AU2022416796B2

AU2022416796B2 - Cassette for electrolyzer with porous electrolyte plate

Info

Publication number: AU2022416796B2
Application number: AU2022416796A
Authority: AU
Inventors: Helge Nielsen
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 2021-12-17
Filing date: 2022-12-14
Publication date: 2025-03-06
Anticipated expiration: 2042-12-14
Also published as: AU2022416796A1; US20250051934A1; WO2023111051A3; EP4448846A2; WO2023111051A2

Abstract

An electrolyte plate (3a, 3c) for an electrolyzer cassette (1), the electrolyzer cassette (1) further comprising at least one cooling plate (2), is disclosed. The electrolyte plate (3a, 3c) is formed with at least one opening (7in, 7out) for a cooling fluid to pass the electrolyte plate (3a, 3c), at least one electrolyte fluid inlet (8in, 9in) for an electrolytic fluid to pass the electrolyte plate (3a, 3c), and at least one gas outlet (8out, 9out) for a gas to pass the electrolyte plate (3a, 3c). A porous area is formed between the at least one electrolyte fluid inlet (8in, 9in) and the at least one gas outlet (8out, 9out), the porous area being formed with openings (11) adapted to pass gas across the electrolyte plate (3a, 3c) between a membrane (4) to be positioned at the one side of the electrolyte plate (3a, 3c), and an electrolyte fluid path (6a, 6c) positioned at the other side of the electrolyte plate (3a, 3c).

Description

CASSETTE FOR ELECTROLYZER WITH POROUS ELECTROLYTE PLATE

BACKGROUND OF THE INVENTION

Power-to-X relates to electricity conversion, energy storage, and reconversion pathways that use surplus electric power, typically during periods where fluctuating renewable energy generation exceeds load.

Electrolyzers are devices that use electricity to drive an electrochemical reaction to break, e.g., water into hydrogen and oxygen. The construction of an electrolyzer is very similar to a battery or fuel cell; it consists of an anode, a cathode, and an electrolyte.

The hydrogen produced from an electrolyzer is perfect for use with hydrogen fuel cells. The reactions that take place in an electrolyzer are very similar to the reactions in fuel cells, except the reactions that occur in the anode and cathode are reversed. In a fuel cell, the anode is where hydrogen gas is consumed, and in an electrolyzer, the hydrogen gas is produced at the cathode. A very sustainable system can be formed when the electrical energy needed for the electrolysis reaction comes from renewal energy sources, such as wind or solar energy systems.

Direct current electrolysis (efficiency 80-85% at best) can be used to produce hydrogen which can, in turn, be converted to, e.g., methane (CH4) via methanation, or converting the hydrogen, along with CO2, to methanol, or to other substances.

The energy, such as hydrogen, generated in this manner, e.g. by means of wind turbines, then can be stored for later usage.

Electrolyzers can be configured in a variety of different ways, and are generally divided into two main designs: unipolar and bipolar. The unipolar design typically uses liquid electrolyte (alkaline liquids), and the bipolar design uses a solid polymer electrolyte (proton exchange membranes).

Alkaline water electrolysis has two electrodes operating in a liquid alkaline electrolyte solution of potassium hydroxide (KOH) or sodium hydroxide (NaOH). These electrodes are separated by a diaphragm, separating the product gases, oxygen, O2, and hydrogen, H2, and transporting the hydroxide ions (OH-) from one electrode to the other. Other fuels and fuel cells include phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, and all their subcategories as well. Such fuel cells are adaptable for use as an electrolyzer as well.

It is an advantage if the fluid solutions operating in the plant are within given temperatures to optimize the efficiency. It is also an advantage if the plant could be compact and scalable.

DESCRIPTION OF THE INVENTION

It is an object of embodiments of the invention to provide an electrolyte plate for an electrolyzer, the electrolyzer being easily producible, efficient and scalable.

The invention provides an electrolyte plate for an electrolyzer cassette, the electrolyzer cassette further comprising at least one cooling plate, where the electrolyte plate is formed with at least one opening for a cooling fluid to pass the electrolyte plate, at least one electrolyte fluid inlet for an electrolytic fluid to pass the electrolyte plate, and at least one gas outlet for a gas to pass the electrolyte plate, and where a porous area is formed between the at least one electrolyte fluid inlet and the at least one gas outlet, the porous area being formed with openings adapted to pass gas across the electrolyte plate between a membrane to be positioned at the one side of the electrolyte plate, and an electrolyte fluid path positioned at the other side of the electrolyte plate.

Thus, the invention provides an electrolyte plate, e.g. in the form of an anodic electrolyte plate or a cathodic electrolyte plate. The electrolyte plate is configured to form part of an electrolyzer cassette, which also comprises at least one cooling plate. The at least one cooling plate allows for cooling of an electrolytic fluid flowing in an electrolyte path along the electrolyte plate.

The electrolyzer cassette may, e.g., comprise two electrolyte plates, in the form of one anodic electrolyte plate and one cathodic electrolyte plate, and two cooling plates. The plates may be arranged in such a manner that a cooling path is formed between the cooling plates, an anodic electrolyte path is formed between one of the cooling plates and the anodic electrolyte plate, and a cathodic electrolyte path is formed between the other cooling plate and the cathodic electrolyte plate. This allows a cooling fluid flowing in the cooling path to provide cooling to an anodic electrolytic fluid flowing in the anodic electrolyte path as well as to a cathodic electrolytic fluid flowing in the cathodic electrolyte path. Accordingly, a suitable temperature of the anodic electrolytic fluid as well as of the cathodic electrolytic fluid can thereby be obtained. This ensures that the electrolyzer is able to operate in an efficient manner.

The electrolyzer cassette may be stacked with several other electrolyzer cassettes to form an electrolyzer. This will be described in further detail below.

The electrolyte plate is formed with at least one opening for a cooling fluid to pass the electrolyte plate, at least one electrolyte fluid inlet for an electrolytic fluid to pass the electrolyte plate, and at least one gas outlet for a gas to pass the electrolyte plate. Accordingly, cooling fluid as well as electrolytic fluid (mainly in liquid form) being supplied to electrolyte paths and electrolytic fluid (mainly in gaseous form) leaving the electrolyte paths, can pass through the electrolyte plate. This will allow such fluids to be supplied to and retrieved from the relevant flow paths when the electrolyte plate forms part of an electrolyzer cassette, and also when such an electrolyzer cassette is stacked with other electrolyzer cassettes to form an electrolyzer.

A porous area is formed in the electrolyte plate between the at least one electrolyte fluid inlet and the at least one gas outlet. When the electrolyte plate forms part of an electrolyzer cassette, electrolytic fluid will typically enter an electrolyte fluid path extending along the electrolyte plate, via at least one of the at least one electrolyte fluid inlet, and leave the electrolyte fluid path via at least one of the at least one gas outlet. Since the porous area is formed between the at least one electrolyte fluid inlet and the at least one gas outlet, the electrolytic fluid flowing in the electrolyte fluid path passes the porous area.

The porous area is formed with openings adapted to pass gas across the electrolyte plate between a membrane to be positioned at the one side of the electrolyte plate and an electrolyte fluid path positioned at the other side of the electrolyte plate. When electrolyzer cassettes are stacked into an electrolyzer, an anodic electrolyte plate of one electrolyzer cassette will be arranged adjacent to a cathodic electrolyte plate of a neighbouring electrolyzer cassette, and a membrane will be arranged between the anodic electrolyte plate and the cathodic electrolyte plate. This allows transport of hydronic ions (H ) from the cathodic electrolyte plate to the anodic electrolyte plate, via the membrane, while keeping the product gases resulting from the electrolysis (e.g. O2 and H2, respectively) separated.

The porous area with the formed openings increases the surface area of the electrolyte plate. The increase of the surface of the electrolyte plates results in the increased generated current, and therefore increased rate of electrolysis. The production of the openings of the electrolyte plates, i.e. the bending outwards, improves the production process efficiency and reduces material waste. In other words, it increases the material resources efficiency since all the material needed to produce the electrolyte plates is used.

The electrolyte plate may be porous at least in an area adapted to match with a membrane, allowing the diffusion of product gases and ions. According to this embodiment, the porous area of the electrolyte plate matches an area of the membrane, in the sense that the entire membrane is arranged in contact with the porous area. This allows diffusion of product gasses and ions in the entire area of the membrane.

The openings formed in the porous area may be formed by a semi-cut allowing cut-out portions to form flaps being bend outwards. According to this embodiment, cuts are made in the electrolyte plate. The cuts define flaps which are then bend outwards, to thereby create the openings forming the porous area.

The opposite surface of the electrolyte plate to the one in the bending direction of the flaps may be essentially flat. According to this embodiment, the bend outwards flaps protrude from one side of the electrolyte plate, whereas the opposite side of the electrolyte plate is essentially flat, i.e. essentially without such protrusions. The side of the electrolyte plate with the protruding bend outwards flaps may face the electrolyte fluid path, while the opposite, essentially flat side may face the membrane.

A recess may be formed around the openings formed in the porous area. According to this embodiment, the recess helps in guiding gasses, such as hydrogen or oxygen, towards the openings.

The recess may extend in a length direction of the electrolyte plate. According to this embodiment, the gasses are guided towards the openings essentially along the length direction of the electrolyte plate, and thereby essentially in the flow direction of electrolytic fluid in the electrolyte fluid path. This ensures a smooth flow of gas through the openings.

The recess may cover a plural of the openings formed in the porous area. According to this embodiment, a given recess guides gasses towards several openings. This is an easy manner of ensuring a smooth flow of gas through several openings.

The recess may be formed at a surface of the electrolyte plate adapted to face the membrane. In the case that the openings are formed by protrusions, such as bend outwards portions, protruding from the surface of the electrolyte plate facing the electrolyte fluid path, the surface facing the membrane may be essentially flat. Forming the recess in this surface ensures that the interface towards the membrane remains essentially flat, resulting in a firm contact between the electrolyte plate and the membrane.

Each of the openings formed in the porous area may be formed by two cuts, and the section between the two cuts may form a pushed outwards section, which contacts the rest of the electrolyte plate at two positions. According to this embodiment, the openings of the porous area are formed by, for each opening, providing two cuts in the electrolyte plate, e.g. two essentially parallel cuts. The section arranged between the two cuts is then pushed outwards, thereby creating a gap between the pushed outwards section and the rest of the electrolyte plate, the gap defining two openings corresponding to the two original cuts. This gap with the two openings forms the opening at the porous area. However, the two end parts of the pushed outwards section, e.g. extending substantially perpendicularly to the two cuts, remain attached to the rest of the electrolyte plate. Accordingly, the pushed outwards section may have a shape which is similar to a bridge or an arch.

The pushed outwards section may be positioned such that at least one of the two openings defined by the two cuts and the pushed outwards section points in the direction of the respective electrolyte gas outlet. Similarly to the embodiment described above, this ensures a smooth flow of gas through the openings formed in the porous area.

The opposite surface of the electrolyte plate to the one in the bending direction of the pushed outwards sections may be essentially flat. Similarly to the embodiment described above, this ensures a good and firm contact between the electrolyte plate and the membrane.

The openings formed in the porous area may be formed by pushed down flanges. According to this embodiment, the openings are formed by pushing a portion of the electrolyte plate outwards while creating a hole or an opening essentially at the centre of the portion being pushed outwards. The creates a flange with a free end, defining a rim of the opening formed at the centre of the portion being pushed outwards.

The pushed down flanges may be positioned such that free ends of the flanges point in the direction of the respective electrolyte gas outlet. Similarly to the embodiments described above, this ensures a smooth flow of gas through the openings formed in the porous area.

The opposite surface of the electrolyte plate to the one in the bending direction of the flanges may be essentially flat. Similarly to the embodiments described above, this ensures a good and firm contact between the electrolyte plate and the membrane. The openings formed in the porous area may be formed with a larger length than width. According to this embodiment, the openings have an elongate shape. The shape and size of the openings influences the flow of gasses (hydrogen or oxygen).

At least some of the openings formed in the porous area may extend in a direction parallel to a length direction L of the electrolyte plate, i.e. the length direction of the openings may be arranged along the length direction L of the electrolyte plate.

Alternatively or additionally, at least some of the openings formed in the porous area may extend in a direction perpendicular to a length direction L of the electrolyte plate, i.e. the length direction of the openings may be arranged substantially perpendicularly to the length direction L of the electrolyte plate.

Alternatively or additionally, at least some of the openings formed in the porous area may be positioned with their length direction at an angle relative to a length direction L of the electrolyte plate. According to this embodiment, at least some of the openings formed in the porous area are arranged with their length direction being neither parallel to, nor perpendicular to, the length direction L of the electrolyte plate. Instead, these openings are arranged with their length direction at an angle to the length direction L of the electrolyte plate, e.g. at an angle within the interval 30 degrees to 60 degrees, such as approximately 45 degrees.

The openings formed in the porous area may have curving shapes being 'meat bone'-shaped. According to this embodiment, the openings have a shape which is similar to the shape of a meat bone, i.e. wider at the ends than at a centre section. The meat bone opening shape is a measure to avoid unwanted deformation of the electrolyzer plates which might occur during the openings pressing out process at the electrolyzer plate. Meat bone shape is the optimum shape for less tension to keep the plate in the right form.

The openings formed in the porous area may have concave sections as well as convex sections. This is, e.g., the case for the 'meat bone'-shape described above. For instance, the two opposing ends of the openings formed in the porous area may be concave seen from the inside of the respective opening, and formed with convex sections at the centre, seen from the inside of the respective opening. Accordingly, as described above, this reduces the risk of unwanted deformation of the electrolyzer plates.

The openings formed in the porous area may be symmetric with two halves mirroring each other. The symmetric feature of the openings evens out the deep drawn stresses induced with pressing forces and reduces or even prevent the occurrence of deformations. The openings formed in the porous area may have a width at a centre portion, which is smaller than an upper width or diameter of a contact column formed in a neighbouring cooling plate when the electrolyte plate and the cooling plate are connected to each other in an electrolyzer cassette. According to this embodiment, the contact column ensures appropriate spacing between the electrolyte plate and the neighbouring cooling plate, and may further ensure electrical contact between the plates. However, this is obtained with minimum obstruction of flow through the openings formed in the porous area due to the contact column.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic illustration of a cassette for an electrolyzer,

Fig. 2 is an illustration of an electrolyzer formed of a stack of cassettes,

Fig. 3A is an illustration of openings in an electrolyte plate formed by a bend section,

Fig. 3B is an illustration of openings in an electrolyte plate formed by a recessed section,

Fig. 3C is an illustration of openings in an electrolyte plate formed by a bend down section,

Fig. 3D is an illustration of openings in an electrolyte plate formed by flanges,

Fig. 3E is an illustration of openings in an electrolyte plate formed by curving sections,

Fig. 3F is an illustration of openings in an electrolyte plate positioned with their length direction being perpendicular to a centre line L of the electrolyte plate,

Fig. 3G is an illustration of openings in an electrolyte plate positioned with their length direction being parallel to the centre line L of the electrolyte plate,

Fig. 3H is an illustration of openings in an electrolyte plate positioned with their length direction at an angle relative to the centre line L of the electrolyte plate,

Fig. 31 is an illustration of openings in an electrolyte plate, where some openings are positioned with their length direction being perpendicular to the centre line L of the electrolyte plate, while other openings are positioned with their length direction being parallel to the centre line L of the electrolyte plate, Fig. 3J is an illustration of openings in an electrolyte plate, where the openings are positioned with their length direction at an angle relative to the centre line L of the of the electrolyte plate, and at two opposite directions relative to each other,

Fig. 3K is an illustration of openings in an electrolyte plate, where some of the openings are absent, or blank,

Fig. 4 is an illustration of areas of an electrolyte plate and a cooling plate, respectively, around the respective electrolyte inlets and cooling fluid openings,

Fig. 5A is an illustration of the area of a cooling inlet opening,

Fig. 5B is an illustration of the area of a cooling inlet opening, illustrating openings formed in projections,

Fig. 5C is an illustration of the area of the cathodic electrolyte gas outlet,

Fig. 5D is an illustration of the area of the anodic electrolyte gas outlet,

Fig. 6 is an illustration of an end section of an electrolyte plate or a cooling plate in the area of the electrolyte gas outlets, showing barriers,

Fig. 7 is an illustration of the area of the anodic electrolyte gas outlet, showing an external gasket with beads,

Figs. 8A and 8B are illustrations of membrane fixing between two gasket parts,

Fig. 9 is an illustration of cooling cells of the cooling plate,

Fig. 10 is an illustration of cooling cells of two cooling plates contacting by crossing projections,

Fig. 11 is a side-view of cooling plates and electrolyte plates forming part of an electrolyzer cassette according to the present invention, showing contact columns, and

Figs. 12A and 12B illustrate possible geometric relationships between contact columns of a cooling plate. DETAILED DESCRIPTION OF THE DRAWINGS

The detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only.

Fig. 1 illustrates a basic setup of a cassette 1 for an electrolyzer according to the present invention. The cassette 1 is formed of two cooling plates 2 and two electrolyte plates 3a, 3c, respectively an anodic plate 3a, and a cathodic plate 3c.

Each cooling plate 2 is patterned, and one side of one of the cooling plates 2 connects to an anodic plate 3a, and the other of the two cooling plates 2, at one side, connects to a cathodic plate 3c. The two cooling plates 2, at their respective other sides, are connected to each other. Thus, the two cooling plates 2 face each other, at one side, and at the other, opposite side, they each face an electrolyte plate 3a, 3c in the form of an anodic plate 3a and a cathodic plate 3c, respectively.

A cooling path 5 is formed between the two connected cooling plates 2, adapted for a cooling fluid to pass from a cooling fluid inlet 7in to a cooling fluid outlet 7out.

Similarly, an anodic electrolyte path 6a is formed between the anodic plate 3a and the connected one of the cooling plates 2, and a cathodic electrolyte path 6c is formed between the cathodic plate 3c and the connected one of the cooling plates 2.

Electrolyte is fed via an anodic electrolyte fluid inlet Sin into the anodic electrolyte path 6a to replace the electrolyte being transferred into gas (e.g. O2), leaving the anodic electrolyte path 6a via an anodic electrolyte gas outlet 8out. Similarly, electrolyte is fed via a cathodic electrolyte fluid inlet 9in into the cathodic electrolyte path 6c to replace the electrolyte within the cathodic electrolyte path 6c being transferred into gas (e.g. H2), leaving the cathodic electrolyte path 6c via a cathodic electrolyte gas outlet 9out.

Fig. 1 illustrates how the electrolyte is positioned like a column within the electrolyte paths 6a, 6c, where the fraction of electrolyte which is formed into gas and leaving the respective electrolyte paths 6a, 6c via the respective electrolyte gas outlets 8out, 9out is replaced by new electrolyte fed into the electrolyte paths 6a, 6c via the respective electrolyte inlets 8in, 9in.

The cassette 1 is adapted for a thin, porous foil, also referred to as a diaphragm or membrane 4, to be positioned between respectively an anodic plate 3a and a cathodic plate 3c of two connected cassettes 1 (see also Fig. 2). The membrane 4 is electrically insulating, or nonconductive, in order to avoid electrical shorts between the electrolyte plates 3a, 3c.

The membranes 4 may be connected at the outside surfaces of the electrolyte plates 3a, 3c relative to respectively the anodic electrolyte path 6a and cathodic electrolyte path 6c, and may be fixed by a clip-on gasket to be described in more detail later.

An electrolyte solution, e.g. potassium hydroxide (KOH) or sodium hydroxide (NaOH), is fed to the anodic electrolyte path 6a via the anodic electrolyte fluid inlet 8in, and to the cathodic electrolyte path 6c via the cathodic electrolyte fluid inlet 9in.

Fig. 2 illustrates three cassettes 1 connected side-by-side with membranes 4 squeezed between them, separating the product gases and allowing the transport of the hydroxide ions (OH-) from the cathodic plate 3c to the anodic plate 3a, generating gas oxygen in the anodic electrolyte path 6a and hydrogen in the cathodic electrolyte path 6c. The oxygen and the hydrogen may then be collected at the anodic gas outlet 8out and the cathodic gas outlet 9out, respectively.

The electrolyte plates 3a, 3c are porous, at least in the area adapted to match with the membrane 4, allowing the diffusion of the product gases and the transportation of hydroxide ions (OH-) across the membranes 4, and hence the porous areas of the electrolytic plates 3a, 3c.

Figs. 3A-3J illustrate different embodiments of such pores, or electrolyte plate openings 11.

Fig. 3A illustrates an embodiment where electrolyte plate openings 11 are formed as flaps Ila formed by a cut allowing the cut-out portions to form flaps Ila to be bend outwards. The opposite surface of the electrolyte plate 3a, 3c to the one in the bending direction of the flaps Ila is essentially flat. The electrolyte plate 3a, 3c is positioned with the flat surface facing outwards relative to the connected cooling plate 2, to form a contact surface to the membrane 4.

The flaps Ila reach towards the cooling plate 2 arranged adjacent to the electrolyte plate 3a, 3c, possibly without contacting it, and thus into the respective electrolyte path 6a, 6c. The flaps Ila may be positioned such that they 'point' in the direction of the respective electrolyte gas outlet 8out, 9out, thereby ensuring a smooth flow of the entering gasses, such as hydrogen or oxygen gasses. Fig. 3B illustrates the same embodiment as Fig. 3A with bend out flaps I la, but where a recess 12 is formed around the electrolyte plate openings 11, possibly extending in a length direction of the electrolyte plate 3a, 3c, and possibly covering a plural of electrolyte plate openings 11. A plural of such recesses may be formed in each electrolyte plate 3a, 3c, and some or all of the electrolyte plate openings 11 may be positioned within such a recess 12.

The recess 12 is formed at the otherwise flat surface adapted to face the membrane 4, and is formed in order to ease and direct the flow of gasses, such as hydrogen and oxygen, from the membrane 4 towards the openings 11.

Fig. 3C illustrates an embodiment where the electrolyte plate openings 11 are formed by two cuts, and where the section between the two cuts forms a pushed outwards section 11b, being, e.g., 'bridge-shaped', 'bow-shaped', 'arch-shaped', etc. The pushed outwards section 11b is contacting the rest of the electrolyte plate 3a, 3c at two positions, forming opposite ends of the pushed outwards section 11b, along a direction defined by the two cuts.

The pushed outwards section 11b could be positioned such that at least one of the two openings 11 formed below the pushed outwards section 11b points in the direction of the respective electrolyte gas outlet 8out, 9out. This ensures a smooth flow of the entering gasses, such as hydrogen or oxygen gasses.

The opposite surface of the electrolyte plate 3a, 3c to the one in the bending direction of the pushed outwards sections 11b is essentially flat. The electrolyte plate 3a, 3c is positioned with the flat surface facing outwards relative to the connected cooling plate 2, to form a contact surface to the membrane 4.

The pushed outwards sections 11b will then face the respective cooling plate 2, preferably without contacting it, and thus extend into the respective electrolyte path 6a, 6c.

Fig. 3D illustrates an embodiment where the electrolyte plate openings 11 are formed by pushed down openings forming flanges 11c. This is an easy construction, in terms of production, and the substantially smooth transition of flanges 11c enables a smooth flow of gasses, such as hydrogen and oxygen, into the respective electrolyte paths 6a, 6c.

The flanges 11c could be positioned such that free ends of the flanges 11c point in the direction of the respective electrolyte gas outlet 8out, 9out. This ensures a smooth flow of the entering gasses, such as hydrogen or oxygen gasses. The opposite surface of the electrolyte plate 3a, 3c to the one in the bending direction of the flanges 11c is essentially flat. The electrolyte plate 3a, 3c is positioned with the flat surface to form a contact surface to the membrane 4.

The flanges 11c will then reach towards the respective cooling plate 2, preferably without contacting it, and thus into the respective electrolyte path 6a, 6c.

Fig. 3E illustrates an embodiment where the electrolyte plate openings 11 are formed with a larger length than width, and they may be orientated in at least two different orientations lid, lie, Ilf, as will be described below with reference to Figs. 3F-3J.

In the illustrated embodiment, the opening 11 has a curving shape, similar to a meat bone, and may therefore be referred to as being 'meat bone'-shaped. This means that the opening 11 has concave sections as well as convex sections. In the illustrated embodiment, the two ends arranged opposite each other along a direction defined by the length of the opening 11 are concave seen from the inside of the opening lid, lie, and convex sections are present at the centre part, seen from the inside of the opening lid, lie. The ends, thus, may form part of a circular or elliptic shape. The convex sections are having a width X which is smaller than the width Y of the concave section. The angle between the line (D) defined by two points (A and B) and the horizontal axis (H) is between 5° and 20°.

The opening l id, lie, Ilf may be symmetric with two halves mirroring each other.

Fig. 3F illustrates an embodiment where the openings lid are positioned with their length direction being perpendicular to a centre line L passing in a length direction of the cassette 1. The centre line L is further parallel to the overall direction of the flow of the cooling fluid from the cooling fluid inlet 7in to the cooling fluid outlet 7out.

The centre line L also corresponds to a line parallel to the length direction of the plates 2, 3a, 3c.

Fig. 3G illustrates an embodiment where the openings lie are positioned with their length direction being parallel to the centre line L.

Fig. 3H illustrates an embodiment where the openings Ilf are positioned with their length direction at an angle relative to the centre line, e.g. 45 degrees. Fig. 31 illustrates an embodiment where some openings l id are positioned with their length direction being perpendicular to the centre line L, while other openings lie are positioned with their length direction being parallel to the centre line L. In the illustrated embodiment they are positioned in an array-like structure where each of the one kind of oriented openings lid, lie are flanked at all sides by openings lie, lid of the other orientation. The distance Z, between the width X of the openings lie and the lower end of width X of the openings lid is higher than the width X.

Fig. 3J is basically a combination of the embodiments of Figs. 3H and 31 where the openings Ilf are angled at two opposite directions relative to each other, and with an angle of approximately 45 degrees relative to the centre line L.

Fig. 3K illustrates an embodiment similar to the embodiment of Fig. 3F, but where some of the openings lie are absent, or blank. In other words, there are regions of the electrolyte plate 3a, 3c where there are no openings 11. This allows contact columns 19 formed in the neighbouring cooling plate 2 (see Figs. 9-11) to contact the electrolyte plate 3a, 3c without obstructing the openings 11. Contact columns 19 may, as an alternative, be formed in the electrolyte plate 3a, 3c and reach out towards the neighbouring cooling plate 2. As another alternative, each contact column 19 may be formed from two parts, where one part is formed in the electrolyte plate 3a, 3c and the other part being formed in the neighbouring cooling plate 2, and the two parts contacting each other to form the contact column.

According to one embodiment, the openings 11 may, at the centre portions, have a smaller width than the upper width or diameter of a contact column 19. This ensures that only a part of the opening 11 is obstructed by the contact column 19, while maintaining a contact to the electrolyte plate 3a, 3c.

The embodiment with contact areas for contact columns 19 or the smaller width diameter could also apply to any of the embodiments of Fig. 3A-3J.

An active area of the electrolyte plate 3a, 3c is formed between the electrolyte fluid inlets 8in, 9in and gas outlets 8out, 9out and is formed with the openings 11, i.e. the active area is porous. This active area is adapted to be aligned with the membrane 4.

Fig. 4 shows the area of an electrolyte plate 3a, 3c and a cooling plate 2 around the respective electrolyte gas inlets 8in, 9in and a cooling fluid inlet 7in or cooling fluid outlet 7out. In the illustrated embodiment, cooling fluid openings 7in, 7out, being cooling fluid inlets 7in and/or cooling fluid outlets 7out, are positioned at the corners of the plates 3a, 3c, 2, but they could be positioned elsewhere, such as at the centre of the plates 3a, 3c, 2.

The cooling fluid flow direction in the cooling path 5 could be counter to the electrolyte fluid flow direction in the respective electrolyte paths 6a, 6c. As an alternative, the cooling fluid flow and the electrolyte fluid flow may be in the same direction. The cooling fluid inlet 7in and/or the cooling fluid outlet 7out, respectively, may consist of one or a plural of openings 7in, 7out, such as two openings 7in, 7out as illustrated.

The embodiment further shows an anodic electrolyte inlet Sin and a cathodic electrolyte inlet 9in, respectively, positioned between the two cooling openings 7in, 7out, such as in each their half of the plates 3a, 3c, 2, seen in relation to a centre line L passing in a length direction of the cassette 1, and thereby in a length direction of the plates 3a, 3c, 2. The electrolyte inlets 8in, 9in could, for example, be positioned at or near the centre of each their half.

The electrolyte plates 3a, 3c, and possibly also the cooling plates 2, may be symmetric relative to the centre line L, the left half of a respective plate 3a, 3b, 2 mirroring the right half thereof.

The four plates 3a, 3c, 2 in the cassette 1 are connected such that the cooling openings 7in, 7out are in fluid connection to the cooling path 5, but are sealed from the electrolyte paths 6a, 6c. The anodic electrolyte openings 8in, 8out are sealed from respectively the cooling fluid path 5 and from the cathodic electrolyte openings 9in, 9out. In the same manner, the cathodic electrolyte openings 9in, 9out are sealed from respectively the cooling fluid path 5 and the anodic electrolyte openings 8in, 8out. This is illustrated in more details in Figs. 5A- 5D.

Figs. 5A-5D illustrate the two cooling plates 2 positioned between an anodic electrolyte plate 3a and a cathodic electrolyte plate 3c. Outer gaskets 31 may be positioned at the outer circumference of the respective openings 7in, 7out, 8in, 8out, 9in, 9out to seal towards the externals when connected to another cassette 1. When a plural of cassettes 1 are stacked with their respective openings 7in, 7out, 8in, 8out, 9in, 9out aligned, the openings combine into opening volumes that reach through all four plates 3a, 3c, 2 of all cassettes 1.

Fig. 4 shows that the membrane 4 covers the active area of the electrolyte plate 3a, 3c. The active area is the section between the electrolyte fluid inlets 8in, 9in and the electrolyte gas outlets 8out, 9out, and is where the electrolyte plate openings 11 are positioned. Encircling the active area is a gasket 33', separating the electrolytic fluids within the active area from the electrolyte gas outlets 8out, 9out.

Fig. 5A illustrates the area of a cooling inlet opening 7in, but the area of the cooling outlet opening 7out could be designed in a similar manner, and the remarks set forth below are therefore equally applicable to the cooling outlet opening 7out. The two cooling plates 2 are contacting at the rim and possibly fixed to each other by, e.g., welding or brazing 50.

Projections 55 may be formed in the plates 3a, 3c, 2 at the circumference of the respective openings 7in, 7out, 8in, 8out, 9in, 9out to contact the neighbouring plates 3a, 3c, 2, possibly contacting similar projections 55 formed in the neighbouring plates 3a, 3c, 2. This stabilizes the areas of the respective openings 7in, 7out, 8in, 8out, 9in, 9out.

Openings 56, see also Fig. 5B, forming a part of the cooling fluid inlet 7in, are formed in the projections 55 in order to allow the respective fluids access to the respective flow paths 5, 6a, 6c.

In Figs. 5A and 5B, the flow path is the cooling fluid path 5, in Fig. 5C, the flow path is the cathodic electrolyte path 6c, connecting to the cathodic electrolyte gas outlet 9out, and in Fig. 5D, the flow path is the anodic electrolyte path 6a, connecting to the anodic electrolyte gas outlet 8out.

In Fig. 5A, the opening 56 is seen as a recess 57 in the projection 55 formed in the cooling plate 2. The recess 57 ensures that the projection 55 formed in the cooling plate 2 is not contacting the projection 55 formed in the neighbouring electrolyte plate 3a, 3c. As an alternative, a recess 57 could be formed in only one of the cooling plates 2, or recesses 57 could be formed in both cooling plates 2. If formed in both cooling plates 2 the recesses 57 could be arranged to face each other, or they could be shifted relative to each other.

In Fig. 5A, the recess 57 is formed in both of the cooling plates 2 only, but it could alternatively be formed in either or both electrolyte plates 3c, 3a, or in either or both of the cooling plate 2 as well as in either or both of cathodic plate 3c and the anodic plate 3a.

In Fig. 5C, the recess 57 is formed in only one of the cooling plates 2, i.e. the cooling plate 2 which faces the cathodic plate 3c. In a similar manner, in Fig. 5D, the recess 57 is formed only in the cooling plate 2 which faces the anodic plate 3a. For both of these embodiments, a recess 57 could alternatively be formed in the cooling plate 2 projection 55 connecting to the respective cathodic plate 3c or anodic plate 3a, or in both. Fig. 6 illustrates an embodiment section of one of the electrolyte paths 6a, 6c, i.e. the anodic electrolyte path 6a or the cathodic electrolyte path 6c, in the area around the electrolyte gas outlets 8out, 9out. The cooling plate 2 may be formed in a similar manner in this area.

The electrolyte paths 6a, 6c may comprise a section stretching from the edges 60 of the plates 2, 3a, 3c towards the centre line L and the respective electrolyte gas outlet 8out, 9out.

One of the respective electrolyte gas outlets 8out, 9out will be open to the respective electrolyte path 6a, 6c, whereas the other will be closed, or sealed, e.g. by a gasket 33, in a manner similar to the cooling fluid openings 7in, 7out, and optionally also the circumference edge of the plates 2, 3a, 3c.

In order to partly separate the upper section electrolyte paths 6a, 6c around the electrolyte gas outlets 8out, 9out from the lower sections where the main gas generation occurs, an inner gas barrier 26 is provided, which obstructs the gas from flowing back to the lower section of the active area.

The inner gas barrier 26 may comprise two halves, each declining or sloping towards the centre line L, corresponding to declining or sloping towards the active area, where a drain 27 in the inner gas barrier 26 is positioned, allowing fluids, in particular in the form of liquid, in the section to drip back to the active area for further processing, due to gravity. This further prevents that liquid enters the gas outlet 8out, 9out and is passed further on in the system. This is an advantage, because liquid being passed on may introduce a risk of short circuiting.

The cassette 1 may be adapted to be positioned in a substantially vertical position with the gas outlets 8out, 9out at the top and electrolyte fluid inlets 8in, 9in at the bottom. Then liquids which are not dissolved will tend to fall downwards, due to gravity, and will be collected by the inner gas barrier 26 since they are heavier than the gas. The declining or sloping gas barrier 26 will guide the liquids towards the gas barrier drain 27.

A lower inner gas barrier 26a may be positioned at the gas barrier drain 27, immediately at the side facing the active area below the inner gas barrier drain 27.

The barrier 26, 26a, 27 may be formed in either of the electrolyte plates 3a, 3c or the connected cooling plate 2, or both, and will be adapted to contact the neighbouring plate 2, 3a, 3c. The section illustrated in Fig. 6 may further include gas barriers 24, 25, e.g. formed as corrugations 24 and/or dimples 25, to make the gas flowing in a meandering way to distribute gas and liquid further within the section.

The respective electrolyte gas outlet 8out, 9out is partly surrounded by an outlet blockade 28 only allowing the gas to leave the section and move towards the electrolyte gas outlet 8out, 9out, via an opening 29 in the outlet blockade 28. Facing the lower sections, the outlet blockade 28 may be provided with an outlet blockade drain 30, allowing possibly remaining fluids, primarily in the form of liquids, to drain back to the section.

Barriers, such as the gas barriers 24, the inner gas barrier 26 and the outlet blockade 28, may be formed by projections on the plates 2, 3a, 3c facing each other and being connected, thus obstructing fluid and gas from passing. Similarly, the dimples 25 may be formed by projections, possibly projecting to both sides and contacting at both the opposing sides of a plate 2, 3a, 3c, in order to form support in the section.

Fig. 7 illustrates an embodiment of outer gaskets 31 of the electrolyte gas outlets 8out, 9out formed with 'beads' 32 reaching into the electrolyte gas outlets 8out, 9out, where the beads 32 extend into both electrolyte gas outlets 8out, 9out when connected to other cassettes 1. This prevents fluid from flowing into the gas channels, the electrolyte paths 6a, 6c, and prevents fluid from leaking into the section between the two connected cassettes 1.

Figs. 8A and 8B show an embodiment fixation of the membrane 4 between two connected cassettes 1 by clamping the membrane 4 between two gasket parts 13, 14, a first gasket part 13, for example an EPDM gasket, and a second gasket part 14, for example a Viton gasket.

The membrane 4 is clamped between the two electrolyte plates 3a, 3c of the connected cassettes 1 and placed in grooves 13a' in the electrolyte plates 3a, 3c to hold them in place. For this, the gasket parts 13, 14 may be formed with projections 13', 14' adapted to be positioned within the grooves 13a'.

One gasket part, e.g. the second gasket part 14, is formed with a locking part 15 that extends through a hole 4a in the membrane 4 and a gasket hole 16 of the other gasket part, e.g. the first gasket part 13. The outer part of the locking part 15 has a larger diameter than the hole 4a of the membrane 4 and must therefore be pushed through with a force. This ensures that the membrane 4 and the gasket parts 13, 14 are kept firmly together, and that relative movements therebetween are essentially prevented. Accordingly, it is ensured that the various parts of the cassette 1 remain properly aligned with respect to each other, and the risk of leaking is minimised.

Either of the first gasket part 13 and/or the second gasket part 14 could be provided with respectively locking part(s) 15 and gasket opening(s) 16.

The first gasket part 13 or the second gasket part 14, respectively, could be the gasket 33' encircling the active area.

In an embodiment, the gasket 33' is formed of respectively the first gasket part 13 and the second gasket part 14, these being adapted to seal at each their side of the membrane 4. The respective first gasket part 13 and second gasket part 14 could be formed of different materials suitable for each their environments at the two sides of the membrane 4, the one possibly being made of a cheap material.

Such fixations 4a, 13a', 13', 14', 15, 16 could be positioned at regular intervals at the circumference of the membrane 4.

Fig. 9 illustrates the cooling plates 2 formed with cooling cells 17 distributed at least in the area contacting the electrolyte plate 3a, 3c which is adapted to be covered by the membrane 4, i.e. the active area.

The intention of the cooling cells 17 is to ensure an even distribution of cooling, or the cooling fluid, across the cooling plate 2, and accordingly across the neighbouring electrolyte plate 3a, 3c. Fig. 9 shows only a few of the cooling cells 17 (eight cooling cells 17 in total), and accordingly only a subsection of the cooling plate 2. However, it should be understood that they may be distributed over the entire active area, or at least a substantial part of it, or even over the entire area of the cooling plate 2.

The cooling cells 17 may be formed with a pattern 18 adapted to contact a similar pattern 18 of a connected neighbouring cooling plate 2, forming a cooling path 5 within the cooling cells 17. The pattern 18, however, does not contact the electrolyte plate 3a, 3c positioned at the opposite side, and therefore contact columns 19 are distributed over the cooling plate 2, such as within the cooling cells 17, as illustrated in Fig. 9. The contact columns 19 formed in the respective cooling cells 17 point towards a neighbouring electrolyte plate 3a, 3c, rather than towards a neighbouring cooling plate 2. Accordingly, the contact columns 19 of respective neighbouring cooling plates 2 do not point towards each other or reach into the cooling cells 17 formed between the two cooling plates 2. The contact columns 19 are situated to contact the respective neighbouring electrolyte plate 3a, 3c in the areas between the electrolyte plate openings 11. This ensures support of the plates 2, 3a, 3c as well as a uniform distance between the cooling plates 2 and the electrolyte plates 3a, 3c, across the entire active area, and essentially regardless of the pressure conditions within the electrolyzer cassette. The contact columns 19 may also form the electrical contact to the electrolyte plates 3a, 3c supplying them with a current/voltage.

The contact columns 19 may be fixedly attached to the respective electrolyte plates 3a, 3c, e.g. by welding or soldering. Alternatively, the contact columns 19 may simply be pushed into contact with the respective electrolyte plates 3a, 3c by pressing the plates 2, 3a, 3c together.

In the embodiment illustrated in Fig. 9, the contact columns 19 form part of the cooling plate 2, and are attached to or pushed into contact with the respective electrolyte plates 3a, 3c. As an alternative, the contact columns 19 may form part of the electrolyte plates 3a, 3b, and be attached to or pushed into contact with the cooling plate 2. As another alternative, each contact column 19 may comprise a part forming part of the cooling plate 2 and a part forming part of the electrolyte plate 3a, 3c, and the two parts may be attached to each other or pushed into contact with each other to form the contact column 19.

Each cooling cell 17 is provided with cooling fluid from a cooling cell supply channel 20 extending between the cooling cells 17, via respective cooling cell inlets 21. Each cooling cell supply channel 20 may connect to a plural of cooling cells 17.

The cooling fluid (now with an increased temperature) leaves the cooling cells 17 via a cooling cell outlet 23, and is fed to cooling cell return channels 22, where each cooling cell return channel 22 may connect to a plural of cooling cells 17.

According to one embodiment, the area of the cooling plates 2 formed with cooling cells 17 may be adapted to be aligned with the active area of the electrolyte plates 3a, 3c, enabling a control of the temperature in the gas generating processes occurring in the electrolytic fluids in the electrolyte flow paths 6a, 6c.

The cooling cells 17 are enclosed by a cooling cell wall 17a, where the respective cooling cell inlets 21 and cooling cell outlets 23 are formed in the cooling cell wall 17a. The cooling cell wall 17a separates the individual cooling cells 17 from each other and may be formed as a projection in the two cooling plates 2 connecting to form a flow barrier. Fig. 10 illustrates cooling cells 17 of two cooling plates 2 being positioned on top of each other. The corrugated patterns 18 of the respective cooling cells 17 are positioned to cross each other and contacting in the crossing point defined by the patterns 18. This ensures that the flow of the cooling fluid changes direction when passing through the cooling fluid path 5 within each cooling cell 17, as it flows over and under the corrugations defined by the patterns 18.

The corrugated pattern 18 illustrated in Figs. 9 and 10 is just an embodiment, any other suitable pattern like chevron-shaped, dimples, etc., could also apply.

The cooling cell inlets 21 and the cooling cell outlets 23 of the connected cooling cells 17 of the respective two connected cooling plates 2 are positioned to align. In the illustrated embodiment, the inlets 21 are positioned at an upper part and the outlets 23 at a bottom part of the cooling cell walls 17a, seen relative to the flow direction of cooling fluid flow.

Fig. 11 is a cross sectional view of a cassette 1 with a membrane 4 at both electrolyte plates 3a, 3c. The cooling flow path 5 is formed between the two cooling plates 2, and the anodic electrolyte path 6a and the cathodic electrolyte path 6c are formed between a cooling plate 2 and a respective electrolyte plate 3a, 3c.

The contact columns 19 are seen pointing towards the electrolyte plates 3a, 3c, contacting these. An electrical contact is created by the contact columns 19 to the electrolyte plates 3a, 3c, the cooling plates 2 themselves thus operating as electrical conductors.

The contact columns 19 may not be fixed to the electrolyte plates 3a, 3c, and in an embodiment contact may be ensured by the pressure of the electrolyte solution in the electrolyte paths 6a, 6c being higher than the pressure of the cooling fluid 2 in the cooling fluid path 5.

Figs. 12A and 12B show a geometric relationship between contact columns 19 of a cooling plate 2. The thickness (t) of the cooling plates 2 is preferably in the range between 0.5 mm and 0.7 mm. The contact columns 19 are placed at the corners of a rectangle. The horizontal distance between the contact column 19 positioned at the first corner of the rectangle and the contact column 19 positioned at the second corner of the rectangle is Z. X is half the length of the horizontal distance Z and is smaller than 160 (hundred sixty) times the thickness, t, of the cooling plates 2, and higher that 30 (thirty) times the thickness, t, of the cooling plates 2. The vertical distance between the contact column 19 positioned at the first corner of the rectangle and the contact column 19 positioned at the fourth corner of the rectangle is Y and is bigger that X in half and smaller than two times X. Fig. 12A shows an embodiment of the cooling plate 2 where the contact columns 19 are distributed at the corners of the rectangle and with one contact column 19 being placed at the intersection of the diagonals (D) of the rectangle.

Fig. 12B shows an embodiment of the cooling plate 2 where the contact columns 19 are distributed at the corners of the rectangle and with two contact columns 19 positioned at half the length of the horizontal distance Z, i.e. X.

References

1 - Cassette

2 - Cooling plate

3a - Anodic electrolyte plate

3c - Cathodic electrolyte plate

4 - Membrane

4a - Membrane hole

5 - Cooling path

6a - Anodic electrolyte path

6c - Cathodic electrolyte path

7in - Cooling fluid inlet

7out - Cooling fluid outlet

Sin - Anodic electrolyte fluid inlet

8out - Anodic electrolyte fluid gas outlet

9in - Cathodic electrolyte fluid inlet

9out - Cathodic electrolyte fluid gas outlet

10 - Clip-on gasket

11 - Electrolyte plate openings

Ila - Cut-out section

11b - Pushed down section

11c - Flanges lid, lie, Ilf - Electrolyte plate openings with curving shapes

12 - Recess

13 - First gasket part

13' - Projection

13a' - Grooves

14 - Second gasket part

14' - Projection

15 - Locking part

16 - Gasket hole 17 - Cooling cell

17a - Cooling cell wall

18 - Pattern

19 - Contact column

20 - Cooling cell supply channel

21 - Cooling cell inlet

22 - Cooling cell return channel

23 - Cooling cell outlet

24 - Gas barriers

25 - Dimples

26 - Inner gas barrier

26a - Lower inner gas barrier

27 - Drain in the inner gas barrier

28 - Outlet blockade

29 - Opening in the outlet blockade

30 - Outlet blockade drain

31 - Outer gaskets

32 - Bead of gas outlet gasket

33 - Gasket

33' - Gasket encircling the active area

50 - Welding/brazing

55 - Projections

56 - Openings

57 - Recess

60 - Plate edges

Claims

23 CLAIMS

1. An electrolyte plate (3a, 3c) for an electrolyzer cassette (1), the electrolyzer cassette (1) further comprising at least one cooling plate (2), where the electrolyte plate (3a, 3c) is formed with at least one opening (7in, 7out) for a cooling fluid to pass the electrolyte plate (3a, 3c), at least one electrolyte fluid inlet (8in, 9in) for an electrolytic fluid to pass the electrolyte plate (3a, 3c), and at least one gas outlet (8out, 9out) for a gas to pass the electrolyte plate (3a, 3c), and where a porous area is formed between the at least one electrolyte fluid inlet (8in, 9in) and the at least one gas outlet (8out, 9out), the porous area being formed with openings (11) adapted to pass gas across the electrolyte plate (3a, 3c) between a membrane (4) to be positioned at the one side of the electrolyte plate (3a, 3c), and an electrolyte fluid path (6a, 6c) positioned at the other side of the electrolyte plate (3a, 3c).

2. An electrolyte plate (3a, 3c) according to claim 1, wherein the electrolyte plate (3a, 3c) is porous at least in an area adapted to match with a membrane (4), allowing the diffusion of product gases and ions.

3. An electrolyte plate (3a, 3c) according to claim 1 or 2, wherein the openings (11) formed in the porous area are formed by a semi-cut allowing cut-out portions to form flaps (Ila) being bend outwards.

4. An electrolyte plate (3a, 3c) according to claim 3, wherein the opposite surface of the electrolyte plate (3a, 3c) to the one in the bending direction of the flaps (Ila) is essentially flat.

5. An electrolyte plate (3a, 3c) according to any of the preceding claims, wherein a recess (12) is formed around the openings (11) formed in the porous area.

6. An electrolyte plate (3a, 3c) according to claim 5, wherein the recess (12) extends in a length direction of the electrolyte plate (3a, 3c).

7. An electrolyte plate (3a, 3c) according to claim 5 or 6, wherein the recess (12) covers a plural of the openings (11) formed in the porous area.

8. An electrolyte plate (3a, 3c) according to any of claims 5-7, wherein the recess (12) is formed at a surface of the electrolyte plate (3a, 3c) adapted to face the membrane (4).

9. An electrolyte plate (3a, 3c) according to any of the preceding claims, wherein each of the openings (11) formed in the porous area are formed by two cuts, and where the section between the two cuts forms a pushed outwards section (11b), which contacts the rest of the electrolyte plate (3a, 3c) at two positions.

10. An electrolyte plate (3a, 3c) according to claim 9, wherein the pushed outwards section

(llb) is positioned such that at least one of the two openings defined by the two cuts and the pushed outwards section points in the direction of the respective electrolyte gas outlet (8out, 9out).

11. An electrolyte plate (3a, 3c) according to claim 9 or 10, wherein the opposite surface of the electrolyte plate (3a, 3c) to the one in the bending direction of the pushed outwards sections (11b) is essentially flat.

12. An electrolyte plate (3a, 3c) according to any of the preceding claims, wherein the openings (11) formed in the porous area are formed by pushed down flanges (11c).

13. An electrolyte plate (3a, 3c) according to claim 12, wherein the pushed down flanges

(llc) are positioned such that free ends of the flanges point in the direction of the respective electrolyte gas outlet (8out, 9out).

14. An electrolyte plate (3a, 3c) according to claim 12 or 13, wherein the opposite surface of the electrolyte plate (3a, 3c) to the one in the bending direction of the flanges (11c) is essentially flat.

15. An electrolyte plate (3a, 3c) according to any of the preceding claims, wherein the openings (11, lid, lie, Ilf) formed in the porous area are formed with a larger length than width.

16. An electrolyte plate (3a, 3c) according to claim 15, wherein at least some of the openings (lid) formed in the porous area extend in a direction parallel to a length direction L of the electrolyte plate (3a, 3c).

17. An electrolyte plate (3a, 3c) according to claim 15 or 16, wherein at least some of the openings (lie) formed in the porous area extend in a direction perpendicular to a length direction L of the electrolyte plate (3a, 3c).

18. An electrolyte plate (3a, 3c) according to any of claims 15-17, wherein at least some of the openings (Ilf) formed in the porous area are positioned with their length direction at an angle relative to a length direction L of the electrolyte plate (3a, 3c).

19. An electrolyte plate (3a, 3c) according to any of claims 15-18, wherein the openings (lid, lie, Ilf) formed in the porous area have curving shapes being 'meat bone'-shaped.

20. An electrolyte plate (3a, 3c) according to any of claims 15-19, wherein the openings (lid, lie, Ilf) formed in the porous area have concave sections as well as convex sections.

21. An electrolyte plate (3a, 3c) according to claim 20, wherein the two opposing ends the openings (lid, lie, I lf) formed in the porous area are concave seen from the inside of the respective opening (lid, lie, I lf), and formed with convex sections at the centre, seen from the inside of the respective opening (l id, lie, Ilf).

22. An electrolyte plate (3a, 3c) according to any of claims 15-21, wherein the openings (lid, lie, Ilf) formed in the porous area are symmetric with two halves mirroring each other.

23. An electrolyte plate (3a, 3c) according to any of claims 15-22, wherein the openings (lid, lie, Ilf) formed in the porous area have a width at a centre portion, which is smaller than an upper width or diameter of a contact column (19) formed in a neighbouring cooling plate (2) when the electrolyte plate (3a, 3c) and the cooling plate (2) are connected to each other in an electrolyzer cassette (1).