Abstract
Disclosed is a method for dynamic variable humidity control; wherein the flow rate of the working gas flow is changed repeatedly according to a certain time interval and increment.
Claims
1-25. (canceled)
26. A method for dynamic variable humidity control of a hydrogen fuel cell system, wherein the flow rate of the working gas flow is changed repeatedly according to a certain time interval and increment.
27. The method for dynamic variable humidity control of the hydrogen fuel cell system according to claim 26, wherein the increment is 5% to 30% of the starting flow rate and the time interval is 1 to 30 minutes.
28. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] FIG. 1A to FIG. 1E are structural diagrams of the first embodiment of a hydrogen fuel cell power generation system of the present invention;
[0061] FIG. 2A to FIG. 2D are structural diagrams of the second embodiment of a hydrogen fuel cell power generation system of the present invention;
[0062] FIG. 3A to FIG. 3B are structural diagrams of the third embodiment of a hydrogen fuel cell power generation system of the present invention;
[0063] FIG. 4A to FIG. 4B are structural diagrams of the fourth embodiment of a hydrogen fuel cell system power generation of the present invention;
[0064] FIG. 5A to FIG. 5B are structural diagrams of the fifth embodiment of a hydrogen fuel cell system power generation of the present invention;
[0065] FIG. 6A is a sectional diagram of a housing in a hydrogen fuel cell power generation system of the present invention;
[0066] FIG. 6B to FIG. 6C are structural diagrams of a housing in a hydrogen fuel cell power generation system of the present invention;
[0067] FIG. 7 is a schematic diagram illustrating the sectional structures of two individual cells connected in series in a cell pack in a hydrogen fuel cell power generation system of the present invention;
[0068] FIG. 8A to FIG. 8B are schematic diagrams illustrating a front structure and a back structure of an anode guide plate of a unit cell in the first embodiment of a hydrogen fuel cell of the present invention;
[0069] FIG. 9A to FIG. 9B are schematic diagrams illustrating a front structure and a back structure of a cathode guide plate of a unit cell in the first embodiment of a hydrogen fuel cell of the present invention;
[0070] FIG. 10A to FIG. 10B are schematic diagrams illustrating a front structure and a back structure of a cathode guide plate of a unit cell in the second embodiment of a hydrogen fuel cell of the present invention;
[0071] FIG. 11A to FIG. 11B are schematic diagrams illustrating a front structure and a back structure of an anode guide plate of a unit cell in the second embodiment of a hydrogen fuel cell of the present invention;
[0072] FIG. 12A to FIG. 12B are schematic diagrams illustrating a front structure and a back structure of a cathode guide plate of a unit cell in the third embodiment of a hydrogen fuel cell of the present invention;
[0073] FIG. 13 is a schematic diagram illustrating a back structure of a cathode guide plate of a unit cell in the fourth embodiment of a hydrogen fuel cell of the present invention;
[0074] FIG. 14A to FIG. 14B are schematic diagrams illustrating a front structure and a back structure of a cathode guide plate of a unit cell in the fifth embodiment of a hydrogen fuel cell of the present invention;
[0075] FIG. 15 is a schematic diagram illustrating a back structure of a cathode guide plate of a unit cell in the sixth embodiment of a hydrogen fuel cell of the present invention;
[0076] FIG. 16 is a schematic diagram illustrating principles of a membrane electrode of the present invention;
[0077] FIG. 17 is a diagram illustrating humidity relations of each layer of an existing membrane electrode when static constant humidity control is applied;
[0078] FIG. 18 is a diagram illustrating humidity relations of each layer of a membrane electrode when the dynamic humidity control method of the present invention is applied; and
[0079] FIG. 19 is a structural diagram of a filtering device in the hydrogen fuel cell system of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0080] The present invention provides a gas-cooled hydrogen fuel cell which works at normal pressure, applies a hard housing encapsulating structure, an integrated outside plate gas distribution structure, an outside plate gas distribution non-penetrating cathode guide plate, a two-side double-air intake inverse process and a middle single-hole gas exhaust-type anode plate. A dynamic humidity control method is applied, i.e. the working voltage of a working fan is controlled to control the flow rate of the working gas flow.
[0081] The present invention applies air-cooling heat dissipation to replace conventional water-cooling heat dissipation, thus eliminating a water management system and various components thereof, reducing system complexity, volume and weight, reduces costs and improves system reliability. Since the water-cooling system is eliminated, a great deal of maintenance workload is reduced. The present invention can be applied without maintenance, and stored and started rapidly in a sub-zero environment in winter.
[0082] The present invention optimizes distribution of heat dissipation air, distribution of working gas flows outside the plate to individual cells in a fuel cell stack assembly and installation of a heat dissipation fan and a working fan, thus realizing heat dissipation, optimized flow passages and distribution of the working gas flows and ensuring relatively high performance of the fuel cell in optimized working conditions.
[0083] The present invention will be described in details through specific embodiments below.
[0084] Integrated Outside Plate Gas Distribution Device
[0085] The present invention combines distribution of heat dissipation air, distribution of the working gas flow outside a plate to a unit cell in a fuel cell stack assembly and installation of a heat dissipation fan and a working fan are combined by an integrated gas distribution device to form a gas distribution device with comprehensive functions and having the following structures:
Embodiment 1
[0086] Single-side gas distribution, i.e. both a heat dissipation gas distribution device and an outside plate gas distribution device for working gas flow are located on the top plate of a housing.
[0087] FIG. 1A to FIG. 1E are structural diagrams of the first embodiment of a hydrogen fuel cell of the present invention. In the present embodiment, the hydrogen fuel cell applies a single-side gas distribution method to distribute heat dissipation air and working gas flow.
[0088] FIG. 1C is a top view of the present embodiment. FIG. 1A and FIG. 1B are respectively front and back views of FIG. 1C sectioned from AA. FIG. 1D is a B-direction view of FIG. 1B. FIG. 1E is a sectional drawing of partial enlargement of FIG. 1B. The hydrogen fuel cell in the present embodiment includes a fuel cell stack assembly and an outside plate gas distribution device, wherein the fuel cell stack assembly is encapsulated with a hard housing. The structure of the fuel cell stack assembly and the hard housing will be described specifically in embodiments hereinafter.
[0089] The outside plate gas distribution device is fixed on the hard housing and the outside plate gas distribution device includes an outside plate gas distribution device for working gas flow and a heat dissipation gas distribution device.
[0090] The outside plate gas distribution device for working gas flow includes a gas distribution manifold 114, a gas distribution groove 113 and a gas flow outlet 115; the gas distribution manifold 114 is located outside the housing and fixed on the top plate of the housing; the gas distribution manifold 114 is interconnected with the gas distribution groove 113; the gas distribution groove 113 extends into the inner cavity of the housing; a gas flow outlet 115 is formed at the bottom of the gas distribution groove 113; the gas flow outlet 115 is interconnected with the air inlet gas distribution nozzle of a cathode guide plate 118 of each unit cell in the hydrogen fuel cell pack; the air inlet gas distribution nozzle is interconnected with an air inlet channel 110. One end of the gas distribution manifold 114 is an open end; the open end is provided with the working fan mount 112 for connected with a working fan. The gas distribution manifold 114 is lowered gradually towards the other end from the open end. The working fan mount 112 and the heat dissipation fan mount 111 are set on two opposite ends of the top plate, respectively; in addition, the gas distribution manifold 114 is lowered gradually from one end where the fan mount 112 locates towards the other end.
[0091] The heat dissipation gas distribution device system includes a heat dissipation channel 1111 set outside the housing and interconnected with the inner cavity of the housing, and a heat dissipation port (not shown in the figures) set on the housing. One end of the heat dissipation channel 1111 is an open end; the open end is provided with a heat dissipation fan mount 111; the heat dissipation channel 1111 is lowered gradually from the open end towards the other end and fixed and covered on the top plate of the housing; in the present embodiment, the working fan mount 112 and the heat dissipation fan mount 111 are located on the open ends of their respective pipes; of course, they may be also located on any positions of the pipes, and the specific positions are determined according to mounting conditions etc.
[0092] The heat dissipation fan blows air into the inner cavity of the housing or pumps air out of the inner cavity of the housing through the heat dissipation channel 1111 to cool the hydrogen fuel cell pack; heat dissipation air obtained after heat dissipation of the hydrogen fuel cell pack is exhausted or enters via the heat dissipation outlet on the housing.
[0093] In addition, the heat dissipation channel 1111 is provided with a gas flow diversion damping groove 117; heat dissipation gas flow generates a downward deflection speed in the damping groove so that the heat dissipation gas flow flows to the heat dissipation channel of the cell pack more uniformly.
Embodiment 2
[0094] Double-side gas distribution, i.e. the outside plate gas distribution device for working gas flow is set on the top plate of the housing and the heat dissipation channel of the heat dissipation gas distribution device is set on the bottom plate of the housing.
[0095] FIG. 2A to FIG. 2D are structural diagrams of the second embodiment of a hydrogen fuel cell power generation system of the present invention. What is different from the first embodiment is that a heat dissipation fan with its mount and the outside plate gas distribution device for working gas flow are set on the upper plate and the lower plate opposite to each other, i.e. the top plate and the bottom plate of the housing of the hydrogen fuel cell, respectively.
[0096] As shown in FIG. 2A to FIG. 2D, in the present embodiment, the top plate 123 is provided with a gas distribution manifold 121. The gas distribution manifold 121 is connected with a working fan (not shown in the figures) through a working fan mount 122; the gas distribution manifold 121 is interconnected with a gas distribution groove 128. The gas distribution groove 128 extends into the inner cavity of the housing. A gas flow outlet 129 is formed at the bottom of the gas distribution groove 128. The gas flow outlet is interconnected with the air inlet gas distribution nozzle (not shown in the figures) of each unit cell in the cell pack. The bottom plate 124 is provided with a heat dissipation air collection chamber 127. A plurality of heat dissipation ports 130 are provided on the top plate 123 of the housing. The heat dissipation air collection chamber 127 is interconnected with the inner cavity of the housing and interconnected with the heat dissipation fan (not shown in the figures) through the heat dissipation fan mount 125. The heat dissipation fan may pumps air out of the heat dissipation air collection chamber 127 to perform heat dissipation by applying an axial flow fan or a centrifugal fan so as to dissipate heat in the heat dissipation channel (not shown in the figures) of the hydrogen fuel cell pack in the housing to cool the cell pack.
[0097] When the heat dissipation fan pumps air, air outside the housing enters the housing from the heat dissipation ports 130 on the top plate 123, passes through the heat dissipation channel of the cell pack and then hot air is exhausted by the heat dissipation fan from the heat dissipation air collection chamber 127. Heat dissipation air may be also blew into the hydrogen fuel cell pack from the bottom plate 124 by the heat dissipation fan through the heat dissipation air collection chamber 127, and exhausted from the heat dissipation ports 130 of the top plate 123 via the heat dissipation channel (not shown in the figures) of the hydrogen fuel cell pack so as to realize heat dissipation effect.
[0098] Composite Structure
[0099] In the present invention, when there is a plurality of fuel cell stack assemblies encapsulated by the hard housing, the fuel cell stack assemblies may be combined into an integrated composite structure. When single-side gas distribution is applied, the length of the cell pack and the length of the hard housing may be extended randomly according to the required power and voltage. When double-side gas distribution is applied, a cell pack and a heat dissipation fan form a unit module. Fuel cell stacks which are twice as many as those on one unit module are installed by a hard housing which is twice as long as that of one unit module on double modules. The outside plate gas distribution device for working gas flow of the double modules above is twice as long as that on one unit module while a heat dissipation gas distribution device below is mounted with two heat dissipation fans. Other multi-module structures are arranged in the same manner by taking the following embodiments for example:
Embodiment 3
[0100] FIG. 3A to FIG. 3B are structural diagrams of the third embodiment of a hydrogen fuel cell of the present invention. As shown in FIG. 3, two unit modules are included. Cell packs in two unit modules are connected in series, and power source interfaces are introduced from the two ends of a housing. Two heat dissipation air collection chambers are connected with two heat dissipation fans via two mounts, respectively. The working principles of the third embodiment are the same as those in the second embodiment, which will not be repeated here.
Embodiment 4
[0101] FIG. 4A to FIG. 4B are structural diagrams of the fourth embodiment of a hydrogen fuel cell of the present invention. As shown in FIG. 4A to FIG. 4B, the present embodiment includes three unit modules.
Embodiment 5
[0102] FIG. 5A to FIG. 5B are structural diagrams of the fifth embodiment of a hydrogen fuel cell power generation system of the present invention. In the third embodiment and the fourth embodiment, it only needs to lengthen the gas distribution device when two unit modules are connected in series. While there are six unit modules in the fifth embodiment as shown in FIG. 5A to FIG. 5B, wherein two rows of unit modules are set in parallel in the housing. Cell packs in each unit module are connected in series and power supply plates on the front and back ends of the cell packs are connected with two power source interfaces with opposite polarities on a gland of the housing via a conducting medium, respectively.
[0103] In the present embodiment, besides the gas distribution manifold 151, the working fan mount 152, the gas distribution groove and the gas flow outlet, the outside plate gas distribution device for working gas flow further includes a gas flow distribution pipe (not shown in the figures), i.e. inputted gas flow is divided by an outside plate gas distribution manifold into two groups to distribute working gas flows to individual cells in the cell packs in the two rows of unit modules. The gas flow distribution pipe includes a gas flow inlet and a plurality of gas flow distribution ports. The number of the gas flow distribution ports is matched with the number of rows of the fuel cell stack assemblies. As shown in the figures. There are two gas flow distribution ports if there are two rows of fuel cell stack assemblies. There are N gas flow distribution ports if there are N rows of fuel cell stack assemblies.
[0104] Hard housing: the cell encapsulating structure in the present invention is changed from a traditional end-plate pull rod type into a hard housing type.
[0105] In the embodiments above, the specific structure of the housing of the hydrogen fuel cell may apply the structures as shown in FIG. 6A to FIG. 6C. In the embodiment above, the housing structures as shown in FIG. 6A and FIG. 6C are used by toppled. After toppling, a removed plate facing the paper surface is the top plate or bottom plate, and the opposite face is the bottom plate or top plate. Combining the embodiments above, the housing includes a gland 60, two concave-shaped plates 61, a top plate (a plate provided with a gas distribution manifold 692), a bottom plate (a plate opposite to the top plate), a side plate 62 and a flange plate 63; the two concave-shaped plates 61 are set oppositely, one end of a concave-shaped plate is fixedly connected with the side plate 62 and the other end is fixed with the gland 60 through the flange plate 63; power source interfaces of two kinds of polarities are set on the gland and the side plate, respectively; a fuel gas inlet 65 and a fuel gas outlet 66 are set on the gland 60 and the side plate 62, respectively.
[0106] The two sides of the upper edge of the gland 60 are provided with an arc-shaped locking face 601 concave downwards; the portion on the flange plate 63 opposite to the arc-shaped locking face 601 is provided with an arc-shaped locking face 631 concave upwards; when the gland 60 is pressed into the flange plate 63 by an external pressure, a space is enclosed by the arc-shaped locking face 601 concave downwards and the arc-shaped locking face 631 concave upwards, and an encapsulating pin 67 or a bolt is provided in the space.
[0107] Since the flange plate 63 and the gland 60 are structured more precisely, relatively complicated and relatively high machining requirements, a simple encapsulating method may be applied, i.e. the gland 60 is fixed on the flange plate 63 directly by the bolt.
[0108] A pressure compensator 68 is provided between the gland 60 and a power supply plate in the inner cavity of the housing, and pressure compensator 68 is composed of metal plates 681 and elastic bodies 682 laminated in a staggered manner.
[0109] If an insulating plate is further provided between the gland 60 and the power supply plate, the pressure compensator may be also provided between the insulating plate and the gland 60.
[0110] A working fan 691 distributes gas to a stack in the housing via the gas distribution manifold 692.
[0111] Unit Cell Structure
[0112] FIG. 7 is a schematic diagram illustrating the sectional structures of two individual cells connected in series in a cell pack in a hydrogen fuel cell of the present invention. As shown in FIG. 7, the hydrogen fuel cell pack is composed of a plurality of individual cells connected in series. The unit cell includes an anode guide plate 21, a membrane electrode and a cathode guide plate 22; the membrane electrode includes two catalyst layers 25, two conductive diffusion layers (carbon paper) 26 and a proton membrane 27. The front of the anode guide plate 21 and the front of the cathode guide plate 22 are adjacent to two side surfaces of the membrane electrode, respectively; the back of the anode guide plate 21 is adjacent to the cathode guide plate 22 (not shown in the figure) of another unit cell, and is adjacent to the cathode guide plate 22 of another unit cell on the back of the anode guide plate 21; both the back of the anode guide plate and the back of the cathode guide plate are provided with a heat dissipation groove, and the heat dissipation grooves are combined to form a heat dissipation channel 23; the heat dissipation channel 23 is configured to dissipate heat for the individual cells; the heat dissipation channel 23 is an internal heat dissipation channel in a fuel cell stack assembly. The heat dissipation channel 23 is interconnected with the heat dissipation channel 1111 located outside the housing in FIG. 1B to form a complete heat dissipation channel. When working, an air guide groove 29 guides air into the cathode guide plate, hydrogen is infused into the anode guide plate 21 via a hydrogen guide groove 20 and electric energy is generated through the membrane electrode. The working principles of the membrane electrode will be explained specifically hereinafter and will not be repeated here.
[0113] About the structures of the guide plates:
Embodiment 1
[0114] FIG. 8A to FIG. 8B are schematic diagrams illustrating a front structure and a back structure of an anode guide plate of a unit cell in the first embodiment of a hydrogen fuel cell of the present invention. As shown in FIG. 8A, the anode guide plate is provided with a main hydrogen gas inlet 311, a main hydrogen gas outlet 315, and a hydrogen guide groove 313 of the anode guide plate; the two ends of the hydrogen guide groove are provided with a first gas guide hole 312 and a second gas guide hole 314; the hydrogen guide groove 313 is arranged longitudinally; and a sealing ring 316 is provided around the anode guide plate.
[0115] As shown in FIG. 8B, the back of the anode guide plate is provided with a first air inlet gas distribution nozzle 317 and a first air inlet groove 320 interconnected with the first air inlet gas distribution nozzle 317; the back of the anode guide plate is further provided with a first heat dissipation groove 319 and a first air exhaust groove 318.
[0116] As shown in FIG. 8A in combination with FIG. 8B, the first gas guide hole 312 on the back of the anode guide plate is interconnected with the main hydrogen gas inlet 311; the second gas guide hole 314 on back of the anode guide plate is interconnected with the main hydrogen gas outlet 315; hydrogen is connected to the main hydrogen gas inlet 311 from an external pipe etc., enters the back of the guide plate, enters the hydrogen guide groove 313 on the front of the guide plate from the back of the guide plate via the first gas guide hole 312, enters the back of the guide plate from the second gas guide hole 314, and is then exhausted by a pipeline from the main hydrogen gas outlet 315 on the back of the guide plate.
[0117] FIG. 9A to FIG. 9B are schematic diagrams illustrating a front structure and a back structure of a cathode guide plate of a unit cell in the first embodiment of a hydrogen fuel cell of the present invention. As shown in FIG. 9A, the cathode guide plate is provided with a main hydrogen gas inlet 321 and a main hydrogen gas outlet 324. The front of the cathode guide plate is provided with an air inlet 325, an air outlet 322, and an air guide groove 323. The air guide groove 323 is arranged transversely.
[0118] As shown in FIG. 9B, the back of the cathode guide plate is provided with a second air exhaust groove 328; the second air exhaust groove 328 is provided with the air outlet 322. Additionally, sealing rings 329 are provided at the main hydrogen gas inlet and the main hydrogen gas outlet. The back of the cathode guide plate is provided with a second air inlet gas distribution nozzle 326 and a second air inlet groove 327 interconnected with the second air inlet gas distribution nozzle 326; the air inlet 325 is set in the second air inlet groove 327.
[0119] When the back of the cathode guide plate is matched with the back of the anode guide plate, the first air inlet groove 320 on the back of the anode guide plate is combined with the second air inlet groove 327 on the back of the cathode guide plate to form a complete air inlet channel. The first air inlet gas distribution nozzle 317 is combined with the second air inlet gas distribution nozzle 326 to form a complete air inlet gas distribution nozzle used for connecting with the gas flow outlet of the outside plate gas distribution device for working gas flow.
[0120] The second air inlet groove 327 of the cathode guide plate is provided with a plurality of air inlets 325 interconnected with the front of the cathode guide plate. The air outlet 322 on the front of the cathode guide plate is interconnected with the first air exhaust groove 328 on the back of the cathode guide plate. The main hydrogen gas inlet 321 of the cathode guide plate and the main hydrogen gas inlet 311 of the anode guide plate on each unit cell in the cell pack are interconnected with each other. The main hydrogen gas outlet 324 of the cathode guide plate and the main hydrogen gas outlet 314 of the anode guide plate on each unit cell are interconnected with each other and connected with a hydrogen gas source outside the system via a hole on the housing.
[0121] The back of the cathode guide plate is further provided with a second heat dissipation groove 330. Turbulators are provided in the second heat dissipation groove 330 and the first heat dissipation groove 319 on the back of the anode guide plate, and two heat dissipation grooves can be combined into a heat dissipation channel.
[0122] As described above, the second air exhaust groove 328 on the back of the anode guide plate and the first air exhaust groove 318 on the front of the anode guide plate are combined into an exhaust gas channel. There may be one or more exhaust gas channels. Correspondingly, one or more outlets are provided on the housing.
[0123] In the structure above, hydrogen flows from the two ends of a guide plate towards the middle to form a guide plate with double gas inlets at two sides and gas outlet in the middle while air flows from the middle to the two ends to form a gas distribution method of an inverse process with gas inlet in the middle and double gas outlets at two sides.
[0124] Additionally, the back of the anode guide plate and the back of the cathode guide plate are provided with a plurality of reinforcing ribs used for improving the guide plate strength. As a preferred embodiment, the structures and shapes of the reinforcing ribs in the heat dissipation channel are designed so that the reinforcing ribs form a turbulator in the heat dissipation channel to enhance the heat dissipation effect.
Embodiment 2
[0125] FIG. 10A to FIG. 10B are schematic diagrams illustrating back structures of an anode guide plate and a cathode guide plate of a unit cell in the second embodiment of a hydrogen fuel cell of the present invention. FIG. 11A to FIG. 11B are schematic diagrams illustrating front structures of an anode guide plate and a cathode guide plate of a unit cell in the second embodiment of a hydrogen fuel cell of the present invention. As shown in FIG. 10A to FIG. 11B, what is different from the first embodiments is that the anode guide plate is provided with one main hydrogen gas inlet 341 set at one side of the anode guide plate, and the anode guide plate is also provided with one main hydrogen gas outlet 342 set at the other side of the anode guide plate. The working principles of the second embodiment are the same as those of the first embodiment and will not be repeated here. A polar plate with such a structure is mainly applied to a compound fuel cell stack.
Embodiment 3
[0126] FIG. 12A to FIG. 12B are schematic diagrams illustrating a front structure and a back structure of a cathode guide plate of a unit cell in the third embodiment of a hydrogen fuel cell of the present invention. As shown in FIG. 12A to FIG. 12B, the present embodiment applies a kind of outside plate gas distribution non-penetrating cathode guide plate. The polar plate is a structure with gas intake at one side and gas collection and exhaust at the other side. A gas distribution pipe 351 is mounted and sealed out of the polar plate 35 and functions as a gas distribution nozzle interconnected with the gas flow inlet of the gas distribution device. Air is inputted from the gas distribution pipe 351 into an air inlet groove 352 in the back of the polar plate 35, and transmitted from an air inlet 353 to an air guide groove 354 sealed on the front of the polar plate 35, and flows from one end of the air inlet 353 to one end of an air outlet 355. Hereby, after participating in oxidation and power generation, the air enters from the air outlet 355 at the other end into a second gas exhaust groove 356, and is exhausted together with the steam generated by the reaction from a gas outlet 358. The working principles of the third embodiment are the same as those of the first embodiment and will not be repeated here.
Embodiment 4
[0127] As shown in FIG. 13 which is a schematic diagram illustrating a back structure of a cathode guide plate in the fourth embodiment, and the front structure of the cathode guide plate has the same structure as that of the third embodiment and will not be repeated here. In the present embodiment, each air outlet is interconnected with a gas exhaust groove on the back of the cathode guide plate of the unit cell. In other words, compared with the third embodiment in which one gas exhaust groove is provided, a plurality of gas exhaust grooves are provided in the fourth embodiment.
Embodiment 5
[0128] FIG. 14A to FIG. 14B are schematic diagrams illustrating a front structure and a back structure of a cathode guide plate of a unit cell in the fifth embodiment of a hydrogen fuel cell of the present invention. As shown in FIG. 14A to FIG. 14B, the present embodiment applies a mechanism with gas intake in the middle and gas collection and exhaust at two sides. In the present embodiment, an outside plate gas distribution pipe 361 is interconnected with an air inlet groove 362. An air inlet 363 is set in the air inlet groove 362 while an air outlet 365, a gas exhaust groove 366 and a gas outlet are set on two sides of a polar plate 36, respectively. On the front of the polar plate, an air guide groove 364 is provided between the air inlet 363 and the air outlet 365. Air enters the outside plate gas distribution pipe 361 from the gas flow outlet of the gas distribution device, flows from the air inlet 363 in the air inlet groove 362 into the air guide groove 364 on the front, flows from one end of the air inlet 363 into one end of the air outlet 365, flows from the air outlet 365 into the gas exhaust groove 366 on the back and is collected and exhausted from the gas exhaust groove 366.
[0129] In the present embodiment, there are two rows of gas exhaust grooves and gas outlets. The working principles of the present embodiment are the same as those of the first embodiment and will not be repeated here.
Embodiment 6
[0130] As shown in FIG. 15 which is a schematic diagram illustrating a back structure of a cathode guide plate in the sixth embodiment, the front structure of the cathode guide plate has the same structure as that of the fifth embodiment and will not be repeated here. In the present embodiment, on the back of the cathode guide plate of the unit cell, each air outlet 365 is interconnected with a gas exhaust groove 366. In other words, compared with the fifth embodiment, a longitudinal gas exhaust groove is provided at two sides of a polar plate respectively in the fifth embodiment while the two sides of the polar plate are provided with a plurality of transverse gas exhaust grooves in the sixth embodiment.
[0131] The present embodiment further provides a method for dynamic variable humidity control of a hydrogen fuel cell power generation system. Please first refer to FIG. 16 which is a schematic diagram illustrating principles of a membrane electrode. As shown in FIG. 16, the membrane electrode 5 is composed of a proton membrane 51, two catalyst layers 52 and two diffusion layers 53. The proton membrane 51, which can conduct hydrogen ions (protons) instead of being electrically conductive, separates a hydrogen gas and an oxygen gas at two sides of the proton membrane to prevent mutual permeation. The catalyst layers 52 are adhered at two sides of the proton membrane 51. The catalyst layer 52 at the hydrogen side is an anode catalyst layer. Hydrogen atoms are electrolyzed into two parts consisting of hydrogen ions and free electrons by the anode. Since the proton membrane 51 can conduct ions, the hydrogen ions (protons) are conducted to an air side of the cathode by the proton membrane 51 while the electrons are transmitted by an external circuit through the diffusion layers (carbon paper) 53 to the cathode to generate electric energy. At the same time, water is generated by oxygen and the hydrogen protons transmitted by the proton membrane 51.
[0132] Secondly, please refer to FIG. 17 which is diagram illustrating humidity relations of each layer when an existing membrane electrode when static constant humidity control is applied. As shown in FIG. 17 and referring to FIG. 16, the higher the humidity of the proton membrane 51 is, the smaller the hydrogen ion conduction resistance of the proton membrane will be. Therefore, the traditional fuel cell constant-humidity temperature control mode has to always work in a relatively high humidity as much as possible (as shown in FIG. 17) in order to reduce internal resistance and improve power generation capacity. Besides catalyzing and conducting ions, the catalyst layers 52 should be further able to make gases diffuse and flow. Diffusing needs relatively high humidity while flowing needs relatively low humidity. Otherwise, gas diffusion will be influenced as soon as a diffusion channel is occupied with water to reduce the power generation capacity. Thus the catalyst layers 52 are required to meet the requirements of two aspects to maintain a balanced medium humidity while the diffusion layers (carbon paper) do not need a high humidity condition to conduct electrons and diffuse gases. Instead, drier diffusion layers are preferred. These three different conditions can be hardly satisfied at the same time in constant humidity control. In order to ensure operation of the membrane electrode 5, the membrane electrode has to run in a relatively high humidity, thus the defects above can be hardly overcome and power can be hardly generated in optimized conditions.
[0133] As shown in FIG. 17, R1 is a relatively optimized humidity of the proton membrane; R2 is a relatively optimized humidity of a catalyst layer; R3 is a relatively optimized humidity of a diffusion layer; and Q is an optimized flow rate of reaction air. When the flow rate of the reaction air is small, the gas flow humidity is high. The gas flow humidity is low when the flow rate of the reaction air is large.
[0134] The method for dynamic variable humidity control of the present invention can realize dynamic variable humidity control. The voltage of a working fan is controlled to change the flow rate of the working gas flow so that the flow rate of the working gas is changed repeatedly according to a certain time interval and increment, as shown by the last curve Q in FIG. 18.
[0135] FIG. 18 is a diagram illustrating humidity relations of each layer of a membrane electrode when the dynamic variable humidity control method of the present invention is applied. In FIG. 18, R1 is a relatively optimized humidity of the proton membrane; R2 is a relatively optimized humidity of a catalyst layer; R3 is a relatively optimized humidity of a diffusion layer; and Q is an optimized flow rate of reaction air. As shown in FIG. 18 and referring to FIG. 16, by using the time difference formed by the humidity gradient and humidity change rate of water transferred between the layers, the dynamic variable humidity control changes parameters of a fan controller first so that the revolving speed of the fan is increased to increase the flow rate of the working gas flow Q to Qa, change and reduce the humidity of the diffusion layers (carbon paper) 53 from R3-a to R3-b so as to change the humidity of the catalyst layers 52 and reduce the humidity from R2-a to R2-b. When the humidity change of the catalyst layers 52 begins to influence the humidity change of the proton membrane 51 and reduce the humidity from R1-a to R1-b, the revolving speed of the fan is controlled and the flow rate of the working gas flow is changed so that the flow rate is reduced from Qb to Qc, the humidity of the diffusion layers (carbon paper) 53 stops decreasing and is increased to R3-c gradually, and the humidity of the catalyst layers 52 stops decreasing and is also increased to R2-c gradually. Similarly, the increase of the humidity to R2-c also stops the humidity from decreasing to R1-b and increases the humidity to R1-c so that the proton membrane 51 works in a relatively high humidity and the catalyst layers 52 works under a medium humidity during a dynamic adjustment process while the working humidity of the diffusion layers (carbon paper) 53 is always circulated and repeated in a relatively low humidity.
[0136] In this way, under such dynamic variable humidity control, the flow rate of the working gas is changed repeatedly according to a certain time interval and increment, thus increasing the humidity gradient and the humidity difference ΔR1 and ΔR2 of the diffusion layers (carbon paper) 53 and the catalyst layers 52 and optimizing the working conditions of the membrane electrode 5 while discharging the reaction water. Wherein such control can be realized by a hydrogen circulating system at the hydrogen side and an air working fan at the same time, or may be controlled separately by the air side. Additionally, the gas flow variables (change amplitude of reaction air optimized flow rate Q) of the change period of the dynamic variable humidity control parameters may change between 5% and 30% of the total quantity Q in a time period from Qa to Qb, i.e. the time difference of the change intervals is 1 to 30 minutes. However, since different membrane electrode materials and membrane electrodes of different structure are very different, the specific values of two kinds of parameters above need to be determined and optimized in the range determined above through experiments for a membrane electrode of a determined material and structure.
[0137] Wherein the total quantity Q is the minimum flow rate value of a membrane electrode optimized theoretical value.
[0138] In addition, the present invention further discloses a hydrogen fuel cell system. The system includes the hydrogen fuel cell of the embodiments above, the working fan and the heat dissipation fan. The working fan and the heat dissipation fan are installed on the mounts in the hydrogen fuel cell.
[0139] To solve the problem that when working in an urban environment, harmful gases (SO.sub.2, HS, HCX, HNX) may enter the cathode of the fuel cell with working gases to cause significant problems including catalyst poisoning and reduction of cell performance, the present invention adds a filtering device to the hydrogen fuel cell system. As shown in FIG. 19, the filtering device includes a gas inlet 18, an alkaline activated carbon absorption filter 81 and a gas outlet 82. The gas inlet 80 is located below the alkaline activated carbon absorption filter 81. The gas inlet 82 is located above the alkaline activated carbon absorption filter 81. The gas inlet 82 is interconnected with the gas inlet of the working fan. The device is similar to an intake filter of an internal combustion engine vehicle. A dust filtering layer between an upper lid 83 and a lower lid 84 of the intake filter is replaced by an alkaline activated carbon absorption filter filled with specially developed alkaline activated carbon absorption grains for absorbing harmful acid gases including SO.sub.2, H.sub.2S etc. The filtering layer can absorb harmful gases when the working gas flow enters the filtering device, passes through the filter before the working gas flow enters and works in the cell, thus ensuring normal operation of the fuel cell in a polluted environment.
[0140] Through the absorption filter 81, a harmful gas concentration of 1 to 5 PPM can be purified to below 0.005 PPM.
[0141] Finally, it should be noted that, the foregoing embodiments are merely used for illustrating, but not for limiting the present invention. Though the present invention has been described in details with reference to the preferred embodiments, those of ordinary skill in the art should understand that, modifications or equivalent replacements made to the present invention without departing from the principle and range of the present invention should be included in the scope of the claims of the present invention.
