High efficiency PEM fuel cells

Abstract

A high efficiency fuel cell comprising a first bipolar plate with a cathode flow field on a first face and an anode flow field on its second face, a first end and a second end, wherein the first end of the bipolar plate includes a single air inlet, a single water inlet and a hydrogen inlet, and the second end of the bipolar plate includes a single cathode fluid outlet and a hydrogen outlet. The air inlet and water inlet are fluidly connected to a cathode flow field via a cathode flow field inlet and the cathode outlet area is at least 20% larger than the water inlet and air inlet area.

Description

HIGH EFFICIENCY PEM FUEL CELLSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a PCT Application, which claims priority to Provisional Application No. 63 / 733,382, filed on December 12, 2024; and of GB Patent Application No. 2319824.4, filed December 21, 2023, the disclosures of all of which are incorporate by reference herein in their entirety as if fully set forth TECHNICAL FIELD

[0002] The present disclosure relates to outlet fluid pressure control in fuel cell stacks, and in particular to membrane-type fuel cells.BACKGROUND

[0003] 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.

[0004] In a fuel cell assembly, 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.

[0005] 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.

[0006] 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).

[0007] 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 ontemperature 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 the MEA. However, it is also important that the MEA 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).

[0008] 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 each fuel cell in fuel cell assemblies forming a stack.

[0009] 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.

[0010] Additional problems in fuel cell assemblies include ensuring a uniform flow field for fluid distribution in fuel, oxidant, and coolant. Bottlenecks in the input or output of fuel, oxidant or water can result in uneven performance of a fuel cell in a stack. The footprint of a fuel cell stack may be critical in space limited applications, the type and number of supporting structures outside the fuel cell stack connected to the fuel cell stack impact this footprint. Reducing waste in constructing the plates forming fuel cell assemblies reduces cost and carbon footprint.

[0011] 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 it directly affects system efficiency. 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 (2) reduce fluid flow restrictions within astack; (3) reduce uneven cooling of fuel cells within a stack; and, (4) reduce fuel cells stack footprint.

[0012] DISCLOSURE

[0013] 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.

[0014] Disclosed are aspects of exemplary implementations of reducing uneven heat removal in fuel cells forming a fuel cell stack.

[0015] Disclosed are aspects of exemplary implementations of reducing fluid flow restrictions within a fuel cell stack.

[0016] Disclosed are aspects of exemplary implementations of reducing uneven cooling of fuel cells within a fuel cell stack.

[0017] Disclosed are aspects of exemplary implementations of devices, systems and methods of reducing uneven cooling of fuel cells within a fuel cell stack . Aspects include using a bipolar frame having a first end and a second end and having two faces, the first face configured as an anode flow field and on an opposite side of the bipolar plate a cathode flow field. The first end includes one of a single air inlet or a single air outlet, a single water inlet, and one of a single hydrogen outlet or a single hydrogen inlet. The second end includes a single cathode fluid outlet and a single hydrogen inlet or a single hydrogen outlet. The air inlet and water inlet are fluidly connected to one of the cathode or anode flow field wherein the cathode flow field is fluidly connected to the cathode flow field outlet which is fluidly connected to the cathode fluid outlet; and, wherein the cathode outlet area is one of at least 20% larger than the cathode water inlet and air inlet area combined, at least 25% larger than the cathode water inlet and air inlet area combined, and at least 30% larger than the cathode water inlet and air inlet area combined. In some instances including an anode gas diffusion layer in fluid communication with the anode flow field, membrane electrode assembly (MEA) in contact with the anode gas diffusion layer on its second side; and, a cathode gas diffusion layer in contact with the first side of the MEA. In some instances including ananode gasket to form a seal around the anode face of the bipolar frame when compressed into a fuel cell and a cathode gasket to form a seal around the cathode face of the bipolar plate when compressed into a fuel cell. In some instances including a cathode inlet cover affixed at the first end of the bipolar frame, a cathode outlet cover affixed over the second end of the bipolar frame and, a water guide affixed to at least a portion of at least one of the first end and the cathode inlet cover. In some instances the hydrogen fluid flow is concurrent (same direction) with the direction of the air and water fluid flow from end to end of the bipolar plate(s). In some instances the hydrogen fluid flow is counter current (opposite direction) with the direction of the air and water fluid flow from end to end of the bipolar plate(s).

[0018] Disclosed are aspects of exemplary implementations of devices, systems and methods of reducing uneven cooling of fuel cells within a fuel cell stack . Aspects include a first bipolar plate having a cathode flow field on a first face, an anode flow field on its second face, a first end and a second end. Also including a second bipolar plate having a cathode flow field on a first face, an anode flow field on its second face, a first end and a second end. 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 and the first end of each bipolar plate includes a single air inlet, a single water inlet, and a hydrogen outlet. The second end of each bipolar plate includes a single cathode fluid outlet and a hydrogen inlet. Configured whereby the air inlet and water inlet are fluidly connected to a cathode flow field via a cathode flow field inlet, the cathode flow field is fluidly connected to the cathode flow field outlet which is fluidly connected to the cathode fluid outlet and, the cathode outlet area is one of at least 20% larger than the water inlet and air inlet area, at least 25% larger than the water inlet and air inlet area, and at least 30% larger than the water inlet and air inlet area.

[0019] In some instances 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.

[0020] Disclosed are aspects of exemplary implementations of devices, systems and methods of reducing uneven cooling of fuel cells within a fuel cell stack configured with a plurality of high efficiency fuel cells formed into a stack An air inlet manifold formed within the fuel cell stack fluidly connected to the cathode flow field of each high efficiency fuel cell in the stack and, a cathode exhaust manifold formed within the fuel cell stack fluidlyconnected to the cathode flow field of each high efficiency fuel cell in the stack. In some instances fluid flow rate of standard liters per min through the cathode flow fields of the fuel cells comprising the stack is at least 13% greater than in a fuel cell stack with multiple cathode flow field air inlets and exhaust outlets.

[0021] Disclosed are aspects of exemplary implementations of devices, systems and methods of improving cathode fluid flow within a fuel cell stack including placing a plurality of cells formed into a stack. Each fuel cell having bipolar plates having a cathode flow field on a first face, an anode flow field on a second face, a first end, and a second end. On the first end of each bipolar plate forming a single air inlet, a single water inlet. On the second end of each bipolar plate forming a single cathode fluid outlet. Sandwiching a MEA between gas diffusion layer on each side. Placing the MEA and gas diffusion layers between bipolar plates. 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, forming a cathode exhaust manifold within the fuel cell stack fluidly connected to the cathode flow field of each fuel cell in the stack.

[0022] In some instances gaskets are placed between the bipolar plates to seal the bipolar plates whereby the cathode flow field and the anode flow fields are sealed and prevented from leaking. In some instances the cathode exhaust manifold has an area which is at least one of at least 20% larger than the air inlet manifold area, at least 25% larger than the air inlet manifold area, at least 30% larger than the air inlet manifold area. In some instances the fluid flow rate of standard liters per min through the cathode flow fields of the fuel cell stack is at least 13% greater than in a fuel cell stack with multiple cathode flow field air inlets and exhaust outlets. In some instances the cathode exhaust manifold has an area which is at least one of at least 50% larger than the air inlet manifold area, at least 60% larger than the air inlet manifold area, at least 70% larger than the air inlet manifold area. In some instances the cathode exhaust manifold has an area which is at least one of at least 80% larger than the air inlet manifold area, at least 90% larger than the air inlet manifold area, at least 100% larger than the air inlet manifold area.

[0023] Disclosed are aspects of exemplary implementations of devices, systems and methods of improving fluid flow within a fuel cell stack. Each fuel cell having bipolar plates having a cathode flow field on a first face, an anode flow on a second opposing face. Aspects of the high efficiency fuel cell assembly include a bipolar frame having an inlet end and anoutlet end and having two faces, the first face configured as an anode flow field and on an opposite side of the bipolar plate a cathode flow field. Said inlet end includes an air inlet, a water inlet, a hydrogen inlet. The outlet end includes a cathode fluid outlet and a hydrogen outlet.

[0024] In some instances the air and water inlet are in fluid communication with the cathode flow field and the hydrogen inlet and outlet are in fluid communication with the anode flow field, and, the hydrogen inlet and hydrogen outlets are on diagonally opposing comers of the anode flow field.

[0025] The anode and cathode fluids flow either concurrently (co current or parallel) each on one side of the bipolar plate or counter current with fluids on the anode side flowing generally the opposite direction of fluids on the cathode side.

[0026] In some instances the air and water inlet are in fluid communication with the anode flow field and the hydrogen inlet and outlet are in fluid communication with the cathode flow field, and, the hydrogen inlet and hydrogen outlets are on diagonally opposing comers of the anode flow field.

[0027] FIGURES

[0028] 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.

[0029] 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.

[0030] Fig. 1 depicts a side exploded assembly view of a high efficiency fuel cell assembly.

[0031] Fig. 2 depicts a perspective exploded assembly view from anode side to cathode side of a high efficiency fuel cell assembly.

[0032] Fig. 3 depicts a top view of the anode side of a frame with anode flow fields of the high efficiency fuel cell assembly in Fig. 1.

[0033] Fig. 4A depicts a top component view of the cathode side of a frame with cathode flow fields of a high efficiency fuel cell assembly in Fig. 1.

[0034] Fig. 4B depicts a top view of the cathode side of a frame with cathode components assembled thereon of the high efficiency fuel cell assembly in Fig. 4A.

[0035] Fig. 5 depicts a top view of the cathode side of a high efficiency fuel cell assembly.

[0036] Fig. 6A and 6B depict flow directions of the anode side and cathode side of the bipolar plate illustrating concurrent and counter current flows of fluids over the anode and cathode faces of a bipolar plate.

[0037] Fig. 7 a fuel cell stack formed from a plurality of high efficiency fuel cell assemblies.

[0038] 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.

[0039] FURTHER DISCLOSURE

[0040] 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.

[0041] Disclosed herein are aspects of methods and systems to provide for at least one of improved and 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.

[0042] By right sizing cathode inlets and outlets to maintain a nominal pressure across the cathode flow field and into a gas diffusion layer (GDL) from inlet to outlet on the cathode side of a fuel cell even predictable fluid flow is achieved. The expansion of air (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 afactor 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 an improved power density during operation compared to a traditional fuel cell or stack utilizing traditional fuel cell assembly outlet and inlets.

[0043] Figure 1 is a component overview of a fuel cell assembly and a fuel cell.

[0044] 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.

[0045] 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.

[0046] A membrane electrode assembly (MEA) containing a proton exchange membrane (also known as a polymer electrolyte membrane) is normally a multi-layer interface whereby protons from the anode side of a fuel cell cross the MEA and the stripped off electron travels around the external circuit to generate electricity. On the cathode side oxygen is provided, and the hydrogen protons eventually form water with some of the oxygen provided.

[0047] The MEA 12 in a fuel cell assembly (or a fuel cell) traditionally 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 face 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 face 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 face 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 fuelcells within a fuel cell stack. At least a cathode gasket 40 and an anode gasket 42may be present.

[0048] Figure 3 shows aspects of the anode side of a bipolar plate. 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. Those of ordinary sill in the art and the skilled artisan will recognize that it is within the scope of the disclosure that fluid flow on the anode and cathode sides of the bipolar may be either concurrent (same direction from end to end) or counter current (opposite general direction from end to end) See Figures 6A and 6B.

[0049] In some instances during operation hydrogen flows, counter current to the cathode side of the bipolar plate fluid flows, into the flow field from inlet 325 and generally moves diagonally across the flow field towards the outlet 315 along the line of arrow 500. The single hydrogen inlet diagonal from the single hydrogen outlet encourages flow of hydrogen through the flow field with less lower activity regions and fewer or no dead zones wherein in sufficient hydrogen is provided to the MEA. Dead zones and low efficiency regions starved of hydrogen during operation reduce the power density of the fuel cell. By reducing and eliminating such less-than-optimal conditions within the anode flow field the fuel cell can operate at higher efficiency i.e., producing electricity during peak performance at or near the voltage maximum for the fuel cell. The other instances hydrogen flows concurrent or in the same direction as the fluid flow on the cathode side of the bipolar plate.

[0050] Figure 4A shows aspects of the unassembled cathode side of a bipolar frame 13. The cathode outlet cover 20 attaches to the bipolar frame at its first end 18 aligning with the water inlet, air inlet 300 and hydrogen outlet 315 of the bipolar frame. A first cathode fluid passage 340 is formed at one edge of the cathode inlet cover 22. A separate cathode inlet cover 22 attached to the bipolar frame at its second end 19 aligning the cathode inlet 300 and hydrogen outlet of the bipolar frame. A second cathode fluid passage 345 is formed at one edge of the cathode outlet cover 20. Once the cathode covers are attached the bipolar plate is formed. Those of ordinary skill in the art and the skilled artisan will recognize that traditional bipolar plates utilizing multiple frames affixed together and bipolar plates with asingle frame and no covers are within the scope of this disclosure. Optionally a separate water guide 30 or distribution means such as a separate water distribution cover is configured to affix over at least a portion of the cathode inlet cover. 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.

[0051] Figure 4B shows aspects of the assembled cathode side of a bipolar plate 200B including optional water distribution cover.

[0052] Figure 5 shows aspects of an assembled bipolar plate cathode face up with cathode gas diffusion layer 15 visible. Fluid 510 containing the air, water and water vapor from the air inlet 300 and the water inlet 310 fluidly pass through the first cathode fluid passage 340 along the lines of arrow 510 through the cathode face 14 and the cathode gas diffusion layer 15 to the second cathode fluid passage 345 then to the cathode fluid (or exhaust) outlet 320. The location of the water and air inlets and outlets can be reversed depending on whether the bipolar plate is running concurrent or counter current flows.

[0053] Figure 6 shows an assembly view 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 605 is also in fluid communication with the cathode fluid outlet.

[0054] Figures 6A and 6B 3 shows aspects of a bipolar plate. The anode side is up and along the cathode side the fluid flows 510 are shown as dotted lines.

[0055] In the concurrent or co-flow operation or system there is an inlet end 525 whereby all fluid inlets for both the anode side and the cathode side are positioned and an outlet end 535 whereby all of the fluid outlets are positioned. Similar to the descriptions above, the fluid flow for hydrogen 500 is preferred to be urged from diagonal comer inlet 527 to diagonal comer hydrogen fluid outlet 537. Fluid flow for air and water travel inlet end 525 to outlet end 535 in a generally linear path as shown by fluid direction flow arrows 510.

[0056] In the opposing operation or system there is an inlet end 525 whereby fluid inlets for the cathode side fluids (air and water for example) travel across the plate as illustrated by fluid direction flow arrows 510 to the outlet end 535. However, as described above, hydrogen fluid inlet 527 is located at a comer region on the fluid outlet end 535.Similarly, the hydrogen fluid outlet 537 is located on a comer diagonal from the hydrogen inlet on the inlet end 525.

[0057] The stack illustrated in Figure 7 shows that the cathode air inlet and outlet cathode fluid manifolds between fuel cells 10 (1-N) are integrated into the fuel cell stack and eliminated from the exterior of the fuel cell stack. In some instance in the stack illustrated in Figure 6 the inlet and outlet manifolds for hydrogen between fuel cells 10 (1-N) are integrated into the fuel cell stack and eliminated from the exterior of the fuel cell stack. Exemplars show an air inlet manifold 300’ formed within the fuel cell stack 600 which are configured to fluidly connect to air inlets 300 of the bipolar plates 10 (1-N) whereby air (oxidant) is evenly dispersed from the air inlet manifold into the cathode flow fields of each fuel cell. Not shown is a compressor or pump directing the air into said air inlet manifold 300’. A cathode exhaust manifold 320’ is formed within the fuel cell stack which is configured to fluidly connect bipolar plates cathode fluid outlets 320 whereby cathode exhaust fluid (air, water and water vapor) is collected in the air outlet manifold.

[0058] Disclosed herein is a fuel cell formed from such bipolar plates as have been described, wherein there can be a single inlet for each of the hydrogen, air and water formed in the fuel cell assembly. There can also be but a single outlet for the air and water and a single outlet for hydrogen unspent in the operation of the fuel cell. By eliminating portions of the frame traditionally used to form multiple outlets in fuel cell assemblies and fuel cells manifolds for collecting and distributing fluids within the fuel cell stack can be formed thereby eliminating external manifolds and fluid pathways thereby reducing the footprint of the fuel cell stack.

[0059] During fuel cell operation the heat of the reaction heats the system, the heated system is cooled by water entering with air from the first side of the bipolar plate via the first cathode fluid passage and passing across the cathode flow field to the second cathode fluid passage and out the cathode outlet at the second end. During the passage across the flow field water vapor is formed, and the air is heated causing a volumetric expansion of fluid. Traditional fuel cells have inlets on one side of the bipolar plate which are the same size as the outlets on the other side of the bipolar plate. The size matching causes restriction in flow of fluid which is further exacerbated by uneven pressure down the length of the fuel cell stack in the cathode exhaust collection region.

[0060] In the instant disclosure the cathode fluid outlet 320 area is proportionately larger than the combined cathode air inlet 300 and the water inlet 310 area. This size differential accommodates the absolute flow with higher volumetric flow. When we compare a traditional multiple cathode air and water inlet fuel cell also having multiple cathode fluid outlet with the fuel cell disclosed herein, we determined that the traditional arrangement had a fluid flow rate of 10856 standard litres per min versus the disclosed fuel cell having a fluid flow rate of 12406 standard litres per min, or about a 13.5% increase in flow rate. In practice, if the volume of the fuel cell power system was a non-factor , for example stationary power systems. The cathode outlet area would be increased by one of at least 1.8 times the inlet, at least 1.85 times the inlet, at least 1.9 times the inlet , at least 1.95 times the inlet, and at least 2.0 times the inlet . In the disclosed configuration which is also suitable for mobile applications a modest increase in cathode outlet area compared to cathode inlets of at least one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, and 29%, is disclosed. In other instances an increase in cathode outlet area compared to cathode inlets of at least one of at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, may be suitable depending on the space limitations. Those of ordinary skill in the art and the skilled artisan will recognize that the above variations which encompass the increased outlet size to accommodate the increased volumetric flow of the heated cathode fluids to limit bottlenecks are within the scope of this disclosure.

[0061] In a traditional fuel cell stack design with multiple cathode fluid inlet and multiple cathode fluid outlet ports each inlet and outlet of the same total area pressure drop in the stack occurs during operation. There is a higher-pressure bias (for cathode outlet fluids) in the fuel cells in the stack nearest the external manifold fluid connection which have a higher volume flow rate than those fuel cells more remote from the manifold fluid connection thus creating differences in each fuel cells based on position in the stack which reduce overall performance. Further traditionally additional energy must be expended to increase the force at the compressor used to input air (oxidant) into the fuel cell cathode air inlets of a fuel cell stack to ameliorate the aforementioned bias.

[0062] In the instant disclosure the single cathode fluid outlet 320 with an area both larger than the cathode inlet area and forming the manifold which each fuel cell outlet feeds into in an unrestricted fashion at least one of reduces and eliminates the biasing. The instantdisclosure, in some instances also at least one of eliminates and reduces parasitic losses caused by the increased energy used at the compressor for air input to the cathode air inlet.

[0063] Disclosed herein are aspects of a more compact fuel cell assembly formed into a more compact fuel cell which are stacked in groups to form a more compact fuel cell stack. The more compact fuel cell stack measured as power density per total system volume is denser in power than a traditional fuel cell stack constructed of fuel cells with multiple cathode side inlets and outlets and external manifolds.

[0064] 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 drones. In some aspects, the systems disclosed herein can be used in automotive, rail or aerospace applications, such as in cars, trucks, trains, airplanes or in stationary power system. 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.

[0065] The components disclosed herein may utilize known materials that are used in the industry.

[0066] 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.

[0067] 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 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.

[0068] Features of the disclosure that are described above in the context of separate embodiments may be provided in combination in a single embodiment. Conversely, variousfeatures 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.

[0069] 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

What is claimed:

1. A high efficiency fuel cell assembly comprising; a bipolar frame (13) having a first end (18) and a second end (19) and having two faces, the first face configured as an anode flow field (16) and on an opposite side of the bipolar plate a cathode flow field (14); the first end includes; a single air inlet (300) or cathode fluid outlet (320), a single water inlet (310) or water outlet 325 and a single hydrogen outlet (315) or hydrogen inlet (325); the second end includes: a single cathode fluid outlet (320) or air inlet (300), and a single hydrogen inlet (325) or hydrogen outlet (315); wherein the air inlet and water inlet are fluidly connected to one of the cathode or anode flow field; wherein the cathode flow field is fluidly connected to the cathode flow field outlet (345) which is fluidly connected to the cathode fluid outlet; and, wherein the cathode outlet area is one of at least 20% larger than the cathode water inlet and air inlet area combined, at least 25% larger than the cathode water inlet and air inlet area combined, and at least 30% larger than the cathode water inlet and air inlet area combined.

2. The high efficiency fuel cell assembly of claim 1, further comprising: an anode gas diffusion layer in fluid communication with the anode flow field; a membrane electrode assembly (MEA) (12) in contact with the anode gas diffusion layer on its second side (12B); and, a cathode gas diffusion layer in contact with the first side of the MEA (12A).

3. The high efficiency fuel cell assembly of claim 2, further comprising: an anode gasket (40) to form a seal around the anode face of the bipolar frame when compressed into a fuel cell; and, a cathode gasket (42) to form a seal around the cathode face of the bipolar plate when compressed into a fuel cell.

4. The high efficiency fuel cell assembly of claim 3 further comprising: a cathode inlet cover (22) affixed at the first end of the bipolar frame; a cathode outlet cover (20) affixed over the second end of the bipolar frame; and, a water guide (30) affixed to at least a portion of at least one of the first end and the cathode inlet cover.

5. The high efficiency fuel cell assembly of claim 1 wherein the fluid flow on the cathode and the anode sides of bipolar plate is concurrent in the same direction.

6. The high efficiency fuel cell assembly of claim 1 wherein the fluid flow on the cathode and the anode sides of bipolar plate is counter current in the opposite direction.

7. A high efficiency fuel cell comprising; a first bipolar plate (200A) comprising; a cathode (14) flow field on a first face; an anode flow field on its second face (16); a first end (18); and a second end (19); a second bipolar plate (200A) comprising; a cathode (14) flow field on a first face; an anode flow field on its second face (16); a first end (18); and a second end (19); 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; a single air inlet (300), a single water inlet (310), and a hydrogen inlet (325);the second end of each bipolar plate includes: a single cathode fluid outlet (320), and a hydrogen outlet (315); wherein the air inlet and water inlet are fluidly connected to a cathode flow field via a cathode flow field inlet (340); wherein the cathode flow field is fluidly connected to the cathode flow field outlet (345) which is fluidly connected to the cathode fluid outlet; and, wherein the cathode outlet area is one of at least 20% larger than the water inlet and air inlet area, at least 25% larger than the water inlet and air inlet area, and at least 30% larger than the water inlet and air inlet area.

8. The high efficiency fuel cell of claim 7, further comprising: 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.

9. A fuel cell stack comprising: a plurality of high efficiency fuel cells formed into a stack; an air inlet manifold formed within the fuel cell stack fluidly connected to the cathode flow field of each high efficiency fuel cell in the stack; and, a cathode exhaust manifold formed within the fuel cell stack fluidly connected to the cathode flow field of each high efficiency fuel cell in the stack.

10. The fuel cell stack of claim 9, wherein the fluid flow rate of standard liters per min through the cathode flow fields of the fuel cells comprising the stack is at least 13% greater than in a fuel cell stack with multiple cathode flow field air inlets and exhaust outlets.

11. A method of improving cathode fluid flow within a fuel cell stack the method comprising; placing a plurality of cells formed into a stack, each fuel cell comprising;bipolar plates having a cathode flow field on a first face, an anode flow field on a second face, a first end, and a second end; on the first end of each bipolar plate forming a single air inlet, a single water inlet; on the second end of each bipolar plate forming a single cathode fluid outlet; sandwiching a MEA between gas diffusion layer on each side; placing the MEA and gas diffusion layers between bipolar plates; 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, forming a cathode exhaust manifold within the fuel cell stack fluidly connected to the cathode flow field of each fuel cell in the stack.

12. The method of claim 11, wherein gaskets are placed between the bipolar plates to seal the bipolar plates whereby the cathode flow field and the anode flow fields are sealed and prevented from leaking.

13. The method of claim 12, wherein the cathode exhaust manifold has an area which is at least one of at least 20% larger than the air inlet manifold area, at least 25% larger than the air inlet manifold area, at least 30% larger than the air inlet manifold area.

14. The fuel cell stack of claim 12, wherein the fluid flow rate of standard liters per min through the cathode flow fields of the fuel cell stack is at least 13% greater than in a fuel cell stack with multiple cathode flow field air inlets and exhaust outlets.

15. The method of claim 12, wherein the cathode exhaust manifold has an area which is at least one of at least 50% larger than the air inlet manifold area, at least 60% larger than the air inlet manifold area, at least 70% larger than the air inlet manifold area.

16. The method of claim 12, wherein the cathode exhaust manifold has an area which is at least one of at least 80% larger than the air inlet manifold area, at least 90% larger than the air inlet manifold area, at least 100% larger than the air inlet manifold area.

17. A high efficiency fuel cell assembly comprising;a bipolar frame (13) having an inlet end (525) and an outlet end (535) and having two faces, the first face configured as an anode flow field and on an opposite side of the bipolar plate a cathode flow field; the inlet end includes; a single air inlet; a single water inlet; a hydrogen inlet (527); and, the outlet end includes: a cathode fluid outlet; a hydrogen outlet (537); wherein the air and water inlet are in fluid communication with the cathode flow field; wherein the hydrogen inlet and outlet are in fluid communication with the anode flow field; and, wherein the hydrogen inlet and hydrogen outlets are on diagonally opposing comers of the anode flow field.

18. The high efficiency fuel cell assembly of claim 17, wherein the cathode outlet area is one of at least 20% larger than the cathode water inlet and air inlet area combined, at least 25% larger than the cathode water inlet and air inlet area combined, and at least 30% larger than the cathode water inlet and air inlet area combined.

19. The high efficiency fuel cell assembly of claim 17, wherein the cathode and anode sides of the bipolar plate are reversed wherein the hydrogen flows across the cathode side and the air and water flow on the anode side.

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