Uniform current density fuel cells

Abstract

A bipolar plate for a fuel cell assembly has a bipolar frame configured with two reverse image faces of different function comprising; anode flow channels formed of a first portion AFC fluidly connect

Description

17 1225 TECHNICAL FIELD

[0001] The present disclosure relates to distribution of fuel and coolant in a fuel cell assembly. BACKGROUND

[0002] A typical fuel cell system includes a fuel cell stack for generating electricity, a hydrogen supply as a fuel to the fuel cell stack, an oxygen (air) supply system for supplying oxygen containing air as an oxidant for the electrochemical reaction and thermal management for removing reaction heat from the fuel cell stack and managing humidity in the stack and water removal. The fuel cell system generates heat and water as well as electricity.

[0003] In fuel cell assemblies, each unit, has an anode, a cathode and an electrolyte (electrolyte membrane). Hydrogen is supplied to the anode and oxygen containing air is supplied to the cathode. By way of a membrane electrode assembly (MEA) the hydrogen and oxygen produce electricity, heat and water.

[0004] A stack is formed from a number of such fuel cells arranged with separate anode and cathode fluid flow paths. Such a stack is typically in the form of a block comprising numerous individual fuel cell plates held together by end plates at either end of the stack. It is important that the polymeric ion transfer membrane remains hydrated for efficient operation. It is also important that the temperature of the stack is controlled. Thus, coolant may be supplied to the stack for cooling and / or hydration.

[0005] In hydrogen fuel cells, hydrogen gas is supplied to the fuel cell from a source outside the fuel cell. Such fuel cells normally include a proton exchange membrane (PEM) sandwiched between electrodes, together comprising the membrane-electrode assembly (MEA).

[0006] An important consideration in the operation of such fuel cells is the management of water within the system. During operation of a PEM fuel cell, product water from the reaction between hydrogen and oxygen is formed at catalytic sites of the MEA. This water is in one or more phases of liquid, vapor and transitional depending on temperature and pressure when produced and it must be exhausted from the MEA via the cathode diffusion structure at the same time that oxygen is transported to the cathode face of 17 1225 the MEA. However, it is also important that the ME A remains suitably hydrated to ensure that the internal electrical resistance of the cell remains within tolerable limits. Failure to control the MEA humidification leads to hot spots and potential cell failure and / or poor electrical cell performance. The anode and cathode fluid flow field plates may each include a rigid, electrically conductive, material having fluid flow channels in the surface adjacent the respective diffusion structure for delivery of the reactant gases (for example, hydrogen and oxygen) and removal of the exhaust gases (for example, unused oxygen and water vapor).

[0007] Fuel cell stacks comprise a series of individual fuel cells built up layer by layer into a stack arrangement. Each fuel cell itself may include various layered components, such as a polymer electrolyte membrane, gas diffusion layers, fluid flow plates, and various sealing gaskets for maintaining fluid tightness and providing fluid fuel and oxidant distribution to the active surfaces of the membrane. The fluid inputs and fluid outputs are directed through flow fields and plates at the fuel cell level and through connected manifolds at the stack level. Common ducts are often used to feed oxidant and fuel to the fuel cell in fuel cell assemblies forming a stack.

[0008] In a typical high power fuel cell arrangement, cooling fluid is injected into the anode or cathode face of a fuel cell and disperses. Uneven cooling is suboptimal and impacts uniformity of operation and reduces efficiency. Fuel cell anode side flow fields require periodic purging to remove impurities in complete purging negatively effects performance by way of current density.

[0009] High efficiency PEM fuel cells (PEMFC) produce heat when operating and the removal or management of same from the fuel cell stack is a factor because efficiency is directly affected. To keep a temperature within a nominal range while current is flowing, the heat must be reduced or be taken away. It is therefore desiderata to: (1) reduce uneven heat removal in fuel cells forming a stack and (2) reduce non uniform current density within a fuel cell. DISCLOSURE

[0010] The following description of examples of implementations, reference is made to the accompanying drawings that form a part hereof, and which show, by way of illustration, specific implementations of the present disclosure that may be utilized. Other implementations may be utilized, and structural changes may be made without departing from the scope of the present disclosure.

[0011] Disclosed are aspects of exemplary implementations of reducing uneven heat removal in fuel cells forming a fuel cell. 17 1225

[0012] Disclosed are aspects of exemplary implementations of providing for even cooling within a fuel cell.

[0013] Disclosed are aspects of exemplary implementations of providing for uniform fuel flow within a fuel cell flow field.

[0014] Disclosed are exemplary aspects of implementations of devices and methods to improve evenness of current density in fuel cells systems including a bipolar frame having a first end and a second end and configured with two reverse image faces of different function configured with anode flow channels formed of a first portion then a gap and a second portion. The first and second portions remain fluidly connected regardless of the gap and the anode flow channels are fluidly connected to the first and second anode flow passages. The gap in each anode flow channel is positioned at least 85% downstream from one of the first and second anode flow passages. Including a cathode field configured with inlet cathode flow channels open to first cathode fluid passage but blocked from the second cathode fluid passage via humps and having outlet cathode flow channels blocked by humps from the first cathode flow passage but open to the second cathode flow passage. Moreover, the first end includes at least one air inlet, at least one water inlet, and at least one hydrogen outlet and the second end includes at least one cathode fluid outlet, and at least one hydrogen inlet and the first cathode flow passage is fluidly connected to the and the second cathode flow passage is fluidly connected to the outlet cathode flow channels. In some instances further included is a cathode gas diffusion layer in contact with the cathode flow field. In some instances further included is an anode gas diffusion layer in contact with the anode flow field. In some instances the gap in each anode flow channel is positioned at least 90% downstream from one of the first and second anode flow passages.

[0015] Disclosed are exemplary aspects of implementations of devices and methods to improve evenness of current density in fuel cells systems including a fuel cell with a first and second bipolar plate, each bipolar plate. Each bipolar plate configured with an anode flow field on its second face having anode flow channels (AFC and AFC’) fluidly connected to the first and second anode flow passages. Each also including a cathode flow field on a first face configured with inlet cathode flow channels (iCFC) open to first cathode fluid passage (340) but blocked from the second cathode fluid passage via humps and outlet cathode flow channels (oCFC) blocked by humps from the first cathode flow passage but open to the second cathode flow passage,a MEA between the cathode flow field of the first bipolar plate and the anode flow field of the second bipolar plate, a gas diffusion layer between the MEA and each flow field. The first end of each bipolar plate includes at least 17 1225 one single air inlets, a water inlet and a hydrogen outlet. The second end of each bipolar plate includes a single cathode fluid outlet and a hydrogen inlet wherein the first cathode flow passage is fluidly connected to the iCFC; and, wherein the second cathode flow passage is fluidly connected to the “oCFC”. In some instances a cathode gasket configured to form a seal around the cathode face of the first bipolar plate and the MEA and, an anode gasket configured to form a seal around the anode face of the second bipolar frame and the MEA are included.

[0016] Disclosed are exemplary aspects of implementations of devices and methods to improve evenness of current density in fuel cells systems including placing a plurality of cells formed into a stack, each fuel cell comprising an anode flow field on its second face having anode flow channels (AFC and AFC’) fluidly connected to the first and second anode flow passages and a cathode flow field on a first face comprising inlet cathode flow channels (iCFC) open to first cathode fluid passage but blocked from the second cathode fluid passage via humps and outlet cathode flow channels (oCFC) blocked by humps from the first cathode flow passage but open to the second cathode flow passage. On the first end of each bipolar plate forming a hydrogen outlet, an air inlet and a water inlet and on the second end of each bipolar plate forming a hydrogen inlet, and a cathode fluid outlet. And, also placing gas diffusion layers on either side of an MEA. Sandwiching the gas diffusion layer and MEA between the anode flow field of one bipolar plate and the cathode flow field of another bipolar plate, adding hydrogen to the anode flow channels via the first anode fluid passage and adding cathode fluid of air and water to the cathode inlet flow channels via the first cathode fluid passage and, forcing diffusion of cathode fluids into the outlet cathode flow channels through the cathode gas diffusion layer forming an air inlet manifold within the fuel cell stack fluidly connected to the cathode flow field of each fuel cell in the stack and also forming a cathode exhaust manifold within the fuel cell stack fluidly connected to the cathode flow field of each fuel cell in the stack.

[0017] In some instances periodically purging the anode flow channels and, wherein the purge is uniform across the anode side of the MEA. In some instances the uniform purge reduces dead zones and results in increased current density. In some instances the force diffusion of cathode fluid from the iCFC to the oCFC evenly cools the MEA. FIGURES

[0018] The present application is further understood when read in conjunction with the appended drawings. For the purpose of illustrating the subject matter, there are shown in the drawings exemplary aspects of the subject matter; however, the presently disclosed subject matter is not limited to the specific methods, devices, and systems disclosed.

[0019] The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.

[0020] Fig. 1 depicts aspects of a side exploded assembly view of an asymmetrical flow field fuel cell assembly.

[0021] side to cathode

[0022] Fig. 2 depicts aspects of a perspective exploded assembly view from anode side of an asymmetrical flow field fuel cell assembly. Fig. 3 A depicts aspects of a top view of the anode side of a frame with anode flow fields of the asymmetrical flow field fuel cell assembly in Fig. 1.

[0023] Fig. 3B depicts aspects of an enlarged view of section “Y” of Fig. 3 A.

[0024] Fig. 3C. depicts a diagrammatic view of fuel flow through the anode flow fields of an asymmetrical flow field fuel cell assembly. 17 1225

[0025]

[0026] plates.

[0027] Fig. 3D illustrates a cut-away view of Fig. 3C along line “A”-“A”. Fig 4 illustrates a traditional serpentine pathway for symmetrical bipolar Fig. 5A depicts aspects of a top component view of the cathode side of a frame with cathode flow fields of an asymmetrical flow field fuel cell assembly in Fig. 1.

[0028] Fig. 5B depicts aspects of an enlarged view of section “Z” of Fig. 4A.

[0029] Fig. 5C depicts a diagrammatic view of fuel flow through the cathode flow fields of an asymmetrical flow field fuel cell assembly.

[0030] Fig. 5D illustrates a cut-away view of Fig. 4C along line “B”-“B”.

[0031] Fig. 6 depicts aspects of a top view of the cathode side of another asymmetrical fuel cell assembly.

[0032] Fig. 7 depicts aspects of a fuel cell stack formed from a plurality of asymmetrical fuel cell assemblies.

[0033] All descriptions and callouts in the Figures and all content therein are hereby incorporated by this reference as if fully set forth herein. All citations are hereby incorporated by this reference as if fully set forth herein. Aspects of the disclosure will now be described in detail with reference to the drawings, wherein like reference numbers refer to like elements throughout, unless specified otherwise. FURTHER DISCLOSURE 17 1225

[0034] The present disclosure may be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to be understood that this disclosure is not limited to the specific devices, methods, applications, conditions or parameters described and / or shown herein, and that the terminology used herein is for the purpose of describing particular exemplars by way of example only and is not intended to be limiting of the claimed disclosure.

[0035] Disclosed herein are aspects of methods and systems to provide for at least one of improved cooling and consistent compression of at least one of fluid flow plates, flow assemblies, fuel cells and fuel cells in a stack which improve efficiencies of electrical generation and reduce cost of production.

[0036] By right sizing cathode inlets and outlets to maintain pressure across a flow field and into a gas diffusion layer (GDL) from inlet to outlet on the cathode side of a fuel cell bottlenecks in fluid flow are at least one of eliminated and minimized. The expansion of air and addition of moisture as oxidant flows through the cathode side of a fuel cell assembly the volume inlet expands by at least a factor of 5 or more times, in some instances it expands by a factor of 50 or more, in some instances it expands by a factor of 100 or more, in some instances it expands by a factor of 200 or more. The instance fuel cell assembly, fuel cells formed from such assembly, and stack formed from a plurality of such fuel cells are a more efficient fuel cell stack by way of minimizing the bottlenecks. More efficient refers to improved power density during operation compared to a traditional fuel cell or stack utilizing a traditional fuel cell assembly outlet and inlets.

[0037] Figure 1 is a component overview of a fuel cell assembly and a fuel cell.

[0038] Two fuel cell assemblies 10 and 10’ each having bipolar plates providing fluid flow pathways cooperate when stacked together and compressed as part of a fuel cell stack and together function as a fuel cell 100 in that stack. Each bipolar plate has a first face and a second face. Each face is either an anode or a cathode.

[0039] Figure 2 shows aspects of a fuel cell assembly viewed cathode side up. Figures 3-6 show aspects of the anode side of a bipolar plate, assembly of the cathode side of a bipolar plate of this disclosure, and the cathode side of a bipolar plate of this disclosure.

[0040] A membrane electrode assemble (MEA) containing a proton exchange membrane (also known as a polymer electrode membrane) is normally a multi-layer interface whereby protons from the anode side of a fuel cell cross the MEA and the stripped off 17 1225 electron travels around the MEA to generate electricity. On the cathode side oxygen is provided and the hydrogen protons eventually form water with some of the oxygen provided.

[0041] The MEA 12 in a fuel cell assembly (or a fuel cell) traditional will have some gas diffusion layer or layers between the MEA and bipolar frame 13. On a first side of the MEA 12A which will be closest to the cathode flow field 14 of a bipolar frame 13 is a cathode gas diffusion layer (or layers) 15. On the opposite second side of the MEA 12B which will be closest to the anode flow field 16 of a bipolar frame 13 is an anode gas diffusion layer 17. The bipolar frame 13 has a first end 18 opposite a second end 19. Disclosed herein is a bipolar frame configured wherein the anode flow field 16 is formed as part of the bipolar frame. Disclosed herein is a novel bipolar plate 200 wherein the cathode face has a separate cathode outlet cover 20 attached to the bipolar frame and a separate cathode inlet cover 22 attached to the bipolar frame. Configuring the bipolar frame 13 to affix separate cathode inlet and outlet covers eliminates the waste material caused by using a single cathode frame thus reducing at least one of carbon footprint, cost and manufacturing cost. A separate water distribution cover 30 configured to affix over at least a portion of the cathode inlet cover optionally may be attached. One or more gaskets are added to seal the fuel cell assembly when forming fuel cells within a fuel cell stack. At least a cathode gasket 40 and an anode gasket 42.

[0042] Figure 3 A shows aspects of the anode flow field 16 of an asymmetrical bipolar plate, showing a portion of the anode gas diffusion layer 17. The asymmetry refers to the cathode flow fields versus the anode flow fields as described herein. At the first end 18 is an air inlet 300, a water inlet 310 and a hydrogen outlet 315. At the second end 19 is a cathode fluid outlet 320 and a hydrogen inlet 325. The hydrogen inlet is fluidly connected via a first anode fluid passage 330 to the anode face of the bipolar plate. The anode face is fluidly connected to a second anode fluid passage 335 that is fluidly connected to the hydrogen outlet 315. The water inlet 310 and air inlet 300 are fluidly connected to the cathode face of the bipolar plate.

[0043] Figure 3B shows section “Y” of Figure 3 A, it is a close up of a portion of the anode side flow field showing anode flow channels AFC and a gap “G” between the first portion of the anode flow channel AFC and the second portion of the anode flow channel AFC’ and said gap will be a hump on the cathode side of the bipolar plate - hence the asymmetrical nature of this bipolar plate. The gap, in operation, is a di minimis diversion and will also is configured to have a di minimis change in the throughflow of the anode fluid flow. The AFC is formed by an anode flow channel wall AFCW which terminates at 17 1225 an anode flow channel top TAFCW. Each ATFCW and connected TAFCW forms boundaries defining the cathode flow channels CFCs.

[0044] Figures 3C and 3D are a diagrammatic and cut-away views of the anode flow field 16 and the AFCs thereon. The hydrogen inlet 325 is fluidly connected to the first anode fluid passage 330 which is fluidly connected to the anode flow field 16. The gap in each flow filed is positioned nearest one of the hydrogen inlet 325 and hydrogen outlet 320. In some instances the gap is positioned at least 80% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 85% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 86% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 87% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 88% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 89% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 90% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 91% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 92% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 93% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 94% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 95% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 96% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least 97% from one of the hydrogen inlet and hydrogen outlet. In some instances the gap is positioned at least980% from one of the hydrogen inlet and hydrogen outlet.

[0045] In operation, hydrogen passes into the anode flow field along the line of arrow 600. During operation periodically the anode outlet 315 will be closed off and the hydrogen will diffuse along the line of arrow 602 into the anode gas diffusion layer 17 and remain until a periodic purge occurs. A controller, known in the art and not shown, sequences the purge and the opening and closing off of the hydrogen flow through the anode flow field. The gap “G” in the AFC does not block the hydrogen during purge and has a di minimis impact on the hydrogen flow during operation. Even and complete purging of the anode flow channels clears impurities and / or waste products from the anode flow channels and the anode gas diffusion layer thusly eliminates dead zones which are poorly purged regions of the anode side of the fuel cell and which reduce uniformity of the anode fluid flow 17 1225 across the MEA. Non uniform anode fluid flow across the MEA reduces uniform hydrogen flow which directly impacts current density. A more uniform flow of hydrogen equates to greater current density. If dead zones (areas with too little hydrogen) form on the anode side of the bipolar plate then the MEA will not receive uniform fuel and the current density will be uneven (non-uniform) in the fuel cell and the efficiency will be reduced which results in a decrease in current density. Our tests revealed that symmetrical anode and cathode flow fields on a bipolar plate provided less current density. If both sides of the bipolar plate have straight through flow channels insufficient cooling of the fuel cell occurs and current density is reduced and the fuel cell will overheat and be less efficient and / or damaged.

[0046] Traditionally both sides of a bipolar plate 1000 have reverse images of the same serpentine channels “SC” or fluid pathways (also referred to as symmetrical bipolar plates) as shown in Figure 4, which shows the anode face or flow field of a symmetrical bipolar plate, dead zones “DZ” occur. In such traditional symmetrical bipolar plates the fluid flow on the anode side is to move from inlet 1001 to outlet 1002 in a generally straight channel segment then turn 180 degrees to another generally straight segment and so forth. In some instances the straight channels are wavy or sinusoidal. The net result for the anode side of the MEA is a low current density dead zones “DZ” because the hydrogen will skip over portions of the serpentine channel “SC” along the lines of arrow 1005 through the anode gas diffusion layer. Such dead zones “DZ” at the MEA have reduced current density due to the lack of uniform distribution of hydrogen across the MEA. The result is a lower current density for the fuel call and in a stack of such fuel cells a lower current density for the fuel cell stack.

[0047] Figure 5A shows aspects of the cathode side of a bipolar plate. The air inlet 300 and the water inlet 310 are fluidly connected via a first cathode fluid passage 340 to the cathode face of the bipolar plate. The cathode face is fluidly connected to a second cathode fluid passage 345 which is fluidly connected to the cathode fluid outlet 320.

[0048] Figure 5B shows section “Z” of Figure 5A,. The cathode flow field is reverse image of the anode flow field walls and channels. Accordingly the anode side gaps form humps “H” on the cathode side and the anode flow channel walls AFCWs which terminate at an anode flow channel tops “TAFCW” form the cathode flow channels walls “CFCWs”. In this close up of a portion of the cathode side flow field the cathode inlet flow channels iCFCs and the cathode outlet flow channels “oCFC” and a humps Hs are visible. Figures 5B-5D show that the cathode inlet flow channel is in direct fluid communication with the first cathode fluid inlet 340 but has no direct outlet to the second cathode fluid passage 17 1225 345. Rather, it is blocked by the hump “H” and configured so that the cathode fluid flows via forced diffusion from “iCFCs” to the cathode GDL and then into the “oCFCs”. Therefore the cathode outlet flow channel “oCFCs” receive fluid flow, not directly from the first cathode fluid passage but rather via the force diffusion of the cathode fluid from the “iCFCs” through cathode GDL.

[0049] Figures 5C and 5D are a diagrammatic and cut-away views of the cathode flow field 14 and the CFCs thereon. The air inlet and water inlets are fluidly connected to the first cathode fluid passage 340 which is fluidly connected to the cathode flow field 14. The iCFC as described above receives direct flow of air and water from the inlets fluidly connected from the first end 18 and the cathode fluids pass into the iCFC along the line of arrow 700. During operation the air and water and water vapor in the cathode inlet fluid is blocked by the humps “H” and fills up the iCFC and via forced diffusion (diffusion under pressure) moves into the cathode gas diffusion layer 15 along the lines of arrows 702. Cathode fluids from the cathode GDL flow into the “oCFCs” and can exit the cathode flow field through the non-humped channels “oCFCs” through the second cathode fluid passage 345 into the cathode fluid outlet 320. Figure 5D shows the cut-away side view along line “B”-“B”. During operation the “iCFC “ is fill with cathode fluid 710 and such fluid 710 cannot exit the “iCFC” in a straight pathway being blocked by the hump “H” and is therefore forced to diffuse into the cathode GDL 15 and eventually finds a way out through “oCFCs” without humps blocking them.

[0050] Unlike the anode flow field which is configured for through flow and the flow of hydrogen is controlled by opening and closing the anode outlet, the cathode flow field is transporting a constantly moving fluid (during operation). The dead-end or hump block channels are configured to force a portion of the cathode fluid which contains water vapor and air into the cathode GDL which then cools the bipolar plate. Without the humps too little cathode fluid would diffuse into the GDL to evenly cool the bipolar plate. If the fuel cell is not operated within a target temperature range, generally between 70 to 90 degrees centigrade, the net system power will be reduced, for lower operating temperatures this is due to system parasitics such as compressors, pumps and the like reducing the net power output. For higher temperatures the hydration of the PEM membrane is affected, higher temperatures increase water evaporation, and the membrane can be overly dried, which increases the ohmic resistance and this reduces efficiency. The fuel cell including the MEA can be damaged by excessive heat, the glass transition temperature of the Nafion (RTM) membrane commonly used in the PEM of the MEA is approximately 120 Celsius, if the cell 17 1225 approaches this temperature the MEA can deform and ultimately melt, again reducing the current density and / or the life of the system.

[0051] Figure 6 shows aspects of an assembled bipolar plate with multiple inlets and outlets, cathode face up, with cathode gas diffusion layer 15 visible. Fluid containing the air, water, and water vapor from the air inlets 300 and the water inlets 310 fluidly pass into the CFC from the first cathode fluid passage 340 and through the cathode flow field along the lines of arrow 700 to the second cathode fluid passage 345 then to the cathode fluid (or exhaust) outlets 320. Those of ordinary skill in the art and the skilled artisan will recognize that the illustration of dual inlets and outlets is not a limitation and a larger number of inlets and / or outlets is clearly within the scope of the disclosure.

[0052] Figure 7 shows an assembly view of fuel cell stack 600 formed from a plurality of fuel cell assemblies 10(l-N) with the cathode gas diffusion layer 14, a first end plate 602 and a second end plate 604. A water outlet is also in fluid communication with the cathode fluid outlet.

[0053] The systems described throughout this disclosure can be utilized in a variety of applications for providing power generated by fuel cells. In some aspects, the systems disclosed throughout this application can be used in machine handling equipment (MHE), such as a forklift. In some aspects, the systems can be used in an unmanned aerial vehicle (UAV), such as a fixed or multi-rotor drone. In some aspects, the systems disclosed herein can be used in automotive applications, such as in cars, trucks or in stationary power systems. In some instances, the systems can be used in marine applications or in aerospace, such as manned or passenger bearing aircraft. It will be appreciated that the systems can be used in a variety of other applications, and the certain functional and physical parameters, such as component sizes and quantities, may be varied for specific applications and may be dictated by requirements for specific uses. Additional advantages to those described above include being able to fit the systems and related components (such as fuel cannister cylinders) into smaller spaces and to arrange systems and related components.

[0054] The components disclosed herein may utilized known materials that are used in the industry.

[0055] Throughout this specification, words are to be afforded their normal meaning as would be understood by those skilled in the relevant art. However, so as to avoid misunderstanding, the meanings of certain terms will be specifically defined or clarified.

[0056] While the disclosure has been described in connection with the various embodiments of the various figures, it will be appreciated by those skilled in the art that 17 1225 changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this disclosure is not limited to the particular embodiments disclosed, and it is intended to cover modifications within the spirit and scope of the present disclosure as defined by the claims.

[0057] Features of the disclosure that are described above in the context of separate embodiments may be provided in combination with a single embodiment. Conversely, various features of the disclosure that are described in the context of a single embodiment may also be provided separately or in any sub-combination. Finally, while an embodiment may be described as part of a series of steps or part of a more general structure, each said step may also be considered an independent embodiment in itself, combinable with others.

[0058] Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

17 12251. A bipolar plate for a fuel cell assembly comprising:a bipolar frame (13) having a first end (18) and a second end (19) and configured with two reverse image faces of different function comprising:an anode flow field (16) comprising:anode flow channels formed of a first portion (AFC) then a gap (G) and a second portion (AFC’);wherein the first and second portions remain fluidly connected regardless of the gap; andwherein the anode flow channels are fluidly connected to first and second anode flow passages (330 and 335); andwherein the gap in each anode flow channel is positioned at least 85% downstream from one of the first and second anode flow passages (330 and 335);a cathode flow field (14) comprising;inlet cathode flow channels (iCFC) open to a first cathode flow passage (340) but blocked from a second cathode flow passage (345) via humps (H); and outlet cathode flow channels (oCFC) blocked by humps (H) from the first cathode flow passage (340) but open to the second cathode flow passage (345);wherein the first end (18) includes:at least one air inlet (300),at least one water inlet (310), andat least one hydrogen outlet (315);and wherein the second end (19) includes:at least one cathode fluid outlet (320), andat least one hydrogen inlet (325);wherein the first cathode flow passage (340) is fluidly connected to the iCFC; and, wherein the second cathode flow passage (345) is fluidly connected to the “oCFC”.

2. The bipolar plate for a fuel cell assembly of Claim 1, further comprising a cathode gas diffusion layer (15) in contact with the cathode flow field (14).

3. The bipolar plate for a fuel cell assembly of Claim 2, further comprising an anode gas diffusion layer (17) in contact with the anode flow field (16).

4. The bipolar plate for a fuel cell assembly of any preceding claim, wherein the gap in each anode flow channel is positioned at least 90% downstream from one of the first and second anode flow passages (330 and 335).

5. The bipolar plate for a fuel cell assembly of Claim 4, wherein fluid flows into and out of the anode flow channels is via ports connected to the anode flow channels.17 1225

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