Fluid pressure control in a fuel cell stack

Abstract

A fuel cell 1 includes an active layer having a membrane electrode assembly (MEA) between a second surface (254, Figure 7) of a first flow assembly (250, Figure 7) and a first surface (252, Figure 7)

Description

TECHNICAL FIELD

[0001] The present disclosure relates to outlet fluid pressure control in a fuel cell stack, and in particular to membrane-type fuel cells. BACKGROUND

[0002] Interest in fuel cell batteries as power sources for portable electronic devices has grown. A fuel cell is an electrochemical cell that uses materials from outside the cell as the active materials for the positive and negative electrode. Because a fuel cell does not have to contain all of the active materials used to generate electricity, the fuel cell can be made with a small volume relative to the amount of electrical energy produced compared to other types of batteries.

[0003] Fuel cells can be categorized according to the type of electrolyte used, typically one of five types: proton exchange membrane fuel cell (PEMFC), alkaline fuel cell (AFC), phosphoric-acid fuel cell (PAFC), solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC). Each of these types of fuel cell can use hydrogen and oxygen as the active materials of the fuel cell negative electrode (anode) and positive electrode (cathode), respectively. Hydrogen is oxidized at the negative electrode, and oxygen is reduced at the positive electrode. Ions pass through an electrically nonconductive, ion permeable separator and electrons pass through an external circuit to provide an electric current. In some types of hydrogen fuel cells, hydrogen is formed from a hydrogen-containing fuel supplied to the negative electrode side of the fuel cell. In other types of hydrogen fuel cells, hydrogen gas is supplied to the fuel cell from a source outside the fuel cell.

[0004] A group of fuel cells stacked to together and compressed between end plates is typically referred to as a fuel cell stack. Fuel cell systems have balance of plant components which may include a battery, a fuel source, such as a fuel tank or a hydrogen generator, pumps, compressors, controllers and the like.

[0005] Such fuel cells may include a proton exchange membrane (PEM) sandwiched between two porous electrodes, together comprising a membrane-electrode assembly (MEA). The MEA itself may be sandwiched between: (i) a cathode diffusion structure (such as a cathode gas diffusion layer) having a first face adjacent to the cathode face of the MEA and (ii) an anode diffusion structure (such as an anode gas diffusion layer) having a first face adjacent the anode face of the MEA. The second face of the anode diffusion structure may contact an anode fluid flow field plate for current collection and for distributing hydrogen to the second face of the anode diffusion structure. The second face of the cathode diffusion structure may contact a cathode fluid flow field plate for current collection, for distributing oxygen to the second face of the cathode diffusion structure, and for extracting excess water from the MEA. The anode and cathode fluid flow field plates may each include 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).

[0006] An important consideration in the operation of such fuel cells is the management of water within the MEA. 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 must be exhausted from 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.

[0007] In an evaporatively cooled fuel cells, water can be introduced via anode fluid flow paths into the fuel cell stack to hydrate the membrane and to cool the cells. In a typical fuel cell arrangement, the cooling water is injected into the anode or cathode face of a fuel cell and disperses. Uneven colling is suboptimal and may reduce efficiency. It is also important that pressure applied to the ends of the fuel cell stack is sufficiently uniform across the surfaces of the stack that all of the individual components of the stack are maintained in proper compressive relationship with one another. Sealing gaskets in particular must be maintained in proper compression across the entire area of each fuel cell to ensure that fluid flow paths are properly defined so that coolant, fuel and oxidant are correctly conveyed to the active surfaces of each cell and do not leak.

[0008] A problem in existing fuel cell technology is that when plates are press-formed, as explained above, they sometimes affect adjacent or nearby components, such as the membrane-electrode assembly (MEA), the gas diffusion layer (GDL), or another component in the fuel cell or the fuel cell stack. In some instances, when the desired or necessary pressure is applied to the fuel cell as described above, the identical press-formed plates stack, or nest, one into the other. Layers between the adjacent nesting plates get caught and are distorted into a corrugated shape to correspond with the shapes of the channels or characteristics of the flow plates. This leads to inconsistent distribution of components through the fuel cell, a decrease in efficiency and energy output, and physical damage to the layers.

[0009] A problem in existing fuel cell technology is that when plates are press-formed, they can adversely affect adjacent or nearby components, such as the membraneelectrode assembly (MEA), the gas diffusion layer (GDL), or another component in the fuel cell or the fuel cell stack. Referring to Figs. 1-3B there is show aspects of a traditional fuel cell stack 1 shown having a two end plates 2 and a plurality of prior art fluid flow plates 4 with gaskets placed there between (not visible) and compressed into a stack. The fluid flow plate 4 have a plurality of channels 5 that are arranged in a fixed pattern as indicated in figures. 2, 3A and 3B the patterns on each of the flow plates 4 are identical. Figures 3A and 3B are representations of section “A” of Fig. 2 before and after assembly compression. As seen from the side view in Fig. 3 A, the fluid flow plates 4 stack, or nest, into one another by virtue of the channels 5 lining up amongst the adjacent plates 4.

[0010] The flow plates 4 include at least one fuel cell component layer 6 disposed between adjacent fluid flow plates 4. The component layer may include a gas diffusion layer (GDL) 10 adjacent to at least one of an anode and a cathode 4, a membrane-electrode assembly (MEA) 20, or another layer component such as a gas diffusion layer. When assembled pressure is applied to the fuel cell orthogonally to the flow plates 4, the flow plates 4 get compressed towards one another. Because the channels 5 are in the same patterns in adjacent flow plates 4, the flow plates 4 are pushed one into another to further nest. This movement squeezes the one or more component layers 6 between the nesting flow plates 4. The compression deforms the component layers between the flow plates 4. As shown in Fig. 3B, the channels 5 of each plate bend portions of at least the GDL 10 as the plates 4 nest into one another, which applies undesirable shear stress forces on the layer. Such forces and deformation damage the layer. The layer gets physically damaged due to the shear deformation and often sustains tears or holes. The bending of the GDL will also interfere with consistent reactant conversion and proper functioning of the fuel cell because the GDL 10 will be placed out of contact with one of the MEA 20 as indicated by arrow 25 and fluid flow channel 5, resulting in incomplete, inefficient, or unpredictable operation of the fuel cell.

[0011] These problems are exacerbated when the necessary pressure is applied to the fuel cells to form a stack. Layers between the adjacent nesting plates get caught and are distorted to correspond with the shapes of the channels or characteristics of the flow plates. However, we have observed that in such arrangements, the use of identical sets of substantially parallel tracks or channels can lead to reduced performance of the fuel cell stack. Compression across the full surface of the membrane electrode assemblies can be inconsistent due to lack of rigidity through the stack which is under mechanical compression, leading to lateral instability, buckling or curvature of flow plates in a stack and / or the MEA and the GDL when placed under such pressures separate from the cathode or anode face which leads to inconsistent distribution of components through the fuel cell, a decrease in efficiency and energy output, and physical damage to the layers.

[0012] Additional problems in fuel cell assemblies include: ensuring a uniform flow field for fluid distribution in fuel, oxidant, and coolant lines; minimizing the pressure drop across inlet manifolds; minimizing the sealing pressure required to ensure gas-tight operation; making the construction of a fluid flow plate compatible with mechanized assembly processes, given the large number of units that need to be assembled with precision in manufacturing a fuel cell assembly; reducing the pitch of the fuel cells making up a stack while maintaining operation within desired parameters; reducing the number of components: reducing the overall weight; reducing material usage and wastage; simplifying the design, manufacture and assembly; and in general reducing the overall cost of a fuel cell assembly.

[0013] A challenge in high efficiency PEMFCs is heat generation and removal or management of same from the fuel cell stack because the stack produces an amount of heat similar to the electric power output. Consequently, if a fuel cell has a power of 100 kW, then the heat dissipation rate is nearly 100 kW, and that heat must be resolved or efficiencies will suffer. Heat generation in PEMFCs occurs due to at least the reversible heat of electrochemical reactions (also called entropic heat), (2) irreversibility of reactions, (3) ohmic resistance, and (4) heat from water vapor condensation. To keep a constant temperature while the current is flowing, the heat must be reduced or be taken away. It is therefore a desideratum to provide for compression of fluid flow plates in a fuel cell and / or flow assembly which address the problems and inefficiency of the prior. DISCLOSURE

[0014] The following are a 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.

[0015] Disclosed are exemplary implementations of aspects of utilizing press-formed fluid flow plates that can be compressed to the necessary pressure but that will not nest one into the other and will distribute forces evenly over the component layers between the plates without applying unnecessary shear forces or damaging the component layers.

[0016] The foregoing needs are met by various aspects of fluid flow plates and fuel cells disclosed.

[0017] Disclosed are exemplary implementations of aspects of controlling fluid pressure differentials which are caused by the variation of heat and humidity in fluid in a fuel cell from inlet manifold through outlet manifold of the fuel cells forming a stack.

[0018] Disclosed are exemplary implementations of aspects of systems and methods of a fuel cell and fuel cells forming fuel cell stacks. Aspects of the fuel cells include a first flow assembly having a first surface and a second surface which comprise a first frame including a first fluid flow plate having a first face and a second face. The fluid flow plate configured with a plurality of fluid flow channels having inlets and outlets. A pressure control passage is in fluid communication with the outlets. An active reduction zone with the flow reduction elements is configured to reduce the cross-sectional area in the pressure control passage. A second flow assembly is included and an active layer having at least a membrane electrode assembly (MEA) therein between the second surface of the first fluid flow assembly and the first surface of the second flow assembly; and, the fuel is supplied via galleries to one side of the MEA and oxidant is supplied via galleries to the other side of the MEA. In some instance the pressure control passage further comprising an active reduction zone.

[0019] Disclosed are exemplary implementations of aspects of systems and methods of a fuel cell and fuel cells forming fuel cell stacks. Aspects of the fuel cells include two flow assemblies each having a first surface and a second surface which comprise a first frame including a first fluid flow plate having a first face and a second face. The fluid flow plate configured with a plurality of fluid flow channels having inlets and outlets. A pressure control passage is in fluid communication with the outlets. An active reduction zone with the flow reduction elements is configured to reduce the cross-sectional area in the pressure control passage. A membrane electrode assembly (MEA) is placed between the two assemblies; and, the fuel is supplied via galleries to one side of the MEA and oxidant is supplied via galleries to the other side of the MEA. In some instance the flow reduction elements are at least one of columns, dimples bumps and projections. In some instances the flow reduction elements do not fill the passage from a first side to the second side. In some instances one or more flow reduction elements fill the passage from a first side to the second side. A plurality of fuel cells are configured to stack together to form a fuel cell stack with common fluid inlet manifold and common fluid outlet manifold. In some instances the at least one of the flow reduction elements is configured to provide at least some structural support to reduce collapse of the passage when fuel cells are compressed into a stack.

[0020] In the fuel cell stack, in some instances, the reduction of the cross-sectional area in the pressure control passage via the density of restricting elements is the same for each fuel cell in a stack. The reduced cross section of each fuel cell passage is a predetermined volume to reduce variation in the pressure drop across the fuel cells in the stack.

[0021] In the fuel cell stack, in some instances, the reduction of the cross-sectional area in the pressure control passage via the density of restricting elements is different for each fuel cell in a stack. In such a stack the different reduced cross section in each fuel cell optimizes the performance of each fuel cell in the stack.

[0022] In the fuel cell stack, in some instances, a plurality of fuel cells are formed into modules; each module is configured with the same density of restricting elements; each module has a different density then the other modules; and, the fuel cell stack is formed of the modules.

[0023] Disclosed are exemplary implementations of aspects of systems and methods of controlling pressure drop in an evaporatively fuel cell stack. The stack is formed from a plurality of fuel cells, and each fuel cell comprises at least an MEA between two GDLs forming an active layer; the active layer is placed between a first fluid flow plate having fluid flow channels each of which has inlets and outlets in a first flow assembly and a second fluid flow plate having fluid flow channels each of which has inlets and outlets in a second flow assembly. Each fuel cell has a pressure control passage in fluid communication with each outlet. The fuel cell may have an active reduction zone with the flow reduction elements configured to reduce the cross-sectional area in the pressure control passage; The fuel cells are configured to stack and form a common inlet manifold fluidly connecting the inlets of each fuel cell; The fuel cells are configured to stack and form a common outlet manifold fluidly connected to the pressure control passage of each fuel cell; the fuel cells are compressed into a fuel cell stack. In some instances the pressure control passage further comprising an active reduction zone. In some instances the flow reduction elements are at least one of columns, dimples, bumps and projections compressed.

[0024] Disclosed are exemplary implementations of aspects of systems and methods of controlling pressure drop in an evaporatively fuel cell stack. The stack is formed from a plurality of fuel cells, and each fuel cell comprises at least a MEA between two GDLs forming an active layer; the active layer is placed between a first fluid flow plate having fluid flow channels each of which has inlets and outlets in a first flow assembly and a second fluid flow plate having fluid flow channels each of which has inlets and outlets in a second flow assembly. Each fuel cell has a pressure control passage in fluid communication with each outlet. The fuel cell may have an active reduction zone with the flow reduction elements configured to reduce the cross-sectional area in the pressure control passage; The fuel cells are configured to stack and form a common inlet manifold fluidly connecting the inlets of each fuel cell; The fuel cells are configured to stack and form a common outlet manifold fluidly connected to the pressure control passage of each fuel cell; the fuel cells are compressed into a fuel cell stack. In some instances at least one of the flow reduction elements is configured to provide at least some structural support to reduce collapse of the passage when fuel cells stack is compressed.

[0025] In some instances the reduction of the cross sectional area in the pressure control passage via the density of restricting elements is the same for each fuel cell in the stack. In some instances the reduced cross section of each fuel cell passage is a predetermined volume to reduce variation in the pressure drop across the fuel cells in the stack. In some instances the reduction of the cross sectional area in the pressure control passage via the density of restricting elements is different for each fuel cell in a stack. In some instances the fuel cell stack contains a plurality of modules and each module contains a plurality of fuel cells each fuel cell in a module is configured with the same density of restricting elements and each module has a different density then the other modules.

[0026] In some instances the reduction of the cross sectional area in the pressure control passage via the density of restricting elements is the same for each fuel cell in the stack. In some instances the reduced cross section of each fuel cell passage is a predetermined volume to reduce variation in the pressure drop across the fuel cells in the stack. In some instances the reduction of the cross sectional area in the pressure control passage via the density of restricting elements is different for each fuel cell in a stack. In some instances the fuel cell stack contains a plurality of modules and each module contains a plurality of fuel cells each fuel cell in a module is configured with the same density of restricting elements and each module has a different density then the other modules.

[0027] Disclosed are exemplary implementations of aspects of systems and methods of cooling a fuel cell including a first flow assembly having a first surface and a second surface configured with a first frame including a first fluid flow plate having a first face and a second face and the fluid flow plate configured with a plurality of fluid flow channels having inlets and outlets and a water plate affixed to at least one of the first and second frame in fluid connection with the inlets. The cooling method and system including a second flow assembly wherein fuel is supplied via galleries to one side of the MEA and oxidant is supplied via galleries to the other side of the MEA; and, wherein water is supplied via a water plate to at least one side of the MEA.

[0028] In some instances the water plate is configured with a coolant gallery formed between the frames and a coolant transport main formed as part of the water plate and is in fluid communication with the coolant gallery.

[0029] A plurality of rivulets are fluidly connected at rivulet inlets to the transport main at interfaces and each rivulet has an outlet wherein the rivulet outlets are open and configured to supply coolant to the adjacent fluid flow plate.

[0030] In some instances there are mixing inlets on the fluid flow plate aligned with rivulet outlets. In some instances supporting structures in the flow assemblies reduce collapse or deformation of galleries. In some instances a plurality of said fuel cells are compressed and affixed into a fuel cell stack. In some instances gas diffusion layers (GDL) are placed on either side of the MEA.

[0031] In some instances the second flow assembly is offset by 180 degrees from the first flow plate and the assembled fuel cell the serpentine fluid flow channels of the first flow assembly and the second flow assembly are offset by 180 degrees; and, the offset fluid flow channels are configured to impinge upon one another at a plurality of areas thereby preventing nesting of the fluid flow channels in the first and second flow assemblies. The MEA, is in some exemplars, sandwiched between two gas diffusion layers (GDL).

[0032] The aforementioned impingement points are configured to at least one to reduce the shear forces on at least one of the MEA and GDL and reduce the ohmic resistance across the MEA during operation. FIGURES

[0033] 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.

[0034] 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.

[0035] Fig. 1 depicts a traditional fuel cell stack;

[0036] Fig. 2 depicts an isometric perspective view of a portion of a traditional arrangement of nested fluid flow plates;

[0037] Figs. 3 A and 3B depicts a side view of a section “A” of the traditional arrangement of nested fluid flow plates depicted in Fig. 2 before and after assembly compression;

[0038] Fig. 4 depicts a simplified diagrammatic overview of novel and non-obvious arrangement of three fluid flow plates with the center plate turned 180 degrees illustrating aspects of a non-nesting arrangement;

[0039] Figs. 5A and 5B depict a side elevation view of channels in a portion of three non-nesting fluid flow plates before and after assembly compression according to an aspect of this disclosure;

[0040] Fig. 6A illustrates a simplified diagram of the first frame of a flow assembly cathode side up;

[0041] Fig. 6B illustrates a simplified diagram of the first frame of a flow assembly anode side up;

[0042] Fig. 6C illustrates a simplified diagram of the second frame of a flow assembly first side up;

[0043] Fig. 6D illustrates a simplified diagram of the second frame of a flow assembly second side up;

[0044] Fig. 6E illustrates a simplified diagram of a water plate of a flow assembly;

[0045] Fig. 6F illustrates aspects of the plates formed into an assembly;

[0046] Fig. 7 illustrates a cut-away assembly view of two fuel cells from three flow assemblies;

[0047] Fig. 8A depicts three identical fluid flow plates and the middle plate is rotated 180 degrees from the top plate;

[0048] Figs. 8B-8D depict a sequential perspective cut-away views of the three stacked plates shown in Figure 8A along the line “A - A” to “C - C” at section “A” illustrating aspects of positioning of channels in the non-nested plates;

[0049] Fig. 9A illustrates an exploded view of a flow assembly;

[0050] Fig. 9B illustrates a partial top view of a first flow assembly frame cathode side up with fluid flow plate and galleries;

[0051] Fig. 9C illustrates a partial top view of a second flow assembly frame;

[0052] Fig. 9D illustrates a partial top view of a water frame or plate;

[0053] Fig. 9E illustrates oxidant fluid flow galleries between the first and second frames of a flow assembly;

[0054] Fig. 9F illustrates fuel fluid flow galleries between the first and second frames of a flow assembly;

[0055] Fig. 9G illustrates fuel fluid flow galleries and gaskets between the first and second frames of a flow assembly and the active layer; and, Fig. 9H illustrates supporting and sealing gaskets separate the plates and surrounding galleries;

[0056] Fig. 91 and 9J illustrates features of the water plate and water distribution to the cathode;

[0057] Fig. 9K illustrates features of outlet fluid pathway;

[0058] Fig. 10A illustrates a portion of assembled set of frames;

[0059] Fig. 10B illustrates the water galleries through the frames and the water plate; and

[0060] 11 A-l IE illustrate exemplars of control devices and methods of pressure drop across an array of fuel cells within a stack.

[0061] 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

[0062] 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.

[0063] 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, improve structural integrity, reduce damage to active layers of a fuel cell, reduce ohmic losses, reduce ohmic resistance, and reduce cost of production.

[0064] Figure 4 depicts a simplified diagrammatic overview of three fluid flow plates 100 each having a serpentine shaped fluid flow channel 105 flow channel at the midsection and with the center plate reversed illustrating aspects of a non-nesting arrangement. Each fluid flow plate 100 has a first face 102A and a second face 102B (see Fig 5A). In this simplified illustration a single serpentine fluid flow channel 105 is shown. The channel 105 is formed in the center of the plate it has an inlet 106 and in outlet 107. In this illustration the middle plate is rotated 180 degrees and each plate is shown anode side up. The rotation of the plate offsets the serpentine fluid flow channel by 180 degrees to provide the stacking configured as non-nesting function which is depicted in Figure 5A and 5B.

[0065] The fluid flow plates form flow assemblies which when combined with a membrane electrode assembly “MEA” form fuel cells. Each fluid flow plate is at least conductive and impermeable to hydrogen. The conductivity may be the result of adding one or more coatings over a non-conductive base material. Each fluid flow plate has an anode surface and a cathode surface when combined into a fuel cell. For simplicity and not as a limitation the first face 102A is designated herein as the anode face and the second face 102B is designated herein as the cathode side.

[0066] Figs. 5A and 5B depict a side elevation view of a portion of three non-nested fluid flow plates 100 -100” before and after assembly compression according to an aspect of this disclosure. A sandwich of active layers 140 contains a membrane electrode assembly (MEA) with a gas diffusion layer (GDL) on either side to form the active element of a fuel cell assembly. Those of ordinary skill in the art (or the skilled artisan) will recognize the active layer can in some instances extend beyond the boundary of the flow plate and still be within the scope of this disclosure. On one side of a first membrane electrode assembly (MEA) 150 there is a cathode gas diffusion layer (GDL) 160 sandwiched between the second side 102B of the first fluid flow plate 100. On the opposite side of the first MEA 150 there is an anode gas diffusion layer (GDL) 170 sandwiched between it and a second side 102B of a second fluid flow plate 100’ fluid flow plate. On one side of a second MEA 150’ there is a cathode GDL 160 sandwiched between the first side 102A of the second fluid flow plate 100’. On the opposite side of the second MEA 150’ there is an anode GDL 170 sandwiched between it and a first side 102A of the third fluid flow plate 100”. The fluid flow channels, as shown in Fig. 5B have as series of ceiling 106 each having a top and tracks each having a floor 108. Walls 109 on either side of each floor or ceiling connect the floors to ceilings. The serpentine channel is formed as a positive and negative image extending positively from one side and indenting negatively on the other side of the fluid flow plate.

[0067] When the MEA, GDLs and fluid flow plates are assembled or formed into a fuel cell or fuel cell stack and compressed, the non-nesting fluid flow channels 105 are formed between a portion of each side of a fluid flow plate and one side of the MEA and the GDL sandwiched therebetween. In a stacked configuration three plates form two fuel cells.

[0068] It will be appreciated that the skilled artisan or one of ordinary skill in the art will understand that more fluid flow plates may be present in the fuel cell stack, for example, 3, 4, 5, 6, 7, 8, or another suitable number. It will be understood that fuel cells stack may have any suitable number of fluid flow plates.

[0069] The non-nesting configuration limits, reduce and / or prevents the bending or movement of a GDL (160 / 170) away from an MEA. In some instances the non-nesting configuration acts to prevent the bending or movement of either GDL (160 / 170) into a channel 150. In some instances non-nesting configuration prevents the bending or movement of a GDL (160 / 170) away from an MEA and to prevent the bending or movement of either GDL (160 / 170) into a channel 150. In some instances non-nesting configuration is configured to reduce stress on the MEA and / or GDL including but not limited to breakage and pinholes. By maintaining consistent contact between the GDL and MEA the gas diffusion across the anode or cathode is distributed evenly thereby supporting consistent function of the fuel cell plate and / or fuel cell stack. In some instances by maintaining a consistent contact between the GDL and MEA ohmic resistance is reduce thereby supporting more efficient operation of the fuel cell and / or fuel cell stack as compared to a fuel cell or fuel cell stack having prior art nested plates (see Figures 3 A and 3B).

[0070] The non-nesting configuration disclosed herein reduces deformation which can lead to lower mean and maximum stresses on the membrane electrode assembly, which is undesirable because the membrane electrode assemblies require a threshold amount of contact pressure to avoid pin-holing, as a result of swell / shrink cycles typically occurring in real world operation, and to provide for electrical contact. Electrical performance can be improved by providing higher and more consistent contact pressure across the surface of the membrane electrode assemblies. Further, a factor in the lifetimes of membrane electrode assemblies is the creation of stress concentrations or localized stresses. As described above the elimination of the distortions of the gas diffusion layer (GDL) and / or the MEA reduces breakage and damage. The elimination of the distortions of the gas diffusion layer (GDL) and / or the MEA via the non-nesting plates allows for even compression during assembly and even compression for consistent performance of the fuel cells. High and / or even compression reduces ohmic losses across each fluid flow plate. By rotating the orientation of the same plate with a serpentine flow field thereon to achieve a non-nesting orientation a single plate design is required thereby eliminating multiple parts yet achieving even compression, reducing ohmic losses and / or and reducing damage and breakage.

[0071] The fuel cells and stacks may be provided with cathode fluid, anode fluid, and coolant fluid inputs via galleries forming a flow control within the frames forming a flow assembly surrounding the fluid flow plates. The flow assembly provides the desired flow rates for each fluid for optimal operation. Exhaust flows can be collected from outlet manifolds via anode outlets and cathode outlets, and water content in the exhaust flows can be captured and reused in further operation for cooling or hydrating the fuel cell and / or fuel cell stack.

[0072] Those of ordinary skill in the art will appreciate that a variety of materials can be used in the manufacturing of the components in the devices and systems disclosed herein. Any suitable structure and / or material can be used for the various features described herein, and a skilled artisan will be able to select appropriate structures and materials based on various considerations, including the intended use of the systems disclosed herein, the intended arena within which they will be used, and the equipment and / or accessories with which they are intended to be used, among other considerations. Conventional polymeric, metal-polymer composites, ceramics, and metal materials are suitable for use in the various components. Materials hereinafter discovered and / or developed that are determined to be suitable for use in the features and elements described herein would also be considered acceptable.

[0073] Referring now to figures 6A-6F which show aspects of simplified flow assemblies. Figures 6A &6B show a fluid flow plate 100 formed as part of a first frame 200A and the view is cathode side 202 up. Figure 6B shows a fluid flow plate 100 formed as part of a first frame 200A and the view is anode side 204 up. Two exemplary serpentine or oscillating fluid pathways 180 and 180’ are illustrated. One or more fluid gallery region 230 are formed near the outlets and the inlets the galleries are zones that may be formed into manifolds or fluid flow paths and contain spacing / supporting structures 231 also referred to as bumps, protrusion or projections and which may be ovoid, circular or elongated. The supporting structures 231 are configured, in some instances, to at least one of direct fluid flow, allow for a predetermine volume of fluid flow, support the shape / integrity of the manifolds or fluid pathways when the flow assembly are compressed during assembly into fuel cells. The support includes but is not limited to supporting the flow gallery, fluid path or manifold when gaskets and active layers (not shown here) are added before the compression of assembly.

[0074] Figure 6C shows a second frame 200B first side 205 up. Figure 6D shows the second side 207 of the second frame 200B. The second frame is affixed to the first frame cathode side 202 up with the second frame configured first side 205 up. Figure 6E illustrates a water management plate or frame 300 which during assembly is affixed to the second frame. Some aspects of assembled frames and other components are shown in Figure 6F as a simplified flow assembly 250 viewed from cathode side up.

[0075] The flow assembly directs and collects oxidant, fuel and by products to and from the fluid flow plate via the active layer. In some instances the region of the active layer which is the area above the serpentine channels including at least a portion of the MEA may be referred to as the active region of the active layer. The serpentine channels 180 / 180’ have fuel channel inlets 182 and fuel channel outlets 185 which are fluidly connected to a fuel via the galleries. In the novel arrangement the oscillating fluid pathways 180 and 180’ are formed outlet to outlet 185 A to 185B. A serpentine channel has two or more bends 188 to create parallel paths of channels spanning the fluid flow plate and in general forming an active area of the fluid flow plate. In a fuel cell and a fuel cell stack inlet manifolds 232 and outlet or manifolds 234 are connected to the gallery regions to provide fuel, coolant and oxidant, and remove exhaust and byproducts. The skilled artisan will recognize that gaskets (not shown) are interspaced to cooperate with the galleries and manifolds to segregate fluid and direct flow as well as even out the compression on each flow assembly when formed into fuel cells and a fuel cell stack. Figure 6G is an exemplary of an inlet to outlet arrangement of flow channels. Unlike the novel outlet to outlet arrangement shown in Fig. 6F this illustration shows the serpentine or oscillating channels in a traditional position wherein an inlet leg 187 of the channel is adjacent to an outlet leg 189 of another channel. The outlet to inlet configuration allows fuel migration along the line of arrows 388 from the inlet leg to an outlet leg. The loss of inlet fuel which via the migration 388 bypasses the circuitous serpentine pathway has multiple negative impacts on the fuel cell. The loss will reduce even distribution of fuel throughout the GDL and over the active layer and that unevenness translates to uneven and / or reduced performance of the fuel cell and fuel cell stack. The novel outlet to outlet arrangement disclosed herein does not impact such distribution as the outlet legs are adjacent to one another and only fuel that is on the outlet leg can jump to another outlet leg.

[0076] Placing the first and second outlets 185A and 185B adjacent to one another prevents migration of outlet fluid into an upstream portion of the adjacent channel or from migration of fluid from an upstream portion of the channel avoiding the circuitous pathway to the outlet and directly into a downstream portion of the adjacent channel. Such migration reduce the distribution of fluid and compromises efficiency of part of the fuel cell which does not receive the fluid along the entirety of the pathway.

[0077] Figure 7 shows a cut-away assembly view of two fuel cells from three flow assemblies 250 having serpentine channels. The illustration shows aspects of the disclosure and are simplified. Each flow assembly has a first surface 252 and a second surface 254. The fluid flow plate 100’ in the middle flow assembly is rotated 180 degrees in plane. Each active layer may have the MEA attached or affixed to active layer gaskets 145. Main gasket 255 are placed between the flow assemblies have the MEA . The depiction of gaskets in the figure is not meant to be a limitation but rather an exemplar of some aspects and the gasket concept to seal the flow assemblies against one another when forming a fuel cell. Figure 8A illustrates aspects of three simplified fuel cell fluid flow plates 100. Between each plate is a sandwich of active layers 140, the middle plate is identical to the top and bottom plates but has been physically rotated 180 degrees before assembly into the first frame whereby the channels on each plate are place in a non-nesting position. Figures 8B-8D are a series of sequential views along lines A-C respectively within section “A” of Figure 8 A, all plates are cathode side up. The plates are designated 100 A, 100B and 100C for ease of reference with 100A being the first plate, 100B being the second plate and 100C being the third plate. The fluid flow plates are identical but for the middle one being rotated 180 degrees in assembly. The active layers are held firmly by the alternating channels and nesting is prevented by the 180 degree rotation of the fluid flow plate in the middle (100B) but for the ceiling 106 and floor 108 impingements between fluid flow plates on alternating flow assemblies The flow assemblies are oriented such that the pattern or arrangement of fluid flow on one a cathode face (of one plate) and of the anode face (of the other plate) do not match the pattern or arrangement and therefore do not nest. The ceiling 106 of the middle plate 100B along line “A” is oriented above the floor 108 of the first plate 100 A. Because of the rotation of the middle fluid flow plate 180 degrees the first - third plates do not nest, and at line “B” the ceiling of the middle plate is now about halfway under the floor 108 of the first plate. At line “C” the floor and ceiling alignment is restored. This dual oscillation of fluid flow channels maximizes the impingement point or points of compression on the active layers and prevents nesting thereby reducing ohmic resistance in a compressed stack of plates forming a fuel cell stack. In some instances impingements are between 11% and 13% of the active layer. In some instances impingements are between 12% and 13% of the active layer. In some instances impingements are between 13% and 15% of the active layer. It is preferred that impingements are greater than 15% of the active layer. Impingements are between 10 %and 13% For flow fields configured with repeat pathways having a wavelength of 13mm and oscillation amplitude of 0.63mm maintain even compression and sufficient impingement to improve MEA efficiency. The disclosure of this configuration is not a limitation and the skilled artisan will recognize it is but one of many examples the disclosure teaches.

[0078] The disclosure of this configuration is not a limitation and the skilled artisan will recognize it is but one of many examples the disclosure teaches.

[0079] In some aspects, the distribution of the impingement regions may be substantially even and uniform along the entire surface, or, in other aspects, the impingement regions may be distributed along a particular gradient, such that one side of the fuel cell has more impingement regions than another side thereof.

[0080] The distribution of the impingement regions allows for more uniform distribution of forces when the flow assemblies are compressed during assembly of the fuel cell stack. The impingement points are configured to reduce distortions and disfigurement of the fluid flow plates, and flow assemblies when compressed into a fuel cell stack.

[0081] In some aspects, the impingement regions may add up to between 1% and 30% of the total area of the active layers. In some aspects, this impingement area may be between 4% and 21% of the active layers.

[0082] It will be appreciated that the pattern may be zig-zag (linear), cosinusoidal, or another shape, and this disclosure is not limited by the particular shape of the pattern of the fluid flow channel rather by the non-nesting. It will be understood that sinusoidal wave frequency may have any suitable number of cycles across the active layer or active region of the fluid flow plates and that multiple fuel cells can be included in a single fuel cell stack (not shown).

[0083] Each fluid flow channel is defined by the series of ceilings 106, floors 108 and walls 109. Although the floors and ceilings are depicted in the figures as the same dimensions that is not a limitation and the skilled artisan will recognize that such dimensions may be altered without departing from the scope of the disclosure. The walls 109 are depicted as having a predetermined angle and are not shown as perpendicular to the floor or ceiling. The depiction is not a limitation the perpendicularity or lack thereof is not a limitation, and the wall may in some instances vary in the angle it is offset from perpendicular and the variation may be constant or varied at different points along the fluid flow channels.

[0084] Each fluid flow channel 180 and 180’ bends 188 one or more times, such that at least a portion of the channel runs parallel to another portion of the same channel. In some aspects, each channel may have 1, 2, 3, ... 10, or another suitable number of respective bends and parallel portions. Thus, the fuel cell formed from the stacking of non-nesting flow assembles as disclosed herein do not nest into one another, thus avoiding deforming and damaging the active layers 140 disposed therebetween.

[0085] The distribution of the impingement regions allows for more uniform distribution of forces when the flow assemblies are compressed during assembly of the fuel cell stack.

[0086] The fuel cell and flow plate assembly also include one or more water galleries 301 configured to receive water (or another coolant) and to fluidly communicate the water across the flow assembly along the fluid flow plates. It will be understood that, although exemplary aspects of this disclosure refer to water, other coolants may be used.

[0087] The distribution of the impingement regions allows for more uniform distribution of forces when the flow assemblies are compressed during assembly of the fuel cell stack. The impingement points are configured to reduce distortions and disfigurement of the fluid flow plates, and flow assemblies when compressed into a fuel cell stack.

[0088] Figure 9A illustrates an exploded view of aspects of another flow assembly with a fluid flow plate 100 within a first frame 200A having cathode side 202 up which is affixed irreversibly (or formed) to the first frame. Figures 9A-9G illustrate further aspects of exemplary implementations of the disclosure. The second frame 200B is affixed to the first frame. In some implementations, the fuel cells described herein may be used in an evaporatively cooled (EC) fuel cell operation. Methods of operating EC fuel cells are described more fully in U.S. Patent Pre-Grant Publication US2015 / 0236361 Al, entitled "Coolant fluid feed to fuel cell stacks, and International Patent Publication WO2016 / 034853A1, entitled "Fuel cell system," and International Patent Publication WO2015 / 140529A1, entitled "Fuel cell stack," the entireties of which are incorporated herein for all purposes.

[0089] Oxidant is provided to the fuel cell cathode air inlet manifold 402 and exits the fuel cell via cathode outlet manifolds 403. Fuel enters the fuel cell via fuel inlet manifolds 404 and exits the fuel cell via fuel outlet manifolds 405. Water enters the fuel cell via water inlet manifolds 406 and exist the fuel cell via water outlet manifolds 407.

[0090] When configured for an EC environment a water plate 300 for directing the movement of water for cooling and humidifying the fuel cell during operation of the fuel cell is affixed to the second side 207 of the second frame placed near a coolant distribution region 301 of the flow assembly. A water inlet manifold 404 and a water outlet manifold 407 align in the first frame and second frame when the fuel cell is assembled. Figure 9D shows the water plate body 302, which may be compression fit onto the coolant distribution region 301 of the flow assembly or additional fastenings such as stich welds or spot welds 303 may be added to affix the water plate to the coolant distribution region of the second frame. A series of flow distributors also called rivulets 304 are channels formed in the water plate to direct water and water vapor (or other coolant which may be used). For the water plate to function at high predictability it requires it to maintain, when assembled and compressed into a fuel cell, contact with the coolant distribution region. The contact ensures even coolant distribution down river lets to rivulet outlets 305 formed as part of the water plate and aligned with shaped mixing inlets 215 (which are shown as scallops but may be any shape that supports the coolant mixing) in the second frame (see Fig. 91) whereby water dispersed from the water manifold through the water plate is infused into the flow field at specific mixing inlets aligned with channels which receive fluid flow that will pass into the active layer. In this instance the water rivulets align with the cathode inlet fluid stream and then exit the fuel cell via the water outlet manifold 407. Those of ordinary skill in the art will recognize in some instances the water may be directed (via manifolds and rivulets) to the anode side of a fuel cell and such a modification is within the scope of this disclosure. The assembled frames and other components as shown form a flow assembly 450 viewed from cathode side up.

[0091] Figures 9B , 9C and 9E-9G illustrate specified manifolds and a series of spacing or supporting structures. Also illustrated are cathode and anode galleries formed between regions of the first and second frame. The galleries are press formed into the first and second frames but also held at a nominal gallery height via protrusions (supporting structures) 231 whereby fluid flow therethrough is directed and controlled.

[0092] Figure 9E illustrates the anode side up of the flow assembly. The cathode air inlet manifold 402 is fluidly connected to air inlet gallery 412 which directs air and in some instances water or water vapor to the cathode face 202 of the fluid flow plate these fluids are directed to the cathode side 202 of the fluid flow plate via air inlet galleries 412, are shown between the fluid flow plates.

[0093] Fuel gallery 424 is configured to direct fuel 500 into the serpentine channels. The skilled artisan will recognize that the number of fuel galleries described herein for inlet or outlet are a design choice and not a limit to the scope of the disclosure. The fuel is directed to the anode side 204 of the fluid flow plate channel inlet 182.

[0094] In the galleries are shown supporting structures 231 configured to maintain nominal gallery size to assure sufficient flow and / or to direct fluid flows. The supporting structures work in concert and are configured to maintain fidelity of galleries and manifolds when the flow plate assemblies and fuel cells, including gaskets, formed thereby are highly compressed into a fuel cell stack.

[0095] Figure 9F illustrates the anode side up of three flow assemblies stacked with via the fuel inlet manifold 404 to a fuel inlet gallery to a distribution fuel gallery 424 into the channel inlet on the anode side 204 of the fluid flow plate. The remaining fuel exits the fluid flow plate at the channel outlet 185 via a fuel collection gallery 425 which is fluidly connected to a fuel outlet gallery which is fluidly connected to a fuel outlet manifold. Fuel flow into a stack of flow assembly and galleries are indicated by arrows 500.

[0096] Figures 9G and 9H provide illustrations of additional detail of the fuel 500 pathway through the galleries on the anode face of the flow field and the flow for oxidant and coolant 505 on the cathode side. A water gallery passage 406, also shown in Figure 10B, provides fluid connection for the water (coolant). A first MEA 150 and a second MEA 150’ are shown sandwiched between the cathode gas diffusion layer 170 and the anode gas diffusion layer 160. In this exemplar abutting the MEA is an MEA sub-gasket 600 preferable configured around the MEA and structurally form an active area of the active layers. A series of cathode side gaskets 605 and anode side gaskets 610 are illustrated. These gaskets cooperate with the supporting structures 231 to maintain the gallery height when the assemblies are compressed into a fuel cell stack. The gaskets are configured to seal the fluid galleries edges during compression to avoid leakage which will reduce performance and efficiency in the fuel cell stack.

[0097] Fuel gallery 424 is configured to direct fuel to the serpentine channels 180. The skilled artisan will recognize that the number of fuel galleries described herein for inlet or outlet are a design choice and not a limit to the scope of the disclosure. The fuel is directed to the anode side 204 of the fluid flow plate channel inlet 182.

[0098] Figure 91 and 9J illustrates the cathode side up of a fuel cell assembly illustrating the alignment of the rivulet outlet 315 and the mixing inlet 215.

[0099] In the galleries supporting structures 231 are configured to maintain nominal gallery size to assure sufficient flow and / or to direct fluid flows. They are positioned to provide support for the water plate 300 whereby it remains flat against the coolant distribution region 301. In some instances a spot or stich weld 303 will be added to affix the water plate directly to portions of the distribution coolant region 301. The water plate 300 has a coolant transport main 320 formed thereon is water distribution which has a series of interfaces 325 to fluidly connect the coolant transport manifold to the rivulet inlets 327. The rivulets 303 each have an outlet 305 configured to align with the shaped mixing inlets 215 in the second frame. The supporting structures 231 work in concert and are configured to maintain fidelity of galleries and manifolds when the flow plate assemblies and fuel cells, including gaskets, formed thereby are highly compressed into a fuel cell stack.

[00100] Figure 9K is a partial view of flow assembly. The oxidant is provided to the fuel cell cathode air inlet manifold 402 and exits the fuel cell via cathode outlet manifolds 403. As the oxidant passes through the assembly the fluid increases in temperature and moisture. Between the flow field and outlet manifold 403 is a pressure control region / passage 440 whereby pressure variation in the outlet across the stack caused by the additive nature of heat and moisture being passed from fuel cell 1 through N in a stack can be adjusted to control the flow balance per cell or group of cells (module) and ensure the best overall efficiency, whilst ensuring even flow balance. Additionally, such balance will be imparting reduced overall pressure drop and reduced parasitic power drain from the balance of plant components such as an air compressor (not shown). The pressure drop is a relative change in local static pressure - as the outlet overall static pressure will remain the same, the effect increases in the inlet static pressure. Therefore, allowing improvement in bulk flow distribution between a stack of multiple parallel fuel cell fluid compartments fed from the same upstream manifold and venting into the same downstream manifold.

[00101] Figure 10A illustrates aspects of and EC fuel cell assembly without active layers shown in a partial top view. The water plate is assembled on top of the second frame 200B and along one edge is a coolant transport main 320 that is fluidly connected to the rivulets 304 configured to distribute coolant to the rivulet outlets 305 onto the cathode face 202 face of the assembly. Although water is called out as the coolant in this disclosure, the skilled artisan and those of ordinary skill in the art will recognize that the disclosure is not limited to water. Water is supplied to the coolant transport main 320 via the water inlet manifold 304 which is configured and sealed with gaskets to fill up with coolant when the fuel cell is assembled into a fuel cell stack. Coolant fluid flow pathways are formed between the first and second frames to fluidly connect the water inlet manifold 406 by the touching faces of adjacent faces of the first and second plates together. In some instances the coolant can also both cool the plates and add humidification to one or more of the GDL and MEA.

[00102] Figure 10B shows a cut-away perspective view of section “A” of Fig. 10A. Supporting structures maintain the water gallery 317 height when the fuel cells are assembled into a stack. Without the supporting structures the height between frames, when compressed, the water inlet manifold height and volume is distorted and inconsistent which results in the flow being less predictable and gasket failure wherein water will leak from the water inlet manifold 406 to the non water galleries thereby flooding areas of the fuel cell. The coolant manifolds and galleries formed between the first and the second plates and the water plate are fluidly connected to the coolant transport main 320 of the water plate 300. In the implementation shown, coolant fluid is fluidly connected from the inlet manifold 406 to the coolant gallery 416 which is in fluid communication with the coolant transport main 320. In operation the method includes coolant fluid flows into a coolant entry volume within galleries 416 and then a first level of distribution is into the coolant transport main 320 then into and through the rivulets 304 the coolant fluid distributed through rivulets mixes with the cathode fluid flow in the cathode flow channels to provide evaporative cooling and to hydrate the MEA. In alternative arrangements, coolant fluid can be provided into the anode fluid flow in addition to or instead of the cathode fluid flow.

[00103] Figures 11A - 1 ID illustrate systems, methods and devices which are configured to at least one of adjust, select, adjust and control the overall pressure drop from inlet to outlet through an assembled operating fuel cell stack 1. The adjustment of outlet pressure drop in the contiguous fuel cells formed into a functional fuel cell stack and exemplars of coordination or control of the outlet pressure drops per fuel cell feeding into the outlet manifold which has measurable effect on stack performance and efficiency and can also reduce parasitic losses.

[00104] We have determined that by increasing the pressure drop in the pressure control region / passage 440 we can reduce variation from fuel cell to fuel cell in a stack via altering the cross sectional openings in the passage 440 stack performance across the fuel cells is improved. The cross section is changed via flow reduction elements 445 which may be columns, dimples, bumps or projections which may fill the passage from a first side 446 to the second side 447 and maybe but need not be functional as support elements but rather they reduce cross section and may also provide structure support. The cross sectional area is a tunable mechanical feature to optimize the stack function.

[00105] Figure 11A illustrates a fuel cell stack 1 with no fluid pressure drop control and it will result in uneven movement of fluid from fuel cell first (FCl) to the last fuel cell (FCN) in the stack. Flow 1 as it exits the fuel cell via the outlet into the manifold is somewhat restricted by the volume of fluid from the remaining fuel cells in the stack which are hotter and moister fluid then that which is passing through fuel cell first (FCl). Accordingly, in the pressure control region / passage 440 and as such the pressure differential from outlet to inlet in fuel cell first (FCl) is much less than that in fuel cell last (FCN), the thickness of flow arrows flow 1, flow 2A and flow 3 A depict the pressure difference. The fuel cell stack operation will be impacted if the resistance to airflow through fuel cell first (FCl) is fractional percentage of the flow through fuel cell last (FCN). The optimal configuration is that each fuel cell in the stack has uniform airflow through the flow field inlet to outlet.

[00106] Figures 1 IB and 1 IC illustrate a common restrictive pressure control region / passage 440 showing the active reduction zone 442 whereby the flow reduction elements 445 are structures such as dimples, bumps and projections which reduce the cross sectional area in the passage 440 of each fuel cell is the stack (FC1-FCN) the same amount. The reduction will reduce the pressure differential between fuel cells. The increase in pressure drop before the outlet feed into the common outlet 403 is a selected outlet pressure reduction in all the fuel cells. The unform flow reduction elements 445 in each fuel cell support a simplified fuel cell stack with all components being essentially the same. In some instances the flow reduction elements may be formed in at least one of the plate, the gasket, and the outlet manifold.

[00107] Figure 1 IC is a magnified view of a section “SOI” in which flow reduction elements 445 are shown with additional clarity. The illustrated shapes and orientation of such reduction elements is not a limitation nor intended to be limiting and the skilled artisan will understand that a plethora of shapes may be deployed to reduce the passage 440 cross sectional volume near the outlet manifold volume and the galleries or shape of the passage may which feed into that outlet manifold, in some instances, require that the shape and orientation of the reduction elements 445 conform to the available space.

[00108] Figure 1 ID shows a fuel cell stack 1 with a gradient flow reduction configuration 443 wherein each fuel cell in the stack has individualized predetermined volume of cross sectional restricting elements 445 to adjust each fuel cell or optimize airflow in each fuel cell.

[00109] Figure 1 IE illustrates a fuel cell stack in which the fuel cells forming the stack are segregated into modules and each module of fuel cells shares the same reduction element 445 configuration. The advantage of this system and methods is to simplify the assembly by reducing the number of different fuel cells in the stack. In this exemplar fuel cells first (FC 1) to four (FC4) form a first module with the same reduction elements 445 at a first density of reduction elements. Adjacent to the first module are fuel cells five (FC5) to fuel cell eight (FC8) which form a second module each with the same reduction elements 445 at a second density of reduction elements. Adjacent to the second module are fuel cells nine (FC9) to fuel cell twelve (FC12) which form a third module each with the same reduction elements 445 at a third density of reduction elements. Adjacent to the third module are fuel cells thirteen (FC13) to fuel cell sixteen (FC16) which form a fourth module each with the same reduction elements 445 at a fourth density of reduction elements. Adjacent to the fourth module are fuel cells seventeen (FC 17) to fuel cell last (FCN) which form a fifth module each with the same reduction elements 445 at a fifth density of reduction elements. A fuel cell stack will often have a far greater number of fuel cells forming the stack then what is described above and the skilled artisan will understand the concept presented in these simplified examples are applicable to larger stacks with dozens, hundreds or thousands of fuel cells therein.

[00110] While systems and methods have 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 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. Also, as used in the specification including the appended claims, the singular forms "a," "an," and "the" include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. The term "plurality", as used herein, means more than one. When a range of values is expressed, another exemplar includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about." it will be understood that the particular value forms another exemplar. All ranges are inclusive and combinable.

[00111] It is to be appreciated that certain features of the disclosure which are, for clarity, described herein in the context of separate exemplar, may also be provided in combination in a single exemplary implementation. Conversely, various features of the disclosure that are, for brevity, described in the context of a single exemplary implementation, may also be provided separately or in any sub combination. Further, reference to values stated in ranges include each and every value within that range.

Claims

1. A fuel cell comprising:a first flow assembly (250) having a first surface (252) and a second surface (254) comprising;a first frame (200A) including a first fluid flow plate (100) having a first face (102A) and a second face (102B);the fluid flow plate configured with a plurality of fluid flow channels (180) having inlets (182) and outlets (185);a pressure control passage (440) in fluid communication with the outlet;an active reduction zone (442) with the flow reduction elements (445) configured to reduce the cross sectional area in the pressure control passage;a second flow assembly (250); and,an active layer having at least a membrane electrode assembly (MEA) therein between the second surface (254) of the first fluid flow assembly and the first surface (252) of a second flow assembly (250); and, wherein fuel is supplied via galleries (230) to one side of the MEA and oxidant is supplied via galleries (230) to the other side of the MEA2. The fuel cell of claim 1, the pressure control passage further comprising an active reduction zone (442).

3. The fuel cell of claim 2 wherein the flow reduction elements are at least one of columns, dimples bumps and projections.

4. The fuel cell of claim 3 wherein one or more of the flow reduction elements fill the passage from a first side (446) to the second side (447).

5. The fuel cell of claim 3 or 4 wherein the flow reduction elements do not fill the passage from a first side (446) to the second side (447).

6. A fuel cell stack comprising a plurality of the fuel cells of any of claims 3 to 5.

7. The fuel cell stack of claim 6 wherein at least one of the flow reduction elementsis configured to provide at least some structural support to reduce collapse of the passage when fuel cells are compressed into a stack.

8. The fuel cell stack of claim 6 or 7 wherein the reduction of the cross sectional area in the pressure control passage via the density of restricting elements (445) is the same for each fuel cell in a stack.

9. The fuel cell stack of claim 8 wherein the reduced cross section of each fuel cell passage is a predetermined volume to reduce variation in the pressure drop across the fuel cells in the stack.

10. The fuel cell stack of any of claims 6 to 9 wherein the reduction of the cross sectional area in the pressure control passage via the density of restricting elements (445) is different for each fuel cell in a stack.

11. The fuel cell stack of claim 10 wherein the different reduced cross section in each fuel cell optimizes the performance of each fuel cell in the stack.

12. The fuel cell stack of any of claims 6 to 11 wherein:a plurality of fuel cells are formed into modules;each module is configured with the same density of restricting elements (445); each module has a different density then the other modules; and, the fuel cell stack is formed of the modules.

13. The fuel cell of any of claim 2 to 5 further comprising gas diffusion layers (GDL) placed on either side of the MEA.

14. A method of controlling pressure drop in an evaporatively cooled fuel cell stack, the method comprising:forming a plurality of fuel cells, each fuel cell comprising;an MEA between two GDLs forming an active layer;placing the active layer between a first fluid flow plate having fluid flow channels each of which has inlets and outlets in a first flow assembly (450) and a second fluid flow plate having fluid flow channels each of which has inlets and outlets in a second flow assembly (450);a pressure control passage (440) in fluid communication with each outlet;an active reduction zone (442) with the flow reduction elements (445) configured to reduce the cross sectional area in the pressure control passage;forming an inlet manifold fluidly connected the inlet of each fuel cell;forming an outlet manifold fluidly connected to the pressure control passage of each fuel cell;compressing the fuel cells into a fuel cell stack.

15. The method of claim 14, the pressure control passage further comprising an active reduction zone (442).

16. The method of claim 15 wherein the flow reduction elements are at least one of columns, dimples, bumps and projections.

17. The method of claim 16 wherein at least one of the flow reduction elements is configured to provide at least some structural support to reduce collapse of the passage when fuel cells stack is compressed.

18. The method of claim 16 or 17 wherein the reduction of the cross sectional area in the pressure control passage via the density of restricting elements (445) is the same for each fuel cell in the stack.

19. The method of claim 18 wherein the reduced cross section of each fuel cell passage is a predetermined volume to reduce variation in the pressure drop across the fuel cells in the stack.

20. The method of any of claims 16 to 18 wherein the reduction of the cross sectional area in the pressure control passage via the density of restricting elements (445) is different for each fuel cell in a stack.

21. The method of claim 20 wherein the different reduced cross section in each fuel cell optimizes the performance of each fuel cell in the stack.

22. The method of any of claims 16 to 21 wherein:the fuel cell stack contains a plurality of modules;each module contains a plurality of fuel cells each fuel cell in a module is configured with the same density of restricting elements (445); and, each module has a different density then the other modules.

23. The method of any of claims 16 to 22 further comprising gas diffusion layers (GDL) placed on either side of the MEA.

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