JP2002026406A - Thermoelectric conversion module comprising electric insulating structure and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric conversion module comprising a heat- resistant electric insulating structure which is suitable for large-scale thermoelectric power generation whose heat source is exhaust heat and where scale-up is easy, and heat resistance is suppressed with high reliability. SOLUTION: A theremoelectric conversion module 10 comprises electrically/ thermally insulating frame 11 where a plurality of through holes 12 and a plurality of electrode grooves 13 communicating between the through holes 12 are provided, a p-type thermoelectric element 14 and an n-type thermoelectric element 15 arrayed alternately at the through hole 12 of the frame 11, a thermal- sprayed electrode 17 so embedded that the p-type thermoelectric element 14 and the n-type thermoelectric element 15 are alternately electrically connected, in series, on the electrode groove 13 of the frame 11, and a ceramic insulating thermal-sprayed layer 20 formed on the thermal-sprayed electrode 17. The frame 11, the p-type and n-type thermoelectric elements 14 and 15, the thermal-sprayed electrode 17, and the ceramic insulating thermal-sprayed layer 20 are integrally fitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric conversion module for directly converting heat into electricity and a method for manufacturing the same, and more particularly to a thermoelectric module using large-scale exhaust heat as a heat source, such as a power plant or a waste incineration facility. It is useful in power generators.

[0002]

2. Description of the Related Art In a thermoelectric conversion module, a plurality of p-type thermoelectric elements and n-type thermoelectric elements are usually arranged alternately, and these thermoelectric elements are made of a conductive material such as metal. And electrically connected in series. This thermoelectric conversion module generates a thermoelectromotive force by the Seebeck effect by giving a temperature difference to the thermoelectric element, and converts a part of heat to electric power by connecting an electric load to the electrode terminals of the thermoelectric conversion module. Can be taken out. A power generator using this thermoelectric conversion module has features such as a simple structure, no moving parts that generate vibration, noise, wear, etc., and the scale of the heat source is not limited. It is attracting attention as a means of recovering heat as electric power and using it effectively.

In general, in the use of such a thermoelectric conversion module, in most cases, one surface is connected to a high-temperature heat exchanger made of a good heat conductor, and the other surface is connected to a low-temperature heat exchanger also made of a good heat conductor. Contact each exchanger,
Electric power is generated by giving a temperature difference to the thermoelectric element. Since the heat exchanger is generally made of metal, when the thermoelectric conversion module is brought into contact with the heat exchanger as it is, an electrical short circuit occurs between the electrodes and power cannot be taken out. Therefore, it is necessary to provide some kind of electric insulating layer between the metal electrode surface and the heat exchanger. In most cases, an inexpensive and highly heat-conductive alumina plate is used for the electric insulating layer. However, in order to reduce the thermal resistance, the alumina plate needs to be thin, but is easily broken because it is a ceramic. Also, it is difficult to increase the area because it is easily broken. Furthermore, it is difficult to secure a sufficient contact area simply by pressing the electrode surface against the alumina plate, so usually applying thermally conductive grease to the alumina surface ensures a secure contact state. I have. However, the thermally conductive grease layer alone causes an increase in thermal resistance.

[0004] As a method for solving the above-mentioned problem,
Description of the Related Art [0005] Soldering of an electrode surface to an electrical insulating plate such as alumina ceramic having good thermal conductivity is performed.
However, this method is effective for low-temperature use, such as when a thermoelectric conversion module is used for thermoelectric cooling. However, when used for power generation in which the high-temperature side exceeds 200 ° C., the heat resistance of the solder is reduced. , The thermoelectric conversion module deteriorates. It is conceivable to solve the problem by using a high-temperature brazing material, but the melting point, decomposition temperature,
Or, there is a problem that the performance is deteriorated due to the diffusion of the brazing material into the element, and it is difficult to put it into practical use. There are only a few very special examples developed specifically for very special uses such as space applications. For details on such technologies, see, for example, "Thermoelectric Semiconductors and Their Applications" (Isao Nishida and Kinichi Uemura, published by Nikkan Kogyo Shimbun) and "Thermoelectric Conversion System Technology" (edited by Takenobu Kajikawa et al., Published by Realize). Has been described.

On the other hand, when a large-scale exhaust heat is used as a heat source, the use of a conventional small-sized thermoelectric module complicates the structure of the entire system, which is problematic in terms of design and construction and maintenance. Therefore, a large thermoelectric conversion module is desired. However, as described above, when a large thermoelectric conversion module is insulated with a substance having good insulation properties, as a material corresponding to an increase in area,
There are few materials suitable for this, for example, the use of heat-resistant polymers such as polyimide is conceivable.However, because the operating temperature range is limited and the thermal conductivity of the material itself is low, it is thinner than an alumina plate to reduce thermal resistance. Must be performed, which also causes a problem in mechanical strength. A method of laying a combination of small-area alumina plates is also conceivable, but this method is difficult to make the thickness uniform and it is difficult to secure sufficient contact, so a grease layer is indispensable structurally. Yes, thermal resistance cannot be reduced. As described above, especially in a large thermoelectric conversion module, an insulating method with high reliability and low thermal resistance has not yet been established.

Accordingly, an object of the present invention is to provide a thermoelectric conversion module which solves such a conventional problem, that is, a thermoelectric conversion module suitable for thermoelectric power generation using large-scale exhaust heat as a heat source.
It is an object of the present invention to provide a thermoelectric conversion module having an electrical insulation structure that suppresses thermal resistance and has high reliability and high heat durability, and a method for manufacturing the same.

[0007]

SUMMARY OF THE INVENTION The present invention provides the above object,
This has been achieved by providing the following thermoelectric conversion module and a method for manufacturing the same. An electrically and thermally insulating mold provided with a plurality of through holes and a plurality of electrode grooves communicating between the through holes, and p-type thermoelectric elements alternately arranged in the through holes of the mold And an n-type thermoelectric element; a spray electrode embedded in the electrode groove of the mold so that the p-type thermoelectric element and the n-type thermoelectric element are alternately electrically connected in series; and A thermoelectric element comprising a ceramic insulating spray layer formed thereon, wherein the mold, the p-type and n-type thermoelectric elements, the spray electrode, and the ceramic insulating spray layer are integrally fixed. "Conversion module.""Using an electrically and thermally insulating material, an electrically and thermally insulating formwork provided with a plurality of through holes and a plurality of electrode grooves communicating between the through holes is produced. A p-type thermoelectric element and an n-type thermoelectric element in the through hole of the mold. And a step of alternately arranging the elements, using a conductive material, a step of forming sprayed electrodes on both surfaces of the mold in which the thermoelectric elements are arranged, and formed in other than the electrode grooves of the mold. A method for manufacturing a thermoelectric conversion module, comprising: a step of removing an unnecessary thermal spray electrode, a step of forming a ceramic insulating thermal spray layer on the thermal spray electrode, and a step of smoothing the surface of the ceramic thermal spray layer. "

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a thermoelectric conversion module according to the present invention will be described with reference to the embodiment shown in FIG. As shown in FIG. 1, the thermoelectric conversion module 10 of the present embodiment
An electrically and thermally insulating frame 11 provided with a plurality of through holes 12 and a plurality of electrode grooves 13, and p-type thermoelectric elements 14 and n-type elements alternately arranged in the through holes 12 of the mold frame 11. Thermoelectric element 15, thermal spray electrode 17 buried in electrode groove 13 of form 11; metal underlayer formed between thermal spray electrode 17 and p-type and n-type thermoelectric elements 14 and 15 16 and a ceramic insulation sprayed layer 20 formed on the sprayed electrode 17. The p-type thermoelectric elements 14 and the n-type thermoelectric elements 15 are electrically connected alternately in series via the sprayed electrodes 17. The p-type and n-type thermoelectric elements 14 and 15, the metal base layer 16, the spray electrode 17, and the ceramic insulating spray layer 20 are integrally fixed to the mold 11.

As the electrically and thermally insulating mold 11, a mold made of a molded product of calcium silicate can be used. Calcium silicate has crystalline phases called zonotolite and tobermorite, and those formed by mixing an organic binder with them are called artificial wood. This artificial wood has characteristics such as non-combustibility, low thermal conductivity, light weight, and good workability, and thus is suitable as an insulating mold for a thermoelectric conversion module. For example, the thermal conductivity is 1.2 W / mK for general lead glass, whereas the molded product of calcium silicate is 0.08 W / mK, which is as small as about 1/15. Compared to 0.4 W / mK of polyimide which is a heat-resistant resin, it is as small as about 1/5. Further, in terms of specific gravity, lead glass and polyimide have a specific gravity of 3.0 and 1.4, respectively.
It is as small as about 5 and is desirable as an insulating mold material for a thermoelectric conversion module.

The thermoelectric materials used as the p-type thermoelectric element 14 and the n-type thermoelectric element 15 are known Bi ₂ Te ₃ , BiSb, FeSi ₂ , PbTe.
It is possible to use a single crystal or a sintered body of a thermoelectric semiconductor such as a SiGe-based thermoelectric semiconductor, but when using a mold made of the above-described calcium silicate molded body as the insulating mold 11, The Bi ₂ Te ₃ system is preferable from the temperature range where the mold can be used.

The sprayed electrode 17 can be formed by a general method such as plasma spraying, gas spraying, arc spraying, and high-speed flame spraying. However, in order to obtain a dense and uniform electrode, plasma spraying and plasma spraying are performed. It is desirable to form by a gas spraying method. Further, as the material of the sprayed electrode 17, a metal having high conductivity such as aluminum or copper is suitable, but is not limited thereto. Further, the thermal spray electrode 17 is provided with a thermal spray layer of another conductive substance (the metal base layer 16) at the interface between the thermoelectric element and the electrode, in order to improve the peel strength between the thermoelectric element and the contact electric resistance. It can also be interposed.

Further, the ceramic insulating spray layer 20
Is preferably formed by a plasma spraying method in order to obtain a dense and uniform insulating layer. Suitable ceramics for forming the insulating sprayed layer 20 include those having relatively high thermal conductivity, such as alumina, but are not limited thereto, and include zirconia, thermally stabilized zirconia, alumina and titania. Composite materials consisting of, for example, can also be used.

The thermoelectric conversion module of the present invention can be applied to a thermoelectric power generation system utilizing exhaust heat of a power plant, waste heat of a garbage incineration facility, exhaust heat of an automobile, sunlight, and the like.

Next, a method of manufacturing a thermoelectric conversion module according to the present invention will be described with reference to FIG. 2 taking the case of manufacturing the thermoelectric conversion module of the embodiment shown in FIG. 1 as an example. First, as shown in FIG. 2A, an electrical and thermal insulating material is used to form an electrically and thermally insulating material in which a plurality of through holes 12 and a plurality of electrode grooves 13 communicating between the through holes 12 are provided. In addition, a thermally insulating mold 11 is manufactured. When calcium silicate is used as the insulating material, first, a molded body of calcium silicate is produced by a production method described in, for example, JP-A-62-213053 or JP-A-3-3635, and is obtained. It is preferable to fabricate the insulating mold 11 by machining the molded body.

Next, as shown in FIG. 2B, a p-type thermoelectric element 14 and an n-type
The thermoelectric elements 15 are alternately arranged using element spacers 18 and 19.

Next, the element spacers 18 and 19 are removed, and as shown in FIG. 2C, the metal underlayer 16 is subjected to the above-mentioned p-type thermoelectric element 14 and the above-mentioned n-type
After being formed on both sides of the mold thermoelectric element 15, the sprayed electrodes 17 are formed using a conductive material such as aluminum or copper so as to cover both sides of the insulating mold 11.

Next, as shown in FIG. 2D, unnecessary thermal spray electrodes formed on the insulating mold 11 other than the electrode grooves 13 are ground and removed using a surface grinder or the like. When the unnecessary thermal spray electrode is removed by grinding, the surface of the insulating mold 11 is slightly ground to ensure the flatness of the electrode surface.

Next, as shown in FIG. 2E, a ceramic insulation sprayed layer 20 is formed on the sprayed electrode by plasma spraying using ceramics such as alumina. Thereafter, in order to ensure the flatness of the ceramic insulating spray layer 20, the surface of the insulating spray layer 20 is subjected to surface grinding to obtain the thermoelectric conversion module of the embodiment shown in FIG.

[0019]

In the thermoelectric conversion module according to the first aspect of the present invention, a ceramic insulating layer is formed on a sprayed electrode by thermal spraying, and the electrode and the insulating layer are integrally fixed. High mechanical strength without
In addition, since a brazing material such as solder is not used for joining the electrodes and a sprayed electrode is used, apply a temperature difference up to the upper limit of the heat resistance of the thermoelectric element without being affected by the heat resistance of the brazing material. Is possible, and the power generation performance is improved. Also,
Since the ceramic insulating layer is formed directly on the sprayed electrode by thermal spraying, the use of a thermally conductive grease layer can be reduced. First, the overall thermal resistance is reduced, resulting in an increase in heat inflow and electrical insulation. The temperature difference is effectively distributed to the thermoelectric element itself due to the reduced thermal resistance of the layer and the electric insulating layer and the thermoelectric module electrode surface, and as a result, the power generation output is improved. Further, according to the method for manufacturing a thermoelectric conversion module of the present invention according to claim 2, it is easy to increase the size of the thermoelectric conversion module, which is suitable for thermoelectric power generation using large-scale exhaust heat as a heat source, with a relatively simple process. And a thermoelectric conversion module having an electrically insulating structure having high reliability and high heat durability can be manufactured.

[0020]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 In this example, in order to see the effect of the ceramic insulating sprayed layer formed on the sprayed electrode in the thermoelectric conversion module of the present invention, a sample was prepared as follows, and the sample was sprayed. The observation of the layer cross-sectional structure and the heat cycle test were performed. [Preparation of sample] Aluminum plate (50 mm x 50 mm x 5 mm
Thickness), aluminum was plasma sprayed to form a 2.4 mm thick aluminum sprayed layer. This is cut by 2
The surface was machined to a thickness of mm. Then, on this aluminum sprayed layer (2 mm thick), alumina ceramics was plasma sprayed to form a 0.4 mm thick alumina ceramics insulating sprayed layer. This was flattened to a thickness of 0.25 mm by grinding to obtain a sample. [Observation of Cross Section Structure of Thermal Sprayed Layer] The sample was embedded in a resin, the cut surface was polished to # 1000 with water resistant abrasive paper, buffed and finished, and the cross section structure was observed by SEM. As shown in FIG. 3, the structure was dense and the number of voids was small. [Heat Cycle Test] A sample was set in an alumina crucible, and a heat cycle as shown in FIG. 4 was repeated three times in the atmosphere. Then, the cross-sectional structure and the surface were observed by SEM. As a result, no peeling of the alumina ceramics sprayed layer from the aluminum sprayed layer and no cracks in the alumina ceramics sprayed layer were observed. From the results of the [observation of the cross-sectional structure of the thermal spray layer] and the [heat cycle test], it was confirmed that the ceramic insulating thermal spray layer formed by thermal spraying was sufficiently applicable to a thermoelectric conversion module.

Embodiment 2 This embodiment is directed to a heat source of about 300 ° C.
Bi as material_TwoTe _ThreeSystem as an insulating mold
Forming a formwork made of a molded body of lucium to form a sprayed electrode
Aluminum as conductive material and ceramic insulation
Alumina ceramics as the material for forming the coating layer
Example of thermoelectric conversion module of the present invention when used and used
It is. First, a molded product of calcium silicate [Ube Industries
2 (registered trademark; Woody Serum)
Machining the insulating mold 11 shown in FIG.
-). Calcium silicate moldings are not
Features such as fuel, low thermal conductivity, light weight, and good workability
The thermoelectric conversion module as an insulating formwork
It is suitable. Production of the molded body of calcium silicate shown here
For example, Japanese Patent Application Laid-Open No. Sho 62-123053 and
This is described in detail in JP-A-3-3635.

Next, a Bi ₂ Te ₃ -based thermoelectric element was manufactured as follows. First, the atomic ratio of Bi _0.3 Sb _1.7 Te
Each raw material was weighed so as to be ₃ (p-type) and Bi ₂ Te _2.4 Se _0.6 (n-type). To the n-type, 0.1% by weight of SbI ₃ was added to adjust the carrier density. Next, these materials were vacuum-sealed in a glass tube and melt-stirred at 650 ° C. for 1 hour to produce a Bi ₂ Te ₃ thermoelectric material. These thermoelectric materials were subjected to stamp mill and ball mill to obtain an average particle size of 1
After pulverizing to about 0 μm, a reduction treatment was performed at 390 ° C. for 12 hours. The obtained thermoelectric material powder was sintered at 490 ° C. for 15 minutes using a hot press to obtain a sintered body of the thermoelectric material. A columnar thermoelectric element (12φ × 7 mmh) was prepared from the obtained sintered body by using a slicer, an ultrasonic machine or the like.

Next, the p-type thermoelectric element 14 and the n-type thermoelectric element 1
5 after sandblasting to roughen the surface.
As shown in (b), they were alternately arranged on an insulating mold.

Next, as shown in FIG. 2 (c), the molybdenum underlayer 16 is formed by plasma spraying to improve the adhesion strength between the thermoelectric element and the aluminum sprayed electrode by 100 μm.
m, and then an aluminum electrode 17 is formed thereon.
mm. The formation of the backside molybdenum underlayer and the aluminum sprayed electrode was performed in the same manner.

Next, as shown in FIG. 2D, aluminum sprayed electrodes 17 formed on both surfaces of the insulating mold 11 are formed.
Unnecessary portions were ground using a surface grinder. At this time, the insulating mold was slightly cut to secure the flatness of the electrode surface.

Next, as shown in FIG. 2 (e), alumina ceramic is sprayed on the aluminum spray electrode 17 to form a 0.4 mm thick alumina ceramic insulating spray layer 20.
Was formed. Thereafter, in order to secure the planarity of the alumina ceramics thermal spray layer 20, the surface thereof is 0.2
mm ground, final alumina ceramics sprayed layer 2
The thickness of 0 was 0.2 mm.

The thermoelectric conversion module fabricated as described above (15 pairs of elements, module size 80 × 144 × 1)
0 mm) was sandwiched between an electric heater and a water-cooled plate via thermal conductive grease, and a temperature difference of 250 ° C. was applied to evaluate the power generation characteristics. An electronic load was used for the measurement, and the load resistance was measured at 0.15Ω. When the temperature difference between the heating plate and the water cooling plate was 250 ° C., the open circuit voltage was 1.205 V, and the temperature difference between the high temperature side and the low temperature side of the module determined from this value was 219.1 ° C. The maximum output is 10.8
6W. In addition, a continuous test was performed for two weeks under the above-mentioned conditions, but no reduction in power generation performance was observed, and it was confirmed that the reliability was excellent.

Comparative Example 1 As an insulating layer, a polyimide film (0.04 mmt)
Except that the thermal conductive grease was applied to both sides of
A thermoelectric conversion module was manufactured through the same steps as in Example 2. With respect to the thermoelectric conversion module having no alumina ceramics thermal spray layer, the same power generation characteristics as in Example 2 were evaluated. As a result, the open circuit voltage is 1.120 V
The temperature difference between the high temperature side and the low temperature side of the module determined from this value was 203.6 ° C. The maximum output was 9.57W.

As is clear from the evaluation results of the power generation characteristics of the thermoelectric conversion modules of Example 2 and Comparative Example 1, when the alumina ceramics thermal sprayed layer was used as the insulating layer,
The maximum output increased by 13.5% as compared with the case where the polyimide film was used. This is because the thermal conductivity of alumina is 20 W / mK and the polyimide film has a thermal conductivity of 0.2 W / mK.
4 W / mK, 1/50 of alumina, very small. Also, by forming the alumina sprayed film directly on the aluminum sprayed electrode, the thermal conductive grease layer could be reduced, so that even if the same temperature difference was applied between the heating plate and the cooling plate, the overall thermal resistance was reduced. As a result, the heat inflow increases, and the thermal resistance of the electrical insulating layer and the electrical insulating layer and the surface of the thermoelectric module electrode is reduced.
The temperature difference is effectively distributed. As a result, the power generation output is improved.

[0031]

The thermoelectric conversion module of the present invention is suitable for thermoelectric power generation using large-scale exhaust heat as a heat source, is easy to increase in size, suppresses thermal resistance, and has high reliability and high heat durability. It is a thermoelectric conversion module having an electric insulation structure. Further, according to the method for manufacturing a thermoelectric conversion module of the present invention,
The above-described thermoelectric conversion module of the present invention can be manufactured by relatively simple steps.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a thermoelectric conversion module of the present invention.

2 (a), 2 (b), 2 (c), 2 (d) and 2 (e) are process diagrams showing an example of a method for manufacturing a thermoelectric conversion module according to the present invention.

FIG. 3 is an observation view of a cross-sectional structure of a sprayed layer by SEM in Example 1.

FIG. 4 is a graph showing a temperature pattern of a heat cycle test in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermoelectric conversion module 11 Insulating mold 12 Through-hole 13 Electrode groove 14 P-type thermoelectric element 15 n-type thermoelectric element 16 Underlayer 17 Thermal spray electrode 20 Ceramic insulating thermal spray layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasumasa Ozora 5 in 1978 Kogushi, Oji, Ube City, Yamaguchi Prefecture Inside Ube Research Institute, Ltd. (72) Inventor Kazuhiro Fujii 5 Ube, 1978 Kogushi in Obe City, Ube City, Yamaguchi Prefecture Kobe Industries, Ltd.Ube Research Institute (72) Inventor Toru Inoue 2-182 Watanabe-dori, Chuo-ku, Fukuoka City, Fukuoka Prefecture Kyushu Electric Power Company (72) Inventor Hiroki Kamakura 2-1-1 Watanabe-dori, Chuo-ku, Fukuoka City, Fukuoka Prefecture No. 82 Kyushu Electric Power Co., Inc. (72) Inventor Toshio Sakurada 2-82 Watanabe-dori, Chuo-ku, Fukuoka City, Fukuoka Prefecture Kyushu Electric Power Co., Ltd.

Claims (2)

[Claims] 1. An electrically and thermally insulating mold provided with a plurality of through holes and a plurality of electrode grooves communicating between the through holes, and alternately arranged in the through holes of the mold. a p-type thermoelectric element and an n-type thermoelectric element, and a sprayed electrode embedded in the electrode groove of the mold so that the p-type thermoelectric element and the n-type thermoelectric element are alternately electrically connected in series. Comprises a ceramic insulating spray layer formed on the spray electrode,
The mold, the p-type and n-type thermoelectric elements, the spray electrode,
And a thermoelectric conversion module, wherein the ceramic insulation sprayed layer is integrally fixed. 2. An electrically and thermally insulating formwork having a plurality of through-holes and a plurality of electrode grooves communicating between the through-holes is produced using an electrically and thermally insulating material. A step of alternately arranging a p-type thermoelectric element and an n-type thermoelectric element in the through-hole of the mold; and using a conductive material, spraying electrodes on both surfaces of the mold in which the thermoelectric element is arranged. Forming a, a step of removing unnecessary sprayed electrodes formed other than the electrode grooves of the mold, a step of forming a ceramic insulating sprayed layer on the sprayed electrode, and a step of forming the ceramic insulating sprayed layer A method for producing a thermoelectric conversion module, the method comprising: smoothing a surface.