JP6858379B2 - Calibration thermoelectric power generation module - Google Patents

Description

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

The thermoelectric conversion technology is a technology for mutually converting thermal energy and electric energy using a solid thermoelectric conversion element. The technology for converting thermal energy into electrical energy is called thermoelectric power generation and is based on the Seebeck effect, which is one of the thermoelectric effects. In thermoelectric power generation, the temperature difference between both ends of the thermoelectric conversion element is directly converted into electrical energy. By using this thermoelectric power generation to recover the enormous amount of unused thermal energy emitted from factories and automobiles and generate electricity from it, fossil fuel consumption can be reduced, _{and CO 2 can be} reduced and energy can be saved. 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 by using the thermoelectric conversion element. Specifically, for example, a P-type thermoelectric conversion element (a carrier carrying an electric charge is a hole) and an N-type thermoelectric conversion element (a carrier carrying an electric charge is an electron) are thermally driven by using an upper junction electrode and a lower junction electrode. A thermoelectric power generation module is obtained by connecting in parallel and electrically in series. A thermoelectric generation module functions as a thermoelectric power generation module even with a pair of P-type-N type thermoelectric conversion elements, but usually, in order to obtain a larger output, a plurality of pairs of P-type-N type thermoelectric conversion elements are connected to form a thermoelectric power generation module. Further, a plurality of these thermoelectric power generation modules are combined to form a thermoelectric power generation device.

In order to promote the standardization of the performance standards of the thermoelectric power generation modules that make up the thermoelectric power generation equipment, it is necessary for the developers and manufacturers of the thermoelectric power generation modules to evaluate the characteristics of the thermoelectric power generation modules more appropriately and accurately. For that purpose, it is indispensable to calibrate the evaluation device that evaluates the characteristics of the thermoelectric power generation module. Calibration of the evaluation device is generally performed using a thermoelectric power generation module for calibration which is a standard (standard). 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 power generation module for calibration, but when the conventional thermoelectric power generation module is used, there are the following problems.

As a problem of the thermoelectric power generation module itself, there is a problem that a thermoelectric conversion element that can be used for a thermoelectric power generation module for calibration that can withstand a high temperature side temperature of 500 ° C. is not easily available. For example, a thermoelectric conversion element of a BiTe-based sintered body currently on the market has a maximum operating temperature of about 230 ° C. Further, although a _{thermoelectric conversion element of an Mg 2} Si sintered body can be used at 500 ° C., it cannot be used for calibration due to the problem of durability of the thermoelectric conversion element itself. Further, a thermoelectric conversion element of a SiGe-based sintered body can be used at 500 ° C., but the coefficient of thermal expansion thereof is significantly different from the coefficient of thermal expansion of metal electrodes such as Cu, Au, and Ni, and the thermoelectric conversion element. There is a concern that the joint between the metal electrode and the metal electrode may come off or the element itself may be damaged, and there is a problem with durability as a thermoelectric power generation module, so it cannot be used for calibration.

As a problem on the evaluation device side of the thermoelectric power generation module, when a metal-based or metal alloy-based thermoelectric conversion element that can be used at a high temperature side temperature of 500 ° C. is used, the heat flow (heat flux) flowing in the element becomes large and evaluated. There is a risk that the heat flow will be input to the device more than normally thought, and the heat flow cannot be measured accurately. 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 temperature on the low temperature side and the temperature difference between the high temperature side and the low temperature side constant.

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

Japanese Patent Application Laid-Open No. 2006-253341

The thermoelectric conversion element of Patent Document 1 has the shape of a truncated cone or a truncated cone, and the cross-sectional area of one of the surfaces in contact with the upper and lower electrodes becomes smaller. The shape and bonding conditions are different from those of a normal rectangular parallelepiped or a thermoelectric conversion element having a cylindrical shape and having the same cross-sectional area of the surfaces in contact with the upper and lower electrodes to be evaluated by the evaluation device. Therefore, the more the heat flow is reduced, the smaller the joint surface with the metal electrode becomes, and there is a possibility that sufficient joint strength cannot be obtained. That is, it is not suitable as a thermoelectric conversion element constituting the thermoelectric power generation module for calibration of the evaluation device of the thermoelectric power generation module. Further, a thermoelectric conversion element in which two small circles of two truncated cone-shaped thermoelectric elements are coupled to each other by energization overheating or the like also has a similarly small joint surface, so that there is a possibility that sufficient strength cannot be maintained.

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

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

According to the calibration thermoelectric power generation module of one aspect of the present invention, the through hole provided on the side surface of the thermoelectric conversion element suppresses the heat flow (heat flux) between the upper electrode and the lower electrode during power generation, and also The power generation efficiency can be improved as compared with the case of using a thermoelectric conversion element having no through hole.

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 thermoelectric conversion elements) of the conventional thermoelectric power 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 appearance of the conventional thermoelectric power generation module. It is a figure which shows the appearance of the thermoelectric power generation module of one Example of this invention. It is a figure which shows the characteristic of the thermoelectric power generation module of one Example of this invention. It is a figure which shows the characteristic of the thermoelectric power generation module of one Example of this invention.

An embodiment 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 relating to the conventional thermoelectric conversion element and the thermoelectric power generation module as appropriate.

FIG. 1 is a diagram showing a 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 the bonding electrode described later to transfer current and heat well, while suppressing the reaction between the thermoelectric conversion material 1 and the bonding electrode. It also has a role of relaxing the stress between the thermoelectric conversion material 1 and the junction electrode.

FIG. 2 is a diagram showing a configuration (a pair of PN thermoelectric conversion elements) of a conventional thermoelectric power generation module. The thermoelectric power generation module 100 includes two thermoelectric conversion elements, a thermoelectric conversion element 20 and a thermoelectric conversion element 30, an upper junction electrode 13 arranged so as to bridge these two thermoelectric conversion elements on the upper part, and a thermoelectric conversion element. 20 and lower bonding electrodes 14 and 14'arranged below the thermoelectric conversion element 30, respectively, are included. As shown in FIG. 2, the thermoelectric power generation module 100 has a π-shaped shape as a whole.

The upper bonding electrode 13 and the lower bonding electrodes 14 and 14'correspond to the above-mentioned bonding electrode. A material having good electrical and thermal conductivity is used for the upper bonding electrode 13 and the lower bonding electrodes 14 and 14'. For example, Cu, Au, Ni and the like 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 12a and 12b, similarly to the thermoelectric conversion element 10 of FIG. 1, and the thermoelectric conversion element 30 also has two thermoelectric conversion materials 11'. It is configured to be sandwiched between electrodes 12a'and 12b'.

In the thermoelectric power generation module 100, when the thermoelectric conversion element 20 is a P-type thermoelectric conversion element (the carrier carrying the electric charge is a hole), the paired thermoelectric conversion element 30 is an N-type thermoelectric conversion element (the carrier carrying the electric charge is an electron). Is. When the upper junction electrode 13 side is heated to a high temperature and the lower junction electrodes 14 and 14'sides are cooled to a low temperature, it can be used as a thermoelectric power generation module that causes a potential difference between the lower junction electrodes 14-14'. Of the above-mentioned configurations of the conventional thermoelectric conversion element 10 and the thermoelectric power generation module 100, other configurations except for the configurations (forms) of the thermoelectric conversion materials 1, 11 and 11'are one of the present inventions described below. It is basically the same as the thermoelectric power generation module of the embodiment.

FIG. 3 is a diagram showing a configuration (appearance) of a thermoelectric conversion element according to an embodiment of the present invention. FIGS. 3A to 3C show examples of three thermoelectric conversion elements 40, 41, and 42 having a vertically long rectangular parallelepiped shape. 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. Each of the four side surfaces of the thermoelectric conversion material 3, in other words, each of the two adjacent side surfaces, is provided with two through holes 5 having a circular cross section so as to be orthogonal to each other inside.

Similarly, the thermoelectric conversion element 41 of FIG. 3B has a structure in which the thermoelectric conversion material 3 is sandwiched between the two electrode materials 4a and 4b. Each of the four side surfaces of the thermoelectric conversion material 3, in other words, each of the two adjacent side surfaces, is provided with two through holes 6 having a rectangular cross section so as to be orthogonal to each other inside. Similarly, the thermoelectric conversion element 42 of (c) has a configuration in which the thermoelectric conversion material 3 is sandwiched between the 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, even if the shape of a vertically long cylinder is used instead of the shape of the vertically long rectangular parallelepiped described above, it is possible to provide a 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 determined during power generation, that is, when a predetermined temperature difference is applied to the upper and lower electrode materials 4a and 4b. It can be determined within an effective range for suppressing the heat flow flowing through 3. If the number of through holes and the opening size are increased, the substantial heat transfer path of the thermoelectric conversion material 3 is narrowed through the through holes and the thermal resistance is increased, so that the heat flow flowing through the thermoelectric conversion material 3 is further suppressed. Can be done. However, since the thermoelectric conversion material 3 becomes a current path due to the potential difference generated at the same time during power generation, if the number of through holes and the opening size are made too large, the amount of power generation (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 (suppression thereof) and the amount of power generation (maintenance thereof).

As the material of the thermoelectric conversion material 3, since the thermoelectric conversion elements 41 to 42 of the embodiment of the present invention are used as a part of the thermoelectric power generation module for calibration, the temperature of the upper electrode 4b, which becomes high temperature, is 500 ° C. or higher. But a material that can withstand is selected. Further, it is also required that the material is easy to process because the through hole is provided on the side surface. Further, in order to prevent joint peeling during heating, it is desirable that the material has a coefficient of thermal expansion close to that of a metal (for example, Cu, Au, Ni, etc.) that can be the upper and lower electrode materials 4a and 4b. Examples of the material of the thermoelectric conversion material 3 satisfying these conditions include a NiCr alloy serving as a P-type thermoelectric conversion element and a CuNi alloy serving as an N-type thermoelectric conversion element. The material of the thermoelectric conversion material 3 is not limited to this example, and any other material can be selected as long as it can satisfy the above three conditions.

Examples of the present invention will be described with reference to FIGS. 4 to 7. FIG. 4 is a diagram showing the appearance of a conventional thermoelectric power generation module for comparison. FIG. 5 is a diagram showing the appearance of a thermoelectric power generation module according to an embodiment of the present invention. 6 and 7 are diagrams showing the characteristics of the thermoelectric power generation modules of FIGS. 4 and 5. In the conventional thermoelectric power generation module 50 of FIG. 4A, 16 thermoelectric conversion elements 10 having the shape of (b) are arranged in parallel between the upper substrate 51 having a high temperature and the lower substrate 52 having a low temperature. Has been done. Of the 16 thermoelectric conversion elements 10, eight are P-type and eight are N-type, and one is alternately arranged in parallel. The thermoelectric conversion element 10 of (b) has the same configuration as the thermoelectric conversion material 1 of FIG. 1 sandwiched between two electrode materials 2a and 2b.

In the thermoelectric power generation module 60 according to the embodiment of the present invention of FIG. 5, 16 thermoelectric conversion elements 40 having the shape (b) are arranged in parallel between the upper substrate 61 having a high temperature and the lower substrate 62 having a low temperature. Is located in. Of the 16 thermoelectric conversion elements 40, eight are P-type and eight are N-type, and one is alternately arranged in parallel. The thermoelectric conversion element 40 of (b) has the same configuration as the thermoelectric conversion material 3 having the through hole 5 of FIG. 3A sandwiched between the two electrode materials 4a and 4b. The thermoelectric conversion elements 10 and 40 of FIGS. 4 and 5 are basically the same in other configurations except that the shapes of the thermoelectric conversion elements (presence or absence of through holes) are different.

Table 1 below shows the basic specifications of the thermoelectric conversion element 40 according to the embodiment of the present invention shown in FIG. 5 (b). If the part names in the last two rows in the table are the holeless P-type element and the holeless N-type element in FIG. 4 (b), the conventional thermoelectric conversion element 10 in FIG. 4 (b) has the same specifications (size). , Materials, etc.). As the high-temperature side and low-temperature side substrates in the table, a substrate made of silicon nitride with 0.2 mm thick copper attached to the surface was used. The number after the element name of Sn63Pb37 of the low temperature side bonding material in the table means atomic%, and mp183 ° 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%. The unit of size in the table is millimeter (mm), and Φ2 indicates that the diameter of the through hole is 2 mm.

FIG. 6 shows that in each of the thermoelectric power generation modules of FIGS. 4 and 5, a temperature load of 500 ° C. on the high temperature side and 50 ° C. on the low temperature side is applied, and the passing heat flow between the upper and lower electrodes is measured in order to derive the power generation efficiency at that time. The result of this is shown. The graph of A is the heat flow Q (W) of the thermoelectric power generation module 60 according to the embodiment of the present invention of FIG. 5, and the graph of B is the heat flow Q (W) of the conventional thermoelectric power generation module 50 of FIG. The heat flow Q of the present invention 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 between the two, the thermoelectric power generation module 60 of the embodiment of the present invention of FIG. 5 was able to reduce (suppress) the passing heat flow by about 69% as compared with the conventional structure of FIG.

FIG. 7 shows the thermoelectric conversion efficiency η (%) from heat to electricity obtained under the measurement conditions of FIG. The graph of A is the conversion efficiency η (%) of the thermoelectric power generation module 60 according to the embodiment of the present invention in FIG. 5, and the graph of B is the 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 between the two, in the thermoelectric power generation module 60 of the embodiment of the present invention of FIG. 5, the conversion efficiency η could be increased (improved) by about 70% as compared with the conventional structure of FIG.

It is considered that the improvement of the conversion efficiency η in FIG. 7 is largely due to the effect of reducing the heat flow Q in 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.}

An embodiment of the present invention has been described with reference to the drawings. However, the present invention is not limited to these embodiments. Further, the present invention can be carried out in a mode in which various improvements, modifications and modifications are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention. For example, instead of the through hole on the side surface of the thermoelectric conversion element, an opening having a depth halfway not penetrating the thermoelectric conversion material may be provided to obtain the same heat flow reduction effect. At that time, the heat flow rate released can be adjusted according to 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 calibrating the evaluation device of the thermoelectric power generation module.

1, 3, 11, 11'Thermoelectric conversion material 2a, 2b, 4a, 4b Electrode material 5, 6, 7 Through holes 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 (6)

It is a thermoelectric power generation module for calibration of the evaluation device of the thermoelectric power generation module.
Includes multiple thermoelectric conversion elements arranged in parallel between the upper and lower electrodes
A thermoelectric power generation module for calibration, characterized in that a plurality of through holes are provided on each side surface of the plurality of thermoelectric conversion elements so as to be orthogonal to each other inside the thermoelectric conversion element. Each of the plurality of thermoelectric conversion elements has a rectangular parallelepiped shape.
The through hole is calibrated thermoelectric power generation module according to claim 1, characterized in that provided on each of the two side surfaces adjacent the thermoelectric conversion element. The calibration thermoelectric power generation module according to claim 2 , wherein a plurality of through holes are provided on each side surface of the thermoelectric conversion element. The calibration thermoelectric power generation module according to any one of claims 1 to 3 , wherein the cross section of the through hole has a circular or rectangular shape. The calibration thermoelectric power generation module according to any one of claims 1 to 4 , wherein the plurality of thermoelectric conversion elements include P-type thermoelectric conversion elements and N-type thermoelectric conversion elements arranged alternately in the lateral direction. The thermoelectric power generation module for calibration according to any one of claims 1 to 5 , 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.

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