Fuel cell stack with metal flow field plate

Abstract

A fuel cell stack (100) is provided, comprising a metal flow field plate (305) between a pair of fuel cell assemblies (103a, 103b). The fuel cell stack (100) includes a pair of end plates (101, 102) and a cover plate (107). The pair of fuel cell assemblies (103a, 103b) includes a first membrane electrode assembly (303) and a second membrane electrode assembly (307) having an anode surface (303a, 307a) and a cathode surface (303b, 307b). The metal flow field plate (305) includes a first surface (305a) having two or more serpentine first flow channels (401) for air and a second surface (305b) having one or more serpentine second flow channels (501) for hydrogen. The metal flow field plate (305) prevents cross-contamination of air and hydrogen and avoids seam welding between the two monopole plates.

Description

Technical Field

[0001] The present invention relates generally to a fuel cell stack, and more particularly to a metal flow field plate in a fuel cell stack. Background Technology

[0002] A fuel cell is an electrochemical device that generates electricity through the reaction between fuels (i.e., hydrogen and oxygen). In a fuel cell, pure oxygen or air containing a large amount of oxygen reacts with pure hydrogen or fuel containing a large amount of hydrogen. Hydrogen can be produced by reforming hydrocarbon fuels (such as methanol). The fuel is guided through a flow field plate to the anode on one side of the proton exchange membrane in the fuel cell, and the oxygen is guided through another flow field plate to the cathode on the other side of the proton exchange membrane. Electrochemical reactions occur at the anode and cathode to generate electricity, water, and heat. The design of the flow field plates is crucial to the performance of the fuel cell. Summary of the Invention

[0003] This summary is provided to present, in a simplified form, selected embodiments of the inventive concept further disclosed in the detailed description of the invention. This summary is not intended to define the scope of the claimed subject matter.

[0004] This document discloses a metal flow field plate in a pair of fuel cell assemblies, comprising a first surface and a second surface behind the first surface. The first surface includes two or more serpentine first flow channels, and the second surface includes one or more serpentine second flow channels, wherein the second flow channels are formed by stamping the first flow channels on the first surface.

[0005] Each of the first flow channels receives air from two or more first inlet pipes located on a first surface, wherein the two or more first inlet pipes are operatively connected to the discharge port of the aeration device and discharge air from two or more first outlet pipes located on the first surface. Each of the second flow channels receives hydrogen from one or more second inlet pipes located on a second surface and discharges hydrogen from one or more second outlet pipes located on a second surface. The metal flow field plate also includes grooves formed along the length of the first and second flow channels on the edges of each of the first and second surfaces for accommodating one or more elastic members.

[0006] A first inlet pipe and a first outlet pipe are located at the first edge of the metal flow field plate. A second inlet pipe engages with one or more inlet manifolds positioned on a pair of end plates, and a second outlet pipe engages with one or more outlet manifolds positioned on a pair of end plates. Air and hydrogen reactively engage with the membrane electrode assembly (MEA) in each of the pair of fuel cell assemblies to supply current to the circuit. Air from the first flow channel diffuses toward the cathode surface of the MEA in the fuel cell assembly, and hydrogen from the second flow channel diffuses toward the anode surface of the MEA in the fuel cell assembly. The aeration device is a blower or a centrifugal pump.

[0007] In an embodiment, a fuel cell stack is disclosed herein, comprising a pair of end plates, a plurality of fuel cell assemblies positioned between the pair of end plates, and a cover plate positioned to contact a first edge of the pair of end plates. Each end plate includes one or more inlet manifolds and one or more outlet manifolds for hydrogen. One pair of fuel cell assemblies includes a pair of membrane electrode assemblies, a metal flow field plate positioned between the pair of membrane electrode assemblies, and one or more elastic members. Each of the elastic members is positioned in a groove on an edge of a first surface and a second surface of the metal flow field plate for hermetically sealing reactants. The cover plate accommodates aeration equipment. The fuel cell stack also includes a pair of monopole current collectors for collecting current generated in the fuel assemblies, and each monopole current collector is positioned between an end plate and one of the membrane electrode assemblies.

[0008] Two or more serpentine first flow channels for air on the first surface of the metal flow field plate create one or more serpentine second flow channels for hydrogen on the back surface of the metal flow field plate. Creating such a continuous vertical serpentine flow path for both hydrogen and air, starting from the inlet and ending at the outlet, solves the problem of water blockage in cryogenic proton exchange membrane (PEM) fuel cells, even without manifolds. The inlet and outlet manifolds are configured solely for hydrogen, while air is delivered through the first inlet line. This configuration eliminates gas crossover at the inlet because the first and second inlet lines are far apart from each other. Attached Figure Description

[0009] The foregoing summary of the invention and the following detailed description can be better understood when read in conjunction with the accompanying drawings. Exemplary constructions of the invention are illustrated in the drawings to illustrate the invention. However, the invention is not limited to the specific structures and methods disclosed herein. The description of structures indicated by reference numerals in the drawings applies to the description of structures indicated by the same reference numerals in any subsequent drawings herein.

[0010] Figures 1A to 1B An exemplary perspective view of a fuel cell stack is shown;

[0011] Figure 2An example is shown Figure 1A An exploded view of a fuel cell stack is shown in the example below;

[0012] Figure 3 An exploded view of a pair of fuel cell assemblies in a fuel cell stack is shown as an example;

[0013] Figure 4 An exemplary front view of a metal flow field plate in a pair of fuel cell assemblies is shown;

[0014] Figures 5A to 5B An enlarged front view of the first and second surfaces of a metal flow field plate is shown as an example;

[0015] Figure 6 An exemplary front view of an elastic member coupled to a metal flow field plate or a single-pole current collector is shown;

[0016] Figure 7 An exemplary front view of the membrane electrode assembly of a fuel cell assembly is shown;

[0017] Figure 8 An exemplary front view of a unipolar current collector plate of a fuel cell assembly having two or more flow channels on its front surface is shown;

[0018] Figure 9 An exemplary front view of a unipolar current collector of a fuel cell assembly having one or more flow channels on its front surface is shown;

[0019] Figure 10 An exemplary front view of the endplate of a fuel cell stack is shown;

[0020] Figures 11A to 11B An exemplary perspective view of the cover plate of a fuel cell stack is shown; and

[0021] Figures 12A to 12C An exemplary illustration shows a housing and a device for positioning the aeration equipment. Figures 11A to 11B The mounting device on the cover plate is shown as an example. Detailed Implementation

[0022] Various designs are available for the flow field plate that directs fuel and air to the proton exchange membrane. For cryogenic proton exchange membrane (PEM) fuel cells, one such design involves two individual serpentine channels extending parallel to each other, such that one channel covers half the flow area of ​​the flow field plate, while the other covers the other half. These two individual serpentine channels are connected to the inlet manifold of the PEM fuel cell via headers. The same design is used for hydrogen and air on both sides of the flow field plate. The bipolar plate is manufactured such that the flow field of hydrogen on one side (anode side) is perpendicular to the flow field of air / oxygen on the other side (cathode side).

[0023] However, when assembling a fuel cell stack with such bipolar plates, the flow field on one side is vertical, while the flow field on the other side is horizontal. When moist gases (hydrogen and oxygen) pass through a single serpentine channel, water blockage is observed in the lower portion of the horizontal flow field due to gravity, while the upper portion dries out, thus adversely affecting fuel cell performance. These problems arise from the manifold and the presence of two single, parallel serpentine channels. Therefore, it is necessary to avoid water blockage in the bipolar plates to prevent degradation of fuel cell performance.

[0024] Furthermore, because the electrochemical reactions generate heat in the fuel cell, this heat must be continuously removed with the help of a coolant (such as air or liquid) to maintain the fuel cell's operating temperature. Low-temperature PEM fuel cells operate at temperatures ranging from approximately -30°C to 80°C, while high-temperature PEM fuel cells operate at temperatures ranging from approximately 80°C to 160°C. Failure to maintain these operating temperatures can lead to permanent damage to the membrane electrode assembly, necessitating its replacement.

[0025] To maintain the operating temperature of the fuel cell stack, the coolant needs to be continuously recirculated within the stack to maintain that temperature. If air is used as the coolant, it is delivered along with the reactant air flowing through the flow field and cooling the stack. However, this delivery of coolant along with reactant air along the flow field plate leads to acid leaching from the membrane electrode assembly, carbon corrosion of carbon-based materials (such as the gas diffusion layer), catalyst poisoning due to the presence of CO, and other degradations in fuel cell performance. To address this performance degradation, a separate manifold / channel could be provided to use either air or any liquid coolant, in addition to the inlet manifold / channel for reactant air. Such an arrangement might require additional components, increasing the manufacturing and maintenance costs of the PEMFC (Proton Exchange Component Fuel Cell). Therefore, it is necessary to circulate the coolant within the PEMFC without degrading its performance.

[0026] Another existing design for flow field plates involves forming flow fields for hydrogen and air on two separate (monopolar) plates and seaming the monopolar plates to obtain a bipolar plate. However, the inlets and outlets for hydrogen and air on both sides of the flow field plate are almost close to each other, leading to sealing difficulties, especially at the inlets and outlets. Inadequate sealing at the inlets and outlets can lead to internal combustion of the gases.

[0027] Therefore, there has long been a need for fuel cell stacks with one or more bipolar flow field plates that allow for the flow of coolant and reactants without adding extra manufacturing costs and making the fuel cell stack easy to maintain. This topic addresses the aforementioned need for bipolar flow field plates that allow for the flow of coolant and reactants without additional cost.

[0028] Figures 1A to 1B An exemplary perspective view of a fuel cell stack 100 is shown. The fuel cell stack 100 is a stacked arrangement of multiple fuel cell modules 103 that generate higher voltage and power than a single fuel cell module. The fuel cell modules 103 are connected in series to form the fuel cell stack 100. In embodiments, the number of fuel cell modules 103 can be increased to increase the output voltage of the fuel cell stack 100. The fuel cell module is an electrochemical cell that converts the chemical energy of hydrogen and oxygen into current and heat through a pair of oxidation and reduction reactions. In the fuel cell module, chemical reactions occur between the anode and the electrolyte, and between the cathode and the electrolyte. At the anode, hydrogen is oxidized, producing positively charged hydrogen ions and negatively charged electrons. The positively charged hydrogen ions travel through the electrolyte, and the electrons travel through the external circuitry. At the cathode, the positively charged hydrogen ions combine with electrons and oxygen to produce water. Depending on the type of cathode, anode, and electrolyte, the fuel cell module can be a proton exchange membrane fuel cell module, a phosphoric acid fuel cell module, a solid acid fuel cell module, an alkaline fuel cell, etc.

[0029] like Figure 1A As exemplarily illustrated, multiple fuel cell assemblies 103 are stacked between a pair of end plates 101 and 102, and a cover plate 107 is positioned on the end plates 101 and 102. The end plates 101 and 102 have guide holes for fasteners 106, such as nut and bolt assemblies, belt assemblies, spring assemblies, etc., to apply pressure to the fuel cell assemblies 103, thereby maintaining the integrity of the fuel cell stack 100 and preventing gas from escaping from the fuel cell assemblies 103. The torque of tightening the fasteners 106 is kept consistent to avoid gas leakage. The end plates 101 and 102 also include one or more inlet manifolds (such as 104) and one or more outlet manifolds (such as 105). The cover plate 107 is positioned to contact a first edge of the end plates 101 and 102. Figure 1AAs exemplarily illustrated, cover 107 accommodates aeration device 110, such as a blower. Cover 107 includes an air inlet pipe 109 of the fuel cell stack 100 that is removably coupled to the exhaust port of the aeration device 110, an air outlet pipe 108 of the fuel cell stack 100, and a recirculation pipe 111 that connects the outlet pipe 108 to the exhaust port of the aeration device 110 via a heat exchange mechanism for recirculating air into the fuel cell stack 100.

[0030] like Figure 1B As exemplarily shown, the aeration device 110 is housed in the housing 112 and uses Figures 12A to 12C The exemplary mounting device shown is housed between the inlet 109 and the outlet pipe 108 of the fuel cell stack 100. In an embodiment, the inlet manifold 104 and the outlet manifold 105 for hydrogen are positioned on the same end plate, such as... Figure 1A As exemplarily shown in the figure, on 102. In an embodiment, the inlet manifold 104 and the outlet manifold 105 for hydrogen are positioned on different end plates, such as 101 and 102, that is, the inlet manifold 104 is on one end plate, such as 101, while the outlet manifold 105 is on another end plate, such as 102.

[0031] Figure 2 An example is shown Figure 1A An exploded perspective view of a fuel cell stack 100 is shown as an example. As shown, multiple fuel cell assemblies 103 are stacked together between end plates 101 and 102 using fasteners 106 and guides 202. Fasteners 106 and guides 202 are inserted through guide holes 201 in end plates 101 and 102. A cover plate 107 is threadedly attached to end plates 101 and 102 at first edges 101a and 102a, respectively, using fasteners 203 (e.g., screw and nut assemblies). The insertion of guides 202 through guide holes 201 into the structure of the fuel cell stack 100 ensures the rigidity and stable assembly of the fuel cell stack 100. Fasteners 106 ensure sufficient compression of the structure of the fuel cell stack 100.

[0032] The outlet of the aeration device 110 is connected to the inlet pipe 109 of the fuel cell stack 100. The emissions from the aeration device 110 include reactive air for the electrochemical reactions in the fuel cell assembly 103 and coolant air to remove heat generated in the fuel cell stack 100. Remaining reactive air and hot coolant air reach the outlet pipe 108 of the fuel cell stack 100 and are recirculated back to the outlet of the aeration device 110 via a recirculation pipe 111 housing a heat exchange mechanism. The aeration device 110 is, for example, a blower that increases the air velocity and pressure via an impeller to supply air for the electrochemical reactions and cooling of the fuel cell stack 100. The supplied air serves as the oxygen source for the electrochemical reactions in each fuel cell assembly of the fuel cell stack 100. Hydrogen is supplied through the inlet manifold 105, and any unreacted hydrogen and water vapor remaining after the electrochemical reactions are discharged through the outlet manifold 105 in the end plate 102. The hydrogen can be derived from hydrogen-containing substances such as methanol, gasoline, natural gas, and water. Pure hydrogen and oxygen, free of impurities, are pressurized and injected into the fuel cell stack 100.

[0033] Figure 3 An exploded view of a pair of fuel cell assemblies 103a and 103b in a fuel cell stack 100 is shown as an example. The pair of fuel cell assemblies 103a and 103b are compressed between a pair of end plates 101 and 102. The pair of fuel cell assemblies 103a and 103b include a pair of membrane electrode assemblies (i.e., a first membrane electrode assembly 303 and a second membrane electrode assembly 307) and a metal flow field plate 305 positioned between the membrane electrode assemblies 303 and 307 by elastic members 302, 304, 306, and 308 disposed on both sides of the membrane electrode assemblies 303 and 307. Each of the membrane electrode assemblies 303 and 307 is a combination of an electrolyte, an anode, and a cathode. Each of the membrane electrode assemblies 303 and 307 includes a selectively permeable proton exchange membrane, an anode catalyst layer and a cathode catalyst layer on both sides of the proton exchange membrane, and a gas diffusion layer on both sides of the proton exchange membrane. The proton exchange membrane conducts positively charged hydrogen ions and blocks negatively charged electrons. The anode catalyst layers form the anode surfaces 303a and 307a of membrane electrode assemblies 303 and 307, respectively, and the cathode catalyst layers form the cathode surfaces 303b and 307b of membrane electrode assemblies 303 and 307, respectively. On the anode surfaces 303a and 307a of membrane electrode assemblies 303 and 307, a hydrogen oxidation reaction occurs, decomposing hydrogen into positively charged ions and negatively charged electrons. The half-cell oxidation reaction is represented as: H2 → 2H2O + +2e - .

[0034] Positively charged ions pass through membrane electrode assemblies 303 and 307 to reach cathode surfaces 303b and 307b, respectively. Electrons travel along the external load circuit to the cathode surfaces 303b and 307b of membrane electrode assemblies 303 and 307, thereby generating current output from fuel cell components 103a and 103b. At the cathode surfaces 303b and 307b of membrane electrode assemblies 303 and 307, oxygen molecules react with protons that have permeated the proton exchange membrane and electrons that have arrived through the external circuit to form water molecules. The half-cell reduction reaction is represented as: 1 / 2 O₂ + 2H₂O + +2e - →H2O.

[0035] Platinum catalysts can initiate half-cell oxidation and half-cell reduction reactions, respectively, on the anode surfaces 303a and 307a and the cathode surfaces 303b and 307b of membrane electrode assemblies 303 and 307, respectively. A gas diffusion layer is positioned above the anode and cathode catalyst layers of membrane electrode assemblies 303 and 307. The gas diffusion layer facilitates the transport of hydrogen and oxygen into the catalyst layers and also helps remove water generated in fuel cell assemblies 103a and 103b. The gas diffusion layer has pores through which air and hydrogen diffuse to the cathode surfaces 303b and 307b and the anode surfaces 303a and 307a of membrane electrode assemblies 303 and 307, respectively.

[0036] As exemplarily illustrated, a metal flow field plate 305 is positioned between a first membrane electrode assembly 303 and a second membrane electrode assembly 307. That is, each fuel cell assembly 103a or 103b in the fuel cell stack 100 is sandwiched between two metal flow field plates (such as 305) to separate it from adjacent fuel cell assemblies. A first surface 305a of the metal flow field plate 305 faces the cathode surface 303b of the first membrane electrode assembly 303, and a second surface 305b of the metal flow field plate 305 faces the anode surface 307a of the second membrane electrode assembly 307. The metal flow field plate 305 uniformly distributes air on the first surface 305a and hydrogen uniformly on the second surface 305b towards the membrane electrode assemblies 303 and 307. The metal flow field plate 305 has flow fields on both surfaces 305a and 305b to satisfy the diffusion of hydrogen and oxygen, respectively. The flow fields can be of different shapes, such as rectangular, triangular, circular, etc. Flow channels on the two surfaces 305a and 305b constitute a flow field for oxygen and hydrogen. Two or more serpentine first air flow channels are provided on the first surface 305a of the metal flow field plate 305, and one or more serpentine second hydrogen flow channels are provided on the second surface 305b of the metal flow field plate 305. The first flow channels of the metal flow field plate 305 satisfy the electrochemical reactions in the fuel cell assembly 103a, and the second flow channels of the metal flow field plate 305 satisfy the electrochemical reactions in the adjacent fuel cell assembly 103b. The metal flow field plate 305, having a first surface 305a and a second surface 305b, exemplarily... Figure 4 , Figure 5A and Figure 5B As shown in the image.

[0037] Elastic members 304 and 306 (e.g., gaskets) are positioned between the metal flow field plate 305 and each of the membrane electrode assemblies 303 and 307. Figure 6 The exemplary elastic members 304 and 306 provided a seal to prevent excessive leakage of hydrogen or oxygen from the fuel cell stack 100. Fuel cell assemblies 103a and 103b include a pair of monopole current collectors 301 and 309 for collecting the current generated in the fuel cell assemblies 103a and 103b. Each monopole current collector 301 and 309 includes a flow field for oxygen or hydrogen on its front surfaces 301a and 309a facing the membrane electrode assemblies 303 and 307. The front surface 301a of the monopole current collector 301 facing the anode surface 303a of the first membrane electrode assembly 303 is analogous to a second hydrogen flow channel of the metal flow field plate 305, and the front surface 309a of the monopole current collector 309 facing the cathode surface 307b of the second membrane electrode assembly 307 is analogous to a first oxygen flow channel of the metal flow field plate 305. The monopole current collectors 301 and 309 connect the fuel cell assemblies 103a and 103b to an external load.

[0038] Another pair of elastic members 302 and 308 are positioned between the unipolar current collectors 301 and 309 of the fuel cell assemblies 103a and 103b and the membrane electrode assemblies 303 and 307, respectively. The elastic members, or gaskets 302 and 308, provide a mechanical seal between the front surfaces 301a and 309a of the unipolar current collectors 301 and 309 and the anode surface 303a or cathode surface 307b of the membrane electrode assemblies 303 and 307 to prevent leakage of oxygen or hydrogen from the flow fields flowing through the unipolar current collectors 301 and 309, respectively.

[0039] Each of the membrane electrode assemblies 303 and 307, the unipolar current collectors 301 and 309, the metal flow field plate 305, and the elastic members 302, 304, 306, and 308 has a guide hole near its edge for receiving a guide 202 and a fastener 106. The fastener 106, passing through the guide hole 201, presses the membrane electrode assemblies 303 and 307, the unipolar current collectors 301 and 309, the metal flow field plate 305, and the elastic members 302, 304, 306, and 308 together.

[0040] Figure 4 A front view of a metal flow field plate 305 in a pair of fuel cell assemblies 103a and 103b is shown as an example. The metal flow field plate 305 consists of a first surface 305a and a second surface 305b. The first surface 305a faces the cathode surface 303b of the first membrane electrode assembly 303, and the second surface 305b, located behind the first surface 305a, faces the anode surface 307a of the second membrane electrode assembly 307. The first surface 305a includes, for example, two serpentine flow channels 401 for airflow, and the second surface 305b includes a single serpentine flow channel 501 for hydrogen flow, as exemplarily shown in FIG5b. The two serpentine first flow channels 401 begin at two first inlet channels 402 and end at two first outlet channels 403 to form a flow field for air on the first surface 305a. A single serpentine second flow channel 501 on the second surface 305b of the metal flow field plate 305 begins at the second inlet pipe 405 and ends at the second outlet pipe 406, thereby forming a flow field for hydrogen on the second surface 305b. The first inlet pipe 402 and the first outlet pipe 403 are located on the first surface 305a at the first edge 404 of the flow field plate 305. The second inlet pipe 405 and the second outlet pipe 406 are also located on the second surface 305b near the first edge 404 of the flow field plate 305, as exemplarily shown in FIG5b.

[0041] The air pressure difference between the first inlet pipe 402 and the first outlet pipe 403 of the air flow field drives air to flow on the first surface 305a. Similarly, the pressure difference between hydrogen and water vapor between the second inlet pipe 405 and the second outlet pipe 406 of the hydrogen flow field drives hydrogen to flow on the second surface 305b. Pressure drops occur along the lengths of flow channels 401 and 501, so the air and hydrogen supplied at inlet pipes 402 and 405, respectively, are at higher pressures from the aeration device 110 and the inlet manifold 104. The first inlet pipe 402 is connected to the inlet pipe 109 of the fuel cell stack 100, and the first outlet pipe 403 is connected to the outlet pipe 108 of the fuel cell stack 100. The second inlet pipe 405 is connected to the inlet manifold 104, and the second outlet pipe 406 is connected to the outlet manifold 105 positioned on the end plate 102. The first inlet pipe 402 (also referred to as the open cathode) receives air, namely reactant air and coolant air. Aeration device 110 blows air onto fuel cell assembly 103 at a predetermined pressure. Since the first inlet line 402 is open, the pressure drop at the first inlet line 402 is minimal, and the air flows in the first flow channel 401 at the same pressure as the predetermined pressure. Coolant air removes heat from the fuel cell stack 100 through forced convection, and reactant air flows through the first flow channel 401 to participate in the electrochemical reaction. Reactant air from the first flow channel 401 diffuses toward the cathode surface 303b of membrane electrode assembly 303, and hydrogen from the second flow channel 501 diffuses toward the anode surface 307a of membrane electrode assembly 307.

[0042] Two serpentine first flow channels 401 are formed on the first surface 305a of the metal flow field plate 305 by stamping, which results in a single serpentine second flow channel 501 being formed on the second surface 305b of the metal flow field plate 305. The serpentine first flow channels 401 and serpentine second flow channels 501 force the reactants (i.e., air and hydrogen) to flow across the entire active region of the first surface 305a and the second surface 305b, eliminating stagnant areas caused by inappropriate reactant distribution. The serpentine first flow channels 401 on the first surface 305a limit the pressure drop along the first flow channels 401 and control water buildup in the fuel cell stack 100. Because the first flow channels 401 and the second flow channels 501 are located on opposite sides of the metal flow field plate 305, crossover of air and hydrogen at the inlet of the metal flow field plate 305 is prevented.

[0043] The metal flow field plate 305 also includes grooves 407 formed along the length of the first flow channel 401 and the second flow channel 501 on the edges of the first surface 305a and the second surface 305b. The grooves 407 accommodate resilient members 304 and 306, i.e., gaskets. The metal flow field plate 305 also includes guide holes, such as 201a, 201b, ..., 201f, to accommodate fasteners 106 and guides 202 passing through them. The metal flow field plate 305 is made of stainless steel, thus exhibiting high strength, high chemical stability, significantly lower cost, and ease of mass production. In embodiments, the metal flow field plate 305 also has a protective coating, for example, of a precious metal, to prevent corrosion of the first surface 305a and the second surface 305b.

[0044] Figures 5A to 5B An enlarged front view of the first surface 305a and the second surface 305b of the metal flow field plate 305 is shown as an example. Figure 5A The exemplary first surface 305a shown illustrates two serpentine first flow channels 401 having two first inlet conduits 402. The width of the first inlet conduits 402 is the same as the width of the first flow channels 401, thus minimizing the pressure drop in the reactant air from the first inlet conduits 402 to the first flow channels 401. The two serpentine first flow channels 401 are adjacent, extend parallel to each other, and terminate at a first outlet conduit 403.

[0045] Figure 5B The second surface 305b, exemplarily shown, illustrates a single serpentine second flow channel 501 with a second inlet conduit 405. The second inlet conduit 405 is an orifice in the metal flow field plate 305 that connects to the inlet manifold 104 of the fuel cell stack 100. Similarly, a second outlet conduit 406 for hydrogen is an orifice in the metal flow field plate 305 located at a first edge 404 on the second surface 305b that connects to the outlet manifold 105 of the fuel cell stack 100. There are no manifolds for the first flow channel 401 and the second flow channel 501. The flow of air and hydrogen through the first flow channel 401 and the second flow channel 501 can be laminar or turbulent.

[0046] The metal flow field plate 305 is referred to as a bipolar plate due to the flow fields on both sides of the metal flow field plate 305. A first flow channel 401 is formed by stamping on a first surface 305a. The first flow channel 401 is a recess of a certain depth on the first surface 305a of the metal flow field plate 305, which results in raised metal on the second surface 305b. Between the raised metal on the second surface 305b, a serpentine second flow channel 501 with the same depth as the first flow channel 401 is formed. Therefore, forming two first flow channels 401 on the first surface 305a results in forming a single second flow channel 501 on the second surface 305b. Thus, the process of manufacturing the metal flow field plate 305 is simple and effortless.

[0047] Figure 6 An exemplary front view of elastic members such as 302, 304, 306, and 308 engaging with the metal flow field plate 305 or the unipolar current collectors 301 and 309 is shown. The elastic members 302, 304, 306, and 308 are, for example, gaskets. The elastic members 304 and 306 are respectively accommodated in grooves 407 on the first surface 305a and the second surface 305b of the metal flow field plate 305. Similarly, the elastic members 302 and 306 are respectively accommodated in grooves (not shown) in the unipolar current collectors 301 and 309. The elastic members 302, 304, 306, and 308 prevent hydrogen and air leakage; that is, when the fuel cell assembly 103 is compressed, the elastic members 302, 304, 306, and 308 provide reactant sealing. Elastic members 302, 304, 306, and 308 also provide vibration and shock resistance to the fuel cell stack 100, and prevent [damage / impact] when compressed within the fuel cell stack 100. Figure 3The mechanical connection of components (such as 301a, 303, 305, 307, and 309) is exemplarily shown. Elastic members 302, 304, 306, and 308 are made of materials with greater compressibility and good sealing properties (such as silicone, PTFE, EPDM rubber, etc.). Elastic members 304 and 306 seal the inactive regions of the metal flow field plate 305 and expose the active regions of the metal flow field plate 305 to the membrane electrode assemblies 303 and 307. The active regions include the flow fields comprising the inlet conduits 402 and 405 and the outlet conduits 403 and 406 on the metal flow field plate 305. On the unipolar current collectors 301 and 309, elastic members 302 and 308 seal the inactive regions and expose the active regions to the membrane electrode assemblies 303 and 307. Elastic members 302, 304, 306, and 308 can be pre-cut or can be formed in situ. During the assembly of the fuel cell stack 100, the on-site shaped elastic members can be solidified by activation and exposure to radiation. The elastic members 302, 304, 306, and 308 also include multiple guide holes, such as 201g and 201h, which are similar to and aligned with the guide holes 201a, 201b, ..., 201f of the metal flow field plate 305 to accommodate the guide 202 and the fastener 106, thereby maintaining the structural integrity of the fuel cell stack 100. The elastic members 302, 304, 306, and 308 are non-conductive and provide electrical insulation between the metal flow field plate 305 and the membrane electrode assemblies 303 and 307, and between the unipolar current collectors 301 and 309 and the membrane electrode assemblies 303 and 307.

[0048] Figure 7 A front view of a membrane electrode assembly (such as 303 and 307) of a fuel cell assembly (e.g., 103a and 103b) is shown as an example. For instance, membrane electrode assembly 303 is the central element of fuel cell assembly 103a in fuel cell stack 100, with elastic members 302 and 304 and a flow field designed and positioned around it. In membrane electrode assembly 303, the electrolyte, electrodes (i.e., the anode and cathode surfaces), and reactants (oxygen and hydrogen) are all in contact. Because ambient air is used instead of pure oxygen, the amount of oxygen available for the electrochemical reaction is less; therefore, membrane electrode assembly 303 is thinner to reduce resistance in fuel cell assembly 103a. Furthermore, catalyst layers on the anode surface 303a and cathode surface 303b of membrane electrode assembly 303 reduce the cost of membrane electrode assembly 303. Membrane electrode assembly 303 optimizes the efficiency of fuel cell stack 100 for both portable and stationary applications. Membrane electrode assembly 303 allows proton transport while blocking reactants, namely hydrogen and oxygen, at a relatively low temperature of about 20°C to about 80°C.

[0049] The active regions of the metal flow field plate 305 and the unipolar current collector plate 301 are exposed to the anode surface 303a and cathode surface 303b of the membrane electrode assembly 303. Hydrogen gas from the flow channel 401 of the unipolar current collector plate 301 diffuses toward the anode surface 303a of the membrane electrode assembly 303, and oxygen gas from the flow channel 401 of the metal flow field plate 305 diffuses toward the cathode surface 303b of the membrane electrode assembly 303, so as to carry out an electrochemical reaction in the membrane electrode assembly 303. Byproducts of the electrochemical reaction diffuse toward the outlet pipe 108 and the outlet manifold 105 through the outlet pipes 403 and 405 on the metal flow field plate 305. As exemplarily shown, similar to the elastic members 301, 304, 306 and 308, the membrane electrode assembly 303 also has guide holes, such as 201i, aligned with the guide holes 201a, 201b, ..., 201f of the metal flow field plate 305 to accommodate the fastener 106 and the guide 202.

[0050] Figure 8 An exemplary front view of a unipolar current collector 309 of a fuel cell stack 100, having two or more flow channels (such as 801 on the front surface 309a), is shown. Flow channels 801 extend from two inlet lines 802 to two outlet lines 803. The two inlet lines 802 and two outlet lines 803 are structurally similar to, consistent with, and function the two first inlet lines 402 and two first outlet lines 403 of a metal flow field plate 305. Flow channels 801 on the front surface 309 face the cathode surface 307b of the membrane electrode assembly 307. Similar to the first surface 305a of the metal flow field plate 305, flow channels 801 carry oxygen for the half-cell reaction at the membrane electrode assembly 307. The rear surface of the unipolar current collector 309, behind the front surface 309a, is flat and rests against the end plate 102 of the fuel cell stack 100. The unipolar current collector 309 also includes a groove 804 along its periphery for receiving a resilient member 308. The unipolar current collector 309 has a support handle 805 extending from its side for connecting the fuel cell stack 100 to an external circuit to draw current from the fuel cell stack 100. The unipolar current collector 309 also includes guide holes (such as 201j and 201k) for engaging with fasteners 106 and guides 202 to maintain the integrity of the fuel cell stack 100.

[0051] Figure 9An exemplary front view of a unipolar current collector 301 of a fuel cell stack 100 is shown. The unipolar current collector 301 has one or more flow channels, such as 901, on its front surface 301a. Flow channels 901 extend from an inlet conduit 902 to an outlet conduit 903. The inlet conduit 902 and outlet conduit 903 are structurally similar to, consistent with, and function the second inlet conduit 405 and the second outlet conduit 406 of the metal flow field plate 305. The flow channels 901 on the front surface 301a face the anode surface 303a of the membrane electrode assembly 303. Similar to the second surface 305b of the metal flow field plate 305, the flow channels 901 carry hydrogen gas for the half-cell reaction at the membrane electrode assembly 303. The rear surface behind the front surface 301a of the unipolar current collector 301 is flat and rests against the end plate 101 of the fuel cell stack 100. The single-pole current collector 301 also includes a groove 904 along its periphery for receiving a resilient member 302. The single-pole current collector 301 has a support handle 905 extending from one side for facilitating connection of the fuel cell stack to external circuitry. The current (amperes), voltage, frequency, and other current characteristics in the external circuitry connected to the single-pole current collectors 301 and 309 are adjusted to suit the electrical application requirements of the fuel cell stack 100. The single-pole current collector 301 also includes guide holes, such as 201l, for engaging with fasteners 106 and guides 202 to maintain the integrity of the fuel cell stack 100.

[0052] Figure 10An exemplary front view of an end plate (e.g., 101) of a fuel cell stack 100 is shown. End plate 101 provides mechanical support for the fuel cell stack 100. Metal flow field plates 305, membrane electrode assemblies 303 and 307, monopole current collectors 301 and 309, and end plates 101 and 102 are parallel to each other within the fuel cell stack 100. End plates 101 and 102 are robust to support the fuel cell stack 100 and to distribute pressure evenly across the fuel cell assembly 103 within the fuel cell stack 100. End plates 101 and 102 possess considerable compressive strength, vibration resistance, and shock resistance, and are stable at low temperatures ranging from approximately 20°C to approximately 80°C. The materials used for end plates 101 and 102 can be stainless steel, aluminum, titanium, nickel, polyethylene, polyvinyl chloride, etc. At the other end of the fuel cell stack 100, end plate 102 has an inlet manifold 104 and an outlet manifold 105 for hydrogen in the fuel cell stack 100. An inlet manifold 104 in endplate 102 connects to the inlet line 902 of the unipolar current collector plate 301 and the inlet line 405 of the metal flow field plate 305, and an outlet manifold 105 in endplate 102 connects to the outlet line 903 of the unipolar current collector plate 301 and the outlet line 406 of the metal flow field plate 305. The inlet manifold 104 is connected to a valve via an external conduit to supply a measured amount of hydrogen to the fuel cell stack 100. Unused heated hydrogen in the fuel cell stack 100 is discharged through the outlet manifold 105. The outlet manifold 105 may be connected to an external conduit that connects to valves, heat exchangers, and any other desired power plant auxiliary components to utilize injected water vapor. Figure 2 The guide 202 shown is inserted through the guide hole 201 in the end plates 101 and 102.

[0053] Figures 11A to 11BA perspective view of a cover plate 107 of a fuel cell stack 100 is shown as an example. The cover plate 107 rests on the first edges 101a and 102a of end plates 101 and 102 and houses an aeration device 110. The exhaust port 1101 of the aeration device 110 is connected to an air inlet pipe 109 of the fuel cell stack 100. Reactant air and coolant air reach the fuel cell assembly 103 in the fuel cell stack 100 through the air inlet pipe 109. Oxygen in the air participates in the electrochemical reaction in the fuel cell stack 100. Stoichiometric amounts of reactant air and coolant air are blown into the inlet pipe 109 by the aeration device 110 to react with a measured amount of hydrogen entering through the inlet manifold 104. Since the electrochemical reaction is exothermic, the heat generated in the fuel cell assembly 103 is transferred to the metal flow field plate 305, the monopole current collectors 301 and 309, and the membrane electrode assemblies 303 and 307. Water vapor generated during the electrochemical reaction absorbs some heat, and an active coolant, such as coolant air fed into the fuel cell stack 100 through the first flow channel 401 in the metal flow field plate 305, absorbs the remaining heat in the fuel cell assembly 103. The hot air and water vapor from the fuel cell assembly 103 are collected together in the outlet pipe 109. Heat from the hot air and water vapor is extracted via an external heat exchanger installed in the recirculation pipe 111. The hot air exchanges heat with the fluid in the heat exchanger, and then its temperature decreases to room temperature. The room temperature air is mixed with ambient air at the outlet 1101 of the aeration device 110 and supplied to the fuel cell stack 100 via the air inlet pipe 109. The water content in the water vapor can be used to humidify the air at the air inlet pipe 109. Hydrogen gas at the inlet manifold 104 is pumped at a higher pressure than the air at the inlet pipe 109. This prevents reactant cross-contamination and improves the stability of the fuel cell assembly.

[0054] Figures 12A to 12C An exemplary illustration shows a housing 1201 and a device for positioning an aeration device 110. Figures 11A to 11B The mounting devices (such as 1202 and 1203) on the cover 107 are exemplarily shown. An aeration device 110 is housed within a housing 1201, which is supported by the mounting devices. The mounting devices include clamps 1202 and clamp gaskets 1203, which are attached to the housing 1201 via fasteners such as nuts and bolts. The performance of the fuel cell stack 100 depends on the pressure of the reactant gases, hydrogen, and air. The aeration device 110 (such as a blower) ensures that the air pressure at the outlet 1101 of the aeration device 110 is approximately 2 to 4 times the ambient atmospheric pressure. The fan speed of the aeration device 110 is adjusted to change the airflow supplied to the fuel cell assembly 103. The amount of stoichiometric oxygen entering the fuel cell stack 100 is controlled by a controller that regulates the electrical power of the aeration device, thereby controlling the compression and airflow into the fuel cell stack 100.

[0055] In this embodiment, a humidifier is also included in the membrane electrode assemblies (such as 303 and 307 of fuel assembly 103). In the humidifier, since the air from inlet pipe 109 may be dry, dry inlet air flows along the humidifier side to obtain humidified air. In this embodiment, the humidifier may be part of aeration device 110 and may supply humidified air at inlet pipe 109 of fuel cell stack 100. The humidified air interacts with membrane electrode assemblies 303 and 307, thereby ensuring the performance of fuel cell stack 100 is not affected due to the dry proton exchange membranes.

[0056] The fuel cell stack 100 is portable and can be used as a backup generator. The fuel cell stack 100 offers extended operating time, high reliability, high efficiency, and reduced environmental impact. The fuel cell stack 100 can be used as a primary or backup power source for laptops, military equipment, battery chargers, vehicles, etc. The fuel cell stack 100 offers the following technological advancements in battery technology: it directly converts chemical potential energy into electrical energy. When implemented in electric vehicles, such a fuel cell stack 100 acts as the primary power source and is highly efficient because it avoids the thermal bottleneck typically found in internal combustion engine vehicles. Such electric vehicles emit only water vapor and a small amount of heat. An external heat exchanger is also used to extract heat from the fuel cell assembly 103. The fuel cell stack 100 is highly efficient because the exhaust gases are merely water vapor and heat from the fuel cell stack 100, rather than harmful greenhouse gases. The fuel cell stack 100 has no moving parts and is therefore far more reliable than a conventional internal combustion engine. The reactants supplied to the fuel cell stack 100 are hydrogen and air, and the hydrogen can be produced in an environmentally friendly manner, unlike the oil extraction and refining used in internal combustion engines.

[0057] The inlet manifold 104 and outlet manifold 105 of the fuel cell stack 100 are configured for hydrogen only, while oxygen is supplied via an open cathode, thus preventing reactant cross-contamination. The elastic members 302, 304, 306, and 308 are identically and simply designed for the two surfaces 305a and 305b of the metal flow field plate 305. Cooling of the fuel cell stack 100 is achieved by simply installing an aeration device 110 (such as a blower). Coolant air is delivered via the same flow channels as reactant air, thus keeping the design of the metal flow field plate 305 simple and lightweight. The serpentine flow channels 401 and 501 on the two surfaces 305a and 305b of the metal flow field plate 305 eliminate the problem of water accumulation in the fuel cell stack 100. The serpentine flow channels 401 and 501 push downwards water droplets trapped in the cathode surface of the membrane electrode assembly (such as 303). The serpentine flow channels 401 and 501 uniformly distribute the reactants on the membrane electrode assembly 303, thereby improving the efficiency of the fuel cell stack 100. Since there are two flow fields on both sides of the metal flow field plate 305, seam welding between the two plates is avoided, thus reducing the weight and size of the fuel cell stack 100. Assembling such a fuel cell stack 100 using the guide 202 and guide holes 201 is also straightforward.

Claims

1. A metal flow field plate (305) in a pair of fuel cell assemblies (103a, 103b), the metal flow field plate (305) comprising: a first surface (305a) comprising two or more serpentine first flow channels (401), wherein each of the two or more serpentine first flow channels (401): receive air from two or more first inlet tubes (402) located on the first surface (305a), wherein the two or more first inlet tubes (402) are operably connected to a discharge port (1101) of an aeration device (110), and discharge air from two or more first outlet tubes (403) located on the first surface (305a); and a second surface (305b) behind the first surface (305a) comprising one or more serpentine second flow channels (501) formed by stamping on the first surface (305a), wherein each of the one or more serpentine second flow channels (501): receive hydrogen gas from one or more second inlet tubes (405) located on the second surface (305b), and discharge hydrogen gas from one or more second outlet tubes (406) located on the second surface (305b), wherein the two or more serpentine first flow channels (401) and the one or more serpentine second flow channels (501) are located on both sides of the metal flow field plate (305), wherein the one or more second inlet tubes (405) interface with one or more inlet manifolds (104) positioned on a pair of end plates (102), and wherein the one or more second outlet tubes (406) interface with one or more outlet manifolds (105) positioned on the pair of end plates (102).

2. The metal flow field plate (305) of claim 1, further comprising a groove (407) formed on an edge of each of the first surface (305a) and the second surface (305b) along a length of the two or more serpentine first flow channels (401) and the one or more serpentine second flow channels (501) for accommodating one or more elastic members (304, 306).

3. The metal flow field plate (305) of claim 1, wherein the two or more first inlet tubes (402) and the two or more first outlet tubes (403) are located at a first edge (404) of the metal flow field plate (305).

4. The metal flow field plate (305) of claim 1, wherein each of the one or more elastic members (304 and 306) is one of pre-cut form and formed in place by curing with activation and exposure to radiation during assembly of the pair of fuel cell assemblies (103a, 103b). ​ 5. The metal flow field plate (305) of claim 1, wherein air and hydrogen reactively engage with a membrane electrode assembly (303 and 307) in each of the pair of fuel cell assemblies (103a, 103b) for supplying current to an electrical circuit.

6. The metal flow field plate (305) of claim 5, wherein: air from the two or more serpentine first flow channels (401) diffuse toward a cathode surface (303b) of the membrane electrode assembly (303) of the fuel cell assembly (103a), and hydrogen from the one or more serpentine second flow channels (501) diffuse toward an anode surface (307a) of the membrane electrode assembly (307) of the fuel cell assembly (103b).

7. The metal flow field plate (305) of claim 1, wherein the air sparging device (110) is one of a blower and a centrifugal pump.

8. A fuel cell stack (100), comprising: a pair of end plates (101, 102), each of the pair of end plates (101, 102) including one or more inlet manifolds (104) and one or more outlet manifolds (105) for hydrogen; a plurality of fuel cell assemblies (103) positioned between the pair of end plates (101, 102), wherein a pair of fuel cell assemblies (103a, 103b) of the plurality of fuel cell assemblies (103) includes: a pair of membrane electrode assemblies (303, 307), each of a first membrane electrode assembly (303) and a second membrane electrode assembly (307) including an anode face (303a, 307a) and a cathode face (303b, 307b); a metal flow field plate (305) positioned between the first membrane electrode assembly (303) and the second membrane electrode assembly (307), the metal flow field plate (305) including: a first surface (305a) including two or more serpentine first flow channels (401) of air facing the cathode face (303b) of the first membrane electrode assembly (303), and a second surface (305b) behind the first surface (305a) including one or more serpentine second flow channels (501) of hydrogen facing the anode face (307a) of the second membrane electrode assembly (307), wherein each of the one or more serpentine second flow channels (501) receives hydrogen from one or more second inlet conduits (405) located on the second surface (305b) and exhausts hydrogen from one or more second outlet conduits (406) located on the second surface (305b), and a cover plate (107) removably attached to a first edge (101a, 101b) of the pair of end plates (101, 103) for housing an air sparging device (110). wherein the two or more serpentine first flow channels (401) and the one or more serpentine second flow channels (501) are located on both sides of the metal flow field plate (305), wherein the one or more second inlet manifolds (405) are in engagement with the one or more inlet manifolds (104), and wherein the one or more second outlet manifolds (406) are in engagement with the one or more outlet manifolds (105).

9. The fuel cell stack (100) as claimed in claim 8, wherein the metal flow field plate (305) further comprises a groove (407) formed on an edge of each of the first surface (305a) and the second surface (305b) along a length of the two or more serpentine first flow channels (401) and the one or more serpentine second flow channels (501), the groove (407) for accommodating one or more elastic members (304, 306), wherein each of the one or more elastic members (304, 306) is positioned in the groove (407) on the edge of each of the first surface (305a) and the second surface (305b) of the metal flow field plate (305) for sealing reactants.

10. The fuel cell stack (100) as claimed in claim 8, further comprising a pair of monopolar current collector plates (301, 309) for collecting electric current generated in the plurality of fuel cell assemblies (103), wherein each of the pair of monopolar current collector plates (301, 309) is positioned between an end plate (101, 102) and one of the first membrane electrode assembly (303) or the second membrane electrode assembly (307).

11. The fuel cell stack (100) as claimed in claim 10, wherein a plurality of fasteners (106) and guides (202) compress the pair of end plates (101, 102), the plurality of fuel cell assemblies (103) and the pair of monopolar current collector plates (301, 309) together.

12. The fuel cell stack (100) as claimed in claim 8, wherein the cover plate (107) comprises: an air inlet pipe (109) of the fuel cell stack (100) removably engaged with a discharge port (1101) of the aeration device (110), an air outlet pipe (108) of the fuel cell stack (100) engaged with the metal flow field plate (305), and a recirculation conduit (111) connecting the air outlet pipe (108) to the discharge port (1101) of the aeration device (110) through a heat exchange mechanism for recirculation of air in the fuel cell stack (100).

13. The fuel cell stack (100) as claimed in claim 12, wherein the aeration device (110) is a blower or a fan.

14. The fuel cell stack (100) as claimed in claim 12, wherein the heat exchange mechanism is a heat exchanger or a heat sink.

15. The fuel cell stack (100) as claimed in claim 12, wherein the air inlet pipe (109) is a flexible pipe.

13. The fuel cell stack (100) of claim 9, wherein each of the one or more elastic members (304, 306) is one of pre-cut form and formed in place by curing with activation and exposure to radiation during assembly of the fuel cell stack (100).

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