The present disclosure relates to the field of fuel cell plate assemblies and methods of assembling fuel cell plate assemblies, and in particular, although not exclusively, to fuel cell plate assemblies that can be put together to form a fuel cell stack and methods of assembling a fuel cell stack.
Conventional electrochemical fuel cells convert fuel and oxidant, generally both in the form of gaseous streams, into electrical energy and a reaction product. A common type of electrochemical fuel cell for reacting hydrogen and oxygen comprises a polymeric ion (proton) transfer membrane, with fuel and air being passed over respective sides of the membrane. Protons (i.e. hydrogen ions) are conducted through the membrane, balanced by electrons conducted through a circuit connecting the anode and cathode of the fuel cell. To increase the available voltage, a stack may be formed comprising a number of such membranes arranged with separate anode and cathode fluid flow paths. Such a stack is typically in the form of a block comprising numerous individual fuel cell plates held together by end plates at either end of the stack.
Because the reaction of fuel and oxidant generates heat as well as electrical power, a fuel cell stack requires cooling once an operating temperature has been reached. Cooling may be achieved by forcing air through the cathode fluid flow paths. In an open cathode stack, the oxidant flow path and the coolant path are the same, i.e. forcing air through the stack both supplies oxidant to the cathodes and cools the stack.
According to a first aspect of the invention, there is provided a method of assembling a fuel cell plate assembly, the method comprising:
Such a method enables convenient and efficient assembly at a single build point, and does not require a significant amount of human intervention. Also, it is advantageous to provide a consistent assembly plateau by lowering the build point platform between component placement operations.
The method may be automated.
The method may further comprise placing the prefabricated MEA and the second fluid diffusion layer onto, and in sealing engagement with, the first track of adhesive such that a face of the prefabricated MEA and second fluid diffusion layer is in sealing engagement with the first track of adhesive.
Dispensing an adhesive may comprise screen printing the adhesive and/or placing a semi-fluid adhesive in a desired location using transfer tape.
There may be provided a method of assembling a fuel cell stack, the method comprising:
The method may further comprise compressing the first end plate, plurality of fuel cell plate assemblies and second end plate. Advantageously, this compressing can be performed at the build point on the build point platform.
The method may further comprise securing the first end plate, plurality of fuel cell plate assemblies and second end plate in the compressed state. Advantageously, this securing can be performed at the build point on the build point platform.
The bipolar plates may have a first and/or a second port. The method of assembling a fuel cell plate assembly may further comprise:
The second and third tracks of adhesive may provide seals between respective ports of adjacent bipolar plates in the fuel cell stack. In this way, a fluid communication gallery can be provided through the thickness of the fuel cell stack in order to provide fluid to each of the fuel cell plate assemblies.
The method may further comprise exposing the one or more tracks of adhesive to ultraviolet light to cure the adhesive. It can be advantageous to cure the adhesive after the fuel cell stack has been assembled so as not to take up valuable time at the build point. This can improve the time of manufacture per fuel cell stack and provide an increase throughput for the method of assembly.
According to a further aspect of the invention, there is provided a fuel cell plate assembly comprising:
There may be provided a fuel cell stack comprising:
The bipolar plates may have a first and/or a second port. The fuel cell plate assemblies may further comprise:
The second and third tracks of adhesive may be configured to provide seals between respective ports of adjacent bipolar plates in the fuel cell stack.
A description is now given, by way of example only, with reference to the accompanying drawings, in which:
One or more embodiments disclosed herein relate to a method of assembling a fuel cell plate assembly and a fuel cell stack at a single build point on a build point platform. The method can be automated and can provide an efficient and convenient method for assembly that does not require significant, or any, human intervention. Advantageously the build point platform can be lowered after component placement operation in order to provide a consistent location.
The active area 105 can be considered as the footprint/area of the gas diffusion layers (GDLs) that are in contact with the electrode surfaces such that the electrodes are provided with the necessary reactant gasses to promote proton exchange through the membrane.
The port 104 receives the fluid in a direction that is through the thickness of the bipolar plate 102. In addition to providing the fluid to the electrode, the port 104 also passes the fluid to an adjacent fuel cell assembly in a fuel cell stack as the ports of the bipolar plates are aligned when the stack is constructed.
In this example, the bipolar plate 102 has a plurality of fluid flow channels 106, which are discontinuous and extend across a lateral width of the bipolar plate 102. In this way, the fluid can be laterally dispersed across the width of the active area 105 when the fluid enters the fluid flow channels 106.
As will be discussed in more detail below, the fluid passes along the longitudinal length of the bipolar plate 102 through a gas diffusion layer. However, one or more optional port channels 108 can provide a fluid connection between the port 104 and the active area 105. The port channels 108 can be provided as grooves in the bipolar plate 102. The relationship between the port channels 108 and the fluid diffusion layer will be described in more detail below with reference to
In addition, one or more optional connecting channels 107 can also transport the fluid between successive fluid flow channels 106 along the length of the bipolar plate 102. Such connecting channels 107 can also be provided as grooves in the bipolar plate 102. The connecting channels 107 may alternate between connecting different ends of the fluid flow channels 106 so as to provide a winding or inter-digitized path along the longitudinal length of the bipolar plate 102. This can encourage the fluid to penetrate a large proportion of the fluid diffusion layer so that it is presented evenly to the electrode.
The anode GDL 210 has an extending region 212 that extends between the port 104 of the bipolar plate 102 and the active area 105. The tab 212 is outside the footprint of the active area 105. The extending region will be referred to as a tab 212. The tab 212 extends from the main body of the anode GDL 210, which in this example is generally co-located with the active area 105. The tab 212 of the anode GDL can communicate the hydrogen received at the port 104 to the active area 105. As identified above, the port channels 108 shown in
In other embodiments, the tab 212 can be considered as optional because the port channels 108 can be used to communicate fluid between the port 104 and the active area 105.
The adhesive is selected such that penetration of the adhesive into the tab 212 of the anode GDL 210 is minimal, thereby not significantly impeding fluid transport through the anode GDL 210.
The 4-layer MEA 418 is positioned over the first track of adhesive 316. It can be seen from
In this way the prefabricated MEA and second fluid diffusion layer 418 is placed in sealing engagement with the dispensed adhesive 316 and thereby forms a seal between the bipolar plate 102, the peripheral edge of the first fluid diffusion layer 210 and the MEA and second fluid diffusion layer 418. In some examples, a bottom face of the prefabricated MEA and second fluid diffusion layer 418 can be in sealing engagement with the dispensed adhesive 316.
The active area is defined within the periphery of the 4-layer MEA 418 as an outer band of the 4-layer MEA 418 is positioned over the adhesive 316, which prevents the transport of the anode gas (hydrogen) to the electrode. It will be appreciated that the placement of the adhesive can be controlled so as to minimise the displacement of the adhesive into the intended active area 105.
As shown in
The bipolar plates may comprise a separate anode sheet 602a and a cathode sheet 602b that are only joined together, for example resistance, laser or adhesive bonded together shortly before the bipolar plate 102 enters the build point. This is shown in
Located on either side of the build point are a stack of anode GDLs 210 and a stack of 4-layer MEAs 418.
It will be appreciated that each of the construction steps illustrated by
The first end plate 1354, 1356, the plurality of fuel cell plate assemblies and the second end plate 1350, 1352 can be compressed at the build point or elsewhere in order to compress the components to a working dimension. Alternatively, the components may be compressed to a dimension that is slightly smaller than the working dimension so that clips 1358, 1360 can conveniently be attached to the plates to secure the fuel cell assembly together.
Clips 1358, 1360 can be attached to each side of the fuel cell stack 1362 to keep the fuel cell plate assemblies together at the intended working dimension in order to provide a completed fuel cell stack 1361. The clips 1358, 1360 can be attached to the fuel cell stack 1362 before or after it is moved from its original build point.
In some examples, the dispensed adhesive can be exposed to a curing environment either during or after the fuel cell stack is assembled. A suitable curing environment may be provided by exposing the fuel cell stack to ultraviolet light and/or a suitable curing temperature. The structure of the fuel cell plates of this embodiment can be well suited to exposure to ultraviolet light as a least a portion of each track of adhesive can be exposed from between the stacked fuel cell plate assemblies.
The method begins at step 1602 by placing a bipolar plate on a build point platform. The build platform can then be lowered at step 1604 in some embodiments, for example such that the top of the bipolar plate is at the same height as the original height of the build platform. That is, the build platform may be lowered by a distance equal to the thickness of the bipolar plate.
At step 1606, the method of assembly continues by placing a prefabricated first fluid diffusion layer on, and in alignment with, the bipolar plate. The build platform can then be lowered at step 1608, for example such that the top of the prefabricated first fluid diffusion layer is at the same height as the original height of the build platform. That is, the build platform may be lowered by a distance equal to the thickness of the prefabricated first fluid diffusion layer.
At step 1610, the method continues by dispensing a first track of adhesive adjacent both the bipolar plate and a peripheral edge of the first fluid diffusion layer. In some examples, method step 1610 may also involve dispensing a second track of adhesive as a loop around a first port of the bipolar plate and/or dispensing a third track of adhesive as a loop around a second port of the bipolar plate.
The adhesive can be dispensed by screen printing a liquid adhesive or placing a semi-fluid adhesive in the desired location using transfer tape.
At step 1612, the method continues by placing a prefabricated MEA and second fluid diffusion layer in sealing engagement with the first track of adhesive. This can form a seal between the bipolar plate, the peripheral edge of the first fluid diffusion layer and the MEA and second fluid diffusion layer.
It will be appreciated that in some examples the build point platform can be, but need not necessarily be, lowered before or after any or all of the placing and dispensing steps 1602, 1606, 1610, 1612. The specific increment that the build point platform is lowered can be different for different lowering operations. The specific increment that the build point platform is lowered does not necessarily need to be related to every component placed.
The method of
Any “prefabricated” layers disclosed herein may be considered as unitary, self-supporting, layers that can be provided to a build point as a single component.
Number | Date | Country | Kind |
---|---|---|---|
1209362.1 | May 2012 | GB | national |
This patent application claims priority to International Patent Application PCT/GB2013/051309 filed on May 20, 2013, which claims priority to United Kingdom Patent Application 1209362.1 filed on May 28, 2012, the contents of which are incorporated here in their entirety.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/GB2013/051309 | 5/20/2013 | WO | 00 |