JP4263052B2 - Temperature control device for electric double layer capacitor - Google Patents

Description

  The present invention relates to a temperature management device for maintaining the temperature of an electric double layer capacitor at an appropriate level.

  2. Description of the Related Art In recent years, attention has been focused on various power storage devices (for example, a drive power source of a hybrid electric vehicle) and an electric double layer capacitor that can be rapidly charged and has a long charge / discharge cycle life.

  In the case of Patent Document 1, the electric double layer capacitor is composed of a positive electrode body, a negative electrode body, and a separator interposed between them to form a laminate. The multilayer body (capacitor body) is immersed in an electrolytic solution and accommodated in a container. The container is sealed so that a part of a pair of terminals (one joined to the positive electrode body and the other to the negative electrode body) protrudes to the outside.

Patent Document 2 discloses an electrode structure suitable for connecting a plurality of electric double layer capacitors in series or in parallel to constitute a power storage device having a required capacity. Patent Document 3 discloses a water cooling device for a capacitor mounted on a vehicle as a drive power source for a hybrid electric vehicle.
JP 2002-289487 A JP 2000-313233 A JP-A-11-273984

  An object of this invention is to provide the means which can prevent effectively the thermal performance deterioration of an electric double layer capacitor based on such a prior art. The water cooling device of Patent Document 3 uses cooling water of an engine that drives a generator, and a cooling jacket is formed so as to surround a predetermined number of capacitors. This limits the range of vehicles that can be used. Another object of the present invention is to provide an effective means for solving such problems.

According to a first aspect of the present invention, there is provided a thermoelectric cooling element for cooling or heating the electric double layer capacitor and a thermoelectric cooling element so as to maintain the temperature of the electric double layer capacitor at an appropriate level in the temperature management device for the electric double layer capacitor. And the thermoelectric cooling element is disposed on the external electrode of the electric double layer capacitor or a connecting electrode connecting them in series, and the electric energy to the thermoelectric cooling element And means for controlling the current flow direction are means for determining the amount of electric power to the thermoelectric cooling element according to the temperature and charge / discharge power of the electric double layer capacitor, and to the thermoelectric cooling element according to the temperature of the electric double layer capacitor. Means for determining the current flow direction .

2nd invention is the temperature management apparatus of the electric double layer capacitor which concerns on 1st invention, Insulation heat-transfer sheet | seat between the thermoelectric cooling element and the external electrode of an electric double layer capacitor, or the connection electrode which connects between these It is characterized by interposing.

According to a third aspect of the present invention, in the temperature management device for an electric double layer capacitor , a liquid circulation path, means for actively exchanging heat between the liquid in the circulation path and the electric double layer capacitor, and a liquid in the circulation path A thermoelectric cooling element for cooling or heating, a pump for forcibly circulating the liquid in the circuit, and the amount of electric power to the thermoelectric cooling element and its flow direction so as to maintain the temperature of the electric double layer capacitor at an appropriate level. Means for controlling together with the pump, and means for positively exchanging heat between the liquid in the circulation path and the electric double layer capacitor, the pipe line along the connecting electrode connecting the plurality of electric double layer capacitors, A connecting pipe for connecting the pipes in series, wherein the pipe is formed integrally with the connecting electrode and is insulative to the liquid flowing through the circulation path, and the connection for connecting the pipes together. Insulate to tube Ones, temperature control device for the electric double layer capacitor characterized by using the.

According to a fourth aspect of the invention, in the temperature management device for the electric double layer capacitor according to the third aspect of the invention , the means for controlling the amount of electric power to the thermoelectric cooling element and its flow direction together with the pump is the temperature and charge / discharge of the electric double layer capacitor It is characterized by comprising means for determining the amount of electric power to the thermoelectric cooling element according to the electric power, and means for determining the direction of current flow to the thermoelectric cooling element according to the temperature of the electric double layer capacitor.

In the first aspect of the invention , the electric double layer capacitor controls the heat absorption (cooling) from the thermoelectric cooling element by controlling the electric energy to the thermoelectric cooling element and the flow direction thereof according to the temperature of the electric double layer capacitor. ) Or heat dissipation (heating) amount, it is maintained at an appropriate temperature level. For this reason, the thermal performance deterioration (deterioration of charge / discharge efficiency, etc.) of the electric double layer capacitor can be effectively prevented.

In this case, since the electric energy to the thermoelectric cooling element is determined by adding the charging / discharging power of the electric double layer capacitor to the parameter, the electric double layer capacitor has an endothermic (cooling) amount that fits the load state without excess or deficiency. Because it receives the amount of heat released (heated), it can be effectively maintained at an appropriate temperature level with good response .

In the second aspect of the invention, the insulating heat transfer sheet secures the thermal conductivity between the external electrode of the electric double layer capacitor and the thermoelectric cooling element, while maintaining the charge / discharge current and the thermoelectric cooling element flowing through the external electrode. Interference with the flowing direct current can be easily prevented.

In the third aspect of the invention, the liquid in the circulation path is forcibly circulated by driving the pump, and the thermoelectric cooling element is operated to receive the heat absorption amount or the heat dissipation amount according to the temperature of the electric double layer capacitor. A heat exchange actively performed with the multilayer capacitor receives a heat release amount or a heat absorption amount. In other words, by controlling the amount of power to the thermoelectric cooling element and the flow direction thereof together with the pump according to the temperature of the electric double layer capacitor, the electric double layer capacitor is connected to the thermoelectric cooling element via the liquid in the circulation path. In order to receive the amount of heat absorbed or radiated according to the temperature, it is maintained at an appropriate temperature level. For this reason, the thermal performance deterioration (deterioration of charge / discharge efficiency, etc.) of the electric double layer capacitor can be effectively prevented .

In this case, since the pipe line is integrally formed with the connecting electrode, the thermal conductivity to the pipe line is increased, and the amount of heat can be efficiently transferred between the pipe line and the insulating liquid. The insulating connecting pipe also avoids a short circuit between the connecting electrodes in which the pipes are integrally formed .

In the fourth aspect of the invention, the electric energy to the thermoelectric cooling element is determined by adding the charge / discharge power of the electric double layer capacitor to the parameter. Because it receives the amount of cooling or heat dissipation (heating), it can effectively maintain the appropriate temperature level with good response .

In the first to fourth inventions , the heat absorption or heat dissipation of the thermoelectric cooling element directly acts on the external electrode or connection electrode of the electric double layer capacitor, so that the inside of the electric double layer capacitor can be efficiently and efficiently responsive. Can be cooled or heated. In the fifth to seventh inventions , the heat absorption or heat dissipation of the thermoelectric cooling element with respect to the electric double layer capacitor indirectly acts via the liquid in the circuit, so the first to fourth inventions. Can cool or heat the electric double layer capacitor responsively and efficiently, but unlike mounting to the external electrode or connecting electrode, the installation space around the electric double layer capacitor is not subject to layout restrictions, so thermoelectric cooling This allows a large degree of freedom related to element design.

  1 to 3 show an embodiment of the present invention, in which a plurality of electric double layer capacitors 10 are connected in parallel via a pair of connecting electrodes 11. The connection electrode 11 is formed in a rectangular plate shape from a material (for example, aluminum) having good electrical conductivity and thermal conductivity, like the external electrode 12 of the electric double layer capacitor 10. An insulating heat transfer sheet 13 is stacked on the rectangular plane of the connection electrode 11, and a thermoelectric cooling element 14 is disposed thereon.

  The thermoelectric cooling element 14 is a junction pair of a P-type semiconductor and an N-type semiconductor, and is configured in a unit in which a plurality of elements are electrically connected in series and thermally connected in parallel. When a direct current (DC) current flows in the thermoelectric cooling element 14 (thermoelectric cooling unit), a heating (heat dissipation) action occurs on one side and a cooling (heat absorption) action on the opposite side occurs on both sides of the element. Changing the direction of DC current flow reverses the heating and cooling surfaces of the element. In the thermoelectric cooling element 14, the fin 15 is disposed on the side opposite to the insulating heat transfer sheet 13.

  In the electric double layer capacitor 10, the capacitor main body is accommodated in the container together with the electrolytic solution, and terminals (electrode leads) constituting the pair of external electrodes 12 a and 12 b are drawn from one side of the container. Although not shown, the capacitor body is composed of a rectangular positive electrode body and negative electrode body and a separator (a porous film such as paper) interposed therebetween to form a predetermined laminate. The positive electrode body and the negative electrode body are composed of a collecting electrode and polarizable electrodes (activated carbon electrodes) formed on both surfaces thereof. These collector electrodes are made of a rectangular metal foil (for example, an aluminum foil), and a strip-shaped lead portion is formed integrally with one side of the rectangular plane. The same polarity of each lead part is bundled together, and the terminal corresponding to polarity is joined to the binding part.

  The capacitor body is immersed in the electrolytic solution and accommodated in a container. The container is formed in a bag shape having one side opened from a resin laminated film (for example, aluminum laminate) having a metal intermediate layer, and a part of the terminal is drawn out of the container from the opening. The inside of the container is vacuum-evacuated to remove excess electrolyte and air and moisture, and the bag is sealed in a vacuum state with the pair of terminals sandwiching the pair of terminals.

  In FIG. 3, the ECU 15 (electronic control unit for capacitor temperature management) controls the amount of electric power and current flow to the thermoelectric cooling element 14, and the part that best reflects the internal temperature of the electric double layer capacitor 10. A temperature sensor 16 that detects the temperature of the external electrode 12 (for example, the external electrode 12 having good thermal conductivity) is provided. Reference numeral 17 denotes a load to which a plurality of electric double layer capacitors are connected as a power storage device. In this example, a rotating electric machine for traveling a vehicle and a rectifier (for example, an inverter) for adjusting its output (power running torque and regenerative torque) are provided. An ECU 18 (electronic control unit for charge / discharge control) that controls charge / discharge of the power storage device with respect to the load is provided.

  The electronic control unit 15 for capacitor temperature management determines the amount of electric power and the flow direction of current to the thermoelectric cooling element 14 based on the detection signal of the temperature sensor 16 and the charge / discharge information from the electronic control unit 18 for charge / discharge control. Control. In this electronic control unit 15, means for determining the amount of electric power to the thermoelectric cooling element 14 according to the detection signal of the temperature sensor 16 and the charge / discharge information from the electronic control unit 18 for charge / discharge control, Means for determining the direction of current flow to the thermoelectric cooling element 14 in response to the detection signal.

  FIG. 6 explains the contents of control related to the electronic control unit 15 for managing the capacitor temperature, and is performed every predetermined control cycle. In S1, it is determined whether or not the power storage device is being charged / discharged (operated) based on the charge / discharge information from the electronic control unit 18 for charge / discharge control. When the determination of S1 is yes, the process proceeds to S2, while when the determination of S1 is no, the power supplied to the thermoelectric cooling element 14 is cut off (OFF) or the cut off state is maintained in S6.

  In S2, it is determined whether the temperature of the electric double layer capacitor 10 is within an appropriate range (appropriate level) for the detection signal of the temperature sensor 16. If it is determined in S2 that the temperature of the electric double layer capacitor exceeds the upper limit value of the appropriate range, the process proceeds to S3. If the temperature of the electric double layer capacitor 10 is lower than the lower limit value of the appropriate range, the process proceeds to S4. If it is determined in S2 that the temperature of the electric double layer capacitor 10 is within an appropriate range, the process proceeds to S5.

  In S3, the electric energy Pt corresponding to the detection signal of the temperature sensor 16 (temperature of the electric double layer capacitor 10) is obtained based on the control map of FIG. 4, and the charge / discharge control electrons are calculated based on the control map of FIG. Thermoelectric cooling is performed so that the amount of power Pp corresponding to the charge / discharge information from the control unit 18 is obtained and the amount of power (Pt + Pp) flows in the cooling direction of the thermoelectric cooling element 14 (current direction in which the connecting electrode 11 side becomes the heat absorption surface). The energization to the element 14 is controlled. In S4, energization to the thermoelectric cooling element 14 is controlled so that a preset amount of power (a constant value) flows in the heat radiation direction of the thermoelectric cooling element 14 (the current direction in which the connecting electrode 11 side becomes the heating surface). In S5, the power supplied to the thermoelectric cooling element 14 is cut off (OFF) or the cut off state is maintained.

  With such a configuration, since the heat absorption or heat dissipation of the thermoelectric cooling element 14 directly acts on the connecting electrode 11 having good electrical conductivity and thermal conductivity, the inside of the electric double layer capacitor 10 is efficiently cooled with good response. Or it can be heated. Since the electric energy to the thermoelectric cooling element 14 is determined by adding the charging / discharging electric power of the electric double layer capacitor 10, the electric double layer capacitor 10 has a heat absorption (cooling) amount or heat dissipation (radiation) suitable for the load state without excess or deficiency. Because it receives the amount of (heating), it can maintain the appropriate temperature level responsively and effectively. As a result, the thermal performance deterioration of the electric double layer capacitor 10 is prevented, and good charge / discharge efficiency can be secured.

  The amount of electric power in the heat dissipation direction of the thermoelectric cooling element 14 is controlled to a predetermined value (constant value) in S4 of FIG. 6, but according to the control map corresponding to the temperature of the electric double layer capacitor 10 and the charge / discharge power. By setting a control map, processing similar to S3 in FIG. 6 may be considered.

  7 to 9 show modifications of the power storage device, and a plurality of electric double layer capacitors 10 are connected in series and parallel via a plurality of connecting electrodes 11. Specifically, two sets of four electric double layer capacitors are connected in parallel, one by two by three connecting electrodes 11. Similarly to the external electrode of the electric double layer capacitor 10, the connecting electrode 11 is formed in a short shape from a material having good electric conductivity, and the external electrode of the electric double layer capacitor 10 is joined to the side surface thereof.

  In the case of illustration, the mounting board 19 is formed from the material with favorable thermal conductivity in the connection electrodes 11b and 11c, and the thermoelectric cooling element 14 (thermoelectric cooling unit) is installed on each board surface 19. The connection electrodes 11 b and 11 c are formed integrally with the mounting board 19 from a material having good electrical conductivity and thermal conductivity (for example, aluminum), and insulation heat transfer is performed between the mounting board 19 and the thermoelectric cooling element 14. A sheet 13 is interposed. The connection electrode 11 a is formed in a rectangular plate shape that does not have the mounting board 19.

  When a direct current (DC) current flows, the thermoelectric cooling element 14 has a heating (heat dissipation) action on one side and a cooling (endothermic) action on the opposite side on both sides of the element. Changing the direction of DC current flow reverses the heating and cooling surfaces of the element. In the thermoelectric cooling element 14, the fin 15 is disposed on the side opposite to the insulating heat transfer sheet 13.

  Although not shown, an ECU (electronic control unit for capacitor temperature management) that controls the amount of electric power and current flow to the thermoelectric cooling element 14 and an ECU (for charge / discharge control) that controls charging / discharging of the power storage device with respect to the load. Electronic control unit). The electronic control unit for managing the capacitor temperature is similar to the flowchart of FIG. 6, based on the detection signal of the temperature sensor and the charge / discharge information from the electronic control unit for charge / discharge control, the electric energy and current to the thermoelectric cooling element 14. It controls the flow direction.

  In the case of FIGS. 1 to 3 and FIGS. 7 to 9, the thermoelectric cooling element 14 is added to the connection electrode 11 that connects the plurality of electric double layer capacitors 10, but the installation space can be secured. If so, it may be attached to the external electrodes 12 a and 12 b of the electric double layer capacitor 10.

  FIG. 10 illustrates another embodiment, and two sets of four electric double layer capacitors 10 in parallel are directly connected to each other by three connecting electrodes 11. In order to maintain the temperature of the electric double layer capacitor 11 at an appropriate level, a liquid circulation path 25 that passes through the heat exchanger 20, a pipe line 22 that forms a part of the circulation path 25 along the connection electrode 11, and these A connection pipe 23 that connects the pipe lines 22 in series and a pump 21 that forcibly circulates the liquid in the circulation path 25 are provided.

  As shown in FIG. 11, the connection electrode 11 is formed integrally from a material having good electrical conductivity and thermal conductivity, like the external electrode 12 of the electric double layer capacitor 10, including the pipe line 22 along one side of the rectangle. It is. Insulating oil is used for the liquid flowing through the circulation path 25 in order to ensure insulation with the connection electrode 11. About the connection pipe 23 which connects the pipe line 22 in series, in order to avoid the short circuit between the connection electrodes 11, all or one part is formed from an insulating material.

  The heat exchanger 20 is formed in a box-shaped vessel 32 as shown in FIGS. 12 to 14, and is provided with a plurality of guide plates 34 that form liquid meandering paths 33 therein. A box-shaped vessel 32 including a plurality of guide plates 34 is formed of a material having good thermal conductivity, and the thermoelectric cooling element 14 that actively cools or heats the liquid flowing through the meandering path 33 on the outer surface of the vessel 32. (Thermoelectric cooling unit) is installed.

  When a direct current (DC) current flows, the thermoelectric cooling element 14 has a heating (heat dissipation) action on one side of the element and a cooling (endothermic) action on the opposite side. Changing the direction of DC current flow reverses the heating and cooling surfaces of the element. In the thermoelectric cooling element 14, the fin 15 is arrange | positioned on the opposite side to an insulated heat transfer sheet.

  The liquid in the circulation path 25 flows between the heat exchanger 20 and the pipe line 22 along the connection electrode 11 and the connection pipe 23 by driving the pump 21. The liquid flowing through the meandering path 33 of the heat exchanger 20 is suitably maintained at the supply side temperature to the pipe line 22 and the connecting pipe 23 by the operation of the thermoelectric cooling element 14, and passes through the pipe line 23 along the connecting electrode 11. In doing so, since the amount of heat is exchanged, the temperature of the electric double layer capacitor 10 can be maintained at an appropriate level.

In FIG. 10, 30 is an ECU (Electronic Control Unit for Capacitor Temperature Management) that controls the amount of electric power to the thermoelectric cooling element 14 and the direction of current flow together with the pump. A temperature sensor 16 that detects the temperature of a part that reflects well (for example, the external electrode 12 having good thermal conductivity) is provided. Although not shown, a load that uses a power storage device including a plurality of electric double layer capacitors 10 as a power source is provided, and an ECU (electronic control unit for charge / discharge control) that controls charging / discharging of the power storage device with respect to the load is provided. .

The electronic control unit 30 for managing the capacitor temperature pumps the amount of electric power and the flow direction of the current to the thermoelectric cooling element 14 based on the detection signal of the temperature sensor 16 and the charge / discharge information from the electronic control unit for charge / discharge control. 21 and control. In this electronic control unit 30 , means for determining the amount of electric power to the thermoelectric cooling element 14 according to the detection signal of the temperature sensor 16 and the charge / discharge information from the electronic control unit for charge / discharge control, and the detection of the temperature sensor 16 Means for determining the direction of current flow to the thermoelectric cooling element 14 in response to the signal.

FIG. 15 illustrates the contents of control related to the electronic control unit 30 for managing the capacitor temperature, and is performed at predetermined control cycles. In S1, it is determined whether or not the power storage device is being charged / discharged (operated) based on charge / discharge information from the electronic control unit for charge / discharge control. If the determination of S1 is yes, the process proceeds to S2, while if the determination of S1 is no, in S6, the thermoelectric cooling element 14 and the pump 21 are turned off (stopped), or they are kept in the OFF state.

  In S2, it is determined whether the temperature of the electric double layer capacitor 10 is within an appropriate range (appropriate level) for the detection signal of the temperature sensor 16. If it is determined in S2 that the temperature of the electric double layer capacitor 10 exceeds the upper limit value of the appropriate range, the process proceeds to S3. If the temperature of the electric double layer capacitor 10 is lower than the lower limit value of the appropriate range, the process proceeds to S4. If it is determined in S2 that the temperature of the electric double layer capacitor 10 is within an appropriate range, the process proceeds to S5.

  In S3, while the pump 21 is turned on, the electric energy Pt corresponding to the detection signal of the temperature sensor 16 (temperature of the electric double layer capacitor 10) is obtained based on the control map (see FIG. 4), and the control map (FIG. 5), the electric energy Pp corresponding to the charge / discharge information from the electronic control unit for charge / discharge control is obtained, and these electric energy (Pt + Pp) is the cooling direction of the thermoelectric cooling element 14 (the connecting electrode 11 side absorbs heat). The energization of the thermoelectric cooling element 14 is controlled so as to flow in the direction of the current that becomes the surface). In S4, while the pump 21 is turned on, the preset amount of electric power (a constant value) is supplied to the thermoelectric cooling element 14 so as to flow in the heat dissipation direction of the thermoelectric cooling element 14 (current direction in which the connecting electrode 11 side becomes the heating surface). Control energization. In S5, the thermoelectric cooling element 14 and the pump 21 are turned off (stopped), or they are kept in the OFF state.

  With such a configuration, the operation of the heat exchanger 20 is actively promoted by the operation of the thermoelectric cooling element 14. Since the heat absorption or heat dissipation of the thermoelectric cooling element 14 indirectly acts on the electric double layer capacitor 10 via the liquid in the circulation path, the embodiment of FIGS. 1 to 6 and FIGS. Although the capacitor 10 can be cooled or heated in a responsive and efficient manner, it is not subject to layout restrictions in the installation space around the electric double layer capacitor 10 unlike the case where the capacitor 10 is attached to the connection electrode 11 or the external electrode 12. The degree of freedom related to the design of the element 14 can be greatly increased.

It is explanatory drawing of the electrical storage apparatus which concerns on an electric double layer capacitor. It is explanatory drawing which shows the cross section A of FIG. It is a schematic diagram of the temperature management apparatus which concerns on an electric double layer capacitor. It is a characteristic view explaining control. It is a characteristic view explaining control. It is a flowchart explaining the control content. It is explanatory drawing of the electrical storage apparatus which concerns on an electric double layer capacitor. It is explanatory drawing which shows the cross section B of FIG. It is explanatory drawing which shows the cross section C of FIG. It is a schematic diagram of the temperature management apparatus which concerns on an electric double layer capacitor. FIG. 11 is an explanatory diagram showing a cross section D of FIG. 10. It is explanatory drawing which concerns on the structure of a heat exchanger and a thermoelectric cooling element. FIG. 13 is an explanatory view showing a cross section E of FIG. 12. It is explanatory drawing which shows the cross section F of FIG. It is a flowchart explaining the control content.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric double layer capacitor 11 11a-11c Connection electrode 12, 12a, 12b External electrode 13 Insulation heat transfer sheet 14 Thermoelectric cooling element (thermoelectric cooling unit)
DESCRIPTION OF SYMBOLS 15,30 Electronic control unit for capacitor temperature management 16 Temperature sensor 17 Load 18 Electronic control unit for charge / discharge control 20 Heat exchanger 21 Pump 22 Pipe line 23 Connection pipe 25 Circulation path 32 Body 33 Meander path 34 Guide plate

Claims (4)

Comprising a thermoelectric cooling element for cooling or heating an electric double layer capacitor, and means for controlling the electric energy and the direction of flow of current to the thermoelectric cooling element to maintain the temperature of the electric double layer capacitor to the proper level, the The thermoelectric cooling element is disposed on an external electrode of the electric double layer capacitor or a connecting electrode that is connected in series between them, and means for controlling the amount of electric power and the direction of current flow to the thermoelectric cooling element are the same as those of the electric double layer capacitor. Means for determining the amount of power to the thermoelectric cooling element according to the temperature and charge / discharge power, and means for determining the direction of current flow to the thermoelectric cooling element according to the temperature of the electric double layer capacitor. An electrical double layer capacitor temperature management device. The temperature of the electric double layer capacitor according to claim 1, wherein an insulating heat transfer sheet is interposed between the thermoelectric cooling element and an external electrode of the electric double layer capacitor or a connecting electrode connecting them. Management device. A liquid circulation path, a means for actively exchanging heat between the circulation path liquid and the electric double layer capacitor, a thermoelectric cooling element for cooling or heating the circulation path liquid, and a circulation path liquid. A pump forcibly circulating, and means for controlling together with the pump the amount of power to the thermoelectric cooling element and its flow direction so as to maintain the temperature of the electric double layer capacitor at an appropriate level, Means for actively exchanging heat with the electric double layer capacitor includes a pipe line along a connecting electrode for connecting a plurality of electric double layer capacitors, and a connecting pipe for connecting the pipes in series. The electrical connection is characterized in that the conduit is formed integrally with the connecting electrode, and an insulating material is used for the liquid flowing through the circulation channel, and an insulating material is used for the connecting tube connecting the conduits. Double layer capacitor temperature Management device. The means for controlling the electric energy to the thermoelectric cooling element and the flow direction thereof together with the pump includes means for determining the electric energy to the thermoelectric cooling element according to the temperature and charge / discharge power of the electric double layer capacitor, The temperature management device for an electric double layer capacitor according to claim 3 , further comprising means for determining a flow direction of current to the thermoelectric cooling element according to temperature.

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