FUEL CELL UNIT AND FUEL CELL STACK

Abstract

A metal-supported, SOEC or SOFC fuel cell unit (10) comprising a separator plate (12) and metal support plate (14) with chemistry layers (50) overlie one another to form a repeat unit, at least one plate having flanged perimeter features (18) formed by pressing the plate, the plates being directly adjoined at the flanged perimeter features to form a fluid volume (20) between them and each having at least one fluid port (22), wherein the ports are aligned and communicate with the fluid volume, and at least one of the plates has pressed shaped port features (24) formed around its port extending towards the other plate and including elements spaced from one another to define fluid pathways to enable passage of fluid from the port to the fluid volume. Raised members (120) may receive a gasket (34), act as a hard stop or act as a seal bearing surface.

Claims

1. A metal-supported solid oxide fuel cell unit comprising: a separator plate; and a metal support plate carrying fuel cell chemistry layers provided over a porous region; the separator plate and the metal support plate overlying one another to form a repeat unit; wherein: at least one of the separator plate and the metal support plate comprises flanged perimeter features formed by pressing the plate to a concave configuration; the separator plate and the metal support plate are directly adjoined at the flanged perimeter features to form a fluid volume therebetween; at least one fluid port is provided in each of the separator plate and the metal support plate within the flanged perimeter features, the respective fluid ports being aligned and in communication with the fluid volume; and at least one of the separator plate and the metal support plate is provided with shaped port features formed around its port by pressing, which shaped port features extend towards the other plate, and elements of the shaped port features are spaced from one another to define fluid pathways between the elements from the port to enable passage of fluid from the port to the fluid volume.

2. A metal-supported fuel cell unit according to claim 1, wherein the fuel cell chemistry layers take the form of an electrochemically active layer comprising an anode, an electrolyte and a cathode formed onto the metal support plate over the porous region that is provided within the metal support plate.

3. A metal-supported fuel cell unit according to claim 1, wherein the porous region is provided on a separate plate over which the fuel cell chemistry layers, taking the form of an electrochemically active layer comprising an anode, an electrolyte and a cathode, are formed, and the separate plate is provided over a window on the metal support plate.

4. A metal-supported fuel cell unit according to claim 1, wherein the fluid pathways from the fluid port to the fluid volume are tortuous and/or cross one another at a plurality of locations.

5. A metal-supported fuel cell unit according to claim 1, wherein the flanged perimeter features are only provided on the separator plate.

6. A metal-supported fuel cell unit according to claim 1, wherein the shaped port features are only provided on the separator plate.

7. A metal-supported fuel cell unit according to claim 1, wherein the shaped port features are the same height above the surface from which they extend as the distance between opposed inner surfaces of the two plates.

8. A metal-supported fuel cell unit according to claim 1, wherein at least one of the separator plate and the metal support plate is provided with one or a plurality of raised members formed by pressing, that extend away from the other plate and that are arranged around the or each fluid port.

9. A metal-supported fuel cell unit according to claim 8, wherein there are a plurality of raised members so arranged to define a space for accommodating a gasket within the raised members and/or a plurality of raised members so arranged to define a perimeter for accommodating a gasket outside of the raised members.

10. A metal-supported fuel cell unit according to claim 8, wherein there are a plurality of raised members interspersed amongst the shaped port features.

11. A metal-supported fuel cell unit according to claim 8, wherein the or each raised member is positioned outside of the shaped port features.

12. A metal-supported fuel cell unit according to claim 8, wherein the or each raised member of the one or a plurality of raised members has a peak that defines a hard stop surface against which an adjacent fuel cell unit, or a part extending therefrom, can bear during assembly of a stack of the cell units.

13. A metal-supported fuel cell unit according to claim 12, wherein there are multiple raised members defining hard stop surfaces and the hard stop surfaces all lie in a common plane.

14. A solid oxide fuel cell stack comprising a plurality of fuel cell units each according to claim 1, the fuel cell units being stacked upon one another with seals around the fluid ports between adjacent fuel cell units, the seals optionally overlying the shaped port features.

15. The fuel cell stack according to claim 14, wherein the seals comprise one of gaskets and in situ seals.

16. (canceled)

17. The fuel cell stack according to claim 1, wherein at least one of the separator plate and the metal support plate is provided with one or a plurality of raised members formed by pressing, that extend away from the other plate and that are arranged around the or each fluid port, wherein the or each raised member of the one or a plurality of raised members has a peak that defines a hard stop surface against which an adjacent fuel cell unit, or a part extending therefrom, can bear during assembly of a stack of the cell units, wherein the at least one seal that sits on a seal receiving surface of a lower one of the fuel cell units has a height above that seal receiving surface before the next fuel cell unit is stacked thereon, and the hard stop surface of the lower one of the fuel cell units has a height that is located above that seal receiving surface but below the height of the seal that sits on the seal receiving surface so as to provide a limit to compression between the adjacent fuel cell units.

18. The fuel cell stack according to claim 1, wherein at least one of the seals is positioned partially in a groove that surrounds a respective fluid port for that seal, the groove being optionally located in a raised portion of the plate.

19. The fuel cell stack according to claim 1, wherein the internal components of the fuel cell stack comprises only the stack of cell units and the seals, the seals optionally overlying the shaped port features around the respective fluid ports.

20. The fuel cell stack according to claim 1, wherein the pressed shaped port features define concave pores on the outer surface of the plate in which they are formed, which pores of each set of shaped port features are covered by one of the seals, the pores optionally being located in a raised portion of the plate.

21. A method of manufacturing a metal-supported solid oxide fuel cell unit, the method comprising the steps of: providing a separator plate; providing a metal support plate; and processing at least one of the metal support plate and the separator plate to form: flanged perimeter features; at least one fluid port within the separator plate and the metal support plate; and shaped port features formed around at least one of the at least one fluid ports, the processing comprising at least pressing of the plate or plates to form the flanged perimeter features to form a concave configuration in the plate or plates, and likewise pressing the shaped port features; the method further comprising: overlying the separator plate and the metal support plate over one another to form a repeat unit; directly joining the separator plate and the metal support plate at the flanged perimeter features, wherein the flanged perimeter features that form the concave configuration form a fluid volume therebetween, wherein the shaped port features extend towards the other plate, and elements of the shaped port features are spaced apart from one another to provide fluid pathways from the port to the fluid volume, and optionally, wherein the fluid ports are cut before the pressing of the plate or plates to form the flanged perimeter features.

22. (canceled)

Description

[0081] These and other features of the present invention will now be described in further detail, by way of various embodiments, and just by way of example, with reference to the accompanying drawings (which drawings are not to scale, and in which the height dimensions are generally exaggerated for clarity), in which:

[0082] FIG. 1 shows a plan view of a metal-supported fuel cell unit comprising a first embodiment;

[0083] FIG. 2 shows a first perspective view of the fuel cell of FIG. 1, with two gaskets positioned below it;

[0084] FIG. 3 is a second perspective view of the arrangement in FIG. 2, shown from a different angle;

[0085] FIG. 4 is an opposite plan view from FIG. 1 of the fuel cell unit with the gaskets shown located over fluid ports of the fuel cell unit;

[0086] FIG. 5 shows a section through the fuel cell unit;

[0087] FIG. 6 shows a section through the fuel cell unit, and the gaskets, as they would be during compression of a stack of fuel cell units during assembly thereof;

[0088] FIG. 7 shows an exploded perspective view of a stack of two fuel cell units, each fuel cell unit being provided with two gaskets underneath them;

[0089] FIG. 8 shows the stack of FIG. 7, but not exploded, with the two cell units stacked over each other with the first pair of gaskets in-between them, and the two further gaskets positioned below the stack for stacking onto a further fuel cell unit (not shown);

[0090] FIG. 9 shows, in plan view, an alternative fuel cell unit, comprising a second embodiment. It is similar to the first fuel cell unit but has flanged perimeter features added to the visible part of the metal support plate of the fuel cell unit, around its fluid ports, rather than just around fluid ports on the separator plate of the fuel cell unit;

[0091] FIG. 10 is a perspective view of the fuel cell unit with two gaskets positioned below it, one for each fluid port;

[0092] FIG. 11 is a second perspective view of the arrangement of FIG. 10;

[0093] FIG. 12 is a bottom plan view of the arrangement in FIGS. 11 and 10;

[0094] FIGS. 13 and 14 are sections through the assembled fuel cell units, with gaskets where applicable, with FIG. 14 showing force indicators to show the compression during stacking, as per FIG. 6;

[0095] FIGS. 15 to 17 show stacking of the second embodiment, which is similar to that of the first embodiment, albeit with the different shaped port features' arrangement;

[0096] FIGS. 18 to 26 show a third embodiment, similar to the first embodiment, but wherein the fuel cell unit has a separate part for the active fuel cell component—which has the electrochemically active layers therein, the metal support plate of the fuel cell unit being provided with a window. Otherwise, the arrangement in these figures is similar to that of the first embodiment;

[0097] FIGS. 27 to 35 are similar to that of FIGS. 18 to 26 but instead show a fourth embodiment which has shaped port features in the metal support plate as well as the separator plate, much like the second embodiment;

[0098] FIG. 36 shows a fifth embodiment of the present invention in which the outer shape of the fuel cell unit has been changed to provide two fluid ports at each end of the fuel cell, rather than the single one as in the first embodiment;

[0099] FIG. 37 shows in more detail a corner of the product of FIG. 36, in which the shaped port features are more clearly visible;

[0100] FIG. 38 shows a sixth embodiment of the present invention in which the fifth embodiment is adapted to include a pair of windows in its metal support plate to align with two separate electrochemically active fuel cell components;

[0101] FIG. 39 shows an alternative arrangement for the fuel cell unit wherein the separator plate of the fuel cell unit has a returning flanged perimeter feature extending back from the flanged perimeter feature to put the edge of the separator plate back in plane with the majority of the separator plate, such that the flanged perimeter feature for forming a fluid volume in the fuel cell is a ridge; the corners of the cell unit are also rounded off;

[0102] FIG. 40 shows a full stack of fuel cell units clamped together, with power take-offs for enabling use of the fuel cell as an electrical supply for a load (L);

[0103] FIG. 41 shows a perspective view of a stack of cell units before compression into a fuel cell stack;

[0104] FIG. 42 shows an exploded view of a prior art fuel cell unit, from WO2015/136295, comprising a metal support plate and a separator plate, much like the present invention, but additionally comprising a spacer plate;

[0105] FIGS. 43 and 44 show a variant to that of FIG. 37, with FIG. 43 being a partial view in plan and FIG. 44 being a partial view in perspective, both showing a corner of a product with a gasket for overlying shaped port features around a fluid port;

[0106] FIGS. 45 and 46 show the variant of FIGS. 43 and 44 in section, FIG. 46 being an enlarged view of part A of FIG. 45;

[0107] FIGS. 47 to 50 show similar views of another variant, again with a gasket and shaped port features around a fluid port, with added hard stop features; and

[0108] FIGS. 51 to 54 show similar views of yet another variant, again with shaped port features around a fluid port, but using an insitu seal, rather than a conventional washer-type gasket.

[0109] Referring first to FIG. 2, there is shown an exploded view of a fuel cell unit of a first embodiment of the present invention, and two gaskets. This fuel cell unit 10 is oriented upside down relative to that of the prior art fuel cell unit shown in FIG. 42 as it is the inside of the fuel cell unit 10 that is of primary interest for the present invention. As can be seen, the fuel cell unit 10 comprises a flat (i.e. planar) metal support plate 14 stacked next to a separator plate 12—in this case above it. The separator plate 12 is shown to have flanged perimeter features 18 around its perimeter. This serves to render redundant the spacer plate 152 of the prior art, and is an important element of the present invention.

[0110] The flanged perimeter features 18 extend out of the predominant plane of the sheet, as found at a central fluid volume area, to create a concavity in the separator plate (and a convexity to the outside surface). The concavity will form the fluid volume 20 within this fuel cell unit upon assembly of the fuel cell unit.

[0111] In this illustrated arrangement (simplified to illustrate key features of the invention), the fuel cell unit 10 has rounded ends and parallel sides, with a fluid port 22 towards each end. Other shapes and sizes and numbers of the respective cell features are of course possible—see FIG. 37 for example—depending upon the required power and dimensions of the final stack assembly.

[0112] In a middle portion of the fuel cell unit 10, an electrochemically active layer 50 is provided on the metal support plate. In this embodiment it is located outside of the fluid volume 20.

[0113] As shown in FIG. 3, the metal support plate 14 (e.g. metal foil) is provided with multiple small holes 48 to enable fluid in the fluid volume to be in contact with the side of the electrochemical layers that is closest to the metal support plate 14. These form a porous region bounded by a non-porous region. In a preferred embodiment, the anode (fuel electrode) layer is located adjacent the small holes with the (enclosed) fluid volume 20 within the fuel cell unit comprising a fuel flow volume 20 supplied by fuel entering and exiting via the fluid ports 22, which are thus fuel ports 22. The cathode (air electrode) layer is on the opposite side of electrochemically active layer 50, i.e. on its outer face, and is exposed to air flowing across that layer during use of the fuel cell unit 10.

[0114] Both the separator plate 12 and the metal support plate 14 are provided with fluid ports 22. In this embodiment, around the fluid ports of the separator plate 12, shaped port features 24 are provided. In this embodiment, the shaped port features 24 are provided as multiple elements in the form of round dimples extending out of the plane of the base of the fluid volume 20 a distance corresponding to that of the height of the flanged perimeter features 18—to have a common height therewith. This is so that they will contact the opposing surface of the metal support plate 14, just like the flanged perimeter features 18, when the cell unit 10 is assembled. As a result, when the flanged perimeter features 18 are joined to the metal support plate 14, for example by welding, the shaped port features 24 will likewise contact the metal support plate 14.

[0115] This is important as the shaped port features 24 also provide part of the function of the spacer plate 152 that was provided in the prior art—supporting the fuel cell unit during compression together of multiple fuel cell units in a stack during assembly of the stack. They thus help to preserve the height of the fluid volume inside the fuel cell unit during that compression.

[0116] The multiple elements in this embodiment are round in section, and are substantially frusto-conical in form in that they have non-perpendicular side walls and a truncated flat top. They are pressed into the plate of the separator plate 12. Such angled walls are a preferred arrangement as an angle is easier to achieve when pressing them out of the plate from which the separator plate 12 is formed than a perpendicular wall.

[0117] However, any angle from perhaps 20 to 90 degrees can provide a useable form. Preferably it is between 40 and 90 degrees from the plane of the sheet from which it is pressed.

[0118] Usually the elements are pressed in the same step as the rest of the separator plate—i.e. the flanged perimeter features and central up projections, and downward or down projections, as discussed below.

[0119] The pressing may be any suitable method for forming a sheet into a suitable configuration, such as, for example, hydroforming or stamping/pressing. A single thin sheet can thus be used to form this part of the fuel cell unit.

[0120] Compressive forces in the stack in the vicinity of the electrochemically active layer are required for good electrical contact and hence good conductivity through the stack. Central projections 32 and central downward projections 30 create the required electrical contacts between cell units and also provide a support function for the fuel cell unit in the central region, extending upwardly to the underside of the metal support plate 14 at the area of the small holes 48, and downwardly to the opposing surface of the electrochemically active layer of a cell below it.

[0121] In this embodiment, the projections in the central region of the separator plate 12 are again circular and will typically have angled side walls as well. As per the prior art, however, they can have different shapes such as the bars of the prior art. They may have angled sidewalls like those of the shaped port regions, i.e. usually within the range 20 to 90 degrees, or more preferably between 40 and 90 degrees.

[0122] A function of these central projections and downward projections, however, is also to create respective fluid passageways, namely, fuel volume passageways and oxidant (e.g. air) volume passageways, on either side of the separator plate 12. In this case, inside the fuel cell unit, the projections create winding (e.g. tortuous) fluid passageways within the fluid volume so that fluid can pass from one fluid port 22 at one end of the fuel cell unit 10, across the active layer 50, to a fluid port 22 at the other end of the fuel cell unit 10.

[0123] That internal flow path also extends between the elements 26 of the shaped port features 24, as the elements also provide fluid passageways 28—see FIG. 5.

[0124] Seals in the form of gaskets 34 are also provided in this embodiment for the fuel cell stack between the adjacent fuel cell units 10. Examples are provided in FIGS. 2 and 3. The seals—here gaskets 34—provide a primary sealing function and will usually be compressible gaskets that are subjected to high compressive forces in the vicinity of the ports. The gaskets may be sized to cover all the shaped port features 24 of each fluid port 22 to prevent fluid that may be travelling through the fluid ports 22 in a stack from seeping between the outside of the fuel cell unit 10 and the gasket 34, into the area external of the cell units, i.e. into the fluid surrounding the fuel cell units 10, or fluid external of the fluid ports from seeping in the other direction—into the fluid ports. This is important to prevent any mixing of the fluid inside the cell unit 10 and the fluid outside the cell unit 10, which will be fuel and oxidant—the polarity of the electrochemically active layers 50 determining which way round this will be. As explained above, commonly it is fuel inside the fluid volume 20 in the fuel cell units 10, and thus in chimneys 72, 74 (see FIGS. 40 and 41) formed by the fluid ports and gaskets (which are ring-gaskets), and air or another oxidant surrounding the fuel cell units.

[0125] The gaskets may also provide electrical insulation between a first fuel cell unit 10 and an adjacent fluid cell unit 10, so as to prevent a short circuit. The gaskets may be any suitable fuel cell gaskets (sealing rings), such as, for example, thermiculite.

[0126] Referring to FIGS. 5 and 6, it can be seen how the flanged perimeter features 18, the central projections, up and down, 32, 30, and the shaped port features 24 extend out of the initial plane of the metal sheet used to form the separator plate 12 and how the gaskets 34 are diametrically sized to cover the area of the shaped port features 24 that are pressed upward out of the underside of the separator plate 12—i.e. away from the gasket 34 to leave pores. With this arrangement, when compression is provided through the cell unit 10 in the assembled stack of cell units, the shaped port features 24, along with the flanged perimeter features 18 and the central projections 30, 32, support against crushing of the fluid volume.

[0127] In the prior art, the support function of the shaped port features 24, along with the flanged perimeter features 18, was instead done by the spacer 152. In particular, the spacer ensured that the high load from the gasket compression in the vicinity of the ports was transferred to the next fuel cell unit.

[0128] Further, the creation of the internal fluid volume 20 is achieved by the flanged perimeter features 18—a feature previously provided by the spacer plate 152. However, the footprint of the original component from which the spacer was cut was large, resulting in wasted material.

[0129] Referring to FIGS. 4, 5 and 6, it can also be seen that the central upward projections 32 alternate with the central downward projections 30 in the separator plate 12. This is to allow the downward projections 30 to extend downwardly to the adjacent fuel cell's upper electrochemically active layer 50, below it. This is shown more clearly in FIGS. 7 and 8, where it can be seen that the central upward projections 32 extend upwardly to the underside of the metal support plate 14 of its own fuel cell unit 10, whereas the downward projections 30 contact the outer side of the electrochemically active layer 50 of the fuel cell unit 10 below it. This thus ensures that the adjacent fuel cell units 10 connect together like batteries in series in each stack. It also serves a beneficial function of expanding the height of the fluid volume passageways in the fluid volume.

[0130] Referring next to FIG. 8 it can be seen that adjacent fuel cell units 10 preferably have separator plates with matched opposed projections relative to one another such that the upward projections 32 on one fuel cell unit 10 align with downward projections 30 on the neighbouring fuel cell unit 10, and downward projections 30 are aligned with upward projections 32. This allows the forces of the respective projections to counter each other axially (i.e. parallel to the compression force applied to the stack during assembly). This avoids, or minimises, imparting torsional force to the electrochemically active layer 50 between the projections, thus preventing inadvertent cracking of the electrochemically active layers.

[0131] Referring next to FIGS. 9 to 17, a second embodiment of the present invention is disclosed. In this embodiment, there is still a separator plate 12 and a metal support plate 14, similar to that of the first embodiment, but the shaped port features 24 are now positioned around the fluid port 22 of both the metal support plate 14 and the separator plate 12. As such, the height of the elements in the separator plate 12 are less high than in the previous embodiment, and separate, aligned, shaped port features 24 are arranged to face downwardly from the metal support plate 14, the latter being of a height suitable to create the equivalent of the full height of the first embodiment when combined with the ones of the separator plate 12. By them aligning onto one another, the volume inside the fuel cell unit 10 is again able to be maintained, at the height of the two stacked elements, while still providing the required support for the fluid volume passageways in the vicinity of the ports where compression forces in the assembled stack are particularly high. The rest of this arrangement is unchanged compared to the previous embodiment.

[0132] Usually the two heights of the elements are intended to be different to one another, but to together create the desired total height, but they can match for achieving that total desired height.

[0133] With the arrangement of the second embodiment, the shaped port features 24 in any particular component need not be quite so high, thereby being easier to achieve when pressing them out of the sheet.

[0134] It is also possible for the shaped port features 24 only to be in the metal support plate 14, or for both to have full height and for them to intermesh, albeit while still leaving fluid pathways for fluid flow in the fluid volume.

[0135] In this second embodiment, as with the previous embodiment, the shaped port features 24, and the central up and down projections 30, 32 are all dimples having a round form.

[0136] They can have different shapes instead, but dimples are preferred as they provide a large passage for the fluid to flow through, and this is especially important for the shaped port features 24 as they are thus less likely to cause channels between the gasket and the opposite side of the member from which they are pressed through which the fluid in the port can leak into the surrounding volume of the cell unit 10, or vice versa.

[0137] Referring next to FIGS. 18 to 26, a third arrangement of the fuel cell unit 10 is provided. In this embodiment, similar to that of the first embodiment, the shaped port features 24 and the central projections, 30, 32 are all again provided in the separator plate 12, and thus the metal support plate 14 is instead generally flat or at least absent such projections, but whereas previously the metal support plate 14 had many small holes 48 in the central area with a directly overlying electrochemically active layer 50, in this embodiment the metal support plate 14 has a window 54 over which a separate electrochemically active layer component 52 will lie. Although formed separately, that electrochemically active layer component 52 will be joined to the metal support plate 14, for example by welding so that the metal support plate carries it.

[0138] The electrochemically active layer component 52 is provided with multiple small holes and a directly overlying electrochemically active layer 50 to enable fluid in the fluid volume 20 to contact the innermost electrochemical layer.

[0139] This embodiment still only involves adjoining two components at the perimeter flange features but does not require the fuel chemistry to be integrally formed with the metal support plate from the outset, which can be advantageous.

[0140] Laser welding is generally the preferred way in which the metal support plate 14, the separator plate 12 and the separate electrochemically active layer component 52, are joined to one another.

[0141] In this third embodiment, the window is rectangular. Other shapes are naturally possible for the window instead.

[0142] The electrochemically active layer component 52 normally has a similar shape to the window 54 to optimise the size of the electrochemically active layer 50 thereon, albeit bigger to overlap, as shown. This again avoids an excessive weight gain for the fuel cell unit 10.

[0143] As can be seen in FIG. 20, the electrochemically active layer component 52 has lots of small holes 48, much like those in the metal support plate 14 of the first and second embodiments. They similarly provide access to one side of the electrochemically active layer 50 thereon. Operation of this fuel cell unit in a stack is thus similar to that of the previous embodiments, and the prior art, although in this embodiment the upward projections 32 need to be higher than in the first two embodiments as they now need also to bridge the thickness of the metal support plate 14 in order to contact the underside of the small holes 48.

[0144] Referring then to FIGS. 27 to 35, a fourth embodiment is shown. In this embodiment, the arrangement is similar to that of the second embodiment but it comprises the separate electrochemically active layer component 52 as per the third embodiment. Again, therefore, the upward projections 32 are taller than in the first and second embodiments. It will be appreciated that the metal support plate 14 can be pressed, and the window 54 cut, before the fuel cell chemistry supporting electrochemically active layer component 52 is attached thereto. The window can be cut before or after the pressing, or at the same time in a press with a punch. More usually it will be laser cut from the metal support plate.

[0145] In each of these four embodiments, a preferred arrangement for the elements of the shaped port features 24 is shown. As can be seen, they take the form of circular dimples. Furthermore, the circular dimples are arranged in concentric rings around the fluid port 22, with circumferential gaps between them, which gaps get larger between the dimples on the further outward rings (from the fluid port 22). This is a suitable arrangement for a circular fluid port, although different arrangements are also possible, such as a regular array, or an irregular arrangement, or different numbers or sizes of dimples, or different numbers of rings.

[0146] In these embodiments there are ten dimples in each concentric ring of dimples, and each concentric ring of dimples is rotated out of line of the preceding one such to stagger relative thereto. This can be such that every ring is differently aligned, or as shown such that the inner concentric ring and the third concentric ring are radially aligned whereas the second concentric ring is interposed to lie in a position commonly spaced between two adjacent dimples of the first concentric ring and likewise with respect to two dimples of the second concentric ring.

[0147] In this, and preferred, arrangements, tortuous, rather than linear, fluid passageways are formed from the fluid port 22 to a location outside the concentric rings (or shaped port features 24).

[0148] Having larger gaps between the elements where they lie radially more distant from the fluid port 22 is preferred, with them closer together nearer the fluid port 22. This larger “outer” gap ensures a greater freedom for the fluid to move through the fluid passageways between the dimples, but more importantly it presents a more complete surface near the edge of the gaskets onto which the gaskets 34 can provide a good seal.

[0149] The gaskets 34 may be compressed upon assembly of the stack so as to deflect into the depressions left behind by the pressed out dimples in the sheet of the separator plate 12 (or metal support plate 14). This then further creates the good seal between the fluid port chimney and the volume surrounding the fuel cell units in the stack.

[0150] The outside shape of the fuel cell unit 10 need not match that of the first to fourth embodiments. Indeed, there are many variations available to a skilled person. The present invention is intended to cover any and all of these different shapes. For example, instead of the elongated version shown herein, it may be more rectangular with the fluid ports in the corners, or it may be diamond shaped with the fluid ports at two corners, or it may be oval with the fluid ports at the longer spaced ends thereof.

[0151] FIG. 36 shows a further possible shape for the fuel cell unit 10, wherein the separator plate 12 and the metal support plate 14 are generally rectangular, albeit with cut-out regions in the short ends thereof to define two extending fingers at each end. Fluid ports 22 are provided on each of those two fingers at each end.

[0152] Some embodiments may have more fingers, or more ports.

[0153] In this fifth embodiment, a flanged perimeter feature 18 is again provided, as are shaped port features 24 in the separator plate 12. Furthermore, arrays of projections 30, 32 extend upwardly and downwardly, alternately, throughout a central region of the separator plate for the purposes previously disclosed with respect to the previous four embodiments. There is furthermore an electrochemically active layer 50 incorporated onto the metal support plate 14. By having two fluid ports 22 at each end, fluid flow within the fluid volume within the SOEC or SOFC fuel cell unit 10 can be better directed.

[0154] Referring next to FIG. 37, a detail of a corner of the fuel cell unit 10 of FIG. 37 is shown. As can be seen, a gasket 34 for the fuel stack is also shown. It is sized to overlie over all of the shaped port features 24, which in this embodiment comprise dimples surrounding the fluid ports 22. The dimples can be a number of concentric rings, such as four concentric rings of staggered circular dimples.

[0155] Other arrangements for the shaped port features 24, such as that of the first to fourth embodiments could instead be provided.

[0156] Referring next to FIG. 38, a modified version of the product of FIG. 36 is shown, in which two windows are provided, which windows 54 are arranged end to end for receiving two separate electrochemically active layer components 52.

[0157] Other embodiments might have more than two windows and electrochemically active layer components.

[0158] Referring next to FIG. 39, there is shown a further modification of the fuel cell unit 10 of the present invention in which the pressed flanged perimeter features 18 are located inward of an edge of the fuel cell unit 10 so as to be an upward projection, or ridge, relative to the edges and middle of the separator plate 12, or the metal support plate 14 if instead provided on that, or on both.

[0159] Referring next to FIG. 40, a fuel cell stack is shown comprising multiple fuel cell units 10. As can be seen it has a top compression plate 62 and a bottom compression plate 64 connected together by bolts 66 to allow the cell units 10 to be compressed together, thus ensuring electrical connectivity between the central projections and the porous regions/electrochemically active layers, and thus complete use of each electrochemically active area. Further it shows an entry position 68 and an exit position 70 for the air or fuel fluid to be passed down into a first chimney 72 formed by a first set of gaskets 34 and a column of all the first of the fluid ports and then down out of a second chimney 74 formed by a second set of gaskets 34 and a column of all the second of the fluid ports. It will be understood, however, that the fluid entry and exit may be otherwise arranged relative to the chimneys 72, 74, e.g. both at the top or the bottom, or the fuel cell stack may be mounted on its side (or at an angle).

[0160] FIG. 40 also shows a contact pad 60 at the top and bottom of the stack which illustrate possible positions for connecting the stack to a power demand, — such as the illustrated load L.

[0161] Referring next to FIGS. 43 to 46, a variant corner arrangement is shown. As with the embodiment in FIG. 37, there is a fluid port 22 surrounded by shaped port features 24 and a gasket 34 provided for covering over the recesses formed by the shaped port features 24 during assembly, as can be seen in FIG. 43. The gasket 34 is shown in that figure to have an outside diameter that covers to the outer edges at least of the shaped port features 24, but an inner diameter larger than the fluid port 22. Although optional, this prevents the inner diameter of the gasket 34 occluding the chimney formed by the stack of fluid ports in the final fuel cell stack in the event that the gasket is slightly misaligned relative to the centre of the chimney.

[0162] The shaped port features 24 extend down to contact metal support plate 14, their lowermost surfaces lying in a first plane, the same plane as the flanged perimeter features 18, whereas their uppermost surfaces and the remainder of the separator plate 12 lie in a second plane spaced from the metal support plate 14 so as to define the fluid volume 20.

[0163] In this embodiment, the shaped port features 24 have grooves at the innermost area, which grooves are open to the fluid port 22. There are then two staggered rings of circular recesses, followed by a final ring of alternating grooves and circular recesses, which grooves have a length of approximately twice the diameter of the circular recesses. In this embodiment, the grooves radially align with the circular recesses of the inner of the two staggered rings, and are staggered relative to the grooves at the innermost area. The circular recesses of that final ring instead radially align with the circular recesses of the second of the two staggered rings of circular recesses. This arrangement creates passageways for allowing fluid to flow between the recesses in the inside of the fuel cell unit (from the fluid port into the inside of the fuel cell unit, or in the opposite direction, if venting).

[0164] Although this embodiment is shown in respect of a corner of a fuel cell unit, whereby it could replace the corner arrangements of the fuel cell units shown in FIG. 36, 38 or 39, this arrangement of grooves and recesses could equally be applied to other fuel cell unit designs, including those with single fluid ports at each end, such as that of FIG. 1.

[0165] Referring next to FIGS. 47 to 50, a further variant for the corner of the fuel cell is shown, although again this may be provided on different fuel cell designs, e.g. elsewhere within the shape of a fuel cell unit, be that a fuel cell unit with four fluid ports, with one in each corner (as per FIGS. 36, 38 and 39, or with two fluid ports, one at each end (as in the embodiment of FIG. 1) or any other fuel cell design, including ones with any other number of fluid ports.

[0166] In this variant, in addition to the recesses and/or grooves forming the shaped port features 24, raised members 120 are provided. These raised members 120 are located in a ring external of the outer perimeter of the gasket 34 and provide, in this embodiment, two functions:

[0167] Firstly they provide a guide for the location of the gasket as the gasket can fit internally of the ring of raised members 120, thus seating in the correct position relative to the fluid port 22, i.e. centred relative to the fluid port 22, during assembly of the fuel cell stack.

[0168] Secondly, as shown in FIGS. 49 and 50, the raised members 120 have a height h that is less than, or preferably between 75 and 99% of, or more preferably 75 to 85% (e.g. 78-82%) of, the thickness t of the gasket 34. The ratio of height h to thickness t can be tailored to the compression requirements of the particular gasket used. Although to provide the first function such a large height h is not necessary, and thus it could instead be less tall (e.g. h could be between 5 and 75% of the thickness t of the gasket), it is preferred to be the larger height to provide the second function of providing a hard stop during assembly and stacking of the stack. This hard stop function can be helpful during manufacture of the fuel cell stack as by virtue of the gasket being compressible, to thus enable it to seal over the recesses in the outer surface of the fuel cell unit upon compression, there is a possibility of over compression of the stack during assembly, which over compression could crack or otherwise damage the electrochemically active layers on the metal support plate as the central projections 30 are also brought into contact with those electrochemical layers during that gasket compression. By having a hard stop, a limit can be set for that degree of compression, whereby over compression could be resisted by the hard stops, thus preventing inadvertent cracking of the electrochemically active layers on the metal support plate (and thus better tolerances for the engagement pressures within the fuel cell between the central projections and the electrochemically active layers).

[0169] It is important, however, for these raised members 120 not to be taller than the thickness t of the gaskets 34 as otherwise the gasket cannot be compressed during the stacking process, and similarly the electrical connection between the electrochemically active layer and the central projections could fail to be made, thus preventing the efficient operation of the stack, and introducing potential for hot-spots within it. Nevertheless, the actual height h of the raised members 120, may be varied or set at appropriate for achieving during assembly the required compression of the gasket, and thus the correct connection between the electrochemically active layer and the central projections, to ensure there is proper sealing over of the recesses in the outer surface of the fuel cell unit by the gasket and correct electrical connections across the whole set of central projections 30. An electrically insulating coating or paste layer may be used on one or both of the abutting surfaces (the hard stop surface, formed by raised members 120, and metal substrate of the adjacent fuel cell unit) of adjacent fuel cell units to prevent electrical contact between adjacent fuel cell units via the abutting surfaces.

[0170] In a variant of this, instead of the raised members surrounding the outer perimeter of the gasket 34, the gasket could have forms or holes within it to accommodate the raised members 120, thus again providing a fixed position for the gasket relative to the raised members 120, and potentially a fixed orientation for the gasket relative thereto (or fixed orientations, if the gasket can fit in more than one fixed orientation).

[0171] In a variant of this, the raised members 120 surrounding the outer perimeter of the gasket are formed on the metal support plate 14 extending towards the separator plate 12 of a neighboring fuel cell unit. In a further variant, raised members are formed on the metal support plate 14 and the separator plate 12, these raised members may be spaced from one another. Further, the raised members on the metal support plate 14 and separator plate 12 may be of an intermediate height and arranged such that their raised features abut one another to form interfacing raised members having the same total height as the case where the height of the raised members is provided by raised members on the separator plate 12 or metal support plate 14, or spaced from one another on both the separator plate 12 and metal support plate 14.

[0172] Referring next to FIGS. 51 to 54, a further variant of the corner is shown. In this embodiment, instead of a (preformed) gasket, an annular groove 122 is provided surrounding the fluid port 22 for accommodating an insitu seal material. The groove 122 is shown in FIG. 52 and it is less deep than the recesses 24 of the shaped port features either side of it as it needs not to create a barrier for fluid flow from the fluid port 22 into the internal space of the fuel cell unit.

[0173] Recesses 24 are again provided, arranged in concentric rings. In this case one ring is external of the annular groove, and one ring is internal of the annular groove, the latter being in the form of grooves to the edge of the fluid port. Additional rings of recesses or grooves may also be provided as per the previous embodiments. For clarity, however, just these two rings are shown to allow the annular groove to be seen most clearly.

[0174] Although the annular groove forms a uniform circle in this embodiment, with a constant depth, it would be possible to make the groove less uniform both in radius and depth, but for simplicity a uniform radius and depth is provided.

[0175] Referring then instead to FIG. 51 it can be seen that the annular groove 122 is now covered by an in-situ seal, namely, a ring of sealant material 124. This material 124 may be a liquid or paste applied during assembly of the stack. It can be any conventional sealing contact paste designed when hardened to withstand the operational environment of the fuel cell. It could also be replaced with a (pre-formed) gasket if needed, but the use of an insitu seal has the significant advantage of reducing the parts count, reducing costs and simplifying assembly since the careful positioning of gaskets is no longer required.

[0176] Referring also to FIGS. 53 and 54, with FIG. 54 being a more detailed view, it can be seen that the annular groove 122 accommodates a volume (or bead) of the sealant material 124 and the material 124 also extends in a ring over the top surface of the shaped port features to thus function like the gasket 34 of the previous embodiments. With this arrangement, the thickness of the sealant material 124 can be significantly less than is generally needed for a pre-formed gasket. Again, an electrically insulating seal may be used or alternatively an electrically insulating coating or paste layer may be used on one or both of the abutting surfaces (the hard stop surface, e.g. formed by the raised portion 126 and metal substrate of the adjacent fuel cell unit) of adjacent fuel cell units to prevent electrical contact between adjacent fuel cell units via the abutting surfaces.

[0177] The thickness of the gasket 34 of the previous embodiments helped provide a space between adjacent fuel cell units for air or fuel flow. To retain that space, the shaped port features 24 can be provided in a raised portion 126 of the separator plate 12, as shown in FIGS. 52, 53 and 54. This also ensures that the final height of the top of the gasket seal material still is the correct height to allow the outer surface of the electrochemically active layers to correctly align and contact the tops of the outwardly extending central projections 30 during the compression or clamping of the stack into its final configuration.

[0178] The groove 122 is shown in FIG. 54, the groove has a depth, d, and it is less deep than the recesses 24 either side of it as it needs not to create a barrier for fluid flow from the fluid port 22 into the fluid volume 20 of the fuel cell unit. Preferably, the depth, d, of groove 122 is less than depth, d2, of the raised portion 126. Preferably still, the depth, d, of the groove is between 5 and 75% of the depth, d2, of the raised portion 126. Typically, this may correspond to the groove 122 extending into the space between the metal support plate and the separator plate by between 5 to 80%, or more preferably between 10 and 50%, and preferably either way less than 50%, of the depth of the extension of the recesses 24. The depth may be measured externally, as indicated by d and d2 in FIG. 54, or can be measured internally across the internal height of the internal space of the fuel cell unit.

[0179] The raised portion 126 within which the annular groove 122 is disposed may act as a hard stop feature, similar to the hard stop feature of FIGS. 47 to 50. It would of course be possible to include, in addition to the annular groove, projections to provide a similar hard stop feature to that of FIGS. 47 to 50 so as to help avoid over compression of the seal material/stack. Likewise, it could even be possible to use the liquid applied seal material, rather than a pre-formed gasket, without an annular groove by surface fitting it, e.g. on a flat annular surface. However, not having the groove could result in a greater likelihood of seal failure because the groove provides a volume into which a portion of the seal material may be pushed during compression (anchored), and without the groove the seal material might be pushed away from regions of the sealing surface, for example due to small misalignments of the stack. Seal failure would allow mixing of fuel and air within the stack, which is undesirable. The annular groove is thus more preferred as a solution for offering greater service life for the stack during use.

[0180] Finally, referring to FIG. 41, an illustration of a stack of fuel cell units according to the first embodiment is illustrated. This is before any housing or compression bolts, or top and bottom plates 62, 64 are added. It is to illustrate the chimneys (internal manifold here formed by multiple aligned ports and aligned gaskets) 72, 74, through the top of which the internal edges of the metal support plate 14, the separator plate 12 and the gasket 34 can be seen. Fluid in the chimney can enter the fluid volume 20 within each fuel cell unit 10 between the metal support plate 14 and the separator plate 12 of each fuel cell unit, but not between adjacent fuel cell units 10 because of the gasket 34, whereas fluid external of the fuel cell units can pass to the space between the adjacent cells, other than at the gasket and the chimney, e.g. at arrows 76, as the sides/edges between them are open.

[0181] In summary, there is provided a metal-supported fuel cell unit 10 comprising a separator plate 12 and metal support plate 14 such as a stainless steel foil bearing chemistry layers 50, which overlie one another to form a repeat unit, at least one plate having flanged perimeter features 18 formed by pressing the plate, the plates being directly adjoined at the flanged perimeter features to form a fluid volume 20 between them and each having at least one fluid port 22, wherein the ports are aligned and communicate with the fluid volume, and at least one of the plates has pressed shaped port features 24 formed around its port extending towards the other plate and including elements spaced from one another to define fluid pathways to enable passage of fluid from the port to the fluid volume. A stack may therefore be formed from minimal number of different, multi-functional components. Raised members 120 also formed by pressing may receive a gasket 34, act as a hard stop or act as a seal bearing surface.

[0182] Alternative arrangements and shapes will also be within the scope of the present invention, for example in which instead of rounded fingers, squared off fingers are provided. Likewise, the shape of the shaped port features, as a group of elements, do not need to match the shape of the area of the cell unit to which they are provided, as the fluid exiting the fluid pathways can circulate around any gap between the group of elements and the flanged perimeter features.

[0183] These and other features of the present invention have been described above purely by way of example. Modifications in detail may be made to the invention within the scope of the claims and particularly in respect of the shape of the fuel cell unit, the electrochemically active layers and the arrangement of the elements of the shaped port features and central projections for enabling fluid flow between fluid ports through the fluid volume within the fuel cell unit.

REFERENCE SIGNS

[0184] Prior Art [0185] 90—fuel cell unit [0186] 110—metal support plate [0187] 150—separator plate [0188] 150A—up & down corrugations [0189] 152—spacer [0190] 160—large space/aperture [0191] 180—fluid port [0192] 200—fluid port [0193] Invention [0194] 10—fuel cell unit [0195] 12—separator plate [0196] 14—metal support plate [0197] 18—flanged perimeter features [0198] 20—fluid volume [0199] 22—fluid port [0200] 24—shaped port features [0201] 26—elements of the shaped port features [0202] 28—fluid passageways [0203] 30, 32—central projections [0204] 34—gaskets [0205] 48—small holes [0206] 50—electrochemically active layer [0207] 52—separate component [0208] 54—window [0209] 58—ridge [0210] 60—contact pad [0211] 62—top compression plate [0212] 64—bottom compression plate [0213] 66—bolts [0214] 68—entry position [0215] 70—exit position [0216] 72—first chimney [0217] 74—second chimney [0218] 120—raised members [0219] 122—annular groove [0220] 124—in-situ seal [0221] 126—raised portion [0222] h—height of raised members [0223] t—thickness of gasket [0224] d—depth of groove [0225] d2—depth of raised portion