ends of a substance. This technology has been used practically, for example, for a remote area power supply, an outer space power supply, and a military power supply.
The performance of a thermoelectric conversion material used for a thermoelectric device often is evaluated by a figure of merit Z, or a figure of merit ZT that is obtained by multiplying a figure of merit Z by absolute temperature to be non-dimensionalized. The figure of merit ZT can be expressed as ZT=S2T/ρκ, where S is a Seebeck coefficient, ρ is electrical resistivity, and κ is thermal conductivity, of a substance. The FIG. S2/ρ, which is expressed by the Seebeck coefficient S and electrical resistivity ρ, is a value referred to as a power factor. The power factor is used as a measure for determining the quality of the power generation performance of, for example, the thermoelectric conversion material and the thermoelectric device under a constant temperature difference.
A Bi-based material that currently is used practically as a thermoelectric conversion material has relatively high properties with a ZT of approximately 1 and a power factor of 40 to 50 μW/cmK2 under the present conditions. However, an ordinary π-type thermoelectric device containing the Bi-based material used therein cannot be said to have a sufficiently high power generation performance for being used in a wider range of applications. The π-type thermoelectric device is a device with a configuration in which a thermoelectric conversion material composed of a p-type semiconductor and a thermoelectric conversion material composed of n-type semiconductor, having carriers of opposite signs, are connected to each other so as to be thermally in parallel and electrically in series. Furthermore, an example of the thermoelectric device other than that of the π type is a thermoelectric device that takes advantage of the anisotropy of thermoelectric properties of natural or artificially-produced layered structures, which has long been proposed (see, for example, Non-Patent Literature 1). However, even this thermoelectric device cannot be said to have a sufficiently high power generation performance. Moreover, Patent Literature 1 describes a thermoelectric device that has two electrodes and a laminate that is interposed between the two electrodes and is composed of Bi2Te3 layers and metal layers that are layered alternately, with a layer surface of the laminate being inclined with respect to the direction in which the two electrodes are opposed to each other. This thermoelectric device has a high power generation performance.
However, since the conventional thermoelectric device has a flat plate shape, there has been a problem that it cannot transfer heat efficiently with respect to a heat source with a curved surface, such as a columnar heat source.
The present invention was made with the above situation in mind and is intended to provide thermoelectric elements and thermoelectric devices that can transfer heat efficiently with respect to, for example, heat sources with a curved surface, such as columnar heat sources.
The present inventors made various studies and found that the above-mentioned object was achieved by the following present invention. That is, a thermoelectric element of the present invention includes a laminate with two different types of thermoelectric conversion materials that are layered alternately from one end to the other end, and a first electrode and a second electrode that are disposed at both ends of the laminate, respectively, wherein the laminate has a shape surrounding a straight line axis from the one end to the other end, when viewed from the direction along the axis, the laminate has an inner circumference with a circular or arc shape and each boundary between respective layers formed of the two different types of thermoelectric conversion materials is disposed in such a manner as to separate from a straight line as the boundary approaches an outer circumference from the inner circumference of the laminate, where the straight line passes an inner circumference-side edge point of the boundary, with the axis being a starting point thereof.
Furthermore, a thermoelectric device of the present invention includes a plurality of thermoelectric elements, wherein the plurality of thermoelectric elements each include a laminate with two different types of thermoelectric conversion materials that are layered alternately from one end to the other end, the laminate has a shape surrounding a straight line axis from the one end to the other end, when viewed from the direction along the axis, the laminate has an inner circumference with a circular or arc shape and each boundary between respective layers formed of the two different types of thermoelectric conversion materials is disposed in such a manner as to separate from a straight line as the boundary approaches an outer circumference from the inner circumference of the laminate, where the straight line passes an inner circumference-side edge point of the boundary, with the axis being a starting point thereof., and the plurality of thermoelectric elements are connected to each other electrically in series.
Moreover, a thermoelectric device of the present invention includes a plurality of thermoelectric elements, wherein the plurality of thermoelectric elements each include a laminate with two different types of thermoelectric conversion materials that are layered alternately from one end to the other end, the laminate has a shape surrounding a straight line axis from the one end to the other end, when viewed from the direction along the axis, the laminate has an inner circumference with a circular or arc shape and each boundary between respective layers formed of the two different types of thermoelectric conversion materials is disposed in such a manner as to separate from a straight line as the boundary approaches an outer circumference from the inner circumference of the laminate, where the straight line passes an inner circumference-side edge point of the boundary, with the axis being a starting point thereof, and the plurality of thermoelectric elements are connected to each other electrically in parallel.
From another aspect, the present invention also provides a thermoelectric element including a laminate formed of a material that contains two different types of thermoelectric conversion materials layered alternately from one end to the other end and that is disposed so as to incline towards an outer circumference from an inner circumference of the material with respect to a straight line extending between a center point surrounded by the material and a point on a boundary between the two different types of thermoelectric conversion materials on the inner circumference of the material, a first electrode disposed at the one end, and a second electrode disposed at the other end. In this case, the laminate has a shape surrounding a straight line axis while extending from one end to the other end. The center point is the axis when the laminate is viewed from the direction along the axis. Furthermore, when the laminate is viewed from the direction along the axis, the respective thermoelectric conversion materials are disposed in such a manner as to separate towards the outer circumference from the inner circumference of the laminate with respect to a straight line extending between the center point and a point on a boundary between the two different types of thermoelectric conversion materials on the inner circumference of the laminate.
The thermoelectric elements and thermoelectric devices of the present invention are practical because they can transfer heat efficiently with respect to heat sources with a curved surface, such as columnar heat sources, and also have high power generation properties. The present invention promotes application of energy conversion between heat and electricity and therefore has a high industrial value.
The present invention can provide thermoelectric elements and thermoelectric devices that can transfer heat efficiently with respect to, for example, heat sources with a curved surface, such as columnar heat sources.
Hereinafter, embodiments of the present invention are described with reference to the drawings.
Preferably, a thermoelectric conversion material composing the first thermoelectric conversion material layers 14 and a thermoelectric conversion material composing the second thermoelectric conversion material layers 15 are different from each other and have large differences in thermal conductivity K and Seebeck coefficient S from each other. This allows the thermoelectric element 10 to generate a large amount of electricity. Furthermore, it is preferable that the thermoelectric conversion materials each have a low electrical resistivity. For example, the thermoelectric conversion materials each are preferably metal and specifically may be a material containing Bi, a material containing Bi and Te, a material containing Pb and Te, or Cu, Ag, Au, or Al. Preferably, one of the thermoelectric conversion materials is a material containing Bi, a material containing Bi and Te, or a material containing Pb and Te. In that case, the other is preferably Cu, Ag, or Au and particularly preferably Cu or Ag. Furthermore, the material containing Bi and Te is preferably Bi2Te3, and the material containing Pb and Te is preferably PbTe. These materials may deviate in composition according to the production condition, but it is acceptable as long as the followings hold: Bi2Tex. (2<x<4) and PbTey (0<y<2).
The materials used for the first electrode 11 and the second electrode 12 are not particularly limited as long as they have high electrical conductivity. Specifically, the first electrode 11 and the second electrode 12 can be formed using metal such as Cu, Ag, Mo, W, Al, Ti, Cr, Au, Pt, or In, nitride such as TiN, or oxide such as indium tin oxide (ITO) or SnO2. Furthermore, the first electrode 11 and the second electrode 12 may be formed using, for example, a solder, a silver brazing, or a conductive paste.
Since air is present in the space 21 to provide electrical insulation, the laminate 13 does not short-circuit. Furthermore, air is preferable because it has high thermal insulation properties and therefore can reduce heat loss from the space 21. Moreover, the space 21 may be filled with an electrical insulator. This increases the strength of the thermoelectric element 10. The insulator can be, for example, an epoxy resin, paraffin, rubber polyvinyl chloride, alumina, or glass but an epoxy resin is preferable because it has high thermal insulation properties.
The present inventors studied various conditions with respect to the thermoelectric element 10, examined the relationship with the thermoelectric performance in detail, and thereby tried to optimize the thermoelectric element 10. As a result, they found that when the angle θ, the ratio of the inner circumferential angles of the first thermoelectric conversion material layers 14 and the second thermoelectric conversion material layers 15, and the ratio of the inner and outer diameters of the laminate 13 were set suitably according to the material composing the second thermoelectric conversion material layers 15, the thermoelectric element 10 obtained a high power generation performance. In this case, the inner circumferential angles are values that indicate the thicknesses of the first thermoelectric conversion material layers 14 and the second thermoelectric conversion material layers 15 in the circumferential direction in the inner circumference of the laminate 13 when the laminate 13 is viewed from the direction along the axis 19, in terms of the angles formed with the axis 19 being the vertex (see
Preferably, the material composing the second thermoelectric conversion material layers 15 contains Bi. In this case, it is particularly preferable that the angle θ be 30° to 120°. Furthermore, the ratio of the inner circumferential angles of the first thermoelectric conversion material layer 14 and the second thermoelectric conversion material layer 15 is preferably in the range of 0.2:1 to 250:1 and particularly preferably in the range of 5:1 to 20:1. Moreover, the ratio of the inner and outer diameters of the laminate 13 is preferably in the range of 1:1.1 to 1:100 and particularly preferably in the range of 1:1.5 to 1:2.
Preferably, the material composing the second thermoelectric conversion material layers 15 contains Bi and Te. In this case, it is particularly preferable that the angle θ be 60° to 90°. Furthermore, the ratio of the inner circumferential angles of the first thermoelectric conversion material layer 14 and the second thermoelectric conversion material layer 15 is preferably in the range of 0.05:1 to 250:1 and particularly preferably in the range of 5:1 to 40:1. Moreover, the ratio of the inner and outer diameters of the laminate 13 is preferably in the range of 1:1.1 to 1:10 and particularly preferably 1:1.5.
Preferably, the material composing the second thermoelectric conversion material layers 15 contains Pb and Te. In this case, it is particularly preferable that the angle θ be 60° to 90°. Furthermore, the ratio of the inner circumferential angles of the first thermoelectric conversion material layer 14 and the second thermoelectric conversion material layer 15 is preferably in the range of 0.2:1 to 100:1 and particularly preferably in the range of 5:1 to 40:1. Moreover, the ratio of the inner and outer diameters of the laminate 13 is preferably in the range of 1:1.05 to 1:10 and particularly preferably in the range of 1:1.2 to 1:1.5.
With respect to each material composing the second thermoelectric conversion material layers 15, when the respective conditions are in the above-mentioned ranges, the thermoelectric element 10 has very practical values of power factor.
In order to produce the thermoelectric element 10, first, the structure retainer 32 shown in
As shown in
Thereafter, the first electrode 11 and the second electrode 12 are formed at both ends of the laminate 13, respectively. Thus, the thermoelectric element 10 shown in
The method of producing the thermoelectric element 10 according to the present invention is not limited particularly to the above-mentioned method as long as it is a method that provides the structure of the thermoelectric element 10. For example, by cutting and polishing not only the thermoelectric conversion material layer pieces 31 but also the material composing the second thermoelectric conversion material layers 15, the thermoelectric conversion material layer pieces having the same shape as that of the second thermoelectric conversion material layers 15 are produced and are then bonded to one another by compression bonding, and thus, the laminate 13 may be produced. Specifically, after the thermoelectric conversion material layer pieces are placed alternately in the groove 32c of the structure retainer 32 in such a manner that each of them has a predetermined inclination angle, this is subjected to roll rolling while being heated and is then cooled. Thus, the laminate 13 can be produced.
In order to operate the thermoelectric element 10, a temperature gradient is generated from the inner circumference side to the outer circumference side in the laminate 13. This generates an electromotive force in the laminate 13. The electrical power that has been generated is output through the first electrode 11 and the second electrode 12.
The thermoelectric element 10 of the present invention can be placed while being in close contact with the outer circumference of a cylindrical or columnar heat source such as a muffler of an automobile or a pipe for discharging exhaust gas inside a factory to the outside. Thereby, since it can absorb heat efficiently from the heat source, it has a high thermoelectric conversion efficiency. Furthermore, since the laminate 13 has a shape that spirally extends around the axis 19, the portion (the inner circumference portion) that is brought into contact with the heat source can have a sufficiently wide area.
The thermoelectric element 10 of the present invention can have a high power generation performance by suitably selecting the ratio of the materials composing it, the angle θ, the inner circumferential angle, and the ratio of the inner and outer diameters. Therefore, a practical thermoelectric element 10 can be obtained. The present invention promotes application of energy conversion between heat and electricity and therefore has a high industrial value.
The materials for the extracting electrodes 71 and the interconnecting electrode 73 are not particularly limited, as long as materials with a high electrical conductivity are used. Specifically, a metal such as Cu, Ag, Mo, W, Al, Ti, Cr, Au, Pt, or In, a nitride such as TiN, or an oxide such as indium tin oxide (ITO) or SnO2 can be used. Furthermore, a solder, a silver brazing, or a conductive paste also may be used. The interconnecting electrode 73 and the extracting electrodes 71 can be produced by using various methods such as plating and thermal spraying in addition to vapor phase growth methods such as a vapor deposition method and a sputtering method.
As shown in
The materials for the wirings 84 and the extracting electrodes 81 are not particularly limited as long as materials with a high electrical conductivity are used. Specifically, a metal such as Cu, Ag, Mo, W, Al, Ti, Cr, Au, Pt, or In, a nitride or an oxide such as TiN, indium tin oxide (ITO), or SnO2 can be used. Furthermore, a solder, a silver brazing, or a conductive paste also may be used. The wirings 84 and the extracting electrodes 81 can be produced by using various methods such as plating and thermal spraying in addition to vapor phase growth methods such as a vapor deposition method and a sputtering method.
As shown in
Even when the heat source has a curved surface as in the case of a columnar shape, the thermoelectric devices of the present invention each can be in close contact with the heat source and thereby heat can be transferred efficiently. Accordingly, the thermoelectric devices can generate electrical power efficiently.
Hereinafter, further specific examples of the present invention are described.
A thermoelectric element 10 of Example 1 had the structure shown in
The thermoelectric element 10 was produced by the production method shown in
The thermoelectric conversion material layer pieces 31 were disposed in the groove 32c of the structure retainer 32 at regular intervals. After the thermoelectric conversion material layer pieces 31 were disposed, Bi heated to 650° C. was poured between them and was then air-cooled for 24 hours. After the structure retainer 32 was removed, the laminate 13 was subjected to the cutting-polishing processing.
A first electrode 11 and a second electrode 12 that were composed of Au were formed at the both ends of the laminate 13, respectively, by the sputtering method. Thus, the thermoelectric element 10 was obtained.
With respect to the thermoelectric element 10 produced by the above-mentioned method, the power generation performance thereof was evaluated. The inner circumference side of the laminate 13 was heated to 30° C. with warm water and the outer circumference side was water-cooled to 20° C. Then, the electromotive force and electrical resistance between the first electrode 11 and the second electrode 12 were measured. When the inclination angle, i.e. the angle θ, was 60°, the electromotive force was 10.5 mV and the resistance was 0.16 mΩ. From this result, the power factor was estimated to be 290 μW/cmK2. In the same manner, a plurality of thermoelectric elements 10 were produced, with the angle θ being varied, and the power factors thereof were determined. Table 1 indicates the result.
From Table 1, it was confirmed that the thermoelectric elements 10 of Example 1 exhibited preferable power generation properties when the angle θ was in the range of 15° to 210° and exhibited further preferable power generation properties when the angle θ was particularly in the range of 30° to 120°.
A thermoelectric element 10 of Example 2 was produced in the same manner as in Example 1. The angle θ was fixed at 60°. A plurality of thermoelectric elements 10 were produced, with the ratio of the inner circumferential angles of Cu and Bi of the laminate 13 being varied in the range of 0.025:1 to 400:1, and the power factors thereof were determined. Table 2 indicates the result. In order to vary the ratio of the inner circumferential angles, when the thermoelectric conversion material layer pieces 31 are disposed in the groove 32c of the structure retainer 32, the intervals at which they are disposed can be varied.
From Table 2, it was confirmed that the thermoelectric elements 10 of Example 2 exhibited preferable power generation properties when the ratio of the inner circumferential angles of Cu and Bi was in the range of 0.2:1 to 250:1 and exhibited further preferable power generation properties when the ratio was particularly in the range of 5:1 to 20:1.
A thermoelectric element 10 of Example 3 was produced in the same manner as in Example 1. The angle θ was fixed at 60°. A plurality of thermoelectric elements 10 were produced, in each of which the inner diameter of the laminate 13 was set at 100 mm, the outer diameter thereof was varied, and thereby the ratio of the inner and outer diameters was varied in the range of 1:1.05 to 1:150. The power factors thereof were then determined. Table 3 indicates the result.
From Table 3, it was confirmed that the thermoelectric elements 10 of Example 3 exhibited preferable power generation properties when the ratio of the inner and outer diameters was in the range of 1:1.1 to 1:100 and exhibited further preferable power generation properties when the ratio was particularly in the range of 1:1.5 to 1:2. In this case, the power factor exceeds 300 μW/cmK2. This is a performance at least about six times as high as that of the π-type structure device that contains Bi used therein and that currently is being used practically.
A thermoelectric element was produced in the same manner as in Example 1. In the thermoelectric element, the materials composing the respective thermoelectric conversion material layers were Cu and Bi, and the respective thermoelectric conversion material layers included both layers with an angle θ of 60° and layers with an angle θ of 180°. In the laminate, the ratio of the inner circumferential angles of Cu and Bi was set at 5:1 and the ratio of the inner and outer diameters was set at 1:1.5. The conditions other than these were the same as in Example 1. In Example 4, a plurality of thermoelectric elements were produced, with the volume ratio of the layers with an angle θ of 60° and the layers with an angle θ of 180° in the laminate being varied, and were then operated under the same conditions as those employed in Example 1. Table 4 indicates the measurement result of the power factor. Table 4 indicates only the volume ratios of the layers with an angle θ of 60°. The volume ratios of the layers with an angle θ of 180° each are the remainder thereof.
A thermoelectric device 70 of Example 5 had the configuration shown in
The laminates 13 were produced in the same manner as in Example 1. The angle θ was set at 60°, the inner circumferential angle of the first thermoelectric conversion material layers 14 was set at 18°, the ratio of the inner circumferential angles of Cu and Bi was set at 20:1, the inner diameter of each laminate 13 was set at 100 mm, and the ratio of the inner and outer diameters was set at 1:2. Furthermore, Cu plates with a thickness of 0.5 mm were used for the extracting electrodes 71 and the interconnecting electrode 73.
With respect to the thermoelectric device 70 of Example 5, the power generation performance thereof was evaluated. First, the resistance value between the extracting electrodes 71 was measured and was 0.34 mΩ. The inner circumference side of each laminate 13 was heated to 30° C. with warm water and the outer circumference side was maintained at 20° C. by water cooling. The open circuit electromotive force of the thermoelectric device 70 was 17.6 mV. According to this result, the power factor was estimated to be a high value, specifically, 386 μW/cmK2. A maximum electrical power of 7.8 W was extracted from the thermoelectric device 70 of Example 5.
A thermoelectric element 10 of Example 6 had the structure shown in
First, Cu was subjected to cutting machining, and thereby thermoelectric conversion material layer pieces 31 with the same shape as that of the first thermoelectric conversion material layers 14 were produced (see
The structure retainer 32 shown in
The thermoelectric conversion material layer pieces 31 and the thermoelectric conversion material layer pieces composed of Bi2Te3 were disposed alternately in the groove 32c of the structure retainer 32. While being heated to 580° C., the laminate including those thermoelectric conversion material layer pieces that were layered together was subjected to roll press from one end to the other end at 0.01 MPa. Thereafter, it was air-cooled for 24 hours and the structure retainer 32 was then removed. After that, the laminate 13 was subjected to the cutting-polishing processing.
A first electrode 11 and a second electrode 12 that were composed of Au were formed at the both ends of the laminate 13, respectively, by the sputtering method. Thus, the thermoelectric element 10 was obtained.
With respect to the thermoelectric element 10 produced by the above-mentioned method, the power generation performance thereof was evaluated. The inner circumference side of the laminate 13 was heated to 30° C. with warm water and the outer circumference side was water-cooled to 20° C. Then, the electromotive force and electrical resistance between the first electrode 11 and the second electrode 12 were measured. When the inclination angle, i.e. the angle θ, was 60°, the electromotive force was 8.4 mV and the resistance was 3.54 mΩ. From this result, the power factor was estimated to be 257 μW/cmK2. In the same manner, a plurality of thermoelectric elements 10 were produced, with the angle θ being varied, and the power factors thereof were determined. Table 5 indicates the result.
From Table 5, it was confirmed that the thermoelectric elements 10 of Example 6 exhibited preferable power generation properties when the angle θ was in the range of 15° to 210° and exhibited further preferable power generation properties when the angle θ was particularly in the range of 60° to 90°.
A thermoelectric element 10 of Example 7 was produced in the same manner as in Example 6. The angle θ was fixed at 60°. A plurality of thermoelectric elements 10 were produced, with the ratio of the inner circumferential angles of Cu and Bi2Te3 of the laminate 13 being varied in the range of 0.025:1 to 400:1, and the power factors thereof were determined. Table 6 indicates the result.
From Table 6, it was confirmed that the thermoelectric elements 10 of Example 7 exhibited preferable power generation properties when the ratio of the inner circumferential angles of Cu and Bi2Te3 was in the range of 0.05:1 to 250:1 and exhibited further preferable power generation properties when the ratio was particularly in the range of 5:1 to 40:1.
A thermoelectric element 10 of Example 8 was produced in the same manner as in Example 6. The angle θ was fixed at 60°. A plurality of thermoelectric elements 10 were produced, in each of which the inner diameter of the laminate 13 was set at 100 mm, the outer diameter thereof was varied, and thereby the ratio of the inner and outer diameters was varied in the range of 1:1.05 to 1:150. The power factors thereof were then determined. Table 7 indicates the result.
From Table 7, it was confirmed that the thermoelectric elements 10 of Example 8 exhibited preferable power generation properties when the ratio of the inner and outer diameters was in the range of 1:1.1 to 1:10 and exhibited further preferable power generation properties when the ratio was particularly 1:1.5. In this case, the power factor exceeds 300 μW/cmK2. This is a performance at least about six times as high as that of the π-type structure device that contains Bi used therein and that currently is being used practically.
A thermoelectric element was produced in the same manner as in Example 6. In the thermoelectric element, the materials composing the respective thermoelectric conversion material layers were Cu and Bi2Te3, and the respective thermoelectric conversion material layers included both layers with an angle θ of 60° and layers with an angle θ of 180°. In the laminate, the ratio of the inner circumferential angles of Cu and Bi2Te3 was set at 5:1 and the ratio of the inner and outer diameters was set at 1:1.5. The conditions other than these were the same as in Example 6. In Example 9, a plurality of thermoelectric elements were produced, with the volume ratio of the layers with an angle θ of 60° and the layers with an angle θ of 180° in the laminate being varied, and were then operated under the same conditions as those employed in Example 1. Table 8 indicates the measurement result of the power factor. Table 8 indicates only the volume ratios of the layers with an angle θ of 60°. The volume ratios of the layers with an angle θ of 180° each are the remainder thereof.
A thermoelectric device 70 of Example 10 had the configuration shown in
The laminates 13 were produced in the same manner as in Example 6. The angle θ was set at 60°, the inner circumferential angle of the first thermoelectric conversion material layers 14 was set at 18°, the ratio of the inner circumferential angles of Cu and Bi2Te3 was set at 20:1, the inner diameter of each laminate 13 was set at 100 mm, and the ratio of the inner and outer diameters was set at 1:1.5. Furthermore, Cu plates with a thickness of 0.5 mm were used for the extracting electrodes 71 and the interconnecting electrode 73.
With respect to the thermoelectric device 70 of Example 10, the power generation performance thereof was evaluated. First, the resistance value between the extracting electrodes 71 was measured and was 0.32 mΩ. The inner circumference side of each laminate 13 was heated to 30° C. with warm water and the outer circumference side was maintained at 20° C. by water cooling. The open circuit electromotive force of the thermoelectric device 70 was 41.4 mV. According to this result, the power factor was estimated to be a high value, specifically, 315 μW/cmK2. A maximum electrical power of 6.4 W was extracted from the thermoelectric device 70 of Example 10.
A thermoelectric element 10 of Example 11 had the structure shown in
First, Cu was subjected to cutting machining, and thereby thermoelectric conversion material layer pieces 31 with the same shape as that of the first thermoelectric conversion material layers 14 were produced (see
The structure retainer 32 shown in
The thermoelectric conversion material layer pieces 31 and the thermoelectric conversion material layer pieces composed of PbTe were disposed alternately in the groove 32c of the structure retainer 32. While being heated to 800° C., the laminate including those thermoelectric conversion material layer pieces that were layered together was subjected to roll press from one end to the other end at 0.01 MPa. Thereafter, it was air-cooled for 24 hours and the structure retainer 32 was then removed. After that, the laminate 13 was subjected to the cutting-polishing processing.
A first electrode 11 and a second electrode 12 that were composed of Au were formed at the both ends of the laminate 13, respectively, by the sputtering method. Thus, the thermoelectric element 10 was obtained.
With respect to the thermoelectric element 10 produced by the above-mentioned method, the power generation performance thereof was evaluated. The inner circumference side of the laminate 13 was heated to 30° C. with warm water and the outer circumference side was water-cooled to 20° C. Then, the electromotive force and electrical resistance between the first electrode 11 and the second electrode 12 were measured. When the inclination angle, i.e. the angle θ, was 60°, the electromotive force was 6.8 mV and the resistance was 3.8 mΩ. From this result, the power factor was estimated to be 136 μW/cmK2. In the same manner, a plurality of thermoelectric elements 10 were produced, with the angle θ being varied, and the power factors thereof were determined. Table 9 indicates the result.
From Table 9, it was confirmed that the thermoelectric elements 10 of Example 11 exhibited preferable power generation properties when the angle θ was in the range of 15° to 210° and exhibited further preferable power generation properties when the angle θ was particularly in the range of 60° to 90°.
A thermoelectric element 10 of Example 12 was produced in the same manner as in Example 11. The angle θ was fixed at 60°. A plurality of thermoelectric elements 10 were produced, with the ratio of the inner circumferential angles of Cu and PbTe of the laminate 13 being varied in the range of 0.025:1 to 400:1, and the power factors thereof were determined. Table 10 indicates the result.
From Table 10, it was confirmed that the thermoelectric elements 10 of Example 12 exhibited preferable power generation properties when the ratio of the inner circumferential angles of Cu and PbTe was in the range of 0.2:1 to 100:1 and exhibited further preferable power generation properties when the ratio was particularly in the range of 5:1 to 40:1.
A thermoelectric element 10 of Example 13 was produced in the same manner as in Example 11. The angle θ was fixed at 60°. A plurality of thermoelectric elements 10 were produced, in each of which the inner diameter of the laminate 13 was set at 100 mm, the outer diameter thereof was varied, and thereby the ratio of the inner and outer diameters was varied in the range of 1:1.01 to 1:50. The power factors thereof were then determined. Table 11 indicates the result.
From Table 11, it was confirmed that the thermoelectric elements 10 of Example 13 exhibited preferable power generation properties when the ratio of the inner and outer diameters was in the range of 1:1.05 to 1:10 and exhibited further preferable power generation properties when the ratio was particularly in the range of 1:1.2 to 1:1.5. In this case, the power factor exceeds 150 μW/cmK2. This is a high performance at least about three times as high as that of the π-type structure device that contains Bi used therein and that currently is being used practically.
A thermoelectric element was produced in the same manner as in Example 11. In the thermoelectric element, the materials composing the respective thermoelectric conversion material layers were Cu and PbTe, and the respective thermoelectric conversion material layers included both layers with an angle θ of 60° and layers with an angle θ of 180°. In the laminate, the ratio of the inner circumferential angles of Cu and PbTe was set at 5:1 and the ratio of the inner and outer diameters was set at 1:1.5. The conditions other than these were the same as in Example 11. In Example 14, a plurality of thermoelectric elements were produced, with the volume ratio of the layers with an angle θ of 60° and the layers with an angle θ of 180° in the laminate being varied, and were then operated under the same conditions as those employed in Example 11. Table 12 indicates the measurement result of the power factor. Table 12 indicates only the volume ratios of the layers with an angle θ of 60°. The volume ratios of the layers with an angle θ of 180° each are the remainder thereof.
A thermoelectric device 70 of Example 15 had the electrical configuration shown in
The laminates 13 were produced in the same manner as in Example 11. The angle θ was set at 60°, the inner circumferential angle of the first thermoelectric conversion material layers 14 was set at 18°, the ratio of the inner circumferential angles of Cu and PbTe was set at 20:1, the inner diameter of each laminate 13 was set at 100 mm, and the ratio of the inner and outer diameters was set at 1:1.5. Furthermore, Cu plates with a thickness of 0.5 mm were used for the extracting electrodes 71 and the interconnecting electrode 73.
With respect to the thermoelectric device 70 of Example 15, the power generation performance thereof was evaluated. First, the resistance value between the extracting electrodes 71 was measured and was 0.32 mΩ. The inner circumference side of each laminate 13 was heated to 30° C. with warm water and the outer circumference side was maintained at 20° C. by water cooling. The open circuit electromotive force of the thermoelectric device 70 was 61.5 mV. According to this result, the power factor was estimated to be a high value, specifically, 156 μW/cmK2. A maximum electrical power of 3.2 W was extracted from the thermoelectric device 70 of Example 15.
The thermoelectric elements and thermoelectric devices according to the present invention have excellent power generation properties and can be used for, for example, electric generators that utilize heat of, for example, an exhaust gas discharged from a factory or an automobile. Furthermore, they also can be used for, for example, small mobile electric generators.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-297548 | Nov 2008 | JP | national |
| 2008-297549 | Nov 2008 | JP | national |
| 2008-297550 | Nov 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/006153 | 11/17/2009 | WO | 00 | 7/28/2010 |
