JPH0992889A - Seebeck element - Google Patents

Abstract

(57) [PROBLEMS] To provide a Seebeck element which is a conductive material which can be mass-produced and which can supply a large electric power with a large electromotive force. SOLUTION: A conductor is made by joining two conductors made of different conductive materials at two points to form a circuit, and the two joints are held at different temperatures from each other, and the different terminals are provided between the terminals of the open circuit. In a Seebeck element that generates an open-circuit voltage according to a temperature difference, one of the two different conductive materials is Fe and the other material is wt%.
Is used as Fe containing silicon in the range of 4.0 to 6.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a functional element that converts natural energy such as air, water, seawater, and geothermal heat having a temperature difference into electric energy.

[0002]

2. Description of the Related Art A circuit is made by joining conductors made of two different conductive materials a and b as shown in FIG. 1, and the two joints are made to have different temperatures T _H and T _L (T _H >T> T). _L )
, The temperature difference between the terminals of the open circuit ΔT = T _H −T _L
The phenomenon in which the open circuit voltage V _ab is generated according to is called Seebeck effect. Also, the change α _{ab of} V _ab with respect to the change of the temperature of one junction by 1 ° C. is referred to as the Seebeck coefficient of the substance b with respect to the substance a.

Conventionally, as a combination of substances a and b capable of obtaining a large open circuit voltage, alumel-chromel, copper-constantan, chromel-constantan, etc. are known. These alloy components are 90% Ni-8 for Alumel.
% Al-2% Mn, chromel 90% Ni-10% C
r and constantan were 40% Ni-60% Cu, etc., and both were characterized by containing nickel at a high concentration (% described here means% by weight, and the following description has the same meaning). Is).

[0004]

The value of the open circuit voltage V _{ab in} FIG. 1 is a function of the temperature difference ΔT, and if there is a temperature difference between the two junctions even at a low temperature near room temperature of 100 ° C. or less, the electrical energy is reduced. Can occur. However, in order to generate a large amount of power according to this principle, a large amount of the above-mentioned alloys is required, so the use of these alloys containing extremely expensive nickel at a high concentration was not economically practical. .

Therefore, the present applicant has found that an iron-based alloy exhibiting a good Seebeck effect in combination with iron that is inexpensively produced in large quantities, is rich in additional elements in terms of resources, and can be added in small amounts. As a result of diligent research on alloys having an effect, Fe-S containing 4.0 to 6.0% of silicon of the present invention.
i alloy was developed.

It is an object of the present invention that the electromotive force obtained by joining iron is at least 3 times the electromotive force obtained by joining chromel-constantan under the same temperature and temperature difference.
It is intended to provide a Seebeck element based on iron, which is one-third or more and which can easily obtain high power.

[0007]

In order to achieve this object, the Seebeck element according to the present invention forms a circuit by joining conductors made of two different conductive materials to each other at two points, and joining the two. In the Seebeck element that holds the parts at different temperatures and generates an open circuit voltage between terminals of the open circuit according to the temperature difference of the different temperatures, one of the two different conductive materials is Fe.
And the other material is silicon in an amount of 4.0 to 6.
It is a Fe-Si alloy containing 0%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In a Fe-Si alloy, a Fe-Si solid solution having a saturation solubility of Si of 18.5% and FeSi,
Although there are intermediate compounds such as FeSi ₂ , the alloy of the present invention is F
It is an e-Si solid solution. The addition of silicon reduces the plasticity of iron and increases its hardness. Further, the temperature of the allotropic transformation increases with the increase of Si, and the transformation disappears when the Si content is about 3% or more. Therefore, the annealing temperature is increased to increase the size of crystal grains, thereby reducing the hysteresis loss and increasing the magnetic permeability at a low magnetic flux density. . Regarding the electric resistance, if Si increases by 1%, the electric resistivity of iron increases by about 10 μΩ · cm.

The Seebeck effect power generation, which obtains industrial electric power from a small temperature difference existing in the temperature range of the living sphere including a temperature of 0 ° C. or less, has extremely low energy conversion efficiency, but has no mechanical driving part. This is a direct conversion method to electric power by an extremely simple device that does not exist. Furthermore, renewable energy is permanent, and from the viewpoint of global environmental conservation, industry,
It is significant as a means of producing household electric power. The main requirements for an energy conversion material to achieve this are that it has good conductivity at temperatures near room temperature, that it has a good Seebeck effect, that it has abundant resources and that it can be manufactured at low cost, and that it has good workability. There are things like that. From the above requirements, the materials are limited to metals and alloys, and because of the problem of quantity, that is, iron other than iron, it is necessary to develop an alloy that satisfies the following conditions.

[0010]

Embodiments of the present invention will be described more specifically below with reference to the accompanying drawings. The Seebeck coefficient of iron is approximately constant at +16 μV / K in the temperature range of −30 ° C. to 100 ° C. In order to increase the generated voltage of the circuit of FIG. 1, if one substance is iron, the Seebeck coefficient of the other substance must have a large positive value or have a large negative value. . A substance having a positive Seebeck coefficient is called a p-type and a substance having a negative Seebeck coefficient is called an n-type. Iron is p
Since it is a type conductor, an n-type conductor is required as a partner to be joined to iron, economical silicon is selected as an element for converting iron to n-type, and a Fe-Si alloy is produced to measure the Seebeck coefficient. Was carried out.

Iron having a purity of 99.9% was melted together with silicon having a purity of 99.8% by high frequency induction heating in an argon atmosphere to produce 200 g of a homogeneous Fe-Si alloy. The composition range of Si in the alloy was 0 to 10% by weight. FIG. 2 shows the measurement results, and at 5.5% Si, the Seebeck coefficient is negative and has a minimum value of −9.3 μV / K. Therefore, when a Fe-Si alloy having this composition is selected and joined to iron to form a circuit, the maximum voltage is generated. This voltage produces a high open circuit voltage due to the temperature difference between the two junctions being 25.3 μV per 1 ° C.

The upper limit of the silicon concentration is 6.0%. This is determined because if the content exceeds 5.5%, the Seebeck voltage is decreased due to bonding with iron, and the conductivity is also decreased, resulting in a decrease in output. On the other hand,
The lower limit of silicon concentration is as the silicon concentration decreases,
The conductivity increases but the Seebeck voltage decreases, so
As a result, the output is reduced, so it was decided to be 4.0%.

Regarding the purity of iron, light elements such as carbon, nitrogen, oxygen, sulfur, and phosphorus, which are usually contained in ordinary steel in an amount of 0.2% or less, and trace amounts of metal elements, are almost in the Seebeck voltage. It is known to have no effect.

[Table 1]

As an example, Table 1 compares the Seebeck coefficient of iron-5.5% silicon iron with a conventionally known metal-alloy pair. As is apparent from the table, the Seebeck coefficient of the iron of the present invention-5.5% silicon iron pair is different from that of other metals-
Although inferior to the alloy pair, it is essentially all iron except 5.5% Si and does not require expensive additional elements. From the viewpoint of economical mass production, the industrial value of the present invention is considered to be great.

A DC generator is generally considered as a product utilizing the ability to directly convert heat into electric energy using the alloy according to the present invention. Based on its power generation characteristics, commercial power generators such as geothermal generators, ocean temperature difference generators, waste heat utilization generators, solar heat utilization generators, nuclear waste heat utilization generators, nuclear fission heat direct utilization generators, garbage generators, etc. It is suitable to use as a power source, private power source, remote power source, and emergency power source.

[0016]

As apparent from what has been described above, according to the present invention, it is possible to provide a Seebeck element that can obtain a good Seebeck electromotive force in combination with iron that is inexpensive and mass-produced. Therefore, it is possible to provide a high power Seebeck element, and it is possible to realize an element expected as an industrial or household power production means.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of a Seebeck element.

FIG. 2 is a graph showing the relationship between the Si concentration and the Seebeck coefficient of a Fe · Fe—Si alloy Seebeck element.

Claims (1)

[Claims] 1. A circuit is formed by joining conductors made of two different conductive materials at two points to each other, and the two joints are held at different temperatures from each other. In a Seebeck element that generates an open-circuit voltage according to a temperature difference between different temperatures, one of the two different conductive materials is Fe, and the other material is wt%.
Fe containing 4.0 to 6.0% of silicon by
Seebeck element characterized by being an alloy.