JP2014158337A - Alkali metal thermoelectric converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a throughput of alkali metal ions for a solid electrolyte, without making the manufacturing difficult, in an alkali metal thermoelectric converter.SOLUTION: An alkali metal thermoelectric converter 1 includes: a closed container 2 having a heat receiving section 51, a heat radiating section 52, and a circulation path 28 of alkaline metal formed to pass through the heat receiving section and heat radiating section; a solid electrolyte 33 provided to delimit the circulation path in the heat receiving section, so as to allow passage of alkaline metal ions, and having an anode side face 38 and a cathode side face 37; an anode 7 provided on the anode side face side; a cathode 36 provided on the cathode side face side; and transportation means 46 for transmitting the alkaline metal in the circulation path to the anode side face of solid electrolyte. The anode side face has a plurality of protrusions 35, and the cathode side face is formed more smoothly than the anode side face.

Description

  The present invention relates to an alkali metal thermoelectric converter.

  As a thermoelectric converter, an alkali metal thermoelectric converter (AMTEC) using a β alumina solid electrolyte member having ion conductivity of alkali metal such as sodium (Na) is known (for example, Patent Document 1).

  The alkali metal thermoelectric converter has a vacuum sealed container having a heat receiving part exposed to a high temperature fluid and a heat radiating part exposed to the low temperature fluid, and the heat receiving part and the heat radiating part are disposed in the sealed container. An alkali metal circulation path is defined so as to pass through, and in the high temperature part which is a part corresponding to the heat receiving part of the circulation path, the circulation path is divided into an upstream high temperature part upstream and a downstream high temperature part downstream. A solid electrolyte, which is β-alumina solid electrolyte (BASE), is disposed in the sealed container so as to divide, a cathode member is disposed upstream of the high temperature portion, and an anode member is disposed downstream of the high temperature portion. .

  The operating principle of the alkali metal thermoelectric converter is that the alkali metal is separated into ions and electrons on the cathode member side, that is, on the upstream side of the high temperature part, only ions move through the solid electrolyte, and the electrons are connected to the cathode member. Passes through the external load and heads toward the anode member. Ions that have passed through the solid electrolyte recombine with electrons on the anode member on the downstream side of the high temperature portion of the solid electrolyte to become the original alkali metal. The alkali metal on the downstream side of the high temperature part is condensed in the low temperature part, and then continuously transported and circulated to the upstream side of the high temperature part of the solid electrolyte by a wick pump or an electromagnetic pump using capillary force.

  The power generation efficiency of the alkali metal thermoelectric converter greatly depends on the amount of alkali metal ions passing through the solid electrolyte. Therefore, by increasing the surface area of the cathode side surface and the anode side surface of the solid electrolyte, the contact area between the solid electrolyte and the alkali metal increases, and the amount of alkali metal ions entering the solid electrolyte increases on the anode side surface. On the cathode side, it is expected that the amount of alkali metal ions released from the solid electrolyte will increase. In order to increase the surface area of the cathode side surface and anode side surface of the solid electrolyte, the solid electrolyte is formed in a cylindrical shape, the cylindrical portion is curved into a corrugated shape, and irregularities are provided on the cathode side surface and the anode side surface (for example, patents). Reference 2).

Japanese Patent No. 2601889 Japanese Patent Laid-Open No. 3-178484

  In an alkali metal thermoelectric converter, the cathode may be formed on the cathode side surface of the solid electrolyte. The cathode is often formed as a porous thin film so that gaseous sodium can pass through. Therefore, if unevenness is formed on the side surface of the cathode of the BASE, it becomes difficult to form the cathode uniformly on the side surface of the cathode, and there is a possibility that disconnection of the cathode or poor contact between the cathode and the side surface of the cathode may occur. In addition, when irregularities are formed on both the anode side surface and the cathode side surface of the solid electrolyte, it may be difficult to separate (extract) the molding die when molding the solid electrolyte, which makes it difficult to manufacture including molding. .

  This invention is made | formed in view of the above background, Comprising: It makes it a subject to increase the passage amount with respect to the solid electrolyte of an alkali metal ion, without making manufacture difficult in an alkali metal thermoelectric converter. .

  In order to solve the above problems, the present invention is an alkali metal thermoelectric converter (1), which passes through a heat receiving part (51), a heat radiating part (52), and the heat receiving part and the heat radiating part. A sealed container (2) having a formed alkali metal circulation path (28); and an anode side face (38) and a cathode provided to permit passage of alkali metal ions and to divide the circulation path in the heat receiving section. A solid electrolyte (33) having a side surface (37), an anode (7) provided on the anode side surface side, a cathode (36) provided on the cathode side surface side, and an alkali metal in the circulation path; Transport means (46) for transporting the solid electrolyte to the anode side surface side, the anode side surface has a plurality of convex portions (35), and the cathode side surface is formed more smoothly than the anode side surface. Characterized in that it is.

  According to this configuration, the surface area of the anode side surface of the solid electrolyte increases due to the presence of the convex portion, and the contact area between the anode side surface and the alkali metal increases. This increases the amount of alkali metal that ionizes and migrates from the anode side into the solid electrolyte. On the other hand, since the cathode side surface is formed smoothly, it is easy to form the cathode on the cathode side surface. Further, since the cathode side surface is formed smoothly, the solid electrolyte can be easily formed. According to the applicant's research, in a conventional alkali metal thermoelectric converter, the amount of ions passing through the solid electrolyte may be significantly less than the amount of ion vacancies in the solid electrolyte. That is, there may be an excess of ion paths in the solid electrolyte. Therefore, it is considered that the amount of alkali metal ions passing through the solid electrolyte has a larger influence on the process in which alkali metal emits electrons and enters the anode side surface than the process in which alkali metal ions receive electrons and exit from the cathode side surface. Therefore, by smoothing the cathode side surface and providing a convex portion on the anode side surface, the cathode can be easily formed on the cathode side surface, and the amount of alkali metal ions passing through the fixed electrolyte can be increased.

  In the above invention, the convex portion may have a plate-like shape projecting outward from the main body portion of the solid electrolyte.

  According to this configuration, the surface area can be efficiently expanded by making the convex portion into a plate shape (fin shape).

  In the above invention, the circulation path has a chamber (27) having an inlet passage (17) and an outlet passage (18) in the heat receiving portion, and the solid electrolyte has an opening at one end and the other end. Is formed in a closed cylindrical shape, the opening is disposed in the chamber so as to communicate with the outlet passage, the chamber is divided into the inlet passage side and the outlet passage side, and an outer surface is the inlet passage. It is preferable that the anode side surface is directed to the side, and the inner surface is the cathode side surface.

  According to this configuration, the circulation path can be partitioned using a cylindrical solid electrolyte that is relatively easy to mold. In addition, the solid electrolyte can be easily formed by providing a cylindrical cathode side surface on the inner side of the cylindrical shape and an anode side surface provided with projections on the outer side.

  In the above invention, the solid electrolyte may be formed in a cylindrical shape, and an inner surface forming the cathode side surface may be formed in a cylindrical surface.

  According to this configuration, the cathode side surface can be formed smoothly.

  In the above invention, the convex portion may extend in the circumferential direction along the outer peripheral surface of the solid electrolyte to form an annular plate piece.

  According to this structure, a comparatively many convex part can be arrange | positioned on the outer peripheral surface of a solid electrolyte.

  In the above invention, a portion defining the inlet passage side of the chamber may include a conductive material to constitute the anode.

  According to this configuration, since the portion defining the inlet passage side of the chamber also serves as the anode, it is not necessary to separately provide an anode, and the number of parts can be omitted.

  In the above invention, the cathode may be a porous body provided on a side surface of the cathode.

  According to this configuration, the three-phase interface between the cathode, the solid electrolyte, and the gas phase can be widened without hindering the flow of gaseous alkali metal.

  In the above invention, the transportation means may be a wick (46) provided in the circulation path. The transport means may transport the alkali metal by centrifugal force by rotating the closed container. The transporting means may be an electromagnetic pump that transports the alkali metal by electromagnetic induction.

  According to these configurations, the alkali metal can be transported using various transportation means.

  According to the above configuration, in the alkali metal thermoelectric converter, the amount of alkali metal ions passing through the solid electrolyte can be increased without making the production difficult.

Sectional drawing of the alkali metal thermoelectric converter which concerns on 1st Embodiment. It is a top view of the alkali metal thermoelectric converter which concerns on 1st Embodiment, Comprising: One cell is broken and shown Sectional drawing of the alkali metal thermoelectric converter which concerns on 2nd Embodiment. Schematic diagram in which an alkali metal thermoelectric converter according to a second embodiment is arranged in an exhaust system of an automobile. Sectional view showing a modification of the solid electrolyte

  Hereinafter, an embodiment of an alkali metal thermoelectric converter according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of an alkali metal thermoelectric converter according to the first embodiment, and FIG. 2 is a plan view of the alkali metal thermoelectric converter according to the first embodiment. FIG. As shown in FIG.1 and FIG.2, the alkali metal thermoelectric converter (AMTEC) 1 has the airtight container 2 which makes an outer shell. The hermetic container 2 includes a disk-shaped first casing 5 with an axis A extending vertically, a cylindrical second casing 6 provided at the center of the lower surface of the first casing 5, and an outer peripheral portion of the upper surface of the first casing 5. A plurality of (three in this embodiment) cylindrical third casings 7 provided. The 1st casing 5 is formed from the material which has heat resistance and insulation. The second casing 6 is formed from a material having thermal conductivity and heat resistance. The plurality of third casings 7 are formed of a material having thermal conductivity, heat resistance, and electrical conductivity. The first casing 5 may be formed from a polymer material, and the second casing 6 and the plurality of third casings 7 may be formed from a metal material such as stainless steel or an aluminum alloy.

  A first hole 11 is recessed in the center of the lower surface of the first casing 5. The first hole 11 is a bottomed cylindrical hole having a circular cross section, and its axis is arranged coaxially with the axis A. The number of second holes 12 corresponding to the number of the third casings 7 (eight in this embodiment) is recessed around the first holes 11 at the center of the lower surface of the first casing 5. Each second hole 12 is a bottomed cylindrical hole having a circular cross section, and its axis is arranged in parallel with the axis A. Each second hole 12 is longer in the direction of the axis A than the first hole 11, that is, has a deep depth. The second holes 12 are arranged in the circumferential direction around the axis A with an interval of 45 ° from each other.

  The number of third holes 13 corresponding to the number of third casings 7 (eight in the present embodiment) is recessed in the outer peripheral portion of the upper surface of the first casing 5. Each third hole 13 is a bottomed cylindrical hole having a circular cross section, and its axis is arranged in parallel with the axis A. The third holes 13 are arranged at an interval of 45 ° in the circumferential direction around the axis A. The center of each second hole 12 and the center of each third hole 13 are offset from each other in the circumferential direction about the axis A.

  A cylindrical partition wall 14 projects downward from the lower surface of the first casing 5 so as to surround the first hole 11 inside the plurality of second holes 12. That is, the partition wall 14 is disposed so as to partition the first hole 11 and each second hole 12. The lower end of the partition wall 14 is an open end. The inner peripheral surface of the partition wall 14 is formed in a cylindrical surface, and the base end portion (upper end portion) has a smaller inner diameter than other portions. In other words, the partition wall 14 has a narrowed portion 15 whose inner diameter is set small at the upper end portion inside.

  A plurality of inlet passages 17 extending in the radial direction of the first casing 5 and communicating with the adjacent second hole 12 and third hole 13 are formed inside the first casing 5. The end of each inlet passage 17 opens to the side surface of the second hole 12 and the side surface of the third hole 13. In addition, a plurality of outlet passages 18 extending from the first hole 11 in the radial direction of the first casing 5 and connected to the third holes 13 are formed in the first casing 5. The end of each outlet passage 18 opens to the side surface of the first hole 11 and the bottom surface of the third hole 13. The inlet passage 17 is disposed so as not to communicate with the outlet passage 18 and the first hole 11, and the outlet passage 18 is disposed so as not to communicate with the inlet passage 17 and the second hole 12.

  The second casing 6 has a cylindrical portion 6A and an end wall 6B that closes one end of the cylindrical portion 6A, and the other end of the cylindrical portion 6A is an open end. The second casing 6 is joined to the lower surface of the first casing 5 so that the opening end faces upward and the partition wall 14 is received inside. The second casing 6 is disposed so that the axis of the cylindrical portion 6A is coaxial with the axis A. In the state where the first casing 5 and the second casing 6 are joined, the cylindrical portion 6A and the partition wall 14 are disposed concentrically, and the protruding end portion (lower end portion) of the partition wall 14 is formed on the end wall 6B of the second casing 6. On the other hand, they face each other through a gap. Thus, the second casing 6 is defined by the first passage 21 defined by the inner peripheral surface of the partition wall 14 and the end wall 6B of the second casing 6 and the cylindrical portion 6A in the vicinity of the end wall 6B. The second passage 22 and the third passage 23 defined by the outer peripheral surface of the partition wall 14 and the inner peripheral surface of the cylindrical portion 6A of the second casing 6 are formed. The third passage 23 is disposed radially outward of the first passage 21 so as to surround the first passage 21. The second passage 22 communicates the lower ends of the first passage 21 and the third passage 23 with each other.

  A plurality of fins 25 project from the outer peripheral surface of the cylindrical portion 6 </ b> A of the second casing 6. The fin 25 enlarges the area of the outer surface of the 2nd casing 6, and there exists an effect which accelerates | stimulates the heat exchange with the 2nd casing 6 and an external heat source (external atmosphere).

  The third casing 7 has a cylindrical portion 7A and an end wall 7B that closes one end of the cylindrical portion 7A, and the other end of the cylindrical portion 7A is an open end. The third casing 7 is joined to the upper surface of the first casing 5 so that the open end communicates with the third hole 13. That is, the third casing 7 is disposed so that the axis of the cylindrical portion 7 </ b> A coincides with the axis of the third hole 13 and closes the third hole 13. Thereby, the chamber 27 is defined by the third casing 7 and the third hole 13.

  With the above configuration, the first passage 21, the second passage 22, the third passage 23, the second hole 12, the inlet passage 17, and the chamber 27 are provided inside the sealed container 2 including the first to third casings 5 to 7. A circulation path 28 that passes through the outlet passage 18 and the first hole 11 in order and reaches the first first passage 21 is formed. The circulation path 28 is branched into a plurality corresponding to each third casing 7 (eight in the present embodiment), and the first passage 21, the second passage 22, the third passage 23, and the first hole 11 are common portions. It becomes.

  A plurality of fins 31 project from the outer peripheral surface of the cylindrical portion 7 </ b> A of the third casing 7. The fin 31 expands the area of the outer surface of the third casing 7 and has an effect of promoting heat exchange between the third casing 7 and an external heat source (external atmosphere).

  The chamber 27 is provided with a solid electrolyte 33 that allows passage of alkali metal ions. In the present embodiment, the solid electrolyte 33 is a β-alumina solid electrolyte or a β ″ -alumina solid electrolyte that allows passage of sodium ions at a high temperature. The solid electrolyte 33 is made of a sintered material of β alumina or β ″ alumina.

  The solid electrolyte 33 has a cylindrical portion 33A and an end wall 33B that closes one end of the cylindrical portion 33A, and has a bottomed cylindrical shape with one end opened. The solid electrolyte 33 is joined to the first casing 5 so that the open end communicates with the outlet passage 18 opened at the bottom of the third hole 13. That is, the solid electrolyte 33 is joined to the bottom of the third hole 13 so as to close the outlet passage 18 opened to the chamber 27. In a state where the solid electrolyte 33 is joined to the first casing 5, the cylindrical portion 33 </ b> A of the solid electrolyte 33 is disposed concentrically with the cylindrical portion 7 </ b> A of the third casing 7, and the end wall 33 </ b> B of the solid electrolyte 33 is It arrange | positions so that the end wall 7B of this may be opposed via a space | gap. Accordingly, the chamber 27 is divided into an outer chamber 27A defined by the outer surface of the solid electrolyte 33 and the inner surfaces of the third casing 7 and the third hole 13, and an inner chamber 27B defined inside the solid electrolyte 33. Partitioned. The inlet passage 17 communicates with the outer chamber 27A, and the outlet passage 18 communicates with the inner chamber 27B.

  The solid electrolyte 33 has a plurality of convex portions 35 on the outer peripheral surface of the cylindrical portion 33A. The convex portion 35 is formed for the purpose of expanding the surface area of the outer peripheral surface of the cylindrical portion 33A. In the present embodiment, the convex portion 35 is a plate piece (fin) that protrudes outward from the outer peripheral surface of the cylindrical portion 33A, and extends in the circumferential direction of the outer peripheral surface and has an annular shape. The plurality of convex portions 35 are arranged with gaps therebetween in the axial direction of the cylindrical portion 33A.

  The inner peripheral surface of the cylindrical portion 33A of the solid electrolyte 33 is formed as a smooth (smooth) cylindrical surface (circumferential surface). That is, the inner peripheral surface of the cylindrical portion 33A is formed more smoothly than the outer peripheral surface. Here, a smooth surface or a smooth surface means a continuous surface including a curved surface, and means a surface having no steep irregularities such as ridges and valleys. In the present embodiment, the inner peripheral surface of the cylindrical portion 33A of the solid electrolyte 33 has a constant inner diameter at each portion in the axial direction. Since the solid electrolyte 33 has a constant inner diameter on the inner peripheral surface and a plurality of convex portions 35 on the outer peripheral surface, the thickness in the radial direction changes as the axial direction proceeds.

  A cathode (anode) 36 having conductivity and air permeability is provided on the inner peripheral surface of the cylindrical portion 33A of the solid electrolyte 33 and the inner surface of the end wall 33B. The cathode 36 is a thin film electrode such as molybdenum. The cathode 36 is formed in a porous shape (three-dimensional network structure) so that gas and liquid alkali metal can pass therethrough. The cathode 36 is formed by a known lamination technique such as sputtering. Thereby, the inner peripheral surface of the cylindrical portion 33 </ b> A of the solid electrolyte 33 and the inner surface of the end wall 33 </ b> B constitute a cathode side surface 37. The cathode 36 is provided so as to cover most of the inner peripheral surface of the cylindrical portion 33A and the inner surface (cathode side surface 37) of the end wall 33B, preferably the entire region. Thereby, the area of the cathode side surface 37 to which electrons are supplied by the cathode 36 is formed wider. The outer peripheral surface of the cylindrical portion 33A of the solid electrolyte 33, the outer surface of the convex portion 35, and the outer surface of the end wall 33B constitute an anode side surface 38. The surface area of the anode side surface 38 is preferably at least twice the surface area of the cathode side surface 37.

  One end of a conductive connection member (lead) 41 is connected to the cathode 36. The other end of the connection member 41 extends into the outlet passage 18, and extends to the outside through the first casing 5 from the outlet passage 18. In the present embodiment, the connecting member 41 includes a first connecting member 41A connected to the surface of the cathode 36, one end connected to the first connecting member 41A, and the other end extending into the outlet passage 18, And a second connecting member 41B extending from the passage 18 to the outside through the first casing 5.

  The first connecting member 41A is made of a porous (three-dimensional network structure) metal (foamed metal body) that has conductivity and allows gas and liquid alkali metals to pass through. The first connecting member 41A may be a metal porous material such as molybdenum, for example. The first connecting member 41A may be provided so as to occupy most of the inside (inner chamber 27B) of the cylindrical portion 33A.

  The second connecting member 41 </ b> B is a bulk metal body that has conductivity and is formed so that gas and liquid alkali metal cannot pass therethrough. The second connection member 41B may be a metal columnar body or wire containing, for example, molybdenum or nickel. One end of the second connection member 41B is inserted into the first connection member 41A and is electrically connected to the first connection member 41A. A seal 42 is provided at a portion where the second connecting member 41B penetrates the first casing 5 in order to prevent leakage of gas and liquid alkali metal. Conductive wiring 43 is provided at the outer end of the second connection member 41B. Accordingly, the cathode 36, the first connection member 41A, the second connection member 41B, and the wiring 43 are electrically connected. In other embodiments, the second connecting member 41B may be omitted, and the wiring 43 may be inserted inward of the first casing 5 and directly connected to the first connecting member 41A. In this case, the wiring 43 is formed so that gas and liquid alkali metal cannot pass through, and the gap with the first casing is sealed by the seal 42. Alternatively, the first connection member 41A may be formed as a thin film laminated so as to cover the cathode 36, and the second connection member 41B or the wiring 43 may be connected to the thin film-like first connection member 41A.

  The third casing 7 functions as an anode. The third casing 7 is provided with conductive wiring 44. One set of the third casing 7, the solid electrolyte 33, the cathode 36, and the wirings 43 and 44 constitute one cell 45. The wirings 43 and 44 are connected to other cells 45 in series or in parallel, and are connected to an external load (not shown).

  A wick pump 46 is provided in the third passage 23 of the second casing 6. The wick pump 46 is a transport means for transporting liquid by capillary force. The wick pump 46 may be a mesh wick, a fibrous wick, or a sintered metal wick that is a porous material. The wick pump 46 may be provided in the second hole 12 or the inlet passage 17 in addition to the third passage 23.

  The inside of the circulation path 28 is evacuated and filled with alkali metal. In the present embodiment, sodium that can pass through β-alumina solid electrolyte or β ″ alumina solid electrolyte when ionized is used as an alkali metal.

  The plurality of third casings 7 are exposed to a high temperature heat source and function as the heat receiving part 51, and the second casing 6 is exposed to a low temperature heat source and functions as the heat radiating part 52. The circulation path 28 is disposed so as to pass through the third casing 7 that is the heat receiving portion 51 and the second casing 6 that is the heat radiating portion 52. The third casing 7 and the chamber 27 are heated by receiving heat, and the second casing 6, the first passage 21, the second passage 22, and the third passage 23 are discharged from the third casing 7 and the chamber 27 by releasing heat. It becomes cooler. During operation, the temperatures of the second casing 6, the first passage 21, the second passage 22, and the third passage 23 are higher than the melting point of the alkali metal and lower than the boiling point. In operation, the temperature of the third casing 7 and the chamber 27 is preferably equal to or higher than the boiling point of the alkali metal.

  Next, the operation of the alkali metal thermoelectric converter 1 configured as described above will be described. The alkali metal thermoelectric converter 1 receives heat at the heat receiving portion 51 and releases heat at the heat radiating portion 52, so that the alkali metal in the circulation path 28 flows into the first passage 21, the second passage 22, the second passage. The three passages 23 exist mainly as a liquid, and the outer chamber 27A exists as a mixture of liquid and gas. As a result, the alkali metal evaporates on the inner chamber 27B side of the wick pump 46, and as a result, the wick pump 46 transports the liquid alkali metal to the outer chamber 27A side by capillary force. As a result, the alkali metal is supplied to the anode side surface 38 of the solid electrolyte 33.

  The liquid and gaseous alkali metals emit electrons at the anode side surface 38 and enter the solid electrolyte 33 as alkali metal ions. The electrons emitted from the anode side surface 38 flow to the wiring 44 through the liquid alkali metal and the third casing 7.

  The alkali metal ions in the solid electrolyte 33 receive electrons from the cathode 36 at the cathode side surface 37 and become gaseous alkali metal. The gaseous alkali metal reaches the first passage 21 via the cathode 36, the inner chamber 27B, the outlet passage 18, and the first hole 11, and the temperature is lowered to become a liquid. The liquid alkali metal reaches the third passage 23 via the second passage 22, and is transported to the outer chamber 27 </ b> A side by the wick pump 46.

  In the alkali metal thermoelectric converter 1 configured as described above, since the surface area of the anode side surface 38 of the solid electrolyte 33 is increased by the plurality of convex portions 35, the contact area between the alkali metal and the anode side surface 38 increases. . The alkali metal emits electrons and enters the solid electrolyte 33. Among the alkali metals existing in the vicinity of the anode side surface 38, those having a certain or higher kinetic energy emit electrons and enter the solid electrolyte 33. It is thought that it will enter. Therefore, as the contact area between the alkali metal and the anode side surface 38 is increased, the probability that an alkali metal having high kinetic energy is located in the vicinity of the anode side surface 38 is increased, so that the alkali metal ions that enter the solid electrolyte 33. The number of increases. Thereby, the output of the alkali metal thermoelectric converter 1 increases. When the output of the alkali metal thermoelectric converter 1 increases, the temperature of the heat receiving portion 51 can be lowered and the size of the alkali metal thermoelectric converter 1 can be reduced.

  On the other hand, since the cathode side surface 37 is formed more smoothly than the anode side surface 38, it is easy to form the cathode 36 on the cathode side surface 37, and disconnection of the cathode 36 or poor contact between the cathode 36 and the cathode side surface 37. Etc. can be prevented. In addition, the solid electrolyte 33 can be easily molded, and the solid electrolyte 33 can be easily pulled out from the mold.

  According to the applicant's research, in a conventional alkali metal thermoelectric converter, the amount of ions passing through the solid electrolyte may be significantly less than the amount of ion vacancies in the solid electrolyte. Therefore, it is considered that the amount of alkali metal ions passing through the solid electrolyte has a larger influence on the process in which alkali metal emits electrons and enters the anode side surface than the process in which alkali metal ions receive electrons and exit from the cathode side surface. Therefore, it is considered that increasing the surface area of the anode side surface 38 rather than the cathode side surface 37 has a higher effect of increasing the amount of alkali metal ions passing through the solid electrolyte 33. Therefore, the cathode side surface 37 is smoothed, and the projections 35 are provided on the anode side surface 38, thereby facilitating the formation of the cathode on the cathode side surface and the amount of alkali metal ions that pass through the fixed electrolyte (the alkali metal ions on the anode side surface 38). Increase in the amount of electrons emitted from the substrate. Since it is more effective to increase the amount of alkali metal ions passing through the solid electrolyte 33 than to increase the surface area of the anode side surface 38 than to the cathode side surface 37, the surface area of the anode side surface 38 is preferably larger than the surface area of the cathode side surface 37. The above effects become remarkable. The surface area of at least the anode side surface 38 is preferably at least twice the surface area of the cathode side surface 37.

  The convex portion 35 can be efficiently expanded in surface area by being formed in a plate shape (fin shape).

  In the first embodiment, the wick pump 46 is used as a transportation means for transporting the liquid alkali metal existing in the first to third passages 21 to 23 to the outer chamber 27A. It is good also as an electromagnetic pump which conveys the said alkali metal by an induction effect. The electromagnetic pump may be provided on the outer peripheral surface of the cylindrical portion 6 </ b> A of the second casing 6.

(Second Embodiment)
The alkali metal thermoelectric converter 60 according to the second embodiment is configured to transport an alkali metal using inertial force. FIG. 3 is a cross-sectional view of an alkali metal thermoelectric converter according to the second embodiment. As shown in FIG. 3, the alkali metal thermoelectric converter 60 according to the second embodiment omits the wick pump 46 and is sealed instead of the alkali metal thermoelectric converter 1 according to the first embodiment. A mechanism for rotating the container 2 is provided. In the alkali metal thermoelectric converter 60, the same components as those of the alkali metal thermoelectric converter 1 are denoted by the same reference numerals and description thereof is omitted.

  A rotating shaft 61 that is coaxial with the axis A is provided on the end wall 6B of the second casing 6 so as to protrude downward. The rotating shaft 61 is connected to the output shaft 64 of the electric motor 63 by a coupling 62. A casing 65 of the electric motor 63 is fixed to the base 66. The electric motor 63 rotates the sealed container 2 about the axis A. The chamber 27 is located farther from the axis A than the first to third passages 23 in the radial direction of the axis A.

  An anode slip ring 68 and a cathode slip ring 69 are attached to the outer peripheral portion of the rotating shaft 61 via an electrical insulating member 67. The anode slip ring 68 and the cathode slip ring 69 are connected to wirings 43 and 44 of the respective cells 45 connected in series or in parallel. Each of the anode slip ring 68 and the cathode slip ring 69 has a structure in which current collecting brushes (not shown) are individually slidably contacted to collect current from the rotating sealed container 2 to the outside (fixed side). . An external load (not shown) is connected to the current collecting brush.

  In the alkali metal thermoelectric converter 60 according to the second embodiment, the sealed container 2 is rotated about the axis A by the electric motor 63, thereby generating centrifugal force. Here, the alkali metal is transported from the third passage 23 to the outer chamber 27A through the second hole 12 and the inlet passage 17 by centrifugal force. The throttle portion 15 prevents the alkali metal present in the first passage 21 from flowing back to the first hole 11 side.

  In the alkali metal thermoelectric converter 1 according to the second embodiment, the inner surface of the partition wall 14 is tapered so as to increase in diameter toward the protruding end side (lower end side), and the inner wall of the cylindrical portion of the second casing 6 is opened. It is good also as a taper shape so that a diameter may be expanded, so that it goes to an end side (upper end side). According to these configurations, when the sealed container 2 is rotated about the axis A, the liquid alkali metal that is to be moved radially outward by the inertial force is guided to the inner surface side of the partition wall 14 and moved downward. And is guided to the inner peripheral surface of the cylindrical portion 6A of the second casing 6 and moves upward. By these actions, transport of the liquid alkali metal to the outer chamber 27A side is promoted.

  FIG. 4 is a schematic view in which an alkali metal thermoelectric converter 60 according to the second embodiment is arranged in an automobile exhaust system. As shown in FIG. 4, the 2nd casing 6 which is the heat receiving part 51 of the airtight container 2 is arrange | positioned in the main channel | path 71 of the exhaust pipe 70 of an internal combustion engine, and heat exchange is possible with the exhaust gas which is a high temperature fluid. Yes. Thereby, the third casing 7 is heated by the exhaust gas.

  The second casing 6 that is the heat radiating portion 52 of the sealed container 2 is disposed in a bypass passage 72 that is disposed in parallel with the main passage 71. The exhaust gas inlet 74 of the bypass passage 72 is opened and closed by an opening / closing valve 75. An external air intake 76 is formed in the bypass passage 72, and a reed valve 77 for external air intake is attached to the external air intake 76. Seal members 78 and 79 are provided between the exhaust pipe 70 and the first casing and between the exhaust pipe 70 and the rotary shaft 61 to prevent exhaust leakage.

  When the alkali metal thermoelectric converter 60 is started, the pre-heating of the second casing 6 is performed by opening the on-off valve 75 and allowing exhaust gas to flow through the bypass passage 72 and heating the heat radiating portion 52 with the exhaust gas. The preheating of the heat radiating portion 52 is performed to liquefy the alkali metal that has become solid in the first to third passages 21 to 23. After the preheating of the heat dissipating part 52 is completed, the on-off valve 75 is closed, the outside air is taken into the bypass passage 72 by the reed valve 77, and the heat dissipating part 52 is kept at a lower temperature than the heat receiving part 51. The appropriate temperature of the heat radiating unit 52 is determined by the temperature of the heat receiving unit 51 and may be about 100 to 500 ° C. With the above configuration, the alkali metal thermoelectric converter 60 operates using the exhaust gas of the internal combustion engine as a heat source.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, the convex portions 81 formed on the outer peripheral surface (anode side surface 38) of the cylindrical portion 33A of the solid electrolyte 33 project radially from the outer peripheral surface of the cylindrical portion 33A as shown in FIG. The shape may extend in the direction.

  Moreover, the convex part 35 may be formed in the shape which protrudes in the shape of a column from the outer peripheral surface of 33 A of cylindrical parts to radial direction outward, or hemispherical. Alternatively, the outer peripheral surface of the cylindrical portion 33A may be curved into a corrugated shape to serve as a protruding portion. Alternatively, a plurality of grooves and recesses may be provided on the outer peripheral surface of the cylindrical portion 33A, and a base surface portion surrounded by the grooves and recesses may be used as the protrusions 35. Thus, the outer peripheral surface of the cylindrical portion 33A only needs to have a convex portion or a concave portion that can enlarge the surface area.

  The inner surface of the cylindrical portion 33 </ b> A serving as the cathode side surface 37 is not limited to the cylindrical surface, and may be composed of a plurality of flat surfaces. For example, in the case where a hole having a prism shape such as a triangle or a quadrangle is formed as an inner hole in the solid electrolyte 33, the inner surface serving as the cathode surface of the solid electrolyte is formed from a plurality of planes.

  Further, when the solid electrolyte 33 is not formed into a cylindrical shape as in the above-described embodiment, but is formed into a flat plate shape, it is preferable that a convex portion is provided on the anode side surface 38 and the cathode side surface 37 is formed flat.

  DESCRIPTION OF SYMBOLS 1,60 ... Alkali metal thermoelectric converter, 2 ... Sealed container, 5 ... 1st casing, 6 ... 2nd casing, 7 ... 3rd casing, 11 ... 1st hole, 12 ... 2nd hole, 13 ... 3rd Hole: 14 ... Partition, 17 ... Inlet passage, 18 ... Outlet passage, 21 ... First passage, 22 ... Second passage, 23 ... Third passage, 27 ... Chamber, 27A ... Outer room, 27B ... Inner room, 28 ... Circulatory path 33 ... solid electrolyte 33A ... cylindrical part 33B ... end wall 35 ... convex part 36 ... cathode 37 ... cathode side face 38 ... anode side face 41 ... connecting member 41A ... first connecting member 41B ... 2nd connection member, 43 ... Wiring, 44 ... Wiring, 45 ... Cell, 46 ... Wick pump, 51 ... Heat receiving part, 52 ... Heat radiation part, 61 ... Rotating shaft, 63 ... Electric motor, A ... Axis

Claims (10)

An alkali metal thermoelectric converter,
A sealed container having a heat receiving portion, a heat radiating portion, and an alkali metal circulation path formed so as to pass through the heat receiving portion and the heat radiating portion;
A solid electrolyte that allows passage of alkali metal ions and is provided so as to delimit the circulation path in the heat receiving part, and has an anode side surface and a cathode side surface;
An anode provided on the side surface of the anode;
A cathode provided on the side surface of the cathode;
Transport means for transporting the alkali metal in the circulation path to the anode side surface side of the solid electrolyte,
The alkali metal thermoelectric converter, wherein the anode side surface has a plurality of convex portions, and the cathode side surface is formed more smoothly than the anode side surface.   The alkali metal thermoelectric converter, wherein the convex portion has a plate-like shape protruding outward from the main body of the solid electrolyte. The circulation path includes a chamber having an inlet passage and an outlet passage in the heat receiving portion,
The solid electrolyte is formed in a cylindrical shape having an opening at one end and closed at the other end, and is disposed in the chamber so that the opening communicates with the outlet passage. 3. The alkali metal thermoelectric converter according to claim 1, wherein an alkali metal thermoelectric converter according to claim 1, wherein the alkali metal thermoelectric converter is divided into an outlet side and an outer surface is the anode side surface facing the inlet channel side, and an inner surface is the cathode side surface. .   The alkali metal thermoelectric converter according to claim 3, wherein the solid electrolyte is formed in a cylindrical shape, and an inner surface forming the side surface of the cathode is formed in a cylindrical surface.   5. The alkali metal thermoelectric converter according to claim 3, wherein the convex portion extends in a circumferential direction along an outer peripheral surface of the solid electrolyte and has an annular plate shape.   6. The alkali metal thermoelectric according to claim 3, wherein a portion defining the inlet passage side of the chamber includes a conductive material and constitutes the anode. 6. converter.   The alkali metal thermoelectric converter according to any one of claims 3 to 6, wherein the cathode is a porous body provided on a side surface of the cathode.   The alkali metal thermoelectric converter according to any one of claims 1 to 7, wherein the transport means is a wick provided in the circulation path.   The alkali metal thermoelectric converter according to any one of claims 1 to 7, wherein the transport means transports the alkali metal by centrifugal force by rotating the sealed container. .   The alkali metal thermoelectric converter according to any one of claims 1 to 7, wherein the transport means is an electromagnetic pump that transports the alkali metal by electromagnetic induction.

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