Abstract:
A fuel cell stack includes a number of modularized plate structures including an anode plate, a cathode plate, water coolant plates and air coolant plates. The anode and cathode plates are designed to form hydrogen and air channels that allow for uniform distribution and even flow of hydrogen and air through the channels with the channels of each particular plate having substantially identical length in order to enhance electrochemical reaction between hydrogen and oxygen contained in the air with respective catalysts in the fuel cell stack. Also a sufficient amount of air is allowed to flow through the cathode plate to enhance output power of the fuel cell stack. The coolant plates adapt a split design, which introduces turbulence in the coolant channels to enhance heat removal.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to the field of fuel cells, and in particular to a modularized separate plate structure for forming a fuel cell stack. 
   2. Description of the Prior Art 
   Fuel cell power system is capable of generating electrical power energy by means of electrochemical reaction between a fuel, such as hydrogen and methanol, and an oxidizer, such as oxygen. The fuel cell is classified, based on the electrolyte thereof, as proton exchange membrane fuel cell or polymer electrolyte membrane fuel cell, abbreviated as PEMFC or PEM, alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC) and solid oxide fuel cell (SOFC). 
   Among these known fuel cells, the PEMFC is the best-developed technique, having the advantages of low operation temperature, fast start-up and high power density. Thus, the PEMFC is very suitable for transportation vehicles and power generation systems, such as home power systems and other portable and stationary power generation systems. 
   The fuel cell generates electrical energy through electrochemical reaction of hydrogen and oxygen, with water as by-product. Basically, the electrochemical reaction occurred in the fuel cell stack is a reverse reaction of electrolysis of water, in which chemical energy is transferred into electrical energy. The fuel cell comprises anode and cathode plates separated from each other with electrolyte arranged between and in physical contact with both the anode and the cathode. A circuit  20  is also incorporated in the fuel cell for conduction of the electricity out of the fuel cell. A typical structure of the fuel cell is shown in  FIG. 1  of the attached drawings, comprising an anode plate  10  and a cathode plate  14  opposite to and spaced from each other with electrolyte  18  provided therebetween. A catalyst  12  is provided at the anode plate  10 . When hydrogen is conducted to the anode plate  10  and catalyzed by the catalyst  12  the following reaction is carried out at the anode:
 
H 2 →2H + +2e − 
 
   The hydrogen ions produced at the anode  10  migrate through the electrolyte  18  and reach the cathode plate  14 . Meanwhile, oxygen is conducted to the cathode  14  in which a catalyst  16  is provided. With the catalysis of the catalyst  16 , oxygen undergoes the following reaction with hydrogen ions at the cathode:
 
½O 2 +2H + +2e − →H 2 O
 
with water as reaction product.
 
   Besides water, the electrochemical reaction also generates heat. To prevent the fuel cell from overheating and maintain it at high performance, a cooling means is commonly employed in the modularized fuel cell stack in order to properly and timely remove heat from the fuel cell stack. An example of the cooling means is a cooling plate structure that is incorporated in a fuel cell to remove heat therefrom. Water, air and the likes can be employed as coolant that circulates through the cooling plate for heat removal. 
   To optimize the operation efficiency of a particular fuel cell, the anode plate and the cathode plate, as well as the cooling plate, must be configured so that gases, including hydrogen, oxygen and air, are allowed to flow through the plates in a substantially uniform manner. In designing the plates, the following factors are critical and should be considered: (1) the uniform flowing of gases through all the channels formed inside each plate, (2) the consistency of the length of channels for even distribution of gases, (3) the maximal and uniform contact of gases with the catalysts in each channel for undergoing electrochemical reaction in the channel and (4) the flow rates of gases for maintaining the electrochemical reaction that is sufficient to supply the desired amount of electricity. Besides, in case of the cooling plate, sufficiency and efficiency in removing heat is another factor to be taken into account. 
   SUMMARY OF THE INVENTION 
   Thus, an object of the present invention is to provide a fuel cell stack comprising modularized stackable plates, including an anode plate, a cathode plate, an air cooling plate and a water cooling plate, those plate having a structure that allows gases to evenly flow through each channel of the plates, that forms channels for gas flow having substantially identical length, that allows for uniform reaction induced in each channel and that allows for sufficient flow rates for gases in the plates, as well as that allows for sufficient and efficient removal of heat from the fuel cell stack. 
   To achieve the above object, in accordance with the present invention, there is provided a fuel cell stack comprising modularized electrode plates, including an anode plate and a cathode plate, having a structure that allows hydrogen and oxygen to flow through channels formed therein. The channels have substantially the same length, so that hydrogen and oxygen can flow and be distributed evenly in each channel and undergo reaction with the catalysts in the channels. Meanwhile, sufficient hydrogen and oxygen are provided to generate enhanced output power. The fuel cell stack selectively comprises air cooling plate and water cooling plate having a structure that creates turbulent flow of air and water in order to efficiently remove heat from the fuel cell stack. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which: 
       FIG. 1  is a schematic view of a typical fuel cell; 
       FIG. 2  is a plan view of an anode plate for a fuel cell stack constructed in accordance with the present invention; 
       FIG. 3  is a plan view of a cathode plate for the fuel cell stack of the present invention; 
       FIG. 4  is a plan view of a water cooling plate for the fuel cell stack of the present invention; 
       FIG. 5  is a plan view of an air cooling plate for the fuel cell stack of the present invention; and 
       FIG. 6  is a perspective view of a fuel cell stack comprised of the anode plate, the cathode plate, and the water cooling plate in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to the drawings and in particular to  FIG. 2 , in which an anode plate constructed in accordance with the present invention to be incorporated in a fuel cell stack is shown, the anode plate that is generally designated with reference numeral  30  in the drawings comprises a substantially rectangular structure having a second edge  38 , a first edge  34  opposite to the second edge  38 , a third edge  66  and a fourth edge  72  opposite to the third edge  66 , the edges  34 ,  38 ,  66 ,  72  being connected to each other to form the rectangle. Along the first edge  34  of the anode plate  30 , a hydrogen inlet port  32  in the form of an elongated slot having rounded ends is defined in a first half of the first edge  34 . A hydrogen outlet port  36 , also in the form of an elongate slot with rounded ends, is defined in a second half of the second edge  38  whereby the hydrogen inlet and outlet ports  32 ,  36  are substantially opposite to each other in a diagonal direction of the rectangular plate  30 . 
   Hydrogen channels (not labeled) are formed in a first guide zone  40  of the anode plate  30  and are connected to and in fluid communication with the hydrogen inlet port  32 . The hydrogen channels in the first guide zone  40  are arranged to be substantially parallel to each other and normal to the length of the hydrogen inlet port  32 . In other words, the hydrogen channels in the first guide zone  40  are parallel to the third and the fourth edges  66 ,  72  and perpendicular to the first and second edges  34 ,  38 . 
   Each hydrogen channel forms a first arcuate connection  42  which redirects the hydrogen channel to a direction substantially normal to that of the hydrogen channel in the first guide zone  40 . Thus, the hydrogen channels are extended in a second guide zone  44  of the anode plate  30  in a direction normal to the third and fourth edges  66 ,  72  and parallel to the first and second edges  34 ,  38 . The arcuate connection  42  is configured to smoothen flowing of gas therethrough and between sections of the hydrogen channels in the guide zones  40 ,  44 . The hydrogen channels in the second guide zone  44  are substantially parallel to each other and the length of the hydrogen inlet port  32 . 
   Each hydrogen channel forms a second arcuate connection  46 , opposite to the first arcuate connection  42 , which redirects the hydrogen channel to a direction substantially normal to that of the hydrogen channel in the second guide zone  44 . Thus, the hydrogen channels are extended in a third guide zone  48  of the anode plate  30  in a direction parallel to the third and fourth edges  66 ,  72  and normal to the first and second edges  34 ,  38 . The second arcuate connection  46  is configured to smoothen flowing of gas therethrough and between sections of the hydrogen channels in the guide zones  44 ,  48 . The hydrogen channels are substantially parallel to each other in the third guide zone  48  and normal to the length of the hydrogen inlet port  32 . 
   Each hydrogen channel forms a third arcuate connection  50 , opposite to the second arcuate connection  46 , which redirects the hydrogen channel to a direction substantially normal to that of the hydrogen channel in the third guide zone  48 . Thus, the hydrogen channels are extended in a fourth guide zone  52  of the anode plate  30  in a direction normal to the third and fourth edges  66 ,  72  and parallel to the first and second edges  34 ,  38 . The arcuate connection  50  is configured to smoothen flowing of gas therethrough and between sections of the channels in the guide zones  48 ,  52 . The hydrogen channels in the fourth guide zone  52  are substantially parallel to each other and the length of the hydrogen inlet port  32 . 
   Each hydrogen channel forms a fourth arcuate connection  54 , opposite to the third arcuate connection  50 , which redirects the hydrogen channel to a direction substantially normal to that of the hydrogen channel in the fourth guide zone  52 . Thus, the hydrogen channels are extended in a fifth guide zone  56  of the anode plate  30  in a direction parallel to the third and fourth edges  66 ,  72  and normal to the first and second edges  34 ,  38 . The fourth arcuate connection  54  is configured to smoothen flowing of gas therethrough and between sections of the hydrogen channels in the guide zones  52 ,  56 . The hydrogen channels are substantially parallel to each other in the fifth guide zone  56  and normal to the length of the hydrogen inlet port  32  and are connected to and in fluid communication with the hydrogen outlet port  36 . Thus, the hydrogen channels are connected between the hydrogen inlet and outlet ports  32 ,  36  and have an S-shaped configuration in the anode plate  30 , including sections in the guide zones  40 ,  44 ,  48 ,  52 ,  56 . Unreacted hydrogen in the fuel cell stack is discharged through the hydrogen outlet port  36 . 
   Such a structure of anode plate  30  allows for hydrogen to be evenly distributed in the channels and uniformly flow through all the hydrogen channels between the hydrogen inlet and outlet ports  32 ,  36 . Each hydrogen channel including sections in the guide zones  40 ,  44 ,  48 ,  52 ,  56  has substantially identical length. Uniform reaction between the hydrogen flowing through each hydrogen channel and the catalyst is performed. The S-shaped configuration of each hydrogen channel between the hydrogen inlet and outlet ports  32 ,  36 , including the sections in the guide zones  40 ,  44 ,  48 ,  52 ,  56  maximize the overall length of the channels in the anode plate  30 , which in turn brings the hydrogen with enhanced efficiency of reaction inside the fuel cell stack. 
   The anode plate  30  further comprises a coolant inlet port  58  that is defined in a first half of the second edge  38  of the anode plate  30 . In other words, the coolant inlet port  58  is arranged above the hydrogen outlet port  36 . The coolant that is used for cooling may be cooling water or air. A coolant outlet port  60  is defined in a second half of the first edge  34  of the anode plate  30 , below the hydrogen inlet port  32 . The coolant, such as air and water, is allowed to discharge through the coolant output port  60 . Both the coolant inlet and outlet ports  58  and  60  are elongate slots with rounded ends. The coolant inlet and outlet ports  58 ,  60  are not in fluid communication with the hydrogen channels of the anode plate  30 . 
   The anode plate  30  also defines a plurality of air inlet ports  62 ,  64 , in the form of elongate slot with rounded ends, along the third edge  66  of the anode plate  30 . The air inlet ports  62 ,  64  are arranged end by end along the third edge  66 . A plurality of air outlet ports  68 ,  70  are defined along the fourth edge  72 . The air outlet ports  68 ,  70  are in the form of elongate slots having rounded ends and are arranged end by end along the fourth edge  72  of the anode plate  30 . The air inlet and outlet ports  62 ,  64 ,  68 ,  70  are not in fluid communication with the hydrogen channels of the anode plate  30 . 
     FIG. 3  shows a plan view of a cathode plate constructed in accordance with the present invention to be incorporated in a fuel cell stack. The cathode plate that is broadly designated with reference numeral  80  comprises a substantially rectangular structure having a first edge  86  and a second edge  92  opposite to the first edge  86 , a third edge  102 , a fourth edge  106  opposite to the third edge  102 , the edges  102 ,  106 ,  86 ,  92  being connected to each other to form the rectangle. Along the first edge  86  of the cathode plate  80 , air inlet ports  82 ,  84  in the form of elongate slots having rounded ends are defined in an end by end manner. Air outlet ports  88 ,  90 , also in the form of elongate slots with rounded ends, are defined in and along the second edge  92  in an end by end manner. Air channels (not labeled) are formed in a guide zone  98  of the cathode plate  80  and straightly extend between and in fluid communication with the air inlet and outlet ports  82 ,  84 ,  88 ,  90 . The air channels run parallel to each other and the third and fourth edges  102 ,  106  and thus substantially perpendicular to length of the air inlet and outlet ports  82 ,  84 ,  88 ,  90 . Air that contains oxygen for reaction with hydrogen in the fuel cell stack is allowed to enter the cathode plate  80  via the air inlet ports  82 ,  84 , traveling through the air channels in a linear manner and finally leaves the cathode plate  80  via the air outlet ports  88 ,  90 . 
   Such a structure of the cathode plate  80  allows the air to be evenly distributed in and uniformly flow through all the air channels between the air inlet and outlet ports  82 ,  84 ,  88 ,  90  for uniform reaction between the oxygen contained in the air flowing through each channel and the catalyst. The air inlet ports  82 ,  84  and the air outlet ports  88 ,  90  of the cathode plate  80 , as well as the air channels in the guide zone  98  of the cathode plate  80 , allows a sufficient amount of air to pass therethrough in order to meet the requirement of great consumption of oxygen in the chemical reaction occurring in the fuel cell stack. Thus, output power of the fuel cell stack is enhanced. 
   The cathode plate  80  forms a hydrogen inlet port  100 , which is in the form of an elongate slot having rounded ends, in a first half of the third edge  102  and a hydrogen outlet port  104 , which is also in the form of an elongate slot having rounded ends, in a second half of the fourth edge  106  whereby the hydrogen inlet and outlet ports  100 ,  104  are opposite to each other in a diagonal direction of the rectangle  80 . The hydrogen inlet and outlet ports  100 ,  104  are not in fluid communication with the air channels. 
   The cathode plate  80  further defines a coolant inlet port  108  that is defined in a first half of the fourth edge  106  of the cathode plate  80 . In other words, the coolant inlet port  108  is arranged above the hydrogen outlet port  104 . A coolant outlet port  110  is defined in a second half of the third edge  102  of the cathode plate  80 , below the hydrogen inlet port  100 . Coolant, such as air and water, is allowed to circulate through the fuel cell stack by passing through the coolant inlet port  108  for flowing into the fuel cell stack and the coolant outlet port  110  for flowing out of the fuel cell stack. Both the coolant inlet and outlet ports  108 ,  110  are elongate slots with rounded ends and are not in fluid communication with the air channels of the cathode plate  80 . 
   The anode plate  30  and the cathode plate  80  are stackable together as a dual-electrode plate in which the air inlet ports, air outlet ports, hydrogen inlet ports, hydrogen outlet ports, coolant inlet ports and coolant outlet ports are respectively connected together to allow air, hydrogen and coolant to flow in and out of the dual-electrical plate. However, the hydrogen channels formed in the anode plate  30  and the air channels formed in the cathode plate  80  are separated from each other. Thus, the oxygen contained in the air and the hydrogen should not get mixed randomly and instead they are involved in the reactions in the anode and the cathode respectively. 
     FIG. 4  shows an embodiment of a cooling plate constructed in accordance with the present invention in which water is adopted as coolant flowing through the coolant plate. The water cooling plate, which is broadly designated with reference numeral  120 , comprises a substantially rectangular structure having a first edge  124 , a second edge  128  opposite to the first edge  124 , a third edge  148  and a fourth edge  154  opposite to the third edge  148 , the edges  124 ,  128 ,  148 ,  154  being connected to each other to form the rectangle. Along the first edge  124  of the water cooling plate  120 , a coolant water inlet port  122  in the form of an elongate slot having rounded ends is defined in a first half of the first edge  124 . A coolant water outlet port  126 , also in the form of an elongate slot with rounded ends, is defined in a second half of the second edge  128  whereby the coolant water inlet and outlet ports  122 ,  126  are substantially opposite to each other in a diagonal direction of the rectangular plate  120 . 
   Coolant channels (not labeled) are formed in a first guide zone  130  of the coolant plate  120  and are connected to and in fluid communication with the coolant water inlet port  122 . The coolant channels in the first guide zone  130  are arranged to be substantially parallel to each other and normal to the length of the coolant water inlet port  122 . In other words, the coolant channels are parallel to the third and the fourth edges  148 ,  154  and perpendicular to the first and second edges  124 ,  128 . 
   Each coolant channel forms a first arcuate connection  132  which redirects the coolant channel to a direction substantially normal to that of the coolant channel in the first guide zone  130  and splits the coolant channel into two parallel sub-channels in a second guide zone  134  in which the sub-channels are extended in a direction normal to the third and fourth edges  148 ,  154  and parallel to the second and first edges  124 ,  128 . The arcuate connection  132  is configured to smoothen the flowing of coolant therethrough and between sections of the coolant channels in the guide zones  130 ,  134 . The sub-channels in the second guide zone  134  are substantially parallel to each other and the length of the coolant water inlet port  122 . 
   Each coolant channel forms a second arcuate connection  136 , opposite to the first arcuate connection  132 , which redirects the sub-channels of the coolant channel in the second guide zone  134  to a direction substantially normal to that of the sub-channels and joint the sub-channels to a single coolant channel in a third guide zone  138  in which the channel is extended in a direction parallel to the third and fourth edges  148 ,  154  and normal to the second and first edges  128 ,  124 . The second arcuate connection  136  is configured to smoothen the flowing of coolant therethrough and between sections of the channels in the guide zones  134 ,  138 . The coolant channels in the third guide zone  138  are substantially parallel to each other and normal to the length of the coolant water inlet port  122 . The coolant channels are connected to and in fluid communication with the coolant water outlet port  126  whereby coolant water that flows into the cooling plate  120  via the coolant water inlet port  122  flows through sections of the coolant channels in the guide zones  130 ,  134 ,  138  toward the coolant water outlet port  126  for bringing away heat generated during the operation of the fuel cell stack. 
   Each coolant channel is split into two or even more sub-channels in the second guide zone  134  of the coolant plate  120 . This introduces turbulence in the coolant flow for enhancing heat removal from the fuel cell stack. 
   The cooling plate  120  further defines a hydrogen inlet port  140  in the form of an elongate slot having rounded ends that is formed in a first half of the second edge  128  of the coolant plate  120  and is thus located above the coolant water outlet port  126 . A hydrogen outlet port  142 , also in the form of an elongate slot having rounded ends, is defined in a second half of the first edge  124  of the coolant plate  120 , below the coolant water inlet port  122 . Both the hydrogen inlet and outlet ports  140  and  142  are not in fluid communication with the coolant channels of the cooling plate  120 . Air inlet ports  144 ,  146 , in the form of elongate slots having rounded ends, are defined along the third edge  148  and arranged in an end by end manner, while air outlet ports  150 ,  152 , in the form of elongate slots having rounded ends, are defined along the fourth edge  154  and also arranged in an end by end manner. The air inlet and outlet ports  144 ,  146 ,  150 ,  152  are not in fluid communication with the coolant channels of the cooling plate  120 . 
   The cooling plate  120  and the anode plate  30  are stackable together as a composite anode structure having individual cooling means in which the air inlet ports, air outlet ports, hydrogen inlet ports, hydrogen outlet ports, coolant inlet ports and coolant outlet ports are respectively connected together to allow air, hydrogen and coolant to flow in and out of the composite anode structure. 
   Similarly, the cooling plate  120  and the cathode plate  80  are stackable together as a composite cathode structure having individual cooling means in which the air inlet ports, air outlet ports, hydrogen inlet ports, hydrogen outlet ports, coolant inlet ports and coolant outlet ports are respectively connected together to allow air, hydrogen and coolant to flow in and out of the composite cathode structure. 
     FIG. 5  shows another embodiment of the cooling plate constructed in accordance with the present invention in which air is adopted as coolant flowing through the cooling plate. The cooling plate, which is broadly designated with reference numeral  160 , comprises a substantially rectangular structure having a first edge  164 , a second edge  168  opposite to the first edge  164 , a third edge  188  and a fourth edge  194  opposite to the third edge  188 , the edges  164 ,  168 ,  168 ,  194  being connected to each other to form the rectangle. Along the first edge  164  of the cooling plate  160 , a coolant air inlet port  162  in the form of an elongate slot having rounded ends is defined in a first half of the first edge  164 . 
   Air coolant channels (not labeled) are formed in a first guide zone  170  of the cooling plate  160  and are connected to and in fluid communication with the coolant air inlet port  162 . The coolant channels in the first guide zone  170  are arranged to be substantially parallel to each other and normal to the length of the coolant air inlet port  162 . In other words, the coolant channels are parallel to the third and the fourth edges  188 ,  194  and perpendicular to the first and second edges  164 ,  168 . 
   Each coolant channel forms a first arcuate connection  172  which redirects the coolant channel to a direction substantially normal to that of the coolant channel in the first guide zone  170  and splits the coolant channel into two parallel sub-channels in a second guide zone  174  in which the sub-channels are extended in a direction normal to the third and fourth edges  188 ,  194  and parallel to the second and first edges  164 ,  168 . The arcuate connection  172  is configured to smoothen the flowing of coolant therethrough and between sections of the coolant channels in the guide zones  170 ,  174 . The sub-channels in the second guide zone  174  are substantially parallel to each other and the length of the coolant air inlet port  162 . 
   Each coolant channel forms a second arcuate connection  176 , opposite to the first arcuate connection  172 , which redirects the sub-channels of the coolant channel in the second guide zone  174  to a direction substantially normal to that of the sub-channels and joint the sub-channels to a single coolant channel in a third guide zone  178  in which the channel is extended in a direction parallel to the third and fourth edges  188 ,  194  and normal to the second and first edges  168 ,  164 . The second arcuate connection  176  is configured to smoothen the flowing of coolant flow therethrough and between sections of the channels in the guide zones  174 ,  178 . The coolant channels in the third guide zone  178  are substantially parallel to each other and normal to the length of the coolant air inlet port  162 . Each coolant channel has an end opening  166  at a second half of the second edge  168  to directly discharge the air into the surroundings. 
   Each coolant channel is split into two or even more sub-channels in the second guide zone  174  of the coolant plate  160 . This introduces turbulence in the coolant flow for enhancing heat removal from the fuel cell stack. 
   The cooling plate  160  further defines a hydrogen inlet port  180  in the form of an elongate slot having rounded ends that is formed in a first half of the second edge  168  of the cooling plate  160  and is thus located above the coolant channel end openings  166 . A hydrogen outlet port  182 , also in the form of an elongate slot having rounded ends, is defined in a second half of first edge  164  of the cooling plate  160 , below the coolant air inlet port  162 . Both the hydrogen inlet and outlet ports  180  and  182  are not in fluid communication with the coolant channels of the coolant plate  160 . Air inlet ports  184 ,  186 , in the form of elongate slots having rounded ends, are defined along the third edge  188  and arranged in an end by end manner, while air outlet ports  190 ,  192 , in the form of elongate slots having rounded ends, are defined along the fourth edge  194  and also arranged in an end by end manner. The air inlet and outlet ports  184 ,  186 ,  190 ,  192  are not in fluid communication with the coolant channels of the cooling plate  160 . 
   The cooling plate  160  and the anode plate  30  are stackable together as a composite anode structure having individual cooling means in which the air inlet ports, air outlet ports, hydrogen inlet ports, hydrogen outlet ports, coolant inlet ports and coolant outlet ports are respectively connected together to allow air, hydrogen and coolant to flow in and out of the composite anode structure. 
   Similarly, the cooling plate  160  and the cathode plate  80  are stackable together as a composite cathode structure having individual cooling means in which the air inlet ports, air outlet ports, hydrogen inlet ports, hydrogen outlet ports, coolant inlet ports and coolant outlet ports are respectively connected together to allow air, hydrogen and coolant to flow in and out of the composite cathode structure. 
   To this point, it is apparent that the present invention provides an anode plate, a cathode plate, a water cooling plate and an air cooling plate for forming a fuel cell stack. These plates are allowed to combined arbitrarily to form the fuel cell stack as shown in  FIG. 6  wherein a fuel cell, designated with reference numeral  200 , comprises an anode plate  30 , a cathode plate  80  and a water cooling plate  120  stacked together. The fuel cell is provided with a main hydrogen inlet  202  and a main hydrogen outlet  204  which are connected to and in fluid communication with the hydrogen inlet and outlet ports formed in the plates  30 ,  80 ,  120  and the hydrogen channels defined in the anode plate  30  for circulating hydrogen through the fuel cell stack. The fuel cell is also provided with a main air inlet  210  which is connected to and in fluid communication with the air inlet and outlet ports formed in the plates  30 ,  80 ,  120  and the air channels defined in the cathode plate  80  for drawing and circulating air containing oxygen into and through the fuel cell stack. The air is eventually discharged out of the fuel cell via a main air outlet not shown in the drawing. In addition, a main coolant inlet  206  and a main coolant outlet  208  are formed on the fuel cell stack and are connected to and in fluid communication with the coolant inlet and outlet ports formed in the plates  30 ,  80 ,  120  and the coolant channels defined in the coolant plate  120  for circulating coolant through the fuel cell stack. It is noted that the cooling plate  120  may be replaced or additionally combined with the cooling plate  160  shown in  FIG. 5 . 
   It is apparent to those skilled in the art to add other components that are musts to the operation of the fuel cell or that enhances the operation efficiency and convenience to the fuel cell stack, such as proton exchange membrane, electric conducting plates or end plates. 
   Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.