Patent Publication Number: US-9847546-B2

Title: Separator for fuel cell and fuel cell including the same

Description:
RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/KR2013/012151, filed on Dec. 24, 2013 which in turn claims the benefit of Korean Patent Application No. 10-2012-0152259 filed on Dec. 24, 2012, the disclosures of which the applications are incorporated by reference herein. 
     TECHNICAL FIELD 
     The present disclosure relates to a separator for a fuel cell and a fuel cell including the same and, more particularly, to a separator for a fuel cell and a fuel cell including the same able to enhance the horizontal distribution of fuel or an oxidizing agent and secure an effective flow area. 
     BACKGROUND ART 
     In general, fuel cells are power generation systems converting the chemical energy of fuel into electrical energy. For example, a fuel cell converts chemical energy, generated during a chemical reaction between hydrogen fuel supplied to an anode and an oxidizing agent injected into a cathode, into electrical energy. 
     Such fuel cells are classified as low-temperature type fuel cells and high-temperature type fuel cells according to operating temperature and electrolyte type. A proton exchange membrane fuel cell (PEMFC) is representative of low-temperature type fuel cells and is mainly used for vehicles or the like, while a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC), and a solid oxide electrolysis cell (SOEC) using a reverse reaction of SOFC are representative of high-temperature type fuel cells. 
     A fuel cell  10  is capable of continuously generating power while fuel (hydrogen) and an oxidizing agent are continuously injected thereinto, and by enhancing the utilization rate of fuel in consideration of power generation efficiency and economical efficiency, such a fuel cell may have increased commercial value. 
     Separators  20  and  30  for the conventional fuel cell  10  include flat plates  22  and  32  providing a flow path in which fuel or an oxidizing agent flows. Intake manifolds  24  and  34  into which the fuel or the oxidizing agent is introduced are provided at one end portions of the flat plates  22  and  32 , and exhaust manifolds  26  and  36  from which the fuel or the oxidizing agent is discharged are provided at the other end portions of the flat plates  22  and  32  to be opposite to the intake manifolds  24  and  34 . Such separators  20  and  30  for the fuel cell  10  are alternately stacked to form a stack. 
     Meanwhile, conventional fuel cells  10  are classified according to a variety of schemes on the basis of arrangements of the separators  20  and  30  and the like. For example, representative schemes are a co-flow scheme in which the fuel and the oxidizing agent are introduced in the same direction as illustrated in  FIG. 1 , a counter-flow scheme in which the fuel and the oxidizing agent are introduced in opposite directions as illustrated in  FIG. 2 , and a cross-flow scheme in which the fuel and the oxidizing agent are introduced in directions perpendicular to each other as illustrated in  FIG. 3 . 
     The flow directions and operating conditions (load, utilization rate and the like) of the fuel and the oxidizing agent in the conventional fuel cell  10  may be determined according to the structures, arrangements, or the like of the separators  20  and  30 , and accordingly, it is determined where an electrochemical reaction occurs. Furthermore, due to the structural constraints of the separators  20  and  30  according to the related art, a portion of the fuel cell where the electrochemical reaction occurs is biased toward one side, and accordingly, the temperature gradient is also biased toward one side. 
     Therefore, the thermal stress distribution in the entire stack of the conventional fuel cell  10  may be asymmetrical, and accordingly, power generation efficiency may be lowered due to the non-uniform flow or biased flow of the fuel or the oxidizing agent. As such non-uniformity is continued, this consequently causes a negative effect on the structural stability of the stack during thermal cycling in the stack. 
     In this regard, as illustrated in  FIGS. 4 through 6 , a cross-shift flow scheme has recently been suggested in order to solve the structural constraints in the co-flow scheme, the counter-flow scheme, and the cross-flow scheme. 
     A fuel cell  50  using a cross-shift flow scheme is provided to reduce non-uniformity of the overall temperature gradient by alternately forming manifold structures in odd-numbered unit cells and even-numbered unit cells. 
     That is, in separators  60  of the odd-numbered unit cell  51  in which fuel or an oxidizing agent is circulated, some regions of the separators are provided with intake manifolds  62  and  72  into which the fuel or the oxidizing agent is introduced and other regions thereof are provided with exhaust manifolds  64  and  74  from which the fuel or the oxidizing agent is discharged. 
     In addition, in separators  80  and  90  of the even-numbered unit cell  55  in which the fuel or the oxidizing agent is circulated, intake manifolds  82  and  92  and exhaust manifolds  84  and  94  are provided to intersect those of the separators  60  and  70  of the odd-numbered unit cell  51 . 
     Such a fuel cell  50  using the cross-shift flow scheme may solve the issue of non-uniformity of the temperature gradient to some extent, but portions of the intake manifolds  82  and  92  and the exhaust manifolds  84  and  94  are blocked in corresponding cells, causing a flow distribution in a horizontal direction to be degraded. Thus, the fuel may not be uniformly supplied to the entirety of the cells, whereby the overall performance of the fuel cell  50  may be lowered. 
     In this regard, a technique for allowing for uniform flow distribution throughout the entirety of the cells through the distributed arrangement of the intake manifolds  82  and  92  and the exhaust manifolds  84  and  94  has been developed. 
     However, since the conventional fuel cell  50  using the cross-shift flow scheme has sealing members  63 ,  73 ,  83  and  93  for sealing between the intake manifolds  62 ,  72 ,  82  and  92  and the exhaust manifolds  64 ,  74 ,  84  and  94 , the sealing members  63 ,  73 ,  83  and  93  may interrupt the diffusion of the fuel or the oxidizing agent in the horizontal direction while the fuel or the oxidizing agent is flowing from the intake manifolds  62 ,  72 ,  82  and  92  to a reaction surface of the cell, resulting in a flow deviation between the manifold holes and the blocked portions of the manifolds. 
     Meanwhile, the fuel cell  50  using the cross-shift flow scheme may be modified in order to allow the horizontal diffusion to be more uniform. For example, a separator  60 ′ of the odd-numbered unit cell  51  in which the fuel or the oxidizing agent is circulated may be modified to have the intake manifold  62  which is disposed in an intermediate position and exhaust manifolds  64   a  and  64   b  which are separately formed. 
     In addition, for example, a separator  80 ′ of the even-numbered unit cell  55  in which the fuel or the oxidizing agent is circulated may be modified to have the intake manifold  82  which is disposed in an intermediate position and exhaust manifolds  84   a  and  84   b  which are separately formed. In this case, the intake manifold  82  and the exhaust manifolds  84   a  and  84   b  may be sealed by the sealing members  63  and  83 . 
     Meanwhile, referring to  FIG. 9 , the conventional fuel cell  50  using the cross-shift flow scheme may create more uniform horizontal diffusion as the number of intake manifolds and exhaust manifolds is increased. However, an area occupied by the sealing members  63  and  83  is also increased and an effective flow area for actual flow is reduced, and accordingly, the overall reaction efficiency and fuel utilization rate may be lowered. 
     That is, when LH denotes the width of the intake manifold and the exhaust manifold and LS denotes the width of the sealing member, the number of sealing members having the same width may be (n−1) with respect to the n number of manifolds. 
     The width L of the effective flow area of the fuel cell is represented by the following equation 1: 
     
       
         
           
             
               
                 
                   L 
                   = 
                   
                     
                       
                         L 
                         H 
                       
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                       n 
                     
                     
                       
                         
                           L 
                           H 
                         
                         × 
                         n 
                       
                       + 
                       
                         
                           L 
                           S 
                         
                         × 
                         
                           ( 
                           
                             n 
                             - 
                             1 
                           
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     Therefore, the conventional fuel cell should be developed to have a structure in which the horizontal distribution of the fuel or the oxidizing agent is improved without reducing the effective flow area L of the fuel cell. 
     DISCLOSURE 
     Technical Problem 
     An aspect of the present disclosure provides a separator for a fuel cell and a fuel cell including the same able to enhance the horizontal distribution of fuel or an oxidizing agent and secure an effective flow area. 
     Technical Solution 
     According to an aspect of the present disclosure, there is provided a separator for a fuel cell, including: a separator body; a first intake manifold provided at one end portion of the separator body; a second intake manifold provided at the other end portion of the separator body to be partitioned from the first intake manifold; a first exhaust manifold provided outwardly of the second intake manifold at the other end portion of the separator body; and a second exhaust manifold provided outwardly of the first intake manifold at one end portion of the separator body to be partitioned from the first exhaust manifold. 
     The separator body may be provided with one or more of the first and second intake manifolds. 
     The first exhaust manifold and the second exhaust manifold may be elongated in a width direction of the separator body. 
     The separator body may have a circulation path between the first intake manifold and the first exhaust manifold in the interior thereof. 
     According to another aspect of the present disclosure, there is provided a fuel cell including one or more unit cells stacked therein, wherein the unit cell may include the separator for a fuel cell as described above, the separator including a plurality of separators, and the separators for a fuel cell may be stacked to intersect perpendicularly to allow fuel or an oxidizing agent to intersect and circulate. 
     The separator body may have a circulation path between the first intake manifold and the first exhaust manifold in the interior thereof. 
     The circulation path may allow a gas supplied by the first intake manifold to pass between the second intake manifolds and be discharged through the first exhaust manifold. 
     The second intake manifold of the separator may be connected to a first intake manifold of another separator by sealing, and the second exhaust manifold of the separator may be connected to a first exhaust manifold of another separator by sealing. 
     Advantageous Effects 
     According to an exemplary embodiment in the present disclosure, intake and exhaust manifolds are arranged in two rows, such that a space available for the diffusion of fuel or an oxidizing agent supplied by the intake manifolds is secured, resulting in secured effective area and improved horizontal distribution, while a single exhaust manifold is provided such that biased flow, which may be caused by a flow change or the like, resulting from a reaction, is reduced. Accordingly, the fuel cell, according to the present embodiment, may have improvements in the reaction efficiency and utilization rate of the fuel due to the improved horizontal distribution, the secured effective area, and the reduction of biased flow. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating the operation of a fuel cell using a co-flow scheme according to the related art; 
         FIG. 2  is a view illustrating the operation of a fuel cell using a counter-flow scheme according to the related art; 
         FIG. 3  is a view illustrating the operation of a fuel cell using a cross-flow scheme according to the related art; 
         FIG. 4  is a perspective view of a fuel cell using a cross-shift flow scheme according to the related art; 
         FIG. 5  is a plan view of an odd-numbered separator of a fuel cell using a cross-shift flow scheme according to the related art; 
         FIG. 6  is a plan view of an even-numbered separator of a fuel cell using a cross-shift flow scheme according to the related art; 
         FIG. 7  is a plan view of a modified separator of a fuel cell using a cross-shift flow scheme according to the related art; 
         FIG. 8  is a plan view of another modified separator of a fuel cell using a cross-shift flow scheme according to the related art; 
         FIG. 9  is a view illustrating an effective flow area of a fuel cell using a cross-shift flow scheme according to the related art; 
         FIG. 10  is a plan view of a separator for a fuel cell according to an exemplary embodiment in the present disclosure; 
         FIG. 11  is a view illustrating a reaction region of a separator for a fuel cell according to an exemplary embodiment in the present disclosure; and 
         FIG. 12  is a plan view of a separator for a fuel cell according to another exemplary embodiment in the present disclosure. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The disclosure may, however, be exemplified in many different forms and should not be construed as being limited to the specific embodiments set forth herein. In the drawings, the shapes and dimensions of elements may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like elements. 
       FIG. 10  is a plan view of a separator for a fuel cell according to an exemplary embodiment in the present disclosure. 
     Referring to  FIG. 10 , a fuel cell  100  according to the present embodiment may be provided with one or more unit cells stacked therein. For example, the fuel cell  100  may have a stack structure in which separators and cells are alternately stacked in order of a separator, a cell, a separator, a cell and so on. 
     Such a unit cell may include one or more separators  110  and  120  and may generate energy through the oxidation-reduction reaction of fuel and an oxidizing agent supplied to the separators  110  and  120 . 
     In the fuel cell  100  according to the present embodiment, the separators  110  and  120  of the unit cells may be alternately stacked, wherein even-numbered separators may be connected to each other and odd-numbered separators may be connected to each other. 
     In addition, the fuel cell  100  according to the present embodiment may be a solid oxide fuel cell (SOFC) by way of example. 
     Such unit cells used in the fuel cell  100  may be stacked and connected to each other so as to increase the amount of voltage supplied thereto. 
     The fuel cell  100  may include an electrolyte membrane provided to separate the fuel from the oxidizing agent in the separators, and an anode and a cathode provided on both sides of the separators based on the electrolyte membrane, besides the separators  110  and  120  for separately supplying and discharging the fuel and the oxidizing agent. 
     More specifically, the fuel cell  100  according to the present embodiment may include the separator  110  to which the fuel is supplied, and the separator  110  for fuel may be associated with the separator  120  to which the oxidizing agent is supplied. 
     The separator  110  for fuel and the separator  120  for the oxidizing agent may be provided to intersect in directions perpendicular to each other, and accordingly, the fuel or the oxidizing agent may be supplied while intersecting and circulating in the directions perpendicular to each other. 
     Meanwhile, the separator  110  or  120  may include a flat plate which is a separator body having a circulation path for guiding the flow of the fuel or the oxidizing agent in the interior thereof. 
     In addition, one end portions of the separator bodies of the separators  110  and  120  may be provided with first intake manifolds  112  and  122  to which a gas, namely, the fuel or the oxidizing agent is supplied. 
     Furthermore, the other end portions of the separator bodies of the separators  110  and  120  may be provided with second intake manifolds  116  and  126  which are partitioned from the first intake manifolds  112  and  122 . The second intake manifolds  116  and  126  may be provided at the other end portions of the separator bodies to be sealed by using a sealing member or the like, and accordingly, the second intake manifolds  116  and  126  do not supply the gases to the separators  110  and  120 , but supply the gases to other separators  110  and  120  connected thereto through first intake manifolds  112  and  122  of the other separators  110  and  120 . 
     In addition, the other end portions of the separators  110  and  120 , which are opposing regions in which the gases reach after passing through an effective reaction region of the cell, may be provided with first exhaust manifolds  114  and  124  from which the gases supplied by the first intake manifolds  112  and  122  are discharged after passing between the second intake manifolds  116  and  126 . 
     Furthermore, one end portions of the separator bodies of the separators  110  and  120  may be provided with second exhaust manifolds  118  and  128 , outwardly of the first intake manifolds  112  and  122 , as spaces partitioned from the first exhaust manifolds  114  and  124 . 
     In addition, the second exhaust manifolds  118  and  128  may be provided outwardly of the first intake manifolds  112  and  122  at one end portions of the separator bodies of the separators  110  and  120  to be sealed by using a sealing member or the like. The second exhaust manifolds  118  and  128  may be connected to first exhaust manifolds  114  and  124  of other separators  110  and  120  connected thereto, and accordingly, without the discharge of the gases to the separators  110  and  120 , the second exhaust manifolds  118  and  128  may be connected to the first exhaust manifolds  114  and  124  of the other separators  110  and  120  connected thereto to discharge the gases. 
     According to the present embodiment, one or more first intake manifolds  112  and  122  may be provided at one end portions of the separator bodies. Preferably, according to the present embodiment, two first intake manifolds  112  and  122  may be provided to be spaced apart from each other by a predetermined interval. 
     Furthermore, the first exhaust manifolds  114  and  124  may be formed at the other end portions of the separator bodies to be elongated in the width direction of the separator bodies. That is, the first exhaust manifolds  114  and  124 , according to the present embodiment, may be provided in the form of a hole, and may be provided as a long slot elongated in the width direction. 
     Therefore, the first exhaust manifolds  114  and  124  may rapidly discharge the fuel or the oxidizing agent that has undergone an electrochemical reaction in the interior of the cell to the second exhaust manifolds  118  and  128 , and the biased flow or the like may be prevented. Without the occurrence of a bottleneck phenomenon, a flow restriction may be minimized. 
     Meanwhile, the second intake manifolds  116  and  126  may be provided inwardly of the first exhaust manifolds  114  and  124  and may be connected to first intake manifolds  112  and  122  of other separators  110  and  120 . Such second intake manifolds  116  and  126  may be provided as paths for supplying the fuel or the oxidizing agent to the first intake manifolds  112  and  122  of the other separators  110  and  120 . 
     In addition, the second exhaust manifolds  118  and  128  may be provided outwardly of the first intake manifolds  112  and  122  and may be connected to the first exhaust manifolds  114  and  124  of the other separators  110  and  120 . 
     As described above, according to the present embodiment, both end portions of the separator bodies may be provided with the second exhaust manifolds  118  and  128  and the first intake manifolds  112  and  122  arranged in two rows and the second intake manifolds  116  and  126  and the first exhaust manifolds  114  and  124  arranged in two rows. 
     Therefore, the gases, namely, the fuel or the oxidizing agent, supplied by the first intake manifolds  112  and  122  may pass through spaces between the second intake manifolds  116  and  126  to be discharged through the first exhaust manifolds  114  and  124 . 
     Meanwhile, according to the present embodiment, the fuel may include gaseous hydrogen. In addition, the oxidizing agent may include gaseous oxygen. 
     Furthermore, pure oxygen may be used as the gaseous oxygen. In the present embodiment, air containing oxygen may also be used. 
     Meanwhile, according to the present embodiment, the separators  110  and  120  may be stacked together with adjacent other separators  110  and  120 , while having the electrolyte membranes interposed therebetween. 
     At this time, the fuel may be circulated to one separator  110  and the oxidizing agent may be circulated to the other separator  120 . Here, the electrolyte membrane may block the permeation of the fuel and the oxidizing agent, have no electronic conductivity and allow oxygen ions or hydrogen ions to be permeated therethrough. 
     Therefore, through an electrochemical reaction between the fuel passing through one cell and the oxidizing agent passing through the other cell, the hydrogen ions of the fuel or the oxygen ions of the oxidizing agent may pass through the electrolyte membrane to trigger an oxidation-reduction reaction to thereby produce water (H 2 O), and during this procedure, electrons are generated. Such a reaction is represented by the following chemical formula 1 or chemical formula 2:
 
Cathode:½O 2 +2 e   −   O −2  
 
Anode:O −2 +H 2   H 2 O+2 e   −   [Chemical Formula 1]
 
Cathode:½O 2 +2H + →H 2 O
 
Anode:H 2 →2H + +2 e   −   [Chemical Formula 2]
 
     The fuel cell  100 , according to the exemplary embodiment, may improve the flow distribution in the horizontal direction, without a reduction in the effective flow area of the gases, the fuel or the oxidizing agent, supplied by the first intake manifolds  112  and  122  of the separators  110  and  120 , to thereby increase the actual circulation flow. Thus, the fuel utilization rate and reactivity may be improved. 
     MODE FOR CARRYING OUT THE INVENTION 
       FIG. 11  is a view illustrating a reaction region of a separator for a fuel cell according to an exemplary embodiment in the present disclosure. 
     Meanwhile, according to the present embodiment, the separators  110  and  120  for the fuel cell  100  may have a reaction region formed while the gases introduced into the first intake manifolds  112  and  122  are being discharged through the first exhaust manifolds  114  and  124 . 
     In the fuel cell  100  according to the exemplary embodiment, the separators  110  and  120  may have the first intake manifolds  112  and  122  and the first exhaust manifolds  114  and  124  corresponding thereto, wherein the gas from the first intake manifolds  112  may be discharged through a single first exhaust manifold  114  and the gas from the first intake manifolds  122  may be discharged through a single first exhaust manifold  124 , and may have the second intake manifolds  116  and  126  and the second exhaust manifolds  118  and  128  connected to the first intake manifolds  112  and  122  and the first exhaust manifolds  114  and  124  of other separators  110  and  120 , respectively. However, the present inventive concept is not limited thereto, and various modifications may be made. 
     For example, referring to  FIG. 12 , the fuel or the oxidizing agent introduced into three first intake manifolds  112  or  122  of the separators  110  or  120  of the fuel cell  100 , which are connected to second intake manifolds  116  or  126  of other separators  110  or  120  thereof, may be discharged through a single first exhaust manifold  114  or  124 . In addition, the first exhaust manifolds  114  and  124  may be connected to second exhaust manifolds  118  and  128  of the other separators  110  or  120 , respectively. 
     As described above, according to the present embodiment, the first intake manifolds  112  and  122  and the first exhaust manifolds  114  and  124  may be sequentially arranged in two rows, unlike the alternate arrangement according to the related art, such that the fuel or the oxidizing agent is supplied in the front row, passes through the reaction region, and then the reacted fuel or oxidizing agent is discharged in the rear row. 
     In addition, the separators  110  and  120  may be provided to intersect perpendicularly, and accordingly, for example, the fuel may be circulated in one separator  110  while the oxidizing agent may be circulated in the other separator  120  in a direction perpendicular to the direction of fuel circulation. 
     Furthermore, the separators  110  and  120  may be provided with guide protrusions  119  for guiding the circulation of the fuel or the oxidizing agent. 
     Meanwhile, according to the present embodiment, the connections of the manifolds provided in the fuel cell  100  are illustrated to help in visualization thereof, but are not limited thereto and may be modified in various manners. For example, the manifolds may be connected below the separators. Specifically, the first intake manifolds  112  and  122 , the first exhaust manifolds  114  and  124 , the second intake manifolds  126  and  128  and the second exhaust manifolds  118  and  128  of the separators  110  and  120  may be connected below other separators  110  and  120 , while passing through other separators. 
     While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present invention as defined by the appended claims.