JP2013172576A - Power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generator whose power generation efficiency is improved by controlling a temperature between two thermoelectric elements.SOLUTION: A power generator 1 includes: a first thermoelectric element 10 disposed to exchange heat with a high-temperature heat source 13; and a second thermoelectric element 20 disposed to exchange heat with a low-temperature heat source 23. A performance index of the first thermoelectric element 10 is higher than that of the second thermoelectric element 20 at a temperature of the high-temperature heat source 13; the performance index of the second thermoelectric element 20 is higher than that of the first thermoelectric element 10 at a temperature of the low-temperature heat source 23; and a heat transport amount of a heat transport medium that transports heat by circulating between the first thermoelectric element 10 and the second thermoelectric element 20 is controlled. As a result, a heat amount moving from the first thermoelectric element 10 on a high-temperature heat source 13 side to the second thermoelectric element 20 on a low-temperature heat source 23 side is controlled and temperatures of the first thermoelectric element 10 and the second thermoelectric element 20 are set at temperatures at which favorable power generation efficiency is attained, thereby improving power generation efficiency of the power generator 1.

Description

  The present invention relates to a power generator.

  A technique for recovering thermal energy of hot exhaust gas discharged from an internal combustion engine as electric energy by a thermoelectric conversion element is known. An example of such a technique is disclosed in Patent Document 1. In the exhaust heat power generation device for an internal combustion engine of Patent Document 1, the cooling is such that the high temperature side surface of the thermoelectric conversion element faces the radial center of the exhaust port and the low temperature side surface is formed around the exhaust port on the tube wall of the exhaust port. It is arranged so as to face the water passage, and power generation is performed while ensuring a temperature difference between the two surfaces.

  In addition, as a technique considered to be related to the present invention, for example, Patent Document 2 discloses an exhaust heat power generation apparatus that adjusts a flow rate adjustment valve and adjusts a flow rate of exhaust gas sent to a thermoelectric element serving as a power generation unit. Yes.

JP 2006-266221 A Japanese Patent Laid-Open No. 11-229867

  By the way, the power generation performance of the thermoelectric element is determined by the characteristics of the thermoelectric element and the temperature difference (temperature range) between the high temperature side surface and the low temperature side surface of the thermoelectric element. As for the characteristics of the thermoelectric element, the higher the figure of merit of the thermoelectric element, the higher the power generation efficiency and the better the power generation performance. FIG. 1 shows a figure of merit with respect to temperature and is a diagram illustrating the characteristics of thermoelectric elements. As shown in FIG. 1, the characteristics of the element vary depending on the material constituting the element, and there are temperature ranges where the power generation performance can be efficiently exhibited for each material constituting the element. At present, no material that can generate power efficiently in a wide temperature range has been found.

  For example, the element using a material having a high performance index in the low temperature range shown in FIG. 2A efficiently generates power in the low temperature range (L), but the power generation efficiency is high in the high temperature range (H). bad. On the other hand, the element using a material having a high performance index in the high temperature range shown in FIG. 2B efficiently generates power in the high temperature range (H), but in the low temperature range (L), the power generation efficiency. Is bad. As described above, since the power generation efficiency is remarkably lowered if the temperature range in which the power generation performance can be efficiently exhibited is exceeded, it is necessary to select an element made of a material suitable for the temperature range to be used. However, there is no convenient material suitable for the temperature range to be used.

  Therefore, as shown in FIG. 3, a cascade type in which a high temperature element 102 made of a material that efficiently generates power in a high temperature range and a low temperature element 103 made of a material that efficiently generates power in a low temperature range are combined. The thermoelectric element 101 is employed. The thermoelectric element 101 sandwiches a high-temperature element 102 including a p-type semiconductor element and an n-type semiconductor element between a high-temperature plate 104 and an intermediate plate 106 on the high-temperature heat source side, and at a low temperature including a p-type semiconductor element and an n-type semiconductor element. The element 103 is sandwiched between a low temperature plate 105 and an intermediate plate 106 on the low temperature heat source side.

FIG. 4 is a diagram showing a figure of merit of the cascade type thermoelectric element 101. T _H in Figure 4 the temperature of the high-temperature heat source, the T _C temperature of the cold heat source, the Z _H merit of high temperature element, the Z _C represents the performance index of the low temperature element. The figure of merit of the cascade type thermoelectric element 1 depends on the temperature (intermediate temperature) _TN of the intermediate plate. That is, if the intermediate temperature _TN is too high, the power generation efficiency in the high temperature element 2 is high, but the power generation efficiency in the low temperature element 3 is low, and the power generation efficiency as a whole is reduced. On the other hand, if the intermediate temperature _TN is too low, the power generation efficiency in the low temperature element 3 is high, but the power generation efficiency in the high temperature element 2 is low, and the power generation efficiency as a whole is reduced.

In the conventional thermoelectric element, since the temperature (intermediate temperature T _N ) between the two elements of the cascade type is not considered, the optimum temperature range for the power generation efficiency is not used, and the power generation efficiency is good. That wasn't true.

  Accordingly, an object of the present invention is to provide a power generation apparatus that controls the temperature between two thermoelectric elements to improve power generation efficiency.

  A power generator of the present invention that solves such a problem includes a first thermoelectric element arranged to exchange heat with a high-temperature heat source, and a second thermoelectric element arranged to exchange heat with a low-temperature heat source, The performance index of the first thermoelectric element is higher than the performance index of the second thermoelectric element at the temperature of the high temperature heat source, and the performance index of the second thermoelectric element is the performance of the first thermoelectric element at the temperature of the low temperature heat source. The relationship is higher than the index, and the heat transport amount of a heat transport medium that transports heat by circulating between the first thermoelectric element and the second thermoelectric element is controlled.

  According to the above configuration, the amount of heat transferred from the first thermoelectric element on the high temperature heat source side to the second thermoelectric element on the low temperature heat source side can be controlled, and the temperature of the first thermoelectric element and the temperature of the second thermoelectric element can be controlled. Thereby, each temperature of a 1st thermoelectric element and a 2nd thermoelectric element can be made into the temperature from which electric power generation efficiency becomes favorable. As a result, the power generation efficiency of the power generator can be improved.

  In the above power generation apparatus, the heat transport amount may be controlled so that the temperature of the heat transport medium becomes a temperature at which the performance index of the first thermoelectric element and the performance index of the second thermoelectric element coincide with each other. . Accordingly, the first thermoelectric element can generate power in a temperature range where the power generation performance of the first thermoelectric element is high, and the second thermoelectric element can generate power in a temperature range where the power generation performance of the second thermoelectric element is high. As a result, the power generation efficiency of the power generator can be improved.

  In the above power generator, the heat transport amount control means includes a heat transport path through which the heat transport medium moves from the first thermoelectric element to the second thermoelectric element, and the heat transport medium from the second thermoelectric element to the second thermoelectric element. You may provide the return path which returns to a 1st thermoelectric element, and the control valve which controls the flow volume of the said return path. In this configuration, when the temperature difference between the first thermoelectric element and the second thermoelectric element is small, the control valve may be closed.

  In the above power generator, the high-temperature heat source may be exhaust exhausted from an internal combustion engine. In this configuration, the low-temperature heat source may be cooling water that circulates and cools the internal combustion engine.

  The power generator of the present invention can improve the power generation efficiency by controlling the temperature between two thermoelectric elements.

It is the figure which showed the performance index with respect to temperature, and demonstrated the characteristic of the thermoelectric element. (A) is the figure which showed the relationship between the temperature of a device which shows a high figure of merit in a low temperature range, and the figure of merit, and (b) is the temperature and the figure of merit of the device which shows a high figure of merit in a high temperature range. It is the figure which showed the relationship. It is the figure which showed the example of the cascade type thermoelectric element. It is the figure which showed the figure of merit of the cascade type thermoelectric element. It is the figure which showed the electric power generating apparatus of the Example. It is the figure which showed the performance index of the 1st thermoelectric element and 2nd thermoelectric element in an electric power generating apparatus. It is the figure which showed the relationship between the temperature of a high-temperature heat source and a low-temperature heat source, and the performance index of a thermoelectric element regarding the electric power generating apparatus of an Example. It is the figure which showed the relationship between the temperature of a high temperature heat source and a low temperature heat source, and the figure of merit of a thermoelectric element regarding the electric power generating apparatus of a comparative example. It is the figure which showed the engine incorporating the electric power generating apparatus. It is the figure which showed the multistage type electric power generating apparatus provided with two or more combinations of a high temperature heat source and a low temperature heat source. It is the figure which showed the electric power generating apparatus provided with the accumulator instead of the control valve.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 5 is a diagram showing the power generator 1 of the present embodiment. The power generation apparatus 1 includes a first thermoelectric element 10, a second thermoelectric element 20, and a heat transport medium circulation path 30. The first thermoelectric element 10 is arranged to exchange heat with the high temperature heat source 13. The first thermoelectric element 10 includes a first p-type semiconductor element 11 and a first n-type semiconductor element 12. The first p-type semiconductor element 11 and the first n-type semiconductor element 12 are made of a material selected so that the first thermoelectric element 10 has a high figure of merit at the temperature of the high-temperature heat source 13. The second thermoelectric element 20 is arranged to exchange heat with the low-temperature heat source 23. The second thermoelectric element 20 includes a second p-type semiconductor element 21 and a second n-type semiconductor element 22. The second p-type semiconductor element 21 and the second n-type semiconductor element 22 of the second thermoelectric element 20 are made of materials selected so that the second thermoelectric element 20 has a high figure of merit at the temperature of the low-temperature heat source 23. In particular, the first thermoelectric element 10 and the second thermoelectric element 20 are such that the performance index of the first thermoelectric element 10 is higher than the performance index of the second thermoelectric element 20 at the temperature of the high temperature heat source 13 and the temperature of the low temperature heat source 23. The performance index of the second thermoelectric element 20 is higher than the performance index of the first thermoelectric element 10.

  The heat transport medium circulation path 30 is a passage through which the heat transport medium circulates. The arrows in FIG. 5 indicate the flow direction of the heat transport medium. A heat transport medium is a medium that can receive heat from a hot object and transfer the heat to a cold object. The heat transport medium may be a latent heat material that receives and vaporizes heat from the high-temperature heat source 13 and delivers the heat to the low-temperature heat source 23 to liquefy it. The latent heat material can carry a large amount of heat energy by evaporating. Further, the heat transport medium may be a sensible heat material in which thermal energy transported from a temperature difference and a flow rate can be easily detected. In this embodiment, for example, water or oil may be adopted as the heat transport medium. The heat transport medium circulation path 30 includes a first heat exchange chamber 31 on the first thermoelectric element 10 side, a second heat exchange chamber 32 on the second thermoelectric element 20 side, a heat transport path 33, and a return path 34. The first heat exchange chamber 31 is in contact with the first thermoelectric element 10 on the opposite side of the high temperature heat source 13. The second heat exchange chamber 32 is in contact with the second thermoelectric element 20 on the opposite side of the low-temperature heat source 23. The heat transport path 33 and the return path 34 communicate with the first heat exchange chamber 31 and the second heat exchange chamber 32, respectively. As shown in FIG. 5, the heat transport medium moves from the first heat exchange chamber 31 to the second heat exchange chamber 32 in the heat transport path 33. In contrast, the heat transport medium moves from the second heat exchange chamber 32 to the first heat exchange chamber 31 in the return path 34. A control valve 35 is provided on the return path 34, and the control valve 35 controls the flow rate of the heat transport medium flowing through the return path 34 by adjusting the throttle. That is, the control valve 35 controls the flow rate of the heat transport medium from the second heat exchange chamber 32 to the first heat exchange chamber 31. The opening of the control valve 35 may be adjusted by an electric mechanism such as an electromagnetic valve, or may be adjusted by a mechanical mechanism such as a diaphragm.

  Next, the operation of the power generator 1 will be described. The power generation apparatus 1 generates power using the thermoelectric effect (Seebeck effect) of the first thermoelectric element 10 and the second thermoelectric element 20. The condition for the power generation device 1 to generate power is that the temperature of the heat transport medium is lower than the temperature of the high temperature heat source 13 and the temperature of the heat transport medium is higher than the temperature of the low temperature heat source 23.

  Here, the description will be made assuming that the conditions for generating power by the power generation apparatus 1 are satisfied. Since the high temperature heat source 13 is at a higher temperature than the heat transport medium, the first thermoelectric element 10 generates power due to a temperature difference between the high temperature heat source 13 and the heat transport medium in the first heat exchange chamber 31. At this time, the first thermoelectric element 10 absorbs heat from the high-temperature heat source 13 and dissipates heat to the heat transport medium. The heat transport medium that has received heat from the first thermoelectric element 10 in the first heat exchange chamber 31 passes through the heat transport path 33 and is sent to the second heat exchange chamber 32. In addition, the second thermoelectric element 20 generates power due to a temperature difference between the heat transport medium in the second heat exchange chamber 32 and the low-temperature heat source 23. At this time, the second thermoelectric element 20 absorbs heat from the heat transport medium and dissipates heat to the low-temperature heat source 23. That is, the heat transport medium that has received heat from the first thermoelectric element 10 in the first heat exchange chamber 31 delivers heat to the second thermoelectric element 20 in the second heat exchange chamber 32. The heat transport medium in the second heat exchange chamber 32 is lowered in temperature by delivering heat to the second thermoelectric element 20. Thereafter, the heat transport medium whose temperature has decreased passes through the return path 34 and returns to the first heat exchange chamber 31.

  As described above, the heat transport medium transports heat from the first heat exchange chamber 31 to the second heat exchange chamber 32 while circulating through the heat transport medium circulation path 30. The power generator 1 controls the flow rate of the heat transport medium supplied to the first heat exchange chamber 31 by adjusting the opening of the control valve 35 by a control unit such as an ECU, for example. By changing the flow rate of the heat transport medium, the amount of heat transported from the first heat exchange chamber 31 to the second heat exchange chamber 32 changes. If the amount of heat transported from the first heat exchange chamber 31 to the second heat exchange chamber 32 decreases, the temperature of the low temperature side portion of the first thermoelectric element 10 increases and the temperature of the high temperature side portion of the second thermoelectric element 20 increases. descend. Conversely, if the amount of heat transported from the first heat exchange chamber 31 to the second heat exchange chamber 32 increases, the temperature of the low temperature side portion of the first thermoelectric element 10 decreases, and the high temperature side portion of the second thermoelectric element 20 Temperature rises. As described above, the power generation device 1 controls the temperature of the low temperature side portion of the first thermoelectric element 10 and the high temperature side portion of the second thermoelectric element 20 by controlling the amount of heat transported by the heat transport medium. Note that the power generation device 1 may include a temperature sensor that measures the temperature of the heat transport medium in the heat transport path 33. The information measured by the temperature sensor may be sent to a control unit such as an ECU, for example, and the opening degree of the control valve 35 may be controlled based on the temperature information received by the control unit.

数１の式によると、発電効率ηは高温熱源温度Ｔ_Ｈと低温熱源温度Ｔ_Ｃとの温度差（Ｔ_Ｈ−Ｔ_Ｃ）が増加するほど向上し、性能指数Ｚが上昇するほど向上する。図６は発電装置１における第１熱電素子１０と第２熱電素子２０の性能指数を示した図である。図６中の実線は第１熱電素子１０の性能指数を示し、破線は第２熱電素子２０の性能指数を示している。図中の横軸は温度を示し、図中の高温熱源温度Ｔ_Ｈと低温熱源温度Ｔ_Ｃの温度差（有効温度差）は発電装置１の性能（発電効率）を決める因子の一つであり、有効温度差が増加するほど発電効率が高まる。また、図６中の縦軸は性能指数を示しており、第１熱電素子１０または第２熱電素子２０の発電時の温度の値に対応する性能指数が高いほど、発電装置１の発電効率が高まる。ここで、図６中に示す第１熱電素子１０の性能指数と第２熱電素子２０の性能指数の値が一致する温度を最適温度Ｔ_Ｂとする。図６に示すように、最適温度Ｔ_Ｂよりも高温では、第１熱電素子１０の性能指数が第２熱電素子２０の性能指数よりも高く、最適温度Ｔ_Ｂよりも低温では、第２熱電素子２０の性能指数が第１熱電素子１０の性能指数よりも高い。 Here, the flow rate of the heat transport medium will be described in relation to the performance of the power generation device 1. The following expression is an expression representing the power generation efficiency η of the power generator 1. In the following equation, T _H is a high temperature heat source temperature, T _C is low heat source temperature, Z is merit.

According to equation 1, the power generation efficiency η is improved as the temperature difference between the high temperature heat source temperature T _H and the low temperature heat source temperature T _C (T H _{-T C)} increases, improved as performance index Z is increased. FIG. 6 is a diagram showing the figure of merit of the first thermoelectric element 10 and the second thermoelectric element 20 in the power generation apparatus 1. The solid line in FIG. 6 indicates the performance index of the first thermoelectric element 10, and the broken line indicates the performance index of the second thermoelectric element 20. The horizontal axis in the figure indicates the temperature, the temperature difference between the high-temperature heat source temperature T _H and the low temperature heat source temperature T _C in the figure (the effective temperature difference) is one of factors that determine the performance of the power plant 1 (power generation efficiency) The power generation efficiency increases as the effective temperature difference increases. The vertical axis in FIG. 6 indicates the performance index. The higher the performance index corresponding to the temperature value during power generation of the first thermoelectric element 10 or the second thermoelectric element 20, the higher the power generation efficiency of the power generator 1 is. Rise. Here, the optimum temperature T _B the temperature value of the performance index of the performance index and the second thermoelectric element 20 of the first thermoelectric element 10 shown in FIG. 6 are identical. As shown in FIG. 6, the optimum temperature T at high temperatures than _B, the performance index of the first thermoelectric element 10 is higher than the performance index of the second thermoelectric element 20, a temperature lower than the optimum temperature T _B, the second thermoelectric element The figure of merit of 20 is higher than the figure of merit of the first thermoelectric element 10.

Next, the operation policy of the power generator 1 will be described. Generator 1, as the temperature of the heat transport medium is the optimum temperature T _B, flow rate of the heat transport medium in the heat transport passage 33, i.e., controls the opening of the control valve 35. By the temperature of the heat transport medium in the heat transport passage 33 which is located between the first thermoelectric element 10 and the second thermoelectric element 20 is the optimum temperature T _B, than the optimum temperature T _B of the first thermoelectric element 10 and maintained at an elevated temperature, maintained at a temperature lower than the optimum temperature T _B of the second thermoelectric element 20. Thereby, both the 1st thermoelectric element 10 and the 2nd thermoelectric element 20 generate electric power in the temperature range with a high figure of merit. Thus, the power generation apparatus 1 is such that the temperature of the heat transport medium is the optimum temperature T _B, by controlling the opening degree of the control valve 35, and thus to obtain high power generation efficiency. In the case or the temperature T _H is lower than the optimum temperature T _B of the high-temperature heat source 13, when the temperature T _C of the low-temperature heat source 23 is higher than the optimum temperature T _B is to a temperature of the heat transport medium and the optimum temperature T _B I can't. In such a case, the power generation apparatus 1, so as to approach the optimum temperature T _B as possible the temperature of the heat transport medium, by adjusting the opening degree of the control valve 35 controls the flow rate of the heat transport medium.

  Next, the temperature conditions of the high-temperature heat source 13 and the low-temperature heat source 23 and the power generation efficiency of the power generator 1 will be described in comparison with a case where the opening degree of the control valve 35 is not controlled. The power generation device of the comparative example has a configuration in which the control valve 35 is not provided or the opening degree of the control valve 35 is not fully adjusted while the opening degree of the control valve 35 is fully open as compared with the power generation device 1 described above. 7 and 8 are diagrams showing the relationship between the temperature of the high temperature heat source 13 and the low temperature heat source 23 and the figure of merit of the thermoelectric element. FIG. 7 relates to the power generation apparatus 1 of the present embodiment, and FIG. 8 relates to the power generation apparatus of the comparative example.

FIG. 7A and FIG. 8A show a state where the high-temperature heat source 13 is at a high temperature and the low-temperature heat source 23 is at a high temperature. Here, the temperature _{T H} of the high-temperature heat source 13 higher than the optimum temperature _{T B,} the temperature _{T C} of the low-temperature heat source 23 is set to be lower than the optimum temperature _{T B.} Generator 1 of this embodiment, the temperature of the heat transport medium is adjusted to be optimum temperature T _B. In the case of the conditions as shown in FIG. 7A, for example, the power generation device 1 appropriately sets the temperature of the heat transport medium to the optimum temperature while the control valve 35 is half open and the flow rate of the heat transport medium is moderate. T _B is set. Accordingly, the temperature of the first thermoelectric element 10 becomes optimum temperature T _B above, the temperature of the second thermoelectric element 20 is equal to or less than the optimum temperature T _B. Therefore, as shown in FIG. 7 (a), the first thermoelectric element 10 will power at a temperature _{T H} and the optimum temperature _T performance index _{Z H1} between _B of the high-temperature heat source 13. The second thermoelectric element 20 will power at a temperature _{T C} and the optimum temperature _T performance index _{Z C1} between the _B cold heat source 23. As described above, in the power generation device 1, the thermoelectric element having the higher performance index according to the temperature range generates power, and thus the power generation efficiency is increased. In this case, the performance index of the power generator 1 is dominated by the characteristics of the first thermoelectric element 10. On the other hand, in the power generation device of the comparative example, the temperature T _M of the heat transport medium is intermediate between the temperature T _H of the high temperature heat source 13 and the temperature T _C of the low temperature heat source 23. Therefore, the first thermoelectric element 10 generates power at a figure of merit Y _H1 between the temperature T _H of the high temperature heat source 13 and the temperature T _M of the heat transport medium, and the second thermoelectric element 20 generates the temperature T _{C of the} low temperature heat source 23. _Is generated with a figure of merit Y _C1 between the temperature and the temperature T _M of the heat transport medium. Therefore, higher than the optimum temperature T _B, at a temperature range lower than the temperature T _M of the heat transport medium, it will be generated by the second thermoelectric element 20 less merit than the first thermoelectric element 10, power generation efficiency Not optimal.

FIGS. 7B and 8B show a state where the high temperature heat source 13 is at a high temperature and the low temperature heat source 23 is at a low temperature. In the case of the condition as shown in FIG. 7B, for example, the opening degree of the control valve 35 is fully opened and the flow rate of the heat transport medium is increased. However. Again, as appropriate, to adjust the opening degree of the control valve 35 so that the temperature of the heat transport medium is the optimum temperature T _B. In this condition, as shown in FIG. 7 (b), the first thermoelectric element 10 is generated by the performance index _{Z H2} between the temperature _{T H} and the optimum temperature _{T B} of the high-temperature heat source 13, the second thermoelectric element 20 It is generated by the temperature _{T C} and the optimum temperature _T performance index _{Z C2} between the _B cold heat source 23. For this reason, since power generation is performed in a temperature range with a high performance index, the power generation apparatus 1 achieves high power generation efficiency. On the other hand, in the comparative example, the temperature T _M of the heat transport medium is equal to the optimum temperature T _B is rare, even in this case, in a temperature range between the temperature T _M and the optimal temperature T _B of the heat transport medium Therefore, power is generated by the thermoelectric element having the lower figure of merit, and optimal power generation efficiency cannot be obtained.

  FIGS. 7C and 8C show a state where the high temperature heat source 13 is in a low temperature state and the low temperature heat source 23 is in a high temperature state. Thus, when the condition as in 7 (c), that is, when the temperature difference between the first thermoelectric element 10 and the second thermoelectric element 20 is small, the power generator 1 closes the control valve 35 and the heat transport medium circulation path 30 The flow of the heat transport medium is stopped, and the transport of heat from the first heat exchange chamber 31 to the second heat exchange chamber 32 is stopped. Under this condition, since the effective temperature difference is small, the power generation efficiency decreases. For this reason, the transportation of heat is stopped and the power generation is stopped.

FIGS. 7D and 8D show a state where the high temperature heat source 13 is at a low temperature and the low temperature heat source 23 is at a low temperature. Here, it is assumed that the temperature T _H of the high-temperature heat source 13 is below the optimal temperature T _B. For conditions such as in FIG. 7 (d), the power generation apparatus 1, stop the opening of the control valve 35, by reducing the flow rate of the heat transport medium, the temperature of the heat transport medium as possible to the optimum temperature T _B Try to be close. This widens the effective temperature difference and increases power generation efficiency. In this case, the first thermoelectric element 10 does not generate power. The second thermoelectric element 20 is generated by the figure of merit _{Z C4} between the temperature _{T H} of the temperature _{T C} and high-temperature heat source 13 of the low-temperature heat source 23. Here, the performance index of the power generator 1 is dominated by the characteristics of the second thermoelectric element 20. On the other hand, in the power generation device of the comparative example, the temperature T _M of the heat transport medium is as follows optimum temperature T _B. In the comparative example, the first thermoelectric element 10 generates power in a temperature range where the second thermoelectric element 20 generates power more efficiently than the first thermoelectric element 10. For this reason, the power generation efficiency is not optimal.

In addition to the example described with FIG. 7, for example, higher than the optimum temperature T _B is the temperature T _H of the high-temperature heat source 13, is higher than the temperature T _C be the optimum temperature T _B of the low-temperature heat source 23, the power generation apparatus 1 to control the opening degree of the control valve 35 adjusts the flow rate of the heat transport medium, the temperature of the heat transport medium as possible may be as close to the optimum temperature T _B. As described above, the power generation apparatus 1 of this embodiment is essentially the temperature of the heat transport medium varies with the temperature of the temperature and the low temperature heat source 23 of the high-temperature heat source 13 and the optimum temperature T _B. Or if it is unable to approach the optimum temperature T _B. Thereby, even if the temperature conditions of the high temperature heat source 13 and the low temperature heat source 23 change, the power generator 1 generates power with the thermoelectric element having a higher performance index under the temperature condition given from the environment of the heat source, thereby improving the power generation efficiency. can do.

  The power generation apparatus 1 described above can be incorporated into an apparatus including the high temperature heat source 13 and the low temperature heat source 23. As an example, an example in which the power generator 1 is incorporated in the engine 50 will be described. FIG. 9 is a view showing an engine 50 in which the power generator 1 is incorporated. The engine 50 is an internal combustion engine mounted on a vehicle or the like. The engine 50 includes an engine main body 51 having a combustion chamber, a valve operating system, etc., a cooling water passage 52 through which cooling water of the engine main body 51 circulates, a radiator 53 that radiates heat from the cooling water, an intake pipe 54 that takes intake air into the combustion chamber, An exhaust pipe 55 is provided for discharging exhaust gas after combustion from the chamber. The cooling water passage 52 is provided with a cooling water branch passage 56 that branches from the main flow supplied to the engine body 51. The cooling water branch passage 56 is branched from the cooling water passage 52 downstream of the radiator 53 and upstream of the engine body 51, and is downstream of the engine main body 51 and upstream of the radiator 53 to the cooling water passage 52. Join. In such an engine 50, the power generator 1 is incorporated such that the first thermoelectric element 10 contacts the exhaust pipe 55 and the second thermoelectric element 20 contacts the piping of the cooling water branch passage 56. The power generation apparatus 1 performs power generation using the exhaust gas passing through the exhaust pipe 55 as the high temperature heat source 13 and the cooling water passing through the cooling water branch passage 56 as the low temperature heat source 23.

  When the power generator 1 is incorporated in an engine, the high temperature heat source 13 becomes high when the exhaust temperature rises, and the high temperature heat source 13 becomes low when the exhaust temperature falls. Further, when the cooling water temperature rises, the low temperature heat source 23 becomes high temperature, and when the cooling water temperature falls, the low temperature heat source 23 becomes low temperature. As shown in the description of FIG. 7, the power generation device 1 adjusts the opening degree of the control valve 35 according to the exhaust gas temperature and the cooling water temperature, and improves the power generation efficiency. Thereby, the electric power generating apparatus 1 can collect | recover efficiently the effective energy which the engine exhaust has. Further, when the temperature difference between the exhaust gas and the cooling water is small under the condition that the exhaust gas temperature is low and the cooling water temperature is high, the power generator 1 closes the control valve 35 to generate power as shown in FIG. To stop. Thereby, since the raise of a cooling water temperature is suppressed, the load of the radiator 53 can be reduced.

  There are a wide range of areas where such a power generator 1 can be used, and in addition to those described here, exhaust, cooling water, oil, radiating air, high-temperature solid that conducts heat, high-temperature latent heat refrigerant, heat storage, Radiant heat from sunlight, exhaust pipes, intentional combustion heat, or the like can be used. Moreover, as a low-temperature heat source, air, cooling water, oil, mist, a low-temperature solid that conducts heat, a latent heat refrigerant, radiation heat dissipation, cold storage heat, or the like can be used.

  As another configuration showing the embodiment of the present invention, as shown in FIG. 10, the power generation device 2 may have a multistage configuration including a plurality of combinations of high-temperature heat sources and low-temperature heat sources. The number of combinations of such a high temperature heat source and a low temperature heat source is not limited. In addition, as shown in FIG. 11, the power generation device 3 includes an accumulator 36 instead of the control valve 35, and controls the flow rate of the heat transport medium by controlling the volume of the heat transport medium in the accumulator 36. Good.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

1, 2, 3 Power generation device 10 First thermoelectric element 13 High temperature heat source 20 Second thermoelectric element 23 Low temperature heat source 30 Heat transport medium circulation path 33 Heat transport path 34 Return path 35 Control valve 50 Engine

Claims (6)

A first thermoelectric element arranged to exchange heat with a high temperature heat source;
A second thermoelectric element arranged to exchange heat with a low-temperature heat source;
With
The performance index of the first thermoelectric element is higher than the performance index of the second thermoelectric element at the temperature of the high temperature heat source, and the performance index of the second thermoelectric element is the temperature of the first thermoelectric element at the temperature of the low temperature heat source. The relationship is higher than the figure of merit,
A power generator that controls a heat transport amount of a heat transport medium that circulates between the first thermoelectric element and the second thermoelectric element to transport heat.   The heat transport amount is controlled so that the temperature of the heat transport medium becomes a temperature at which the performance index of the first thermoelectric element and the performance index of the second thermoelectric element coincide with each other. Power generation device. A heat transport path through which the heat transport medium moves from the first thermoelectric element to the second thermoelectric element;
A return path from which the heat transport medium returns from the second thermoelectric element to the first thermoelectric element;
The power generator according to claim 1, further comprising a control valve that controls a flow rate of the return path.   The power generator according to claim 3, wherein the control valve is closed when a temperature difference between the first thermoelectric element and the second thermoelectric element is small.   The power generator according to any one of claims 1 to 4, wherein the high-temperature heat source is exhaust discharged from an internal combustion engine.   The power generator according to claim 5, wherein the low-temperature heat source is cooling water for circulating and cooling the internal combustion engine.

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