WO2019021703A1

WO2019021703A1 - Thermoelectric power generation module for calibration

Info

Publication number: WO2019021703A1
Application number: PCT/JP2018/023516
Authority: WO
Inventors: 山本　淳; 和夫長瀬; 誠相原; 道広太田; 弘隆西当; 高澤　弘幸
Original assignee: 国立研究開発法人産業技術総合研究所
Priority date: 2017-07-27
Filing date: 2018-06-20
Publication date: 2019-01-31
Also published as: JP2021078351A; JPWO2019021703A1; JP7441524B2; JP6858379B2

Abstract

Provided are a thermoelectric conversion element and a thermoelectric power generation module including same, which are utilizable as a thermoelectric power generation module for calibration of an evaluation device for thermoelectric power generation modules. The thermoelectric power generation module for calibration of an evaluation device for thermoelectric power generation modules according to the present invention is characterized by comprising a plurality of thermoelectric conversion elements (40) disposed in parallel between an upper electrode (4b) and a lower electrode (4a), and by providing at least one through-hole (5, 6, 7) in respective lateral surfaces of the plurality of thermoelectric conversion elements so that heat flow between the upper electrode and the lower electrode is suppressed at the time of power generation.

Description

Thermoelectric module for calibration

The present invention relates to a thermoelectric power generation module, and more particularly to a thermoelectric power generation module for calibration of an evaluation device of a thermoelectric power generation module, and more specifically to a thermoelectric conversion element constituting a thermoelectric power generation module for calibration.

The thermoelectric conversion technology is a technology for mutually converting thermal energy and electrical energy using a solid thermoelectric conversion element. The technology for converting thermal energy into electrical energy is called thermoelectric generation and is based on the Seebeck effect, which is one of the thermoelectric effects. In thermoelectric generation, a temperature difference between both ends of a thermoelectric conversion element is directly converted to electrical energy. By using this thermoelectric power generation to recover the vast amount of unused thermal energy emitted from factories and automobiles, and generating electricity from there, it is possible to greatly reduce fossil fuel consumption, CO ₂ reduction and energy saving. I can contribute.

The thermoelectric conversion element generally has a configuration in which a thermoelectric conversion material is sandwiched between two electrodes. A thermoelectric power generation module can be configured using the thermoelectric conversion element. Specifically, for example, a P-type thermoelectric conversion element (carriers carrying charges are holes), an N-type thermoelectric conversion element (carriers carrying charges are electrons), and thermal using an upper junction electrode and a lower junction electrode The thermoelectric generation module is obtained by electrically connecting in series in parallel. The thermoelectric generation module functions as a thermoelectric generation module even with a pair of P-type-N-type thermoelectric conversion elements, but usually, in order to obtain a larger output, multiple pairs of P-type-N-type thermoelectric conversion elements are connected to form a thermoelectric generation module Further, a plurality of the thermoelectric generation modules are combined to constitute a thermoelectric generation device.

In order to standardize the performance standard of the thermoelectric power generation module that constitutes the thermoelectric power generation device, it is necessary for the development, manufacture and the like of the thermoelectric power generation module to more appropriately and accurately evaluate the characteristics of the thermoelectric power generation module. For that purpose, it is indispensable to calibrate the evaluation device that performs the characteristic evaluation of the thermoelectric generation module. The calibration of the evaluation device is generally performed using a standard (standard) calibration thermoelectric generation module. In the calibration of the evaluation device, it is necessary to add a temperature of about 500 ° C. to the high temperature side of the thermoelectric generation module for calibration, but there are the following problems when using the conventional thermoelectric generation module.

As a problem of the thermoelectric power generation module itself, it can be mentioned that a thermoelectric conversion element that can be used for a thermoelectric power generation module for calibration that withstands the high temperature side temperature of 500 ° C. is not readily available. For example, the thermoelectric conversion element of a BiTe-based sintered body currently commercially available is about 230 ° C. at maximum use temperature. In addition, although the thermoelectric conversion element of Mg ₂ Si-based sintered body can be used at 500 ° C., there is a problem of durability of the thermoelectric conversion element itself, and it can not be used for calibration. Furthermore, although the thermoelectric conversion element of a SiGe-based sintered body can be used at 500 ° C., the difference between the thermal expansion coefficient and the thermal expansion coefficient of metal electrodes such as Cu, Au, Ni, etc. is large. There is concern about peeling of the joint between the metal electrodes and breakage of the element itself, and there is a problem of durability as a thermoelectric power generation module, so it can not be used for calibration.

As a problem of the evaluation device side of the thermoelectric power generation module, when using a metal-based or metal alloy-based thermoelectric conversion element that can be used at a high temperature 500 ° C., heat flow (heat flux) flowing in the element becomes large and evaluation The heat flow beyond what is usually considered may be input to the device, and the heat flow may not be accurately measured. Specifically, a large heat flow exceeds the capacity of the cooling device of the evaluation device of the thermoelectric power generation module, and it becomes difficult to keep the low temperature and the temperature difference between the high temperature and the low temperature constant.

Patent document 1 makes the shape of the thermoelectric element a shape whose area is not uniform in the cross-sectional direction perpendicular to the heat flux, for example, a truncated cone, a truncated pyramid, a shape combining a plurality of these, or a shape combining spheres. Thus, a thermoelectric power generation element is disclosed, which is capable of increasing the temperature difference between the high temperature side and the low temperature side in the thermoelectric element, in which a hot spot is formed in the thermoelectric element.

Japanese Patent Application Laid-Open No. 2006-253341

The thermoelectric conversion element of Patent Document 1 has a truncated cone or truncated pyramid shape, and the cross-sectional area of one of the surfaces in contact with the upper and lower electrodes is reduced. The shape and bonding condition are different from those of the thermoelectric conversion elements in which the cross-sectional areas of the surfaces in contact with the upper and lower electrodes having the shape of a regular rectangular parallelepiped or a column to be evaluated by the evaluation device are the same. Therefore, as the heat flow is reduced, the bonding surface with the metal electrode becomes smaller, and there is a possibility that sufficient bonding strength can not be obtained. That is, it is not suitable as a thermoelectric conversion element which comprises the thermoelectric-generation module for calibration of the evaluation apparatus of a thermoelectric-generation module. In addition, a thermoelectric conversion element in which two small circles of two truncated cone-shaped thermoelectric elements are combined by electric heating or the like also has a small bonding surface, and thus there is a possibility that sufficient strength can not be maintained.

In the present invention, heat flow (heat flux) is suppressed even at high temperatures on the high temperature side of 500 ° C. or higher, and the cross-sectional area of the surface in contact with the upper and lower electrodes is similar to that of a normal thermoelectric conversion element. It is an object of the present invention to provide a thermoelectric conversion element that can be secured and used as a thermoelectric power generation module for calibration of an evaluation device of a thermoelectric power generation module, and a thermoelectric power generation module including the same.

A thermoelectric generation module for calibration of an evaluation device of a thermoelectric generation module according to an aspect of the present invention includes a plurality of thermoelectric conversion elements arranged in parallel between an upper electrode and a lower electrode, and a side surface of each of the plurality of thermoelectric conversion elements Preferably, at least one or more through holes are provided to suppress an increase in heat flow between the upper electrode and the lower electrode during power generation.

According to the thermoelectric generation module for calibration of one aspect of the present invention, the heat flow (heat flux) between the upper electrode and the lower electrode is suppressed at the time of power generation by the through holes provided on the side surfaces of the thermoelectric conversion elements. Power generation efficiency can be improved as compared with the case of using a thermoelectric conversion element without through holes.

It is a figure which shows the structure of the conventional thermoelectric conversion element. It is a figure which shows the structure (a pair of PN thermal-electric conversion element) of the conventional thermoelectric-generation module. It is a figure which shows the structure of the thermoelectric conversion element of one Embodiment of this invention. It is a figure which shows the external appearance of the conventional thermoelectric-generation module. It is a figure which shows the external appearance of the thermoelectric-generation module of one Example of this invention. It is a figure which shows the characteristic of the thermoelectric-generation module of one Example of this invention. It is a figure which shows the characteristic of the thermoelectric-generation module of one Example of this invention.

Embodiments of the present invention will be described with reference to the drawings. In the following description, for comparison and in order to understand the configuration common to the present invention, the description will be made with reference to the drawings regarding the conventional thermoelectric conversion element and the thermoelectric generation module as appropriate.

FIG. 1 is a diagram showing the configuration of a conventional thermoelectric conversion element. The thermoelectric conversion element 10 has a configuration in which the thermoelectric conversion material 1 is sandwiched between two

electrode materials

2a and 2b. The

electrode materials

2a and 2b electrically and thermally connect the thermoelectric conversion material 1 and a junction electrode to be described later, and transmit current and heat well while suppressing the reaction between the thermoelectric conversion material 1 and the junction electrode And the role of relieving stress between the thermoelectric conversion material 1 and the junction electrode.

FIG. 2 is a diagram showing the configuration (a pair of PN thermoelectric conversion elements) of a conventional thermoelectric generation module. The thermoelectric generation module 100 includes two thermoelectric conversion elements, a thermoelectric conversion element 20 and a thermoelectric conversion element 30, and one upper junction electrode 13 disposed to bridge these two thermoelectric conversion elements, and a thermoelectric conversion element 20 and lower junction electrodes 14 and 14 'disposed under the thermoelectric conversion element 30, respectively. As shown in FIG. 2, the thermoelectric power generation module 100 has a π-shape as a whole.

The upper bonding electrode 13 and the lower bonding electrodes 14 and 14 'correspond to the above-described bonding electrodes. A material having good electrical and thermal conductivity is used for the upper junction electrode 13 and the lower junction electrode 14 and 14 '. For example, Cu, Au, Ni, etc. are used. The thickness is about 1 mm at the upper limit in consideration of productivity. Further, the thermoelectric conversion element 20 has a configuration in which the thermoelectric conversion material 11 is sandwiched between two

electrodes

12 a and 12 b as in the case of the thermoelectric conversion element 10 in FIG. 1, and the thermoelectric conversion element 30 also has two thermoelectric conversion materials 11 ′. It is set as the structure clamped by electrode 12a ', 12b'.

In the thermoelectric generation module 100, when the thermoelectric conversion element 20 is a P-type thermoelectric conversion element (the carrier carrying the charge is a hole), the pair of thermoelectric conversion elements 30 is an N-type thermoelectric conversion element (the carrier carrying the charge is electrons) It is. When the upper junction electrode 13 is heated to a high temperature and the lower junction electrodes 14 and 14 'are cooled to a low temperature, it can be used as a thermoelectric power generation module that generates a potential difference between the lower junction electrodes 14-14'. Among the configurations of the conventional thermoelectric conversion element 10 and the thermoelectric power generation module 100 described above, other configurations except for the configuration (form) of the

thermoelectric conversion materials

1, 11 and 11 'are ones of the present invention described below. It is basically the same as the thermoelectric generation module of the embodiment.

FIG. 3 is a view showing a configuration (appearance) of a thermoelectric conversion element according to an embodiment of the present invention. (A) to (c) of FIG. 3 show an example of three

thermoelectric conversion elements

40, 41, 42 having the shape of a vertically long rectangular parallelepiped. The thermoelectric conversion element 40 of (a) has a configuration in which the thermoelectric conversion material 3 is sandwiched between two

electrode materials

4a and 4b. In each of the four side surfaces of the thermoelectric conversion material 3, in other words, each of two adjacent side surfaces, two through holes 5 having a circular cross section are provided.

The thermoelectric conversion element 41 of FIG. 3B similarly has a configuration in which the thermoelectric conversion material 3 is sandwiched between two

electrode materials

4a and 4b. In each of the four side surfaces of the thermoelectric conversion material 3, in other words, each of two adjacent side surfaces, two through holes 6 having a rectangular cross section are provided. The thermoelectric conversion element 42 of (c) similarly has a configuration in which the thermoelectric conversion material 3 is sandwiched between two

electrode materials

4a and 4b. One through hole 7 having a circular cross section is provided on each of two adjacent side surfaces of the thermoelectric conversion material 3. Although not shown in the drawings, in the case of having a vertically long cylindrical shape instead of the above long rectangular shape, it is possible to provide another through hole as shown in (a) to (c). It is included in the present invention as an embodiment.

In the thermoelectric conversion elements 40 to 41 of each embodiment of FIG. 3, the number of through holes 3 to 5 and the opening size are thermoelectric generation materials at the time of power generation, that is, when the upper and

lower electrode materials

4a and 4b have a predetermined temperature difference. The effective range can be determined to suppress the heat flow flowing through three. If the number of through holes and the opening size increase, the substantial heat transfer path of the thermoelectric conversion material 3 narrows through the through holes and the thermal resistance increases. Therefore, the heat flow flowing through the thermoelectric conversion material 3 is further suppressed. Can. However, at the time of power generation, since the thermoelectric conversion material 3 becomes a current path due to the potential difference generated simultaneously, if the number of through holes and the opening size are made too large, the power generation amount (power generation efficiency) will be lowered. . Therefore, it is necessary to determine the number of through holes and the opening size in consideration of the balance between the heat flow (its suppression) and the power generation amount (its maintenance).

Since the thermoelectric conversion elements 41 to 42 according to the embodiment of the present invention are used as a part of the thermoelectric generation module for calibration, the temperature of the upper electrode 4b which is high is 500 ° C. or higher. Even materials that can withstand are selected. In addition, since a through hole is provided on the side surface, it is also required to be an easy material that can be processed. Furthermore, in order to prevent bonding peeling and the like at the time of heating, it is desirable that the material has a thermal expansion coefficient close to that of metals (for example, Cu, Au, Ni, etc.) which can be the upper and

lower electrode materials

4a, 4b. As a material of the thermoelectric conversion material 3 which satisfy | fills these conditions, the NiCr alloy used as a P-type thermoelectric conversion element, the CuNi alloy used as an N-type thermoelectric conversion element etc. are mentioned, for example. In addition, the material of the thermoelectric conversion material 3 is not limited to this example, As long as it is a material which can satisfy said 3 conditions, other arbitrary materials can be selected.

An embodiment of the present invention will be described with reference to FIGS. 4 to 7. FIG. 4 is a view showing the appearance of a conventional thermoelectric generation module for comparison. FIG. 5 is an external view of a thermoelectric generation module according to an embodiment of the present invention. 6 and 7 are diagrams showing the characteristics of the thermoelectric generation modules of FIGS. 4 and 5, respectively. In the conventional thermoelectric generation module 50 of FIG. 4 (a), 16 thermoelectric conversion elements 10 in the shape of (b) are arranged in parallel between the upper substrate 51 at high temperature and the lower substrate 52 at low temperature. It is done. Among the 16 thermoelectric conversion elements 10, there are eight P-type and eight N-type, and they are alternately arranged in parallel one by one. The thermoelectric conversion element 10 of (b) is the same as that of the structure by which the thermoelectric conversion material 1 of FIG. 1 was clamped by two

electrode material

2a, 2b.

In the thermoelectric generation module 60 according to the embodiment of the present invention shown in FIG. 5, 16 thermoelectric conversion elements 40 in the shape of (b) are arranged in parallel between the upper substrate 61 which is high temperature and the lower substrate 62 which is low temperature. Is located in Among the 16 thermoelectric conversion elements 40, there are eight P-type and eight N-type, and they are alternately arranged in parallel one by one. The thermoelectric conversion element 40 of (b) is the same as the structure by which the thermoelectric conversion material 3 which has the through-hole 5 of Fig.3 (a) was clamped by two

electrode material

4a, 4b. The

thermoelectric conversion elements

10 and 40 of FIG. 4 and FIG. 5 are basically the same except for the configuration (the presence or absence of the through hole) of the thermoelectric conversion elements.

Table 1 below shows basic specifications of the thermoelectric conversion element 40 according to the embodiment of the present invention shown in FIG. 5 (b). Assuming that the last two rows in the table have the names of the holeless P-type element and the holeless N-type element in FIG. 4B, the conventional thermoelectric conversion element 10 in FIG. , Materials, etc.). As a high temperature side and a low temperature side substrate in the table, a substrate made of silicon nitride with 0.2 mm thick copper adhered on the surface was used. The number behind the element name of Sn63Pb37 on the low temperature side bonding material in the table means atomic%, and mp 183 ° C. indicates that the melting point is 183 ° C. Similarly, the numbers after the element names of Ni90Cr10 and Cu55Ni45 in the table mean atomic%. Moreover, the unit of the size in a table | surface is a millimeter (mm), and (PHI) 2 shows that the diameter of a through-hole is 2 mm.

FIG. 6 gives temperature loads on the high temperature side 500 ° C. and the low temperature side 50 ° C. in each of the thermoelectric power generation modules in FIGS. 4 and 5 and measures the heat flow passing between the upper and lower electrodes for deriving the power generation efficiency at that time The results are shown. The graph of A is the heat flow Q (W) of the thermoelectric generation module 60 of one embodiment of the present invention in FIG. 5, and the graph of B is the heat flow Q (W) of the conventional thermoelectric generation module 50 of FIG. The inventive heat flow Q of A was about 74 W and the heat flow density was about 9.4 W / cm ² . On the other hand, the heat flow of the conventional structure of B was about 234 W, and the heat flow density was about 29.8 W / cm ² . From the comparison of the two, in the thermoelectric power generation module 60 according to the embodiment of the present invention shown in FIG. 5, the passing heat flow can be reduced (suppressed) by about 69% as compared with the conventional structure shown in FIG.

FIG. 7 shows the thermoelectric-to-electricity conversion efficiency% (%) obtained under the measurement conditions of FIG. The graph of A is the conversion efficiency η (%) of the thermoelectric power generation module 60 of the embodiment of the present invention of FIG. 5, and the graph of B is η (%) of the conventional thermoelectric power generation module 50 of FIG. The conversion efficiency η of the present invention of A was about 0.52%, and the conversion efficiency η of the conventional structure of B was about 0.30%. From the comparison of the two, the thermoelectric generation module 60 according to the embodiment of the present invention shown in FIG. 5 was able to increase (improve) the conversion efficiency η by about 70% as compared with the conventional structure shown in FIG.

The improvement of the conversion efficiency η in FIG. 7 is considered to largely depend on the heat flow Q reduction effect of FIG. That is, the conversion efficiency η can be expressed by the following equation (1) using the power generation output P and the passing heat flow Q _out of the thermoelectric conversion element.

η = P / (Q _out + P) × 100 (%) (1)

From the equation (1), it can be seen that it is effective to reduce the passing heat flow Q _out in order to increase the conversion efficiency η.

Embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the present invention can be implemented in variously modified, modified, or modified forms based on the knowledge of those skilled in the art without departing from the scope of the present invention. For example, instead of the through holes in the side surfaces of the thermoelectric conversion element, an opening having a depth not halfway through the thermoelectric conversion material may be provided to obtain the same heat flow reduction effect. At that time, it is possible to adjust the flow rate of heat released depending on the depth of the opening and the like.

The thermoelectric conversion element of the present invention and the thermoelectric power generation module using the same can be industrially used as a thermoelectric power generation module for calibration of an evaluation device of a thermoelectric power generation module.

1, 3, 11, 11 '

thermoelectric conversion material

2a, 2b, 4a,

4b electrode material

5, 6, 7 through

hole

10, 40, 41, 42 thermoelectric conversion element 20 P type thermoelectric conversion element 30 N type

thermoelectric conversion element

12a , 12b, 12a ', 12b' electrode 13 upper bonding electrode 14, 14 '

lower bonding electrode

51, 61

upper substrate

52, 62 lower substrate

Claims

A thermoelectric generation module for calibration of an evaluation device of a thermoelectric generation module,
Including a plurality of thermoelectric conversion elements arranged in parallel between the upper electrode and the lower electrode;
A calibration thermoelectric generation module, wherein at least one through hole is provided on each side surface of the plurality of thermoelectric conversion elements so as to suppress heat flow between the upper electrode and the lower electrode during power generation.
The calibration thermoelectric generation module according to claim 1, wherein at least one or more of the through holes are provided in each of two adjacent side surfaces of the thermoelectric conversion element.
The calibration thermoelectric generation module according to claim 1, wherein two or more through holes are provided on one side surface of the thermoelectric conversion element.
The calibration thermoelectric generation module according to any one of claims 1 to 3, wherein each of the thermoelectric conversion elements has a rectangular or cylindrical shape.
The calibration thermoelectric generation module according to claim 4, wherein a cross section of the through hole has a circular or rectangular shape.
The calibration thermoelectric generation module according to claim 5, wherein the plurality of thermoelectric conversion elements include P-type thermoelectric conversion elements and N-type thermoelectric conversion elements alternately arranged in the lateral direction.
The calibration thermoelectric generation module according to claim 6, further comprising a metal bonding layer between the upper surface and the lower surface of each of the thermoelectric conversion elements, and the upper electrode and the lower electrode.