JPH05315657A - Thermoelectric converting element and thermoelectric converter - Google Patents

Abstract

PURPOSE:To improve a synthetic thermoelectric conversion efficiency by joining p-type or n-type thermoelectric semiconductors to both sides of the material being a good heat conductor and being an electric insulator, in an element which converts heat to electricity or electricity to heat. CONSTITUTION:P-type thermoelectric semiconductors 21 and 22 or n-type thermoelectric semiconductors 31 and 32 are joined to both sides of the material being a good heat conductor and being an electric insulator through an electrodes 5. The power generated by the temperature difference between a thermal source 6 and a material 1 is taken out from the electrodes 5 provided to both ends of the p-type thermoelectric semiconductor 21 or an n-type thermoelectric semiconductor 31, and the power generated by the temperature difference between the material 1 and a heat source 7 is taken out of the electrodes 5 provided at both ends of the p-type thermoelectric semiconductor 22 or an n-type thermoelectric semiconductor 32, and are supplied to different loads, respectively. Since the thermoelectric semiconductors different in composition are junctioned thermally, the deterioration of the thermoelectric semiconductor by the heat can be prevented by the selection of the material 1, and high thermoelectric conversion efficiency can be maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly efficient thermoelectric conversion element and a thermoelectric conversion device using the same.

[0002]

2. Description of the Related Art Thermoelectric conversion elements use energy (ENERGY)
As described in September 1987, p. 47, etc., a rod-shaped or plate-shaped p-type thermoelectric conversion semiconductor and an n-type thermoelectric conversion semiconductor are joined at one end directly or through a conductor, and an electrode is provided at the other end. It is known that they are joined (FIGS. 13 and 14) and directly convert heat into electricity by the Seebeck effect and electricity into heat by the Peltier effect and Thomson effect.

[0003]

When the thermoelectric conversion element is used as an element for thermoelectric generation, generally, the larger the temperature difference between the high temperature end and the low temperature end, the larger the thermoelectromotive force. In the case of the conventional rod-shaped thermoelectric conversion element, it is long in the heat flow direction of the element in order to obtain the temperature difference between the high temperature end and the low temperature end. Since a thermoelectric conversion material generally has a larger electric resistance than a metal, when the thermoelectric conversion element is connected to a load, Joule heat generation due to the internal resistance of the thermoelectric conversion element increases, and the thermoelectric conversion efficiency decreases. Further, in the case of a thermoelectric conversion element using a plate-shaped thermoelectric conversion material, since the high temperature source and the low temperature source are very close to each other, it is difficult to suppress heat loss due to radiative heat transfer from the high temperature source to the low temperature source. , The total thermoelectric conversion efficiency defined by the ratio of the generated power to the input heat amount decreases.

When the thermoelectric conversion semiconductor element is used as an element for power generation, power can be generated even if the positions of the high temperature source and the low temperature source are exchanged, but the flowing current is in the opposite direction, so the battery is charged. It cannot be used in applications where the direction of equal current must be constant.

When the thermoelectric conversion semiconductor element is used as an element for cooling, when the rod-shaped material is used, the Joule heat generation due to the internal resistance of the element becomes large as described above, and when the plate-shaped material is used, The backflow of heat due to the heat radiation from the heat generating portion to the heat absorbing portion causes a problem that the heat generating portion is cooled and the heat absorbing portion is heated, and the cooling efficiency is reduced.

A first object of the present invention is to provide a thermoelectric conversion element having a high total thermoelectric conversion efficiency.

A second object of the present invention is to provide a thermoelectric conversion module device using a thermoelectric conversion semiconductor element having a high total thermoelectric conversion efficiency.

A third object of the present invention is to provide a thermoelectric conversion device in which a current flows through the load in the same direction even when the high temperature source and the low temperature source are switched.

[0009]

The first object of the present invention is to:
In an element that directly converts heat into electricity or electricity into heat, it can be achieved by bonding a p-type or n-type thermoelectric semiconductor to both ends of a material that is a good conductor of heat and an electrical insulator. ..

The first object of the present invention is also to provide an element for converting heat into electricity or directly converting electricity into heat, in which a p-type or n-type thermoelectric semiconductor is joined to both ends of a heat pipe. Can be achieved.

The first object of the present invention can also be achieved by constructing a thermoelectric conversion element by using a material having a high performance index at high temperature and a material having a high performance index at medium and low temperatures.

The second object of the present invention can be achieved by a configuration in which a plurality of thermoelectric conversion elements according to claims 3 to 6 are electrically connected in series or in parallel.

The third object of the present invention can also be achieved by inserting a rectifying device between the electrode portion of the thermoelectric conversion device and the load.

[0014]

In the thermoelectric conversion element of the present invention, first, the thermoelectric semiconductor is bonded to both ends of a material having a high thermal conductivity (for example, a heat pipe having a thermal conductivity several thousand times that of a metal). Without changing the size of the conversion semiconductor,
Moreover, the length of the element can be arbitrarily set while keeping the temperature difference in the portion that does not contribute to thermoelectric conversion very small. Therefore, even when the distance between the heat sources is large, the internal resistance of the thermoelectric element can be kept small. Also, in order to suppress heat radiation between heat sources and heat conduction through structural materials (reinforcing materials, etc.) that do not contribute to thermoelectric conversion, the distance between the heat sources installed between the heat sources is increased to increase the distance between the heat sources. Means such as reducing the temperature gradient can be used. Therefore, high total thermoelectric conversion efficiency can be obtained. Also, when a material with high thermal conductivity is an insulator electrically, especially when the distance between heat sources is large and it is necessary to lengthen the length of a good conductor of this heat in the heat flow direction, the high temperature source side By electrically disconnecting the thermoelectric semiconductor and the thermoelectric semiconductor on the low temperature source side and connecting them to different loads, it is possible to shorten the wiring and reduce power transmission loss.

In the case of the thermoelectric conversion element of the present invention, a thermoelectric semiconductor material having a high performance index at medium and high temperatures is used on the high temperature source side, and a thermoelectric semiconductor material having a high performance index at medium and low temperatures is used on the low temperature source side. As a result, high thermoelectric conversion efficiency can be realized. A tandem-type thermoelectric conversion element based on a similar idea joins thermoelectric conversion semiconductors with different compositions at an extremely short distance, so that some of the components of the thermoelectric conversion semiconductors used at high temperatures are heated to the low temperature side. It may diffuse and deteriorate in a short time. On the other hand, in the thermoelectric conversion element of the present invention, since thermoelectric semiconductors having different compositions are bonded only at a long distance thermally, a material that is a good conductor of heat and an electrical insulator is appropriately selected. As a result, it is possible to prevent the thermoelectric semiconductor from deteriorating due to heat and maintain a high thermoelectric conversion efficiency.

The thermoelectric conversion element and the thermoelectric conversion device of the present invention can be operated even when the high temperature source and the low temperature source are exchanged, but since the flowing current is in the opposite direction, a known rectifying device should be inserted between the load and the load. Thereby, the direction of the current flowing through the load can be kept constant.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.

<Embodiment 1> FIG. 1 is a sectional view showing a first embodiment of the present invention. A p-type thermoelectric semiconductor 21,2 such as iron silicide in which a small amount of chromium is added to both ends of a material (for example, silicon carbide) 1 which is a good electric conductor and an electric insulator.
2 or n such as iron silicide with a small amount of cobalt added
The thermoelectric semiconductors 31 and 32 are joined via the electrode 5. The electric power generated by the temperature difference between the heat source 6 and the material 1 which is a good conductor of heat and which is an electric insulator is generated by the p-type thermoelectric semiconductor 21,
Alternatively, the electric power generated by the temperature difference between the heat source 7 and the material 1 which is a good conductor of heat and an electric insulator is taken out from the electrodes 5 provided at both ends of the n-type thermoelectric semiconductor 31, or n-type thermoelectric semiconductor 22 or n. The thermoelectric semiconductor 32 is taken out from the electrodes 5 provided at both ends and connected to different loads 8.

FIG. 2 is a sectional view showing a second embodiment of the present invention. The difference from FIG. 1 is that instead of the material 1 which is a good conductor of heat and is an electric insulator, a heat pipe 11 is used in which the parts in contact with the thermoelectric semiconductor and the electrodes are electrically insulated by the electric insulator 12. There is a point.

In the present embodiment, since electric power can be independently taken out from the thermoelectric semiconductor which is in contact with the heat source 6 side and the thermoelectric semiconductor which is in contact with the heat source 7 side, the material 1 or thermoelectric semiconductor which is a good heat conductor and an electric insulator, Even when the length of the heat pipe 11 in which the portion in contact with the electrodes is electrically insulated by the electric insulator 12 is long, the wiring can be kept short and power transmission loss can be reduced. Further, it is possible to generate power with the same efficiency regardless of which of the heat source 6 and the heat source 7 becomes a high temperature source.

<Embodiment 2> FIG. 3 is a sectional view showing a third embodiment of the present invention. For the p-type thermoelectric semiconductors 21 and 22, iron silicide containing a small amount of chromium added, n-type thermoelectric semiconductors 31 and 3
2 uses iron silicide containing a small amount of cobalt. The p-type thermoelectric semiconductors 21 and 22 and the n-type thermoelectric semiconductors 31 and 32 are joined together with a material (for example, silicon carbide) 1 which is a good thermal conductor and an electrical insulator interposed therebetween. The p-type thermoelectric semiconductor 21 and the n-type thermoelectric semiconductor 31 are electrically connected to each other at their ends close to the heat source 6 by a well-known method (for example, silver paste) with the good electrical conductor 4, and the p-type thermoelectric semiconductors 21, n
The electrode 5 is formed on the other end of the thermoelectric semiconductor 31. Heat source 6
The electric power generated by the temperature difference between the material 1 which is a good conductor of heat and the electrical insulator is taken out from this electrode. The p-type thermoelectric semiconductor 22 and the n-type thermoelectric semiconductor 32 are electrically connected at their ends remote from the heat source 7 by a well-known method (for example, silver paste) by the good electrical conductor 4, and are connected to the p-type thermoelectric semiconductor 22. The electrode 5 is formed on the other end of the n-type thermoelectric semiconductor 32. Material 1 that is a good conductor of heat and an electrical insulator
The electric power generated by the temperature difference between the heat source 7 and the heat source 7 is taken out from this electrode.

FIG. 4 is a sectional view showing the first embodiment of the present invention. 3 is different from FIG. 3 in that instead of the material 1 which is a good conductor of heat and is an electric insulator, a heat pipe 11 in which a portion contacting a thermoelectric semiconductor and an electrode is electrically insulated by an electric insulator 12 is used. It is in.

<Embodiment 3> In FIGS. 3 and 4, the heat source 6 is a high temperature source and the heat source 7 is a low temperature source.
For the p-type thermoelectric semiconductor 22 and the n-type thermoelectric semiconductor 32, for example, a material having a high thermoelectric power at an intermediate temperature and a high temperature, for example, iron silicide containing chromium or cobalt is used for the type thermoelectric semiconductor 31, for example, By using bismuth telluride to which selenium or antimony is added, a higher overall thermoelectric conversion efficiency than in Example 1 is realized.

<Fourth Embodiment> FIG. 5 is a sectional view showing a fifth embodiment of the present invention. 3 is different from FIG. 3 in that instead of the good electrical conductor 4 that electrically connects the p-type thermoelectric semiconductor 22 and the n-type thermoelectric semiconductor 32, the p-type thermoelectric semiconductor 22 and the n-type thermoelectric semiconductor 32 are provided.
The electrode 5 is provided on each of the above, and the electrical good conductor 4 that connects the p-type thermoelectric semiconductors 21 and 22 and the n-type thermoelectric semiconductors 31 and 32 is provided in parallel with the material 1 which is a good thermal conductor and an electrical insulator. Further, in order to suppress radiant heat transfer, a barrier 9 is provided between the heat source 6 and the heat source 7 with a material having a low emissivity (such as a film formed by vapor deposition of gold). Material 1 that is a good conductor of heat and an electrical insulator
The good electrical conductor 4 provided in parallel with the above may be integrated with the material 1 which is a good thermal conductor and an electrical insulator.

FIG. 6 is a sectional view showing a sixth embodiment of the present invention. The difference from FIG. 5 is that the heat pipe 11 is used instead of the material 1 which is a good conductor of heat and is an electric insulator. As a result, the same effect as that of integrating a good thermal conductor and a good electrical conductor can be obtained.

A comparison between this example and the conventional example is shown below. In addition, in the p-type thermoelectric semiconductors 21 and 22, and the n-type thermoelectric semiconductors 31 and 32, the figure of merit Z = 10 ³ K ⁻¹ (Seebeck coefficient α
= 10 ⁻³ VK, electric conductivity σ = 10 ³ Ω ⁻¹ m ⁻¹ , thermal conductivity κ = ¹ Wm ⁻¹ K ⁻¹ ) and a thermal conductivity κ _hp = 10 ⁵ Wm ^−1. Using the K- ¹ heat pipe 11,
Heat flow direction total length 10 cm (of which thermoelectric conversion material length 1 cm x
2) It is assumed that a thermoelectric conversion element having a cross-sectional area of 10 cm ² of the thermoelectric conversion material part is manufactured. The high temperature source temperature is 773K, the low temperature source temperature is 373K, the heat source cross-sectional area is 20 cm ² , and the resistance value R
The total thermoelectric conversion efficiency when connected to a load of 0.02Ω was compared.

(1) Comparison with a rod-shaped thermoelectric conversion element The total thermoelectric conversion efficiency is 5.5% when a thermoelectric conversion element of the same size as the element of this preparation example, which is made of all thermoelectric conversion materials, is manufactured. This is about half of the total thermoelectric conversion efficiency of 10% in this preparation example.

(2) Comparison with a plate-like thermoelectric conversion element A thermoelectric conversion element composed entirely of thermoelectric conversion material and having a length of 2 cm in the heat flow direction (from the thermoelectric element of this preparation example to the heat pipe 1
1 and the radiant heat barrier 9 are removed), the total thermoelectric conversion efficiency is 4.5% when radiant heat transfer is taken into consideration, which is about the total thermoelectric conversion efficiency of this example that can suppress radiant heat transfer. It is half.

<Fifth Embodiment> FIGS. 7 and 8 are sectional views showing the seventh and eighth embodiments of the present invention. The present example is a good conductor of heat and an electrical insulator which existed independently in the thermoelectric conversion element having the p-type electrical property and the thermoelectric conversion element having the n-type electrical property in the first example. Some material 1,
Alternatively, the heat pipe 11 in which the portion contacting the thermoelectric semiconductor and the electrodes is electrically insulated by the electric insulator 12
I shared it. With such a configuration, it is possible to reduce the number of parts, save material, and simplify assembly without losing the advantages described in the first embodiment. In the present embodiment, for one element, the material 1 which is a good conductor of heat and is an electrical insulator, or the heat pipe 11 in which the portion contacting the thermoelectric semiconductor and the electrode is electrically insulated by the electrical insulator 12 is shared. Although an example is shown, when a thermoelectric conversion device is configured by combining a large number of elements, the material 1 which is a good conductor of heat and is an electrical insulator of all the elements, or the thermoelectric semiconductor and the electrode, regardless of electrical connection. It is also possible to share the heat pipe 11 whose portion contacting with is electrically insulated by the electric insulator 12.

<Embodiment 6> FIGS. 9 and 10 are perspective views showing the ninth and tenth embodiments of the present invention. The configuration is Example 2
In the present embodiment, the heat source 6 and the heat source 7 are flat plates and are perpendicular to each other, and the material 1 which is a good conductor of heat and is an electrical insulator, or the portion which contacts the thermoelectric semiconductor and the electrode is electrically The heat pipe 11 electrically insulated by the insulator 12 is bent by 90 degrees in accordance with the heat pipe 11.
Not only in the simple case as in this embodiment, but also in the heat pipe in which the material 1 which is a good conductor of heat and is an electric insulator, or the portion which contacts the thermoelectric semiconductor and the electrode is electrically insulated by the electric insulator 12. By selecting a material with high workability as 11, there is no need to change the shape of the thermoelectric conversion element, which is often difficult to process, to create the element according to the arrangement state of the heat source and the usage state of the space between the heat sources. You can

<Embodiment 7> FIGS. 11 and 12 are sectional views showing an embodiment of the thermoelectric conversion device of the present invention. 11 and 1
2 is a material 1 which is a good conductor of heat and an electrical insulator, which is obtained by electrically connecting two thermoelectric conversion elements shown in FIGS. 3 and 4 and thermoelectric conversion materials on the heat source 6 side and the heat source 7 side respectively in series. , Or the portion in contact with the thermoelectric semiconductor and the electrode is the electrical insulator 1
The heat pipe 11 electrically insulated by 2 is shared. The extracted electric power is connected to different loads 8 on the heat source 6 side and the heat source 7 side, and a known rectifying device 10 is inserted between the thermoelectric converter and the load so that either the heat source 6 or the heat source 7 becomes a high temperature source. Even so, the current is made to flow in the same direction in the load 8. In this embodiment, only two elements are connected, but it is possible to electrically connect a larger number of elements by various methods.

Although the above embodiments have been described mainly from the viewpoint of thermoelectric power generation, except for the seventh embodiment, by removing the heat sources 6 and 7 and passing an electric current through the electrodes, high-performance thermoelectric cooling and heating can be performed. It can be operated as an element or a device.

[0033]

According to the present invention, a thermoelectric conversion element having a high total thermoelectric conversion efficiency can be obtained. Further, a thermoelectric conversion device using a thermoelectric conversion element having a high total thermoelectric conversion efficiency can be obtained. Then, even when the high temperature source and the low temperature source are exchanged, it is possible to obtain a thermoelectric conversion device in which a current flows through the load in the same direction.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a sixth embodiment of the present invention.

FIG. 7 is a perspective view of a seventh embodiment of the present invention.

FIG. 8 is a perspective view of an eighth embodiment of the present invention.

FIG. 9 is a sectional view of a ninth embodiment of the present invention.

FIG. 10 is a sectional view of a tenth embodiment of the present invention.

FIG. 11 is a system diagram of an embodiment of the thermoelectric conversion device of the present invention.

FIG. 12 is a system diagram of another embodiment of the thermoelectric conversion device of the present invention.

FIG. 13 is a sectional view of a thermoelectric conversion element using a conventional rod-shaped thermoelectric conversion material.

FIG. 14 is a cross-sectional view of a thermoelectric conversion element using a conventional plate-shaped thermoelectric conversion material.

[Explanation of symbols]

4 ... Good electrical conductor, 5 ... Electrode, 6 ... Heat source, 7 ... Heat source, 8 ...
Load, 21 ... P-type thermoelectric conversion material, 22 ... P-type thermoelectric conversion material, 31 ... N-type thermoelectric conversion material, 32 ... N-type thermoelectric conversion material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Shiono 1168 Moriyama-cho, Hitachi-shi, Ibaraki Pref.

Claims (10)

[Claims] 1. An element for converting heat into electricity or directly converting electricity into heat, wherein a p-type or n-type thermoelectric semiconductor is bonded to both ends of a material which is a good conductor of heat and is an electric insulator. Thermoelectric conversion element. 2. A thermoelectric conversion element for converting heat into electricity or directly converting electricity into heat, wherein a p-type or n-type thermoelectric semiconductor is bonded to both ends of a heat pipe. 3. The thermoelectric semiconductor according to claim 1, wherein the both ends of the material which is a good conductor of heat and is an electric insulator are the same,
The two semiconductors are electrically connected by a conductor to form a thermoelectric conversion element having p-type or n-type electrical properties, and one ends of the thermoelectric conversion elements having different electrical properties are connected by a good electrical conductor. Conversion element. 4. The p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor according to claim 1, which have thermoelectric semiconductors having the same electric properties at both ends of a material which is a good conductor of heat and is an electric insulator. One with a thermoelectric semiconductor with different electrical properties at each end of a material that is a good conductor of heat and an electrical insulator, and two of each semiconductor with different electrical properties. A thermoelectric conversion element with one end connected by a good electrical conductor. 5. A thermoelectric conversion element having p-type or n-type electrical properties, wherein the thermoelectric semiconductors at both ends of the heat pipe, which is a good conductor of heat and is a good conductor of heat, have the same type. A thermoelectric conversion element in which one ends of thermoelectric conversion elements having different electrical properties are connected by a good electrical conductor. 6. The heat pipe according to claim 2, wherein at least a portion in contact with the thermoelectric semiconductor and the electrode is electrically insulated by a known method, the thermopipe semiconductor having the same electric property at both ends. One using p-type thermoelectric semiconductor and one using n-type thermoelectric semiconductor,
Alternatively, a thermoelectric conversion element in which two thermoelectric semiconductors having different electric properties at both ends of the heat pipe are connected to each other at one end of each semiconductor having different electric properties by a good electric conductor. 7. The thermoelectric conversion element according to claim 1, wherein the high temperature source side is made of a material having a high performance index at a high temperature, and the low temperature source side is made of a material having a high performance index at an intermediate temperature. 8. A thermoelectric conversion element according to claim 3, 4 or 6, wherein a material that is a good conductor of heat and is an electrical insulator or a heat pipe is shared. 9. The thermoelectric conversion module according to claim 3, 4, 5 or 6, wherein a plurality of thermoelectric conversion elements are electrically connected in series or in parallel. 10. The thermoelectric conversion device according to claim 9, wherein a rectifying device is inserted between the electrode of the thermoelectric conversion element or the thermoelectric conversion device and the load.