Fuel cell stack assembly including heat sink insert

Abstract

To provide a fuel cell column capable of achieving a smaller temperature distribution within fuel cell stacks and within the column as a whole.SOLUTION: A fuel cell column 140 includes a plurality of fuel cell stacks 14, at least one fuel manifold 204 configured to provide fuel to the plurality of fuel cell stacks 14, and at least one heat sink insert 301 located between adjacent fuel cells of the plurality of fuel cell stacks.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates generally to fuel cell systems, and more particularly to fuel cell stack assemblies having heat sink inserts. [Background technology]

[0002] Fuel cells are electrochemical devices that can convert energy stored in a fuel into electrical energy with high efficiency. High-temperature fuel cells include solid oxide fuel cells and molten carbonate fuel cells. These fuel cells can operate using hydrogen and / or hydrocarbon fuels. There are classes of fuel cells, such as reversible solid oxide fuel cells, that are also capable of reverse operation, such that water or other oxidized fuels can be reduced to unoxidized fuels using electrical energy as an input.

[0003] In high-temperature fuel cell systems, such as solid oxide fuel cell (SOFC) systems, an oxidizing stream passes through the cathode side of the fuel cell and a fuel stream passes through the anode side of the fuel cell. The oxidizing stream is typically air, and the fuel stream is typically a hydrogen-rich gas produced by reforming a hydrocarbon fuel source. When the fuel cell operates at typical temperatures between 750°C and 950°C, negatively charged oxygen ions can be transferred from the cathode flow stream to the anode flow stream, where the ions combine with free hydrogen or hydrogen in hydrocarbon molecules to form water vapor and / or with carbon monoxide to form carbon dioxide. Excess electrons from the negatively charged ions are directed back to the cathode side of the fuel cell through an electrical circuit completed between the anode and cathode, resulting in the flow of electrical current through the circuit.

[0004] Fuel cell stacks can be internally or externally manifolded for fuel and air. In an internally manifolded stack, fuel and air are distributed to each cell using risers contained within the stack. In other words, gas flows through openings or holes in each fuel cell's support layer, such as the electrolyte layer, and through each cell's gas separator. In an externally manifolded stack, the stack is open to inlet and outlet sides for fuel and air, and the fuel and air are introduced and collected independently of the stack hardware. For example, the inlet and outlet fuel and air flow in separate channels between the stack and the manifold housing in which the stack is located.

[0005] Fuel cell stacks are often constructed from multiple cells in the form of planar elements, tubes, or other geometric shapes. Fuel and air must be provided over a potentially large electrochemically active surface. One of the components of a fuel cell stack is a so-called gas flow separator (referred to as a gas flow separator plate in planar stacks) that separates the individual cells in the stack. The gas flow separator plate separates the fuel, such as hydrogen or a hydrocarbon fuel, flowing to the fuel electrode (i.e., anode) of one cell in the stack from the oxidant, such as air, flowing to the air electrode (i.e., cathode) of an adjacent cell in the stack. Often, the gas flow separator plate also serves as an interconnect, electrically connecting the fuel electrode of one cell to the air electrode of an adjacent cell. In this case, the gas flow separator plate, functioning as an interconnect, is made of or contains a conductive material. Summary of the Invention

[0006] A fuel cell column according to various embodiments of the present disclosure includes a plurality of fuel cell stacks, at least one fuel manifold configured to provide fuel to the plurality of fuel cell stacks, and at least one heat sink insert positioned between adjacent fuel cell stacks of the plurality of fuel cell stacks.

[0007] In various embodiments, the fuel cell column includes at least one heat sink insert positioned between adjacent fuel cell stacks in the column, which can reduce the peak temperature of the fuel cell stacks adjacent to the heat sink insert and can provide a smaller temperature distribution within the fuel cell stacks and across the column. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a three-dimensional view of a prior art fuel cell stack assembly. [Figure 2] FIG. 2 is a three-dimensional cross-sectional view of a fuel cell stack assembly including a heat sink insert according to one embodiment of the present disclosure. [Figure 3] FIG. 3 is a cross-sectional side view of a portion of a fuel cell stack assembly including two fuel cell stacks and a heat sink insert according to one embodiment of the present disclosure. [Figure 4] FIG. 4 is a top view of a heat sink insert for a fuel cell stack column according to one embodiment of the present disclosure. [Figure 5] FIG. 5 is a top view of a heat sink insert for a fuel cell stack column according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] When an element or layer is referred to as being "on" or "connected to" another element or layer, it is understood that the element or layer can be directly on or connected to the other element or layer, or that there can be intervening elements or layers. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element or layer, there are no intervening elements or layers. For purposes of this disclosure, it is understood that "at least one of X, Y, and Z" can be interpreted as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ, ZZ).

[0010] FIG. 1 illustrates a prior art fuel cell stack assembly 100 described in U.S. Patent Application Publication No. 2021 / 0351420, which is incorporated herein by reference in its entirety. Referring to FIG. 1, the fuel cell stack assembly 100 includes a fuel cell stack column 140, side baffles 220 disposed on both sides of the column 140, a compression assembly 60 including a lower block 53 and an upper block 63. In the exemplary fuel cell stack assembly 100 illustrated in FIG. 1, the column 140 includes eight fuel cell stacks 14, a fuel manifold 204 disposed between the fuel cell stacks 14, and end plates 27 disposed at both ends of the column 140. The fuel cell stack 14 includes multiple fuel cells stacked on top of each other and separated by interconnects. The interconnects can provide electrical interconnection between the fuel cell stacks and can also separate a fuel, such as a hydrocarbon fuel, flowing to a fuel electrode of one cell in the stack from an oxidant, such as air, flowing to an air electrode of an adjacent cell in the stack. The interconnects may also include gas flow passages or channels formed in the surfaces of the interconnects that provide fuel and oxidant flow across the electrodes of each fuel cell stack. At each end of the stack may be an end plate (e.g., an air end plate and a fuel end plate) that respectively provide air or fuel to the end electrodes of the stack. The outer surfaces of the end plates may be substantially flat and may abut another component of the fuel cell stack assembly 100, such as a fuel manifold 204 or another fuel cell stack 14 in a column 140. Multiple fuel cell stack assemblies 100 may be mounted to a base.

[0011] An exemplary fuel manifold 204 is described in U.S. Patent No. 10,511,047, which is incorporated herein by reference in its entirety. Any number of fuel manifolds 204 may be provided between adjacent end plates of adjacent fuel cells in the fuel cell stack 14, as desired.

[0012] The side baffle 220 connects the upper block 63 and the lower block 53 of the compression assembly 60. The side baffle 220, compression assembly 60, and lower block 53 can be collectively referred to as the "stack housing." The stack housing is configured to apply a compressive load to the column 140. The stack housing configuration eliminates costly feedthroughs and resulting tie rod heat sinks, and the same component (i.e., the side baffle 220) serves two purposes: to apply the load to the stack 14 and to direct the cathode supply flow stream (e.g., in the case of a ring-shaped stack, the cathode inlet stream, e.g., air or another oxidant, can be provided from a manifold external to the ring-shaped configuration through the stack and outlet as the cathode exhaust stream to a manifold located internal to the ring-shaped configuration). The side baffle 220 can also electrically isolate the fuel cell stack 14 from metallic components within the system. The load on the column 140 may be provided by the compression assembly 60, which is held in place by the side baffles 220 and the lower block 53. In other words, the compression assembly 60 may urge the stack 14 of the column 140 toward the lower block 53.

[0013] The side baffles 220 may be plate-shaped rather than wedge-shaped and may include a baffle plate 202 and a ceramic insert 46 configured to connect the baffle plate 202 to the lower block 53 and the compression assembly 60. In particular, the baffle plate 202 includes a generally circular cutout 52 within which the insert 46 is positioned. The insert 46 does not completely fill the cutout 52. The insert 46 is generally bowtie-shaped, but includes a flat edge 51 rather than a fully rounded edge. Thus, an open space remains above or below the insert 46 within each cutout 52.

[0014] Generally, the side baffles 220 are made from a high-temperature resistant material, such as alumina or other suitable ceramic. In various embodiments, the side baffles 220 are made from a ceramic matrix composite (CMC). The CMC can include, for example, a matrix of aluminum oxide (e.g., alumina), zirconium oxide, or silicon carbide. Other matrix materials can also be selected. The fibers can be made from alumina, carbon, silicon carbide, or any other suitable material. The lower block 53 and compression assembly 60 can also be made from the same or similar materials.

[0015] Any combination of matrix and fibers can be used. Additionally, the fibers can be coated with an interfacial layer designed to improve the fatigue properties of the CMC. If desired, the CMC baffle can be made from an integral piece of CMC material rather than separate interlocking baffle plates. The CMC material can increase baffle strength and creep resistance. When the baffle is made from alumina or alumina fiber / alumina matrix CMC, this material is a relatively good thermal conductor at typical SOFC operating temperatures (e.g., above 700°C). If thermal isolation of adjacent stacks or columns is desired, the baffle can be made from insulating ceramic or CMC material.

[0016] Other elements of the compression housing, such as lower block 53 and compression assembly 60, can also be made from the same or similar materials. For example, lower block 53 can include a ceramic material, such as alumina or CMC, that is separately attached (e.g., by inserts, dovetails, or other devices) to side baffles 220 and the system base. The use of a ceramic block material minimizes heat sink formation and eliminates the thermal expansion interface problems that would result from connecting a ceramic baffle to a metal base.

[0017] Fuel rails 214 (e.g., fuel inlet and outlet pipes or conduits) connect to fuel manifolds 204 located between stacks 14 in a column 140. The fuel rails 214 may include ceramic tubes 216 brazed to metal tubes 218, which, in one embodiment, may include compressible bellows tubes. A fuel cell rail 214 is used to deliver fuel to each pair of stacks 14 in a column 140 of fuel cell stacks via fuel cell manifolds 204. In these systems, the ceramic tubes 216 are located between adjacent fuel manifolds 204 to prevent short circuits between adjacent fuel manifolds 204 in a column 140. Alternatively, a dielectric material separator can be provided between the fuel manifold 204 and adjacent fuel cell stacks 14, and a jumper can be used to allow current to flow between adjacent fuel cell stacks 14 without passing through the fuel manifold 204. This is discussed in U.S. Patent Application Publication No. 2021 / 0351420. In such an embodiment, the fuel rail 214 may be made entirely of metal and the dielectric (e.g., ceramic) tube 216 is not required and may be omitted. In one embodiment, the fuel rail 214 includes only a metal bellows 218 and a straight metal tube.

[0018] In a fuel cell stack assembly 100 such as that shown in FIG. 1 , the temperature of the fuel cell stack 14 is not uniform. The highest temperature within the fuel cell stack 14 is often at the interface between the fuel cell stack 14 and an adjacent fuel cell stack 14 (i.e., the stack-to-stack interface). Peak temperatures in the fuel cell stack 14 can approach or even exceed the safe temperature limit of the stack seals. This temperature can be around 880°C for solid oxide fuel cell stacks. Peak stack temperatures exceeding the safe temperature limit can result in seal failure, which can lead to reduced cell performance and a reduced lifespan of the fuel cell stack assembly 100. Additionally, excessive temperatures near the stack-to-stack interface can result in undesirable variations in fuel utilization (FU) across the fuel cell columns 140.

[0019] Various embodiments of the present disclosure relate to a fuel cell stack assembly including one or more heat sink inserts positioned between adjacent fuel cell stacks of the assembly. In various embodiments, the fuel cell stack assembly can include a fuel cell stack column including a plurality of fuel cell stacks and at least one heat sink insert disposed between adjacent fuel cell stacks of the column. In embodiments, some of the adjacent fuel cell stacks of the column can be separated by a fuel manifold, and the remaining adjacent fuel cell stacks of the column can be separated by a heat sink insert. The heat sink insert, according to various embodiments, can reduce peak temperatures of the fuel cell column adjacent the heat sink insert, resulting in a tighter temperature distribution within the fuel cell stack and across the column.

[0020] FIG. 2 is a three-dimensional cross-sectional view of a fuel cell stack assembly 200 according to one embodiment of the present disclosure. The three-dimensional cross-sectional view of FIG. 2 is taken along the vertical centerline of the fuel cell stack assembly 200. The fuel cell stack assembly 200 shown in FIG. 2 can be similar to the assembly 100 shown in FIG. 1 and can include a fuel cell stack column 140, side baffles 220 disposed on both sides of the column 140, a compression assembly 60 including a lower block 53 and an upper block 63. In the exemplary fuel cell stack assembly 100 shown in FIG. 2, the column 140 includes eight fuel cell stacks 14, labeled M1 through M8. End plates 27 can be disposed at both ends of the column 140.

[0021] 2, the fuel cell stack assembly 200 includes a fuel manifold 204 and a heat sink insert 301 disposed between the fuel cell stacks 14 in the column 140. In the embodiment shown in FIG. 2, the fuel cell stack assembly 200 includes four fuel manifolds located between stacks M1 and M2, between stacks M3 and M4, between stacks M5 and M6, and between stacks M7 and M8. The fuel cell stack assembly 200 further includes three heat sink inserts 301 located between stacks M2 and M3, between stacks M4 and M5, and between stacks M6 and M7, respectively. Thus, each fuel cell stack 14 in the column 140 is adjacent to a fuel manifold 204 on one side of the fuel cell stack 14 and adjacent to either a heat sink insert 301 or an end plate 27 on the opposite side of the fuel cell stack 14.

[0022] Each of the heat sink inserts 301 may be located at a stack-to-stack interface between a pair of fuel cell stacks 14 in the column 140. The heat sink inserts 301 may have a first major surface that contacts the end plate of a first fuel cell stack 14 and a second major surface that contacts the end plate of a second fuel cell stack 14. The heat sink inserts 301 may be constructed from a suitable thermally conductive material, such as a metal or metal alloy. In some embodiments, the heat sink inserts 301 may be constructed from a chromium-iron alloy. In one non-limiting embodiment, the heat sink insert 301 can include a chromium-iron alloy having greater than about 80% by weight chromium, e.g., greater than about 90% by weight chromium, e.g., about 94% to 96% by weight (e.g., 95% by weight) chromium, greater than zero% to less than about 20% by weight iron, e.g., less than about 10% by weight iron, e.g., about 4% to 6% by weight (e.g., 5% by weight) iron, and less than about 2% by weight, e.g., zero% to 1% by weight, of other materials, e.g., yttrium or yttria, and residual or unavoidable impurities. Thus, in one embodiment, the heat sink insert 301 can be made from the same material as the interconnects in the fuel cell stack 14 (i.e., the Cr-Fe alloy described above). However, the heat sink insert 301 can be thicker than the interconnects to increase heat dissipation. Alternatively, the heat sink insert 301 can include a stainless steel material, such as grade 446 stainless steel (SS446). Other suitable materials for the heat sink insert 301 are within the contemplated scope of this disclosure.

[0023] Each of the heat sink inserts 301 can include a block of thermally conductive material. The block of thermally conductive material can be a single, integral piece, or can be comprised of multiple pieces that can optionally be welded or otherwise adhered or attached together to form the heat sink insert 301. In some other embodiments, described in more detail below with respect to FIG. 4, the heat sink insert 301 can have a segmented structure, where the separate pieces forming the insert 301 are not attached to each other, allowing them to "float" independently of each other. In various embodiments, each heat sink insert 301 can have a thickness dimension (i.e., height) between adjacent fuel cell stacks 14 of about 1 mm to 10 mm, e.g., about 3 mm to 7 mm, e.g., 5 mm to 6 mm (e.g., 5.4 mm). The thickness of each heat sink insert 301 can be correlated to the number of inserts 301 in a column 140 and the height of the column 140 (e.g., the maximum height of the column 140 that can fit into an assembly enclosure such as a "hot box").

[0024] The heat sink insert 301 can have a width dimension along a first horizontal direction (i.e., hd1 in FIG. 2 ) that allows the heat sink insert 301 to fit between the side baffles 220 of the fuel cell stack assembly 200. In some embodiments, the width dimension of the heat sink insert 301 can be substantially the same as the width dimension of an adjacent fuel cell stack 14. The heat sink insert 301 can also have a length dimension along a second horizontal direction (i.e., hd2 in FIG. 2 ). In some embodiments, the length dimension of the heat sink insert 301 can be substantially the same as the width dimension of an adjacent fuel cell stack 14.

[0025] Alternatively, as shown in Figure 3, the length dimension of the heat sink insert 301 along the second horizontal direction (hd2) may be greater than the length dimension of the fuel cell stack 14, such that the heat sink insert 301 extends laterally beyond the side of the fuel cell stack 14. The perspective shown in Figure 3 may be along a vertical plane that includes the second horizontal direction (hd2). However, because the ceramic baffle plates 202 are located on the other two sides of the column 140, the heat sink insert 310 has a width dimension between the ceramic baffle plates 202 that is the same as the width dimension of each of the adjacent fuel cell stacks 14 between the ceramic baffle plates 202.

[0026] It is estimated that a temperature reduction of approximately 8°C to 10°C can be achieved at the stack-to-stack interface of a column 140 having a heat sink insert 301 between adjacent fuel cell stacks 14 compared to a column 140 without a heat sink insert. It is also estimated that the embodiment column 140 with the heat sink insert 301 will have a lower maximum temperature and a tighter temperature distribution than the comparative column without the heat sink insert 301. Additionally, it is estimated that the peak temperature within the stack of the embodiment column will be in the middle region of the stack, rather than at the stack-to-stack interface as in the comparative column.

[0027] The reduction in overall peak temperature in the column of embodiments can help minimize or eliminate seal failure in the column. Additionally, the reduction in maximum column temperature, tighter temperature distribution within the column, and shifting of peak stack temperature from stack-to-stack interface regions to the middle region of the stack can improve fuel distribution throughout the fuel cell stack in the column. This can allow the column to operate at a higher fuel utilization rate, improving the efficiency of the fuel cell stack assembly.

[0028] FIG. 4 is a top view of a heat sink insert 301 for a fuel cell stack column according to one embodiment of the present disclosure. The heat sink insert 301 of FIG. 4 includes an open area 302 (indicated by a dashed line in FIG. 4 ), such as a slot or groove formed in the surface of the insert 301 or an internal opening in the insert 301 that extends from the periphery of the heat sink insert 301 to the central region of the heat sink insert 301. A temperature sensor 303, such as a thermocouple, may be provided in the open area 302 in the heat sink insert 301. The temperature sensor 303 may detect the temperature in the central region of the column 140, which may indicate the core temperature(s) of the adjacent fuel cell stack(s) 14. Providing the temperature sensor 303 in the central region of the heat sink insert 301 may improve monitoring of the fuel cell stack temperature under varying operating conditions and parameters, thereby improving control of the fuel cell stack operation.

[0029] FIG. 5 is a top view of a heat sink insert 301 for a fuel cell stack column according to another embodiment of the present disclosure. The heat sink insert 301 of FIG. 5 has a segmented structure including multiple separate pieces 305a, 305b separated by an expansion zone 307. A heat sink insert 301 having a segmented structure can include any number of separate pieces 305 (e.g., two or more), which can have any suitable size and / or shape. The expansion zone 307 can be an open space between the pieces 305a, 305b, a space filled with a sealing material, or an interface where the sidewalls of the separate pieces 305a, 305b meet each other. In some embodiments, the separate pieces 305a, 305b of the heat sink insert 301 can be unconnected to each other, allowing the separate pieces 305a, 305b to "float" independently of each other. This can help reduce thermal stresses applied to adjacent fuel cell stacks during thermal cycling.

[0030] While the foregoing represents particularly preferred embodiments, it will be understood that the present invention is not limited thereto. Those skilled in the art will recognize that various modifications can be made to the disclosed embodiments and that such modifications are intended to be within the scope of the present invention. All publications, patent applications, and patents cited herein are hereby incorporated by reference in their entirety.

Claims

1. a plurality of fuel cell stacks; at least one fuel manifold configured to provide fuel to the plurality of fuel cell stacks; at least one heat sink insert positioned between adjacent fuel cell stacks of the plurality of fuel cell stacks; Equipped with the adjacent fuel cell stacks include a first fuel cell stack disposed above a second fuel cell stack; the first fuel cell stack includes a first end plate disposed at a lower portion of the first fuel cell stack; the second fuel cell stack includes a second end plate disposed at an upper end of the second fuel cell stack; the first end plate and the second end plate are made of the same material; the at least one heat sink insert includes a first heat sink insert disposed between the first end plate of the first fuel cell stack and the second end plate of the second fuel cell stack; the first heat sink insert having a first major surface in physical contact with the first end plate of the first fuel cell stack and a second major surface in physical contact with the second end plate of the second fuel cell stack; the first heat sink insert has an open region therein that includes an interior opening extending from a periphery of the heat sink insert to a central region thereof; Fuel cell column.

2. 2. The fuel cell column of claim 1, wherein the at least one heat sink insert comprises an essentially single, integral block of thermally conductive material that contacts a first fuel cell stack on a first side of the heat sink insert and contacts a second fuel cell stack on a second side of the heat sink insert.

3. 3. The fuel cell column of claim 2, wherein the at least one heat sink insert comprises a chromium-iron alloy.

4. 4. The fuel cell column of claim 3, wherein the chromium-iron alloy contains at least 80% by weight chromium, greater than zero and less than 20% by weight iron, and zero to less than 2% by weight at least one of yttria or yttrium.

5. The fuel cell column of claim 2 , wherein the at least one heat sink insert comprises stainless steel.

6. 10. The fuel cell column of claim 1, wherein said at least one heat sink insert has at least one of a length dimension and a width dimension that is the same as a length dimension and a width dimension of each of said adjacent fuel cell stacks in said column.

7. the fuel cell column includes a plurality of fuel manifolds and a plurality of heat sink inserts positioned between the plurality of fuel cell stacks; 2. The fuel cell column of claim 1, wherein each fuel cell stack of the plurality of fuel cell stacks contacts at least one of the plurality of fuel manifolds and the heat sink insert.

8. 8. The fuel cell column of claim 7, wherein the at least one heat sink insert is located between two of the plurality of fuel manifolds at an interface between adjacent two of the plurality of fuel cell stacks.

9. the plurality of fuel cell stacks are positioned between a pair of end plates; 9. The fuel cell column of claim 8, wherein each fuel cell stack of the plurality of fuel cell stacks contacts a fuel manifold on one side of the fuel cell stack and contacts either a heat sink insert or an end plate on an opposite side of the fuel cell stack.

10. The fuel cell column of claim 10 further comprising a temperature sensor disposed in the open area.

11. A fuel cell column as described in claim 1, wherein the at least one heat sink insert comprises a heat sink insert including separate first and second pieces separated by an expansion zone.

12. 10. The fuel cell column of claim 1, wherein the at least one heat sink insert has a thickness between a first side and a second side of the heat sink insert of between 1 mm and 10 mm.

13. The fuel cell column of claim 1 , wherein the plurality of fuel cell stacks comprises solid oxide fuel cell (SOFC) stacks.

14. 14. The fuel cell column of claim 13, wherein each of the SOFC stacks includes multiple SOFCs separated by multiple interconnects.

15. 15. The fuel cell column of claim 14, wherein each of the plurality of interconnects, the first end plate, and the second end plate comprises an alloy including 94 to 96 weight percent chromium, 4 to 6 weight percent iron, and zero to 1 weight percent at least one of yttrium or yttria.

16. 16. The fuel cell column of claim 15, wherein the at least one heat sink insert comprises an alloy including 94 to 96 weight percent chromium, 4 to 6 weight percent iron, and zero to 1 weight percent at least one of yttrium or yttria.

17. The fuel cell column of claim 16 , wherein the at least one heat sink insert is thicker than each of the plurality of interconnects.

18. 2. The fuel cell column of claim 1, wherein the at least one heat sink insert has a length dimension that is greater than a length dimension of each of the adjacent fuel cell stacks, such that the at least one heat sink insert extends laterally beyond a side of the adjacent fuel cell stack.

19. further comprising ceramic baffle plates located on two sides of the column; 20. The fuel cell column of claim 18, wherein the at least one heat sink insert has a width dimension between the ceramic baffle plates that is the same as a width dimension of each of the adjacent fuel cell stacks between the ceramic baffle plates.

20. A plurality of fuel cell stacks; at least one fuel manifold configured to provide fuel to the plurality of fuel cell stacks; at least one heat sink insert positioned between adjacent fuel cell stacks of the plurality of fuel cell stacks; Equipped with the adjacent fuel cell stacks include a first fuel cell stack disposed above a second fuel cell stack; the first fuel cell stack includes a first end plate disposed at a lower portion of the first fuel cell stack; the second fuel cell stack includes a second end plate disposed at an upper end of the second fuel cell stack; the first end plate and the second end plate are made of the same material; the at least one heat sink insert includes a first heat sink insert disposed between the first end plate of the first fuel cell stack and the second end plate of the second fuel cell stack; the first heat sink insert having a first major surface in physical contact with the first end plate of the first fuel cell stack and a second major surface in physical contact with the second end plate of the second fuel cell stack; the first heat sink insert includes separate first and second pieces separated by an expansion zone; Fuel cell column.

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