GB2628599A

GB2628599A - A fuel cell

Info

Publication number: GB2628599A
Application number: GB2304669.1A
Authority: GB
Inventors: James Mason Thomas; Charlies Engebretsen Erik; Derek Richard Kok Matthew; Philip Jones Simon
Original assignee: Bramble Energy Ltd
Current assignee: Bramble Energy Ltd
Priority date: 2023-03-29
Filing date: 2023-03-29
Publication date: 2024-10-02
Also published as: GB202304669D0; WO2024201083A1

Abstract

A fuel cell comprises at least one fuel cell board 200 with at least one first insulating layer 101,102, and a segmented membrane electrode assembly (MEA) 103 with at least one ion permeable membrane and multiple anodes and cathodes 113 provided on respective opposite faces of the membrane(s). At least one material property of the anodes or cathodes, such as the main or additive material used, the coating and/or the catalyst composition, properties, location or size, changes or varies across the surface of the fuel cell board. Alternatively, the size of the anodes or cathodes varies or changes across the fuel cell board, e.g. the width decreases or increases along the length of the MEA. In another aspect, at least one material property of another component, such as the gas diffusion layer, of the fuel cell board varies or changes across the fuel cell board. Also claimed is an arrangement in which pairs of anodes and cathodes across the at least one ion permeable membrane are electrically connected in parallel with adjacent pairs of anodes and cathodes (Figure 3e).

Description

Intellectual Property Office Application No GI323046691 RTM Date:25 May 2023 The following terms are registered trade marks and should be read as such wherever they occur in this document: Nation Sigracet SGL Carbon Avcarb Fumatech Fumapem Fluorinert Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo

A FUEL CELL

The present disclosure relates to fuel cells, uses of fuel cells, methods of controlling fuel cell voltage, components for fuel cells.

BACKGROUND

A fuel cell (e.g. a solid-polymer-electrolyte fuel cell) is an electrochemical device which generates electrical energy and heat from a reactant or oxidant (e.g. pure oxygen or air) and a fuel (e.g. hydrogen or a hydrogen-containing mixture, or a hydrocarbon or hydrocarbon derivative). Fuel cell technology finds application in stationary and mobile applications, such as power stations, vehicles and laptop lo computers.

Typically, a fuel cell comprises two electrodes, an anode and a cathode, separated by an electrolyte membrane that allows ions (e.g. hydrogen ions), but not free electrons, to pass through from one electrode to the other. A catalyst on the electrodes accelerates a reaction with the fuel on the anode to separate electrons and protons/cations, and oxidant on the cathode to undergo a reduction reaction to water. A circuit can then be formed between the anode and the cathode to generate a current to power a load e.g. an electrical device. A reactant fluid, e.g. oxygen or reactant air, is supplied to the cathode and a fuel, e.g. hydrogen, is supplied to the anodes.

A single pair of electrodes separated by an electrolyte membrane is called a membrane electrode assembly (MEA). A fuel cell MEA operating under a moderate load produces an output voltage of about 0.7V, which is often too low for many practical considerations. In order to increase this voltage, MEA5 are typically assembled into a stack as shown in FIG. 1. Each MEA has a layer of electrolyte membrane la (such as a NafionTM membrane), which comprises an ion-permeable membrane sandwiched between two electrode layers, and an anode 2 and a cathode 3 on either side of the electrolyte membrane. Adjacent MEAs can be separated by an electrically conducting bipolar separator plate 4, and a fuel (e.g. hydrogen) 5 and an oxidant 6 (e.g. oxygen gas or 'reactant air') flow through the channels provided on opposing sides of the bipolar plate. End plates 9 are connected to an external circuit via an electrical connector 7, 8. The number of these MEA5 in a stack in a fuel cell determines the total voltage that can be output, and the surface area of each membrane electrode determines the total current that can be drawn/output. Catalyst layers adjacent to the electrodes increase the rate of and efficiency of the reactions at the electrodes.

FIG. 2 shows an exemplary fuel cell of the prior art (see e.g. WO 2012/117035) in which a plurality of fuel cell boards 22 are stacked between two endplates 21 in order to provide increased voltage and power. Electrode pairs are arranged in a series along either side of a single layer of polymer electrolyte 10, such as a Nafionm membrane. Anodes 11 are disposed on one surface of these membranes and cathodes 12, separated by gaps are disposed on the other, opposite, surface of these membranes. The anode and cathode respectively of two adjacent electrode pairs may partially overlap. Through-membrane electrical connectors 13 connect the electrodes across the membrane in the overlapping region, and may be produced by a homogeneous chemical deposition process. A catalyst on the electrodes encourages the reactions at the electrodes. A fuel 17, such as hydrogen gas, flows along the face of the fuel cell board 22 supplying the anodes 11 and a reactant or oxidant 16, such as oxygen gas or air, flows along the surface of the fuel cell board 22 supplying the cathodes 12. One electrode at the edge of the upper surface and one electrode at another edge of the lower surface of the fuel cell board are connected to an external circuit via an electrical connection 18, 19.

In this series arrangement, the surface area of an electrode pair determines the size of the current for a fuel cell board 22, but the voltage accumulates in proportion to the number of electrode pairs on that fuel cell board 22.

Electrically insulating spacers 20 can be integrated into the stack between each of the fuel cell boards each comprising a spacer composed of electrically insulating material (such as plastic).

The size of an individual cell (the surface area of a pair of electrodes) determines the size of the current for a fuel cell board. The total number of individual cells on a fuel cell board determines the voltage produced. The number of fuel cell boards in a stack determines the size of the total current of the fuel cell stack.

The end cathodes and anodes 11 on each fuel cell board are connected to respective first and second output lines via electrical connections 18, 19. The connection between each fuel cell board in the stack and the second output line can be controlled by a switch mechanism such as a field-effect transistor (FET) switch providing power handling and control directly at the cell. Each of these switches can be controlled by individual control lines.

There are a number of factors that determine the performance and determine the consistency of voltage output/current output of a fuel cell. Maintaining the correct s water content in the electrolyte membrane is important to optimising and controlling a fuel cell's performance, as the humidity of a fuel cell board can affect performance and control. Fuel cell ion permeable membranes require a certain level of moisture to operate efficiently and to conduct the ionic current efficiently so that the fuel cell current does not drop. Water produced by the cell is removed by the flow of fluid along the cathode or wicked away. If a fuel cell board is too humid or too dry performance can be sub-optimal or variable during operation.

Temperature of a fuel cell or fuel cell stack, the temperature variance across fuel cells, cells or MEAs or individual fuel cell boards can determine the performance of a fuel cell and consistency of voltage output/current of a fuel cell or subsequent fuel cell stack.

Other factors of variance across fuel cell boards, such as fuel concentration, pressure or partial pressure of the fuel(s) and heat exchange fluid temperature (e.g. coolant temperature) can affect fuel cell performance and affect the consistency of voltage output/current of a fuel cell.

Consistency of voltage output/current of a fuel cell is important for most fuel cell applications. Unless specifically desired, too great a voltage variance can affect performance of the operations downstream of the fuel cell. It may be desirable to vary fuel cell voltage and control of this, if possible, is important for fuel cell design.

In view of the foregoing, there is a need to improve control of the voltage/current output of a fuel cell, through new methods and novel fuel cell designs. It is desirable to provide improved fuel cells, uses of fuel cells, methods of controlling fuel cell voltage, components for fuel cells.

SUMMARY

A first aspect of preferred embodiments provides a fuel cell comprising at least one fuel cell board. Each fuel cell board comprises at least one first insulating layer, at least one ion permeable membrane and multiple anodes and multiple cathodes. All cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface opposing the first surface of the ion permeable membrane. At least one material property of the anodes or at least one material property of the cathodes may vary across the fuel cell board. The size of the anodes and/or the size of the cathodes may vary of change from anode to anode across the fuel cell board. At least one material property of another component of the fuel cell board (for example the 'another component' may be ion permeable membrane or the gas diffusion layer) may vary or change across the fuel cell board. Each anode may have a different material property/composition or a different size to at least one/any adjacent anode/the other anodes on the same fuel cell board and/or wherein each cathode has a different material property/composition or size to at least one/any adjacent cathode/the other on the same fuel cell board cathodes. The size and/or material property/composition of each anode may be different to at least one/any adjacent anode/the other anodes on the same fuel cell board and/or wherein the size and/or material property/composition of each cathode may be different to at least one/any adjacent cathode/the other cathodes on the same fuel cell board. At least one anode or at least one cathode may have a different size (may be larger or smaller) or material property/composition to the other anode(s) on the same fuel cell board. A fuel cell board may have multiple ion permeable membranes, this may be one per anode and cathode pair.

Preferably, pairs of anodes and cathodes across the at least one ion permeable membrane may be electrically connected in parallel with adjacent pairs of anodes and cathodes.

The anodes and cathodes of the fuel cells described herein may be described as or referred to "segmented" throughout. Segmented anodes or cathodes are those with a gap between adjacent anodes or cathodes. Segmented anodes and cathodes form segmented membrane electrode assemblies (MEAs) or 'cells'. Each MEA can be formed of one anode and one cathode, each on an opposing face of an ion permeable membrane. One ion permeable membrane can have multiple anodes or cathodes or multiple MEAs across its surface(s). Multiple segmented MEAs can be found on a single fuel cell board of the present invention. MEAs may also be referred to as 'cells' herein. There may be multiple ion permeable 5 membranes across a fuel cell board, each with one or more anodes or cathodes. Each MEA may be one anode, one cathode and one ion permeable membrane. These are arranged such that each anode overlaps with at least one cathode through the ion permeable membrane and/or such that each cathode overlaps with at least one anode through an ion permeable membrane. The anodes and the 10 cathodes have a gap between the adjacent anodes or cathodes on the same fuel cell board.

Segmented anodes, cathodes, cells or MEAs may have varying, changing or different properties (e.g. size, geometry or material property/composition) to the other anodes, cathodes, cells, or MEAs (respectively) on the same fuel cell board.

This can be where at least one material property/composition or property of the anodes or wherein the size or the geometry of the anodes varies from anode to anode across the first surface of the ion permeable membrane and/or wherein at least one material property/composition of the cathodes or wherein the size or the geometry of the cathodes varies from cathode to cathode across the second surface of the ion permeable membrane. Each anode may have a different material composition or size or geometry to at least one/any adjacent anode/the other anodes on the same fuel cell board. Each cathode may have a different material property/composition or size or geometry to at least one/any adjacent cathode/the other cathodes on the same fuel cell board. The size, geometry and/or material property/composition of each anode may be different to at least one/any adjacent anode/the other anodes on the same fuel cell board. The size, geometry and/or material property/composition of each cathode may be different to at least one/any adjacent cathode/the other cathodes on the same fuel cell board.

Segmentation of MEAs on a fuel cell board in the manner described herein improves overall performance and durability of fuel cell boards. Segmentation can allow tailoring of the voltage/current properties of a fixed dimensioned stack.

As described in the background section, MEAs are typically designed to operate under specific conditions, and can be designed to account for different applications where increased or decreased temperature or humidity might be expected. But, the inventors have realised the advantages of designing MEAs to vary across individual fuel cell boards and the particular advantages and ability to do this with PCB-material based fuel cell boards.

s An increased level of tailoring and design of fuel cell boards is described herein, where the segmented MEAs, anodes, cathodes or cells will have their properties vary across a single fuel cell board. Different anodes or cathodes on the same face of a fuel cell board can have different properties (e.g. size, geometry or material composition) to others on the same face of the fuel cell board. These can be varied as described herein to account for the possibly different performance of MEAs across a fuel cell board. These can vary to account for changes in current density across a fuel cell board.

Variation in the conditions fuel cell boards are subject to, for example variance in temperature, humidity and fuel concentration, as described in greater detail herein, can be accounted for by varying the properties of the individual cells individually. These variances will result in a variation in current density across fuel cell boards. Design can account for variation across a fuel cell board which can occur depending on the fuel flow paths across boards. Tailoring MEAs to account for variance in conditions boards are subject to will result in a reduction in potential variance across the board. A reduction in potential variance across the board may be referred to as a flattening of the voltage (i.e. keeping the voltage within a certain range a reduction in potential variance across the board).

Reduction in the potential variance across the board results in improved performance of the fuel cell boards, and increased fuel cell board efficiency. The fuel cells and fuel cell boards described herein can be tailored to give the same power output but at a different voltage.

This is uniquely possible with the PCB fuel cell boards as described herein, because of their insulating properties and because of how they can be manufactured, when compared to for example metal or graphite fuel cell boards.

Because PCBs are insulating material, unlike metal or graphite based fuel cell boards of the prior art where the whole board is conductive, the fuel cell boards described herein can be designed to ensure that current only passes in specific locations, for example plated through holes, use of conductive material (e.g. copper) plating in selective areas of the PCB board, or electrical connection tabs at the edges of the MEAS. These may be connected so that the connections can dynamically be varied to maintain a desired voltage range (whilst keeping the KW power output constant), providing a consistent output if desired. This is not technically possible in, for example, metal fuel cell boards.

Furthermore, the herein described tailored varied segmentation can reduce the impact of transient events such as those which occur at fuel cell start up and/or fuel cell shut down. Gas fronts passing through/along the board can result in high potentials that can damage fuel cell boards, particularly the catalysts. By segmenting the cell into smaller areas the duration of these high potentials can be reduced to minimise degradation. This is particularly useful with segmented fuel cell boards where the properties of the cells vary across the board for example corrosion resistance catalysts can be used in areas where high potentials are likely to be experienced, or reversal tolerant material could be used where this may occur.

Further, segmenting the MEAs on fuel cell boards with varying properties reduces parts of the fuel cell ending up at a relatively low potential during operation. This is beneficial because large variance in potential can accelerate degradation of fuel cell boards. Thus, the fuel cell boards described herein have improved degradation resistance/longer lifespans.

A second aspect of preferred embodiments provides a fuel cell comprising at least one fuel cell board. Each fuel cell board comprises at least one first insulating layer, at least one ion permeable membrane, and multiple anodes and multiple cathodes. All cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface opposing the first surface of the ion permeable membrane. These are arranged such that each anode overlaps with at least one cathode through the ion permeable membrane and/or such that each cathode overlaps with at least one anode through the ion permeable membrane. Pairs of anodes and cathodes across the at least one ion permeable membrane are electrically connected in parallel with adjacent pairs of pairs of anodes and cathodes. Individual cells comprise at least one anode and at least one cathode on opposite faces of at least one ion permeable membrane such that the anode and cathode can exchange ions across the at least one ion permeable membrane. Each individual cell is connected in parallel across the fuel cell board.

Preferably for the second aspect at least one material property of the anodes or the cathodes or the size of the anodes or the size of the cathodes varies or changes across the fuel cell board, and/or at least one material property of another component of the fuel cell board varies or changes across the fuel cell board.

Pairs of anodes of cathodes across the at least one ion permeable membrane, sometimes referred to herein as individual cells on a fuel cell board or individual MEAs on a fuel cell board, may be electrically connected so that they are connected in parallel with the other (i.e. adjacent) pairs of pairs of anodes and cathodes on the same fuel cell board. They may be connected by any means known in the art, as described here.

Having the pairs of anodes and cathodes, individual cells on a fuel cell board or individual MEAs on a fuel cell board connected in parallel, rather than in series, will lower the overall voltage of the fuel cell and will increase the amount of current drawn from the fuel cell board, it can be termed "flattening" the polarisation/potential curve of the fuel cell. Operating in this method can be used to flatten the polarization curve.

A further advantage of having the individual MEAs on a fuel cell board connected in parallel is the ability to by-pass possibly faulty individual cells. In the arrangements where individual cells or MEAs on a fuel cell board are not connected in parallel, a faulty cell could bring the whole board offline, and indeed possibly the whole fuel cell stack offline. Being able to bypass faulty cells will keep the circuit open and the fuel cell board or fuel cell operational.

Operating the individual MEAs on a fuel cell board in series may produce a higher voltage (than when operated in parallel), which can be advantageous in certain circumstances. So, fuel cell boards connected to be switchable between series and parallel may advantageous, offering advantages over those just operable in series or operable in parallel.

Whilst described as "connected in parallel", these can also be electrically connected in series and connections can be dynamically switched during operation of the fuel cell, from parallel to series, to account for different needs during the operation of the fuel cell. Being "connected in parallel" does not mean they are not able to be electrically connected in series and the two switched between. Being able to alter the connection of these will also result in a flattening of the voltage (i.e. keeping the voltage within a certain range, a reduction in potential variance across the board). This allows a tailoring of the voltage of the fuel cell to match the desired application, here the same fuel cell could have connection pathways altered to have the fuel cell operate at high voltage/lower current or lower voltage/higher current reducing the need for a DC to DC converter. It will enable a reduction in power loses from conversions or cheaper system components (i.e. a smaller size DC to DC converter) to be used.

The following preferable embodiments relate to both the first and second aspect of the invention.

Preferably, the at least one ion permeable membrane is bonded to the at least one insulating layer.

Preferably, there are gaps between each anode across the first surface of the ion permeable membrane. Preferably, there are gaps between each cathode across the second surface of the ion permeable membrane. These are described as segmented' herein. Preferably, the gaps between adjacent anodes and/or adjacent cathodes are between 0.1mm-1.5cm, preferably between 0.2mm and 1cm.

Preferably, the fuel cell board comprises means configured to supply the cathodes with an oxidisable fluid and the fuel cell board comprises means configured to supply the anodes with a reducible fluid. Preferably, the means to supply the cathodes with an oxidisable fluid is an insulating layer comprising at least one first fluid path, and/or wherein the means configured to supply the anodes with a reducible fluid is an insulating layer comprising at least one first fluid path. Preferably, the at least one first insulating layer comprises at least one first fluid path and is either the means configured to supply the cathodes with an oxidisable fluid or is the means configured to supply the anodes with a reducible fluid.

Preferably, the one or more insulating layers are PCB boards. The insulating layers of the embodiments herein can be printed circuit board (PCB) layers, as described herein. Boards of insulating materials, such as FR-4 epoxy resin boards, have the advantage of enabling the elements to be manufactured in large quantities and at low cost. For example, multiple flow field boards can be manufactured at the same time, by using thin laminate boards which are stacked and then simultaneously routed or drilled. Individually routed boards are then stacked and laminated together. PCBs have a high mechanical strength, whilst being light, and when laminated together provide a solid structure, with good contact between the individual layers. Accordingly, a monolithic, light, and completely sealed structure is produced. Use of insulating materials to construct such fuel cell also enables the present fuel cells, fuel cell boards and components to be constructed without a mass or size penalty which may be present using other materials such as metal. These insulating material plates can be plated with copper and/or have plated through holes or other means to conduct electrical current through or across the plates. This allows improved control of current through stacks, as not all of the plates, spacers etc need be conductive, like when prior art bipolar plates or conductive metal components are utilised in prior art stacks.

Preferably, the anodes increase in size or decrease in size across the first surface of the ion permeable membrane, and/or preferably, the cathodes increase in size or decrease in size across the second surface of the ion permeable membrane.

The anodes and/or may are all be substantially the same length, but the width of the anodes or cathodes increases or decreases across the first/second surface of the ion permeable membrane. The size of the anodes or the size of the cathodes may comprise the width, height, length or thickness of the anode or the cathode. At least one anode may be larger or smaller than the other anode(s) of the fuel cell board. At least one cathode may be larger or smaller than the other anode(s) of the fuel cell board.

Preferably, only the anodes or only the cathodes have their material property/composition or size vary or changes from anode to anode across the surface of the ion permeable membrane.

Preferably, the anodes and/or the cathodes have a smaller size where the conditions the fuel cell board are subjected to are more favourable, compared to the anodes/cathodes elsewhere on the board. For example, where the fuel cell board may have a preferable humidity, temperature, fuel partial pressure (or other condition described here) the anodes and/or the cathodes can be smaller in size compared to the anodes/cathodes elsewhere on the board. Preferably, the anodes and/or the cathodes have a larger size where the conditions the fuel cell board are subjected to are less favourable, compared to the anodes/cathodes elsewhere on the board. There may be a gradient of sizes of anodes and cathodes based on the conditions the board may be subject to in operation. There may also be a change in other material properties of the anodes.

Preferably, at least one of the anodes (and possibly at least one of the cathodes) have a smaller size or width at the edge or side of the fuel cell board where the reducible fluid is first supplied to the anodes, compared to the size or width of the anodes (and possibly the cathodes) at the edge or side of the fuel cell board where the reducible fluid leaves the fuel cell board.

Preferably, at least one of the cathodes (and possibly at least one of the anodes) have a larger size or width at the edge or side of the fuel cell board where the oxidisable fluid is first supplied to the cathodes, compared to the size or width of the cathodes (and possibly the anodes) at the edge or side of the fuel cell board where the reducible fluid leaves the fuel cell board.

Preferably, the at least one of anodes (and possibly at least one of the cathodes) have a larger size or width at the edge or side of the fuel cell board where the reducible fluid is first supplied to the anodes, compared to the size or width of the anodes (and possibly the cathodes) at the edge or side of the fuel cell board where the reducible fluid leaves the fuel cell board.

Preferably, the at least one of cathodes (and possibly at least one of the anodes) have a smaller size or width at the edge or side of the fuel cell board where the oxidisable fluid is first supplied to the cathodes, compared to the size or width of the cathodes (and possibly the anodes) at the edge or side of the fuel cell board where the reducible fluid leaves the fuel cell board.

Preferably, the at least one of anodes (and possibly the at least one of cathodes) have a smaller size or width at the edge or side of the fuel cell board which has the highest humidity than the humidity of the other side or edge of the fuel cell board, compared to the size or width of the cathodes (and possibly the anodes) at the edge or side of the fuel cell board where the humidity is lower.

Preferably, the at least one of anodes (and possibly at least one of the cathodes) have a smaller size or width at the edge or side of the fuel cell board which has the highest partial pressure of reducible fluid, compared to the size or width of the anodes (and possibly the cathodes) at the edge or side of the fuel cell board where the partial pressure of reducible fluid is lower.

Preferably, the at least one of cathodes (and possibly at least one of the anodes) have a smaller size or width at the edge or side of the fuel cell board which has the highest partial pressure of oxidisable fluid, compared to the size or width of the cathodes (and possibly the anodes) at the edge or side of the fuel cell board where the partial pressure of reducible fluid is lower.

Preferably, an oxidisable fluid is initially supplied to the cathodes of the fuel cell board in a direction substantially opposite to direction in which a reducible fluid is initially supplied to the anodes of the fuel cell board.

Preferably, a heat exchange fluid is initially supplied to the fuel cell board either in a direction substantially similar to the direction in which a reducible fluid is initially supplied (to the anodes) of the fuel cell board or in a direction substantially similar to the direction in which an oxidisable fluid is initially supplied (to the cathodes) of the fuel cell board.

Preferably, the at least one anode and/or cathode material property/composition (which varies across the fuel cell board) is at least one of: i) at least one of the material the anodes and/or the cathodes comprise, or at least one of the additive materials provided to or with the anodes and/or the cathodes; ii) the coating of the anodes and/or the cathodes; and/or iii) the composition, material properties of, location or size of a catalyst layer on or with each of the cathodes and/or each of the anodes. Preferably, the composition of the catalyst layer comprises at least one of the ionomer content, catalyst loading or catalyst type.

Preferably there may be 2, 3, 4, 5, 6, 7, 8, 9, 10 or over 10 MEA5 on a single fuel cell board. Preferably there may be 20, 30, 40, 50, 60, 70, 80, 90, 100 or over 100 MEA5 on a single fuel cell board.

Preferably, wherein the fuel cell board does not have any MEA5 connected in parallel with each other, the fuel cell board comprises means to conduct electrical current from one face of the fuel cell board to the other face of the fuel cell board.

Preferably, these means are plated through holes. These plated through holes may go through the whole fuel cell board and can carry electrical current in series across a fuel cell board. Preferably, the means may conduct electrical current to or from copper plating on the insulating layer.

Preferably, the fuel cell board comprises means to conduct electrical current from the anodes through the at least one insulating layer to the surface of the at least one first insulating layer, and the fuel cell board comprises means to conduct electrical current to the cathodes through the at least second insulating layer from the surface of the at least one second insulating layer. Preferably, these means are plated through holes. Preferably, the number or frequency of the means to conduct electrical current vary across the fuel cell board. These can vary to account for variance in the anode and/or cathode design across the fuel cell board. A higher number, concentration or density of these can relate to a higher current density across a fuel cell board. Preferably, the means may conduct electrical current to or from copper plating on the insulating layer.

Preferably, each anode may overlap with at least one cathode through the ion permeable membrane and/or each cathode may overlaps with at least one anode through the ion permeable membrane. Overlaps refers to the body of the anode or cathode on one face of the ion permeable membrane at least in part overlapping with the body of the anode or cathode on the other face of the ion permeable membrane.

Preferably, the first insulating layer comprises at least one first fluid path. Preferably, the first insulating layer comprises multiple first fluid paths. Preferably, the multiple first fluid paths are substantially parallel to each other.

Preferably, the fuel cell board comprises a second insulating layer. The first insulating layer may comprise at least one first fluid path, the second insulating layer may comprise at least one second fluid path. The at least one ion permeable membrane and the multiple anodes and the multiple cathodes may be located between the first insulating layer and the second insulating layer so that the at least one first fluid path is arranged such that an oxidisable fluid can be supplied to one or more of the cathodes (all of the cathodes) of the at least one fuel cell board and so that the at least one second fluid path is arranged such that a reducible fluid can be supplied to one or more of the anodes (all of the anodes) of the at least one fuel cell board. The MEA, the first insulating layer and the second insulating layer may be laminated together to form the fuel cell board. Preferably, at least two of the layers of the fuel cell board are laminated together.

Preferably, the first insulating layer comprises multiple first fluid paths. Preferably, the multiple first fluid paths are substantially parallel to each other. Preferably, the second insulating layer comprises multiple second fluid paths, Preferably, the multiple second fluid paths are substantially parallel to each other.

Preferably, at least one of the at least one first fluid paths has a different flow path pathway/design to the at least one second fluid path.

Preferably, the first insulating layer comprises at least one fluid path for a heat exchange fluid. Preferably, the second insulating layer further comprises the at least one further or a third fluid path for a heat exchange fluid. The at least one further/third fluid path is arranged so that the heat exchange fluid can control the thermal properties or control the temperature of the fuel cell board, preferably at least the thermal properties or the temperature of the at least one anode. The heat exchange fluid is separated from the oxidisable fluid, these are different fluid flows. Preferably, the at least one further/third fluid path is on the opposite face of the insulating layer to the at least one first fluid path or the at least one second fluid path.

Preferably, the fuel cell comprises a plurality of fuel cell boards. The at least one fuel cell board may be arranged such that the first insulating layer and the one or more cathodes of each fuel cell board face the second insulating layer and the one or more anodes of an adjacent fuel cell board. The at least fuel cell board may be arranged such that the second insulating layer and the one or more anodes of each fuel cell board face the first insulating layer and the one or more cathodes of an adjacent fuel cell board.

Preferably, at least one of the first fluid path, the second fluid path or the third/further fluid path is substantially linear. Preferably, at least one of the first fluid path, the second fluid path or the third/further fluid path is serpentine.

Preferably, the fuel cell board comprises multiple first fluid paths and/or multiple second fluid paths and/or multiple third/further fluid paths. Preferably, the fuel cell board comprising at least one of the following: multiple first fluid paths which are substantially linear and substantially parallel with each other, multiple second fluid paths which are substantially linear and substantially parallel with each other and/or multiple third/further fluid paths which are substantially linear and substantially parallel with each other.

Preferably, the at least one further/third fluid path has a different flow path to the at least one first fluid path or the at least one second fluid path. For example, one of the paths may be substantially linear and the other may be serpentine.

Preferably there are more of one of the multiple first fluid paths and/or multiple second fluid paths and/or multiple third/further fluid paths than the other fluid paths, for example there may be more third/further fluid paths than the first fluid paths.

Preferably, the fuel cell further comprises further means to control the temperature of the at least one fuel cell board or adjacent fuel cell boards. The means to control the temperature of the at least one fuel cell board comprises at least one further insulating layer, the further insulating layer comprising at least one further/fourth fluid path for a heat exchange fluid. This at least one further insulating layer is arranged between the first insulating layer of the fuel cell board and the second insulating layer of an adjacent fuel cell board. This at least one further insulating layer comprises means to conduct electrical current from one face of the at least one further insulating layer to the other face of the at least one further insulating layer. This may allow it to act as a bipolar plate. This may enable electrical contact of anodes and cathodes of adjacent fuel cell boards, as described herein. The heat exchange insulating layer may be laminated to the first or the second insulating layer of the fuel cell board. Preferably, this further means laminated to the second insulating layer, i.e. adjacent to the anode side of the MEA. Lamination of the further means to the fuel cell board allows increased energy density because in this further means there may be just one further layer, as opposed to multiple layer means or thicker means as described previously. Further, sealing the further means plate to the fuel cell board simplifies assembly of the fuel cell stacks, due to there being fewer components and fewer non-builtin seals to the stack. Preferably, this further/fourth fluid path carries a coolant fluid to cool the fuel cell board or an adjacent fuel cell board. Preferably this heat exchange fluid is the same as the heat exchange fluid in the third/further fluid path located in/on the first insulating layer and/or located in/on the second insulating layer. Preferably this heat exchange fluid is different to the heat exchange fluid in the third/further fluid path located in/on the first insulating layer and/or located in/on the second insulating layer. This further means to control the temperature of the at least one fuel cell board or adjacent fuel cell board may be present when neither of the at least one of the first insulating layer or the second insulating layer comprises at least one further/third fluid path for a heat exchange fluid (i.e. in the absence of the at least one further/third fluid path for a heat exchange fluid). Preferably the further means to control the temperature of the at least one fuel cell board comprises a second further insulating layer, wherein the second layer seals or caps the flow path of the further/fourth fluid path (acting as described for other embodiments herein). The first insulating layer of this further comprises further means to control the temperature of the at least one fuel cell board or adjacent fuel cell boards may be thicker than the second further insulating layer, or the second further insulating layer may be thinner than the first insulating layer of this further comprises further means to control the temperature of the at least one fuel cell board or adjacent fuel cell boards. This further means to control the temperature of the at least one fuel cell board or adjacent fuel cell boards may have multiple fluid paths for heat exchange fluid, of different sizes, shapes and/or dimensions, different fluid types, or fluids at different flow rates or different fluid temperatures. Fluids could be at different temperatures or different flow rates in different plates, or at different temperatures or at different flow rates in different flow paths within the same plate. This can address varying coolant need throughout a fuel cell. Preferably, where multiple further means to control the temperature of the at least one fuel cell board or adjacent fuel cell boards are present in a single fuel cell stack, each further means to control the temperature of the at least one fuel cell board or adjacent fuel cell boards may have different fluid paths, different sized, shaped or dimensioned fluid paths or be designed to carry different fluids, or different temperature fluids, or fluids with different flow rates. This can address varying coolant need throughout a fuel cell. The further/fourth fluid path can be routed or depth routed into the insulating layer of this plate.

Fuel cell stacks with these additional heat exchange layers are advantageous because they do not need to be open to input of coolant air, as described in prior art systems, and they are completely sealed to the atmosphere. Although the integration of heat exchange fluid paths in the first or second insulating layers, as described herein, is the most space-efficient, utilising these additional heat exchange layers can increase power density when compared to prior art stacks due to the lack of non-functional spacer elements and the ability to supply reactant gases at a higher pressure thus increasing power density and reactant distribution on the electrodes.

Preferably, the face or surface of the first insulating layer adjacent to the cathodes in the fuel cell board is the face or surface which comprises the at least one first fluid flow path or channel, so that oxidisable fluid can flow to or diffuse to the one or more of the cathodes of the MEA (all of the cathodes). This may be through a gas diffusion layer.

Preferably, the face or surface of the second insulating layer adjacent to the anodes in the fuel cell board is the face or surface which comprises the at least one second fluid flow path or channel, so that reducible fluid can flow to or diffuse to the one or more of the anodes of the MEA (all of the anodes). This may be through a gas diffusion layer.

Preferably, the Membrane Electrode Assembly (MEA) further comprises at least one gas diffusion layer. The one or more gas diffusion layer(s) may be between the at least one cathode or all of the cathodes and the first insulating layer and at least one or all of the first fluid path(s). The one or more gas diffusion layer(s) may be between the at least one anode or all of the anodes and the second insulating layer and at least one or all of the second fluid path(s). The MEA may comprise multiple gas diffusion layers as described herein.

Preferably, the fuel cell comprises a means to air cool at least one of the fuel cell boards.

Preferably, the oxidisable fluid described in any aspect of the invention described herein is air and the reducible fluid is hydrogen gas.

Preferably, each fuel cell board may have a power rating of at least 10W.

Preferably, each fuel cell board may have a power rating of up to 1000W.

Preferably, each fuel cell board may have a power rating of lOW to 1000W. Preferably, a fuel cell comprising multiple fuel cell boards may have a power rating of at least 10kW. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of up to 1000kW. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of 10kW to 1000kW.

Preferably, one or more of the layers described herein are laminated together. This lamination may be achieved by chemical bonding by heating layers of prepreg between the insulating layers under pressure and an increased temperature, as described herein. Use of an epoxy resin prepreg also maintains compression of the gas diffusion layer of the MEA5, a critical component in maintaining fuel cell performance as it provides a sufficiently low resistance electrical path without compromising distribution of reactant fluids.

Preferably, the oxidisable fluid, the reducible fluid and/or the one or more heat exchange fluids enter and leave the relevant fluid paths described herein via inlets and outlets. These inlets and outlets may connect the fluid paths to manifolds which supply the relevant fluids to the fluid paths. These manifolds are those described herein, but may be apertures in the insulating layers.

Preferably, each fuel cell board described in any aspect of the invention described herein is connected to an electronic circuit to produce an electrical output, and wherein the connection between each fuel cell board and the electronic circuit is individually switchable. Preferably, the connection between each fuel cell board in the fuel cell and an output line can be controlled by a switch mechanism such as a field-effect transistor (FET) switch, providing power handling and control directly at the cell. Each of these switches can be controlled by individual control lines. This can be by providing a switch on each fuel cell board.

Preferably, one or more of the flow paths described herein is routed through the whole body of the layer. Preferably the fluid paths are routed into the insulating layers, optionally wherein the fluid paths are routed into the insulating layers prior to copper plating of at least part of the insulating layers.

Preferably, one or more of the fluid flow paths are formed within the insulating layer such that the fluid flow path is routed or grooved within the insulating layer without the routing or groove extending all the way through the insulating layer.

In embodiments, a fluid flow path is formed within or on an insulating layer such that the fluid flow path is routed or grooved within or through part of the body of one or more faces of the layer. In other words, the fluid flow path is formed without the routing or groove extending all the way through the layer. As can be seen throughout the figures herein, a fluid flow path or so-called depth route, provides a flow path for fluid within a single layer, as opposed to requiring one layer to provide a flow path, and another layer to provide a sealing face sealing the fluid path, as may be required in arrangements of the art. Depth routing to a depth of up to 1mm may be applied in embodiments. Depth routing to a depth of up to 3mm, 2 mm or 1mm may be applied in embodiments. Depth routing of around 3mm, 2mm, 1mm, 0.9mm, 0.8mm, 0.7mm, 0.6mm, 0.5mm, 0.4mm, 0.3mm, 0.2mm or 0.1mm may be applied in embodiments. Depth routing of around between 3mm and 0.1mm, or of around between 1mm and 0.3mm, or of around between 0.9mm and 0.4mm, or of around between 0.8mm and 0.4mm may be applied in embodiments. Here depth routing can be used because it maintains the sealing integrity of any one individual layer. Preferably, depth routing is where the whole layer (e.g. PCB board) is not routed through, i.e. only 100/0, or only 20%, or only 30%, or only 40%, or only 50%, or only 60%, or only 70%, or only 80%, or only 90% of the depth of the layer is routed through. Preferably only 10% to 90% of the depth of the layer is routed through, preferably only 20% to 80% of the depth of the layer is routing through, preferably only 50% to 75% of the depth of the layer is routing through. This may also be referred to as depth drilling.

Preferably at least 0.1mm of layer remains below the routed or drilled area after depth drilling. Preferably between about 0.10mm and 0.40mm of layer remains below the routed or drilled area after depth drilling.

Preferably, at least one of the insulating layers are at least partially coated with a passivating layer after copper plating at least part of the insulating layers.

An aspect of the present invention provides the use of any fuel cell described herein.

An aspect of the present invention is a component for an electrochemical device. The component may comprise any of the features described herein related to the insulating layers for the fuel cell boards. It may comprise an insulating layer comprising at least one first fluid path on one face of the insulating layer and a second fluid path for a heat exchange fluid on the other or opposite face of the insulating layer. This may be a component for any type of electrochemical device where anodes and cathodes are arranged across a membrane, as described herein.

An aspect of the present invention is a method of controlling fuel cell voltage, the method comprising operating a fuel cell comprising at least one fuel cell board, the at least one fuel cell board comprising multiple Membrane Electrode Assemblies (MEAs). The fuel cell board has at least one insulating layer, at least one ion permeable membrane and multiple anodes and multiple cathodes. All cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface of the ion permeable membrane.

They may be arranged such that each anode overlaps with at least one cathode through the ion permeable membrane and/or such that each cathode overlaps with at least one anode through the ion permeable membrane, forming the multiple MEAs on a single fuel cell board. Each MEA is electrically connected in parallel with each or both or all adjacent MEAs and the method comprises operating the fuel cell when each MEA is electrically connected in parallel with each or both or all adjacent MEAS.

Whilst described as "connected in parallel", these can also be electrically connected in series and connections can be dynamically switched during operation of the fuel cell, from parallel to series, to account for different needs during the operation of the fuel cell. Being "connected in parallel" does not mean they are not able to be electrically connected in series and the two switched between. Being able to alter the connection of these will also result in a flattening of the voltage (i.e. keeping the voltage within a certain range a reduction in potential variance across the board). This allows a tailoring of the voltage of the fuel cell to match the desired application, here the same fuel cell could have connection pathways altered to have the fuel cell operate at high voltage/lower current or lower voltage/higher current reducing the need for a DC to DC converter. It will enable a reduction in power loses from conversions or cheaper system components (i.e. a smaller size DC to DC converter) to be used. These may be connected so that the connections can dynamically be varied to maintain a desired voltage range (whilst keeping the kW power output constant), providing a consistent output if desired. This is not technically possible in, for example, metal fuel cell boards.

The fuel cell board of the method may comprise any of the features described herein related to the fuel cell boards above.

s Preferably, the connection between each MEA is individually switchable between the parallel connection and a series connection.

Preferably at least one material property of the anodes or the cathodes or the size of the anodes or the size of the cathodes varies or changes across the fuel cell board, and/or at least one material property of another component of the fuel cell board varies or changes across the fuel cell board.

An aspect of the present invention is a method of controlling fuel cell voltage, the method comprising operating a fuel cell comprising segmented MEAs on a single fuel cell board, wherein the segmented MEAs are connected in parallel with each other. Embodiments of the previous aspects may also apply to this method.

An aspect of the present invention is the use of segmented MEAs on a single fuel cell board and use of parallel connections between these segmented MEAs in a fuel cell. Embodiments of the previous aspects may also apply to this method.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which: FIG. 1 shows a schematic side view of a stacked fuel cell of the prior art; FIG. 2 shows a cross-section of a fuel cell of the prior art comprising a stack of fuel cell boards; FIG.s 3a to 3d show illustrative diagrams of how the size of MEAs can vary across one face of a fuel cell board, FIG. 3e shows a fuel cell board 50 with tabs 62, 63 to provide the possibility of connecting the cells/MEAs in parallel; FIG. 4 shows an expanded embodiment of a fuel cell board of the present invention; FIG. 5 shows a possible electron pathway in a segmented active area of a fuel cell board FIG. 6 shows a fuel cell of an embodiment; FIG. 7 shows how fuel cell stacks can be tailored to have the same power s output but at a different voltage, depending on the requirements; and FIG.s 8a to 8d show modelling of segmented fuel cell boards.

DETAIL DESCRIPTION

Embodiments will now be described in detail with reference to the accompanying drawings. The same reference signs indicate the same or similar features in different figures and embodiment of the invention, although this is only for reference and is not limiting on the invention. In the following detailed description numerous specific details are set forth by way of examples, in order to provide a thorough understanding of the relevant teachings. However, it will be apparent to one of ordinary skill in the art that the present teachings may be practiced without these specific details.

Fuel cells can be run more efficiently if at least one material property/composition of the anodes or the size of the MEAs varies or changes across a fuel cell board. For example, the size, geometry or material property/composition of the MEAs, membranes, anodes or cathodes are varied based on their location in relation to the flow paths transporting fuels and heat exchange fluids to/across the fuel cell boards. Variations in the conditions that fuel cell boards are subject to, for example temperature, humidity and fuel concentration can be accounted for by varying the properties of the individual cells. Varying cell design can account for variation across a fuel cell board, which can occur typically depending on the fuel flow paths across boards. Tailoring MEAs to account for variance in conditions boards are subject to means that there is a reduction in potential variance across the board.

The temperature of a fuel cell board can vary across the board due to a number of factors. For example, if the location on the fuel cell board is near the exit of a heat exchange fluid (e.g. coolant) fluid flow, then that area of the fuel cell board is likely at a higher temperature as the heat exchange fluid is likely warmer. Further for example, if the ion permeable membrane on the board next to a location in question is locally dry, then there will be a decrease in fuel cell performance, there will be a lower voltage for equivalent current which means more waste heat will be generated, and this location of the fuel cell board may have a higher temperature than other areas.

The humidity of a fuel cell board can vary across the board due to a number of factors. For example, typically those areas of a fuel cell board with a higher temperature (as described above), will have a lower humidity. Water is generated by the cathodes of a fuel cell board, but this can diffuse to the anodes of a fuel cell board. At the inlet for the reducible fluid (e.g. H2 gas) there is typically more water generated, as the fuel concentrations are higher and because the system is wetter. Further, H2 may be re-circulated in fuel cell stacks, and re-circulated H2 fluid may have a higher water content then previously circulated H2. This may diffuse to drier areas of the fuel cell board. Generally, an MEA with higher humidity will have lower resistance and achieve higher current density for the same voltage.

Generally, the flow directions of the fuels and heat exchange fluids can affect humidity variations across fuel cell boards. But there is typically always some sort of humidity variation across a fuel cell board in normal operation.

Fuel concentrations or partial pressure of reactants can vary across a fuel cell board due to a number of factors. For example, the concentration of reactant in the fuels (the reducible fluid or the oxidisable fluid, e.g. H2 and 02) decreases as the fuels react with the anodes and cathodes across the fuel cell board.

The pressure of the fluids being supplied to the fuel cell boards, i.e. the fuels (e.g. reducible fluid or the oxidisable fluid) or the heat exchange fluids (e.g. coolants) being supplied to a fuel cell board can vary across a fuel cell board due to a number of factors. The pressure of these can vary across the board due to a number of factors. For example, pressure is likely highest at the inlet of the fluid, regardless of the stream, as pressure losses occur for any flowing fluid as they travel along a fluid path. Further, the partial pressure decreases even more rapidly as the both the concentration of the fluid decreases (for example as fuel is consumed by the MEAs of the fuel cell board), and as the overall system pressure decreases.

Known transient events can also be accounted for with variation in fuel cell design, such as those which occur at fuel cell start up and/or fuel cell shut down. Gas fronts passing through/along the board can result in high potentials that can damage fuel cell boards, particularly the catalysts.

Figure 3a shows is an illustrative diagram showing how the size of MEAs can vary across one face of a fuel cell board 50. Fuel cell board 50 is shown with six rectangles 52, 54 across the face of this fuel cell board shown. The rectangles represent 'active areas' of a fuel cell board, and could be anodes or cathodes, or representative of MEAs or cells. Fig. 3a illustrates how the size of the cathodes, anodes, both, cells or MEAs can vary across a single face of a fuel cell board 50. Here, the furthest left rectangle 52 has the smallest size and the furthest right rectangle has the largest size 54.

FIG. 3b shows an illustrative diagram showing a fuel cell board 50 where the segmented MEAs 52 do not vary (in size or properties) across the face of the fuel cell board 50. The rectangles represent 'active areas' of a fuel cell board, and could be anodes or cathodes, or representative of MEAs or cells. The left-hand side of the board 50 has the inlet to the flow paths across the faces of the board 50 for air (02, cathode reactant fluid) and coolant (heat exchange fluid). The right-hand side of the board 50 has the inlet to the flow path for the H2 (anode reactant fluid). Here parallel fluid paths will carry all three fluids across the respective faces (coolant over the anode face) to outlets on the opposite edge of the fuel cell board.

FIG. 3c shows a fuel cell board 50 where the segmented MEAs do vary in size across the fuel cell board 50. Fuel cell board 50 is shown with ten rectangles 54 to 52 across the face of this fuel cell board shown. As with FIG.s 3a and 3b, the rectangles represent 'active areas' of a fuel cell board, and could be anodes or cathodes, or representative of MEAs or cells. FIG. 3c illustrates how the size of the cathodes, anodes, both, cells or MEAs can vary across a single face of a fuel cell board 50. Here, the furthest right rectangle 52 has the smallest size and the furthest left rectangle has the largest size 54. Fluid inlets, outlets and flow paths are the same as for FIG. 3b.

The anodes can increase in size or decrease in size across the board. Alternatively, or additionally, the cathode can increase in size or decrease in size across the board. The size of the anode or the size of the cathodes comprises the width, height, length or thickness of the anode or the cathode. Both may increase or decrease in the same pattern as each other on the other face of the PCB board. This may be across the at least one ion permeable membrane, or there may be multiple ion permeable membranes across the board.

Particularly, the anodes and/or cathodes may all be substantially the same length, but the width of the anodes or cathodes may increase or decrease across the ion permeable membrane.

The shape of the segmented anodes or the segmented cathodes may vary across the ion permeable membrane. Shape may vary to follow fuel particular flow path designs, for example anode shapes may vary across the surface of the ion permeable membrane to follow the anode fuel (reducible fluid e.g. H2) flow path in an anode (PCB) plate adjacent to the anode layer.

FIG. 3c shows how segmented MEAs could be arranged in a relatively low humidity, drier, fuel cell system. Humidity can be a key limiting factor on fuel cell board performance. Here a design for a low humidity system is described, where particularly the cathode air stream has a low or near zero humidity.

If the boards of both FIG. 3b and FIG. 3c were in a low humidity system, the furthest left MEAs would have the lowest humidity as the 02 air stream enters the fuel cell board at a low humidity. The furthest right MEA would experience a high H2 concentration as it is closest inlet, and thus produce a relatively greater amount of moisture. Further, as the air flows over the fuel cell board it will become more humidified and will be more humidified by the time it reaches the furthest right MEA. Thus, the right hand MEAs will have the highest humidity.

The MEAs have been designed to account for the higher humidity at the furthest right side of the board. The smaller MEA here will lower the reaction rate at the furthest right MEA, or conversely this could be described as having the larger MEA on the left side to as to increase the reaction rate at this MEA. This balances the discrepancies in conditions experiences at different sides of the fuel cell board, balancing out the electrical properties (i.e. current density) of the fuel cell board.

Here, the MEAs are shown designed to account for variations with a counter flow of the anode and cathode fluids (H2 and air are shown in counterflow in FIG.s 3b and 3c). Counterflow H2 and air typically balances out the current density experience across the fuel cell board. But, MEAs could be varied to account for co-flow (H2 and air inlets the same side of the fuel cell board) arrangements (as well as counter flow).

Fuel cell boards shown in FIGs 3a, 3b and 3c are suitable for use with parallel fuel flow paths, where fuels (the reducible fluid or the oxidisable fluid, e.g. H2 and air) are passed over this face of the fuel cell board in parallel flow paths. The MEA properties, here shown as size, can be varied to account for variations in the conditions the MEAs are subject to on the fuel cell board.

A fuel cell board could have variance in MEA design to account for different flow paths, as well as parallel flow paths. Various flow field patterns and entry and exit points on a plate to the plate will be known to those of skill in the art. For example, flow paths can be serpentine, circular or just channels straight across a plate (i.e. parallel). Flow fields can enter and leave by the same side of a plate or opposing sides or corners of the plates. For example, MEAs could have staggered sizes or material properties to account for variations in reactant or reaction conditions (e.g. humidity) along serpentine flow path as well as the parallel paths shown here.

Use of PCB materials to construct the fuel cell boards allows segmentation of the MEAs into smaller areas without lateral conductivity between MEAS. This would not be possible in fuel cell boards made of conductive materials, such as metal or graphite. Thus, the varied MEA designs shown herein can be created.

The number of anodes, cathodes, cells or MEAs on a single fuel cell board is not limited to the number shown in the examples herein. There may be as few as two segmented MEAs on a single fuel cell board, preferably there may be 2, 3, 4, 5, 6, 7, 8, 9, 10 or more MEAs on a single fuel cell board. There could be over 10 MEAs on a single fuel cell board, for example 20, 30, 40, 50, 60, 70, 80, 90, 100 or over 100 MEAs on a single fuel cell board, depending on fuel cell board size.

The fuel cell boards may be constructed in any suitable and desirable dimensions.

In some embodiments, the thickness of the electrolyte membrane layer may be between 1-200pm, and preferably between 5-100pm. The electrode bands/MEAs may be 1mm-10cm in width, preferably 2mm-5cm in width. The electrode bands/MEAs may be up to 500 by 500 mm, preferably 300 x 100 mm, 300 x 200 mm or 300 x 300 mm. The gaps between the electrode bands may be between 0.lmm-1.5cm wide, preferably between 0.2mm and 1cm wide. The width of the through-membrane electrical connectors may be 1pm-2mm and preferably 10pm1mm.

Anodes and cathodes can have the same design pattern, geometry size, shapes or material properties on opposing faces of the ion permeable membrane, or anodes and cathodes can have different design pattern, geometry size, shapes or material properties on opposing faces of the ion permeable membrane. This is as long as all anodes and all cathodes overlap with at least one cathode or anode through the ion permeable membrane, so there can be exchange of ions for fuel cell operation.

As well as size, MEAs can have their material properties varied across the fuel cell board, as described later.

MEAs can be designed to account for different limiting factors, for example humidity, temperature or partial pressure of the reactant fluids.

For example, if H2 or 02 partial pressure in reactant flow was known to be a limiting factor in a fuel cell stack design, the MEAs could be designed to account for this. The anodes (and possibly the cathodes) may have a smaller size or width at the edge or side of the fuel cell board where the fluid which is considered the limiting factor to the reactions on the fuel cell board is supplied to the fuel cell board. The anodes (and possibly the cathodes) may have a larger size or width at the edge or side of the fuel cell board where the fluid which is considered the limiting factor to the reactions on the fuel cell board leaves the fuel cell board.

For example, the MEA on the side of the board at the anode flow (H2) inlet would experience the highest H2 concentration and thus a higher reaction rate. If this was the furthest left MEA, then the furthest right MEA would experience the lowest H2 concentration and reaction rate. Thus, if size was varied across the fuel cell board to account for partial pressure (e.g. H2 partial pressure), the smallest MEA could be located at the end of the board with the anode inlet, and the largest MEA could be located at the opposite end of the board, at the anode outlet side. This would balance current density, to account for the higher reactant rate at the anode inlet with the higher H2 partial pressure/concentration. The same could apply if 02 partial pressure/concentration was limiting.

An oxidisable fluid may be initially supplied to the cathodes of the fuel cell board in a direction substantially opposite to direction in which a reducible fluid is initially supplied to the anodes of the fuel cell board. A heat exchange fluid may be initially supplied to the fuel cell board either in a direction substantially similar to the direction in which a reducible fluid is initially supplied (to the anodes) of the fuel cell board or in a direction substantially similar to the direction in which an oxidisable fluid is initially supplied (to the cathodes) of the fuel cell board.

The material properties or material composition of the anodes or the cathodes can vary across the fuel cell board or the ion permeable membrane. Anodes can be designed to be aid in the hydrogen oxidation reaction (HOR), be robust to degradation (thermal cycling, voltage, acidic environment), and have a high electrochemically active surface areas (ECSA). The same applies for cathode but for the oxygen reduction reaction (ORR).

Anodes and cathodes may comprise platinum with a carbon support. Other platinum group metals can be used (Pt, Ir, Os, Rh, Ru, Pd) as well as non-precious metals (NPM5) which have much lower electrochemical activity such as Ni, Fe, Co, Sn).

These could vary by ionomer content, PTFE content, catalyst content, composition of the electrodes of by varying the coatings on the electrodes.

The materials that the anodes and/or the cathodes themselves are made of may vary. This could be by changing the material the electrodes are made of, i.e. they could be made of graphite, Pt, Ir, a mixture of these or of different mixes or materials across the face of a fuel cell board. For example the % of platinum in graphite electrodes might vary across a fuel cell board to account for variation in zo condition across the fuel cell board.

The additive materials provided to or with the anodes and/or the cathodes may vary. This could be by addition of Iridium Oxide, PTFE, Ru, in varying concentrations across a fuel cell board.

A gas diffusion layer (GDL) may also be present between the flow paths and the anodes/cathodes. MEAs may also comprise one or more gas diffusion layers. These may be porous carbon papers such as Sigracet (SGL Carbon), Avcarb, or Toray. These can also be metallic foams or porous metallic materials (e.g. foams or felts). These may comprise aluminium, titanium or stainless steel. The material structure of this could also be varied across the face of the fuel cell board, and 'material composition of MEA5' as used herein includes the composition of this GDL.

The electrolyte membrane may be a proton-exchange membrane (PEMFC), also known as polymer electrolyte membrane (PEM). This may be fluorinated (for example a sulfonated tetrafluoroethylene based fluoropolymer-copolymer, e.g. NafionTM) or a not fluorinated membrane (for example a hydrocarbon membrane, e.g. an Ionomr PEMIONTM membrane). The membrane may be Ionomr PemionTM GORE-SelectTM membrane or a Fumatech FumapemTM membrane. Or, the electrolyte membrane may be an anion exchange membrane (for example a Fumatech FumasepTM FAA-3 membrane). Other such suitable membranes known in the art may be used with the embodiments herein.

In some embodiments, a catalyst layer on the electrodes accelerates a reaction with the fuel (on the anode electrode) and oxidant (on the cathode electrode) to create or consume the ions and electrons. This layer may be made of suitable catalytic material for the reactions of interest, as is commonly understood by a person skilled in the art of fuel cell production. For example, the catalyst layer may be composed of platinum nanoparticles deposited on carbon and bound with a proton conducting polymer (e.g. NafionTM). The catalyst layer may be on or with each of the cathodes and/or each of the anodes. The composition of the catalyst layer may vary from anode to anode or cathode to cathode across the surface of the ion permeable membrane. For example, there may be variation in at least one of the ionomer content, catalyst loading or catalyst type across the fuel cell board.

The herein described tailored varied segmentation can also reduce the impact of transient events such as those which occur at fuel cell start up and/or fuel cell shut down. Gas fronts passing through/along the board can result in high potentials that can damage fuel cell boards, particularly the catalysts. By segmenting the cell into smaller areas the duration of these high potentials can be reduced to minimise degradation. This is particularly useful with segmented fuel cell boards where the properties of the cells vary across the board for example corrosion resistance catalysts can be used in areas where high potentials are likely to be experienced, or reversal tolerant material could be used where this may occur. The relative smaller area of some anodes or cathodes means the extent of damage on each MEA can be balanced, reducing variation in MEA efficiency during operation.

Specifically The catalysts could be varied by changing catalyst type or % loading across the anodes and/or cathodes. For example where the conditions are less favourable for the anode (for example the anodes furthest from the anode reactant inlet or closest to the anode reactant fluid outlet) additional iridium oxide that can react with water preventing damage to the catalyst support can be added to the anodes/anode catalysts. This can just be on the anodes known to experience less favourable conditions. For example, a catalyst tolerant to anode fuel poisoning (for example PtRu catalyst which is tolerant to CO poisoning of H2) could be added to the anodes closer to the anode reactant inlets, so those anodes would be more resistant to such conditions.

The number or frequency of the means to conduct electrical current to or from the anodes, or the layout of the means to conduct electrical current from one face of the fuel cell board to the other face of the fuel cell board can vary across a fuel cell board to account for variance in the anode and/or cathode design across the fuel cell board.

FIG 3d shows how the means to conduct the electricity generated by a fuel cell board 50 can be arranged to account for the variation in the size of the active areas of the fuel cell board. Here, the means to conduct the electricity 60 can be plated through holes (PTHs), as described herein. They are represented with rows 60 in Fig. 3b. With a smaller active area, a higher density of PTHs 60 in the smaller active area can carry away more current, as a consequence of higher current density in smaller and more efficient MEA5. PTHs 60 can also act to carry heat away, which can be advantageous in those MEA5 undergoing a higher reaction rate.

The "means to conduct electricity" as referred to herein may be plated through holes. "Plated through holes" (PTHs) are holes that form a conduit through one or more insulating material layers, said conduit running substantially perpendicular to the planar surfaces of the fuel cell boards. These are plated with a conductive material, for example copper, to act as a conduit for electricity. The Plated though holes are necessary because PCB material (e.g. FR-4) is electrically insulative so PTHs must be introduced so that electricity can pass through the plates. These may be formed by holes bring drilled through the layer of insulating material (for example a PCB plate) and then lining with a conductive material. For example, they may be lined with a conductive material by an electroplating dip process such that copper lines the edge of each hole. Optional additional steps can occur after electroplating, wherein i) resin can be used fill the remainder of the hole, which is achieved by forcing resin over the PCB such that it flows through any holes present; ii) electroplating dip processing again such that the resin filled holes are capped with copper on both sides; and iii) there may be a mild milling process after this to ensure the surface of the PCB is flat. When these are found through PCB layers they can create continuity between two layers of copper plating on either side of the PCB material. PTH5 may be formed through only certain layers of the insulating materials described herein, or through only some layers of the fuel cell boards described herein (for example through just the anode and cathode plates, to be able to carry current to/from the anode/cathode to the outer surface of a layer of insulating material). PTH5 may be formed through the whole fuel cell board (for example through both the anode and cathode plate with the same hole, to be able to carry current to/from one surface of the fuel cell board to the other surface of the fuel cell board).

FIG. 3e shows a fuel cell board 50 with tabs 62, 63 to provide the possibility of connecting the cells/MEAs in series or in parallel. MEAs/cells 52, 54 are shown with a variation in size, the largest MEA 54 found on the further right of the board. Six MEAs/cells are shown, each with a tab 62, 63 opposite edges of each MEA/cell (totalling 12 tabs 62, 63 across the six MEAs).

The current from each MEA can be collected at tabs or connection points at the edge of each MEA, for example, electrode tabs, on the individual MEAS. Tabs can be for example parts of a PCB board with a copper plating which is electrically connected to a part of the MEA, so as to be able to carry current away from that MEA. This can be via copper plating, wires or any means suitable and known in the art for carrying current away from a planar MEA. These tabs or connection points at the edge of each MEA can then be electrically connected to other tabs or connection points of other MEAS. These connections can be wired in series or parallel.

Two different connection/wiring types are shown on the same fuel cell board to illustrate the comparison between the possible series or parallel connections of the MEAs/cells.

The top set of tabs 62 in FIG. 6e are shown connected in series with one another. Each MEA is connected in series with the adjacent MEAS. These are connected in series to the rest of the tab.

The bottom set of tabs 63 in FIG. 6e are shown connected in parallel pairs. Each parallel connected pair of MEA/cells is then connected in series with the rest of the fuel cell stack.

The MEA can be connected so that the MEAs can be connected electrically in either in series or in parallel, depending on what is needed in operation, to vary the voltage. This switching between series and parallel connection can be used to advantageously flatten the voltage of the fuel cell, if desirable.

FIG. 4 is a schematic diagram of one view of an expanded PCB fuel cell board 200. Fuel cell board 200 is shown expanded for the purposes of this figure, to show the membrane electrode assembly layer 103 separated from cathode plate 101 and anode plate 102. The cathode plate may be the first insulating layer as described herein. The anode plate may be the second insulating layer as described herein.

MEA layer 103 has ten cells or MEAs 113 which are visible in a planar arrangement. Each MEA 113 comprises an ion permeable membrane, an anode and a cathode.

Two MEAs 113 are labelled in FIG. 4, but all 10 are in part visible. MEAs 113 of this embodiment have all cathodes are arranged on a first surface of the ion permeable membrane and all anodes are arranged opposite the cathodes on the other surface of the ion permeable membrane. Only a single membrane is present. In this embodiment MEAs 113 are laminated between the cathode plate 101 and anode plate 102, but are shown separated/expanded in this figure just to show their presence. The lamination process is described later. Here anodes face anode plate 102 (face up in FIG. 4) and cathodes face cathode plate 101 (face down and not visible in FIG. 4).

This shows one embodiment of an MEA suitable for use for the embodiments described here. Other MEA designs, shapes, orientations would be known to a person of skill in the art and understood to be suitable with the present embodiments. Variation in MEAs can be as described herein. Just variation in size of MEAs is visible in this embodiment. The MEA layer 103 comprises a sealing/lamination material such as prepreg, visible in MEA layer 103 as the non-MEA 113 area. 113 shows the MEA which can include a gas diffusion layer. The ion permeable membrane extends beyond this area for a small distance (around 0.2 mm all the way to the edge of the module), to form a seal with the prepreg. The ion permeable membrane is sandwiched between prepreg in this area.

Cathode plate 101 and anode plate 102 here are partially copper plated printed circuit boards (PCBs), but in embodiments herein could be layers of any insulating material as described herein. In a fuel cell board 200 the cathode plate 101 and anode plate 102 are laminated together with the MEA layer 103, the MEA5 are located between the cathode plate 101 and anode plate 102 to form a fuel cell board 200. In FIG. 4 only inner face 101a of cathode plate 101 and outer face 102b of anode plate 102 are visible. The inner faces of both cathode plate 101 (face 101a shown in FIG. 4) and anode plate 102 are plated with copper and routed with flow field 111, 112 designs, with a passivating ink screen printed over the flow field surfaces on the inner faces of both plates 101, 102 to prevent degradation. Only the flow cathode flow fields 111 are visible on the inner face 101a of cathode plate 101 (one flow field 111 is labelled in FIG. 4, but multiple flow parallel field paths 111 are visible). In FIG. 4 the flow fields for the anode plate 102 are not visible, they are on the not visible inner face 102a of the cathode plate 102. The flow fields 111 on the cathode plate 101 may be the first fluid paths as described herein and the flow fields on the anode plate 102 may be the second fluid paths as described herein.

In the specific embodiment displayed in FIG. 4, but also generally in all embodiments, flow fields are routed into the PCB to provide paths for the reactants (for example air, hydrogen) to be supplied to the cathodes and anodes. Oxidisable fluids flow only to one or more of the cathodes and reducible fluids flow only to the one or more of the anodes of each fuel cell board. Reference herein to oxidisable fluids' refers to fluids that will react at the cathode, for example air or oxygen. Reference 'reducible fluids' refers to fluids that will react at the anode, for

example hydrogen.

Here, the flow fields are channels routed into the surface of the PCBs, but are not routed through the whole body or volume of the board. They are just routed into one surface, no flow field or channels are found on the opposing face to the face into which the fields are routed. The present arrangement allows effective separation of the reactants for the anodes and the cathodes. For example, as visible in FIG. 4, flow fields 111 on cathode plate 101 are only routed into face 101a of anode plate 101, they are not routed through the whole body of the plate through to face 101. The same for the flow fields (not visible in FIG. 4) on the anode plate 102. Thus, no flow field is visible on the outer face 102b of the anode plate 102 (and no flow field would be visible on the outer face 101b of cathode plate 101). When the boards are laminated the flow fields are located over the relevant part of the MEA5 113 (the anode flow field over the anodes, the cathode flow fields over the cathodes), so as to supply the relevant reactant directly to the anodes and the cathodes. The pressure of the reactant fluids supplied ensures a reaction at the anodes and the cathodes. Recants will enter one side of the plate and leave via the opposing side of the plate, in this embodiment with parallel flow fields.

Various flow field patterns and entry and exit points on a plate to the plate will be known to those of skill in the art. For example, flow paths can be serpentine, circular or just channels straight across a plate (i.e. parallel). Flow fields can enter and leave by the same side of a plate or opposing sides or corners of the plates. It is advantageous to have flow of reactants enter and leave opposite sides of the plate so that the reactant manifolds can easily be separated on opposing sides of a fuel cell.

The outer faces 101b, 102b of plates 101, 102 are also copper plated and are routed with the desired copper design. The plates are then drilled with holes for the various manifolds and flow fields.

After lamination, the outer surfaces 101b, 102b of the cathode pate 101 and the zo anode plate 102 have further holes 103, 104 drilled or routed. These holes 103, 104 provide access into their respective flow fields 111 for reactant fluids (e.g. air and hydrogen) to be supplied from the manifold and back into the manifold, to and from (respectively) the flow fields 111.

On the cathode plate 101 reactant air is supplied and exits the end of cathode flow fields 111. Cathode manifold 105 supplies compressed reactant air, and it is via cathode manifold 105 reactant air exits cathode plate 101 and the fuel cell board 200 as a whole. The air comes from the atmosphere i.e. outside of the fuel cell, but it enters the fuel cell system via an air compressor (as opposed to a fan as may occur in later embodiments). This enables higher pressures of air to be achieved, although there is an increased parasitic energy cost to operate such a compressor over a fan.

Heat exchange fluid manifold 107 and anode manifold 109 are also visible in FIG. 4, and are also drilled or routed into the plates after lamination. Anode manifold 109 supplies reactant hydrogen, and it is via anode manifold 109 reactant hydrogen leaves anode plate 102 and the fuel cell board 200 as a whole. Heat exchange fluid manifold 107 and cathode manifold 105 are also visible in FIG. 4, also drilled into the plates after lamination. These supply cathode reactant fluid and a heat exchange (e.g. coolant) fluid to the fuel cell board 201.

Generally, for all embodiments herein, manifolds of any appropriate size, dimension and shape supply and collect the reactants and heat exchange fluids, or any other relevant substances, into and out of the inlets and outlets of fuel cell boards. Vertical channels up and down fuel cell stacks are connected to manifolds along the two opposed edges of the stack, which supply and collect the reactants, heat exchange fluids etc. to and from boards.

The plates may also have holes drilled or routed for bolting holes, and/or alignment pins can be inserted into these.

Fluid path', 'fluid channel', 'flow path', 'fluid flow path"fluidic path', 'flow field' and 'channel' may all be used interchangeably herein and may be substituted for one another herein. They all refer to means by which fluids can flow or travel along, down or through. Fluids may be substantially directed, either with or without assistance, along fluid flow paths, channels or the like.

FIG. 5 shows a possible electron pathway in a segmented active area of a fuel cell zo board. This shows how MEAs can be connected in series across a fuel cell board 70. Such PTHs could not be used when MEAs are connected in parallel. Fuel cell board 70 has two MEAs shown, each with an anode 72 and a cathode 74. Each fuel cell board can have multiple MEAs connected in this manner, this just shows two of a possible multiple. Anodes 72 and cathodes 74 sandwich ion permeable membranes 71. Arrow 76 shows the path of current laterally across the fuel cell board 70. The current first flows from the anode 72 to the copper plating 76 on the upper surface of the board 70 via the plated through holes 80. The current flows across the copper layer 76 on the upper surface of the board, down the plated through hole 82 and along the copper layer 76 on the lower surface of the board. The electrons will then flow through the plated through holes 80 to the cathode 74 on the right side of the board. Four plated through holes 80 are labelled for each MEA, two each side of ion permeable membrane 71. 11 plated through holes 80 are shown for each MEA.

FIG. 5 demonstrates how current can flow laterally across a fuel cell board when the MEAs are segmented, as described herein. These MEAs are in series with each other.

FIG. 5 demonstrates two types of plated through holes -labelled 80 and 82. Firstly plated through holes 80 which only go pass through (and provide a current pathway through) part of or one layer of insulating material, from one surface of the fuel cell board to the anodes or cathodes. These are labelled 80 In FIG. 5. Secondly plated through holes 82, those which pass through (and provide a current pathway through) the whole fuel cell board, from one surface of the fuel cell board all the way through to the other surface of the fuel cell board. This will be through the at least two insulting layers of insulating material, both the anode and cathode plate. In some arrangements (not shown here), these may go through anodes, cathodes and the ion permeable membranes of MEAs. These are labelled 82 In FIG. 5.

In operation, a fuel cell can be enclosed in a housing and is sealed from the atmosphere. Reactants are fed into the fuel cell channels through sealed connections. Seals may, for example, be made of Polydimethylsiloxane (PDMS). In particular, fuel (e.g. H2) and oxidant (e.g. air) are fed into appropriate fluid channels of the fuel cell stack, with fuel being supplied to the anodes and oxidant to the cathodes. The electrical current thus formed can be taken directly or the output of the fuel cell board. A constant power output of the stack may be achieved in a variety of ways. For example, all fuel cell boards may be loaded at all times. Alternatively, the fuel cell boards may be divided into groups and these groups may be "switched on" in turn in a synchronous manner (i.e. switching occurs at a defined time for all fuel cell boards). The fuel cell boards may also be switched in an asynchronous or quasi-asynchronous manner -i.e. each fuel cell board is connected and disconnected to the load for a defined period and frequency individually specified for each fuel cell board. By switching the fuel cell boards so that they are only connected to the load for a proportion of the time according to a duty cycle, the output power of the stack can be continuously modified. For example, if over a given sample period of time only 50% of the fuel cell boards are connected to the load, then the output power of the fuel cell stack will be similarly reduced. The manner in which this 50% is achieved may be brought about in a multitude of ways -for example half of the fuel cell boards may be disconnected from the load and half connected for the entire period; alternatively all fuel cell boards may be connected to the load, but each connected for only half of the sample period. Alternatively again, half of the fuel cell boards may be connected to the load for one quarter of the sample period, and the other half for three quarters of the sample period etc. The choice of the specific scheme or duty cycle used may depend on the performance of individual fuel cell boards, the need to avoid localized heating or 'hot spots', the need to avoid flooding of cathode sites with product water, the need to prevent dehydration of the membrane, or the need to counteract poisoning of the electrodes. It will be noted that the duty cycle may be predetermined or may be controlled in real time based on monitored performance of the fuel cell, for example in a closed feedback loop with a voltage measuring apparatus. Part-time use of fuel cell boards may also improve efficiency as one can achieve optimum load conditions and power conversion for each individual fuel cell board rather than for the fuel cell stack which is a limitation of current designs. By including additional switching and filtering components on the fuel cell boards, a smoothly varying output, for example a sinusoidal wave, may be obtained, in addition to simple "changeovers" or steps from one potential to another.

Each fuel cell board can carry its own electronic circuitry, with each module feeding the power into an electrical bus. That is, each board contains its own power electronics and controller. The latter monitors the performance of the fuel cell electrodes, local humidity and temperature. It can also control the shape memory alloy (SMA) valves to throttle the flow of reactant to the electrodes on that board, as described in more detail below. Thus the power electronics can be put directly onto each horizontal board. In this manner, the status of each electrode can be monitored for degradation. This information gives feedback to enable the electronics to be modulated so a particular board of electrodes can be used less, thereby slowing the degradation process, or by completely shutting down a board of electrodes. This control enables the protection of underperforming boards, thereby increasing the longevity of the entire fuel cell stack.

FIG. 7 shows how fuel cell stacks can be tailored to have the same power output but at a different voltage, depending on the requirements. In FIG. 7 experimental modelling shows two examples of systems in different configurations delivering the same amount of maximum power. System A (represented by dots and crosses, voltage represented by crosses and power represented by dots) is a fuel cell stack comprising 20 cells each with an area of 100 cm2, whilst System B (represented by squares and triangles, voltage represented by triangles and power represented by squares) is a fuel cell stack where a fuel cell board comprising 10 cells each with an area of 200 cm2. In System A, where a higher voltage maybe required for the application, the fuel cell are connected in series to maximise the cumulative voltage of 18V, delivering a maximum stack current of 100A. Whereas in System B, the cumulative voltage of the stack is lowered to 10V by switching the connection of the fuel cell from series to parallel, whilst the current is increased to 210A to maintain the power constant. System A has a higher voltage but delivers a lower current, system B has a lower voltage but delivers a higher current. This demonstrates how changing the cell segmentation can affect the electrical properties of a fuel cell stack.

Figures 8a, 8b, 8c and 8d show modelling of segmented fuel cell boards. For all, the x axis shows the spatial coordinates across a modelled fuel cell board, so 10 individual MEAs are visible for each of the four graphs, each line representing a different MEA at eight different currents (0.1 A/cm2 to 1.6 A/cm2).

These figures compare the cathode potential for two differently segmented MEA fuel cell boards operating under otherwise identical conditions, run at a relatively low humidity. The anode inlet as a 50% relative humidity and the cathode inlet is at a 10% humidity.

Figure 8a shows oxygen saturation (partial pressure) plotted against spatial coordinates and Figure 8b shows water activity (relative humidity) plotted against spatial coordinates, both at the cathode catalyst layer. These two graphs are for a segmented module where all the segments are experiencing the same current density, because all segments are the same size.

There is a predictable distribution shown, which indicates a predictable reduction in oxygen saturation and a predictable increase in humidity across a fuel cell board.

Figure 8c shows electrical potential plotted against spatial coordinates and Figure 8d also shows electrical potential plotted against spatial coordinates, both at the cathode catalyst layer. These two graphs are for a segmented module, however FIG. 8c is for a fuel cell module where all segments of the fuel cell are the same size, whilst FIG. 8d is for a fuel cell modules where all the segments are experiencing a different current density, because the segments are a varying size across the fuel cell board.

FIG. 8d, compared to FIG. 8c, shows that there is much less of a variance in potential across the fuel cell board when the MEA segmentation varies across the fuel cell board. This demonstrates that varying the size of the MEAs can decrease the variance in potential across the fuel cell board, flattening the voltage and making voltage more predictable. A more consistent voltage is maintained across the varying segmented fuel cell board.

Comparing Figures 8c and 8d show that there is an improvement in performance (4.65 V versus 4.60 V) particularly at 1.6 A/cm2.

Herein the construction of the fuel cell boards and the fuel cell stack is described herein in terms of 'horizontal' and 'vertical' planes, in accordance with the embodiments illustrated in the Figures. However, these terms are used for clarity only, and are not limiting on the scope of the invention. It will be clear to the reader that the fuel cell boards can be arranged in any plane, not just the horizontal plane. Further, the term 'directly opposite' is not limited to the electrodes being in register. The anode lies on one face of the polymer electrolyte and lies directly opposite a cathode on the opposite face of the same electrolyte membrane layer.

A fuel cell stack 30-1 of the of an embodiment is shown in FIG. 6. The fuel cell stack 30-1 is encased in a fuel cell casing with end plate 31 visible. Present in this embodiment are eleven liquid coolant plates 300 and ten fuel cell boards 200. The fuel cell has two cathode inlet/outlets 32, two coolant inlet/outlets 33 and two anode inlets/outlets 34.

Cathode inlets 32 will be connected to a compressed air compressed air canister or an air compressor to supply compressed air to act as an oxidant to react at the cathodes in fuel cell operation. Cathode outlets 32 will be connected to an exhaust to the atmosphere. Sometimes cathode outlets 32 will be connected to an exhaust via a humidifier such that the water produced in the fuel cell can be used to humidify the air going into the stack. This is achieved via passing the incoming and outgoing fluids over a water permeable membrane.

Anode inlets 34 will be connected to a hydrogen cannister, to supply hydrogen reactant to the anodes to act as a reducible gas in order to fuel the fuel cell operation. Anode outlets 34 will be connected to an exhaust to the atmosphere or an anode recirculation system.

An anode recirculation system can comprise a water trap (to remove accumulated water) and a hydrogen pump or orifice which increases pressure such that any unused hydrogen can be put back into the stack.

Endplates 32 act to compress the fuel cell and to seal it, to prevent any fluid leakage in operation. Fuel cells are bolted together to ensure compression.

Use of a sealing materials such as prepreg, and the use of insulating plates, such as PCBs ensures that the MEA is sealed from anything not deliberately directed to the components of the MEA by the channels in the boards (e.g. anode and cathode plates) directly adjacent to the MEA5. This is an advantage of the herein described technology, it allows quick, simple and cheap construction of such structures. Use of lamination with for example an epoxy resin prepreg also maintains compression of the gas diffusion layer of the MEAs, an important component in maintaining fuel cell performance, providing a sufficiently low resistance electrical path without compromising distribution of reactant fluids.

Boards which are laminated with a specific lamination process, involving careful pre-cutting and alignment of materials, along with bespoke heating, cooling, pressure and washing cycles.

Once fuel cell boards 200 of this embodiment are constructed, they can be made into fuel cell stacks. These are modular and made of two components, the fuel cell boards 200 and the thermal management plates 300. Stacks begin and terminate with an endplate which provides compression through the stack as well as sealed ports to connect fuel, oxidant, and thermal management fluid. Means to remove excess current can also be used at either end of the stack to take off the significantly high current when necessary. A stack can be built with a repetitive sequence of and fuel cell boards 200, with possible addition of heat exchange plates 300. The stacks shown throughout may be held together with bolts, or compression bands, which also provide compression for the seals between modules, however any means to hold stacks together compressed, or any means to seal fuel cell boards, possible heat exchange plates, or modules together, and end plate types known in the art, may be utilised. Gaskets to seal manifolds or other parts of the fuel cell stack together can be used, if necessary, but may not be necessary in such a stack.

Reference herein to "heat exchange fluid", "thermal management fluid" or a "temperature control fluid", interchangeable herein, refers to a fluid which can be used in a fuel cell or a component for a fuel cell or other such electrochemical device which can flow near or flow adjacent or flow to contact one or more portions of the fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein. For example, the systems and methods herein can allow a heat exchange fluid to flow through a flow path adjacent or near the anodes of a fuel cell board, acting to cool or heat those anodes.. These can act to cool components, for example cool anodes of a fuel cell whilst the fuel cell functions. Or, such heat exchange fluids can act to heat or warm components, for example to heat up an anode component of a fuel cell at the point of fuel cell start up, early in a fuel cell operation timeline/program or in low temperature environments. Heat exchange fluids can be liquids, gases or other such suitable fluids as described herein. Heat or temperature can be added or removed from various parts of the fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein.

The heat exchange fluid may contact one or more portions of the fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein. For example, the systems and methods herein can allow a heat exchange fluid to flow through a flow path adjacent or near the anodes of a fuel cell board, acting to cool those anodes.

Thermal management or heat exchange may be to maintain the fuel cell board or stack at a certain operating temperature, to operate the system in a more energy efficient manner, to increase the operating lifetime of the system, and/or to provide more efficient fuel cell operation (e.g. allowing a fuel cell to operate within set parameters, not leading to over production or under production of power).

All heat exchange fluids known to those of skill in the art would be suitable for the purposes of thermally managing or controlling the temperature of fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein.

Particularly, heat exchange fluids can be deionised water, water, or a mixture of water or deionised water and glycol to prevent freezing of the water can be used.

Other suitable heat exchange fluids are envisioned, and would be known to a person of skill in the art. For example, a fluid with a ratio of 1:1 deionised water to glycol (such as ethylene glycol or propylene glycol) may be used, or alternatively a ratio of 2:1 deionised water to glycol, or alternatively a ratio of 3:1 deionised water to glycol, or alternatively a ratio of 4:1 deionised water to glycol, or alternatively a ratio of 5:1 deionised water to glycol. A solution may be up to 10% glycol in deionised water, or 1% glycol in deionised water, or 2% glycol in deionised water, or 5% glycol in deionised water, or 10% glycol in deionised water, or 20% glycol in deionised water, or 30% glycol in deionised water, or 40% glycol in deionised water, or 50% glycol in deionised water. Or, a heat exchange fluid may be a mixture of another type of alcohol (for example, methanol, ethanol, isopropyl alcohol) and deionised water. A solution may be up to 10% alcohol in deionised water, or 1% alcohol in deionised water, or 2% alcohol in deionised water, or 5% alcohol in deionised water, or 10% alcohol in deionised water, or 20% alcohol in deionised water, or 30% alcohol in deionised water, or 40% alcohol in deionised water, or 50% alcohol in deionised water. Coolant fluid may also comprise one or more perfluoroamines, such as FluorinertTM. Any water described as deionised throughout may also cover non-deionised water, and vice versa.

Insulating layers, within a single insulating layer, could have multiple different fluid paths, or channels, of different sizes, shapes and/or dimensions, or fluids at different flow rates or different fluid temperatures. Fluids could be at different temperatures or different flow rates in different plates, or at different temperatures or at different flow rates in different flow paths within the same plate. When multiple thermal management plates are present in a fuel cell stack, each plate may have different fluid paths, different sized, shaped or dimensioned fluid paths or be designed to carry different fluids. Different plates could carry different temperature fluids, or fluids with different flow rates, depending on varying thermal management fluid need throughout the stack.

The reactant fluid may be oxygen gas, air or pressurised air or any other suitable 30 fluid which would be oxidisable at the cathodes. As described above, the reactant fluid for the cathodes may be air draw in from the atmosphere outside the fuel cell by means of a fan or air compression device.

Reference herein to "fuel cell boards" or a "fuel cell board" refers to a membrane electrode assembly (MEA) 113 sandwiched between and a cathode plate 101 and an anode plate 102. In the present embodiments, the three layers are laminated together. Some fuel cell boards may have a cap layer 150 also as part of the laminated structure. Fuel cell boards may also be referred to as fuel cell modules herein. The use of 'fuel cell board' is not intended to limit the size, shape or arrangement of the MEA, or other components of the board. Fuel cell board is not intended to be limiting on the size, shape or dimensions of the board, it is just a term in the art to refer to the MEAs and plates described herein.

The fuel cells, fuel cell boards and components may be constructed of insulating layers, for example Printed Circuit Boards (PCB). Individual layers can be adhered together into a solid structure using an epoxy-containing glass fibre composite ("prepeg"). The MEAs may be laser bonded onto an insulating layer and then to create the fuel cell board, a plurality of boards are laminated together. The gaps between the electrodes, and the sealing achieved in these gaps by the epoxy resin, prevent separate flows from mixing, i.e. prevent air cooling, reactant and fuel flows from mixing. A simple PCB can also be used as the end board or plates in the stacks described herein.

The insulating layers of the embodiments herein can be printed circuit boards (PCBs). PCBs for the embodiments may be produced in the known way. Reference herein to 'Printed Circuit Board(s)' or 'PCB(s)' refers to a layer of insulating material comprise of one or more dielectric substrates such as an epoxy resin, for example FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM5, polytetrafluoroethylene, and G-10, preferably the insulating layer comprises FR-4, which may be laminated together with an epoxy resin prepreg. Plates or boards may comprise one or more layers of these insulating materials. In order to yield conductive areas, a thin layer of a conducting material (for example a metal, for example copper) may either be deposited, plated or applied to the whole insulating substrate and etched away (for example using a mask) to give a desired conductive pattern. Conductive material may be applied by electroplating. The PCBs described throughout may or may not be copper plated in various parts across the PCB boards.

The reactant fluid may be oxygen gas, air or pressurised air or any other suitable fluid which would be oxidisable at the cathodes. As described above, the reactant fluid for the cathodes may be air draw in from the atmosphere outside the fuel cell by means of a fan or air compression device.

Reference herein to a passivating ink may refer to a conductive ink, particularly the ink may have a functional conductive element that is carbon based. The ink acts to provide a low through-plane resistance conductive path between the electrode and the current collector while protecting the copper from the corrosive environment of the fuel cell. It does this by passivating any migratory copper which would otherwise cause irreversible damage of the electrolyte/membrane. Further, the ink may be a carbon ink, it may be a silver paste and polyurethane based ink with conductive elements dispersed in it such as carbon nanotubes or gold/silver nanoparticles these and other inks will be known to a person of skill in the art.

In operation, the fuel cell is enclosed in a housing and is sealed from the atmosphere. Reactants are fed into the fuel cell channels through sealed connections. Seals may, for example, be made of Polydimethylsiloxane (PDMS). In particular, fuel (e.g. H2) and oxidant (e.g. 02) are fed into appropriate channels of the fuel cell stack, with fuel being supplied to the anodes and oxidant to the cathodes. The electrical current thus formed can be taken directly or the output of the fuel cell board can be modulated utilising the aforementioned switch. A constant power output of the stack may be achieved in a variety of ways. For example, all fuel cell boards may be loaded at all times. Alternatively, the fuel cell boards may be divided into groups and these groups may be "switched on" in turn in a synchronous manner (i.e. switching occurs at a defined time for all fuel cell boards). The fuel cell boards may also be switched in an asynchronous or quasi-asynchronous manner -i.e. each fuel cell board is connected and disconnected to the load for a defined period and frequency individually specified for each fuel cell board. By switching the fuel cell boards so that they are only connected to the load for a proportion of the time according to a duty cycle, the output power of the stack can be continuously modified. For example, if over a given sample period of time only 50% of the fuel cell boards are connected to the load, then the output power of the fuel cell stack will be similarly reduced. The manner in which this 50% is achieved may be brought about in a multitude of ways -for example half of the fuel cell boards may be disconnected from the load and half connected for the entire period; alternatively all fuel cell boards may be connected to the load, but each connected for only half of the sample period. Alternatively again, half of the fuel cell boards may be connected to the load for one quarter of the sample period, and the other half for three quarters of the sample period etc. The choice of the specific scheme or duty cycle used may depend on the performance of individual fuel cell boards, the need to avoid localized heating or 'hot spots', the need to avoid flooding of cathode sites with product water, the need to prevent dehydration of the membrane, or the need to counteract poisoning of the electrodes. It will be noted that the duty cycle may be predetermined or may be controlled in real time based on monitored performance of the fuel cell, for example in a closed feedback loop with the voltage measuring apparatus described above. Part-time use of fuel cell boards may also improve efficiency as one can achieve optimum load conditions and power conversion for each individual fuel cell board rather than for the fuel cell stack which is a limitation of current designs.

By including additional switching and filtering components on the fuel cell boards, a smoothly varying output, for example a sinusoidal wave, may be obtained, in addition to simple "changeovers" or steps from one potential to another.

It will be appreciated that aspects of the invention can be interchanged or zo juxtaposed as appropriate. The fuel used is not restricted to hydrogen, but may be any suitable fuel. For example, the new geometry fuel cell stack described herein is also applicable to methanol used in Direct Methanol fuel cells. Other fuel cell types would be known in the art and can use the arrangements and components as described herein, they are not limited to hydrogen fuel cells.

Although the invention as exemplified uses hydrogen as the reactant fuel (i.e. the reducible gas for the anodes), the fuel cells could be used with all suitable pressurised fluids. As used herein "fluid" refers to a substance that has no fixed shape and yields easily to external pressure, for example a gas or a liquid. Fuels for use with the systems and methods as described herein are fluids. These fuels can be hydrogen or a hydrogen-containing mixture, or a hydrocarbon or hydrocarbon derivative. Fuels could be other gaseous fuels, such as methane or propane. Fuels could be other gaseous fuels, such as methane or propane and fluids include oxidants such as air and oxygen.

The fuel cells and fuel cell boards described herein can be capable of, any envisioned power output for a fuel cell stack. Each fuel cell board may have a power rating of at least 100W. Each fuel cell board may have a power rating of up to 1000W. Each fuel cell board may have a power rating of 10W to 1000W. A fuel cell comprising multiple fuel cell boards may have a power rating of at least 10kW.

Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of up to 1000kW. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of 10kW to 1000kW. But, any power rating is merely representative of current embodiments, and the rating may vary from these described as just exemplary.

The systems and methods can be used with pressurised fuel storage units or containers, as are well known in the art. The fuel can be stored in a pressurised storage unit, for example a bottle or canister. These can be, for example at a pressure of between 700 and 300 bar.

The systems and methods can be used with pressurised fuel storage units or containers, as are well known in the art. The fuel can be stored in a pressurised storage unit, for example a bottle or canister. These can be, for example at a pressure of between 700 and 10 bar. In particular the fuel storage units can be suitable for use with fuel cells as described herein, i.e. at a pressure of between zo 150 and 350 bar.

It will be clear to one skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present disclosure.

Claims

CLAIMS1. A fuel cell comprising: at least one fuel cell board, wherein each fuel cell board comprises: at least one first insulating layer; at least one ion permeable membrane; and multiple anodes and multiple cathodes; wherein all cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface opposing the first surface of the ion permeable membrane; wherein at least one material property of the anodes or the cathodes or the size of the anodes or the size of the cathodes varies or changes across the fuel cell board; and/or wherein at least one material property of another component of the fuel cell board varies or changes across the fuel cell board.
2. A fuel cell comprising: at least one fuel cell board, wherein each fuel cell board comprises: at least one first insulating layer; at least one ion permeable membrane; and multiple anodes and multiple cathodes; wherein all cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface opposing the first surface of the ion permeable membrane, wherein pairs of anodes and cathodes across the at least one ion permeable membrane are electrically connected in parallel with adjacent pairs of anodes and cathodes.
3. The fuel cell of claim 1, wherein pairs of anodes and cathodes across the at least one ion permeable membrane are electrically connected in parallel with adjacent pairs of pairs of anodes and cathodes.
4. The fuel cell of claim 2, wherein at least one material property of the anodes or the cathodes or the size of the anodes or the size of the cathodes varies or changes across the fuel cell board; and/or wherein at least one material property of another component of the fuel cell board varies or changes across the fuel cell board.
5. The fuel cell of any preceding claim, wherein the fuel cell board comprises means configured to supply the cathodes with an oxidisable fluid and wherein the fuel cell board comprises means configured to supply the anodes with a reducible fluid, optionally wherein the means to supply the cathodes with an oxidisable fluid is an insulating layer comprising at least one first fluid path, and/or optionally wherein the means configured to supply the anodes with a reducible fluid is an insulating layer comprising at least one first fluid path, optionally wherein the at least one first insulating layer comprises at least one first fluid path and is either the means configured to supply the cathodes with an oxidisable fluid or is the means configured to supply the anodes with a reducible fluid.
6. The fuel cell of any preceding claim, wherein the anodes increase in size or decrease in size across the first surface of the ion permeable membrane; and/or wherein the cathodes increase in size or decrease in size across the second surface of the ion permeable membrane.
7. The fuel cell of any preceding claim, wherein the anodes and/or the cathodes have a smaller size where the conditions the fuel cell board are subjected to are more favourable, and/or wherein the anodes and/or the cathodes have a larger size where the conditions the fuel cell board are subjected to are less favourable.
8. The fuel cell of claim 6 or claim 7, wherein at least one the cathode has a smaller size at the edge of the fuel cell board where an oxidisable fluid is first supplied to the cathodes; and/or wherein at least one the anode has a larger size at the edge of the fuel cell board where a reducible fluid is first supplied to the anodes.
9. The fuel cell of any preceding claim, wherein an oxidisable fluid is initially supplied to the cathodes of the fuel cell board in a direction substantially opposite to direction in which a reducible fluid is initially supplied to the anodes of the fuel cell board.
10. The fuel cell of any of the preceding claims, wherein the at least one anode and or cathode material property which varies is at least one of: i) at least one of the material the anodes and/or the cathodes comprise, or at least one of the additive materials provided to or with the anodes and/or the cathodes; ii) the coating of the anodes and/or the cathodes; and/or iii) the composition, material properties of, location or size of a catalyst layer on or with each of the cathodes and/or each of the anodes, optionally wherein the composition of the catalyst layer comprises at least one of the ionomer content, catalyst loading or catalyst type.
11. The fuel cell of any of the preceding claims, wherein the fuel cell board comprises means to conduct current from one face of the fuel cell board to the other face of the fuel cell board, optionally wherein the means are plated through holes, and/or wherein the fuel cell board comprises means to conduct electrical current from the anodes through the at least one insulating layer to the surface of the at least one first insulating layer, and wherein the fuel cell board comprises means to conduct electrical current to the cathodes through the at least second insulating layer from the surface of the at least one second insulating layer, optionally wherein the means are plated through holes.
12. The fuel cell of any of the preceding claims, wherein the first insulating layer comprises at least one first fluid path.
13. The fuel cell of claim 12, wherein the first insulating layer comprises multiple first fluid paths and wherein the multiple first fluid paths are substantially parallel to each other.
14. The fuel cell of any of the preceding claims, wherein the fuel cell board comprises a second insulating layer wherein the first insulating layer comprises at least one first fluid path and; wherein the second insulating layer comprises at least one second fluid path; wherein the at least one ion permeable membrane and the multiple anodes and the multiple cathodes are located between the first insulating layer and the second insulating layer so that the at least one first fluid path is arranged such that an oxidisable fluid can be supplied to one or more of the cathodes of the at least one fuel cell board and so that the at least one second fluid path is arranged such that a reducible fluid can be supplied to one or more of the anodes of the at least one fuel cell board; and wherein the MEA, the first insulating layer and the second insulating layer are laminated together to form the fuel cell board.
15. The fuel cell of claim 14, wherein the first insulating layer comprises multiple first fluid paths and wherein the multiple first fluid paths are substantially parallel to each other; and/or wherein the second insulating layer comprises multiple second fluid paths and wherein the multiple second fluid paths are substantially parallel to each other.
16. The fuel cell of any preceding claim, wherein the first insulating layer is a printed circuit board (PCB), optionally wherein any further insulating layers are also PCBs.
17. The fuel cell of any preceding claim, wherein the fuel cell comprises a plurality of fuel cell boards, wherein each fuel cell board is arranged such that the cathodes of each fuel cell board face the anodes of the adjacent fuel cell board and wherein each fuel cell board is arranged such that the anodes of each fuel cell board face the cathodes of the adjacent fuel cell board.
18. The fuel cell as claimed in any one of the preceding claims, wherein the fuel cell board has a power rating of between 10W and 1000W, and/or the fuel cell has a power rating of between 10kW and 1000kW.
19. The fuel cell of any preceding claim, wherein the lamination is achieved by chemical bonding by heating layers of prepreg between the insulating layers under pressure and an increased temperature.
20. The use of a fuel cell of any preceding claim.
21. A method of controlling fuel cell voltage, the method comprising operating a fuel cell comprising at least one fuel cell board, the at least one fuel cell board comprising multiple Membrane Electrode Assemblies (MEAs), wherein the fuel cell board comprises: at least one insulating layer; at least one ion permeable membrane; and multiple anodes and multiple cathodes; wherein all cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface of the ion permeable membrane to form the multiple MEAs on a single fuel cell board; wherein each MEA is electrically connected in parallel with each or both or all adjacent MEAs, the method comprising operating the fuel cell when each MEA is electrically connected in parallel with each or both or all adjacent MEAs.
22. The method of claim 21, wherein the connection between each MEA is individually switchable between parallel connection and series connection.
23. The method of claim 21 or claim 22, wherein at least one material property of the anodes or the cathodes or the size of the anodes or the size of the cathodes varies or changes across the fuel cell board; and/or wherein at least one material property of another component of the fuel cell board varies or changes across the fuel cell board.
24. A method of controlling fuel cell voltage, the method comprising operating a fuel cell comprising segmented MEAs on a single fuel cell board, wherein the segmented MEAs are connected in parallel with each other.
25. Use of segmented MEAs on a single fuel cell board and use of parallel connections between these segmented MEAs in a fuel cell.