Patent Abstract:
A heat storage apparatus comprises a heat storage material accommodation cell for accommodating therein a heat storage material having an electricity conductive characteristic and configured to be electrically heated, and a fluid passageway for allowing a heat exchanging fluid to flow therethrough, the fluid passageway being adjacent to the heat storage material accommodation cell via a bulkhead. The heat storage material accommodation cell and the fluid passageway are put in a spiral configuration together with the bulkhead in a heat storage main body of the heat storage apparatus. Heat held in the heat storage material is transferred to the heat exchanging fluid so as to be taken out of the heat storage apparatus.

Full Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a heat storage apparatus of a type in which heat energy is taken out from a heat storage material which is electrically heated by a heat exchanging fluid. 
   2. Description of the Related Art 
   In recent years, a demand has been increasing that heat is stored using inexpensive power available late at night so that heat energy so stored is taken out for use in supplying hot water and heating rooms during the daytime, and in association with such a demand, there has been a tendency that high-performance heat storage apparatuses are demanded. 
   A heat-storage type heat exchanger is known as a heat storage apparatus in the related art (for example, in JP-A-11-264683 (paragraph [0012], FIG. 1)). 
   The related art will be described by reference to FIGS. 1A, 1B in the patent literature No. 1. 
     FIG. 13  is a drawing incorporated herein to illustrate what is illustrated in FIG. 1B of the patent literature No. 1, in the drawing, reference numeral  4  denotes a phase-changeable material, and reference numeral  3  denotes a fluid flow path. When a medium such as air is allowed to flow into the fluid flow path  3 , this medium absorbs heat energy that the phase changeable material  4  possesses. 
   There is a statement in lines 6 to 7 in paragraph “0012” in the patent literature No. 1 that states, “a number of quadrangular flow paths 3 are formed by ceramic walls 2 a .” 
     FIG. 14  is a drawing incorporated herein to illustrate what is illustrated in FIG. 1A of the patent literature No. 1. It is seen from the drawing that a ceramic honeycomb  2  which constitutes a heat storage element  1  is partitioned in a grid-like fashion and that a multiplicity of quadrangular flow paths  3  and quadrangular phase changeable material accommodation cells for accommodating phase changeable material are provided. 
   The heat exchanger, in the related art, constituted by the quadrangular flow paths and phase changeable material accommodation cells has the following problems. 
   1) Since a number of fluid passageways each having a quadrangular shape exist alternately, it is difficult to allow a heat exchanging fluid to flow into all the fluid passageways uniformly, and there happen to be caused locations where the heat exchanging fluid flows in such a large amount that heat exchanging is completed so quickly and, on the contrary, locations where the heat exchanging fluid flows in such a small amount that heat exchanging is not promoted, thereby making it difficult to obtain a high performance as a whole. 
   2) Since a number of quadrangular heat storage material accommodation cells exist alternately, the volume of each heat storage material accommodation cell becomes small, and therefore, when heat is taken out of the phase changeable heat storage material, an excessively cooling phenomenon is easy to occur, and therefore, a stable output cannot be obtain. 
     FIG. 15  is a drawing illustrating another problem inherent in the related art and corresponds to a partial view of  FIG. 14 , in which it is shown that phase changeable materials  4 ,  4  stored in quadrangular phase changeable material accommodation cells are placed adjacent to quadrangular flow paths  3 ,  3 . In order to store heat using power available late at night so that the heat so stored is taken out as heat energy during the daytime, the following are needed: a material having an electricity conductive characteristic is used for the phase exchangeable material  4 ; electrode plates  101 ,  101  for phase changing the phase changeable material  4  are provided in each of the phase changeable material accommodation cell; and a power supply  103  is connected to these electrode plates  101 ,  101  via lead wires  102 ,  102 . 
   Namely, the electrode plates  101 ,  101  are energized from the power supply  103  late at night so as to phase change the phase changeable material  4 . During the daytime, energizing by the power supply  103  is halted, and a heat exchanging fluid such as air or water is allowed to flow through the flow path  3  so that heat is absorbed by the heat exchanging fluid to thereby take out heat energy. 
   However, the lead wire  102  needs to be drawn out from each electrode plate  101 , and taking for example a case shown in  FIG. 14 , since the phase changeable material  4  is accommodated in 16 cells which are partitioned in a 4×4 fashion, 32 lead wires  102 , which results from 16×2, need to be drawn out as a whole, and since such a large number of lead wires  102  need to be laid out, the production cost of the apparatus is increased and the feed control becomes difficult. 
   Namely, since a number of quadrangular heat storage material accommodation cells exist in an alternate fashion, in order to directly heat the heat storage material using Joule heat, electrode plates need to be placed in all the heat storage material accommodation cells and wiring needs to be installed for the electrode plates so placed. The layout of electric wires becomes complex very much, and this increases the number of components involved, as well as the production costs. 
   SUMMARY OF THE INVENTION 
   An object of the invention is to provide a heat storage apparatus which can enhance the heat exchanging performance and simplify the layout of electric wires. 
   With a view to attaining the object, according to a first aspect of the invention, there is provided a heat storage apparatus comprising: a heat storage material accommodation cell for accommodating therein a heat storage material having an electricity conductive characteristic and configured to be electrically heated; and a fluid passageway for allowing a heat exchanging fluid to flow therethrough, the fluid passageway being adjacent to the heat storage material accommodation cell via a bulkhead, wherein heat held in the heat storage material is transferred to the heat exchanging fluid so as to be taken out of the heat storage apparatus, and wherein the heat storage material accommodation cell and the fluid passageway are put in a spiral configuration together with the bulkhead in a heat storage main body of the heat storage apparatus. 
   Since the heat storage material accommodation cell and the fluid passageway are put in the spiral configuration, the numbers of heat storage material accommodation cells and fluid passageways can be decreased largely. By decreasing the numbers of cells and passageways like this, volumes of each heat storage material accommodation cell and fluid passageway can be increased largely, and in conjunction with these volume increases, the flow of the fluid can be easily uniformed, whereby the occurrence of an excessively cooling phenomenon of the heat storage material can be prevented, thereby making it possible to enhance the heat exchanging performance. 
   Since the number of the heat storage material accommodation cells can be decreased largely, the number of electrode plates which are attached to the cells also can be decreased largely, which leads to a simple layout of electric wires, whereby the production costs can be easily decreased. 
   According to a second aspect of the invention, the heat storage material has a property in which electric resistance increases drastically when the heat storage material changes its phase from a solid to a liquid. 
   Heat storing is completed by changing the phase from a solid to a liquid. In the event that the electric resistance is designed to increase drastically when the phase so changes, an autonomous control becomes possible in which a current value becomes small, and a temperature-electricity control device such as a thermostat can be omitted. In case such a control part can be saved, a further decrease in production costs can be attempted to be attained. 
   According to a third aspect of the invention, the heat storage main body is a cylindrical body in which the heat storage material accommodation cell and the fluid passageway are made to open in both end faces thereof, and both the end faces of the cylindrical body are closed with a top lid and a bottom lid, respectively. 
   In case the heat storage main body is the cylindrical body in which the heat storage material accommodation cell and the fluid passageway are made to open in both end faces thereof, the heat storage main body can be produced by an extrusion forming process, and the production cost of the heat storage main body can be decreased. 
   According to a fourth aspect of the invention, the heat storage main bodies are arranged in series via an intermediate plate. 
   Since the heat storage main bodies can be connected together in series by using the intermediate plate, the heat storage apparatus can be arranged freely according to specifications thereof. 
   According to a fifth aspect of the invention, an energizing lead pattern is provided on at least one of the lids, the lead pattern including a spiral pattern. 
   According to a sixth aspect of the invention, an energizing lead pattern is provided on at least one of the lids and the intermediate plate, the lead pattern including a spiral pattern. 
   In the event that the lead patterns are provided on at least one of the lids and intermediate plate, a highly reliable wiring can be installed at low costs. In addition, in the event that the spiral pattern is included in the lead patterns, since the spiral pattern is allowed to function as an inductance, power factor can be attempted to be improved. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is an exploded perspective view of a heat storage apparatus according to the invention; 
       FIG. 2  is an extracted view of the heat storage apparatus according to the invention; 
       FIG. 3  is an exploded perspective view of a heat storage main body according to the invention; 
       FIG. 4  is a plan view of the heat storage main body according to the invention; 
       FIG. 5  is an explanatory diagram explaining how a heat exchanging fluid is allowed to flow and how the heat storage material is sealed in; 
       FIG. 6  is an explanatory diagram illustrating a construction for energizing an electrode plate from an external location; 
       FIG. 7  is a diagram illustrating a relationship between lead patterns, bolts and electrode plates which are adopted in the invention; 
       FIG. 8  is an explanatory diagram illustrating the function of the heat storage apparatus according to the invention; 
       FIG. 9  is an electric circuit diagram with a single-phase alternating current being used as a power supply; 
       FIG. 10  is a lead pattern preferred for a three-phase alternating current; 
       FIG. 11  is an electric circuit diagram with a three-phase alternating current being used as a power supply; 
       FIG. 12  is an exploded perspective view of a multi-stage heat storage apparatus according to the invention; 
       FIG. 13  is a diagram illustrating what is shown in FIG. 1B in JP-A-11-264683. 
       FIG. 14  is a diagram illustrating what is shown in FIG. 1A in JP-A-11-264683. 
       FIG. 15  is a diagram illustrating another problem inherent in the related art. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An embodiment of the invention will be described below based on the accompanying drawings. Note that the drawings are to be seen in directions in which reference numerals are oriented. 
     FIG. 1  is an exploded perspective view of a heat storage apparatus according to the invention, and the heat storage apparatus  10  includes a cylindrical heat storage main body  20 , a top lid  40  placed to cover a top side of the heat storage main body  20 , a bottom lid  50  placed to close a bottom side of the heat storage main body  20  and retaining machine screws  61  . . . ( . . . denotes plurality). 
   A fluid inlet  41  for a heat exchanging fluid is provided in the center of the top lid  40 , and a spiral lead pattern  42  is provided in such a manner as to surround the fluid inlet  41 . Then, a ring-like lead pattern  43  is provided in such a manner as to surround the spiral lead pattern  42 , and three heat storage material injecting ports  44 ,  45 ,  46  are provided in such a manner as to surround the ring-like lead pattern  43 . 
   The lead patterns  42 ,  43  can be formed, respectively, on the top lid  40  and the bottom lid  50  which have an electricity insulation characteristic by way of a vacuum plating process or an electroless plating process. 
   Three fluid outlets  51  for the heat exchanging fluid are provided in the bottom lid  50 . 
   A flexible resin such as EPDM (ethylene propylene diene rubber) is placed over a bottom side of the top lid  40  and a top side of the bottom lid  50  so as to secure a gastightness with the heat storage main body  20 . 
   While the construction of the cylindrical heat storage main body  20  will be described next, for the sake of promotion of understanding, a description will first be made by reference to  FIG. 2  (an extracted view) and  FIG. 3  (an exploded view) 
     FIG. 2  is an extracted view of the heat storage main body  20  according to the invention and illustrates a construction in which a first heat storage material accommodation cell  22  which is spiral is provided in a cylindrical body, a first-a electrode plate  23   a  and a first-b electrode plate  23   b  are disposed in parallel in the first heat storage material accommodation cell  22 , and a fist-a bolt  24   a  and a first-b bolt  24   b  are brought into contact with the first-a electrode plate  23   a  and the first-b electrode plate  23   b , respectively. 
     FIG. 3  is an exploded view of the heat storage main body according to the invention and illustrates that the first spiral heat storage material accommodation cell  22 , a second spiral heat storage material accommodation cell  25  and a third spiral heat storage material accommodation cell  26  are provided in the cylindrical body  21  with their phases being shifted through 120° from one another. Then, the heat storage main body  10  is constructed by inserting the first-a electrode plate  23   a  and the first-b electrode plate  23   b  into the first heat storage material accommodation cell  22  from thereabove, inserting a second-a electrode plate  27   a  and a second-b electrode plate  27   b  into the second heat storage material accommodation cell  25  from thereabove, and inserting a third-a electrode plate  28   a  and a third-b electrode plate  28   b  into the third heat storage material accommodation cell  26  from there above. Note that each electrode plate may be formed on a bulkhead, which will be described later on, by way of the vacuum plating process or the electroless plating process. 
     FIG. 4  is a plan view of the heat storage main body according to the invention, and the cylindrical body  21  is partitioned by a group of extremely thin bulkheads. This group of bulkheads will be described in detail. 
   Firstly, a first spiral inner bulkhead  31   a  is provided in order for the first-a electrode plate  23   a  to follow there along. This first inner bulkhead  31   a  constitutes a spiral which turns one and a half rotations as with the first heat storage material accommodation cell  22  shown in  FIG. 2 . 
   Then, a first outer bulkhead  31   b  is provided outwardly of the first inner bulkhead  31   a  so provided with a gap “t” being provided therebetween. 
   An outer end portion of the first inner bulkhead  31   a  and an outer end portion of the first outer bulkhead  31   b  are connected to each other by way of a U-shaped wall  32 . An inside diameter of this U-shaped wall  32  is set to about 2×t. 
   Similarly, an inner end portion of the first inner bulkhead  31   a  and an inner end portion of the first outer bulkhead  31   b  are connected to each other by way of a U-shaped wall  33 . An inside diameter of this U-shaped wall  33  is set to about 3×t. 
   Heat exchanging fluid tends to stay longer or stop in corner portions when compared with other locations of the flow passageway. Then, by setting the inside diameters of the U-shaped walls  32 ,  33  to the (2 to 3)×t, heat exchanging fluid is prevented from staying longer or stopping thereat, whereby the heat exchanging fluid is devised to flow uniformly. 
   Thus, the first inner bulkhead  31   a  and the first outer bulkhead  31   b  together constitutes a first fluid flow passageway  34  having the gap “t”. 
   In similar manners, a second fluid passageway  36  is constituted by a second inner bulkhead  35   a  and a second outer bulkhead  35   b , and a third fluid passageway  38  is constituted by a third inner bulkhead  37   a  and a third outer bulkhead  37   b.    
   Reference numerals  39  . . . denote heat insulation cells which are provided as required, and the heat insulation cell may be constituted by a space or may be filled with a heat insulation material. 
   The cylindrical body  21  is produced from materials having a good electrical insulation characteristic by way of extrusion forming, injection molding, shaping, sintering or other processes. Resins such as PE (polyethylene), PP (polypropylene), PPS (polyphenylene sulfide), and PET (polyethylene terephthalate) and ceramics are suitable as the materials having a good electrical insulation characteristic. 
     FIG. 5  is an explanatory diagram illustrating how the heat exchanging fluid is allowed to flow and how the heat storage material is sealed. Note that for the sake of conveniences in explanation, the heat storage main body  20  and the top lid  40  are illustrated as being separated from each other. 
   When the heat exchanging fluid is supplied from the fluid inlet  41  in the center of the top lid  40 , the heat exchanging fluid so supplied comes into abutment with the U-shaped walls  33  . . . which form together a Y shape is then divided into three streams as indicated by arrows so as to flow into the first to third fluid passageways  34 ,  36 ,  38 . Having passed through the first to third fluid passageways  34 ,  36 ,  38 , the heat exchanging fluid flows out from the fluid outlets  51  (refer to  FIG. 1 ) in the bottom lid  50 . 
   On the other hand, a heat storage material  71  (refer to  FIG. 8 ) is injected from the heat storage material injection port  45  into the second heat storage material accommodation cell  25 . The heat storage material is injected from the heat storage material injection port  44  into the first heat storage material accommodation cell  22  and is also injected from the heat storage material injection port  46  into the third heat storage material accommodation cell  26 . 
   The heat injection storage material  71  to be injected is a material which can phase change from a solid to a liquid and conduct electricity and which includes charge carriers which are free electrons, ions or holes. To be specific, suitable examples are a material in which graphite is mixed and dispersed in paraffin and a material in which a conductor is mixed and dispersed in a heat storage material of a sugar alcohol system such as erythritol. 
   It is preferable to use a heat storage material having a PTC (Positive Temperature Coefficient) property in which electric resistance increases largely when a phase change from a solid to a liquid occurs. 
   A heat storage is completed when a phase change from a solid to a liquid occurs. In case electric resistance is designed to increase drastically when such a phase change occurs to complete a heat storage, an autonomous control in which the current value becomes small becomes possible, whereby a temperature-electricity control device such as a thermostat can be saved. In case such a control device can be saved, a further reduction in the production costs can be attempted. 
     FIG. 6  is an explanatory diagram illustrating a construction for energizing the electrode plates from the outside, the first-a bolt  24   a  is suspended from the ring-like lead pattern  43  on the top lid  40  so as to be brought into contact with the first-a electrode plate  23   a . In addition, the first-b bolt  24   b  is suspended from the spiral lead pattern  42  on the top lid  40  so as to be brought into contact with the first-b electrode plate  23   b.    
   Similarly, a second-a bolt  72   a  suspended from the ring-like lead pattern  43  is brought into contact with the second-a electrode plate  27   a , and a second-b bolt  72   b  suspended from the spiral lead pattern  42  is brought into contact with the second-b electrode plate  27   b.    
   Furthermore, a third-a bolt  73   a  suspended from the ring-like lead pattern  43  is brought into contact with the third-a electrode plate  28   a , and a third-b bolt  73   b  suspended from the spiral lead pattern  42  is brought into contact with the third-b electrode plate  28   b.    
     FIG. 7  is a diagram illustrating a relationship between the lead pattern adopted in the invention, the bolt and the electrode plate, in which, for example, the first-a bolt  24   a  is illustrated as being suspended from the ring-like lead pattern  43 , so that the bolt  24   a  is brought into contact with the first-a electrode plate  23   a . Since the same relationship results with respect to the other bolts, the description thereof will be omitted herein. 
     FIG. 8  is a diagram describing the function of the heat storage apparatus according to the invention. In order to facilitate the description, only the first heat storage material accommodation cell  22  will be described. 
   Firstly, late at night, a single-phase alternating current power supply  74  is connected to the first-a electrode plate  23   a  and the first-b electrode plate  23   b  of the first heat storage material accommodation cell  22 . Then, electric current conducts to the heat storage material  71  via the pair of electrode plates  23   a ,  23   b , and the temperature of the heat storage material  71  increases due to Joule heat. In the invention, since the sufficiently large electrode plates  23   a ,  23   b  are disposed at a small interval, it is possible to generate Joule heat uniformly in the heat storage material  71 . 
   Then, the phase of the heat storage material  71  is changed from a solid to a liquid at a point where the temperature of the heat storage material  71  has reached its fusing point, whereby a large magnitude of energy can be stored as latent heat. 
   Thereafter, feeding is stopped and the energy so stored will be ready for use during the daytime. 
   During the daytime, a heat exchanging fluid (air or water) is allowed to flow into the first fluid passageway  34  as required. Then, the heat exchanging fluid takes heat away from the heat storage material  71  via the bulkhead and the temperature of the heat exchanging material  71  itself is increased. Thus, the energy is taken out from the heat exchanging fluid to the outside for use as a heat energy for supplying hot water or heating rooms. 
   Thus, while the first heat storage material accommodation cell  22  and the first fluid passageway  34  have been described above, a similar description will be made with respect to the second and third heat storage cells  25 ,  26  and the second and third fluid passageways  36 ,  38 . 
     FIG. 9  is an electric circuit diagram with a single-phase alternating current being used as a power supply, and since an “a” line  76  corresponds to the ring-like lead pattern  43  (refer to  FIG. 1 ), a “b” line  77  and an inductance  78  correspond to the spiral lead pattern  42  (refer to  FIG. 1 ), resistors  79  . . . correspond to the heat storage material  71  (refer to  FIG. 8 ), and dielectrics  81  . . . correspond to the electrode plates  23   a ,  23   b ,  27   a ,  27   b ,  28   a ,  28   b , a circuit shown in the drawing can be drawn. 
   The spiral pattern is included in the lead pattern, and since this spiral pattern can be made to function as an inductance, the improvement in power factor can be attempted. 
   While the single-phase alternating current is used in the example that has been described heretofore, the single-phase alternating current can be replaced by a three-phase alternating current. 
     FIG. 10  is a lead pattern diagram which is preferred for a case where a three-phase alternating current is used as a power supply, and a small ring-like lead pattern  43  is disposed on the top lid  40 , and large ring-like lead patterns  42 A,  42 B,  42   c  are disposed in such a manner as to surround the small ring-like lead pattern  43 . 
     FIG. 11  is an electric circuit diagram with a three-phase alternating current being used as a power supply, and the spiral lead pattern  42 A described in  FIG. 10  is replaced by an inductance  78 A in  FIG. 11 . Similarly, the spiral lead patterns  42 B,  42 C described in  FIG. 10  are replaced by inductances  78 B,  78 C in  FIG. 11 , and the power supply is replaced by a three-phase alternating current power supply  82 . From this, an electric circuit diagram as shown in  FIG. 11  can be drawn. 
   In a case where there are three heat storage accommodation cells as with the embodiment, this is suitable for feeding with the three-phase alternating current power supply  82 . 
     FIG. 12  is an exploded perspective view of a multi-stage heat storage apparatus according to the invention, in which a heat storage apparatus  10 B can be constructed into multiple stages comprising two or more stages by a top lid  40 , an upper heat storage main body  20 A, an intermediate plate  83 , a lower heat storage main body  20 B and a bottom lid  50 . While the heat storage main bodies  20 A,  20 B are identical with the heat storage main body  20 , the suffixes A, B are imparted to clarify their positions. 
   Heat storage material passing holes  84 ,  84 ,  84  and fluid passing openings  85 ,  85 ,  85  are provided in the intermediate plate  83 . Furthermore, a lead pattern is provided, as required, on the intermediate plate  83  having an electrical insulating property. 
   A flexible resin such as EPDM (ethylene propylene diene rubber) is placed over top and bottom sides of the intermediate plate  83  so as to secure gastightness between the heat storage main bodies  20 A,  20 B. 
   Note that while, in this embodiment, there are provided three heat storage material accommodation cells, with the single-phase alternating current being used as a power supply, there may be provided one, two or four heat storage material accommodation cells. With the three-phase alternating current being used as a power supply, there maybe provided heat storage material accommodation cells in multiples of three such as three, six or nine cells. Consequently, the heat storage material accommodation cell that is formed in the heat storage main body may be formed into at least a spiral configuration, and the number of cells is arbitrary. 
   In addition, the retaining machine screw may be replaced by a bolt which are longer than the length of the cylindrical body and a pair of nuts which are screwed onto both end portions of the bolt. 
   Alternately, neither retaining screw nor bolt may be used, and instead, there may be caused no problem even if the top lid, the bottom lid and the intermediate plate are integrally bonded together with the heat storage main body. For such an integral bonding, ultrasonic fusing, laser-beam fusing, brazing, bonding with an adhesive or any other processes can be used. 
   The invention constructed as has been described heretofore can exhibit the following advantages. 
   According to the first aspect of the invention, since the heat storage material accommodation cell and the fluid passageway are put in the spiral configuration, the numbers of heat storage material accommodation cells and fluid passageways can be decreased largely. By decreasing the numbers of cells and passageways like this, the volumes of each heat storage material accommodation cell and fluid passageway can be increased largely, and in conjunction with these volume increases, the flow of the fluid can be easily uniformed, whereby the occurrence of an excessively cooling phenomenon of the heat storage material can be prevented, thereby making it possible to enhance the heat exchanging performance. 
   Since the number of the heat storage material accommodation cells can be decreased largely, the number of electrode plates which are attached to the cells also can be decreased largely, which leads to a simple layout of electric wires, whereby the production costs can be easily decreased. 
   According to the second aspect of the invention, the heat storage material has the property in which electric resistance increases drastically when the heat storage material changes its phase from a solid to a liquid. 
   Heat storing is completed by changing the phase from a solid to a liquid. In the event that the electric resistance is designed to increase drastically when the phase so changes, an autonomous control becomes possible in which the current value becomes small, and the temperature-electricity control device such as a thermostat can be omitted. In case such a control part can be saved, a further decrease in production costs can be attempted to be attained. 
   According to the third aspect of the invention, the heat storage main body is the cylindrical body in which the heat storage material accommodation cell and the fluid passageway are made to open in both end faces thereof, and both the end faces of the cylindrical body are closed with the top lid and the bottom lid, respectively. 
   In case the heat storage main body is the cylindrical body in which the heat storage material accommodation cell and the fluid passageway are made to open in both the end faces thereof, the heat storage main body can be produced by an extrusion forming process, and the production cost of the heat storage main body can be decreased. 
   According to the fourth aspect of the invention, the heat storage main bodies are arranged in series via the intermediate plate. 
   Since the heat storage main bodies can be connected together in series by using the intermediate plate, the heat storage apparatus can be arranged freely according to specifications thereof. 
   According to the fifth aspect of the invention, the energizing lead patterns are provided on at least one of the lids, the lead pattern including a spiral pattern. 
   According to the sixth aspect of the invention, the energizing lead patterns are provided on at least one of the lids and the intermediate plate, the lead pattern including a spiral pattern. 
   In the event that the lead patterns are provided on at least one of the lids and intermediate plate, a highly reliable wiring can be installed at low costs. In addition, in the event that the spiral pattern is included in the lead patterns, since the spiral pattern is allowed to function as an inductance, power factor can be attempted to be improved.

Technology Classification (CPC): 5