This application claims the priority of Korean Patent Application No. 2009-0031784 filed on Apr. 13, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a thermoelectric element having improved stability and thermoelectric efficiency.
2. Description of the Related Art
Due to rapid increase in the use of fossil fuel energy, there are concerns about global warming and the exhaustion of existing energy supplies. This has stimulated interest in the thermoelectric (TE) element. The TE element is used as a cooling device substitute for freon gas or the like which contribute to air pollution. Also, it is used extensively as a small generator utilizing the Seebeck effect. Particularly, when a loop is formed by which metals are grounded to each other by the medium of a semiconductor (a TE semiconductor) and a current is passed through the loop, a potential difference is generated by a Fermi energy difference. At this time, electrons take energy necessary to move from one metal surface to another metal surface, resulting in a cooling effect (heat absorption). In contrast, energy equivalent to the energy the electrons bring is taken out in another metal surface, resulting in a heating effect (heat emission). This is the so called Peltier effect, which is a principle of operating a cooling device by the use of the TE element. Here, a position of the heat absorption and the heat emission is determined based on types of semiconductor and directions of current flow, and variations in semiconductor materials lead to different effects.
An aspect of the present invention provides a thermoelectric (TE) element having improved stability and thermoelectric efficiency in that even in the case that a section of components does not operate electrically, the operation of the entire element is not adversely affected.
According to an aspect of the present invention, there is provided a TE element including a plurality of pn junctions each formed by bonding an n-type TE semiconductor and a p-type TE semiconductor with a metallic layer interposed therebetween, and a first electrode and a second electrode electrically connected to the n-type TE semiconductor and the p-type TE semiconductor, respectively. The plurality of pn junctions are laminated with insulating layers interposed therebetween, and are connected electrically in parallel to each other.
The n-type and p-type TE semiconductors of at least one of the plurality of pn junctions may be formed of materials having thermal conductivity different from that of another pn junction.
In this case, the thermal conductivity in the materials of the n-type and p-type TE semiconductors may increase from an upper part to a lower part with respect to the lamination direction of the plurality of pn junctions.
The lamination direction of the plurality of pn junctions may be identical to the direction of heat flow in the TE element.
The metallic layer may be formed of the same material as the first and second electrodes.
The first electrode may be a common electrode for the n-type TE semiconductor in each of the plurality of pn junctions.
The second electrode may be a common electrode for the p-type TE semiconductor in each of the plurality of pn junctions.
The first and second electrodes may be arranged in a lateral direction of a structure including the plurality of pn junctions.
In this case, the first and second electrodes may be arranged to face each other.
The n-type and p-type TE semiconductors may contact the first and second electrodes, respectively, and be arranged to be spaced apart from the second and first electrodes, respectively.
In this case, the TE element may further include insulating materials that are formed between the n-type TE semiconductor and the second electrode and between the p-type TE semiconductor and the first electrode, respectively.
The TE element may further include a ceramic layer and a heat absorbing layer successively formed on an upper surface of a pn junction positioned at the top of the plurality of pn junctions with respect to the lamination direction of the plurality of pn junctions.
In this case, a ceramic material included in the ceramic layer may be alumina.
The TE element may further include a heat sink formed on a lower surface of a pn junction positioned at the bottom of the plurality of pn junctions with respect to the lamination direction of the plurality of pn junctions.
The TE element may further include a power source connected to the first and second electrodes to form a circuit. The power source allows current to flow through the plurality of pn junctions so that heat absorbed from one side of the plurality of pn junctions is transferred along the lamination direction of the plurality of pn junctions.
The TE element may further include a resistance device connected to the first and second electrodes to form a circuit. In this case, current may flow through the plurality of pn junctions and the resistance device by heat absorbed from one side of the plurality of pn junctions.
The insulating layers may be formed of a ceramic material.
The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the shapes and dimensions may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like components.
The n-type and p-type TE semiconductors 101 and 102 may use materials typically used in this technical field and suitably doped, for example, TE materials such as BiTe-based materials and PbTe-based materials. The metallic layer 103 may use materials having a high electrical conductivity such as copper so that current flows smoothly. The TE element 100 may be used as a TE cooler by allowing for heat transfer from one side to the other side in accordance with current flow that is generated when voltage is applied to the n-type and p-type TE semiconductors 101 and 102. Also, current may be generated by the use of energy that is generated by making the temperature of one side different from that of the other side in a structure having the n-type and p-type TE semiconductors 101 and 102.
The n-type TE semiconductor 101, the metallic layer 103, and the p-type TE semiconductor 102 are involved in a single unit structure performing a TE function, which is hereinafter referred to as a “pn junction”. There are provided a plurality of pn junctions to be laminated. In this embodiment, one pn junction is connected electrically in parallel to another pn junction, which is different from pn junctions that are connected in series according to the related art.
As described above, the TE element 100 is able to absorb heat at one side and emit the heat to the other side by a structure in which the pn junctions are laminated (hereinafter referred to as “laminate structure”). In the laminate structure, the heat absorbing layer 108 and the heat sink 110 are suitably bonded, thereby being capable of performing the TE function. According to the laminate structure with reference to
Also, as described in the exemplary embodiment, the pn junctions are laminated in one direction, thereby inducing heat flow in the lamination direction of the pn junctions. That is, in the case that the n-type and p-type TE semiconductors 101 and 102 are connected to a positive electrode and a negative electrode, respectively, the current flow allows the heat of the heat absorbing layer 108 to pass through the pn junctions and be emitted to the heat sink 110. In this exemplary embodiment, the pn junctions are connected thermally in series and electrically in parallel. This reverses the connection in the TE element according to the related art, in which the pn junctions are connected thermally in parallel and electrically in series.
In the TE element having the laminate structure according to that exemplary embodiment, considering that the heat flow is induced in the lamination direction, the n-type and p-type TE semiconductors 101 and 102 may be formed of different materials according to lamination directions. Specifically, in the case that a pn junction positioned at a high temperature part, relative to a pn junction positioned at a low temperature part, is formed of TE materials for relatively high temperature, for example, relatively low thermal conductive materials, enhanced TE performance can be achieved. That is, with reference to
As described above, in the case that the pn junctions are laminated by different thermal conductivity, temperature is distributed to have different temperature gradients from the high temperature part to the low temperature part in the laminate structure. In contrast, the TE element according to the related art shows nearly constant temperature gradients from the high temperature part to the low temperature part. As a result of comparing parallel connection design (laminate structure wherein the pn junctions are laminated by different thermal conductivity) with series connection design (structure illustrated in
Meanwhile, the first and second electrodes 105 and 106 may contact the n-type and p-type TE semiconductors 101 and 102, respectively, and be formed of the same material as the metallic layer 103. In this case, in order to acquire an efficient contact structure, the first and second electrodes 105 and 106 may be arranged in a lateral direction of the laminate structure of the pn-junctions and face each other. The first electrode 105 and the p-type TE semiconductor 102 are spaced apart from each other, not to contact each other. Likewise, the second electrode 106 and the n-type TE semiconductor 101 are spaced apart from each other, not to contact each other. In this case, as illustrated in
According to the exemplary embodiments of the present invention, even in the case that a section of components does not operate electrically, the operation of the entire element is not adversely affected, thereby being able to improve stability of the TE element.
Furthermore, the TE element according to the exemplary embodiments of the present invention is able to reduce dependence on the applied voltage and enhance the TE efficiency more than before.
While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.
Number | Date | Country | Kind |
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10-2009-0031784 | Apr 2009 | KR | national |