Patent Publication Number: US-2005130019-A1

Title: Structure for reducing internal circuit of fuel cell

Description:
TECHNICAL FIELD  
      The present invention relates to a fuel cell, and in particular to an structure for reducing internal circuit of a fuel cell capable of minimizing an internal circuit occurred among plural stacked unit cells.  
     BACKGROUND ART  
      Fuel cell has been presented as a substitute for fossil fuel, and it converts chemical energy generated by oxidation of fuel such as hydrogen into electric energy directly.  
       FIG. 1  illustrates an example of a fuel cell. As depicted in  FIG. 1 , in the fuel cell, when hydrogen-included fuel and air as a oxidant are supplied to a fuel electrode (anode)  11  and an air electrode (cathode)  12  arranged on both sides of an electrolyte layer  10  respectively, electrochemical oxidation reaction occurs on the fuel electrode  11 , hydrogen ions and electrons are emitted, the hydrogen ions are moved to the air electrode  12  through the electrolyte layer  10 , and the electrons are moved to the air electrode  12  through a load  20  connecting the fuel electrode  11  to the air electrode  12 . Simultaneously electrochemical reduction reaction occurs on the air electrode  12 , and heat and by-products are generated while the hydrogen ions are combined with oxygen. Herein, current is generated while the electrons emitted from the fuel electrode  11  are moved to the air electrode  12 .  
      One unit fuel cell is constructed with the structure. Herein, in order to generate greater electric energy, a fuel cell can be constructed by combining plural unit cells.  
      In addition, fuel cells can be classified into various kinds according to kinds of fuel, operational temperature and catalyzers, etc.  
      When fuel of hydrogen group such as NaBH4, KBH4, LiA1H4, KH, NaH, etc. is dissolved in an alkali aqueous solution, the fuel becomes an electrolyte solution, electrons generated with hydrogen ions are moved through the electrolyte solution (fuel).  
       FIG. 2  is a sectional view illustrating an example of a fuel cell using the electrolyte solution as fuel in accordance with the conventional art,  FIG. 3  is a plane view illustrating a stack of the fuel cell,  FIG. 4  is a plane view illustrating a first manifold of the fuel cell, and  FIG. 5  is a plane view illustrating a second manifold of the fuel cell.  
      As depicted in FIGS.  2 ˜ 5 , in the fuel cell, monopolar plates  110 ,  120  are respectively arranged on both sides of one bipolar plate  100 , two M.E.As (membrane electrode assembly)  130  are respectively inserted between the bipolar plate  100  and the monopolar plate  110 ,  120 , and an end plate  140  is respectively arranged on both sides of the monopolar plates  110 ,  120 . The bipolar plate  100 , the monopolar plate  110 ,  120 , the M.E.A  130  and the end plate  140  are fixedly combined by fastening means  150 , and accordingly a stack is constructed.  
      In the bipolar plate  100 , fluid flowing channels  102 ,  103  are respectively formed on both sides of a plate  101  having a certain thickness and area; and inflow paths  104 ,  105  and outflow paths  106 ,  107  in which fuel and air flow respectively are formed so as to be connected with the channels  102 ,  103 .  
      In the monopolar plates  110 ,  120 , fluid flowing channels  112 ,  122  are formed on a side of plates  111 ,  121  having a certain thickness and area; and inflow paths  113 ,  123  and outflow paths  114 ,  124  connected to the channels  112 ,  122  are formed on the plates  111 ,  121  so as to receive and discharge a fluid.  
      The fuel side inflow paths  104 ,  123  of the bipolar plate  100  and the monopolar plates  110 ,  120  are arranged on the same line, and the air side inflow paths  105 ,  113  are arranged on the same line with the fuel side inflow paths  104 ,  123  so as to have a certain interval.  
      In the M.E.A  130 , a fuel side electrode  132  contacted to fuel is formed on a side of the electrolyte layer  131  having a certain area, and an air side electrode  133  contacted to air is formed on the other side of the electrolyte layer  131 . In the M.E.As  130 , the same electrode is arranged on the same position.  
      A first manifold  160  for distributing fuel and air so as to make them flow into the fuel side inflow paths  104 ,  123  and the air side inflow paths  105 ,  113  respectively is arranged on a side of the stack, a second manifold  170  for gathering fuel and air to be respectively discharged to the fuel side outflow paths  106 ,  124  and the air side outflow paths  107 ,  114  is arranged on the other side of the stack, and the first and second manifolds  160 ,  170  are fixedly combined by additional fastening means  180 . In the first manifold  160 , a fuel side space  162  and an air side space  163  are respectively formed in a body unit  162  having a certain thickness and rectangular area, through holes  164  connected with the fuel side inflow paths  104 ,  123  are formed on the bottom of the fuel side space  162 , and through holes  165  connected with the air side inflow paths  105 ,  113  are formed on the bottom of the air side space  163 . And, in the second manifold  170 , a fuel side space  172  and an air side space  173  are respectively formed in a body unit  171  having a certain thickness and rectangular area, through holes  174  connected with the fuel side outflow paths  106 ,  124  are formed on the bottom of the fuel side space  172 , and through holes  175  connected with the air side outflow paths  107 ,  114  are formed on the bottom of the air side space  173 .  
      The fuel side space  162  of the first manifold is connected to a fuel tank (not shown) and a pump (not shown) by a pipe (not shown), and the fuel side space  172  of the second manifold is connected to the fuel tank by an additional reproducing means (not shown).  
      In the above-described fuel cell, when fuel in the fuel tank flows into the fuel side space  162  of the first manifold, simultaneously air flows into the air side space  163  of the first manifold. The fuel in the fuel side space  162  flows into the bipolar plate  100  and the inflow paths  104 ,  123  of the monopolar plate  120  of the stack through the through holes  164 .  
      When the fuel flows in the channels  102 ,  122 , electrochemical oxidation occurs on the fuel side electrode  132  of the M.E.A  130 , hydrogen ions and electrons are generated, the hydrogen ions are moved to the air side electrode  133  through the electrolyte layer  131  of the M.E.A, and the electrons are moved to the air side electrode  133  through the bipolar plate  100  or the monopolar plates  110 ,  120 . Simultaneously, when the air in the air side space  163  of the first manifold flows into the channels  103 ,  112  through the through holes  165  in the air side space, each bipolar plate  100  and the inflow paths  105 ,  113  of the monopolar plate  110  of the stack, electrochemical reduction reaction occurs with the hydrogen ions on the air side electrode  133  of the M.E.A.  
      In the meantime, the fuel discharged into the fuel side space  172  of the second manifold flows into the fuel tank through the reproducing means and is supplied again to the stack.  
      And, when a load is connected between the monopolar plates  110 ,  120 , electric energy is generated while current flows through the load by electric potential difference.  
      However, in the conventional structure, because the electrolyte solution is used as fuel, the fuel connects the stacked unit cells electrically so as to construct an internal circuit, electric leakage may occur, and accordingly electrical loss may occur.  
     TECHNICAL GIST OF THE PRESENT INVENTION  
      In order to solve the above-described problem, it is an object of the present invention to provide a structure for reducing internal circuit of a fuel cell capable of minimizing electric leakage occurred among plural stacked-unit cells.  
      In order to achieve the above-mentioned object, a structure for reducing internal circuit of a fuel cell includes adjacently stacked unit cells; a fuel side distributing means for connecting each fuel side inflow path of the unit cells and insulating them electrically; and an air side distributing means for connecting each air side inflow path of the unit cells.  
      In addition, a structure for reducing internal circuit of a fuel cell includes a stack consisting of adjacently stacked unit cells; a first and a second manifolds respectively arranged on both sides of the stack so as to have fuel side connection paths for connecting fuel side paths of the unit cells and air side connection paths for connecting air side paths of the unit cells; a first insulating member combined between the stack and the first manifold so as to have fuel side through holes for connecting the fuel side paths of the unit cell with the fuel side connection path of the first manifold and air side through holes for connecting the air side paths of the unit cell with the air side connection path of the first manifold; and a second insulating member combined between the stack and the second manifold so as to have fuel side through holes for connecting the fuel side paths of the unit cell with the fuel side connection path of the second manifold and air side through holes for connecting the air side paths of the unit cell with the air side connection path of the second manifold. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
      The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.  
      In the drawings:  
       FIG. 1  is a sectional view illustrating a general fuel cell;  
       FIG. 2  is a sectional view illustrating an example of the conventional fuel cell;  
       FIG. 3  is a plane view illustrating a stack of a fuel cell in accordance with the conventional art;  
       FIGS. 4 and 5  are plane views respectively illustrating partial-exploded first and second manifolds of the fuel cell in accordance with the conventional art;  
       FIG. 6  is a sectional view illustrating a fuel cell having a structure for reducing internal circuit of a fuel cell in accordance with a first embodiment of the present invention;  
       FIG. 7  is a plane view illustrating the fuel cell in  FIG. 6 ;  
       FIG. 8  is a sectional view illustrating a fuel cell having an internal circuit reducing structure in accordance with a second embodiment of the present invention;  
       FIG. 9  is a sectional view illustrating the fuel cell taken along a line A-B in  FIG. 8 ;  
       FIG. 10  is a sectional view illustrating the fuel cell taken along a line C-D in  FIG. 8 ; and  
       FIG. 11  is a graph showing comparison results of unit cells in accordance with the first and second embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Hereinafter, the preferred embodiments of the present invention will be described with reference to accompanying drawings.  
      First, a structure for reducing internal circuit of a fuel cell in accordance with a first embodiment of the present invention will be described.  
       FIG. 6  is a sectional view illustrating a fuel cell having an internal circuit reducing structure in accordance with a first embodiment of the present invention, and  FIG. 7  is a plane view illustrating the fuel cell in  FIG. 6 .  
      As depicted in  FIGS. 6 and 7 , the structure for reducing internal circuit of a fuel cell in accordance with the first embodiment of the present invention includes adjacently stacked unit cells (C); a fuel side distributing means for connecting each fuel side inflow path of the unit cells (C) and insulating them (electrically); and an air side distributing means for connecting each air side inflow path  205  of the unit cells (C).  
      The fuel side distributing means is a fuel side distributing pipe  240  for connecting each fuel side inflow path of the unit cells (C). The fuel side distributing pipe  240  distributes fuel to each fuel side inflow path of the unit cells (C) and simultaneously forms electrically insulating space.  
      The air side distributing means is an air side distributing pipe  280  for connecting each air side inflow path of the unit cells (C).  
      And, a fuel inflow pipe  250  is connected to the fuel side distributing pipe  240 , and the fuel inflow pipe  250  is connected to a fuel tank  260 . An air inflow pipe  290  in which external air flows is combined with the air side distributing means  280 .  
      The unit cell (C) consists of a bipolar plate  200 ; monopolar plates  210 ,  220  respectively arranged on both sides of the bipolar plate  200 ; and a M.E.A  230  respectively inserted between the bipolar plate  200  and the monopolar plate  210 ,  220 . The bipolar plate  200 , the two monopolar plates  210 ,  220  and the M.E.A  230  construct one unit cell (C).  
      In the bipolar plate  200 , channels  202 ,  203  are respectively formed on both sides of a plate  201  having a certain thickness and rectangular area, inflow paths  204 ,  205  for transmitting fuel and air respectively to the channels  202 ,  203  are formed on the plate  201 , and outflow paths  206 ,  207  for discharging the fuel and air of the channels  202 ,  203  are formed on the plate  201 . The fuel side inflow path  204  and the air side outflow path  207  are formed on a surface of the plate  201 , and the fuel side outflow path  206  and the air side inflow path  205  are formed on another surface (opposed to the above-mentioned surface) of the plate  201 . The fuel side inflow path  204  and the fuel side outflow path  206  are arranged diagonally, and the air side inflow path  205  and the air side outflow path  207  are arranged diagonally.  
      In the monopolar plate  210 ,  220 , a channel  212 ,  222  is formed on a side of a surface  211 ,  221  having a certain thickness and rectangular area, and an inflow path  213 ,  223  and an outflow path  214 ,  224  for receiving and discharging a fluid into/from the channel  212 ,  222  are formed on the plate  211 ,  221 . The monopolar plates  210 ,  220  are respectively arranged on both sides of the bipolar plate  200  so as to make the channels  212 ,  222  face the channels  202 ,  203  of the bipolar plate. Herein, when the channel  212  of the monopolar plate  210  faces the channel  203  in which air flows of the bipolar plate  200 , fuel flows in the channel  212  of the monopolar plate  210 . When the channel  222  of the monopolar plate  220  faces the channel  202  in which fuel flows of the bipolar plate  200 , air flows in the channel  222  of the monopolar plate  220 .  
      In the M.E.A  230 , a fuel side electrode  232  on which fuel is contacted is formed on a side of an electrolyte layer  231  having a certain area, and an air side electrode  233  in which air is contacted is formed on the other side of the electrolyte layer  231 . The M.E.A  230  is inserted between the bipolar plate  200  and the monopolar plate  210 ,  220  so as to make the electrodes  232 ,  233  be arranged in the same direction.  
      The fuel side distributing pipe  240  connects the fuel side inflow path  204  of the bipolar plate to the fuel side inflow path  213  of the monopolar plate in which fuel flows. The fuel side distributing pipe  240  is curved-formed. The fuel inflow pipe  250  is connected to the fuel side distributing pipe  240 , and the fuel inflow pipe  250  is connected so as to be arranged on the center of the fuel side distributing pipe  240 .  
      The fuel inflow pipe  250  is connected to a fuel tank  260  for storing fuel, a first pump  270  for pumping fuel is installed on the fuel inflow pipe  250 , and the first pump  270  is arranged between the fuel side distributing pipe  240  and the fuel tank  260 . Fuel of the fuel tank is an electrolyte solution.  
      The fuel side distributing pipe  240  and the fuel inflow pipe  250  are made of an insulating material.  
      An outflow pipe  208  is respectively combined with the fuel side outflow path  206  of the bipolar plate  200  and the fuel side outflow path  214  of the monopolar plate  210  adjacent to the fuel side outflow path  206  and having fuel.  
      The air side distributing pipe  290  connects the air side inflow path  205  of the bipolar plate  200  with the air side inflow path  223  of the monopolar plate  220  adjacent to the air side inflow path  205  and having air. The air side distributing pipe  290  is curved-formed. The air inflow pipe  251  is connected to the air side distributing pipe  290 , and the air inflow pipe  251  is connected so as to be arranged on the center of the air side distributing pipe  290 . The air side distributing pipe  290  and the air inflow pipe  251  are made of an insulating material.  
      A second pup  271  for pumping air is installed on the air inflow pipe  251 .  
      An outflow pipe  281  is respectively connected with the air side outflow path  207  of the bipolar plate  200  and the air side outflow path  224  of the monopolar plate  220  adjacent to the air side outflow path  207  and having air.  
      The operation of the structure for reducing internal circuit of a fuel cell will be described.  
      First, when the first pump  270  and the second pump  271  are operated, fuel in the fuel tank  260  flows into the fuel side distributing pipe  240  through the fuel inflow pipe  250 . The fuel in the fuel side distributing pipe  240  is distributed and flows into the fuel side inflow paths  204 ,  213  of each unit cell (C), the fuel in the fuel side inflow paths  204 ,  213  flows through the channels  202 ,  212 . While the fuel flows through the channels  202 ,  212 , electrochemical oxidation occurs by the fuel side electrode  232  of the M.E.A, hydrogen ions and electrons are generated, the hydrogen ions are moved to the air side electrode  233  through the electrolyte layer  231  of the M.E.A, and the electrons are moved to the air side electrode  233  through the bipolar plate  200 .  
      Simultaneously, when external air flows into the air side distributing pipe  290  through the air inflow pipe  251  and flows into the air side inflow path  205 ,  223  of each unit cell (C). While the air in the air side inflow path  205 ,  223  of each unit cell (C) flows through the channels  203 ,  222 , electron-chemical oxidation occurs on the air side electrode  233  of the M.E.A with the hydrogen ions.  
      The fuel passing the channel  202 ,  212  of each unit cell (C) is respectively discharged through the fuel side discharge path  206 ,  214  and the discharge pipe  280 . The air passing the channel  203 ,  222  of each unit cell (C) is discharged through the air side outflow path  207 ,  224  and the outflow pipe  281 . The fuel discharged through the outflow pipe  280  passes an additional reproducing means (not shown) and flows again into the fuel tank  260 .  
      When a load is connected between the monopolar plates  210 ,  220 , electric energy is generated while current flows through the load by the electric potential difference.  
      In that process, because the fuel supplied from the fuel tank  260  is distributed through the fuel side distributing pipe  240  and flows into the fuel side electrode  232  of each unit cell (C), electric leakage occurred by electric connection of the fuel can be restrained by the fuel side distributing pipe  240 . In more detail, because the fuel as the electrolyte solution flowing into each unit cell (C) is connected through the fuel side distributing pipe  240  having a certain length, electric connection by the fuel is unstable, and accordingly electric leakage can be minimized.  
      In addition, the fuel passing each unit cell (C) is respectively discharged through an additional discharge pipe  280 , electric connection by the fuel is cut off, and accordingly electric leakage can be prevented.  
      In the meantime, in the present invention, by installing respectively a pump  270 ,  271  for pumping fuel and air, the number of pumps can be minimized.  
      And, an internal ground current reducing structure of a fuel cell in accordance with a second embodiment of the present invention will be described.  
       FIG. 8  is a sectional view illustrating a fuel cell having an internal circuit reducing structure in accordance with a second embodiment of the present invention,  FIG. 9  is a sectional view illustrating the fuel cell taken along a line A-B in  FIG. 8 , and  FIG. 10  is a sectional view illustrating the fuel cell taken along a line C-D in  FIG. 8 .  
      As depicted in  FIGS. 8-10 , the structure for reducing internal circuit of a fuel cell in accordance with the second embodiment of the present invention includes a stack consisting of stacked unit cells (C); a first and a second manifolds respectively arranged on both sides of the stack so as to have a fuel side connection path for connecting fuel side paths of the unit cells (C) and an air side connection path for connecting air side paths of the unit cells (C); a first insulating member combined between the stack and the first manifold so as to have fuel side through holes for connecting the fuel side paths of the unit cell (C) with the fuel side connection path of the first manifold and air side through holes for connecting the air side paths of the unit cell (C) with the air side connection path of the first manifold; and a second insulating member combined between the stack and the second manifold so as to have fuel side through holes for connecting the fuel side paths of the unit cell (C) with the fuel side connection path of the second manifold and air side through holes for connecting the air side paths of the unit cell (C) with the air side connection path of the second manifold.  
      The stack consists of two unit cells (C). In the unit cell (C), monopolar plates  310 ,  320  are respectively arranged on both sides of one bipolar plate  300 , and a M.E.A  330  is respectively inserted between the bipolar plate  300  and the monopolar plate  310 ,  320 .  
      The unit cell (C) consists of a bipolar plate, a monopolar plate and a M.E.A.  
      The bipolar plate  300 , the monopolar plates  310 ,  320  and the M.E.A  330  have the same structure with the bipolar plate  200 , the monopolar plates  210 ,  220  and the M.E.A  230  of the structure in accordance with the first embodiment.  
      Reference numerals  301 ,  311 ,  312  are plates,  302  and  303  are channels,  304  and  313  are fuel side inflow paths,  305  and  323  are air side inflow paths,  306  and  314  are fuel side outflow paths,  307  and  324  are air side outflow paths. In addition, reference numeral  331  is an electrolyte layer,  332  is a fuel side electrode,  333  is an air side electrode, and  420  is an end plate.  
      In the first manifold  340 , a fuel side connection path  342  is formed on a side of a body  341  having a certain thickness and rectangular area, and an air side connection path  343  is formed on the other side of the body  341 . The fuel side connection path  342  is formed so as to connect fuel side inflow paths  304 ,  313  of adjacent two unit cells (C). The air side connection path  343  is formed so as to connect air side outflow paths  307 ,  324  of the two unit cells (C).  
      In modification of the first manifold  340 , it is divided into a part including the fuel side connection path  342  and a part including the air side connection path  343 . The part including the fuel side connection path  342  and the part including the air side connection path  343  are formed so as to have a certain thickness and rectangular area.  
      In the second manifold  350 , a fuel side connection path  352  is formed on a side of a body  351  having a certain thickness and rectangular area, and an air side connection path  353  is formed on the other side of the body  351 . The fuel side connection path  352  is formed so as to connect fuel side outflow paths  306 ,  314  of adjacent two unit cells (C). The air side connection path  353  is formed so as to connect air side inflow paths  305 ,  323  of the two unit cells (C).  
      In modification of the second manifold  350 , it is divided into a part including the fuel side connection path  352  and a part including the air side connection path  353 . The part including the fuel side connection path  352  and the part including the air side connection path  353  are formed so as to have a certain thickness and rectangular area.  
      The first and second manifolds  340 ,  350  can be made of an insulating material, herein, usage of the first and second insulating members  360 ,  370  can be excluded.  
      The first and second manifolds  340 ,  350  are fixedly combined by additional fastening means  400 .  
      The first and second insulating members  360 ,  370  have a rectangular shape and a certain thickness, and a fuel side through hole  361 ,  371  and an air side through hole  362 ,  372  are respectively formed in them. When the fuel side through hole  361 ,  371  and the air side through hole  362 ,  372  are filled with fuel, there is an insulating space.  
      A fuel inflow pipe  390  connected to the fuel tank  380  is connected with the fuel side connection path  342  of the first manifold  340 , and an outflow pipe  391  for discharging air is connected with the air side connection path  343 . A first pump  392  is installed on the fuel inflow pipe  390 , and fuel stored in the fuel tank  380  is an electrolyte solution.  
      A fuel outflow pipe  393  for discharging fuel is connected with the fuel side connection path  352  of the second manifold  350 , and an air inflow pipe  394  in which external air flows is connected with the air side connection path  353 . A second pump  395  is installed on the air inflow pipe  394 .  
      Hereinafter, the operation of the structure for reducing internal circuit of a fuel cell in accordance with the second embodiment of the present invention will be described.  
      First, fuel in the fuel tank  380  flows into the fuel side connection path  342  of the first manifold through the fuel inflow pipe  390  and flows into the fuel side inflow path  304 ,  313  of each unit cell (C) of the stack, and the fuel in the fuel side inflow path  304 ,  313  flows through the channels  302 ,  312 . While the fuel flows through the channel  302 ,  312 , electrochemical oxidation reaction occurs by the fuel side electrode  332  of the M.E.A, hydrogen ions and electrons are generated, the hydrogen ions are moved to the air side electrode  333  through the electrolyte layer  331  of the M.E.A, and the electrons are moved to the air side electrode  333  through the bipolar plate  300 .  
      Simultaneously, when external air flows into the air side connection path  353  through the air inflow pipe  394  and flows into the air side inflow path  305 ,  323  of each unit cell (C). While the air in the air side inflow path  305 ,  323  of each unit cell (C) flows through the channel  303 ,  322 , electron-chemical oxidation reaction occurs on the air side electrode  333  of the M.E.A with the hydrogen ions.  
      The fuel passing the channel  302 ,  312  of each unit cell (C) is respectively discharged through the fuel side discharge path  306 ,  314 , the discharge pipe  393  and the fuel side connection path  352  of the second manifold. The air passing the channels  303 ,  322  of each unit cell (C) is discharged through the air side outflow paths  307 ,  324 , the air side connection path  343  and the outflow pipe  391  of the first manifold. The fuel discharged through the outflow pipe  393  passes an additional reproducing means (not shown) and flows again into the fuel tank  380 .  
      When a load is connected between the monopolar plates  310 ,  320 , electric energy is generated while current flows through the load by the electric potential difference.  
      In that structure, because the first and second insulating members  360 ,  370  are combined between the first and second manifolds  340 ,  350 , electric leakage performed by the stack, the first manifold  340 , the stack and the second manifold  350  can be prevented.  
      In addition, by the first and second insulating members  360 ,  370 , electric leakage occurred by connection of the fuel as the electrolyte can be minimized. In more detail, the electric connection of the fuel formed with the fuel side connection path  342  of the first manifold, the fuel side connection path  352  of the second manifold and the paths in which the fuel flows of the unit cells (C) is unstable by height of the fuel side through holes  361 ,  371  of the first and second insulating members  360 ,  370 , and accordingly leakage can be minimized. In more detail, the fuel side through holes  361 ,  371  of the first and second insulating members perform functions of an insulating pipe, electric connection by the fuel is unstable, and leakage can be minimized.  
      In the meantime, when the first and second manifolds  340 ,  350  are made of an insulating material, electric connection by the fuel is unstable, and accordingly leakage can be minimized.  
       FIG. 11  is a graph showing comparison results of unit cells in accordance with the first and second embodiments of the present invention.  
      As depicted in  FIG. 11 , in the first and second embodiments, it can be known electric loss due to electric leakage is small in comparison with a general unit cell. The unit cell has a structure having little electric leakage caused by fuel and additional parts.  
     INDUSTRIAL APPLICABILITY  
      As described-above, in the a structure for reducing internal circuit of a fuel cell in accordance with the present invention, among stacked plural unit cells, by minimizing electric connection by fuel as an electrolyte solution and electric leakage occurred by electric connection by additional parts, electric energy efficiency of a unit cell can be improved.