WO2020018832A1

WO2020018832A1 - Air cooling arrangement for a co-axial array of fuel cell stacks

Info

Publication number: WO2020018832A1
Application number: PCT/US2019/042462
Authority: WO
Inventors: George Skinner
Original assignee: Ballard Power Systems Inc.; Ballard Material Products Inc.
Priority date: 2018-07-20
Filing date: 2019-07-18
Publication date: 2020-01-23

Abstract

A fuel cell stack assembly comprises a co-axial array of air-cooled fuel cell stacks placed in an enclosure having an air inlet and an air outlet and an air circulating device comprising one or more fans for circulating air through the fuel cell stacks. The air-cooling arrangement comprises a series of baffles which are placed between the fuel cell stacks to divide the main air intake stream into side air intake streams which circulate through the fuel cell stacks and to guide the side air exhaust streams exiting the fuel cell stacks to a main air exhaust stream which exits the enclosure.

Description

AIR COOLING ARRANGEMENT FOR A CO-AXIAL ARRAY

OF FUEL CELL STACKS

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a fuel cell stack assembly comprising an air cooling arrangement for a co-axial array of fuel cell stacks which use air as oxidant and coolant.

Description of the Related Art

Fuel cells are devices in which fuel and oxidant fluids electrochemically react to generate electricity. A type of fuel cell being developed for various commercial applications is the solid polymer electrolyte fuel cell, which employs a membrane electrode assembly (MEA) comprising a solid polymer electrolyte made of a suitable ionomer material ( e.g ., Nafion^®) disposed between two electrodes. Each electrode comprises an appropriate catalyst located next to the solid polymer electrolyte. The catalyst forms a catalyst layer and may be, for example, a metal black, an alloy, or a supported metal catalyst such as platinum on carbon. A fluid diffusion layer (a porous, electrically conductive sheet material) is generally employed adjacent to the electrode for purposes of mechanical support and/or reactant distribution.

For commercial applications, a plurality of fuel cells are generally stacked in series in order to deliver a greater output voltage. Separator plates are typically employed adjacent the gas diffusion electrode layers in solid polymer electrolyte fuel cells to separate one cell from another in a stack. In a fuel cell stack, if a separator plate is adjacent to one cell’s anode on one side and to another cell’s cathode on the other side, it is referred to as a bipolar plate. Fluid distribution features, including inlet and outlet ports, fluid distribution plenums and numerous fluid channels, are typically formed in the surface of the separator plates adjacent to the electrodes in order to distribute reactant fluids to, and remove reaction by-products from, the electrodes. Such separator plates are also referred to as flow field plates. These bipolar separator/flow field plates also provide a path for electrical and thermal conduction, as well as mechanical support and dimensional stability to the MEA.

Certain fuel cell types are liquid cooled and, along with anode and cathode flow fields, also employ coolant flow fields. The coolant flow field is frequently located between an anode flow field and a cathode flow field in a composite (two piece) separator plate.

In air cooled fuel cells, the cathode flow field can serve both for oxidant distribution and for cooling purposes. Therefore, the cathode flow field is sized appropriately to serve both purposes and a separate coolant flow field is generally not employed.

In the air cooled fuel cells, the air provided to the stack as a reactant and also for cooling can be supplied by means of a fan through an intake duct and is sucked into the fuel cell stack through its air intake side. The air leaves the fuel cell through the opposite side of the cell, through the air exhaust side.

In air cooled fuel cell systems comprising more than one stack of fuel cells, the stacks have generally been arranged such that the air streams supplied to and exhausted from each stack are on parallel axes. This ensures that stack cooling streams do not interfere with each other. An example of such an arrangement is illustrated in Figure 3 of the United States patent application 2016/0056482, where each fuel cell stack 66 is provided with a suction fan 57 whereby parallel air flows are supplied to the fuel cell stacks.

While such systems are functioning well and provide adequate cooling to the fuel cell stacks by ensuring that the air cooling streams do not interfere with each other, they require a lot of space and have a lower packaging density.

Air has also been used for cooling other power producing systems like batteries. In some battery systems which comprise several co-axially arranged battery stacks, the cooling air stream provided by a fan flows from one battery to the next, respectively from the exhaust side of a battery in the stack to the intake side of the next battery in the stack, as illustrated for example in Japanese patent application number 2017004896. In other systems, for example, in the battery system illustrated in the United States patent 9,413,045, the cooling air stream supplied by a fan is divided into parallel air streams which are each supplied to a battery stack.

Nevertheless, the requirements for operating a battery system for vehicles are different than those for fuel cell powering systems, because for batteries, only the exterior of the battery packs have to be cooled and therefore the arrangements for cooling battery packs do not have to take in consideration the restrictions imposed by the air serving as a reactant in the power pack. As such, in batteries, the air streams do not need to flow directly through the stacks and do not need to be guided through the air supply channels of the flow field plates, as is the case with the air cooled fuel cell stacks.

While advances have been made in the field of air cooled fuel cells, there remains a need for improved an air cooling arrangement for a fuel cell system that is more compactly packed, for example for a fuel cell system where the air cooled stacks are arranged in a co-axial array. The present invention addresses this need and provides other associated benefits.

BRIEF SUMMARY OF THE INVENTION

In brief, an air-cooled fuel cell stack assembly is provided comprising an array of fuel cell stacks having at least two fuel cell stacks arranged along the same axis and placed within an enclosure which is provided with an air inlet and an air outlet.

Each fuel cell stack comprises a series of fuel cells having flow field plates provided with channels for circulating air through the stack to serve as a reactant and to also serve as coolant and each fuel cell stack has an air intake side and an air exhaust side.

The fuel cell stack assembly further comprises an air circulating device for sucking air from the outside of the enclosure through the air inlet to create a main air intake stream and a series of baffles, each baffle being placed between two neighboring fuel cells stacks from the array of fuel cell stacks, more specifically between the air exhaust side of one fuel cell stack and the air intake side of the neighbouring fuel cell stack The baffles are shaped to divide the main air intake stream into side air intake streams, to direct the side air intake streams to the air intake side of each fuel cell stack and to direct side air exhaust streams exiting the fuel cell stacks through the air exhaust side of each fuel cell stack to a main air exhaust stream and towards the air outlet of the enclosure.

In some embodiments, the air circulating device in the fuel cell stack assembly comprises a series of fans, each fan being placed between the air exhaust side of one fuel cell stack and the baffle separating the fuel cell stack from a neighboring fuel cell stack. In some other embodiments the air circulating device can comprise only one fan positioned at the air outlet of the enclosure.

In some embodiments, the air inlet of the enclosure comprises air inlet duct. In other embodiments, the air inlet of the enclosure comprises an air inlet duct and the air intake side of the first fuel cell stack in the array of fuel cell stacks.

Similarly, in some embodiments the air outlet of the enclosure comprises an air outlet duct, while in other embodiments, the air outlet of the enclosure can comprise an air outlet duct and the air exhaust side of the last fuel cell stack in the array of fuel cell stacks.

In some embodiments, the enclosure is also shaped to divide the main air intake stream into one of the side air intake streams and to direct it to the air intake side of the first fuel cell stack in the array of fuel cells stacks and/or to direct one of side air exhaust streams which exits the last fuel cell stack in the array of fuel cell stacks to the main air exhaust stream exiting the enclosure through the air outlet.

A method is also disclosed for cooling a fuel cell stack assembly comprising an array of fuel cell stacks consisting of at least two fuel cell stacks arranged along the same axis, where each fuel cell stack comprises a series of fuel cells having flow field plates provided with channels for circulating air through the stack and each fuel cell stack having an air intake side and an air exhaust side, the array of fuel cell stacks being placed in an enclosure having an air inlet and an air outlet.

The method comprises sucking air from the outside of the enclosure through the air inlet by using an air circulating device to create a main air intake stream and dividing the main air intake stream into side air intake streams by a series of baffles, each baffle separating two neighboring fuel cells and being shaped to divide the air intake stream into side air intake streams. The method further comprises directing the side air intake streams by using the series of baffles to the air intake side each fuel cell stack, and directing side air exhaust streams formed by the air exiting the fuel cell stacks through the air exhaust side of each fuel cell stack by using the series of baffles to form a main air exhaust stream which exits the enclosure through the air outlet.

In some embodiments, the air is sucked in from the outside of the enclosure through the air inlet by a fan positioned at the air outlet of the enclosure, while in other embodiments the air is sucked in from the outside of the enclosure by a series of fans, each fan being placed between the air exhaust side of one fuel cell stack and the baffle separating the fuel cell stack from a neighboring fuel cell stack.

These and other aspects of the invention are evident upon reference in the attached drawings and following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the schematic of an air cooling arrangement for an array of co-axially arranged fuel cell stacks employing a separate fan for each fuel cell stack.

Figure 2 shows the schematic of an air cooling arrangement for an array of co-axially arranged fuel cell stacks employing one fan for the entire array of fuel cell stacks.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth in order to provide a thorough understanding of the various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures associated with fuel cells, fuel cell stacks, batteries and fuel cell systems have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments of the invention. Unless the context requires otherwise, throughout the specification and claims which follow, the word“comprise” and variations thereof, such as,“comprises” and“comprising” are to be construed in an open, inclusive sense, which is“including, but not limited to.”

The cooling air referred to in the present application is also used as a reactant in the fuel cells for producing electrical power.

An air-cooled fuel cell stack assembly 100 according to the present invention is illustrated in Figure 1. Fuel cell stacks 101, 102, 103 and 104 form a co- axial array of fuel cell stacks positioned in an enclosure 110 provided with an air inlet 112 and an air outlet 114. In this embodiment, the air inlet 112 and air outlet 114 are in the shape of an inlet duct and respectively an outlet duct. The fuel cell stacks 101, 102, 103 and 104 are coaxial, being positioned on the same axis 116. This makes the array of fuel cell stacks more compact and easier to accommodate in a fuel cell powered system, for example in in an unmanned aerial vehicle, an auto-vehicle, etc.

Each fuel cell stack comprises several polymer electrolyte membrane fuel cells with flow field plates provided with reactant channels for supplying fuel and air to each fuel cell in the stack, as known in the prior art. Each fuel cell stack has an air intake side, for example air intake side 161, for fuel cell stack 101, through which air is supplied to the stack, and an air exhaust side 162 through which air is exhausted from the stack. In such stacks the air supplied to the stacks serves as a reactant (oxidant) and also helps cool the stacks. The fuel cell stacks in the array are separated from each other by baffles 121, 122 and 123 which help direct the air flow as further described below.

The air circulation device comprises fans 131, 132, 133 and respectively 134, each fan being placed next to the air exhaust side of one of the fuel cell stacks, between the air exhaust side of the fuel cell stack and the baffle separating the fuel cell stack from the fuel cell stack next to it. Fans 131, 132, 133 and 134 are sucking air from the outside of the enclosure 110 through inlet 112 to create a main air intake stream 170 which is divided into side air intake streams 151, 154, 155 and 156 each air intake stream being supplied to one fuel cell stack in the array of fuel cell stacks. In the illustrated embodiment, side air intake stream 151 is sucked in by fan 131 and is directed by a wall of the enclosure 110 to the air intake side 161 of the fuel cell stack 101. Air is exhausted from the fuel cell stack 101 and from fan 131 and forms a side air exhaust stream 152 which is directed by baffle 121 to the outlet pathl 18 which communicates with air outlet 114. Similarly, side air intake streams 154, 155 and respectively 156 are divided from the main air intake stream 170 being sucked in by fans 132, 133 and respectively 134, and the side air exhaust streams 157, 158 and 159 which are exhausted from the fuel cell stacks 102, 103 and 104 and respectively from fans 132, 133 and 134, are directed by baffles 122, 123 and respectively by a wall of the enclosure 110 to the outlet path 118, merging, together with side air exhaust stream 152 into a main air exhaust stream 180 which flows out of the enclosure 110 through the air outlet 114. As seen in Figure 1, the outlet path 118 is formed between the baffles and the enclosure to direct the air exhaust streams 152, 157, 158 and 159 to air outlet, and the enclosure 110 is also shaped to direct the air intake stream 151 to the first stack 101 and to direct the air exhaust stream 159 to the air outlet 114.

An air-cooled fuel cell stack assembly 200 according to a second embodiment of the present invention is illustrated schematically in Figure 2. Fuel cell stacks 201, 202, 203 and 204 form a co-axial array of fuel cell stacks which are positioned in an enclosure 210 provided with an air inlet and an air outlet. Fuel cell stacks 201, 202, 203 and 204 are positioned on the same axis 216. Each fuel cell stack in the array has an air intake side and an air exhaust side, for example air intake side 261 for fuel cell stack 201, and air intake side 262 for fuel cell stack 204 through which air is supplied to the stack, and an air exhaust side, for example air exhaust side 263 for fuel cell stack 201 and air exhaust side 264 for fuel cell stack 204 through which air is exhausted from the stack. The air inlet of the enclosure in this embodiment comprises an air inlet duct 212 and the air intake side 261 of the fuel cell stack 201 which is placed at one end of the fuel cell array in the fuel cell stack assembly and the air outlet of the enclosure comprises an air outlet duct 214 and the air exhaust side 264 of the fuel cell stack 204 which is placed at the other end of the co-axial array of the fuel cell stacks. Each fuel cell stack comprises several polymer electrolyte membrane fuel cells with flow field plates provided with channels for supplying fuel and oxidant/cooling air to the cell, as known in the prior art. The fuel cell stacks in the array are separated from each other by baffles 221, 222 and 223 which help direct the flow of the air as further described below.

This second embodiment is different than the first embodiment because the air circulating device comprises only one fan 230 which is placed in the air outlet duct 214 instead of multiple fans illustrated in the first embodiment.

Fan 230 is sucking air from the outside of the enclosure 210 through the air inlet formed by the air inlet duct 212 and the air intake side 261 of the fuel cell stack 201 and the air is supplied to each of the fuel cell stack in the array of fuel cell stacks.

In the illustrated embodiment, side air intake stream 251 and main air intake stream 270 are sucked in by fan 230 and are supplied to the array of fuel cell stacks, whereby the side air intake stream 251 is supplied to the air intake side 261 of the fuel cell stack 201 and the main air intake stream 270 is divided by baffles 221, 222 and 223 into side air intake streams 254, 255 and 256 which are each supplied to the air intake side of each of the fuel cell stacks 202, 203 and 204. Side air exhaust streams 252, 257, and 258, which are exhausted from the fuel cell stacks 201, 202, 203 and 204 are directed by baffles 221, 222 and 223 to merge into a main exhaust air stream 280 which flows out of the enclosure 210 through the air outlet 214 and fan 230. The side air exhaust stream 259 comes out of the air exhaust side of fuel cell stack 204 and flows into the environment surrounding the fuel cell assembly 200.

Each embodiment of the present invention has its own advantages. The first embodiment illustrated in Figure 1 has the advantage that the flow of the air through each of the fuel cell stack can be easier controlled and adapted to the respective cooling needs of the stack. The second embodiment illustrated in Figure 2 has the advantage of a simplified construction which is more compact and where the air circulating device, fan 230 can be easier replaced.

The advantages of the present invention consist of having a compact system of coaxial fuel cell stacks, each fuel cell stack being supplied with a separate air intake stream which comprises fresh air from the outside of the system’s enclosure and generating an air exhaust stream which is directed through an outlet path to the air outlet, such that the air exhaust stream of each stack does not come into contact with the air inlet stream of the stack next to it.

All of the above U.S. patents, U.S. patent application publications, U.S patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including, but not limited to U.S. Provisional Patent Application No. 62/701, 285 are incorporated herein by reference in their entirety.

While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore contemplated by the appended claims to cover such modifications that incorporate those features coming within the scope of the invention.

Claims

CLAIMS What is claimed is:

1. An air-cooled fuel cell stack assembly comprising:

an array of fuel cell stacks comprising at least two fuel cell stacks arranged along the same axis, each fuel cell stack comprising a series of fuel cells having flow field plates provided with channels for circulating air through the stack and each fuel cell stack having an air intake side and an air exhaust side;

an enclosure having an air inlet and an air outlet;

an air circulating device for sucking air from the outside of the enclosure through the air inlet to create a main air intake stream;

a series of baffles, each baffle being placed between two neighboring fuel cells stacks from the array of fuel cell stacks,

wherein the array of fuel cell stacks is placed within the enclosure and the baffles placed between the fuel cell stacks are shaped to divide the main air intake stream into side air intake streams, to direct the side air intake streams to the air intake side of each fuel cell stack and to direct side air exhaust streams exiting the fuel cell stacks through the air exhaust side of each fuel cell stack to a main air exhaust stream exiting the enclosure through the air outlet.

2. The air-cooled fuel cell stack assembly of claim 1 wherein the air circulating device comprises a series of fans, each fan being placed between the air exhaust side of one fuel cell stack and the baffle separating the fuel cell stack from a neighboring fuel cell stack.

3. The air-cooled fuel cell stack assembly of claim 1 wherein the air circulating device comprises a fan positioned at the air outlet of the enclosure.

4. The air-cooled fuel cell stack assembly of claim 1 wherein the air inlet of the enclosure comprises air inlet duct.

5. The air-cooled fuel cell stack assembly of claim 1 wherein the air inlet of the enclosure comprises an air inlet duct and the air intake side of the first fuel cell stack in the array of fuel cell stacks.

6. The air-cooled fuel cell stack assembly of claim 1 wherein the air outlet of the enclosure comprises an air outlet duct.

7. The air-cooled fuel cell stack assembly of claim 1 wherein the air outlet of the enclosure comprises an air outlet duct and the air exhaust side of the last fuel cell stack in the array of fuel cell stacks.

8. The air cooled fuel cell stack assembly of claim 1 wherein the enclosure is also shaped to divide the main air intake stream into one of the side air intake streams and to direct it to the air intake side of the first fuel cell stack in the array of fuel cells stacks and/or to direct one of side air exhaust streams which exits the last fuel cell stack in the array of fuel cell stacks to the main air exhaust stream exiting the enclosure through the air outlet.

9. A method for cooling a fuel cell stack assembly comprising an array of fuel cell stacks consisting of at least two fuel cell stacks arranged along the same axis, each fuel cell stack comprising a series of fuel cells having flow field plates provided with channels for circulating air through the stack and each fuel cell stack having an air intake side and an air exhaust side, the array of fuel cell stacks being placed in an enclosure having an air inlet and an air outlet, the method comprising:

sucking air from the outside of the enclosure through the air inlet by using an air circulating device to create a main air intake stream; dividing the main air intake stream into side air intake streams by a series of baffles, each baffle separating two neighboring fuel cells and being shaped to divide the air intake stream into side air intake streams,

directing the side air intake streams by using the series of baffles to the air intake side each fuel cell stack, and

directing side air exhaust streams formed by the air exiting the fuel cell stacks through the air exhaust side of each fuel cell stack by using the series of baffles to form a main air exhaust stream which exits the enclosure through the air outlet.

10. The method of claim 9 wherein the air is sucked in from the outside of the enclosure through the air inlet by a fan positioned at the air outlet of the enclosure.

11. The method of claim 9 wherein the air is sucked in from the outside of the enclosure by a series of fans, each fan being placed between the air exhaust side of one fuel cell stack and the baffle separating the fuel cell stack from a neighboring fuel cell stack.