Modular arrangement of solid oxide cell stacks

Abstract

The object of the present invention is a modular arrangement arranged in a 2×N matrix, where N is any natural number. This arrangement includes a fuel inlet manifold (150) and a fuel outlet manifold (152) between two adjacent stacks (103). The fuel inlet manifold (150) and the fuel outlet manifold (152) form a fuel manifold (171) for supplying a fuel gas supply (108) to the stack and for supplying a fuel exhaust gas (177) from the stack, and the stacks are arranged in parallel connection at the manifold in terms of fuel gas supply and fuel exhaust gas connections. The stacks (103) are arranged with a common oxygen-side gas supply section (106) connected to the inlet side of the open structure for oxygen-side gas supply (105) and a common oxygen-side gas exhaust section (176) connected to the outlet side of the open structure for oxygen-side gas supply (105). The inlet manifold (150) includes gas flow holes of controllable size for the stack (103) to create uniform gas flow into the stack, and the outlet manifold (152) includes gas flow holes of controllable size for the stack (103) to create uniform gas flow from the stack. The modular arrangement includes a first gas seal (155), a first electrical insulating plate (119), and a second gas seal (156) between the manifold (171) and the stack (103). The modular arrangement includes a second electrical insulating plate (114) and compression structures (116) for the stack (103) on the upper and lower sides (122) and (124) of the cell stack (103), and an air-side seal structure (169) between the stacks, and each stack end plate (170) is connected to an electrical connection (173).

Description

[Technical Field]

[0001] The majority of the world's energy is produced by oil, coal, natural gas, or nuclear power. All of these production methods have their own problems, for example, regarding availability and environmental considerations. Regarding the environment, oil and coal in particular cause pollution when burned. A problem with nuclear power, at least, is the storage of spent fuel.

[0002] Particularly due to environmental concerns, new energy sources have been developed that are more environmentally friendly and have, for example, better efficiency than the energy sources mentioned above. Fuel cells convert the energy of fuels, for example biogas, directly into electricity through a chemical reaction in an environmentally friendly process, and electrolyzers, which convert electricity into fuel, are promising future energy solution devices.

[0003] Renewable energy production methods such as solar and wind power face seasonal production fluctuations due to environmental limitations. In the case of overproduction, hydrogen production by water electrolysis has been suggested as a future energy storage option. Furthermore, electrolysis cells can also be used to produce high-quality methane gas from renewable biogas reserves.

[0004] This invention relates to a modular arrangement of solid oxide fuel cell (SOFC) stacks or solid oxide electrolysis cell (SOEC) stacks. Fuel cells generate electricity by reacting an input reactant fuel gas on an anode electrode with a gaseous oxidant (oxygen) on a cathode electrode. Electrolyzers have the opposite reaction to fuel cells, using electricity to produce fuel and oxygen. SOFC and SOEC stacks include a sandwich of cell elements and separators, each sandwiching an electrolyte, an anode side, and a cathode side. Reactants are guided to the porous electrodes by flow-through plates. [Background technology]

[0005] As shown in FIG. 1, a fuel cell comprises an anode side 100, a cathode side 102, and an electrolyte material 104 therebetween. This structure is referred to herein as a unit cell 174 (FIGS. 1 and 2). In a solid oxide fuel cell (SOFC), oxygen 106 is supplied to the cathode side 102 and is reduced to negative oxygen ions by receiving electrons from the cathode. The input stream 106 is depleted of oxygen at the outlet side 176. The negative oxygen ions travel through the electrolyte material 104 to the anode side 100, where they react with fuel 108 to produce electrons, water, and typically carbon monoxide (CO) and carbon dioxide (CO), i.e., fuel exhaust 177. The anode 100 and cathode 102 are connected via an external electrical circuit 111, which includes a fuel cell load 110 that extracts electrical energy along with heat from the system. The fuel cell reactions for methane, carbon monoxide, and hydrogen fuels are shown below: Anode: CH4 + H2O = CO + 3H2 CO+H2O=CO2+H2 H2+O 2- =H2O+2e - Cathode: O2+4e - =2O 2- Net reaction: CH4 + 2O2 = CO2 + 2H2O CO+1 / 2O2=CO2 H2+1 / 2O2=H2O

[0006] In the electrolysis mode of operation (solid oxide electrolysis cell (SOEC)), the reactions are reversed: heat and electrical energy from a source 110 are supplied to the cell, where water, and often also carbon dioxide, are reduced on the cathode side 100 to form oxygen ions, which migrate through the electrolyte 104 material to the anode side 102, where the oxidation reaction occurs. It is possible to use the same solid electrolyte cell in both SOFC and SOEC modes. In such cases, in the context of this specification, the electrodes are typically referred to as the anode and cathode based on the fuel cell's mode of operation, although in purely SOEC applications, the oxygen electrode may be referred to as the anode and the reactant electrode as the cathode.

[0007] Solid oxide electrolysis cells operate at temperatures that allow high-temperature electrolysis reactions to occur, typically between 500 and 1000°C, although temperatures outside this range may be useful. These operating temperatures are similar to those of SOFCs. The net cell reaction produces hydrogen and oxygen gases. The reaction for one mole of water is shown below, with water reduction occurring at the anode: Cathode: H2O+2e - →2 H2+O 2- Anode: O 2- →1 / 2O2+2e - Net reaction: H2O → H2 + 1 / 2O2.

[0008] In solid oxide fuel cell (SOFC) stacks and solid oxide electrolyzer (SOE) stacks, generally referred to herein as solid oxide cell stacks, the flow direction of cathode gas relative to anode gas within each cell, as well as the flow direction between adjacent cells, are combined through different cell layers of the stack. Additionally, cathode gas and / or anode gas can pass through two or more cells before being exhausted, and multiple gas streams can be split or combined between passing through a primary cell and a secondary cell. These combinations serve to increase current density and minimize thermal gradients across the cells and stack.

[0009] In normal operation, SOFCs provide a voltage of approximately 0.8 V, and SOECs provide 1.3 V. To increase the total voltage output, cells 174 are typically assembled into stacks where the cells are electrically connected via flow plates (also separator plates, interconnect plates, bipolar plates). The desired voltage level determines the number of cells required.

[0010] The bipolar plates separate the anode and cathode sides of adjacent cell units while allowing electron conduction between the anode and cathode. The interconnect or bipolar plates typically have multiple channels for passing fuel gas through one side of the interconnect plate and oxygen-rich gas through the other side. The fuel gas flow direction is defined as the substantial direction from the fuel inlet to the fuel outlet of the cell unit. Similarly, the oxygen-rich gas flow direction is defined as the substantial direction from the inlet to the outlet of the cell unit.

[0011] Conventionally, cells are stacked on top of each other with complete overlap, resulting in a stack with parallel flow, for example, with all fuel and oxidant inlets on one side of the stack and all fuel and oxidant outlets on the other side. One feature that affects the temperature of the structure during operation is steam reforming of the fuel supplied to the cells. Steam reforming is an endothermic reaction, cooling the fuel inlet edge of the cell.

[0012] Due to the heat generated by the electrochemical process, the outlet gas exits at a higher temperature than the inlet temperature. The combination of endothermic and exothermic reactions within a SOFC stack creates significant temperature gradients across the stack. Large thermal gradients induce highly undesirable thermal stresses within the stack, accompanied by differences in current density and electrical resistance. Therefore, the thermal management of SOFC stacks presents a challenge: sufficiently reducing the thermal gradients to avoid unacceptable stresses while simultaneously maximizing electrical efficiency through a uniform current density profile.

[0013] Prior art fuel cell stacks or electrolyzer cell stacks have tolerance variations in the thickness of the unit cell structures between cell structures within the stack. For example, in cell stack structures where ceramic materials are used, prior art embodiments allow thickness variations in the range of only a few micrometers. This causes differences in flow conditions between cells, which in turn causes variations in cell voltage profiles within the stack structure, resulting in thermal gradients between cells and reducing the power density of the stack. This in turn reduces the stack duty cycle and shortens the stack lifespan, the former increasing the capital cost of the stack per unit of power output produced, and the latter increasing the operational cost of the stack structure due to, for example, reduced stack replacement time in fuel cell systems and increased electricity costs in electrolysis stacks.

[0014] High-temperature solid oxide cell stacks are a preferred conversion technology due to their extremely high efficiency in both fuel cell and electrolysis modes. An inherent challenge associated with these technologies, partially due to the high temperatures, is material corrosion, which causes an increase in internal resistance to the structure and reduces the power output and hydrogen production capabilities of the fuel cell and electrolyzer, respectively. Corrosion issues can exist in multiple locations within the stack structure, but are typically prominent in areas involving various material systems. These material systems are typically the three-phase region between the metallic interconnect structures, the seal structures, and the oxidizing gas. In these material systems, for example, the metallic interconnect materials, typically made of ferritic stainless steel grades due to their excellent corrosion resistance and thermal expansion characteristics matching those of the other stack materials, can react with the seal structures, which are typically made at least in part of glass materials, by, for example, changing the crystal structure of the metal or by changing the protective oxide structure on the metal surface, ultimately causing through-plane oxidation of the steel material and creating a direct path for fuel and oxygen to mix, potentially leading to catastrophic failure of the structure. Summary of the Invention

[0015] The object of the present invention is to improve the reliability and structure of fuel cell or electrolyzer cell stacks by a modular arrangement of solid oxide cell stacks in a fuel cell system or electrolyzer cell system, wherein each stack includes unit cells including a fuel side, an oxygen-rich side, and an electrolyte material between the fuel side and the oxygen-rich side, each stack includes flow path plates made of a material having high electrical conductivity at high temperatures, each stack has a four-angled configuration, each stack includes a gas seal structure made of an electrically insulating material, the arrangement has gas distribution structures for both the inlet and outlet sides of the fuel gas, the oxygen-side gas supply is based on an open channel structure, the arrangement includes end plates used for current collection, and the cells, flow path plates, and gas seal structures are arranged in a pile to form a stack between the end plates. The module arrangement is arranged in a 2×N matrix, where N is any natural number, and the arrangement includes a fuel inlet manifold and a fuel outlet manifold between two adjacent stacks, the fuel inlet manifold and the fuel outlet manifold form a fuel manifold for supplying a supply fuel gas to the stack and for supplying a fuel exhaust gas from the stack, the stacks are arranged in parallel connection in the manifold in terms of fuel gas supply and fuel exhaust gas connection, and the stacks are connected together with a common oxygen side gas supply compartment connected to an inlet side of the open structure for oxygen side gas supply and a common oxygen side gas exhaust compartment connected to an outlet side of the open structure for oxygen side gas supply. the inlet manifold includes gas flow holes of controllable size relative to the stack to form uniform gas flow into the stack, the outlet manifold includes gas flow holes of controllable size relative to the stack to form uniform gas flow from the stack, the modular arrangement includes a first gas seal, a first electrical insulating plate, and a second gas seal between the manifold and the cell stack, the modular arrangement includes a second electrical insulating plate and compression structures for the stack above and below the cell stack, and an air-side seal structure between the stacks, and each stack end plate is connected to an electrical connection.

[0016] The present invention is based on a modular arrangement of solid oxide cell stacks in a fuel cell system or electrolyzer cell system, the modular arrangement including stacks arranged in a 2×N matrix, where N is any natural number, with inlet fuel gas supplied to the stacks and exhaust gas supplied from the stacks over a fuel manifold between two adjacent stacks. The stacks are arranged in parallel connection at the manifold in terms of fuel gas supply and exhaust gas connections. The invention is further based on the stacks being arranged with a common oxygen-side gas compartment and a common oxygen-side gas exhaust compartment, and the manifold including gas flow holes of controllable size for the stacks to form uniform gas flow to and from the stacks based on the pressure difference between the inlet and outlet pipe connections of the manifold. An advantage of the present invention is a practical cell stack modular arrangement that can be sized according to the selected fuel cell or electrolysis cell application, thus saving time, economic costs, and assembly space. [Brief explanation of the drawings]

[0017] [Figure 1] A single fuel cell structure is shown. [Figure 2] 1 shows a repetitive solid oxide cell structure. [Figure 3] 1 shows a first exemplary cell stack module arrangement according to the present invention from the front side. [Figure 4] 10 illustrates a second exemplary cell stack module arrangement according to the present invention from the back side. [Figure 5] 10 illustrates a second exemplary cell stack module arrangement according to the present invention from the front side. [Figure 6] 1 illustrates an exemplary manifold configuration. [Figure 7] 1 shows the compression structure inside the air-side seal structure. [Figure 8] 1 shows the compression structure outside the air-side seal structure. DETAILED DESCRIPTION OF THE INVENTION

[0018] According to the present invention, a fuel cell or electrolysis stack includes at least two single repeat structures. The single repeat structure includes at least one electrochemically active unit cell structure including a fuel side, an electrolyte therebetween, and an oxygen-rich side, the at least one electrochemically active unit cell structure being disposed between at least two flow plates, one distributing oxygen-rich gas to the oxygen-rich side of the unit cell structure and the other distributing fuel gas to the fuel side of the unit cell structure, and at least one sealing means for sealing the gas atmosphere in its intended enclosure. The flow plates have at least one inlet opening for the fuel gas and / or oxygen-rich gas and at least one outlet opening for the spent fuel gas and / or oxygen-rich gas. The flow directions of the fuel gas and oxygen-rich gas can be arranged in a co-flow arrangement, in which both gases flow in essentially the same direction on each side of the unit cell, or in a counter-flow arrangement, in which the flow directions between the fuel gas and the oxygen-rich gas are essentially opposite, or in a cross-flow arrangement, in which the flow directions between the fuel gas and the oxygen-rich gas are at an essentially 90-degree angle, or any combination thereof.

[0019] FIG. 2 shows the flow plates 121 of a fuel cell stack. A complete fuel cell stack includes several plates 121 arranged one on top of the other in the illustrated manner. The plates in this embodiment are rectangular and symmetrical. Between the plates 121, generally in the center of the plates, is a unit cell structure 174 containing an electrolyte layer 104 between an anode electrode and a cathode electrode. The electrolyte element structure 174 may be any suitable electrolyte element structure and will therefore not be described in further detail herein. The flow plates 121 and unit cell structure 174 are sealed with a gas seal structure 128, which is preferably made of a compressible material, such as a ceramic, mineral, or glass material. The gas seal structure 128 according to the present invention is compressed when the cells are assembled into a stack. Two opposing flow plates 121, with the unit cell structure 174 and gas seal structure 128 therebetween, form a single repeating structure.

[0020] The fuel cell stack arrangement of FIG. 2 includes flow-restricting orifices 135, 136 that open to the flow distribution region and the fluid outlet region. The gas seal structure 128 compresses over the flow-restricting orifices 135, 136. The flow-restricting orifices 135, 136 ensure uniform fuel flow distribution across the active area of ​​the fuel cell electrodes by creating an additional pressure sink in the flow path. The gas seal structure 128 also creates similar pressure drop conditions between the fuel cell repeats, ensuring uniform flow distribution characteristics for each fuel cell repeat. The uniform flow distribution within the fuel cell stack also ensures uniform heat distribution conditions for the fuel cell stack, i.e., similar thermal gradients between cells within the stack. This improves the duty cycle of the fuel cell stack and extends the life of the fuel cell stack.

[0021] The purpose of the gas seal structure 128 is to further ensure that oxidant and fuel do not mix directly without a fuel cell reaction within the electrochemically active area, that fuel and oxidant do not leak from the electrochemical cells, that adjacent electrochemical cells do not electronically contact each other, and that oxidant and fuel are delivered to the desired flow plate 121. The flow plate 121 is a flat, thin plate made of a metal alloy, ceramic material, cermet material, or other material that can withstand the chemical, thermal, and mechanical stresses present in a fuel cell. The oxygen-rich gas can be any gas or gas mixture that contains a measurable amount of oxygen.

[0022] Preferred manufacturing methods for creating the contoured surface of the flow field plate 121 are those that use plastic deformation, such as stamping, molding, or pressing, where the shape of the material changes but no material is added or removed, or where material is added, such as by welding, sintering, and laser sintering, or removed, such as by etching and machining. If the flow field material is brittle, other manufacturing methods can be used, such as extrusion, casting, printing, or molding. Gas orifices can typically be made in the same manufacturing process.

[0023] Each flow plate 121 can be identically manufactured in a stack assembly, so that a desired number of plates of the same type are required to manufacture a fuel cell stack having a desired number of repeating unit cell structures 174. This simplifies the construction and facilitates the manufacture of the fuel cell.

[0024] Solid oxide electrolysis stacks differ from solid oxide fuel cell stacks only in that electricity is used to produce fuel in a reaction that is the reverse of the fuel cell reaction as described in the prior art.

[0025] The single largest energy consumer in a fuel cell system is the blower or compressor used to supply air to the cathode compartment of the fuel cell stack. The power consumption of the air supply device is proportional to the pressure level to which the air must be compressed. Also, in solid oxide electrolysis systems, air is typically supplied to the anode to control the heat balance of the electrolysis stack and maintain a predetermined oxygen partial pressure in the anode compartment. One of the major sources of pressure loss in fuel cells and electrolysis systems is the stack itself. It is advantageous to design the device so that the air side of the device has an open channel to the surrounding atmosphere.

[0026] 3-5 show first and second exemplary cell stack modular arrangements according to the present invention in a fuel cell system or electrolyzer cell system. In the modular arrangement of solid oxide cell stacks, each stack includes a unit cell 174 having a fuel side 100, an oxygen-rich side 102, and an electrolyte element 104 between the fuel side and the oxygen-rich side. Each stack 103 includes flow plates 121 made of a material that has high electrical conductivity at high temperatures. Preferably, high electrical conductivity means an area specific resistance of 0.1 ohm cm. 2 Less than, preferably 0.01 ohm cm 2The temperature is less than 400°C. High temperature means a temperature value above 400°C. Each stack has four angled structures and a gas seal gasket 128 made of an electrically insulating material. This arrangement has a gas distribution structure 127 for both the inlet and outlet sides of the fuel gas. The oxygen side gas supply is based on an open channel structure. This arrangement includes end plates 170 used for current collection, and the cells 174, flow path plates 121, and gas seal structure 128 are stacked to form a stack 103 between the end plates 170.

[0027] An exemplary module arrangement according to the present invention includes stacks 103 arranged in a 2×N matrix, where N is any natural number. The arrangement includes a fuel inlet manifold 150 and a fuel outlet manifold 152 between two adjacent stacks 103, which form a fuel manifold 171 for supplying fuel gas 108 to the stack and fuel exhaust gas 177 from the stack. The stacks are arranged in parallel connection at the manifold in terms of fuel gas supply and fuel exhaust gas connections.

[0028] In a further embodiment, the module arrangement includes at least two pairs of cell stacks 103 electrically arranged in series connection. In a further embodiment, the module arrangement includes X cell stacks 103 arranged in series connection, where X is a natural number and satisfies 2N / X=Y, where N and Y are natural numbers. The stacks 103 are arranged with a common oxygen side gas supply compartment 106 connected to the inlet side of the open structure 105 for oxygen side gas supply, a common oxygen side gas exhaust compartment 176 connected to the outlet side of the open structure 105 for oxygen side gas supply, and the common oxygen side gas exhaust compartment 176. As shown in FIGS. 4 and 5 , a manifold 171 can have an inlet pipe connection 160 at a first end of the manifold and an outlet pipe connection 162 at the first end of the manifold. In another embodiment, the manifold 171 can have an inlet pipe connection 160 at a first end of the manifold and an outlet pipe connection 162 at a second end of the manifold, and other types of arrangements are also possible. Manifold 171 includes gas flow holes of controllable size to stack 103 to create uniform gas flow to and from the stack based on the pressure difference between inlet pipe connection 160 and outlet pipe connection 162 of manifold 171. In one preferred embodiment, the module arrangement includes means for controlling the size of individual gas flow holes 133, 137 (FIG. 6) to create uniform gas flow to and from stack 103. Pressure drops may require different hole sizes between holes 133, 137.

[0029] 7, the module arrangement further includes a first gas seal 155, a first electrical insulating plate 119, and a second gas seal 156 between the manifold 171 and the cell stack 103. The module arrangement includes a second electrical insulating plate 114 and a compression structure 116 for the stack 103 on the upper and lower sides 122 and 124 of the cell stack 103, and an airtight structure 169 between the stacks. Each stack end plate 170 is connected to an electrical connection 173. The module arrangement can include an airtight structure 200 in which the fuel manifold structure 171, the stack 103, the seal structures 155, 156, and the electrical insulating plates 119, 114 are located. The air-side seal structure 169 is sealed to the airtight structure 200.

[0030] In an embodiment according to the invention, the modular arrangement can include a compression structure 116 inside the airtight structure 169 (FIG. 7). In another embodiment according to the invention, the modular arrangement can include a compression structure 116 outside the airtight structure 169 (FIG. 8).

[0031] In a preferred embodiment, the module arrangement may include centering structures on the upper side 122 and lower side 124. The centering structures may include threaded holes and seals. In one preferred embodiment, the module arrangement may include a compensation plate on the upper side 122 of the cell stack 103 to compensate for height tolerances between the stacks 103. The module arrangement preferably includes gas flow structures within the manifold 171 to create a pressure condition in which the pressure loss across the inlet manifold 150 and outlet manifold 152 is less than the pressure loss across a single cell 174. The exemplary manifold 171 shown in FIG. 6 includes connections to the inlet pipe 160 and outlet pipe 162, gas flow holes 133 to the stack, and gas flow holes 137 from the stack. In a preferred embodiment, the fuel inlet manifold 150 and fuel outlet manifold 152 may be connected to each other by welding to increase the rigidity and strength of the structure.

[0032] The manifold 171 and the cover portion of the stack 103 are preferably made of materials with similar thermal expansion coefficients. The air-side seal structure 169 preferably includes a hard ceramic in the center portion and a soft ceramic in the edge portion. The manifold 171 is preferably made of ferritic steel. The first electrical insulating plate 119 is preferably made of at least one high-density material. The second electrical insulating plate 114 is preferably made of at least one porous material. The high-density or porous material is preferably a ceramic material and / or a mineral. The gas seal structure 128, the first gas seal 155, and the second gas seal 156 are preferably manufactured by screen printing technology and are at least partially made of glass, glass-ceramic, or brazing alloy materials. The module arrangement preferably includes ceramic and / or glass paste for bonding the cells and the gas seals 155 and 156.

[0033] In one embodiment (e.g., FIG. 2), the height of the flow orifice can be determined by the distance from the bottom of the flow distribution region and / or the bottom of the fluid outlet region to the bottom of the gasket structure to stabilize the flow distribution in the repeating structure of the stack where the electrolyte element structure has thickness tolerance variations. Similar pressure drop conditions between cells are achieved by utilizing a gasket structure that can be compressed and pre-compressed from at least the flow portion to achieve uniform heat distribution, i.e., similar thermal gradients between cells in the stack. This improves the duty cycle of the solid oxide cell stack and extends the stack life.

[0034] The cell stack arrangement according to the present invention can include a flow-restricting orifice that opens into the flow distribution region and the fluid outlet region. In one embodiment, a means can be used to guide the fuel supply flow from the side of the fuel cell to the flow distribution region. A gasket structure is compressed over the flow-restricting orifice. The flow-restricting orifice ensures uniform fuel flow distribution across the active area of ​​the fuel cell electrode by creating an additional pressure sink in the flow path. The gasket structure also creates similar pressure drop conditions between the fuel cell repeats, ensuring uniform flow distribution characteristics for each fuel cell repeat. The uniform flow distribution within the fuel cell stack also ensures uniform heat distribution conditions for the fuel cell stack, i.e., similar thermal gradients between cells within the stack. This improves the duty cycle of the fuel cell stack and extends the life of the fuel cell stack.

[0035] The purpose of the gasket structure is to further ensure that oxidant and fuel do not mix directly within the electrochemically active area without a fuel cell reaction, that fuel and oxidant do not leak out of the electrochemical cell, that adjacent electrochemical cells do not come into electronic contact with each other, and that oxidant and fuel are delivered to the desired flow plate. Flow plates are flat, thin plates made of metal alloys, ceramic materials, cermet materials, or other materials capable of withstanding the chemical, thermal, and mechanical stresses present in a fuel cell. The oxygen-rich gas can be any gas or gas mixture containing a measurable amount of oxygen.

[0036] While the basic novel features of the present invention as applied to the preferred embodiments thereof have been illustrated, described, and pointed out, it will be understood that various omissions, substitutions, and changes in form and detail of the present invention may be made by those skilled in the art without departing from the spirit of the invention. For example, all combinations of elements which achieve substantially the same results are expressly intended to be within the scope of the present invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated. It should also be understood that the drawings are not necessarily drawn to scale and are merely conceptual in nature. It is therefore intended to be limited only as indicated by the scope of the appended claims.

Claims

1. a modular arrangement of solid oxide cell stacks in a fuel cell system or an electrolyzer cell system, each stack comprising a unit cell including a fuel side, an oxygen-rich side, and an electrolyte material between the fuel side and the oxygen-rich side; each stack comprising a flow plate made of a material having high electrical conductivity at high temperatures; each stack having a four-angled configuration; each stack comprising a gas seal structure made of an electrically insulating material; the modular arrangement having an internal gas distribution structure for both the inlet and outlet sides of fuel gas; the oxygen-side gas supply is based on an open structure; the modular arrangement comprising end plates used for current collection; the cells, flow plate, and gas seal structure are arranged in piles to form a stack between the end plates; the modular arrangement being arranged in a 2×N matrix, N being any natural number; the modular arrangement comprising a fuel inlet manifold and a fuel outlet manifold between two adjacent stacks; the fuel inlet manifold and the fuel outlet manifold supply fuel gas to the stacks and to separate fuel from the stacks; a fuel manifold is formed to supply exhaust gas, the stacks are arranged in parallel connection in the fuel manifold in terms of fuel gas supply and fuel exhaust gas connection, the stacks are arranged with a common oxygen side gas supply compartment connecting to the inlet side of the open structure for oxygen side gas supply and a common oxygen side gas exhaust compartment connecting to the outlet side of the open structure for oxygen side gas supply, the fuel inlet manifold includes gas flow holes of controllable size for the stack to form a uniform gas flow into the stack, the fuel outlet manifold includes gas flow holes of controllable size for the stack to form a uniform gas flow from the stack, the module arrangement includes a first gas seal, a first electrical insulation plate, and a second gas seal between the fuel manifold and the stack, the module arrangement includes a second electrical insulation plate and a compression structure for the stack on the upper and lower sides of the stack, and an air side seal structure between the stacks, each stack end plate is connected to an electrical connection, the module arrangementA modular arrangement comprising said fuel inlet and outlet manifolds interconnected by welding to enhance structural rigidity and strength.

2. 10. The modular arrangement of claim 1, wherein said modular arrangement includes means for controlling the size of individual gas flow holes to provide uniform gas flow between said stacks.

3. 2. The modular arrangement of claim 1, wherein said fuel manifold has an inlet pipe connection at a first end thereof and an outlet pipe connection at a first end thereof.

4. 2. The module arrangement of claim 1, wherein the air-side seal structure includes a hard ceramic in the center portion and a soft ceramic in the edge portion.

5. 2. The modular arrangement of claim 1, wherein the fuel manifold and the stack cover portion are made of at least one material having a similar coefficient of thermal expansion.

6. 2. The modular arrangement of claim 1, wherein said first electrically insulating plate is made of at least one high density material.

7. 2. The modular arrangement of claim 1, wherein said second electrically insulating plate is made of at least one porous material.

8. 2. The modular arrangement of claim 1, wherein said fuel manifold is made of ferritic steel.

9. 10. The modular arrangement of claim 1, wherein the modular arrangement includes at least two cell stack pairs electrically arranged in a series connection.

10. 2. The module arrangement of claim 1, wherein the module arrangement includes X cell stacks arranged in series connection, where X is a natural number, and satisfies 2N / X=Y, where N and Y are natural numbers.

11. 2. The modular arrangement of claim 1, wherein the modular arrangement comprises a compensation structure above or below the stack for compensating for height tolerances between the stacks.

12. The modular arrangement of claim 1 , further comprising: an airtight structure in which the fuel manifold, stack, seal structure, and electrical insulating plate are located; and the air-side seal structure sealed to the airtight structure.

13. 13. The modular arrangement of claim 12, wherein the modular arrangement comprises the compression structure inside the airtight structure.

14. 13. The modular arrangement of claim 12, wherein the modular arrangement comprises the compression structure outside the airtight structure.

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