Solid oxide fuel cell unit

Abstract

The present invention relates to an improved metal supported solid oxide fuel cell unit, fuel cell stacks, fuel cell stack assemblies, and methods of manufacture.

Claims

1. A metal supported solid oxide fuel cell unit comprising: a) a metal substrate defining first and second opposed surfaces, wherein at least one solid oxide fuel cell is disposed on said second surface of said metal substrate; b) a metal spacer, which defines first and second opposed surfaces, said metal spacer comprising: (i) an external perimeter, (ii) at least one fuel inlet internal perimeter defining a fuel inlet port, (iii) at least one cut-out internal perimeter defining a cut-out, and (iv) at least one fuel outlet internal perimeter defining a fuel outlet port, wherein said first surface of said metal substrate is attached to said second surface of said metal spacer; and c) a metal interconnect plate which defines first and second opposed surfaces, said second surface of said metal interconnect plate sealingly attached to said first surface of said metal spacer, wherein: a fuel inlet port volume is defined between said first surface of said metal substrate, each fuel inlet internal perimeter of said metal spacer, and said second surface of said metal interconnect plate, a cut-out volume is defined between said first surface of said metal substrate, said at least one cut-out internal perimeter of said metal spacer, and said second surface of said metal interconnect plate, and a fuel outlet port volume is defined between said first surface of said metal substrate, each fuel outlet internal perimeter of said metal spacer, and said second surface of said metal interconnect plate, wherein said metal interconnect plate comprises a plurality of bridge portions defining a fluid flow path from said at least one fuel inlet port volume to said at least one cut-out volume to said at least one fuel outlet port volume.

2. A metal supported solid oxide fuel cell unit according to claim 1, wherein a fluid flow path is defined from the at least one fuel inlet port to the at least one cut-out internal perimeter to the at least one fuel outlet port via the bridge portions.

3. A metal supported solid oxide fuel cell unit according to claim 1, wherein there are a plurality of bridge portions between adjacent volumes.

4. A metal supported solid oxide fuel cell unit according to claim 1, wherein each metal spacer fuel inlet port and each metal spacer fuel outlet port comprises a fuel duct region, a plurality of fuel throat regions, and a corresponding plurality of fuel distributor channel regions.

5. A metal supported solid oxide fuel cell unit according to claim 1, wherein said bridge portions extend outwardly from said first surface of said metal interconnect plate, away from said second surface of said metal interconnect plate.

6. A metal supported solid oxide fuel cell unit according to claim 1, wherein said bridge portions comprise an elongate dimple.

7. A metal supported solid oxide fuel cell unit according to claim 1, wherein said bridge portions define a volume between said first surface of said metal spacer and said second surface of said metal interconnect plate.

8. A metal supported solid oxide fuel cell unit according to claim 1, wherein said metal spacer comprises at least two fuel inlet internal perimeters defining at least two fuel inlet ports.

9. A metal supported solid oxide fuel cell unit according to claim 1, wherein said metal spacer comprises at least two cut-out internal perimeters defining at least two cut-outs.

10. A metal supported solid oxide fuel cell unit according to claim 1, wherein said metal spacer comprises at least two fuel outlet internal perimeters defining at least two fuel outlet ports.

11. A metal supported solid oxide fuel cell unit according to claim 1, wherein said metal supported solid oxide fuel cell unit is a metal supported solid oxide fuel cell stack layer.

12. A solid oxide fuel cell stack comprising a plurality of metal supported solid oxide fuel cell units according to claim 1.

13. A solid oxide fuel cell stack assembly comprising: a base plate, an end plate, a solid oxide fuel cell stack according to claim 12, and a skirt attached to said base plate and said end plate and defining a volume between said skirt, said base plate and said end plate within which is contained said fuel cell stack.

14. A method of assembly of a metal supported solid oxide fuel cell unit, the metal supported solid oxide fuel cell unit comprising: a) a metal substrate defining first and second opposed surfaces, wherein at least one solid oxide fuel cell is disposed on said second surface of said metal substrate; b) a metal spacer, which defines first and second opposed surfaces, said metal spacer comprising: (i) an external perimeter, (ii) at least one fuel inlet internal perimeter defining a fuel inlet port, (iii) at least one cut-out internal perimeter defining a cut-out, and (iv) at least one fuel outlet internal perimeter defining a fuel outlet port; and c) a metal interconnect plate which defines first and second opposed surfaces, said method of assembly comprising the steps of: (i) attaching said first surface of said metal substrate to said second surface of said metal spacer; and (ii) sealingly attaching said second surface of said metal interconnect plate to said first surface of said metal spacer, wherein: a fuel inlet port volume is defined between said first surface of said metal substrate, each fuel inlet internal perimeter of said metal spacer, and said second surface of said metal interconnect plate, a cut-out volume is defined between said first surface of said metal substrate, said at least one cut-out internal perimeter of said metal spacer, and said second surface of said metal interconnect plate, and a fuel outlet port volume is defined between said first surface of said metal substrate, each fuel outlet internal perimeter of said metal spacer, and said second surface of said metal interconnect plate, wherein said metal interconnect plate comprises a plurality of bridge portions defining a fluid flow path from said at least one fuel inlet port volume to said at least one cut-out volume to said at least one fuel outlet port volume.

Description

(1) Of the Figures:

(2) FIG. 1 shows an exploded perspective view of the fuel cell unit components of Embodiment 1

(3) FIG. 2 shows a top view of metal substrate components located on an assembly baseplate

(4) FIG. 3 shows a top view of a metal spacer positioned on top of metal substrate components of FIG. 2

(5) FIG. 4 shows a top view of a first clamping plate positioned on top of the metal spacer of FIG. 3 for welding purposes

(6) FIG. 5 shows a top view of the metal spacer of FIG. 3 after welding and removal of the first clamping means

(7) FIG. 6 shows a top view of a metal interconnect plate positioned on top of the metal spacer of FIG. 5

(8) FIG. 7 shows a top view of a second clamping plate positioned on top of the metal interconnect plate of FIG. 6 for welding purposes

(9) FIG. 8 shows a top view of the metal interconnect plate of FIG. 6 after welding and removal of the second clamping means and removal from the assembly base plate

(10) FIG. 9 shows a cross-section through a metal substrate plate

(11) FIG. 10 shows an exploded perspective view of the fuel cell unit of Embodiment 2

(12) FIG. 11 shows an exploded perspective view of the fuel cell unit of Embodiment 4

(13) FIG. 12 shows a top view of the component parts of the fuel cell unit of the fuel cell unit of Embodiment 5

(14) FIG. 13 shows a top view of a part of a metal spacer

(15) FIG. 14 shows a top view of a part of a metal interconnect plate

(16) FIG. 15 shows an exploded perspective view of a fuel cell unit of Embodiment 1 with an illustration of fuel flow

(17) FIG. 16A is a CFD image showing fuel velocity in a prior art device

(18) FIG. 16B is a CFD image showing fuel velocity in a prior art device (shading indicates fuel mid plane velocities in m.Math.s{circumflex over ( )}-1)

(19) FIG. 16C is a CFD image showing fuel velocity in a device according to the present invention (shading indicates fuel mid plane velocities in m.Math.s{circumflex over ( )}-1)

(20) FIG. 17A is a CFD image showing normalised fuel residence time (age of fuel) in a prior art device

(21) FIG. 17B is a CFD image showing normalised fuel residence time (age of fuel) in a device according to the present invention

(22) A list of the reference signs used herein is given at the end of the specific embodiments. Repeat use of reference symbols in the present specification and drawings is intended to represent the same or analogous features or elements.

(23) It will be apparent to those of ordinary skill in the art that various modifications and variations can be made in the present invention without departing from the scope of the appended claims. For instance, features described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.

(24) Other objects, features, and aspects of the present invention are disclosed in the remainder of the specification. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary constructions.

EMBODIMENT 1

(25) Fabrication of a metal supported solid oxide fuel cell unit 1 is illustrated in the Figures. Metal supported solid oxide fuel cell unit 1 is for use as a solid oxide fuel cell stack layer.

(26) In this embodiment, metal supported solid oxide fuel cell unit 1 is fabricated comprising a metal substrate 65 (also referred to as a “substrate layer” or a “metal substrate layer”), a metal spacer 30, and a metal interconnect plate 20.

(27) Metal substrate plates 70a and 70b each comprise a porous region 78 defined by laser-drilled perforations 78a extending between first surface 71 and second surface 72. Fuel cell 79 is deposited over porous region 78 on second surface 72 of metal substrate plates 70a and 70b, and comprises an anode layer deposited over (bonded to) porous region 78 of metal substrate plate 70a, 70b, an electrolyte layer deposited over (bonded to) the anode layer, and a cathode layer deposited over the electrolyte layer. Porous region 78 is surrounded by non-porous region 78b.

(28) As shown in FIG. 2, assembly baseplate 80 comprises fixed dowels 83a, 83b, 83c, 83d, 83e, 83f, 83g, and spring loaded dowels 84a, 84b, 84c, 84d, 84e, 84f, 84g. Assembly baseplate 80 also defines (comprises) a datum edge 81.

(29) Metal substrate plates 70a and 70b, and blanking plates 50a and 50b are aligned on assembly baseplate 80, and alignment is achieved by fixed dowels 83a, 83b, 83c, 83d, 83e, 83f, 83g, spring loaded dowels 84a, 84b, 84c, 84d, 84e, 84f, 84g, and datum edge 81.

(30) Second surface 52 of blanking plate 50a is disposed on (i.e. contacts/abuts) assembly baseplate 80. Second edge 58 of blanking plate 50a is aligned on datum edge 81 by fixed dowel 83g, and first edge 57 of blanking plate 50a is aligned to fixed dowel 83a and spring loaded dowel 84a. Curved edge 55 of blanking plate 50a is aligned by spring loaded dowel 84g.

(31) Second surface 52 of blanking plate 50b is disposed on (i.e. contacts/abuts) assembly baseplate 80. Second edge 58 of blanking plate 50b is aligned on the datum edge 81 by fixed dowel 83c, and first edge 57 of blanking plate 50b is aligned to fixed dowel 83b and spring loaded dowel 84d. Curved edge 55 of blanking plate 50b is aligned with spring loaded dowel 84e.

(32) Second surface 72 of metal substrate plate 70a is disposed on (i.e. contacts/abuts) assembly baseplate 80.

(33) Metal substrate plates 70a and 70b are positioned on assembly baseplate 80 between blanking plates 50a and 50b. Second short side 75 of metal substrate plate 70a is aligned on datum edge 81 by fixed dowels 83f and 83e. First short side 74 of metal substrate plate 70a is aligned by spring loaded dowel 84b.

(34) Second short side 75 of metal substrate plate 70b is aligned on datum edge 81 by fixed dowel 83d and spring loaded dowel 84f. First short side 74 of metal substrate plate 70b is aligned by spring loaded dowel 84c.

(35) Outer long side 76 of metal substrate plate 70a is aligned parallel to inner edge 59 of the blanking plate 50a, defining a tolerance gap 82a between metal substrate plate 70a and blanking plate 50a.

(36) Outer long side 76 of metal substrate plate 70b is aligned parallel to inner edge 59 of blanking plate 50b, defining a tolerance gap 82b between metal substrate plate 70b and blanking plate 50b.

(37) Tolerance gap 82c is defined between inner long side 77 of metal substrate plate 70a and inner long side 77 of metal substrate plate 70b.

(38) As shown in FIG. 3, metal spacer 30 is then placed on top of blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b.

(39) Second surface 32 of metal spacer 30 is disposed on (i.e. contacts/abuts) first surface 51 of blanking plate 50a, first surface 71 of metal substrate plate 70a, first surface 71 of metal substrate plate 70b, and first surface 51 of blanking plate 50b.

(40) Metal spacer 30 is aligned with blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b by fixed dowel 83e, spring loaded dowels 84a, 84d, 84e, 84f and 84g, and datum edge 81.

(41) Second elongate edge 38 of metal spacer 30 is aligned with datum edge 81 and second edge 58 of blanking plates 50a and 50b and second short sides 75 of metal substrate plates 70a and 70b using fixed dowel 83e and spring loaded dowel 84f. First elongate edge 37 of metal spacer 30 is aligned with first edges 57 of blanking plates 50a and 50b and first short sides 74 of metal substrate plates 70a and 70b using spring loaded dowels 84a and 84d.

(42) The external perimeters of blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b do not extend beyond external perimeter 33 of metal spacer 30.

(43) Metal spacer 30 comprises cut-out internal perimeters 39a and 39b, with each internal perimeter defining a respective cut-out 40a and 40b, and a cross member 41 between them. Metal substrate plates 70a and 70b wholly overlap cut-out internal perimeters 39a and 39b of metal spacer 30, i.e. metal substrate plates 70a and 70b wholly cover cut-outs 40a and 40b.

(44) Metal spacer 30 also comprises a plurality of fuel inlet internal perimeters 33a, 33b, and fuel outlet internal perimeters 33c, 33d defining fuel ports 34a, 34b, 34c and 34d. Each fuel port comprises a number of regions—fuel duct region 44a, fuel throat region 44b, and fuel distributor channel region 44c.

(45) As shown in FIG. 4, first clamping plate 90 is then placed on top of metal spacer 30, i.e. contacts/abuts first surface 31 of metal spacer 30.

(46) First clamping plate 90 defines orifices 92a and 92b. Spring loaded dowel 84h projects through orifice 92a, and fixed dowel 83e projects through orifice 92b, allowing first clamping plate 90 to be aligned with metal spacer 30 (and therefore also with blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b).

(47) Clamping means (not shown) clamps first clamping plate 90 and assembly baseplate 80, i.e. clamps metal spacer 30, blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b.

(48) First clamping plate also defines welding slots 91a, 91b and 91c.

(49) Welding means (not shown) is used to create line weld seam 100a between metal spacer 30 and blanking plate 50a, line weld seams 100b and 100c between metal spacer 30 and metal substrate plate 70a, line weld seams 100d and 100e between metal spacer 30 and metal substrate plate 70b, and line weld seam 100f between metal spacer 30 and blanking plate 50b.

(50) Non-porous region 78b of metal substrate plates 70a, 70b is attached to metal spacer 30.

(51) Blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b, and blanking plate 50b attached to metal spacer 30 form/define a metal substrate 65, i.e. a metal substrate 65 attached to metal spacer 30.

(52) First clamping plate 90 is then removed, as shown in FIG. 5 (fixed dowel 83e and spring loaded dowels 84a, 84d and 84f are not shown).

(53) As shown in FIG. 6, metal interconnect plate 20 is then placed on top of metal spacer 30.

(54) Second surface 22 of metal interconnect plate 20 is disposed on (i.e. contacts/abuts) first surface 31 of metal spacer 30.

(55) Metal interconnect plate 20 is aligned with metal spacer 30 (and therefore also blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b) by fixed dowel 83e, spring loaded dowels 84a, 84d, and 84f, and datum edge 81. Spring loaded dowels 84a and 84d abut first edge 27 of metal interconnect plate 20. Second edge 28 of metal interconnect plate 20 abuts datum edge 81, fixed dowel 83e, and spring loaded dowel 84f.

(56) Metal interconnect plate 20 comprises a plurality of dimples 110 and elongate bridge dimples 120, 121 which extend outwardly from first surface 21, i.e. away from second surface 22 and away from metal spacer 30 and the metal substrate 65 attached to metal spacer 30.

(57) Dimples 110 are formed in a number of regions including regions corresponding to the location of fuel cells 79 of metal substrate plates 70a, 70b, such that in a fuel cell stack arrangement comprising a plurality of fuel cell units 1 in a stack, the dimples 110 of a first fuel cell unit 1 contact the fuel cells 79 of an adjacent fuel cell unit 1 with which it is stacked. Thus, the dimples 110 form an electrical connection with the outer (cathode) surface of the fuel cells 79, with electrical current flowing from the first surface 21 of metal interconnect plate 20 to the cathode layer of the adjacent fuel cell/fuel cells 79 of the adjacent fuel cell unit 1.

(58) As described in more detail later, elongate bridge dimples 120, 121 act as fluid flow bridges between separate zones/areas/volumes of the final fuel cell unit 1.

(59) As shown in FIG. 7, second clamping plate 95 is then placed on top of metal interconnect plate 20, i.e. contacts/abuts first surface 21 of metal interconnect plate 20.

(60) Second clamping plate 95 defines orifices 98a and 98b. Spring loaded dowel 84h projects through orifice 98a, and fixed dowel 83e projects through orifice 98b, allowing second clamping plate 95 to be aligned with metal interconnect plate 20 (and therefore also with metal spacer 30, blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b).

(61) Second clamping plate 95 comprises inner perimeter 96 which defines opening 96a.

(62) Clamping means (not shown) clamps second clamping plate 95 and assembly baseplate 80, i.e. clamps metal interconnect plate 20, metal spacer 30, blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b.

(63) Welding means (not shown) is used to create a continuous perimeter weld seam 101 between metal interconnect plate 20, metal spacer 30, and blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b, and blanking plate 50b.

(64) Second clamping plate 95 is then removed, and the completed metal supported solid oxide fuel cell unit 1 is removed from assembly base plate 80.

(65) In the completed metal supported solid oxide fuel cell unit 1, fuel ducts 130 are defined by fuel ports 24, fuel duct regions 44a of fuel ports 34a-d, all of which are aligned with one another. Fuel ducts 130 extend between first surface 21 of metal interconnect plate 20 and second surface 52 of blanking plates 50a, 50b.

(66) At first end 2 of fuel cell unit 1 (see e.g. FIG. 3), first volumes (fuel inlet port volumes 35a) are defined between first surface 51 of blanking plate 50a, fuel inlet internal perimeters 33a, 33b of metal spacer 30, and second surface 22 of metal interconnect plate 20.

(67) A second volume (a cut-out volume 35b) is defined between first surface 71 of metal substrate plate 70a, cut-out internal perimeter 39a of metal spacer 30, and second surface 22 of metal interconnect plate 20.

(68) A third volume (a cut-out volume 35b) is defined between first surface 71 of metal substrate plate 70b, cut-out internal perimeter 39b of metal spacer 30, and second surface 22 of metal interconnect plate 20.

(69) At second end 3 of fuel cell unit 1, fourth volumes (fuel outlet port volumes 35c) are defined between first surface 51 of blanking plate 50b, fuel outlet internal perimeters 33c and 33d of metal spacer 30, and second surface 22 of metal interconnect plate 20.

(70) At first end 2 of fuel cell unit 1, elongate dimples 120 act to define a fluid flow passage between the first and second volumes, i.e. act as fluid flow bridges between the first and second volumes. The fluid flow bridges are the volumes between the elongate dimples 120 and the metal spacer 30.

(71) Elongate dimples 121 act to define a fluid flow passage between the second and third volumes (i.e. between the adjacent cut-out volumes 35b). The fluid flow bridges are the volumes between the elongate dimples 121 and the metal spacer 30.

(72) At second end 3 of fuel cell unit 1, elongate dimples 120 act to define a fluid flow passage between the third and fourth volumes, i.e. act as fluid flow bridges between the first and second volumes. The fluid flow bridges are the volumes between the elongate dimples 120 and the metal spacer 30.

(73) Thus, a fluid flow path is defined (using the fuel inlet port volumes 35a, cut-out volumes 35b, fuel outlet port volumes 35c, and fluid flow bridges) from: (1) fuel duct regions 44a of fuel ports 34a, 34b, to (2) fuel throat regions 44b of fuel ports 34a, 34b, to (3) fuel distributor channel regions 44c of fuel ports 34a, 34b, to (4) elongate dimples 120 at first end 2 of fuel cell unit 1, to (5) the second volume defined between first surface 71 of metal substrate plate 70a, cut-out internal perimeter 39a of metal spacer 30, and second surface 22 of metal interconnect plate 20, to (6) elongate dimples 121, to (7) the third volume defined between first surface 71 of metal substrate plate 70b, cut-out internal perimeter 39b of metal spacer 30, and second surface 22 of metal interconnect plate 20, to (8) fuel distributor channel regions 44c of fuel ports 34c, 34d, to (9) fuel throat regions 44b of fuel ports 34c, 34d, to (10) fuel duct regions 44a of fuel ports 34c, 34d.

(74) Thus, a fluid flow path 140 (i.e. a fuel flow path) is defined within fuel cell unit 1 from fuel ducts 130 at first end 2 to fuel ducts 130 at second end 3.

(75) The fluid flow path 140 is illustrated in FIG. 15.

(76) As can be seen from FIGS. 13 and 14, metal interconnect plate 20 comprises one elongate bridge dimple 120a which transfer the fuel from one fuel distributor channel 44c1 to the cut out 40a. Likewise, metal interconnect plate 20 comprises two elongate bridge dimples 120b which transfer the fuel from one fuel distributor channel 44c2 to the cut out 40a. Furthermore, metal interconnect plate 20 comprises three elongate bridge dimples 120c which transfer the fuel from one fuel distributor channel 44c3 to the cut out 40a.

(77) The width of the elongate bridge dimples ra, rb and rb1 remain constant. However, the width rc, rc1 and rc2 of the elongate bridge dimple (the length of the shortest side of the rectangular cross section shape of elongate bridge dimples 120c) increases as the elongate bridge dimples 120c get close to the centre of the fuel cell unit. That is to say, rc2>rc1>rc, so that the flow area enclosed inside the elongate bridge dimples 120c closer to the middle of the fuel cell is gradually greater, being the fuel promoted uniformly to the centre of the fuel cell avoiding fuel starvation in said centre of the fuel cell.

(78) FIG. 14 also illustrates the alternating dimples 110 and 122, with dimples alternating between extending away from the first surface and from the second surface of the metal interconnect plate. For the avoidance of doubt, elongate dimples 120, 120a, 120b, 120c and 121 do not alternate and instead all extend from first surface 21 of metal interconnect plate 20, away from second surface 22.

(79) FIG. 13 illustrates the arrangement of the fuel ports 34a, 34b, 34c and 34d of the metal spacer 30. The fuel throat region 44b comprises a constant width “W” between the fuel port 34a to the corresponding fuel distributor channel region 44c (fuel distributor channel regions 44c1, 44c2, 44c3) wherein the fuel is transferred at high speed from such fuel ports 34a to the corresponding fuel distributor channel region, reducing the risk of fuel starvation.

(80) In addition, fuel distributor channel region 44c (44c1, 44c2, 44c3) comprises a curved shape being the width of said fuel distributor channel region 44c gradually increasing, starting from the width “W” of fuel throat region 44b and finishing at a width equal to a distance (da, db, dc), wherein (da<db<dc).

(81) The distance d (da, db, dc) at the edge of the fuel distributor channel region 44c is longer in the areas close to the centre of the fuel cell unit 1 to promote the fuel uniformly along the middle region of the fuel cell unit 1, improving the fuel distribution.

(82) In a fuel cell stack assembly, the length “L” of the fuel throat region 44b is related to the size of the compression gaskets located in between the metal interconnect plate 20 of one solid oxide fuel cell unit 1 and the substrate layer 65 of the following solid oxide fuel cell unit 1, the gasket comprising a toroid shape surrounding one port of interconnect. The length “L” of the fuel throat region 44b is coincident with the external radius minus the internal radius of the compression gasket to minimize pressure drop.

(83) Additional dimples 122 are located in between dimples 110 and elongate bridge dimples 120, alongside such side elongate bridge dimples 120. In addition, additional dimples 122 are located in between dimples 110 and elongate bridge dimples 121. Dimples 122 maintain clearance between the interconnect 20 and the metal substrate 65 avoiding fuel blockage in such areas where the additional dimples 122 are located.

(84) Elongate bridge dimples 120c comprise a wedge shape along its shortest side of its rectangular cross-sectional shape, such wedge shape located on the side connecting the fuel distribution channel region 44c3 to the elongate bridge dimples 120c. In a fuel cell stack assembly, the wedge shape maintains clearance between the metal interconnect plate 20 and the next fuel cell unit 1, reducing the risk of short circuits between two adjacent solid oxide fuel cell units 1.

(85) FIGS. 16A, 16B and 16C show the significant improvement in fuel velocity achieved with the present invention (FIG. 16C) as compared to prior art devices. In particular, there is a significant increase in fuel velocity around port areas. The fuel velocity remains more constant with the present invention (FIG. 16C), with less fuel deficiency regions at the corner of the fuel cell unit 1, and the fuel promoted uniformly across the fuel cell unit 1, which improve the chemical reaction occurring within the fuel cell.

(86) FIGS. 17A and 17B and Table 1 show that in the present invention the normalised fuel residence time has decreased as compared to the prior art, which means less concentration of Hydrogen is required for the chemical reaction. That is to say, less fuel is needed for the chemical reaction to occur, so the efficiency of the present invention is improved as compared to the prior art.

(87) TABLE-US-00001 TABLE 1 Average at Active Average in Maximum region exit active region Prior art 1.1 0.88 0.72 Embodiment 1 0.78 0.62 0.29

(88) Table 2 illustrates flow uniformity at the fuel cell unit 1 active area—a higher coefficient shows a better flow distribution across the active region, so the fuel is better distributed across the cell in the present application.

(89) TABLE-US-00002 TABLE 2 Entry Exit Prior art 0.56 0.51 Present invention 0.81 0.81

(90) Table 3 illustrates pressure drop at operating point. Due to a better distribution of the fuel, the pressure drop between inlet and outlet ports has decreased in the present invention as compared to the prior art. Minimizing the pressure drop across the cell is beneficial to maintain the compression along the stack.

(91) TABLE-US-00003 TABLE 3 Pressure drop Prior art 58.17 mbar Present invention 49.8 mbar

(92) Suitable material for various components include (Table 4):

(93) TABLE-US-00004 TABLE 4 metal interconnect plate 20 ferritic stainless steel, grade 441 metal spacer 30 ferritic stainless steel, grade 441 blanking plates 50a, 50b Crofer 22 APU (VDM Metals GmbH) metal substrate plates 70a, 70b Crofer 22 APU (VDM Metals GmbH)

EMBODIMENT 2

(94) As shown in FIG. 10, Embodiment 2 is as per Embodiment 1, except that in metal supported solid oxide fuel cell unit 1: (i) blanking plate 50a and metal substrate plate 70a are formed as a combined metal substrate plate 170a, and (ii) blanking plate 50b and metal substrate plate 70b are formed as a combined metal substrate plate 170b.

(95) Fabrication and operation is otherwise identical to that of Embodiment 1.

EMBODIMENT 3

(96) As per WO2015/136295, a fuel cell stack assembly is formed using a plurality of fuel cell units 1. In more detail, a stack of fuel cell units 1 is assembled on top of a metal base plate (ferritic stainless steel 3CR12), with a Thermiculite 866 gasket electrically insulating the base plate from the adjacent fuel cell unit 1, and a power take off located between the Thermiculite 866 gasket and the adjacent fuel cell unit 1. Thermiculite 866 gaskets are located between the first ends 2 of adjacent fuel cell units 1, and between the second end 3 of adjacent fuel cell units. A power take-off is then positioned upon the top (i.e. the exposed) fuel cell unit 1, a Thermiculite 866 gasket is then placed on top of the power take-off and a metal end plate (ferritic stainless steel 3CR12) placed upon the Thermiculite gasket. Compressive force is then exerted by compression means between the base plate and the end plate, and a skirt attached to the base plate and the end plate to define a volume between them within which is contained the fuel cell stack and its fuel cell units.

EMBODIMENT 4

(97) As shown in FIG. 11, Embodiment 4 is as per Embodiment 1, except that in solid oxide fuel cell unit 1: (i) blanking plate 50a, metal substrate plate 70a, metal substrate plate 70b and blanking plate 50b are formed as a single combined metal substrate plate 180 (a metal substrate) (ii) metal spacer 30 has a single cut-out internal perimeter 39a defining a single cut-out.

(98) Fabrication and operation is otherwise identical to that of Embodiment 1.

EMBODIMENT 5

(99) As shown in FIG. 12, a fuel cell unit 1 is fabricated as per Embodiment 1. In this embodiment, there are a total of six metal substrate plates 70, and six corresponding cut-outs 40.

EMBODIMENT 6

(100) This embodiment is as per Embodiment 4, except that metal substrate plate 180 comprises a single porous region 78, and a single fuel cell 79 is provided on the second surface 72 of metal substrate plate 180, the porous region and the fuel cell extending to the perimeter of the single cut-out internal perimeter 39a.

(101) When manufacturing the fuel cell unit 1, the first welding step (in which the metal substrate 65/70 components are welded to the metal spacer 30) is not necessary. Instead, a single welding around the perimeter through the three layers is performed.

(102) Various modifications, adaptations and alternative embodiments will be readily apparent to the person of ordinary skill in the art without departing from the scope of the appended claims. Reference signs are incorporated in the claims solely to ease their understanding, and do not limit the scope of the claims.

REFERENCE SIGNS

(103) 1 Solid oxide fuel cell unit 2 First end 3 Second end 20 Metal interconnect plate 21 First surface (of metal interconnect plate 20) 22 Second surface (of metal interconnect plate 20) 23 External perimeter (of metal interconnect plate 20) 24 Fuel port (of metal interconnect plate 20) 27 First edge (of metal interconnect plate 20) 28 Second edge (of metal interconnect plate 20) 30 Metal spacer 31 First surface (of metal spacer 30) 32 Second surface (of metal spacer 30) 33 External perimeter (of metal spacer 30) 33a Fuel inlet internal perimeter 33b Fuel inlet internal perimeter 33c Fuel outlet internal perimeter 33d Fuel outlet internal perimeter 34a Fuel port 34b Fuel port 34c Fuel port 34d Fuel port 35a Fuel inlet port volume 35b Cut-out volume 35c Fuel outlet port volume 37 First elongate edge (of metal spacer 30) 38 Second elongate edge (of metal spacer 30) 39a Cut-out internal perimeter 39b Cut-out internal perimeter 40 Cut-out 40a Cut-out 40b Cut-out 41 Cross member 44a Fuel duct region 44a1 Fuel duct region 44a2 Fuel duct region 44a3 Fuel duct region 44b Fuel throat region 44c Fuel distributor channel region 44c1 Fuel distributor channel region 44c2 Fuel distributor channel region 44c3 Fuel distributor channel region 50a Blanking plate 50b Blanking plate 51 First surface (of blanking plate) 52 Second surface (of blanking plate) 54 Fuel port (of blanking plate) 55 Curved edge (of blanking plate) 57 First edge (of blanking plate) 58 Second edge (of blanking plate) 59 Inner edge (of blanking plate) 65 Metal substrate 65a Metal substrate first surface 65b Metal substrate second surface 70 Metal substrate 70a Metal substrate plate 70b Metal substrate plate 71 First surface (of metal substrate plate) 72 Second surface (of metal substrate plate) 74 First short side (of metal substrate plate) 75 Second short side (of metal substrate plate) 76 Outer long side (of metal substrate plate) 77 Inner long side (of metal substrate plate) 78 Porous region (of metal substrate plate) 78a Perforation 78b Non-porous region (of metal substrate plate) 79 Solid oxide fuel cell 80 Assembly baseplate 81 Datum edge 82a Tolerance gap 82b Tolerance gap 82c Tolerance gap 83a Fixed dowel 83b Fixed dowel 83c Fixed dowel 83d Fixed dowel 83e Fixed dowel 83f Fixed dowel 83g fixed dowel 84a Spring loaded dowel 84b Spring loaded dowel 84c Spring loaded dowel 84d Spring loaded dowel 84e Spring loaded dowel 84f Spring loaded dowel 84g Spring loaded dowel 84h Spring loaded dowel 90 First clamping plate 91a Welding slot 91b Welding slot 91c Welding slot 92a Orifice 92b Orifice 95 Second clamping plate 96 Inner perimeter 96a Opening 98a Orifice 98b Orifice 100a Line weld seam 100b Line weld seam 100c Line weld seam 100d Line weld seam 100e Line weld seam 100f Line weld seam 101 Perimeter weld seam 110 Dimple 120 Elongate bridge dimple 120a Elongate bridge dimple 120b Elongate bridge dimple 120c Elongate bridge dimple 121 Elongate bridge dimple 122 Dimple 130 Fuel duct 140 Fluid flow path 170a Combined metal substrate plate 170b Combined metal substrate plate 180 Combined metal substrate plate da Distance db Distance dc Distance rc1 Width rc2 Width rc3 Width L Length (of fuel throat region 44b) W Width (of fuel throat region 44b)