Abstract:
A fuel cell device comprising: two vertically arranged cylindrical fuel cells different in diameter, each comprising a solid-electrolyte layer having first and second surfaces, an anode layer formed on the first surface of the solid-electrolyte layer, and a cathode layer formed on the other surface of the solid-electrolyte layer. The two fuel cells are mutually arranged in such a manner that the anode layer of one of the fuel cells faces the anode layer of the other fuel cell with a predetermined space between them and the space extends vertically from a lower position to an upper position. A fuel supply unit is provided for supplying fuel into the space at the lower position thereof so that a flame is formed, in the space, in an upward direction in which the space extends.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a fuel cell device and, particularly, to a fuel cell device including at least two fuel cells, each having an anode layer on one side of a solid-electrolyte layer and a cathode layer on the other side of the solid-electrolyte layer.  
           [0003]    2. Description of the Related Art  
           [0004]    A fuel cell device for generating electric power having a fuel cell disposing in a flame has been proposed, for example, in Japanese Unexamined Patent Publication (Kokai) No. 6-196176.  
           [0005]    A fuel cell device described in the above-mentioned patent publication is simply shown in FIG. 10. The fuel cell device shown in FIG. 10 includes a cylindrical fuel cell  100  having a cylindrical solid-electrolyte layer of zirconia, on the inner circumference of which is formed with a cathode layer and on the outer circumference of which is formed with an anode layer.  
           [0006]    The fuel cell  100  is disposed so that the anode layer is located in a reducing flame area  106  of a fire flame  104  ignited by a burner  102 .  
           [0007]    According to the cylindrical fuel cell  100  disposed so that the anode layer is located in the reducing flame area  106 , electricity is generated by using oxygen in air fed by the convection due to the flame  104  to the inner circumference on which the cathode layer is formed, which oxygen is reacted with hydrocarbon, hydrogen, various radicals or others existing in the reducing flame area  106  to which the anode layer of the outer circumference is exposed.  
           [0008]    The fuel cell device shown in FIG. 10 needs no external electric power for heating the fuel cell component  100  and, therefore, it is possible for it to deal with an unexpected breakdown of electric power facilities or other problems.  
           [0009]    However, as the fuel cell device shown in FIG. 10 uses the reducing flame  106  of the flame  104 , it is necessary to bring the outer circumference of the fuel cell  100  into contact with the reducing flame  106  as widely as possible. For this purpose, the fuel cell  100  is disposed to be orthogonal to the flame  104 .  
           [0010]    Accordingly, as it is necessary to form the flame  104  along the outer circumference of the fuel cell  100 , the burner  102  becomes larger in size.  
           [0011]    In addition, when a plurality of fuel cells  100  are connected in series or parallel to each other to generate electric power, the burner  102  becomes furthermore larger, resulting in a further enlargement of the size of the fuel cell device.  
           [0012]    Further, as an amount of air fed by convection due to the flame  104  to the inner circumference of the fuel cell  100  disposed orthogonal to the flame  104  is not sufficient, it is necessary to forcibly feed air by a blower or another means for the purpose of feeding a sufficient amount of air to the inner circumference of the fuel cell  100 , which needs electric power for driving the blower. This is a problem in an unexpected breakdown of electric power.  
           [0013]    Also, as the outer circumference of the fuel cell  100  is heated by the flame  104 , only part of heat generated by the flame  104  is used for heating the fuel cell  100 , and most of heat is dissipated out of the fuel cell system. Accordingly, the heat efficiency for heating the fuel cell  100  becomes low.  
         SUMMARY OF THE INVENTION  
         [0014]    Accordingly, a problem to be solved by, and an object of, the present invention is to provide a fuel cell device using a flame capable of effectively using the heat of the flame and capable of feeding sufficient air to a cathode layer.  
           [0015]    The present inventors have studied to solve the above-mentioned problems in the prior art, and found that if a cylindrical fuel cell section consists of two cylindrical fuel cells different from each other in inner diameter and arranged concentric with each other so that an anode layer forming one fuel cell is located opposite to an anode layer forming the other fuel cell, it is possible to feed a sufficient amount of air to cathode layers formed in the respective cylindrical fuel cells by the convection due to the flame. Thus the present invention has been achieved by these inventors.  
           [0016]    According to the present invention, there is provided a fuel cell device comprising: at least two fuel cells, each comprising a solid-electrolyte layer having first and second surfaces, an anode layer formed on the first surface of the solid-electrolyte layer, and a cathode layer formed on the other surface of the solid-electrolyte layer; the at least two fuel cells being mutually arranged in such a manner the anode layer of one of the fuel cells faces the anode layer of the other fuel cell with a predetermined space between them and the space extends from a lower position to an upper position; and a fuel supply unit for supplying fuel into the space at the lower position thereof so that a flame is formed in the space in a direction in which the space extends.  
           [0017]    The at least two fuel cells may preferably have respective cylindrical-shapes, which are concentrically arranged in such a manner that the space defines an annular-shaped space between the anode layers of the adjacent two fuel cells.  
           [0018]    Otherwise, the at least two fuel cells have respective flat-shapes, which are arranged in parallel to each other in such a manner that the space defines a flat space having a predetermined width between the anode layers of the adjacent two fuel cells arranged in parallel.  
           [0019]    The fuel supply unit may be a gaseous fuel supply unit. Otherwise, the fuel supply unit is a liquid fuel supply unit. The anode layer is preferably made of a fired material mainly composed of NiO in which Li is contained in a solid solution.  
           [0020]    According to the inventive fuel cell device, the fuel supply unit is provided at a lower end of the space in which the anode layer forming one fuel cell of a fuel cell section is located opposite to the anode layer forming the other fuel cell thereof, so that the flame is formed upward in the extending direction of the anode layers. Thus, the burner can be formed small in size because it is unnecessary to form the flame along the fuel cell, as in the device known in the prior art.  
           [0021]    Further, as the flame is formed in the extending direction of the anode layer and the convection of air due to the flame also occurs in the flame-generating direction, it is possible to feed a sufficient amount of air to the cathode layer solely by the convection, and to eliminate the blower or the like for forcibly supplying air.  
           [0022]    As the flame is formed in a space in which the anode layers are located opposite to each other, it is possible to effectively use the heat of the flame for heating the fuel cells without providing additional means for heating the fuel cells.  
           [0023]    As described above, according to the inventive fuel cell device, since the burner becomes smaller in size and means for forcibly feeding air such as a blower and means for heating the fuel cells are eliminated, it is possible to form the fuel cell device smaller in size and simpler in production. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is a perspective view for illustrating a fuel cell section constituting a fuel cell device of this invention;  
         [0025]    [0025]FIG. 2 is a sectional view of the fuel cell section shown in FIG. 1;  
         [0026]    [0026]FIG. 3 is a sectional view for illustrating one embodiment of means for supplying gaseous fuel to the fuel cell section;  
         [0027]    [0027]FIG. 4 is a sectional view for illustrating one embodiment of means for supplying liquid fuel to the fuel cell section;  
         [0028]    [0028]FIG. 5 is a sectional view for illustrating two fuel cells connected in parallel to each other to constitute the fuel cell section shown in FIG. 1;  
         [0029]    [0029]FIG. 6 is a sectional view for illustrating two fuel cells connected in series to each other to constitute the fuel cell section shown in FIG. 1;  
         [0030]    [0030]FIGS. 7 and 8 are illustrations of another embodiment of a fuel cell section constituting another embodiment of a fuel cell device of this invention;  
         [0031]    [0031]FIG. 9 is a perspective view of a further embodiment of the present invention using plate type fuel cells; and  
         [0032]    [0032]FIG. 10 is a schematic view for illustrating a fuel cell device known in the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    One embodiment of a fuel cell section constituting the inventive fuel cell device is shown in FIG. 1. In the fuel cell section  10  shown in FIG. 1, two vertically arranged cylindrical fuel cells  10   a  and  10   b  different in inner diameter from each other are disposed concentric with each other with a space  14  between the two.  
         [0034]    As shown in FIG. 2, which is a sectional view of the fuel cell section  10 , each of the fuel cells  10   a  and  10   b  constituting the fuel cell section  10  is formed by laminating a solid-electrolyte layer  12   a , an anode layer  12   b  and a cathode layer  12   c  concentrically with each other.  
         [0035]    If the fuel cell  10   a  is smaller in inner diameter than the other fuel cell  10   b , the anode layer  12   b  is formed on the outer circumference of the solid-electrolyte layer  12   a  and the cathode layer thereof is formed on the inner circumference of the solid-electrolyte layer  12   a.    
         [0036]    On the other hand, if the fuel cell  10   b  is larger in inner diameter than the fuel cell  10   a , the anode layer  12   b  is formed on the inner circumference of the solid-electrolyte layer  12   a  and the cathode layer  12   c  is formed on the outer circumference of the solid-electrolyte layer  12   a.    
         [0037]    In such a manner, the anode layer  12   b  is formed on the outer circumference of the fuel cell  10   a , and the anode layer  12   b  is formed on the inner circumference of the fuel cell  10   b . Accordingly, in the fuel cell section  10  formed by inserting the fuel cell  10   a  having a smaller inner diameter into the fuel cell  10   b  having a larger inner diameter, a space  14  is obtained in which the anode layer  12   b  formed on the outer circumference of the fuel cell  10   a  is located opposite to the anode layer  12   b  formed on the inner circumference of the fuel cell  10   b.    
         [0038]    In this regard, the solid-electrolyte layers  12   a  forming the fuel cells  10   a  and  10   b  are preferably made of zirconium oxide partially stabilized by a third group element (in the Periodic Table) such as yttrium (Y) or scandium (Sc), or cerium oxide doped with samarium (Sm) or gadolinium (Gd).  
         [0039]    Also, the anode layer  12   b  is preferably made of a fired material mainly composed of NiO in which Li is contained as a solid solution. This fired material is an-electro-conductive ceramic obtained by adding a Li compound, in a range from 1 to 15 mol % converted into Li 2 O equivalent, to NiO and firing the mixture.  
         [0040]    In the anode layer  12   b  thus formed, a metal such as rhodium, platinum, ruthenium, palladium, rhenium or iridium or oxide thereof is blended. According to the fuel cell device constituted by the fuel cells  10   a  and  10   b  having the anode layers  12   b  blended with such metal or oxide thereof, it is possible to exhibit a higher performance for generating electric power than a fuel cell device constituted by the anode layers  12   b  blended with no metal such as rhodium or others or oxide thereof.  
         [0041]    The metal such as rhodium, platinum, ruthenium, palladium, rhenium or iridium or oxide thereof is preferably blended in the anode layer  12   b  in a range from 1 to 50 wt % interms of the metal.  
         [0042]    It is possible to widen a contact area of the metal such as rhodium, platinum, ruthenium, palladium, rhenium or iridium or oxide thereof with a mixed fuel gas by blending 50 vol % or less of either one of samaria-doped ceria, scandia-stabilized zirconia and yttria-stabilized zirconia as an accessary constituent for the anode layer  12   b.    
         [0043]    Further, the cathode layer  12   c  is formed of manganese, gallium or cobalt oxide of lanthanum added with a third group element (in the Periodic Table) such as strontium (Sr).  
         [0044]    The anode layer  12   b  and the cathode layer  12   c  are porous layers having a porosity of 20% or more, preferably in a range from 30 to 70%, more preferably from 40 to 50%.  
         [0045]    The fuel cell  10   a  shown in FIGS. 1 and 2 is obtained by using a shape-retaining tubular core of the same material as the cathode layer  12   c  on which are wrapped a solid-electrolyte cell material to be the solid-electrolyte layer  12   a  and an anode cell material to be the anode layer  12   b  or coated with pastes of these materials in this order, which layers are then fired at a predetermined temperature.  
         [0046]    The fuel cell  10   b  having a desired inner diameter is obtained by using a shape-retaining tubular core of the same material as the anode layer  12   b  on which are wrapped a solid-electrolyte cell material to be the solid-electrolyte layer  12   a  and a cathode cell material to be the cathode layer  12   c  or coated with pastes of these materials in this order, which layers are then fired at a predetermined temperature.  
         [0047]    In the fuel cell section  10  formed of two cylindrical fuel cells  10   a  and  10   b  different in inner diameter from each other and disposed in concentric with each other at a predetermined space between the both, nozzles  16 ,  16 , . . . for supplying gaseous fuel such as butane or propane are provided at a lower end of the space  14  in which the anode layers  12   b  and  12   b  are opposite to each other as shown in FIG. 3 in a standing-up state.  
         [0048]    When the gaseous fuel is supplied to each of the nozzles  16 ,  16 , . . . , flames  18 ,  18 , . . . are formed in the extending direction in the space  14  between the anode layers  12   b . Accordingly, as the flames  18 ,  18 , . . . are encircled by the anode layers  12   b  and  12   b , heat from the flames  18 ,  18 , . . . is sufficiently used for heating the fuel cells  10   a  and  10   b  without the necessity of other external heating means for heating the fuel cells  10   a  and  10   b.    
         [0049]    Further, hydrocarbon, hydrogen or various radicals are usable for the generation of electric power by the anode layers  12   b ,  12   b  encircling the flames  18 ,  18 , . . . . Particularly, in the fuel cell  10   a  and  10   b  having the anode layers  12   b  formed of the fired material mainly composed of NiO in which Li is contained as a solid solution, not only the reducing flame portions of the flames  18 ,  18 , . . . but also the oxidizing flame portions are usable for the generation of electric power.  
         [0050]    As the flames  18 ,  18 , . . . are formed in the extending direction in the space  14  between the anode layers  12   b ,  12   b , the convection of air derived from the flames  18 ,  18 , . . . flows in the same direction as the extending direction of the flames  18 ,  18 , . . . . Thereby, air is supplied not only to the space  14  but also to the cathode layer  12   c  so that electromotive force occurs between the anode layers  12   b  exposed to the flames  18 ,  18 , . . . .  
         [0051]    While gaseous fuel is used in the fuel supply means shown in FIG. 3, liquid fuel can also be supplied.  
         [0052]    One embodiment of means for supplying liquid fuel is shown in FIG. 4. FIG. 4 is a sectional view of the fuel supply means for supplying liquid fuel such as ethanol provided at a lower end of the space  14  in which the anode layers  12   b  and  12   b  are opposite to each other while the fuel cell section  10  is in the standing-up state.  
         [0053]    In the fuel cell section  10  shown in FIG. 4, the same reference numerals are used for denoting the same elements in FIG. 3 and the detailed explanation thereof will be eliminated.  
         [0054]    The means for supplying liquid fuel such as ethanol shown in FIG. 4 is constituted by a tank  30  for storing the liquid fuel  32  such as ethanol and supplying members  20 , one ends of which are dipped in the liquid fuel  32  in the tank  30  and the other ends are inserted into a lower end of the space  14  in which the anode layers  12   b  and  12   b  are located opposite to each other. The supplying member  20  may be composed of heat-durable fibers collected to convey the liquid fuel upward due to the capillarity thereof. The supplying member  20  may be provided to be movable upward and downward.  
         [0055]    When the liquid fuel is vaporized from the upper end of the supplying members  20  and ignited, the flames  22 ,  22 , . . . are formed in the extending direction of the anode layers  20   b  and  12   b  as shown in FIG. 4. Therefore, in the same manner as the fuel cell device shown in FIG. 3, the fuel cells  10   a  and  10   b  can be heated to generate the electric power while using heat, hydrocarbon, hydrogen or various radicals generated from the flames  22 ,  22 , . . . .  
         [0056]    The fuel cell section  10  shown in FIGS.  1  to  4  includes the two fuel cells  10   a  and  10   b . The electric power generated from the fuel cells  10   a  and  10   b  may be individually taken out. However, as shown in FIG. 5, the fuel cells  10   a  and  10   b  may be preferably connected in parallel to each other by wires  24 ,  24 , . . . , or as shown in FIG. 6, the fuel cells  10   a  and  10   b  may be preferably connected in series to each other by wires  24 ,  24 , . . . , so that the electric power is collectively taken out.  
         [0057]    [0057]FIGS. 7 and 8 are illustrations of another embodiment of a fuel cell section according to this invention. In this embodiment, there are arranged, vertically, four cylindrical fuel cells  10   a ,  10   b ,  10   c  and  10   d  different in diameter to each other and are arranged in concentric with each other. Therefore, in this embodiment, two annular spaces  14 , i.e., inner and outer annular spaces  14 ,  14 , each having a predetermined gap, are defined between the anode layers  12   b ,  12   b  of the adjacent cylindrical fuel cells  10   a  and  10   b , and between the anode layers of the adjacent cylindrical fuel cells  10   c  and  10   d , respectively.  
         [0058]    While the fuel cell section  10  shown in FIGS.  1  to  8  is formed by disposing the a plurality of cylindrical fuel cells  10   a ,  10   b , . . . concentric with each other, it may be possible as shown in FIG. 9 to provide a fuel cell section  40  formed of a plurality of flat-plate type fuel cells.  
         [0059]    In the fuel cell section  40  shown in FIG. 9, four flat-plate type fuel cells  40   a ,  40   b ,  40   c  and  40   d  are disposed at a predetermined space  14 ,  14  between the adjacent ones.  
         [0060]    Each of the fuel cells  40   a ,  40   b ,  40   c  and  40   d  has an anode layer  42   b  on one surface of a solid-electrolyte layer  42   a  and a cathode layer  42   c  on the other surface of the solid-electrolyte layer  42   a.    
         [0061]    Of these fuel cells  40   a ,  40   b ,  40   c  and  40   d , the fuel cells  40   a  and  40   b  and the fuel cells  40   c  and  40   d  are disposed so that the anode layers  42   b  and  42   b  thereof are opposite to each other.  
         [0062]    In the fuel cell section  40  shown in FIG. 9, there are fuel supply means for supplying gaseous or liquid fuel in the spaces  14 ,  14  in which the anode layers  42   b  and  42   b  are located opposite to each other as shown in FIG. 3 or  4 .  
         [0063]    The fuel cells  40   a ,  40   b ,  40   c  and  40   d  constituting the fuel cell section  40  shown in FIG. 9 are formed of the same material as the fuel cells  10   a  and  10   b  shown in FIGS.  1  to  6  and, therefore, a detailed description thereof will be eliminated.  
         [0064]    Also, the fuel cells  40   a ,  40   b ,  40   c  and  40   d  are obtainable by laminating green sheets of predetermined shapes suitable for the respective layers on a solid-electrolyte layer  42   a  preliminarily formed by the firing, or coating pastes for the respective layers thereon, and thereafter firing the same again.  
         [0065]    While the electric power generated from the fuel cells  40   a ,  40   b ,  40   c  and  40   d  may be individually taken out from the respective fuel cells, it may be taken out in a collective manner by connecting the fuel cells  40   a ,  40   b ,  40   c  and  40   d  in parallel or series to each other.  
         [0066]    According to the inventive fuel cell device, it is possible to effectively use heat of the flame to supply sufficient amount of air to the cathode layer. Therefore, it is possible to generate the electric power by effectively using hydrocarbon, hydrogen or various radicals formed in the flame and oxygen in air on the anode layer while heating the fuel cells by the flames on the anode layer.  
         [0067]    As a result, it is possible to form the fuel cell device smaller in size without the necessity of external heating means for heating the fuel cells to a temperature capable of generating the electric power, whereby the fuel cell device according to the present invention is applicable to the outdoor use in camping or for emergency use.  
         [0068]    Also, heat generated from the fuel cell device may be used for room heating to save energy.  
         [0069]    It should be understood by those skilled in the art that the foregoing description relates to only some of the preferred embodiments of the disclosed invention, and that various changes and modifications may be made to the invention without departing from the sprit and scope thereof.