Patent Publication Number: US-2003228507-A1

Title: Humidifing module and its unit cell for fuel cell

Description:
BACKGROUND OF THE INVENTION  
       [0001] Field of the Invention  
       [0002] The invention relates to a module for humidifying a fuel cell and a unit cell for assembling the module; in particular, to a humidifying module and its unit cell that can maintain humidity in a fuel cell.  
       [0003] Description of the Related Art  
       [0004] Fuel cells have been developed to reduce polluting emissions generated by combustion engines.  
       [0005] In fuel cells, water and electric energy are generated by hydrogen gas reacting with oxygen gas during electrochemical reaction. Generally a fuel cell includes an anode, a cathode, an electrolyte, and a circuit. Hydrogen gas is introduced into the anode, and oxygen gas (or air) is introduced into the cathode. Hydrogen ions in the anode move to the cathode through the electrolyte, and electrons in the anode move to the cathode through the circuit. Oxygen gas reacts in the cathode so that water is generated and electric energy is released.  
       [0006] Types of fuel cells include an alkaline fuel cell (AFC), a phosphoric acid fuel cell (PAFC), a solid oxide fuel cell (SOFC), a molten carbonate fuel cell (MCFC), a proton exchange membrane fuel cell (PEMFC). Each type of fuel cell has different advantages, disadvantages, and different areas of application. The design of this invention is based on the proton exchange membrane fuel cell, and a detailed description of the proton exchange membrane fuel cell is described in the following.  
       [0007] A proton exchange membrane, when used as an electrolyte, in a proton exchange membrane fuel cell, requires liquid water to transmit protons (hydrogen ions). However, when cool, dry air enters the hotter fuel cell, most of water content in the proton exchange membrane evaporates due to the temperature differential. Thus, the water content in the proton exchange membrane is dramatically reduced, and protons cannot be effectively transmitted in the proton exchange membrane.  
       [0008] In the conventional proton exchange membrane fuel cell, a device for humidifying air is usually utilized. However, the humidifying device is disposed outside of the fuel cell, and additional power is required to actuate the humidifying device. As a result, the whole system becomes complicated, and its volume and weight increase.  
       SUMMARY OF THE INVENTION  
       [0009] In view of this, the invention provides a humidifying module and its unit cell thereof that maintains a predetermined humidity in a fuel cell.  
       [0010] Accordingly, the invention provides a unit cell including a first guiding plate, a second guiding plate, and an intermediate layer. The first guiding plate, communicating with the fuel cell, includes a plurality of first grooves so that air flows to the fuel cell via the first grooves. The second guiding plate, communicating with the fuel cell, includes a plurality of second grooves so that gas from the fuel cell flows out of the unit cell via the second grooves. The second grooves face the first grooves. The intermediate layer is disposed between the first guiding plate and the second guiding plate, and prevents the air flowing in the first grooves from mixing with the gas flowing in the second grooves. Water content in the gas flowing in the second grooves is transmitted to the first grooves.  
       [0011] In a preferred embodiment, the intermediate layer includes a water-permeable layer, a first water-absorbent layer, and a second water-absorbent layer. The water content of the gas, flowing in the second grooves, passes through the water-permeable layer. The first water-absorbent layer is disposed on a surface, facing the second guiding plate, of the water-permeable layer. The water content of the gas, flowing in the second grooves, is absorbed by the first water-absorbent layer. The second water-absorbent layer is disposed on a surface, facing the first guiding plate, of the water-permeable layer. The water content, passing through the water-permeable layer, is absorbed by the second water-absorbent layer.  
       [0012] Furthermore, the first water-absorbent layer and the second water-absorbent layer are adhered to the water-permeable layer. The water-permeable layer is made of material for preventing gas from passing through. The first water-absorbent layer and the second water-absorbent layer are made of a hydrophilic material.  
       [0013] In another preferred embodiment, the intermediate layer is adhered to the first guiding plate and the second guiding plate.  
       [0014] In another preferred embodiment, the first grooves and the second grooves are orthogonal.  
       [0015] In another preferred embodiment, the first guiding plate includes a first opening and a second opening formed in a direction that the first grooves extend. The second guiding plate includes a third opening and a fourth opening corresponding to the first opening and the second opening. Thus, the air flows into the first grooves via the first opening and the third opening, and flows out of the unit cell via the second opening and the fourth opening.  
       [0016] In another preferred embodiment, the second guiding plate includes a fifth opening formed in a direction that the second grooves extend. The first guiding plate includes a sixth opening corresponding to the fifth opening. Thus, the gas from the fuel cell flows into the second grooves via the fifth opening and the sixth opening.  
       [0017] Furthermore, the first guiding plate includes a seventh opening opposite from the sixth opening. Thus, the gas, flowing in the second grooves, flows out of the unit cell via the seventh opening.  
       [0018] In another preferred embodiment, the unit cell further includes an expansion plate. The expansion plate is disposed between the first guiding plate and the second guiding plate, and includes a plurality of third grooves facing the first guiding plate and a plurality of fourth grooves facing the second guiding plate.  
       [0019] Furthermore, the third grooves and the fourth grooves are orthogonal, and the third grooves and the first grooves are orthogonal, and the fourth grooves and the second grooves are orthogonal.  
       [0020] Furthermore, the expansion plate includes an eighth opening and a ninth opening formed in a direction that the third grooves extend, and includes a tenth opening and a eleventh opening formed in a direction that the fourth grooves extend.  
       [0021] In this invention, a module, for humidifying a fuel cell, is provided. The module includes a plurality of unit cells communicating with the fuel cell respectively. The unit cell includes a first guiding plate, a second guiding plate, and an intermediate layer. The first guiding plate, communicating with the fuel cell, includes a plurality of first grooves so that air flows to the fuel cell via the first grooves. The second guiding plate, communicating with the fuel cell, includes a plurality of second grooves so that gas from the fuel cell flows out of the unit cell via the second grooves. The second grooves face the first grooves. The intermediate layer is disposed between the first guiding plate and the second guiding plate, and prevents the air flowing in the first grooves from mixing with the gas flowing in the second grooves. Water content in the gas flowing in the second grooves is transmitted to the first grooves.  
       [0022] In this invention, a unit cell, for humidifying a fuel cell, is provided. The unit cell communicates with a fluid supply source, and includes a first guiding plate, a second guiding plate, and an intermediate layer. The first guiding plate communicates with the fuel cell, and includes a plurality of first grooves so that air flows to the fuel cell via the first grooves. The second guiding plate communicates with the fluid supply source, and includes a plurality of second grooves so that fluid from the fluid supplying device flows out of the unit cell via the second grooves. The second grooves face the first grooves. The intermediate layer is disposed between the first guiding plate and the second guiding plate, and prevents the air flowing in the first grooves from mixing with the fluid flowing in the second grooves. Water content in the fluid flowing in the second grooves is transmitted to the first grooves. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0023] The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
     [0024]FIG. 1 is an exploded view of a unit cell for humidifying a fuel cell as disclosed in a first embodiment of this invention;  
     [0025]FIG. 2 a  is a front view of a first guiding plate in FIG. 1;  
     [0026]FIG. 2 b  is a rear view of a first guiding plate in FIG. 1;  
     [0027]FIG. 3 a  is a front view of a second guiding plate in FIG. 1;  
     [0028]FIG. 3 b  is a rear view of a second guiding plate in FIG. 1;  
     [0029]FIG. 4 a  is a schematic view of an assembled unit cell in FIG. 1;  
     [0030]FIG. 4 b  is a cross section along a line b-b in FIG. 4 a;    
     [0031]FIG. 4 c  is a cross section along a line c-c in FIG. 4 a;    
     [0032]FIG. 5 is a schematic view of a module for humidifying a fuel cell as disclosed in a first embodiment of this invention;  
     [0033]FIG. 6 a  is an exploded view of a unit cell for humidifying a fuel cell as disclosed in a second embodiment of this invention;  
     [0034]FIG. 6 b  is a front view of an expansion plate in FIG. 6 a;    
     [0035]FIG. 6 c  is a rear view of an expansion plate in FIG. 6 a;    
     [0036]FIG. 7 a  is an exploded view of a unit cell for humidifying a fuel cell as disclosed in a third embodiment of this invention;  
     [0037]FIG. 7 b  is a front view of a first guiding plate in FIG. 7 a;    
     [0038]FIG. 7 c  is a rear view of a first guiding plate and a second guiding plate in FIG. 7 a;    
     [0039]FIG. 7 d  is a front view of a second guiding plate in FIG. 7 a;    
     [0040]FIG. 7 e  is a schematic view of an assembled unit cell in FIG. 7 a ; and  
     [0041]FIG. 8 is a schematic view of a module for humidifying a fuel cell as disclosed in a third embodiment of this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0042] Embodiments  
     [0043] Embodiment 1  
     [0044] Referring to FIGS.  1 - 4   c , a unit cell  100  for humidifying a fuel cell as disclosed in a first embodiment of this invention is shown. The unit cell  100  humidifies air before entering the fuel cell, and includes a first guiding plate  10 , a second guiding plate  20 , and an intermediate layer  30 .  
     [0045] The first guiding plate  10  communicates with the fuel cell  5  as shown in FIG. 4 a , and includes a plurality of first grooves  11  at a surface as shown in FIG. 2 a . Referring to FIG. 2 a  and FIG. 2 b , the first guiding plate  10  is formed with two first openings  12 , two second openings  13 , two sixth openings  14 , and a seventh opening  15  at its periphery. Dry ambient air enters the fuel cell  5  through the first grooves  11  of the first guiding plate  10 . The first openings  12  and the second openings  13  are formed in a direction that the first grooves  11  extend.  
     [0046] The second guiding plate  20  communicates with the fuel cell  5  as shown in FIG. 4 a , and includes a plurality of second grooves  21  at a surface as shown in FIG. 3 a . Referring to FIG. 3 a  and FIG. 3 b , the second guiding plate  20  is formed with two third openings  22 , two fourth openings  23 , and two fifth openings  24  at three sides of its periphery. Exhaust air from the fuel cell  5  flows out of the unit cell  100  through the second grooves  21  of the second guiding plate  20 . The third openings  22  correspond to the first openings  12 , and the fourth openings  23  correspond to the second openings  13 . The fifth openings  24  are formed in a direction that the second grooves  21  extend, and correspond to the sixth openings  14 .  
     [0047] Furthermore, referring to FIG. 1, in the unit cell  100 , the second guiding plate  20  is disposed in a manner such that the second grooves  21  face the first grooves  11 . The first grooves  11  and the second grooves  21  are orthogonal.  
     [0048] Referring to FIG. 4 a , by the first guiding plate  10  and the second guiding plate  20 , dry ambient air enters the first grooves  11  through the first openings  12  and the third openings  22 . Then, dry air flows out of the unit cell  100  via the second openings  13  and the fourth openings  23 , and flows into the fuel cell  5 . After the air is reacted in the fuel cell  5 , it includes lots of vapor and flows out of the fuel cell  5 . Finally, after reaction the air enters the second grooves  21  via the fifth openings  24  and the sixth openings  14 , and directly flows out of the unit cell  100 .  
     [0049] As shown in FIG. 1, the intermediate layer  30  is disposed between the first guiding plate  10  and the second guiding plate  20 , and includes a water-permeable layer  31 , a first water-absorbent layer  32 , and a second water-absorbent layer  33 . The water-permeable layer  31  is used as a base of the intermediate layer  30 , and is made of material for preventing gas from passing through. Thus, the gas flowing in the first grooves  11  can be prevented from mixing with the gas flowing in the second grooves  21  by the water-permeable layer  31 . However, the water content of the gas, flowing in the second grooves  21 , can be transmitted to the first grooves  21  through the water-permeable layer  31 .  
     [0050] The first water-absorbent layer  32  is disposed on a surface, facing the second guiding plate  20 , of the water-permeable layer  31 . The first water-absorbent layer  32  is made of a hydrophilic material, and absorbs the water content of the gas flowing in the second grooves  21 . The second water-absorbent layer  33  is disposed on a surface, facing the first guiding plate  10 , of the water-permeable layer  31 . The second water-absorbent layer  33  is made of a hydrophilic material, and absorbs the water content passing through the water-permeable layer  31 .  
     [0051] Furthermore, the first water-absorbent layer  32  and the second water-absorbent layer  33  are adhered to the water-permeable layer  31  respectively so as to form the intermediate layer  30 . The water-permeable layer  31  is provided with two first adhesive portions  311  and two second adhesive portions  312  at its periphery. By means of the first adhesive portions  311  and the second adhesive portions  312 , the intermediate layer  30  can be adhered to the first guiding plate  10  and the second guiding plate  20 . It is noted that after the first guiding plate  10  is assembled with the second guiding plate  20 , the positions of the first adhesive portions  311  and the second adhesive portions  312  on the water-permeable layer  31  do not interfere with the gas flowing in the first grooves  11  and the second grooves  21 .  
     [0052] As stated above, after the ambient air enters the first grooves  11  of the unit cell  100  via the first openings  12  and the third openings  22  by a blower (not shown), it flows out of the unit cell  100  via the second openings  13  and the fourth openings  23  so as to flow to the cathode of the fuel cell  5 . After the air passes through the cathode of the fuel cell  5 , it re-enters the second grooves  21  of the unit cell  100  via the fifth openings  24  and the sixth openings  14 . Then, the air is directly discharged out of the unit cell  100  and into the ambient. It is noted that after the ambient air passes through the cathode of the fuel cell  5 , its humidity and temperature increase.  
     [0053] By the above process, before the ambient air enters the fuel cell  5 , the water content of the gas with high humidity flowing in the second grooves  21  can be absorbed by the intermediate layer  30 . Thus, the ambient air can be humidified.  
     [0054] Thus, since the cool dry air is humidified by the unit cell  100  of this invention before it enters the hotter fuel cell  5 , the humidity difference in the proton exchange membrane of the fuel cell can be minimized. As a result, the water content in the proton exchange membrane can be largely prevented from evaporating, and the proton in the proton exchange membrane can be smoothly transmitted, thus ensuring the efficiency of the fuel cell.  
     [0055] In addition, the temperature of the ambient air can be increased by the unit cell. Thus, the efficiency of the fuel cell can be further enhanced.  
     [0056] It is understood that in practice, a plurality of unit cells  100  can be assembled into a humidifying module  1  as shown in FIG. 5. Thus, the amount of air entering the fuel cell can be increased.  
     [0057] Embodiment 2  
     [0058] Referring to FIGS. 6 a - 6   c , a unit cell  200  for humidifying a fuel cell as disclosed in a second embodiment of this invention is shown. The unit cell  200  includes a first guiding plate  10 , a second guiding plate  20 , two intermediate layers  30 , and an expansion plate  40 . It is noted that since the first guiding plate  10 , the second guiding plate  20 , and the intermediate layers  30  of this embodiment are the same as those of the first embodiment, their description is omitted.  
     [0059] As shown in FIG. 6 a , the expansion plate  40  is disposed between the first guiding plate  10  and the second guiding plate  20 . One intermediate layer  30  is disposed between the first guiding plate  10  and the expansion plate  40 , and another intermediate layer  30  is disposed between the second guiding plate  20  and the intermediate layer  30 . Referring to FIG. 6 a  and FIG. 6 b , the expansion plate  40  includes a plurality of third grooves  41  at a side facing the first guiding plate  10 , and includes a plurality of fourth grooves  42  at a side facing the second guiding plate  20 . The third grooves  41  and the fourth grooves  42  are orthogonal, and the third grooves  41  and the first grooves  11  are orthogonal, and the fourth grooves  42  and the second grooves  21  are orthogonal.  
     [0060] As shown in FIG. 6 b  and FIG. 6 c , the expansion plate  40  includes two eighth openings  43  and two ninth openings  44  extending in the same direction as the third grooves  41 , and includes two tenth openings  45  and two eleventh openings  46  formed in a direction that the fourth grooves  42  extend.  
     [0061] As stated above, after the ambient air enters the first grooves  11  and the fourth grooves  42  of the unit cell  200  via the first openings  12 , the third openings  22  and the tenth openings  45  by a blower (not shown), it flows out of the unit cell  200  via the second openings  13 , the fourth openings  23  and the eleventh openings  46  so as to flow to the cathode of the fuel cell  5 . After the air passes through the cathode of the fuel cell  5 , it re-enters the second grooves  21  and the third grooves  41  of the unit cell  200  via the fifth openings  24 , the sixth openings  14 , and the eighth openings  43 . The air is evacuated from the unit cell  200  and discharged into the surrounding atmosphere via the seventh openings  15  and the ninth openings  44 .  
     [0062] Thus, the effect of the unit cell  100  can also be attained by the unit cell  200  of this embodiment. In addition, the unit cell  200  offers better expansibility is better than the first embodiment, and is more convenient.  
     [0063] It is understood that in practice, more than one expansion plate can be disposed between two guiding plates.  
     [0064] Furthermore, as with the first embodiment, a plurality of unit cells  200  can be assembled into a humidifying module.  
     [0065] Embodiment 3  
     [0066] Referring to FIGS. 7 a - 7   e , a unit cell  300  for humidifying a fuel cell as disclosed in a third embodiment of this invention is shown. The unit cell  300  includes a first guiding plate  50 , a second guiding plate  60 , and an intermediate layer  30 . It is noted that since the intermediate layer  30  of this embodiment is the same as that of the first embodiment, its description is omitted.  
     [0067] The first guiding plate  50  communicates with the fuel cell  5  as shown in FIG. 7 e , and includes a plurality of first grooves  51  at a surface as shown in FIG. 7 a . Referring to FIG. 7 b , the first guiding plate  50  is formed with two first openings  52 , two second openings  53 , two sixth openings  54 , and two seventh openings  55  at its periphery. Dry ambient air enters the fuel cell  5  through the first grooves  51  of the first guiding plate  50 . The first openings  52  and the second openings  53  are formed in a direction that the first grooves  51  extend.  
     [0068] The second guiding plate  60  communicates with a fluid supply source  6  as shown in FIG. 7 e , and includes a plurality of second grooves  61  at a surface as shown in FIG. 7 d . The second guiding plate  60  is formed with two third openings  62 , two fourth openings  63 , two fifth openings  64 , and two eighth openings  65  at its periphery. Fluid from the fluid supply source  6  flows out of the unit cell  300  through the second grooves  61  of the second guiding plate  60 . The third openings  62  correspond to the first openings  52 , and the fourth openings  63  correspond to the second openings  53 . The fifth openings  64  and the eighth openings  65  are formed in a direction that the second grooves  61  extend, and correspond to the sixth openings  54  and the seventh openings  55 .  
     [0069] As stated above, after the ambient air enters the first grooves  61  of the unit cell  300  via the first openings  52  and the third openings  62  by a blower (not shown), it flows out of the unit cell  300  via the second openings  53  and the fourth openings  63  so as to flow to the cathode of the fuel cell  5 . After the fluid from the fluid supply source  6  enters the second grooves  61  of the unit cell  300  via the fifth openings  64  and the sixth openings  54 , it flows out of the unit cell  300  via the eighth openings  65  and the seventh openings  55 .  
     [0070] The difference between this and the first embodiment is that an additional fluid supply source  6  is utilized. Specifically, in the first embodiment, ambient air is humidified by the gas passed through the fuel cell before entering the fuel cell. In contrast, in this embodiment, the ambient air before entering the fuel cell is humidified by the fluid from the fluid supply source. Thus, the selectivity of the fluid for humidifying is enhanced. For example, both the gas and the liquid can be used as the humidifying fluid. As a result, the characteristics of the humidifying fluid, such as the humidity and the temperature, can be obtained properly so that the humidifying effect can be achieved. However, since the fluid supply source is additionally disposed, the space occupied by the device is larger than that of the first embodiment.  
     [0071] Furthermore, the first guiding plate and the second guiding plate of this embodiment can be replaced with those of the first embodiment.  
     [0072] Furthermore, as with the first embodiment, a plurality of unit cells  300  can be assembled into a humidifying module  3  as shown in FIG. 8.  
     [0073] Furthermore, like the second embodiment, the expansion plate can be disposed in the unit cell  300  so as to enhance the expansibility.  
     [0074] While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to include various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.