JP2009272327A - Thermoelectric conversion system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve energy saving by highly efficiently generating power while recovering exhausted heat of ≤300°C which is not utilized but exhausted in a factory or a power plant. <P>SOLUTION: The thermoelectric conversion system includes: a thermoelectric conversion module 1 capable of alternately converting thermal energy and electric energy; a heat source 2 for heating a high-temperature side surface of the thermoelectric conversion module 1; a cooling source for cooling a low-temperature side surface of the thermoelectric conversion module 1; a cooling device 3 for cooling a low-temperature side surface of the thermoelectric conversion module by performing heat exchange between the cooling source for cooling the low-temperature side surface of the thermoelectric conversion module and the thermoelectric module 1; a high heat conductive material 4 for assisting heat conduction between the heat source 2 and the thermoelectric conversion module 1 and between the cooling device 3 and the thermoelectric conversion module 1; and a heat insulating material 5 provided on the surrounding portion except the heat source 2 and the cooling device 3 and used to minimize the heat radiation to the outside. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermoelectric conversion system that contributes to efficient power generation and energy saving by utilizing exhaust heat generated from a factory, a power plant, or high-temperature equipment.

  A thermoelectric conversion module generally has a structure in which a P-type element (P-type semiconductor) and an N-type element (N-type semiconductor) are sandwiched between ceramic substrates (insulating plates) via electrodes.

  The P-type element and the N-type element are alternately joined through electrodes made of a metal member, thereby forming a PN element pair (PN semiconductor pair) of the P-type element and the N-type element. And as the whole thermoelectric conversion module, many PN element pairs are connected, and a lead wire is connected to the start point and end point of a PN element pair.

  In the thermoelectric conversion module configured as described above, one of the two ceramic substrates (hereinafter referred to as a low temperature end surface) is cooled with cooling water or the like, and the other one (hereinafter referred to as a high temperature end surface) is cooled. When heat is applied, an electromotive force is generated between the low temperature side electrode and the high temperature side electrode, and a current flows. That is, electric power can be taken out from the thermoelectric conversion module by constructing the thermoelectric conversion system so as to give a temperature difference to both sides of the thermoelectric conversion module.

Conventionally, as this type of thermoelectric conversion system, an in-vehicle exhaust heat power generation device (Patent Document 1) that uses a thermoelectric conversion module to recover exhaust heat of exhaust gas discharged from an automobile engine or the like and convert it into electric power is disclosed. There is a thermoelectric conversion device for a furnace wall (Patent Document 2) that generates power by attaching a thermoelectric conversion module to a furnace wall of a high temperature furnace such as an incinerator or a melting furnace.
Japanese Patent No. 3564274 Japanese Patent Application No. 10-190073

  However, in in-vehicle exhaust heat power generation devices that use exhaust heat of exhaust gas and furnace wall thermoelectric conversion devices that use the furnace wall temperature of high-temperature furnaces such as incinerators and melting furnaces, the exhaust received by the high-temperature end face of the thermoelectric conversion module is received. Since the temperature of the heat is a high temperature of 500 ° C. to 1000 ° C., the temperature gradient between the high temperature end surface and the low temperature end surface of the thermoelectric conversion module can be increased, but the target heat is unused heat whose exhaust heat temperature is relatively low. In this case, there is a problem that it is difficult to obtain a large temperature gradient between the high temperature end surface and the low temperature end surface of the thermoelectric conversion module.

  The present invention has been made in view of the above circumstances, and allows a large temperature gradient between the high temperature end surface and the low temperature end surface of the thermoelectric conversion module to be used in a factory or a power plant. An object of the present invention is to provide a thermoelectric conversion system that can efficiently collect power by collecting waste heat that has been discarded, and can save energy.

  In order to achieve the above object, the present invention provides a thermoelectric conversion module capable of mutually converting heat energy and electric energy, a heat source for heating a high temperature side surface of the thermoelectric conversion module, a cooling source, the cooling source, A cooling device that performs heat exchange with the thermoelectric conversion module to cool a low temperature side surface of the thermoelectric conversion module, between the heat source and the thermoelectric conversion module, and between the cooling device and the thermoelectric conversion module A highly thermally conductive material that assists heat conduction, and a heat insulating material that is provided around the heat source and the cooling device except for minimizing heat radiation to the outside.

  The present invention also provides a thermoelectric conversion module capable of mutually converting heat energy and electric energy, a heat source for heating a high temperature side surface of the thermoelectric conversion module, and heat exchange between the heat source and the thermoelectric conversion module. A heating device, a cooling source that cools a low-temperature side surface of the thermoelectric conversion module, a cooling device that performs heat exchange between the cooling source and the thermoelectric conversion module, and between the heating device and the thermoelectric conversion module, And a high thermal conductivity material that assists in heat conduction between the cooling device and the thermoelectric conversion module, and the heat source, the cooling source, the heating device, and a peripheral portion excluding the cooling device to minimize heat radiation to the outside. And a heat insulating material.

  Furthermore, the present invention provides a thermoelectric conversion module capable of mutually converting heat energy and electric energy, a cooling device in which a low temperature side surface of the thermoelectric conversion module is cooled by a cooling source, a high temperature side surface and a heat source of the thermoelectric conversion module, Between the low temperature side of the thermoelectric conversion module and the cooling device, and a high thermal conductivity material that assists heat conduction between the low temperature side surface and the cooling device. And a heat insulating material.

  The present invention also provides a thermoelectric conversion module capable of mutually converting heat energy and electric energy, a cooling device in which a low temperature side surface of the thermoelectric conversion module is cooled by a cooling source, and a high temperature side surface side of the thermoelectric conversion module by a heat source. A heating device to be heated; a high thermal conductivity material that assists heat conduction between the hot side of the thermoelectric conversion module and the heating device; and between the cold side of the thermoelectric conversion module and the cooling device; and the heating It is provided in the peripheral part except a device and the said cooling device, and is provided with the heat insulating material for minimizing the thermal radiation to the exterior.

  According to the present invention, by taking a large temperature gradient between the high-temperature end face and the low-temperature end face of the thermoelectric conversion module, the relatively low-temperature exhaust heat that is discarded without being used in factories or power plants can be recovered. Energy can be generated efficiently and energy saving can be realized.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view of an overall configuration showing a first embodiment of a thermoelectric conversion system according to the present invention.

  The thermoelectric conversion system of the present embodiment performs thermoelectric conversion by exchanging heat between the thermoelectric conversion module 1, the heat source 2 that heats the high temperature side surface of the thermoelectric conversion module 1, and a cooling source (not shown) and the thermoelectric conversion module 1. A cooling device 3 that cools a low-temperature side of the module 1, a high thermal conductivity material 4 that assists heat conduction between the heat source 2 and the thermoelectric conversion module 1, and between the cooling device 3 and the thermoelectric conversion module 1, and a heat source 2 and a heat insulating material 5 for minimizing heat radiation to the outside.

  The thermoelectric conversion module 1 is fixed to a wall surface of the heat source 2 by a fixing means such as a fixing bolt (not shown) so as to be sandwiched between the heat source 2 and the cooling device 3.

  In this case, as the heat source 2, one that recovers unused waste heat from various plants (geothermal (hot spring), factory, power plant, waste treatment plant) is used, and the temperature is equal to or lower than the heat-resistant temperature of the thermoelectric conversion module 1. Any number of times is acceptable.

  Further, the sandwich structure of the heat source 2 -thermoelectric conversion module 1 -cooling device 3 is fastened with a high pressure by a fixture such as a bolt or screw, and between the thermoelectric conversion module 1 and the heat source 2 and between the cooling device 3 and the thermoelectric conversion module. The thermal resistance between 1 and 1 is made small. The surface pressure at this time is preferably 1 MPa or more and the bottom surface of the cooling device is not deformed.

  Further, each joint surface of the heat source 2 -thermoelectric conversion module 1 -cooling device 3 is made flat and high thermal conductivity grease or the like is inserted between them so that the thermal resistance at the joint surface is as small as possible. It is trying to become.

  As the thermoelectric conversion module 1 described above, there are a case where the electrode surface is covered with an insulating high heat conductive material such as alumina and a case where the electrode surface is exposed, but the electrode surface is exposed. In this case, as shown in the drawing, the electrode surfaces are arranged by disposing a thin plate such as alumina (Al) or aluminum nitride (AlN) as the high thermal conductive material 4 on the high and low temperature electrode surfaces of the thermoelectric conversion module 1. Insulating cover.

  In these joints, grease with high thermal conductivity is often used. As this grease, there are silicon-based grease and non-silicon-based grease. Especially, non-silicon-based grease has (1) high thermal conductivity and excellent heat dissipation characteristics, (2) low bleed, Excellent long-term stability, (3) Siloxane-free, less prone to migration, (4) Stable at high temperatures, low outgassing, (5) Wide operating temperature range (-55 ° C to 350 ° C) There is a merit.

  Further, the cooling device 3 for cooling the low temperature side surface of the thermoelectric conversion module 1 has a plurality of flat plate rectangular fins 3b vertically spaced at equal intervals on the upper surface of a fin base 3a made of alumina (Al) or the like as shown in FIG. This is a structure to be arranged.

  Here, when the fin pitch Pf and the fin plate thickness t are adjusted under the condition that the area of the fin base 3a (vertical width Wf × horizontal width Lb) and the fin height L are constant, fin efficiency as shown in FIG. 3 is obtained. . Therefore, heat exchange can be efficiently performed by designing the cooling device 3 so that the fin pitch Pf is 1 to 3 times the fin plate thickness t.

  At this time, when the vertical width and horizontal width of the fin base 3a of the cooling device 3 are set to integral multiples of the sum of the thermoelectric conversion module dimensions and the stop dimensions, respectively, the effective power generation area is maximized and the power generation efficiency is improved. The size of the thermoelectric conversion module is, for example, 60 mm × 60 mm as a basic size, and a plurality of thermoelectric conversion modules are connected in accordance with the mounting area of the heat source on the wall surface. For example, when six thermoelectric conversion modules (60 mm × 60 mm) are arranged in three rows in the horizontal direction and in two stages in the vertical direction, the dimensions of these thermoelectric conversion modules are 10 mm, 20 mm, 20 mm, If 10 mm, 10 mm, 20 mm, and 10 mm in the vertical direction, the fin base 3a of the cooling device 3 has a horizontal width of 240 mm and a vertical width of 160 mm, and the effective power generation area is maximized.

  Next, in the cooling device (flat rectangular fin) 3 in the case of forced air cooling, when the fin height is adjusted from 1 mm to 150 mm, the efficiency and output of the thermoelectric conversion system tend to be almost saturated at 120 mm or more as shown in FIG. Is seen. Therefore, a fin height of 120 mm is sufficient.

  Thus, in the first embodiment of the present invention, a plurality of flat rectangular fins 3b having a fin height of 120 mm are vertically arranged on the upper surface of the fin base 3a so that the fin pitch Pf is 1 to 3 times the fin plate thickness t. The temperature between the high temperature side surface and the low temperature side surface of the thermoelectric conversion module 1 by cooling the low temperature side surface of the thermoelectric conversion module 1 by forced air cooling flowing in from an external cooling source using the cooling device 3 having the structure arranged in FIG. Since the gradient can be increased, it is possible to efficiently generate power and contribute to energy saving.

  Next, a second embodiment of the present invention will be described.

  In the second embodiment, the cooling device is configured to cover the outside of the cooling device with a duct, and the cooling medium is passed from the cooling source to cool the low-temperature side surface of the thermoelectric conversion module. This is the same as the first embodiment.

  In this case, the duct is provided in close contact with the periphery and the tip of the cooling device. Further, the duct includes an intake (water) port at an end opposite to a connection end with the exhaust (water) port. For example, if a flat plate rectangular fin made of aluminum and a base plate having a thickness of, for example, 10 mm is used, if the surface pressure is 1 MPa to 1.5 MPa, the heat source wall surface of the SS400 steel having a thickness of 10 to 15 mm and the thermoelectric conversion module And the adhesion between the thermoelectric conversion module and the flat rectangular fin are the best, and the thermal resistance at each junction can be minimized.

  In this thermoelectric conversion module, the duct of the cooling source part for sending wind and refrigerant to the flat rectangular fins is made of a material having a thermal conductivity equal to or higher than that of the flat rectangular fins. For this reason, the heat from the heat source is also transmitted to the duct covering the flat rectangular fins.

  Therefore, if the thermal resistance with the duct is low or the duct has a high thermal conductivity, the heat that has passed through the thermoelectric conversion module can be released from the duct, and the power generation performance of the thermoelectric conversion system is improved. In this case, the surfaces of the thermoelectric conversion module and the base plate of the flat rectangular fin facing each other have the same shape, but the area of the base plate is preferably slightly larger than that of the thermoelectric conversion module. .

  In the above, the outside of the cooling device is covered with a duct, but the cooling device itself may be formed in a duct shape. If it does in this way, a refrigerant can be efficiently poured into a cooling device.

  Next, when considering the type of cooling source for cooling the cooling device 3, forced air cooling when the fin height of the flat rectangular fin 3b is 120 mm and forced water cooling when the fin height is several mm to 10 mm. The system efficiency of the latter is about 20% higher than that of the former. Therefore, the use of water or seawater as the cooling source makes it possible to reduce the height of the fins, and the system can be downsized (reduced in size and weight) and reduced in cost.

  Considering the practical aspect of this thermoelectric conversion system, it is optimal to install it in a plant in which a cooling source is prepared in advance as a pair with a heat source. In this case, it is realistic to use the cooling source by diverting a cooling system originally used as a cooling medium in a factory or a power plant. Further, seawater may be circulated as a cooling source.

  Furthermore, if the alternative chlorofluorocarbon (R134a) is circulated as a cooling source to cool the cooling device 3, as shown in FIG. 5, when the fin height is 7 mm or more under the condition of a constant flow rate, the cooling water is used. The pressure loss of the cooling device can be kept low. In this case, since the outside of the cooling device is covered with the duct so that there is no leakage of the refrigerant, the refrigerant can flow efficiently to the cooling device.

  In the first and second embodiments, the cooling device 3 having a structure in which a plurality of flat rectangular fins 3b are vertically arranged on the upper surface of the fin base 3a so that the fin pitch Pf is 1 to 3 times the fin plate thickness t. However, a cooling device having cooling fins having the following shapes may be used.

  FIGS. 6A to 6F show fins having different shapes constituting the cooling device. FIG. 6 (a) is a corrugated flat rectangular fin, which is the most common and easy to process fin that is bent to form a duct having a plurality of rectangular sections.

  FIG. 6B shows a cooling fin that is bent so that a plurality of ducts having a triangular cross section are formed. This cooling fin is equivalent to the fin plate corresponding to the diagonal line than in FIG. Since the fin density is high, the cooling performance is improved, but the pressure loss is also increased.

  FIG. 6C shows a corrugated fin formed by bending so as to form a plurality of corrugated ducts, FIG. 6D shows an offset fin, and FIG. 6E shows a louver fin. While expanding, it gives a turbulent flow effect to the refrigerant flow in the fin and improves the cooling performance of the fin.

  FIG. 6F shows a perforated fin, and this fin has an effect that the cooling performance is supplemented by a turbulent flow effect and the fin is reduced in weight because the surface area is reduced.

  In addition, the cooling device can be replaced with a microchannel having a channel representative diameter of 1 mm or less.

  7-9 is a figure for demonstrating the difference in the performance of the thermoelectric conversion system by the difference in the shape of a cooling device, respectively.

  As a result of adopting these cooling fins, the system efficiency and system output are ranked as “offset fin”> “louver fin” = “corrugated flat rectangular fin”> “perforate fin”.

  However, as can be seen from FIG. 7 and FIG. 8, the system efficiency cannot be significantly increased with forced air cooling. Therefore, when the coolant was changed to water, it was found that even if the fin height is 1/12 of the conventional system (120 mm → 10 mm), the system efficiency is expected to be improved by 2.0% → 2.4%. The introduction of the microchannel contributes to the significant downsizing of the cooling device, and the same performance as “water refrigerant + flat plate rectangular fin” is obtained. However, when a microchannel is used, since the pressure loss is large as shown in FIG. 9, it is necessary to introduce it in pairs with a micropump.

  As described above, in the second embodiment of the present invention, the refrigerant is formed in a duct shape so that the refrigerant flows inside the cooling device, or the outside of the cooling device is covered with the duct so that the refrigerant does not leak, and as a cooling source. The cooling system used in factories and power plants is divided and used, the seawater is circulated, the alternative chlorofluorocarbon (R134a) is circulated and used, and the low temperature side of the thermoelectric conversion module 1 is used. By cooling, the temperature gradient between the high temperature side surface and the low temperature side surface of the thermoelectric conversion module 1 can be increased, so that power can be generated efficiently and energy saving can be achieved.

  In particular, the system output, system efficiency, pressure loss, and the like can be verified using the fin shape and size of the cooling device and the type of refrigerant as parameters of the system performance of the thermoelectric conversion module, and the optimum system configuration can be obtained from the results.

  Next, a third embodiment of the present invention will be described with reference to FIG. 10. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Different parts will be described here.

  In the first embodiment and the second embodiment described above, the heat source side is a flat surface and the high temperature side surface of the thermoelectric conversion module 1 can be placed in contact, but the heat source is a fluid made of gas or liquid, for example, a tube When the heat source side is not a flat surface like a road, the high temperature side surface of the thermoelectric conversion module 1 cannot be placed in surface contact with the heat source side.

  Therefore, in the third embodiment, as shown in FIG. 10, the heating device 6 is disposed between the heat source 2 and the high thermal conductivity material 4 provided on the high temperature side surface of the thermoelectric conversion module 1, so that the heat source 2 and the thermoelectric conversion are arranged. Heat exchange is performed with the module 1, and other configurations are the same as those in the first embodiment and the second embodiment.

  Here, as the heating device 6, when the heat source 2 is a fluid made of gas or liquid, the heat source 2 is directly contacted with the fluid to extract heat, or the heat is indirectly heated without contacting the fluid directly. A stationary heat exchanger is used.

  With such a configuration, even when the thermoelectric conversion module cannot be directly attached to the heat source, heat can be extracted from the fluid serving as the heat source by the heating device 6 with high efficiency and provided to the thermoelectric conversion module.

1 is a cross-sectional view of an overall configuration showing a first embodiment of a thermoelectric conversion system according to the present invention. The perspective view which shows the structure of the cooling device in the embodiment. The figure for demonstrating the relationship between fin efficiency, fin thickness, and fin pitch in the embodiment. The figure for demonstrating the relationship between fin efficiency and fin height in the 2nd Embodiment of this invention. The figure for demonstrating the difference in the pressure loss by the difference in a refrigerant | coolant in the same embodiment. (A)-(f) is a figure which shows the structural example of the various cooling devices used with the thermoelectric conversion system by this invention. The figure for demonstrating the refrigerant | coolant speed dependence of the system efficiency by the combination of a cooling device and a refrigerant | coolant. The figure for demonstrating the refrigerant | coolant speed dependence of the system output by the combination of a cooling device and a refrigerant | coolant. The figure for demonstrating the refrigerant | coolant speed dependence of the pressure loss by the combination of a cooling device and a refrigerant | coolant. Sectional drawing of the whole structure which shows the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Thermoelectric conversion module, 2 ... Heat source, 3 ... Cooling device, 3a ... Flat rectangular fin, 3b ... Fin base, 4 ... High heat conductive material, 5 ... Heat insulating material, 6 ... Heating device

Claims (17)

A thermoelectric conversion module capable of mutually converting thermal energy and electrical energy;
A heat source for heating the high temperature side surface of the thermoelectric conversion module;
A cooling source for cooling the low-temperature side of the thermoelectric conversion module;
A cooling device for exchanging heat between the cooling source and the thermoelectric conversion module;
A highly thermally conductive material that assists in heat conduction between the heat source and the thermoelectric conversion module and between the cooling device and the thermoelectric conversion module;
A thermoelectric conversion system comprising: a heat insulating material for minimizing heat radiation to the outside, provided in a peripheral portion excluding the heat source, the cooling source, and the cooling device. A thermoelectric conversion module capable of mutually converting thermal energy and electrical energy;
A heat source for heating the high temperature side surface of the thermoelectric conversion module;
A heating device that exchanges heat between the heat source and the thermoelectric conversion module;
A cooling source for cooling the low-temperature side of the thermoelectric conversion module;
A cooling device for exchanging heat between the cooling source and the thermoelectric conversion module;
A highly thermally conductive material that assists in heat conduction between the heating device and the thermoelectric conversion module and between the cooling device and the thermoelectric conversion module;
A thermoelectric conversion system comprising: the heat source, the cooling source, a heating device, and a heat insulating material provided in a peripheral portion excluding the cooling device to minimize heat radiation to the outside. A thermoelectric conversion module capable of mutually converting thermal energy and electrical energy;
A cooling device in which the low temperature side of the thermoelectric conversion module is cooled by a cooling source;
A highly thermally conductive material that assists in heat conduction between the hot side of the thermoelectric conversion module and a heat source and between the cold side of the thermoelectric conversion module and the cooling device;
A thermoelectric conversion system comprising: a heat insulating material that is provided in a peripheral portion excluding the heat source and the cooling device and minimizes heat radiation to the outside. A thermoelectric conversion module capable of mutually converting thermal energy and electrical energy;
A cooling device in which the low temperature side of the thermoelectric conversion module is cooled by a cooling source;
A heating device in which a high temperature side surface of the thermoelectric conversion module is heated by a heat source;
A high thermal conductivity material that assists in heat conduction between the hot side of the thermoelectric conversion module and the heating device and between the cold side of the thermoelectric conversion module and the cooling device;
A thermoelectric conversion system comprising: a heat insulating material that is provided in a peripheral portion excluding the heating device and the cooling device and minimizes heat radiation to the outside.   The thermoelectric conversion system according to claim 2 or 4, wherein the heating device is any one of a direct contact heat exchanger and a static heat exchanger that draws heat from a fluid as a heat source.   The thermoelectric conversion system according to any one of claims 1 to 4, wherein the cooling device includes a plurality of fins arranged on the fin base at appropriate intervals.   In the cooling device, a plurality of fins are arranged on the fin base with appropriate intervals, and the cooling device is formed in a duct shape so that the refrigerant flows inside, or is covered with a duct so that the refrigerant does not leak. The thermoelectric conversion system according to any one of claims 1 to 4, wherein the thermoelectric conversion system is characterized.   8. The thermoelectric conversion system according to claim 6, wherein the cooling device has a vertical width and a horizontal width of the fin base that are integer multiples of a sum of a thermoelectric conversion module dimension and a stopper dimension, respectively.   The thermoelectric conversion system according to claim 6 or 7, wherein a fin pitch of each fin is 1 to 3 times a fin plate thickness.   The thermoelectric conversion system according to claim 6 or 7, wherein a fin height of each fin is 1 mm to 150 mm.   The plurality of fins are any of flat rectangular fins, corrugated flat rectangular fins, corrugated fins, offset fins, perforate fins, and louver fins. The thermoelectric conversion system described in 1.   The thermoelectric conversion system according to any one of claims 1 to 11, wherein the cooling source is a branch of a cooling system used as a cooling medium in various plants.   The thermoelectric conversion system according to any one of claims 1 to 11, wherein the cooling source is obtained by circulating seawater.   The thermoelectric conversion system according to any one of claims 1 to 11, wherein the cooling source is a circulation of alternative chlorofluorocarbon (R134a).   The thermoelectric conversion system according to any one of claims 1 to 14, wherein the heat source recovers unused exhaust heat from various plants.   The thermoelectric conversion system according to any one of claims 1 to 15, wherein the high thermal conductive material is any one of alumina, aluminum nitride, non-silicone grease, and silicone grease.   The thermoelectric conversion system according to any one of claims 1 to 4, wherein the cooling device includes a microchannel having a channel representative diameter of 1 mm or less.

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