WO2014068168A1

WO2014068168A1 - Method and arrangement for feeding reactants into a fuel cell stack and an electrolyzer stack

Info

Publication number: WO2014068168A1
Application number: PCT/FI2012/051060
Authority: WO
Inventors: Markus RAUTANEN; Olli HIMANEN; Jari Kiviaho; Jari PENNANEN
Original assignee: Elcogen Oy
Priority date: 2012-10-31
Filing date: 2012-10-31
Publication date: 2014-05-08

Abstract

The object of the invention is a method and apparatus for solid oxide fuel cell or solid oxide electrolyzer stack, in which method and apparatus at least first, second and third flow field plates (1a, 1b, 1c) on a stack are arranged in such a manner that each first face (16, 18) is opposed by a second face (15, 17) of a super positioned flow field plate (1a, 1b, 1c). At least one gas of fuel side gas and oxygen rich side gas is fed through at least one opening of an opening for fuel side gas inlet (8, 12) and an opening for oxygen rich side gas. At least one opening of the fuel side gas inlet opening (8, 12) and the oxygen rich side gas opening (7, 11) is formed on at least one edge (19) of the flow field plates (1a, b, 1c) and superposed in relation to each other in order to form a duct, The sealing means (3 - 6) are arranged to block at least one opening in such a manner that at least one direction of the fuel gas flow directions (15, 18) and the oxygen rich gas flow directions (16, 17) is changed at least in one single repetitious structure compared to at least another single repetitious structure.

Description

METHOD AND ARRANGEMENT FOR FEEDING REACTANTS INTO A FUEL CELL STACK AND AN

ELECTROLYZER STACK

The present invention relates to arranging gas exchange in a Solid Oxide Fuel Cell (SOFC) stack and in a Solid Oxide Electrolyzer (SOE) stack. A fuel cell causes fuel gas on the anode electrode and gaseous oxidizer (oxygen) on the cathode electrode to react in order to produce electricity. Electrolyzer reactions are reverse to fuel cell, i.e. electricity is used to produce fuel. SOFC and SOE stacks comprise stacked cell elements and separators in a sandwiched manner wherein each cell element is constituted by sandwiching an electrolyte, a fuel electrode and an oxygen electrode. The reactants are guided by flow field plates to the porous electrodes.

Background of the invention

The present invention concerns fuel cell and electrolyzer stacks, in particular Solid Oxide Fuel Cell (SOFC) and Solid Oxide Electrolyzer (SOE) stacks where the flow direction of the cathode gas relative to the anode gas internally in each cell as well as the flow directions of the gases between adjacent cells, are combined through different cell layers of the stack. Further, the cathode gas or the anode gas or both can pass through more than one cell before it is exhausted and a plurality of gas streams can be split or merged after passing a primary cell and before passing a secondary cell. These combinations serve to increase the current density and minimize the thermal gradients across the cells and the whole stack.

In the following, the invention is explained in relation to SOFC. Accordingly, in the SOFC the cathode gas is an oxidation gas (including air and other oxygen rich gases) and the anode gas is a fuel gas. A SOFC comprises an oxygen-ion conducting electrolyte, a cathode electrode where oxygen is reduced and an anode electrode where fuel is oxidized. The overall reaction in an SOFC is that fuel and oxygen react chemically and electrochemically to produce electricity and heat. The operating temperature for a SOFC is in the range of 600 to 1000°C, preferably at the lower range. A SOFC delivers in normal operation a voltage of approximately 0.8V. To increase the total voltage output, the fuel cells are usually assembled in stacks in which the fuel cells are electrically connected via flow field plates (also:

interconnector plates, bipolar plates). The desired level of voltage determines the number of cells needed.

During operation, an oxidant such as air is supplied to the solid oxide fuel cell in the cathode region. Fuel, such as methane, is supplied in the anode region of the fuel cell where it is converted into hydrogen and carbon oxides by chemical and electrochemical reactions. Fuel passes through the porous anode and reacts at the anode/electrolyte interface with oxygen ions generated in the cathode side and conducted through the electrolyte. Oxygen ions are created in the cathode side as a result of the acceptance of electrons from the external circuit of the cell. Bipolar plates separate the anode and cathode sides of adjacent cell units and at the same time enable electron conduction between anode and cathode. Interconnects, or bipolar plates are normally provided with a plurality of channels for the passage of fuel gas on one side of an

interconnect plate and oxidant gas on the other side. The flow direction of the fuel gas is defined as the substantial direction from the fuel inlet portion to the fuel outlet portion of a cell unit. Likewise, the flow direction of the oxidant gas, the cathode gas, is defined as the substantial direction from the cathode inlet portion to the cathode outlet portion of a cell unit.

Conventionally, the cells are stacked one on top of each other with a complete overlap resulting in a stack with for instance co-flow having all fuel and oxidant inlets on one side of the stack and all fuel and oxidant outlets on the opposite side. One feature affecting the temperatures of the structure in operation is steam reformation of the fuel that is fed into the cell. Steam reformation is endothermic reaction and cools the fuel inlet edge of the cell.

Due to the exothermicity of the electrochemical process, the outlet gases leave at higher temperature than the inlet temperature. When endothermic and exothermic reactions are combined in an SOFC stack a significant temperature gradient across the stack is generated. Large thermal gradients induce thermal stresses in the stack which are highly undesirable and they entail difference in current density and electrical resistance. Therefore the problem of thermal management of an SOFC stack exists: to reduce thermal gradients enough to avoid unacceptable stresses and to maximize electric efficiency through homogenous current density profile.

US 6,830,844 describes a system for thermal management in a fuel cell assembly, particularly for preventing temperature gradients of above 200°C across the cathodes by periodically reversing the air flow direction across the cathode, thereby alternating the supply and exhaust edges of the cathodes.

US 6,803,136 describes a fuel cell stack with a partial overlap between the cells forming the stack and resulting in an overall spiral configuration of the cells. The cells are angularly offset to one another which provides ease of manifolding and thermal management.

JP 7082874 discloses a stack wherein gas flows are guided crosswise so that inlet channel of the gas is opposite to outlet channel in each cell. The flow is spread on electrolyte by several funnels and the flows of fuel gas and oxidizer are directed opposite to each other.

Other arrangements for guiding the gas flow in a fuel cell are described in WO

2011003519, EP 0369059, JP 11067258 and JP 63236264.

Despite the great number of various approaches to dealing with gas distribution in a fuel cell, improvements in the field are needed.

It is an object of the present invention to provide a fuel cell or electrolyzer stack, particularly a solid oxide fuel cell stack or solid oxide electrolyzer stack, with efficient thermal management across the stack, which is simpler than the presently proposed structures.

It is a further object of the present invention to provide a solid oxide fuel cell stack or solid oxide electrolyzer stack which has a flow channel structure that can be more easily manufactured.

Yet a further object of the invention is to provide a solid oxide fuel cell stack or solid oxide electrolyzer stack wherein the flow paths of the gases are obtained by blocking flow from selected main gas channels by sealing means.

Summary of the invention

According to the present invention, the fuel cell or electrolyzer stack comprises at least two single repetitious structures. A single repetitious structure comprises at least of one electrochemically active electrolyte element structure including fuel side, electrolyte in between, and oxygen rich side, placed between at least two flow field plates the other distributing oxygen rich gas in the oxygen rich side of the electrolyte element structure and the other distributing fuel gas in the fuel side of the electrolyte element, and at least one sealing means sealing the gas atmosphere at its intended enclosure. The flow field plate has at least one inlet openings for fuel gas and/or oxygen rich gas and at least one outlet openings for used fuel gas and/or oxygen rich gas. The flow direction of at least one gas of fuel gas and oxygen rich gas at least in one single repetitious structure is changed compared to at least another single repetitious structure by applying sealing means that enable the utilization of gas from an inlet opening and delivering the reaction product gas to an outlet opening that differs from the inlet opening and outlet opening of at least in another single repetitious structure.

The object of the invention is solid oxide fuel cell or solid oxide electrolyzer 5 stack, comprising at least first, second and third flow field plates, each having a first face and a second face and arranged on a stack in such a manner that each first face is opposed by a second face of a super positioned flow field plate, at least one electrolyte element structure placed between each opposing super positioned flow field plates, sealing means arranged on each of the faces i o of the flow field plates, and means for guiding fuel side gas and oxygen rich side gas to and from the electrolyte element structure, and each two opposing flow field plates and the electrolyte element structure therebetween form a single repetitious structure. The first and second faces of the at least three flow field plates have a surface comprising gas flow guiding means and electronic

15 paths for distributing gas flow over the at least two electrolyte elements and conducting electrons between the electrolyte elements placed therebetween. The means for feeding gas comprise at least one opening of an opening for fuel side gas inlet and an opening for oxygen rich side gas inlet, at least one opening of fuel side gas inlet opening and oxygen rich side gas inlet opening is

20 formed at least on one edge of the flow field plates and superposed in relation to each other in order to form at least one duct, and the sealing means are arranged to block at least an inflow opening in such a manner that at least one direction of the fuel side gas flow directions and the oxygen rich side gas flow directions is changed at least in one single repetitious structure compared to at

25 least another single repetitious structure.

The object of the invention is also a solid oxide fuel cell or solid oxide

electrolyzer stack method, in which method at least first, second and third flow field plates on a stack are arranged in such a manner that each first face is 30 opposed by a second face of a super positioned flow field plate, is placed at least one electrolyte element structure between each opposing super positioned flow field plates, is arranged at least one of sealing means at least on a face of the flow field plates, is guided fuel side gas and oxygen rich side gas to and from the electrolyte element structure, and a gas flow is guided and distributed over at least the two electrolyte elements and electrons are conducted between the electrolyte elements placed therebetween. In the method at least one gas of fuel side gas and oxygen rich side gas is fed through at least one opening of an opening for fuel side gas inlet and an opening for oxygen rich side gas, at least one opening of the fuel side gas inlet opening and the oxygen rich side gas opening is formed on at least one edge of the flow field plates and superposed in relation to each other in order to form a duct, and the sealing means are arranged to block at least one opening in such a manner that at least one direction of the fuel gas flow directions and the oxygen rich gas flow directions is changed at least in one single repetitious structure compared to at least another single repetitious structure.

According to one advantageous embodiment, the flow paths for at least one gas of fuel side gas and the oxygen rich side gas are obtained by blocking flow at least from one selected opening by sealing means. According to one embodiment of the invention, at least one outflow channel is indexed in relation to at least one inflow channel in view of at least one face of the flow field plate.

According to one embodiment of the invention, the flow field plates are made of at least one of sheet metal, ceramic material, cermet material, and some similar type of material.

According to one embodiment of the invention, the contour structure in flow field plates are made with at least one of net type structure, material insertion methods, plastic deformation, combining at least two formed sheet metal plates, extrusion, casting, printing, and similar method. According to one embodiment of the invention, the sealing means are made of at least one of glass, ceramic, glass-ceramic, silicate mineral, metal, and similar material.

Other objects and features of the invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.

Brief description of the drawing

Figure 1 is a schematic drawing of one embodiment of the invention.

Detailed description of the presently preferred embodiments

In the following, the invention is explained in relation to a solid oxide fuel cell stack. The solid oxide electrolyzer stack only differs from solid oxide fuel cell stack in that manner that electricity is used to produce fuel with reverse reactions to fuel cell reactions.

Figure 1 shows flow field plates la, lb, lc of a fuel cell. A complete fuel cell stack comprises several plates 1 placed on successively each other in a shown manner. The plates in this embodiment are rectangular and symmetrical. An electrolyte element structure 2 comprising an electrolyte layer between an anode electrode and a cathode electrode is placed between the plates 1 generally in the middle of the plate. The electrolyte element structure 2 may be any suitable electrolyte element structure and is not therefore described herein in any further detail. The flow field plates 1 and the electrolyte element structure 2 are sealed with sealing means 3 - 6. The purpose of the sealing means 3 - 6 is to ensure that oxidant and fuel are not directly mixed without the fuel cell reactions inside the electrochemically active area, that the fuel and oxidant are not leaked out from the electrochemical cells, that the adjacent electrochemical cells are not in electronic contact with each other, and that oxidant and fuel are supplied to the desired flow field plate planes 1. Two opposing flow field plates la, lb, lc and the electrolyte element structure 2 therebetween form a single repetitious structure. A flow field plate 1 is a planar thin plate that is made of metal alloy, ceramic material, cermet material or other material that can withstand chemical, thermal and mechanical stresses that are present in a fuel cell. According to the invention, the flow field plate 1 comprises inflow and outflow openings placed at the edges of the plate 1. In this example the plate 1 is rectangular and flow openings are placed on slightly shorter edges 19. Both of the edges 19 have four openings, one inflow opening 7, 11 for oxygen rich gas (in following exemplary embodiment: air), one outflow opening 10, 14 for air, one inflow opening 8, 12 for fuel, and one outflow opening 9, 13 for fuel. The oxygen rich gas can be any gas or gas mixture, which comprises a measurable amount of oxygen. On both of the edges 19 the openings are arranged in a sequence that has first air in 7, 11, then fuel in 8, 12, then fuel out 9, 13, and then air out 10, 14. The surfaces of the first face 20 (in the fig. top surface) and the second face 21 (below surface, not shown) around the edges of the flow field plate are shaped to allow efficient sealing and they limit a contoured surfaces 15 - 18 in the middle of the flow field plate that has a specific contour for guiding fuel gas and air over the surfaces of the electrolyte elements 1. It should be noted, that the reference numerals 15 - 18 that depict arrows related to sealing means 3 - 6 that illustrate gas flow routes in figure 1 are also used to refer to a face and a contoured surface 15 - 18 of a flow field plate la, lb, lc that is facing towards the sealing means 3 - 6 that faces the sealing element or structure in question. The contoured surfaces 15 - 18 comprise gas distribution media and electric contact paths that run from one side of the openings to the opposite side. The gas distribution media and electric contact paths are preferably straight and parallel to each other and arranged so that contact paths on one face 20, 21 of the flow field plate 1 is a gas distribution media on the opposite face of the plate 1 and vice versa. In a way, the surfaces of the faces are mirror images. The contour of the plate can thus be similar to a corrugated board. Such a plate can be easily manufactured by pressing or stamping or by any manufacturing method utilizing plastic deformation or by molding, extrusion, tape casting or similar in the case of brittle materials such as ceramic or cermet materials. The openings 7 - 14 for fuel and air can be made simultaneously in a same die. Thus the making of the plate requires basically only one process step.

The gas distribution media and electric contact paths may have other curvature than straight if it is needed for guiding the gas flows. Theoretically, any smooth or angled curve can be utilized as long as the gas distribution path formed on the surface form a continuous flow path from the inflow channels of the flow field plate la, lb, lc to the outflow channels. As the flow field plate 1 may have any geometrical shape that is desired, the inflow and outflow openings may be positioned at any desired places near edges of the flow field plate. The number of the openings for arranging the gas flows on a fuel cell stack may vary as well as the way how the gas flows are arranged. The basic idea is that openings 7 - 14 on superposed flow field plates 1 are arranged so that their positions are matched and the openings in same line form a gas manifold channel through the stack. Sealing means 3 - 6 are used in order to prevent feeding of the fuel and air to wrong layers between electrolyte elements and the flow field plates. The sealing mean is arranged to surround each opening 7

- 14 on the flow field plate 1. The flow field plate 1 and the sealing elements 3

- 6 are used to form ducts that go through whole fuel cell stack. The openings in the flow field plates are super positioned in order to form such a duct.

When fuel or air is to be guided from said duct between the flow field plate and the electrolyte element, an opening is formed in the sealing element 3 - 6 so that a passage of gas is allowed only to a restricted flow media, either 15, 16, 17 or 18 of the flow field plate 1. Any suitable sealing means, material and structures used in the art may be utilized for providing the required sealing and forming the gas channels. The sealing means may be separate elements or made by joining the plates in a sealing manner.

One possible arrangement for arranging the gas flows is described in the following. In here definitions top and bottom as well as up and down are used in conjunction of the fig. 1 only, and have no other structural meaning. First, air is fed over a flow field plate that is first in the stack. This plate lc is shown in the bottom of the exploded view in fig. 1. Now, an air path is arranged to start from air inflow channel 7 and the exit is arranged at the outflow channel 14. The air flows along the flow media 18 and is divided over the bottom surface of the electrolyte element structure 2. The electronic paths are set against electrolyte element structure and provide for guiding the gas over said surface as well as heat and electron transfer over a significantly large area. The flow medium is preferably straight channel structure but any other form may be used, for example such as sine, parabolic or zigzag curve or net type structures. On the opposite side of the electrolyte element structure 2 is the second flow field plate lb. Now, fuel is guided over the electrolyte element. This is accomplished by arranging a flow path from fuel inflow channel 8 over the underside of the second flow field plate and over the electrolyte element structure in flow media 17. Fuel is exhausted through the outflow opening 13. In this embodiment air and fuel gases have same flow directions. On following layer gas flows are arranged as follows: air from opening 11 to opening 10 through gas distribution media 16, fuel from opening 12 to opening 9 through gas distribution media 15. The flow arrangement with varying inflow and exhaust locations can be continued with as many layers as required for the application. The purpose of varying the inflow and exhaust locations is to provide means for arranging the gas flows so that the temperatures over the fuel cell and fuel cell stack can be kept as constant as possible and the temperature gradients small. As the flow arrangements cannot be changed after the fuel cell is assembled and in operation, the design of the flow characteristics is done by using calculations and simulation models. Further, it must be noted that each gas flow flows into a space between two flow field plates la - lc through inflow channel and exits therefrom via exit channel. Each inflow channel feeds fresh gas to the electrolyte element structure 2 and each outflow channel leads the exhaust gas directly out from the stack. Thus, gas flows are not redirected to further electrolyte elements. It must further be noticed that the inflow and outflow openings do not have to be formed on to the flow field plate but they can be arranged in separate means, such as closed gas compartments.

The number of the opening used for gas feed may vary according to the design of the fuel cell. Minimum number might be one inflow opening for a gas as well as an outflow opening. Using more openings allows for more flow patterns but naturally complicates the design. According to one embodiment, the fuel gas and air flow may be arranged crosswise to each other. This can be done simply by rotating every other flow field plate 90°. The rectangular form described above can be used to simplify manufacturing and assembling processes.

However, any geometric form desired may be used such as polygonal, circular, oval, etc.

The preferred manufacturing methods for forming the contoured (as example: corrugated) surface are methods using plastic deformation such as stamping, pressing and like, wherein the shape of the material is changed but no material is added or removed, or methods wherein material is added such as welding or removed such as etching. Other manufacturing methods can be utilized if the flow field material is brittle such as extrusion, casting, printing, molding, and like. The openings for fuel and air can be usually made in a same

manufacturing step. Each flow field plate 1 can be made similar in the stack assembly structure, thus only one type of plate is needed to produce a fuel cell stack having desired amount of repetitious electrolyte element structures 2. This simplifies the structure and eases manufacturing of the fuel cells.

Feeding in air and fuel into a SOFC causes normally an uneven temperature distribution since the inlet air and fuel cool the electrolyte elements from the inlet side. On the other hand, exothermic fuel cell reactions heats up the gases on their way to the exhaust side of the electrolyte elements. The thermal distribution causes thermomechanical stresses to the SOFC structure which may cause breakage of the electrolyte element. The performance of a SOFC improves as the temperature is increased but the increased temperature speeds up aging of the cell. In order to maximize the performance and lifetime of the cell, it is essential to be able to use the cell as accurately as possible on optimum temperature over the whole cell structure. The flow arrangement structure provided by the invention diminishes the temperature differences of the cell and thus improves reliability, performance and lifetime. The invention is also economically usable in stack manufacturing. As the structure is simple, benefits can be obtained in design and production.

Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the invention may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements which perform substantially the same results are within the scope of the invention. Substitutions of the elements from one described embodiment to another are also fully intended and contemplated. It is also to be understood that the drawings are not necessarily drawn to scale but they are merely conceptual in nature. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

Claims:

1. Solid oxide fuel cell or solid oxide electrolyzer stack, comprising - at least first, second and third flow field plates (la, lb, lc), each having a first face (16, 18) and a second face (15, 17) and arranged on a stack in such a manner that each first face (16, 18) is opposed by a second face (15, 17) of a super positioned flow field plate (la, lb, lc), - at least one electrolyte element structure (2) placed between each opposing super positioned flow field plates (la, lb, lc),

- sealing means (3 - 6) arranged on each of the faces (15, 16, 17, 18) of the flow field plates (la, lb, lc), and

- means (7 - 14) for guiding fuel side gas and oxygen rich side gas to and from the electrolyte element structure (2), and each two opposing flow field plates (la, lb, lc) and the electrolyte element structure (2) therebetween form a single repetitious structure, characterized in that

- the first (16, 18) and second (15, 17) faces of the at least three flow field plates (la, lb, lc) have a surface comprising gas flow guiding means and electronic paths for distributing gas flow over the at least two electrolyte elements (2) and conducting electrons between the electrolyte elements (2) placed therebetween, - the means (7 - 14) for feeding gas comprise at least one opening of an opening for fuel side gas inlet (8, 12) and an opening for oxygen rich side gas inlet (7, 11),

- at least one opening of fuel side gas inlet opening (8, 12) and oxygen rich side gas inlet opening (7, 11) is formed at least on one edge (19) of the flow field plates (la, lb, lc) and superposed in relation to each other in order to form at least one duct,

- and the sealing means (3 - 6) are arranged to block at least an inflow opening in such a manner that at least one direction of the fuel side gas flow directions (15, 18) and the oxygen rich side gas flow directions (16, 17) is changed at least in one single repetitious structure compared to at least another single repetitious structure.

2. Solid oxide fuel cell or solid oxide electrolyzer stack according to claim 1, characterized in that the flow path for at least one gas of the fuel side gas and the oxygen rich side gas are obtained by blocking flow at least from one selected opening (7 - 14) by sealing means (3 - 6).

3. Solid oxide fuel cell or solid oxide electrolyzer stack according to claim 1, characterized in that at least one outflow opening is indexed in relation to at least one inflow opening of the same gas in view of at least one face of the flow field plate.

4. Solid oxide fuel cell or solid oxide electrolyzer stack according to claim 1, characterized in that the flow field plates are made of at least one of sheet metal, ceramic material, cermet material, and some similar type of material.

5. Solid oxide fuel cell or solid oxide electrolyzer stack according to claim 1, characterized in that the contour structure in flow field plates (1) are made with

at least one of net type structure, material insertion methods, plastic deformation, combining at least two formed sheet metal plates, extrusion, casting, printing, and similar method.

6. Solid oxide fuel cell or solid oxide electrolyzer stack according to claim 1, characterized in that the sealing means (3 - 6) are made of at least one of glass, ceramic, glass-ceramic, silicate mineral, metal, and similar material.

7. Solid oxide fuel cell or solid oxide electrolyzer stack method, in which method at least first, second and third flow field plates (la, lb, lc) on a stack are arranged in such a manner that each first face (16, 18) is opposed by a second face (15, 17) of a super positioned flow field plate (la, lb, lc),

- is placed at least one electrolyte element structure (2) between each opposing super positioned flow field plates (la, lb, lc),

- is arranged at least one of sealing means (3 - 6) at least on a face (15, 16, 17, 18) of the flow field plates (la, lb, lc),

- is guided fuel side gas and oxygen rich side gas to and from the electrolyte element structure (2), and

- a gas flow is guided and distributed over at least the two electrolyte elements (2) and electrons are conducted between the electrolyte elements (2) placed therebetween, characterized in that in the method:

- at least one gas of fuel side gas and oxygen rich side gas is fed through at least one opening of an opening for fuel side gas inlet (8, 12) and an opening for oxygen rich side gas, - at least one opening of the fuel side gas inlet opening (8, 12) and the oxygen rich side gas opening (7, 11) is formed on at least one edge (19) of the flow field plates (la, lb, lc) and superposed in relation to each other in order to form a duct,

5

- and the sealing means (3 - 6) are arranged to block at least one opening in such a manner that at least one direction of the fuel gas flow directions (15, 18) and the oxygen rich gas flow directions (16, 17) is changed at least in one single repetitious structure compared to at least another single repetitious

0 structure.

8. Solid oxide fuel cell or solid oxide electrolyzer stack method according to claim 7, characterized in that at least one flow of the fuel side gas flow and the oxygen rich side gas flow is obtained by blocking flow from at least one5 selected opening (7 - 14) by sealing means.

9. Solid oxide fuel cell or solid oxide electrolyzer stack method according to claim 7, characterized in that at least one outflow opening is indexed in relation to at least one inflow opening of the same gas in view of at least one o face of the flow field plate.

10. Solid oxide fuel cell or solid oxide electrolyzer stack method according to claim 7, characterized in that the flow field plates are made of at least one of sheet metal, ceramic material, cermet material, and some similar type of

5 material.

11. Solid oxide fuel cell or solid oxide electrolyzer stack method according to claim 7, characterized in that the contour structure in flow field plates (1) are made with at least one of net type structure, material insertion methods, plastic0 deformation, combining at least two formed sheet metal plates, extrusion, casting, printing, and similar method.

12. Solid oxide fuel cell or solid oxide electrolyzer stack method according to claim 7, characterized in that the sealing means (3 - 6) are made of at least one of glass, ceramic, glass-ceramic, silicate mineral, metal, and similar material.