JP2010135620A - Thermoelectric conversion module, and generator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric conversion module capable of achieving an increase in power generation quantity by achieving a large difference in temperature in an element: and to provide a generator using the thermoelectric conversion module. <P>SOLUTION: The thermoelectric conversion module includes: a substrate 201 made of a foaming body; a plurality of upper plate electrodes 202 and lower plate electrodes 203 which are provided on both the surfaces of the substrate; a plurality of through-holes 204 penetrating through a region where the substrate and each electrode are superimposed; an n-type thermoelectric conversion element 205 embedded in one of the through-holes of each electrode; and a p-type thermoelectric conversion element 206 embedded in the other through-hole. The thermoelectric conversion module has a structure in which the end sides of the thermoelectric conversion elements 205, 206 are electrically connected to the upper and lower plate electrodes respectively so that a plurality of pairs of thermoelectric conversion elements 205, 206 can be arranged in series, and one electrode side is arranged on a high temperature side and the other electrode side is arranged on a low temperature side. The generator generates power based on the difference in temperature between a solar cell and the ambient air by allowing the module to contact the backside of the solar cell. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermoelectric conversion module that converts heat into electricity using a temperature difference and a power generation device in which the thermoelectric conversion module is connected to a solar cell.

  As global warming has progressed and problems such as bad weather and rising seawater have become seriously serious, solar cells are not only important in Japan as an energy source that does not emit carbon dioxide, a greenhouse gas, It is also recognized in Europe and the United States, and its introduction into homes and offices has become popular. Seventy percent of the solar cells introduced are Si-based solar cells, most of which are crystalline (single crystal or polycrystalline).

During midsummer daytime, the solar energy falling on the earth is about 1000 W / m ² , and the average power generation amount under these optimum conditions of these solar cells is about 150 W / m ² . That is, the conversion efficiency is about 15%. However, in reality, it depends strongly on the latitude of the place where you live, the orientation of the house, the presence of obstacles, the difference in season, the weather, and the like, and the value of 15% is realized throughout the year. is not.

The average amount of power required in an average home will be about 4 kW, but if the average home wants to introduce solar cells, about 26 m ² will be required. Considering effective efficiency, about 40 m ² will be necessary. Securing such a roof area is not so easy. Therefore, in order to make the area as small as possible, a solar cell unit having a high conversion efficiency is required.

  Further, during the daytime of midsummer, the solar cell temperature is 80 ° C. or higher in the time zone where the amount of power generation is the largest for the solar cell. When the temperature of a crystalline silicon solar cell rises to 80 ° C., it falls by 20 to 30% from the conversion efficiency at room temperature. In order to compensate for the decrease in efficiency, the area of the solar cell placed on the roof has to be increased, which is not only expensive, but it is also difficult to secure the area on the roof. If the effective efficiency of the solar cell can be increased, the required solar cell area on the roof can be reduced, leading to cost reduction. For these reasons, an inexpensive solar cell with high power generation efficiency is desired.

  In the past, there has been an idea to generate electricity by attaching a thermoelectric conversion element to the back surface of the solar cell by using the fact that the solar cell itself is close to 80 ° C. around noon in midsummer sunny weather (Patent Documents 1 and 2). But it has not been realized as a business. The reason for this is that it is difficult to produce a conventional thermoelectric conversion element, so that only an element with a small area can be produced. Therefore, the complexity of the process of adhering the element to the back of a large solar cell is also cited.

  There is also a situation that the thermoelectric conversion element is too expensive. This is a structure of a conventional thermoelectric conversion element using the Seebeck effect, and a structure in which a p-type and an n-type element are coupled in a “π” shape to stand vertically to a lower substrate. It is necessary to connect n-type-p-type in series, and the thermoelectric material generally used is Bi-Te, which is a brittle material and difficult to join with solder. For this reason, the reason is that it can only be made by hand.

  For this reason, it is not realistic to use it for the back surface of the solar cell substrate, which is indispensable for a low price, and has not actually appeared in the market as a product.

  Under such a technical background, Patent Literature 3 and Non-Patent Literature 1 propose thermoelectric conversion elements that can generate power efficiently. That is, this thermoelectric conversion element is formed such that a thin film p-type thermoelectric conversion element made of a p-type material and a thin film n-type thermoelectric conversion element made of an n-type material are connected in series, and are formed on both sides thereof. A thermoelectric conversion unit is formed by forming electrodes, and a flexible film-like substrate composed of two types of materials having different thermal conductivities is provided on both sides of the thermoelectric conversion unit. On the unit side, a film is provided with a material such as polyimide resin, which is an insulator with low thermal conductivity, and on the side opposite to the joining surface of the thermoelectric conversion unit, a metal material such as copper with high thermal conductivity is in the form of the film. It is provided so that it may be located in a part of outer surface of a board | substrate.

  By adopting such a configuration, a temperature difference is generated inside the film substrate from the difference in heat flux of each layer when a temperature difference is applied to the upper and lower surfaces of the film substrate, and the thickness direction of the film substrate The temperature gradient is efficiently converted into a temperature gradient in the in-plane direction of the film-like substrate, and the temperature gradient is used to efficiently generate power with the thermoelectric conversion unit. The inventions described in Patent Document 3 and Non-Patent Document 1 have high mechanical strength, excellent workability, are easy to automate, can be mass-produced, and are flexible to curved surfaces. The object of the present invention is to provide a thermoelectric conversion element with high power generation efficiency that can be installed and is not limited in installation location.

  Specifically, using a mask, a p-type and n-type thermoelectric material is formed on the resin sheet by sputtering while controlling the element structure to form a thermoelectric conversion element portion, and the thermoelectric conversion element The thermoelectric conversion element is sandwiched by attaching another resin sheet on the part.

  Next, on both outer side surfaces of the bonded resin sheet and in a portion corresponding to the joint portion of the p-type and n-type thermoelectric conversion elements, a metal having good thermal conductivity such as copper is used to have the same size as the joint portion. Form an isomorphic pattern. A cross section of this structure is shown in FIG.

  Actually, a thermoelectric conversion element (FIG. 1) is formed on the back surface of a polyimide sheet (shown as material-A in FIG. 1) with copper (shown as material-B in FIG. 1) coated or pasted on one side. The other side of the polyimide sheet with no copper attached is bonded onto the thermoelectric conversion element, and the copper thin films on both surfaces of the bonded sheet are etched. To cut the desired pattern. This copper part comes into contact with the high temperature part and the low temperature part. Due to the heat conduction from there, there was a temperature difference in the thermoelectric conversion element parallel to the resin sheet surface, and power was generated.

  However, in this method, the heat conduction from the temperature contact portion on the high temperature side and the low temperature side (hereinafter referred to as the temperature contact portion) is only the heat conduction by thermal diffusion in the resin, and therefore the heat conductivity to the thermoelectric conversion element. However, it is difficult to have a temperature gradient in the thermoelectric conversion element, so that the amount of power generation is reduced.

  By the way, as for power generation efficiency, a certain temperature difference can be realized by bonding an object having a large heat capacity between the high temperature part and the low temperature part, for example, when one is thermally connected to the high temperature part and the other is radiated to the atmosphere. There are conditions for maximum efficiency. If the power generation amount is to be increased when the temperature between the high temperature part and the low temperature part is a fixed temperature, it is better that the thermoelectric conversion elements are densely arranged in the space and the length of the thermoelectric conversion elements is short (thermoelectricity). The thickness of the element module should be thin). This is because the amount of power generation is inversely proportional to the length of the thermoelectric element and proportional to the cross-sectional area.

  In order to maximize the amount of power generated by the thermoelectric element, a thermoelectric module described in Patent Document 4 is known as an example in which the cross-sectional area of the thermoelectric element is focused. That is, in the thermoelectric module in which the upper and lower electrode surfaces of the P-type thermoelectric element and the N-type thermoelectric element are connected to the electrodes and the P-type thermoelectric element and the N-type thermoelectric element are arranged between the vertically opposed substrates, The cross-sectional area ratio of the P-type and N-type thermoelectric elements cut by a plane parallel to the surface is the minimum product of the average value of the electrical resistance value and the average value of the thermal conductivity of the P-type and N-type thermoelectric elements. It was characterized by doing so. In this thermoelectric module, even if there is a difference in electrical characteristics and thermal characteristics between the P-type thermoelectric element and the N-type thermoelectric element, the performance of both types of thermoelectric elements can be maximized. In addition, there is an advantage that a structural performance deterioration factor is not newly generated.

However, in the thermoelectric module described in Patent Document 4, the region where the P-type thermoelectric element and the N-type thermoelectric element do not exist in the module is a simple space (non-thermoelectric element space) due to the structure of the module. There was still room for improvement in order to maximize the amount of power generated by the thermoelectric elements.
JP 2001-53322 A JP 2003-69070 A JP 2006-186255 A Japanese Patent Application Laid-Open No. 11-274577 NEDO 2006 Research Grants Project Results Report Industrial Technology Research Grants Project “Energy / Environmental Technology” Project ID: 03B70010c = Presentation of “Research and development of sheet-like flexible thermoelectric conversion elements for low-temperature waste heat utilization” "Urethane rubber elastic body", "Properties of porous body and its applied technology", March 30, 1999, published by Masafumi Ishii, Fuji Techno System, page 210 Figure 6. "Performance of various heat insulating materials"

  The present invention has been made paying attention to such problems, and the problem is that the upper and lower electrode surfaces of the P-type thermoelectric element and the N-type thermoelectric element are connected to the electrodes and face each other vertically. In a thermoelectric module having a structure in which a P-type thermoelectric element and an N-type thermoelectric element are arranged between them, a preferable new structure for maximizing the amount of power generation is provided, and “the thermal conductivity of the thermoelectric conversion element and An object of the present invention is to provide a thermoelectric module structure that can adjust the amount of power generation to the maximum from the relationship between the product of the cross-sectional area and the product of the cross-sectional area of the non-thermoelectric element space and the thermal conductivity.

  Then, in order to solve the said subject, as a result of this inventor's earnest examination, it came to obtain the following technical knowledge.

  That is, in a thermoelectric conversion module that converts heat into electricity using a temperature difference, when one is thermally connected to a high temperature part and the other is radiated to the atmosphere, the thermoelectric element is shortened or the cross-sectional area is increased. Then, although the thermal conductivity of the thermoelectric element is smaller than that of a normal metal but larger than the atmosphere, the temperature difference between the high temperature part and the low temperature part becomes small. And since electric power generation amount is proportional to the square of a temperature difference, it is disadvantageous that a temperature difference becomes small.

  Accordingly, in the thermoelectric module having a structure in which the upper and lower electrode surfaces of the P-type thermoelectric element and the N-type thermoelectric element are connected to the electrodes and the P-type thermoelectric element and the N-type thermoelectric element are arranged between the vertically opposed substrates. May have optimal placement and dimensions. In addition, a smaller thermal conductivity of the space where the thermoelectric element does not dominate (that is, the non-thermoelectric element space where no thermoelectric element exists) is advantageous for creating a large temperature difference.

  From these technical findings, we find a new thermoelectric module structure suitable for maximizing the amount of power generation, and to maximize the power generation amount of the thermoelectric module structure, see “Thermal conductivity of thermoelectric conversion element and It has been found that there is a strict relationship between the product of the cross-sectional area and the product of the cross-sectional area of the non-thermoelectric element space and the thermal conductivity.

  The present invention has been completed based on such technical findings.

That is, the invention according to claim 1
In thermoelectric conversion module,
A substrate made of foam, a plurality of upper plate-like electrodes provided on the upper surface side of the substrate and not electrically connected to each other, and a plurality of lower plate-like electrodes provided on the lower surface side of the substrate and not electrically connected to each other Embedded in the electrode, a plurality of through holes provided in the region where the upper plate electrode and the lower plate electrode of the substrate overlap or in the vicinity region, and one through hole provided in or near each plate electrode An n-type thermoelectric conversion element made of an n-type material and a p-type thermoelectric conversion element made of a p-type material embedded in the other through-hole provided in or near each plate-like electrode, Alternatively, each end side of a pair of n-type thermoelectric conversion element and p-type thermoelectric conversion element provided in the vicinity is electrically connected to the corresponding upper plate electrode and lower plate electrode, respectively. Multiple sets of p-type thermoelectrics The conversion element and the n-type thermoelectric conversion element are arranged in series, the upper plate electrode or the lower plate electrode side is arranged on the high temperature side, and the other electrode side is arranged on the low temperature side. is there.

Next, the invention according to claim 2
In the thermoelectric conversion module according to the invention of claim 1,
The p-type thermoelectric conversion element and the n-type thermoelectric conversion element have thermal conductivity κp and κn, respectively, and the p-type thermoelectric conversion element and the n-type thermoelectric conversion element have cross-sectional areas Sp and Sn, respectively. When the thermal conductivity of the region where the p-type thermoelectric conversion element and the n-type thermoelectric conversion element are not embedded is κo and the cross-sectional area of the region is So,
1.2 × (κp · Sp + κn · Sn) ≧ κo × So (Formula 1)
And having the relationship
0.8 × (κp · Sp + κn · Sn) ≦ κo × So (Formula 2)
It has the relationship of
The invention according to claim 3
In thermoelectric conversion module,
A plurality of thermoelectric conversion modules according to claim 1 or 2 are stacked via an electrical insulating layer, and the plate electrode side of one thermoelectric conversion module located on the outermost side is disposed on the high temperature side and located on the outermost side. The plate electrode side of the other thermoelectric conversion module is arranged on the low temperature side,
The invention according to claim 4
In the thermoelectric conversion module which concerns on the invention in any one of Claims 1-3,
The plate-like electrode side of the thermoelectric conversion module disposed on the high temperature side or the low temperature side is an atmospheric heat radiation type.

The invention according to claim 5
In the thermoelectric conversion module which concerns on the invention in any one of Claims 1-4,
The thermal conductivity of the substrate made of foam is 0.03 W / mK or less,
The invention according to claim 6
In the thermoelectric conversion module according to the invention of claim 5,
The foam material constituting the substrate is one or more selected from expanded polystyrene, polystyrene foam, urethane foam, phenol foam, and glass wool.

Next, the invention according to claim 7 provides:
In the power generator,
The thermoelectric conversion module according to any one of claims 1 to 6 is adhered to the back side of the solar cell, and the power is generated by a temperature difference between the solar cell and the outside air,
The invention according to claim 8 provides:
In the power generator according to claim 7,
When the thermal conductivity of the adhesive used for bonding the solar cell and the thermoelectric conversion module is (W / mK) and the thickness of the adhesive is (d), the ratio of (W / mK) / (d) is 1000 or more. It is characterized by
The invention according to claim 9 is:
In the power generator according to claim 7,
The solar cell is an amorphous Si solar cell,
The invention according to claim 10 is:
In the power generator according to claim 7,
When the temperature on the surface side in contact with the solar cell in the thermoelectric conversion module is lower than the temperature on the surface side not in contact with the solar cell, a switch that switches between positive and negative of electricity is provided in the circuit of the thermoelectric conversion module It is characterized by being.

  The thermoelectric conversion module according to the present invention includes a substrate made of a foam, a plurality of upper plate electrodes that are provided on the upper surface side of the substrate and are not electrically connected to each other, and provided on the lower surface side of the substrate and that are electrically connected to each other. A plurality of lower plate electrodes that are not connected, a plurality of through-holes that are opened in a region where the upper plate electrode and the lower plate electrode of the substrate overlap or in the vicinity thereof, and provided in or near each plate electrode An n-type thermoelectric conversion element made of n-type material embedded in one through-hole and a p-type thermoelectric conversion element made of p-type material embedded in the other through-hole provided in or near each plate-like electrode And a pair of n-type thermoelectric conversion elements and p-type thermoelectric conversion elements provided in or near each plate-like electrode are electrically connected to the corresponding upper plate-like electrode and lower plate-like electrode respectively. Connected A plurality of sets of p-type thermoelectric conversion elements and n-type thermoelectric conversion elements are arranged in series via equal plate electrodes, the upper plate electrode or lower plate electrode side is arranged on the high temperature side, and the other electrode side is low temperature It has a structure arranged on the side.

And according to the thermoelectric conversion module according to the present invention,
Thermal conductivity compared to conventional thermoelectric conversion modules in which the space where the thermoelectric element does not dominate (non-thermoelectric element space where no thermoelectric element exists) is made of foam such as polystyrene foam or glass wool, and the space is made of air. As a result, a large temperature difference is realized in the thermoelectric conversion module, so that the power generation amount can be increased and improved.

In particular, the thermal conductivity of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element is κp and κn, respectively, and the cross-sectional areas of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element are Sp and Sn, respectively. When the thermal conductivity of the region where the p-type thermoelectric conversion element and the n-type thermoelectric conversion element of the substrate are not embedded is κo and the cross-sectional area of the region is So,
1.2 × (κp · Sp + κn · Sn) ≧ κo × So (Formula 1)
And having the relationship
0.8 × (κp · Sp + κn · Sn) ≦ κo × So (Formula 2)
Thus, the maximum power generation amount can be obtained.

  Furthermore, by adhering the thermoelectric conversion module according to the present invention to the back surface side of the solar cell, the power generation efficiency in the solar cell can be assisted, and the effective power generation efficiency of the solar cell can be increased.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a thermoelectric conversion module 200 according to the present invention is provided on a substrate 201 made of a foam as shown in FIG. A plurality of upper plate-like electrodes 202 that are not electrically connected to each other, a plurality of lower plate-like electrodes 203 that are provided on the lower surface side of the substrate 201 and are not electrically connected to each other, and the substrate 201 A through hole 204 that passes through the region where the side plate electrode 202 and the lower plate electrode 203 overlap and is provided for each of the upper plate electrode 202 and the lower plate electrode 203, and for each of the plate electrodes 202, 203 An n-type thermoelectric conversion element 205 made of an n-type material embedded in one through-hole 204 and a p-type embedded in the other through-hole 204 of each plate electrode 202, 203. A p-type thermoelectric conversion element 206 made of a material, and an n-type thermoelectric conversion element 205 of each plate-like electrode 202, 203 and an upper plate-like electrode 202 corresponding to each end side of the p-type thermoelectric conversion element 206 and a lower plate-like shape. A plurality of sets of n-type thermoelectric conversion elements 205 and p-type thermoelectric conversion elements 206 are arranged in series via the plate-like electrodes 202 and 203 respectively connected to the electrodes 203, and the upper plate-like electrode 202 or the lower plate-like electrode 203 side is arranged on the high temperature side, and the other electrode side is arranged on the low temperature side.

  Further, as shown in FIG. 3, a thermoelectric conversion module 300 according to a modification of the present invention includes a substrate 301 made of a foam and a plurality of upper plate-like members that are provided on the upper surface side of the substrate 301 and are not electrically connected to each other. The electrode 302, a plurality of lower plate electrodes 303 that are provided on the lower surface side of the substrate 301 and are not electrically connected to each other, and are opened in the vicinity of the upper plate electrode 302 and the lower plate electrode 303 of the substrate 301. A plurality of through-holes 304, an n-type thermoelectric conversion element 305 made of an n-type material embedded in one through-hole 304 provided in the vicinity of each plate-like electrode 302, 303, and the vicinity of each plate-like electrode 302, 303 And a p-type thermoelectric conversion element 306 made of a p-type material embedded in the other through-hole 304 provided in the plate, and a set of n-type heat provided in the vicinity of the plate electrodes 302 and 303. Each end side of the conversion element 305 and the p-type thermoelectric conversion element 306 is electrically connected to the corresponding upper plate-like electrode 302 and lower plate-like electrode 303, and a plurality of sets of n are connected via these plate-like electrodes 302, 303. Type thermoelectric conversion element 305 and p type thermoelectric conversion element 306 are arranged in series, upper plate electrode 302 or lower plate electrode 303 side is arranged on the high temperature side, and the other electrode side is arranged on the low temperature side It has a structure.

  2 and 3, according to the thermoelectric conversion modules 200 and 300, the space 201 where the thermoelectric element does not dominate (the non-thermoelectric element space where no thermoelectric element exists) is made of a foam 201 such as expanded polystyrene or polystyrene foam. 301, and the thermal conductivity is smaller than that of the conventional thermoelectric conversion module in which the space is made of air, thereby realizing a large temperature difference in the thermoelectric conversion modules 200 and 300. Therefore, the power generation amount can be increased and improved.

  For the thermoelectric conversion module 200 shown in FIG. 2, as shown in Example 2 below, these electrode surfaces are made of resin so as to ensure electrical insulation between the upper plate electrode 202 and the lower plate electrode 203. The structure may be covered with a sheet or the like.

Further, for the thermoelectric conversion module 300 shown in FIG. 3, as shown in Example 1 below, on the pair of electrode substrates such as alumina, the upper plate electrode 302 and the connection portions N and P with each element, and After forming the lower plate-like electrode and the connection portion with each element, and forming the plurality of sets of the n-type thermoelectric conversion element 305 and the p-type thermoelectric conversion element 306 on the substrate 301 made of foam, For the electrode on which the upper plate-like electrode 302 is formed, the substrate 301 is aligned with the ends of the n-type thermoelectric conversion element 305 and the p-type thermoelectric conversion element 306 and the connection portions of the electrode substrate. A structure may be adopted in which the substrate is sandwiched between the electrode substrate on which the lower plate-like electrode 303 is formed.

1. Conditions of heat flow that maximizes the power generation amount of the thermoelectric conversion module according to the present invention When considering the power generation amount of the thermoelectric conversion module according to the present invention, the power generation amount is maximized when one plate-like electrode side is an air radiation type. A vertical thermoelectric conversion element in which thermoelectric conversion elements are arranged substantially vertically with respect to the simplest electrode plate in order to obtain the optimum value of the heat flow conditions and the resulting cross-sectional area ratio, specifically shown in FIG. A structure composed of a pair of a p-type thermoelectric conversion element (P) and an n-type thermoelectric conversion element (N) is considered.
(1) Definition of heat flow In the thermoelectric conversion module shown in FIG. 4, it is assumed that the electrode on the left side of the drawing is in contact with the high temperature side (temperature T1), and the electrode on the right side of the drawing is radiated to the atmosphere (temperature T3). The temperature on the low temperature side of the thermoelectric conversion module is assumed to be T2.

  Heat is radiated from the low temperature contact portion (temperature T2) to the atmosphere, and the heat transfer coefficient at that time is α (α = 5 to 20). In addition, the cross-sectional area (A2) of the p-type thermoelectric conversion element (P), the cross-sectional area (A3) of the n-type thermoelectric conversion element (N), the total area per pair of conversion elements (A0), the heat of the thermoelectric conversion element The conductivity (κ2, κ3), the thermal conductivity (κ1) of a space where there is no thermoelectric element (non-thermoelectric element space), and the length (L) of each thermoelectric conversion element.

The heat flow (Q0) lost by heat radiation from the low temperature contact portion (temperature T2) on the right side of FIG.
Q0 = α · A0 · (T2-T3)
There are three types of heat flow from the high temperature side to the low temperature side per conversion element.

Q1 = κ1 · (A1 / L) · (T1-T2)
Q2 = κ2 · (A2 / L) · (T1-T2)
Q3 = κ3 · (A3 / L) · (T1-T2)
Here, the following relationship must be established between these heat flows.

Q0 = Q1 + Q2 + Q3 (1)
Further, there is the following relationship between the cross-sectional areas.

A1 = A0− (A2 + A3)
From simple calculations,

この素子により発電される電気量は、簡単のためｐ型とｎ型の断面積が等しい（Ａ２＝Ａ３）とすると、以下のようになる。

The amount of electricity generated by this element is as follows, assuming that the cross-sectional areas of p-type and n-type are equal (A2 = A3) for simplicity.

ここで、Ｐｆはパワーファクターと呼ばれる値で、熱電変換素子の物理定数できまる。

Here, Pf is a value called a power factor, which is determined by the physical constant of the thermoelectric conversion element.

ここで、ρｐ、ρｎは、熱電変換素子ｐ型、ｎ型のそれぞれの電気伝導度、Ｓはゼーベック係数である。

Here, ρp and ρn are the electric conductivities of the thermoelectric conversion elements p-type and n-type, respectively, and S is the Seebeck coefficient.

  The heat flow ratio (Q2 + Q3) / Q1 and the relationship between the cross-sectional area ratios A2 and A0 when the power generation amount Pw is maximized are obtained. A simple calculation results in the following case.

（Ｑ２＋Ｑ３）とＱ１の熱流の比は、

The ratio of heat flow between (Q2 + Q3) and Q1 is

断熱層は熱伝導度が小さく、κ２〜κ３>>κ１、αＬ≧κ１ということを考慮すると

The heat insulating layer has low thermal conductivity, and considering that κ2 to κ3 >> κ1 and αL ≧ κ1

となる。

It becomes.

  That is, the heat flow flowing through the thermoelectric element portion and the heat flow flowing through the thermoelectric element portion are substantially the same. Since the thickness is common, this condition is defined as the thermal conductivity (κt), the cross-sectional area (St) of the thermoelectric element, and the thermal conductivity (κa) of the low thermal conductivity foam (heat insulating material) excluding the thermoelectric element. ), The cross-sectional area (Sa), it can be expressed as κa × Sa = κt × St. Then, when obtaining the condition that the power generation amount is 80% or more of the maximum value, the relationship of approximately 0.8 × κa × Sa ≧ κt × St is established, and 1.2 × κa × Sa ≦ κt × St I understood that.

If you put a realistic value for the area ratio,
(A2 + A3) / A0 = 2 · (A2 / A0)
= 2 · (αL + κ1) / (2κ2)
This corresponds to ˜2 · αL / (2κ2) to 0.08 · Q1 to (Q2 + Q3), and at this time, the amount of power generation is maximized.

(2) Another boundary condition: Case of constant heat inflow Consider the case of constant heat inflow as shown in FIG.

At this time,
Q1 = κ1 · (A1 / L) · (T1-T2)
Q2 = κ2 · (A2 / L) · (T1-T2)
Q3 = κ3 · (A3 / L) · (T1-T2)
The relationship becomes true.

Q0 = Q1 + Q2 + Q3 = α (A1 + A2 + A3) · (T2-T3)
Q0 = (T1-T2) (κ1 · A1 + κ2 · A2 + κ3 · A3) / L
Is established.

ここで発電量は、

Here, the power generation amount is

ΔＴを代入して

Substituting ΔT

Ａ２／Ａ０＝κ１／（２κ２）のとき、発電量は最大値をとり、その値は、

When A2 / A0 = κ1 / (2κ2), the power generation takes the maximum value, and the value is

熱流比を求める。

Obtain the heat flow ratio.

現実的な数値で考えると
κ１／κ２＝０．０３
従って、同様に

Considering realistic values, κ1 / κ2 = 0.03
Therefore, as well

のとき、発電量が最大となる。

In this case, the amount of power generation is maximized.

  Since the thickness is common, this condition is that the thermal conductivity of the thermoelectric conversion element (κt), the cross-sectional area (St), and the thermal conductivity of the foam (heat insulating material) with low thermal conductivity excluding the thermoelectric element ( κa) and cross-sectional area (Sa), it can be expressed as κa × Sa = κt × St.

And when obtaining the condition that the power generation amount is 80% or more of the maximum value,
The relationship of 1.2 × κa × Sa ≧ κt × St is established, and
It was found that 0.8 × κa × Sa ≦ κt × St must be satisfied.

2. Configuration of Thermoelectric Conversion Module (1) Thermoelectric Conversion Module The thermoelectric conversion module according to the present invention has a structure as shown in FIGS. 2 and 3, for example. That is, the thermoelectric conversion module according to the present invention is provided with a foam substrate, a plurality of upper plate electrodes provided on the upper surface side of the substrate and not electrically connected to each other, and provided on the lower surface side of the substrate and electrically connected to each other. A plurality of lower plate-like electrodes that are not connected to each other, a plurality of through-holes opened in a region where the upper plate-like electrode and the lower plate-like electrode of the substrate overlap or in the vicinity thereof, and in or near each plate-like electrode An n-type thermoelectric conversion element made of an n-type material embedded in one provided through-hole and a p-type thermoelectric made of a p-type material embedded in the other through-hole provided in or near each plate-like electrode A pair of n-type thermoelectric conversion elements and p-type thermoelectric conversion elements provided in or near each plate-like electrode, and corresponding to the upper plate-like electrode and the lower plate-like electrode respectively corresponding to each end side Contact A plurality of sets of p-type thermoelectric conversion elements and n-type thermoelectric conversion elements are arranged in series via these plate-like electrodes, and the upper plate-like electrode or lower plate-like electrode side is arranged on the high temperature side and the other The electrode side is arranged on the low temperature side.

  And the thermoelectric conversion module shown in FIG. 2 can be manufactured through processes as shown in the manufacturing process diagram of FIG. 6, for example.

  That is, a metal foil such as copper is bonded to both surfaces of a foamed resin plate such as polystyrene foam, and a plurality of upper surfaces as shown in FIG. Side plate electrodes 202 and lower plate electrodes 203 are formed.

Next, a plurality of through holes having a rectangular cross section are formed by punching in a region where the upper plate electrode 202 and the lower plate electrode 203 overlap through the foamed resin plate, and the n-type thermoelectric conversion element 205 is provided in these through holes. 2 and p-type thermoelectric conversion element 206 are embedded and soldered to form a structure as shown in FIG. 2, and the upper plate electrode and the lower plate electrode side are covered with a resin sheet as necessary. A thermoelectric conversion module as shown in FIG. 7 is obtained.

(2) Thermoelectric conversion materials As thermoelectric conversion materials, siliceous FeSi ₂ , SiGe, etc., which have low thermoelectric properties but are resource abundant in addition to chalcogen compounds such as IrSb ₃ , Bi ₂ Te ₃ , and PbTe that have high performance. Things. Also, by adding various additive elements such as P, B, and Al alone or in combination so that the carrier concentration in the Si semiconductor is about 10 ²⁴ (1 / m ³ ) and adjusting the addition amount, Seebeck A Si-based thermoelectric conversion material having a very large coefficient and significantly improved thermoelectric conversion efficiency can also be used. In addition, any known material can be used. In Si, at least one of Ge, C, and Sn is 5 to 10 atomic%, and at least one of additive elements for making Si a p-type semiconductor or an n-type semiconductor is 0.001 atomic% to 20 atomic%. Si-based thermoelectric conversion materials such as Si-based thermoelectric conversion materials containing a crystal structure in which one or more of Ge, C, and Sn or further one or more of additional elements are precipitated are included in the grain boundary portion of polycrystalline Si. This is preferable because the conversion efficiency is remarkably high.

  As a dopant element for making Si a p-type semiconductor, a p group group (Be, Mg, Ca, Sr, Ba, Zn, Cd, Hg, B, Al, Ga, In, Tl), a transition metal element group ( One or more selected from each group of Y, Mo, Zr) are desirable. Particularly preferable elements are B, Ga, and Al.

Further, dopant elements for making an Si-based thermoelectric conversion material an n-type semiconductor include n group groups (N, P, As, Sb, Bi, O, S, Se, Te), transition metal element groups (Ti, V , Cr, Mn, Fe, Co, Ni, Cu, Nb, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Pt, Au, provided that Fe is 10 atomic% or less) One or more selected from each group of rare earth elements (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu) are desirable. Particularly preferable elements are P, Cu, and As.

(3) Low thermal conductivity material (substrate material made of foam)
Normally, the thermal conductivity of the atmosphere is very low, but when there are two substantially parallel temperature electrodes, the thermal conductivity between the two temperature electrodes is not limited to the heat conduction by atmospheric molecules, but also the heat conduction by radiation. is there. This is particularly noticeable when the temperature difference between the two electrodes is large. For example, when there is a temperature difference of 100 ° C. between two temperature electrodes, the heat conduction between two electrodes having a distance of 3 mm is calculated, and the Stefan Boltzmann constant is σ = 5.67 × 10 ⁻⁸ W / m. when the ² K ^4, determine the effective thermal conductivity of thermal radiation. At this time, an effective thermal conductivity κ can be defined.

Q = σS (T1 ⁴ −T2 ⁴ ) = (κ / L) · (T1−T2) S
Area S is canceled on both sides, and if T1 = 400K and T2 = 300K are substituted,
κ / L = 9.92.

When L = 3 × 10 ⁻³ m, κ = 0.029 W / mK and not necessarily small.

Therefore, it can be seen that it is preferable to use a material having the following thermal conductivity. As a candidate for a material having low thermal conductivity, there are hard urethane foam, phenol foam, hard PVC foam, glass wool and the like listed in the graph of FIG. 8 (see Non-Patent Document 2).

(4) Effect of inserting a low thermal conductive material (a substrate material made of foam) between the electrodes When the conditions regarding the thermoelectric material (for example, the material, size, number, etc. of the thermoelectric element) are the same, the non-thermoelectric element space (hereinafter, The lower the thermal conductivity of the heat insulating layer (which may be called a heat insulating layer), the larger the amount of power generation. The simulation result is shown in FIG. It can be seen that the lower the thermal conductivity of the heat insulating layer, the greater the temperature difference between the upper and lower sides, and the greater the amount of power generation.

3. A structure in which a plurality of thermoelectric conversion modules are stacked via an electrical insulation layer. For example, a plurality of thermoelectric conversion modules as shown in FIGS. 2 and 3 are stacked via an electrical insulation layer and located on the outermost side. Alternatively, the thermoelectric conversion module may have a structure in which the plate electrode side of one thermoelectric conversion module is arranged on the high temperature side and the plate electrode side of the other thermoelectric conversion module located on the outermost side is arranged on the low temperature side.

4). Power Generation Device The power generation device according to the present invention is characterized in that the thermoelectric conversion module is bonded to the back side of the solar cell and generates power with a temperature difference between the solar cell and the outside air temperature.

  With such a configuration, it is possible to generate power using the temperature difference between the back surface of the solar cell and the outside air temperature, thereby improving the decrease in power generation efficiency due to the temperature increase of the solar cell.

By the way, in the power generation device according to the present invention, the thermal conductivity of the adhesive used for bonding the solar cell and the thermoelectric conversion module and the thickness of the adhesive are related to the power generation efficiency, and the thermal conductivity of the adhesive is (W / mK), where the thickness of the adhesive is (d), the ratio of (W / mK) / (d) is preferably 1000 or more. The heat flowing through the resin, which is a low thermoelectric material of about 0.1 (W / mK), is about 0.1 / 10 ⁻³ = 100 when the thickness is about 1 mm. Since it should not become a thermal resistance at the bonding portion with the solar cell, the heat flow in the bonding portion is 10 times or more compared to the heat flow of the resin, that is, the ratio of (W / mK) / (d) is 1000 or more. Is desirable.

  Here, the kind of solar cell to which the thermoelectric conversion module according to the present invention is bonded is not particularly limited, and examples thereof include amorphous Si solar cells. Amorphous Si solar cells have a larger solar absorption coefficient than crystalline Si solar cells, so the film thickness of Si is 1 μm or less. In addition, since amorphous Si can be formed on a resin, a flexible solar cell can be made. However, since the power generation efficiency is low, about 8% on average, the type mounted on the roof requires a large area to achieve 4 kW, and the range of use is limited even at a low price. However, unlike crystalline Si solar cells, amorphous Si solar cells have a feature that power generation efficiency does not decrease even when the temperature rises. Therefore, more efficient power generation can be realized with the type in which the thermoelectric conversion module according to the present invention in which the substrate made of foam is incorporated is bonded to the back surface of the solar cell. Since any type of solar cell can be powered by the thermoelectric conversion module according to the present invention independently of the solar cell itself, the thermoelectric conversion module according to the present invention can be applied to any type of solar cell. Can be used.

  Next, in the power generation device according to the present invention, when the temperature of the surface side in contact with the solar cell in the thermoelectric conversion module is lower than the temperature of the surface side not in contact with the solar cell, the positive / negative of electricity is determined. It is preferable that the switch to switch is provided in the circuit of the thermoelectric conversion module. The reason for providing the switch is that the temperature on the surface side in contact with the solar cell is not necessarily a high temperature part, and depending on the outside air temperature or the way of installing the solar cell, it becomes a low temperature part and may generate a reverse voltage. Because there is. In this case, if the structure is switched between positive and negative with a switch, power generation is possible even at night without the sun. Therefore, it is preferable to provide a switch in the circuit that can automatically switch between positive and negative. In the present specification, unless otherwise specified, the bonding portion side with the back surface of the solar cell is described as a high temperature portion.

Examples of the present invention will be described in detail below with reference examples.
(Reference Example 1)
Assuming the thermoelectric conversion element having the structure shown in FIG. 10, each part uses the materials and elements described in Tables 1 and 2 and “the ratio of the sum of the cross-sectional areas of only the thermoelectric elements” to the “area of the entire thermoelectric conversion module”. We simulated the temperature difference between the plate electrodes and the amount of power generated by the thermoelectric conversion module. The result is shown in FIG.

  In FIG. 11, β = “the ratio of the sum of the cross-sectional areas of only the thermoelectric elements” to “the area of the entire thermoelectric conversion module”.

  It can be seen that the maximum output is shown around β = 0.015. The smaller the area ratio β indicated by the thermoelectric element, the smaller the heat flow flowing between the two thermal electrodes, so the temperature difference becomes larger, but the cross-sectional area becomes smaller, so the amount of power generation becomes smaller.

  From the thermal conductivity κt = 2 (W / mK) of the thermoelectric conversion element and the thermal conductivity κa = 0.03 (W / mK) of the heat insulating layer, β = St / Sa = κa / κt = 0.015.

  That is, it is understood that the maximum value is obtained at St · κt = Sa · κa.

（参考例２）
市販のペルチエ素子（小松エレクトロニクス社製：ＫＳＭ−０６１２７Ａ）に対して、硬質ウレタンフォーム（熱伝導度＝０．０１Ｗ／ｍＫ）を詰め込んだ。高温側を１２０℃に固定し、低温側は２０℃の大気に放熱した。熱電素子間が大気のままの場合と、ウレタンフォームを充填したときに、発電量の差を調べた。

(Reference Example 2)
A rigid urethane foam (thermal conductivity = 0.01 W / mK) was packed into a commercially available Peltier element (manufactured by Komatsu Electronics Co., Ltd .: KSM-06127A). The high temperature side was fixed at 120 ° C., and the low temperature side was radiated to the atmosphere at 20 ° C. The difference in the amount of power generation was examined when the thermoelectric elements remained in the atmosphere and when the urethane foam was filled.

  As shown in Table 3 below, filling the urethane foam increased the temperature difference between the upper and lower sides, and the power generation amount increased accordingly.

  In agreement with the above simulation results, it was confirmed that the amount of power generation increased when the non-thermoelectric element space between the plate electrodes was filled with a material having low thermal conductivity.

［実施例１］
熱電変換素子（小松エレクトロニクス社製：９Ａ−０６Ｌ０４）を分解してｐ型、ｎ型素子（いずれも２ｍｍ×２ｍｍ×３ｍｍ）を取り出した。

[Example 1]
A thermoelectric conversion element (manufactured by Komatsu Electronics Co., Ltd .: 9A-06L04) was disassembled to take out p-type and n-type elements (both 2 mm × 2 mm × 3 mm).

  Then, 16 pairs of p-type and n-type elements are used, and each side of the small section is 40 mm, 80 mm, 100 mm, and 120 mm square alumina substrates as shown in FIG. Elements were placed in series.

  Next, a thermoelectric element was sandwiched between two alumina substrates, and one of the thermoelectric conversion elements was attached with a heat sink of a copper block. Since the thermoelectric conversion element is a BiTe system, the thermal conductivity is about 1.5 W / mK. Between the thermoelectric conversion elements, urethane foam was filled. The thermal conductivity of urethane foam is 0.03 W / mK.

  One side of the alumina substrate was fixed to a copper block maintained at a constant value of 80 ° C. with an adhesive, the room temperature was kept at 25 ° C., and the amount of power generation at this time was measured. The results are shown in Table 4.

Ａ＝２０ｍｍのときが最大となった。

The maximum was when A = 20 mm.

This corresponds to a case where 8 mm ² × 1.5 W / mK (W / mK) = A2 × 0.03.

[Example 2]
The element (size = 2 mm × 2 mm × 3 mm thickness) was separated from the p-type and n-type BiTe thermoelectric element (manufactured by Komatsu Electronics: KSM-04127A).

  In the process shown in the manufacturing process diagram of FIG. 6, a copper foil (thickness of 30 μm) is attached to a polystyrene foam resin, and etching is performed so that the positional relationship shown in FIGS. 2 and 7 is obtained. A lower plate electrode was formed. The structure of the upper plate electrode and the lower plate electrode is such that the upper and lower plates form an angle of 45 degrees with each other, and a plurality of thermoelectric conversion elements are arranged in series with n-type-p-type-n-type-p type. Is formed.

  Thereafter, a plurality of 2 mm × 2 mm square through holes shown in FIG. 7 were formed by a punching method, a thermoelectric element material was embedded in these through holes, and soldered between the electrodes. 8 × 6 = 48 thermoelectric conversion elements were produced on a styrene resin having a size of about 100 mm × 100 mm. Finally, in order to ensure electrical insulation, it was filled with a thin heat conductive resin (manufactured by Nitto Shinko Co., Ltd .; silicone rubber).

  And the one electrode side of the obtained thermoelectric conversion module was adhere | attached on the hotplate surface using the heat conductive adhesive (Nissho Sangyo Co., Ltd. product: Silicone oil compound YG6240 for thermal radiation). In consideration of the attachment of the solar cell, the hot plate was tilted at an angle of 45 degrees and arranged so that the element faced downward.

  FIG. 7 shows a configuration of a thermoelectric element in which a pair of p-type and n-type elements are arranged in an area of about 10 mm × 15 mm. The thermal conductivity (κt) of the thermoelectric element is about 1.5 W / mK, and the thermal conductivity (κa) of the expanded polystyrene resin is about 0.07 W / mK.

  The temperature of the hot plate surface and the element surface was measured with a thermocouple. The hot plate temperature was adjusted to about 80 ° C. The atmospheric temperature was adjusted to about 30 ° C.

  In the case of the arrangement of FIG. 7, the surface temperature of the element was about 64 ° C., and the temperature difference was 16 ° C.

The voltage across the 48 pairs of heat conversion elements was 6.1 mV, and the current was 24 mA. From this, the power generation amount when converted to 1 m ² is 15 W.

  When the thermoelectric conversion element was produced in the same process as described above while changing the interval at which the thermoelectric element was arranged, the results shown in Table 5 below were obtained.

これより、Ｓａ×κａ＝Sｔ×κｔのとき最大となり、それからずれると温度差が小さくなり、出力が下がることが確認された。

From this, it was confirmed that the maximum value was obtained when Sa × κa = St × κt, and that the temperature difference became smaller and the output decreased when deviating from that.

  According to the thermoelectric conversion module according to the present invention, since a large temperature difference is realized in the thermoelectric conversion module, it is possible to increase and improve the amount of power generation, and by adhering to the back side of the solar cell, It is possible to increase the effective power generation efficiency of the battery. Therefore, the thermoelectric conversion module according to the present invention has industrial applicability to be used by being incorporated in a solar cell.

Sectional drawing which shows the principal part structure of the thermoelectric conversion element which concerns on a prior art. The schematic perspective view of the thermoelectric conversion module which concerns on this invention. The schematic perspective view of the thermoelectric conversion module which concerns on the modification of this invention. The schematic of the heat flow in the thermoelectric conversion module in which the p-type thermoelectric conversion element and the n-type thermoelectric conversion element are arrange | positioned substantially perpendicularly between a pair of electrode plates. The schematic diagram of the heat flow in a thermoelectric conversion module in case a p-type thermoelectric conversion element and an n-type thermoelectric conversion element are arrange | positioned substantially perpendicularly between a pair of electrode plates, and there exists a fixed heat inflow on the one electrode plate side. Explanatory drawing which shows the manufacturing process of the thermoelectric conversion module which concerns on Example 2. FIG. The schematic plan view of the thermoelectric conversion module which concerns on this invention shown in FIG. The graph which compared the performance of various heat insulation materials. The graph which shows the relationship between the thermal conductivity of the heat insulation layer (non-thermoelectric element space) in a thermoelectric conversion module, the temperature difference between an upper and lower electrode, and electric power generation amount. Explanatory drawing which shows the structure of the thermoelectric conversion element which concerns on the reference example 1. FIG. The graph which shows the relationship between the temperature difference between plate-shaped electrodes when the "ratio of the sum of the cross-sectional areas of only a thermoelectric element" with respect to "the area of the whole thermoelectric conversion module" in the reference example 1 and the electric power generation amount of a thermoelectric conversion module . FIG. 3 is a plan view of an alumina substrate on which a plurality of upper or lower plate electrodes of the thermoelectric conversion module according to the first embodiment are formed.

Explanation of symbols

200 Thermoelectric Conversion Module 201 Foam Substrate 202 Upper Plate Electrode 203 Lower Plate Electrode 204 Through Hole 205 n-Type Thermoelectric Conversion Element 206 p-Type Thermoelectric Conversion Element 300 Thermoelectric Conversion Module 301 Foam Substrate 302 Upper Plate Electrode 303 Lower plate electrode 304 Through hole 305 n-type thermoelectric conversion element 306 p-type thermoelectric conversion element

Claims (10)

  A substrate made of foam, a plurality of upper plate-like electrodes provided on the upper surface side of the substrate and not electrically connected to each other, and a plurality of lower plate-like electrodes provided on the lower surface side of the substrate and not electrically connected to each other Embedded in the electrode, a plurality of through holes provided in the region where the upper plate electrode and the lower plate electrode of the substrate overlap or in the vicinity region, and one through hole provided in or near each plate electrode An n-type thermoelectric conversion element made of an n-type material and a p-type thermoelectric conversion element made of a p-type material embedded in the other through-hole provided in or near each plate-like electrode, Alternatively, each end side of a pair of n-type thermoelectric conversion element and p-type thermoelectric conversion element provided in the vicinity is electrically connected to the corresponding upper plate electrode and lower plate electrode, respectively. Multiple sets of p-type thermoelectrics The conversion element and the n-type thermoelectric conversion element are arranged in series, and the upper plate electrode or the lower plate electrode side is arranged on the high temperature side, and the other electrode side is arranged on the low temperature side. module. The p-type thermoelectric conversion element and the n-type thermoelectric conversion element have thermal conductivity κp and κn, respectively, and the p-type thermoelectric conversion element and the n-type thermoelectric conversion element have cross-sectional areas Sp and Sn, respectively. When the thermal conductivity of the region where the p-type thermoelectric conversion element and the n-type thermoelectric conversion element are not embedded is κo and the cross-sectional area of the region is So,
1.2 × (κp · Sp + κn · Sn) ≧ κo × So (Formula 1)
And having the relationship
0.8 × (κp · Sp + κn · Sn) ≦ κo × So (Formula 2)
The thermoelectric conversion module according to claim 1, wherein:   A plurality of thermoelectric conversion modules according to claim 1 or 2 are stacked via an electrical insulating layer, and the plate electrode side of one thermoelectric conversion module located on the outermost side is disposed on the high temperature side and located on the outermost side. The thermoelectric conversion module, wherein the plate-like electrode side of the other thermoelectric conversion module is disposed on the low temperature side. The thermoelectric conversion module according to any one of claims 1 to 3, wherein the plate-like electrode side of the thermoelectric conversion module disposed on the high temperature side or the low temperature side is an air radiation type.
Thermoelectric element   The thermoelectric conversion module according to any one of claims 1 to 4, wherein the substrate made of foam has a thermal conductivity of 0.03 W / mK or less.   The thermoelectric conversion module according to claim 5, wherein the foam material constituting the substrate is at least one selected from expanded polystyrene, polystyrene foam, urethane foam, phenol foam, and glass wool.   A thermoelectric conversion module according to any one of claims 1 to 6 is adhered to a back surface side of a solar cell, and a power generation device is configured to generate power with a temperature difference between the solar cell and outside air.   When the thermal conductivity of the adhesive used for bonding the solar cell and the thermoelectric conversion module is (W / mK) and the thickness of the adhesive is (d), the ratio of (W / mK) / (d) is 1000 or more. The power generator according to claim 7, wherein the power generator is provided.   The power generator according to claim 7, wherein the solar cell is an amorphous Si solar cell.   When the temperature on the surface side in contact with the solar cell in the thermoelectric conversion module is lower than the temperature on the surface side not in contact with the solar cell, a switch that switches between positive and negative of electricity is provided in the circuit of the thermoelectric conversion module The power generator according to claim 7, wherein the power generator is provided.

Images