Plate stack

Abstract

The present invention relates to a stack of substantially flat plates stacked one on top of the other along a stacking (Z) direction, wherein each plate is extending in a horizontal direction being perpendicular to the stacking direction and being defined by a longitudinal (X) and a transversal (Y) direction, the substantially flat plates defining at least a first plate interspace (21) between a first plate (11) and an opposing second plate (12) and at least a second plate interspace (22) between the second plate (12) and an opposing third plate (13), wherein the first and the second interspaces (21, 22) are arranged in the stacking (Z) direction, wherein the second plate (12) has at least a first bend (121) defining a first angled part (12a) of the plate having an extension deviating from the horizontal direction, wherein the second plate (12) has at least a second bend (122) defining a second angled part (12b) of the plate having an extension deviating from the horizontal direction in a different direction than the first angled part (12a), and wherein a distance (d) of any of the first and the second interspaces (21, 22) is less than a thickness (t) of any of the plates (11, 12, 13).

Description

[0001] PLATE STACK

[0002] Technical field

[0003] The present invention relates to a plate stack, a system comprising the plate stack and a method of manufacturing a plate stack.

[0004] Background of the invention

[0005] Plate stacks can be permanently joined by different technologies. Joints may be formed by a joining method in which the plates are subjected to a heat lower than the melting point of the plates. Such joining methods may be brazing with an added brazing material in the form of a foil, a paste, or a powder comprising e.g., copper or nickel.

[0006] The above techniques are commonly used for permanently joining corrugated metal plates of permanently sealed heat exchangers. The corrugations of opposing plates contact each other at well-defined contact points. The melted brazing material will accumulate at the contact points between the corrugated plates due to capillary forces and wet the contact point and this ensures a proper leak free joint between the plates.

[0007] Permanently joining of substantially flat plates is however much more challenging than joining corrugated plates as with flat plates there are no well-defined contact points between the plates. Substantially flat plates are particular useful for manufacturing fuel cells, electrolysers or similar, but can also be used in some heat exchanger applications. Substantially flat plates are understood to mean plates defining a plane surface which is intended to be joined to a corresponding plane surface of an opposing plate. However, the plates typically have thoroughgoing channels and port holes for accommodating fluids.

[0008] The flat plates are typically permanently joined along the edges of the substantially flat plates or along the port holes by applying brazing material at the edges of the substantially flat plates. However, it will typically not result in a leak free joint. As the opposing plates in practice cannot be positioned perfectly flat relative each other there will typically be a random contact point between the plates when stacked. During stacking of the plates, there will always be areas where there will be more of less play between the opposing plates. Since the capillary forces are stronger at areas with less distance between the opposing plates and weaker at areas with more distance between the opposing plates, the melted brazing material or plate material will flow from the areas with more play, i.e. greater distance, between the opposing plates to areas with less play, i.e. smaller distance, between the opposing plates. Thus, the areas with more play between the plates may not receive a sufficient amount of melted material and thus may not be sufficiently joined, and there may be leaks at those locations. This is considered a fault.

[0009] It is also difficult to ensure that the flat plates are joined at the correct location, i.e. adjacent the edge or adjacent port holes, using flat plates. In case the smallest distance between the plates is closer to the centre of the plate, there is a risk that all or most of the melted material accumulates at that location. This may also lead to a failure. Below follows a short description of some applications of substantially flat plates:

[0010] Fuel cells make use of substantially flat plates and generate electrical power from an electrochemical reaction between a hydrogen-based fuel and an oxidant. Fuel cells typically comprise a set of fuel cell substrates assembled in series. Each fuel cell substrate includes a plate package of four (or more) substantially flat metal plates. The fuel cell substrate comprising a fuel plate, a separator plate, an oxidant plate and an electrolyte plate positioned between the fuel plate and the oxidant plate. The fuel plate and the oxidant plate each include channels for distributing the fuel and oxidant, respectively. The electrolyte plate comprising an electrolyte material. The separator plate separates the fuel plate and the oxidant plate. An electric current is generated by an electrochemical reaction between the fuel and the oxidant occurring at the electrolyte plate.

[0011] Electrolysers also make use of substantially flat plates that are used to generate hydrogen and oxygen from water by the use of electrical energy. Electrolysers like fuel cells comprise a set of substantially flat metal plates and may face similar challenges as the fuel cell plates.

[0012] The substantially flat plates of fuel cell substrates or electrolysers are successively arranged face to face and joined along their outer edges to be leak tight. They are also joined along port holes. However, as described above, it is very challenging to join flat surfaces due to the lack of a well-defined contact area between the plates. The melted material may therefore, due to capillary forces, accumulate at a random location where there is a small distance or a contact between the plates and leave other areas left open. The likelihood of a fault in the joint is therefore very high. A faulty joint may lead to leaks between the plates. EP 3 301 747 describes an internally manifolded solid oxide fuel cell stack.

[0013] There is thus a need in the art to find technologies for permanently joining flat plates without the above-mentioned drawbacks.

[0014] Summary of the invention

[0015] It is an object of the invention to at least partly overcome one or more limitations of the prior art. In particular, it is an object to provide a stack of substantially flat plates that are permanently joined without faults, such as leakages or failure, e. g. when brazing materials accumulate at one or several non-desired location(s).

[0016] It is a further object of the invention to ensure tight contact between larger, substantially flat surfaces and that the contact between the surfaces is well defined.

[0017] As a first aspect of the invention, there is provided a stack of plates, wherein each plate is substantially flat, and wherein at least one plate includes a bend, the plates stacked one on top of the other along a stacking direction, wherein each plate is extending in a horizontal direction being perpendicular to the stacking direction and being defined by a longitudinal and a transversal direction, the plates defining at least a first plate interspace between a first plate and an opposing second plate and at least a second plate interspace between the second plate and an opposing third plate, wherein the first and the second interspaces are arranged in the stacking direction, wherein the second plate has at least a first bend defining a first angled part of the plate having an extension deviating from the horizontal direction, wherein the second plate has at least a second bend defining a second angled part of the plate having an extension deviating from the horizontal direction in a different direction than the first angled part, and wherein a distance of any of the first and the second interspaces is less than a thickness of any of the plates.

[0018] The plates are generally flat, with one or more of them having bends. The first and second angled parts are extending in a combination of the longitudinal direction and the stacking direction. This could also be a combination of the transversal direction and the stacking direction. The first and second bends are intended bends, and each bend is a distinct and sharp deviation from the horizontal direction. The intended distinct bend of a plate is a slight deviation from the longitudinal or transversal direction of the plate. Thereby the plate deviates from the horizontal direction, so that the plate deviates either upwards or downwards towards the stacking direction. The intended bends give the plate an exact deviation of where the plate deviates from the horizontal direction.

[0019] A number of consecutive plates are arranged in the stack. An opposing plate is defined to be arranged adjacent a neighbouring plate of two consecutive plates. The stack comprises at least three plates defining plate interspaces between each of them. The plate interspaces are typically very small. They essentially define a contact plane between the plates. The distance between two consecutive plates is less than the thickness of a plate. As the plates are typically very thin, this means that a plate normally is less than 1 mm.

[0020] The first angled part of the second plate has an extension that overbridges the second plate interspace and contacts the third plate along a first contact line that is a permanent joint between the second and the third plate, and wherein the second angled part of the second plate has an extension that overbridges the first and the second plate interspace and contacts the first plate along a second contact line that is a permanent joint between the first and the second plate.

[0021] The stack of plates could also be a mirrored version so that the first angled part of the second plate would have an extension that overbridges the first plate interspace and contacts the first plate along a first contact line that is a permanent joint between the first and the second plate, and the second angled part of the second plate would have an extension that overbridges the first and the second plate interspace and contacts the third plate along a second contact line that is a permanent joint between the second and the third plate.

[0022] The bent plate with angled parts meets the consecutive plate at a contact line, i.e. this is the intersection of the bent plate and the neighbouring plate, so that two opposing plate surfaces are joined together. The contact line is a well-defined path in a lengthening direction, i.e. it has a straight extension with a specific length.

[0023] The plates are made of metal such as stainless steel. They are substantially flat meaning that they are not corrugated. A plate having at least one intended bend is also defined to be substantially flat since along most of its extension this is the case, the at least one intended bend is located at its outer edge. Some of the plates for the fuel cell application define port holes and / or channels at the inner region for fuel or oxidizer, however, the plates themselves are substantially flat.

[0024] The bend of a plate will lead to that eventually in the longitudinal direction the plate makes contact with the neighbouring plate, i.e. overbridges the play (interspace) between two consecutive plates so that a well-defined contact area is created between the two plates. So, the contact point between the two consecutive plates will attract melted brazing material or plate material flowing from areas with more play due to that the capillary forces are stronger at areas with less distance between adjacent plates and weaker at areas with more distance between adjacent plates. So, intended bends make a plate meet a neighbouring plate that result in well-defined contact lines that can attract brazing material.

[0025] According to a further embodiment of the first aspect, the first angled part of the second plate has an extension defined by a first angle between the first angled part and the horizontal direction, wherein the second angled part of the second plate has an extension defined by a second angle between the second angled part and the horizontal direction, and wherein the first angle is smaller, larger or equal to the second angle.

[0026] Each of the first and the second angled parts has a rather short extension. Since the intended bends are arranged near an edge of a plate the angled parts define deviations from the horizontal direction near the end part of a plate. This bent plate has its outer edge at approximal the same location as the neighboring plates. Thereby larger areas between substantially flat plates are enclosed by the contact lines and sealed off so that the areas are leak proof.

[0027] According to a further embodiment of the first aspect, the stack of plates defining at least a third plate interspace in the stacking direction between the third plate and an opposing fourth plate, wherein the third plate has a third bend defining a third angled part of the plate having an extension deviating from the horizontal direction, wherein the third angled part of the third plate has an extension that overbridges the third plate interspace and contacts the fourth plate along a third contact line that is a permanent joint between the third and the fourth plate, and wherein the third angled part of the third plate has an extension defined by a third angle between the third angled part and the horizontal direction. This is an embodiment having two consecutive plates with bent parts; one plate having two angled parts and the neighbouring plate having one angled part. Each bent plate makes contact with a further opposite plate, respectively. The stack of plates could also be a mirrored version so that the second plate has one bend, and the third plate has a first and second bend, such that the second plate contacts the first plate along a contact line and the third plate contacts the second and the fourth plate along a contact line, respectively. Hereby, a more complex structure of bent plates is achieved that can seal off areas at different levels in a plate stack.

[0028] According to a further embodiment of the first aspect, the first, second and third angle are constant angles along their respective angled parts. So, each angled part has a straight extension; the first angle has a constant value so that the first angled part has the same direction of extension throughout its length, the second angle has a constant value so that the second angled part has the same direction of extension throughout its length and the third angle has a constant value so that the third angled part has the same direction of extension throughout its length.

[0029] According to a further embodiment of the first aspect, the first contact line contacts the third plate offset in the horizontal direction in relation to the third bend of the third plate. The first contact line may make contact with the third plate either on the horizontal part of the third plate or on the third angled part of the third plate.

[0030] According to a further embodiment of the first aspect, the first contact line contacts the third plate on the third angled part, and wherein the first angle is larger than the third angle. In order for the first contact line to adhere to the third plate on the third angled part the deviation from the horizontal plan needs to be larger for the second plate than for the third plate.

[0031] According to a further embodiment of the first aspect, at least one of the contact lines encircling the plate adjacent an edge of the plate. A contact line may encircle the plates which allows the plate interspace to form an inner region which is fluid tight. Port holes can be used to introduce fuel and oxidiser into the fuel cell and can be encircled at the plate interspaces in which the ports are not used.

[0032] According to a further embodiment of the first aspect, each of the first, second and third angle is in the range of 0 to 20°, specifically 4°-6°, and / or 6°-8°, and / or 8°-9°, and / or 9°-10°, and / or 10°-11°, and / or 11°-13°, and / or 13°-15°, and / or 15°-17°, and / or 17°-19°. According to a further embodiment of the first aspect, the first, second and third contact line are extending in the longitudinal direction, or in the transversal direction. The contact lines follow the contour around the plate stack. The plates are often rectangular, with perpendicular corners.

[0033] According to a further embodiment of the first aspect, the first, second and third contact line are extending along a combination of the longitudinal and the transversal direction. So, the contact lines could also be arranged where the contour does not have perpendicular edges, such as a rounded corner or where the edge is chamfered or bevelled.

[0034] The object is according to a second aspect of the present invention realized by a system comprising the plate stack according to any of the above-mentioned embodiments, the system being a fuel cell or an electrolyser.

[0035] Fuel cells and electrolysers are examples of applications where substantially flat plates are used.

[0036] The object is according to a third aspect of the present invention realized by a method of manufacturing a stack of plates, wherein each plate is substantially flat, and wherein at least one plate includes a bend, comprising the steps of: pressing a plate to comprise at least a first and a second bend defining a first angled part and a second angled part of the plate, arranging the bent plate between two opposing plates in a stacking direction such that a first and a second plate interspace is defined between the plates, and wherein a distance of any of the first and the second interspaces being defined to be less than a thickness of any of the plates, wherein a first contact line between the bent plate and the first opposing plate, a second contact line between the bent plate and the second opposing plate, and permanently joining the plates at the first and second contact lines.

[0037] The method of how a bend can be achieved could be by cutting, bending, drawing, pressing etc.

[0038] According to a further embodiment of the third aspect, the method further comprising the initial step of applying a brazing material onto at least one of the contact lines. Although different technologies can be used for permanently joining the plates, it is preferred to use a brazing material. The brazing material can preferably be applied by printing, such as screen printing, directly on a plate. To reduce the risk of brazing material flowing away, it can be deposited directly onto a plate where the contact line will be established. Printing techniques can be used for an accurate deposit of brazing material onto the plate at the location of where the contact line will be made.

[0039] Brazing material has a melting temperature lower than the metal of the plates and thus when the plates are heated above the melting point of the brazing material, it becomes liquid and fills the gap between the plates by capillary action. When cooled down the brazing material solidifies to form the joint.

[0040] According to a further embodiment of the third aspect, at least one of the contact lines encircling the plate adjacent an edge of the plate.

[0041] The above method according to the third aspect is preferably used together with the stack of plates according to the first aspect.

[0042] Brief description of the

[0043] Figure 1 is a side cross-sectional view of a stack with a number of plates.

[0044] Figure 2 is a side cross-sectional view of a stack with three plates.

[0045] Figure 3 is a side cross-sectional view of a stack with four plates.

[0046] Figure 4 is a perspective view and a closeup of a stack after permanent joining of plates according to Figure 3.

[0047] Detailed

[0048] FIG. 1 discloses a perspective view of a stack of substantially flat plates 100, stacked on top of each other. The plates are stacked in a stacking direction, defined by an axis Z. Each plate is extending in a horizontal direction that is perpendicular to the stacking direction and defined by a longitudinal and a transversal direction. The longitudinal direction is defined by an axis X and the transversal direction is defined by an axis Y. The three axes are defined according to the cartesian coordinate system.

[0049] The plates have substantially the same area and are stacked on top of each other having substantially the same location, to leave substantially the same footprint, i.e. having approximately the same extension of the outer edges seen in the X-Y direction. The plates are arranged consecutively; a first plate followed by a next second plate, etc. An exemplary set of plates is illustrated. A plate stack normally comprises at least three plates.

[0050] FIG. 2 shows an embodiment having a plate stack with three plates. A first plate 11 , a second plate 12 and a third plate 13 are shown at one of their outer ends. The first plate 11 is the top plate in this embodiment and the second plate 12 is arranged between the first and the third plate 11 , 13. The plates are arranged parallelly on top of each other, and between two consecutive plates there is an interspace. Between the first and the second plate 11 , 12 there is a first interspace 21 and between the second and the third plate 12, 13 there is a second interspace 22. Each plate has a thickness defined as a distance t in the stacking direction Z. Each interspace has a distance d between two neighbouring plates, i.e. the distance between their opposing surfaces, defined in the stacking direction Z.

[0051] All three plates are substantially flat. However, the second plate 12 deviates from the horizontal extension near its outer edge by having a first bend 121 and a second bend 122. The first bend 121 gives the plate an extension deviating from the horizontal direction, the deviation is defined by a first angle a in relation to the horizontal direction. Thereby a first angled part 12a of the second plate 12 is defined. The first angled part 12a meets the third plate 13 at a first contact line 41. And at this location of the second plate 12 a second bend 122 gives the plate another deviation from the horizontal direction defined by a second angle p. The second plate eventually meets the first plate 11 along a second contact line 42, which is the outer edge of the second plate 12. The part of the second plate between the first and the second contact line 41 , 42 is a second angled part 12b. The contact lines 41, 42 follow the contour of the plate stack at an intersection between two plates. So, the contact lines 41 , 42 are encircling the plate stack adjacent an edge.

[0052] FIG. 3 discloses an embodiment having a plate stack with four plates. A first plate 11 , a second plate 12, a third plate 13 and a fourth plate 14 are arranged and illustrated at an outer end of the plate stack. The first plate 11 is the top plate in this embodiment and the second plate 12 and the third plate 13 are arranged between the first and the fourth plate 11, 14. The plates are arranged parallelly on top of each other, opposite to each other. Between two consecutive plates there is an interspace. Between the first and the second plate 11, 12 there is a first interspace 21 , between the second and the third plate 12, 13 there is a second interspace 22, and between the third and the fourth plate 13, 14 there is a third interspace 23. All four plates are substantially flat. However, the second plate 12 deviates from the horizontal extension near its outer edge by having a first bend 121 and a second bend 122. The first bend 121 gives the plate an extension deviating from the horizontal direction, the deviation is defined by a first angle a in relation to the horizontal direction. So, a first angled part 12a of the second plate 12 is defined. The first angled part 12a meets the third plate 13 at a first contact line 41 . And at this location of the second plate 12 a second bend 122 gives the plate another deviation (than the first angled part 12a) from the horizontal direction defined by a second angle p. The second plate eventually meets the first plate 11 along a second contact line 42, which is located at the outer edge of the second plate 12. The part of the second plate between the first and the second contact line 41, 42 is defined as a second angled part 12b. The third plate 13 deviates from the horizontal extension at its outer edge by having a third bend 131. The third bend 131 gives the plate an extension deviating from the horizontal direction, the deviation is defined by a third angle y in relation to the horizontal direction. Thereby a third angled part 13a of the third plate 13 is defined. The third angled part 13a meets the fourth plate 14 at a third contact line 43, which is located at the outer edge of the third plate 13 and near the outer edge of the fourth plate 14.

[0053] The contact line 41 of the second plate 12 meets the third plate 13 slightly offset from the third bend 131. Thus, the contact line 41 and the third bend 131 are not located at the same location seen in the horizontal direction i.e. , the longitudinal direction X and the transversal direction Y.

[0054] The angled parts are extending in a combination of the longitudinal direction and the stacking direction, X-Z or in a combination of the transversal direction and the stacking direction, Y-Z. The first and second bends are intended bends, and each bend is a distinct and sharp deviation from the horizontal direction.

[0055] The joining technique used can be brazing as previously described. Brazing material has a melting temperature lower than the metal of a plate. So, the plates are heated above the melting point of the brazing material, the brazing material applied to the plates becomes liquid and fills the gap between the plates by capillary action. Capillary forces are stronger where an interspace between two consecutive plates is smaller and thus, liquified brazing material will gather at locations where there is a narrow distance between plates. The brazing material solidifies when cooling down and forms a joint. The joints are thereby defined in connection to the contact lines i.e., around the contact lines. Also, in FIG. 3 each plate has a thickness defined as a distance t, and each interspace has a distance d between two neighbouring plates, defined in the stacking direction Z, as in FIG.

[0056] 2. This is not included in the figure.

[0057] All angles are constant angles along their respective angled parts. This means that each angled part has a straight extension. The first angle a has a constant value so that the first angled part has the same direction of extension throughout its length, the second angle p has a constant value so that the second angled part has the same direction of extension throughout its length and the third angle y has a constant value so that the third angled part has the same direction of extension throughout its length.

[0058] The angles are typically in the range of 0° to 20°, wherein each of the first, second and third angle is in the range of 4°-6°, and / or 6°-8°, and / or 8°-9°, and / or 9°-10°, and / or 10°-11 °, and / or 11°-13°, and / or 13°-15°, and / or 15°-17°, and / or 17°-19°. In figure 3 this could represent that the first angle a could have a value of 8°-15°, the second angle p could have a value of 17°-20° and the third angle y could have a value of 4°-8°.

[0059] The contact lines 41 , 42, 43 encircle the plate stack adjacent an edge, so the contact lines are arranged at the outskirts of the plates, which means that they are arranged close to the outer edge of the plates.

[0060] Only exemplary embodiments of plate stacks have been disclosed. Further embodiments of plates arranged on top of each other with more than four plates could also be envisaged. So, that other combinations of plates in plate stacks can be made. However, the two outermost plates i.e., the first and the last plate in the stacking direction are substantially flat plates without any intended bends.

[0061] FIG. 4 shows a perspective view of an embodiment of a plate stack 100’ consisting of the plates in FIG. 3 when the plates have been permanently joined. The plates of FIG. 3 have been used as an example; the plate stack could also consist of the three plates of FIG. 2 or a larger number of plates. The plate stack comprises port holes.

[0062] When manufacturing the plate stack the intended bends of the plates can be achieved by cutting, bending, drawing, pressing, etc. Different technologies could be applied for permanently joining the plates into a plate stack, preferably a brazing material is used. Although in the present disclosure the plates are described to be permanently sealed together by brazing, it is understood by a person having ordinary skill in the art that fusion bonding or similar methods also could be used.

[0063] The plates, angles and plate interspaces described herein have been exaggerated for better visibility.

[0064] REFERENCE LIST

[0065] 11: first plate

[0066] 12: second plate

[0067] 12a: first angled part of second plate

[0068] 12b: second angled part of second plate

[0069] 13: third plate

[0070] 13a: third angled part of third plate

[0071] 14: fourth plate

[0072] 21: first plate interspace

[0073] 22: second plate interspace

[0074] 23: third plate interspace

[0075] 41: first contact line

[0076] 42: second contact line

[0077] 43: third contact line

[0078] 100: stack of plates

[0079] 100’: stack of plates

[0080] 121 : first bend of second plate

[0081] 122: second bend of second plate

[0082] 131 : third bend of third plate

[0083] X: longitudinal direction

[0084] Y: transversal direction

[0085] Z : stacking direction a: first angle (of second plate)

[0086] 3: second angle (of second plate) y: third angle (of third plate) t: plate thickness d: distance of interspace

Claims

Claims1. A stack (100, 100’) of plates, wherein each plate is substantially flat, and wherein at least one plate includes a bend, the plates stacked one on top of the other along a stacking (Z) direction, wherein each plate is extending in a horizontal direction being perpendicular to the stacking direction and being defined by a longitudinal (X) and a transversal (Y) direction, the plates defining at least a first plate interspace (21) between a first plate (11) and an opposing second plate (12) and at least a second plate interspace (22) between the second plate (12) and an opposing third plate (13), wherein the first and the second interspaces (21 , 22) are arranged in the stacking (Z) direction, wherein the second plate (12) has at least a first bend (121) defining a first angled part (12a) of the plate having an extension deviating from the horizontal direction, wherein the second plate (12) has at least a second bend (122) defining a second angled part (12b) of the plate having an extension deviating from the horizontal direction in a different direction than the first angled part (12a), wherein a distance (d) of any of the first and the second interspaces (21 , 22) is less than a thickness (t) of any of the plates (11, 12, 13), wherein the first angled part (12a) of the second plate (12) has an extension that overbridges the second plate interspace (22) and contacts the third plate (13) along a first contact line (41) that is a permanent joint between the second and the third plate (12, 13), and wherein the second angled part (12b) of the second plate (12) has an extension that overbridges the first and the second plate interspace (21 , 22) and contacts the first plate (11) along a second contact line (42) that is a permanent joint between the first and the second plate (11 , 12).

2. The stack of plates according to claim 1 , wherein the first angled part (12a) of the second plate (12) has an extension defined by a first angle (a) between the first angled part (12a) and the horizontal direction, wherein the second angled part (12b) of the second plate (12) has an extension defined by a second angle (|3) between the second angled part (12b) and the horizontal direction, and wherein the first angle (a) is smaller, larger or equal to the second angle (p).

3. The stack of plates according to any of the preceding claims, wherein the stack of plates defining at least a third plate interspace (23) in the stacking (Z) direction between the third plate (13) and an opposing fourth plate (14), wherein the third plate (13) has a third bend (131) defining a third angled part (13a) of the plate having an extension deviating from the horizontal direction, wherein the third angled part (13a) of the third plate (13) has an extension that overbridges the third plate interspace (23) and contacts the fourth plate (14) along a third contact line (43) that is a permanent joint between the third and the fourth plate (13, 14), and wherein the third angled part (13a) of the third plate (13) has an extension defined by a third angle (y) between the third angled part (13a) and the horizontal direction.

4. The stack of plates according to any of the preceding claims, wherein the first, second and third angle (a, p, y) are constant angles along their respective angled parts.

5. The stack of plates according to claim 3 or 4, wherein the first contact line (41) contacts the third plate (13) offset in the horizontal direction in relation to the third bend (131) of the third plate (13).

6. The stack of plates according to any of claims 3-5, wherein the first contact line (41) contacts the third plate (13) on the third angled part (13a), and wherein the first angle (a) is larger than the third angle (y).

7. The stack of plates according to any of claims1-6, wherein at least one of the contact lines (41 , 42, 43) encircling the plate adjacent an edge of the plate.

8. The stack of plates according to any of claims 2-7, wherein each of the first, second and third angle (a, p, y) is in the range of 0 to 20°.

9. The stack of plates according to any of claims 1-8, wherein the first, second and third contact line (41 , 42, 43) are extending in the longitudinal (X) direction, or in the transversal (Y) direction.

10. The stack of plates according to any of claims 1-8, wherein the first, second and third contact line (41 , 42, 43) are extending along a combination of the longitudinal (X) and the transversal (Y) direction.

11. The stack of plates according to any of the preceding claims, wherein the permanent joint is a brazed joint.

12. A system comprising the stack of plates according to any of the preceding claims, the system being a fuel cell or an electrolyzer.

13. A method of manufacturing a stack of plates, wherein each plate is substantially flat, and wherein at least one plate includes a bend, comprising the steps of: pressing a plate to comprise at least a first and a second bend defining a first angled part and a second angled part of the plate, arranging the bent plate between two opposing plates in a stacking direction such that a first and a second plate interspace is defined between the plates, wherein a distance (d) of any of the first and the second interspaces being defined to be less than a thickness (t) of any of the plates, wherein a first contact line is defined between the bent plate and the first opposing plate, wherein a second contact line is defined between the bended plate and the second opposing plate, and permanently joining the plates at the first and second contact lines.

14. The method according to claim 13, further comprising the initial step of applying a brazing material onto at least one of the contact lines.

15. The method according to any of the claims 13-14, wherein at least one of the contact lines encircling the plate adjacent an edge of the plate.

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