The disclosure relates generally to fuel cells, and more particularly to fluid flow assemblies for and/or in, fuel cell stacks.
Fuel cells, such as Proton Exchange Membrane (PEM) fuel cells, oftentimes are arranged in assemblies known as fuel cell stacks. In such a fuel cell stack, the fuel cells are oriented adjacent to each other. In particular, this orientation involves the cathode of one of the fuel cells being located adjacent to the anode of a next of the fuel cells. In operation, fuel reactant (e.g., hydrogen) flows through channels at the anodes and oxidant reactant (e.g., air) flows through channels at the cathodes. A coolant (e.g. water) may also flow in the fuel cell in proximity with the anode and cathode reactant flow channels.
Conventionally, two plates (e.g., stamped plates) can be positioned between two adjacent fuel cells to form the anode channels of one of the fuel cells and the cathode channels of the other. The channels serve to deliver fluid reactant to the respective anodes and cathodes via an array of flow channels collectively called flow fields, and thus the plates may be termed, individually or collectively, fluid flow field plates or, simply, flow field plates. One such example is disclosed in U.S. Pat. No. 5,981,098 to N. G. Vitale for ‘Fluid flow Plate for Decreased Density of Fuel Cell Assembly”. Specifically, when the flow field plates are positioned so that one overlies the other, the anode channels are formed on the outside of one of the plates, the cathode channels are formed on the outside of the other of the plates. In some embodiments, coolant channels are formed between the plates. In such configurations, and assuming the channels are formed by stamping the plates, the anode channels, cathode channels, and coolant channels if present, would be generally aligned, or matched.
However, such matching of channels, and thus flow paths, may not be desirable throughout the total extent of the channels. This is particularly the case where, as in most systems, the reactant flow fields are not only straight flow channels, but include turns to provide multiple passes across the plate throughout the zone or region termed the “active area”. The “active area” is that in which the well-known electrochemical reaction of the fuel cells takes place. In the region(s) or sub-zone(s) of the plates in which the anode and cathode flow fields may not be parallel, as for instance where turns in the flow of a reactant occur, it is desirable to afford the coolant flow fields on the back of each plate a directional independence of flow. To this end and referring briefly to
In order to accommodate the need for some independence of the flow direction of the reactants and the coolant in the turn region(s) 60 (shown in circular broken line), those back-to-back flow field plates 11 and 21 have been provided with a so-called mid-plane region 62 (shown in rectangular broken line) at the channel turn region(s) 60 of those plates. In this regard, in the mid-plane region(s) 62, the channeled structure of each of the flow field plates 11 and 21 transitions to a “mid-plane” configuration having an array of protrusions 64 and 64′ (in
Fuel cells and related assemblies involving directionally independent channels are provided. Performance and/or durability of a fuel cell stack are improved by using only traditional fluid flow channels in the active area. In this regard, an exemplary embodiment of a fuel cell stack comprises: a first fuel cell having channels associated with an anode; and a second fuel cell, located adjacent the first fuel cell, having channels associated with a cathode, the channels associated with the cathode exhibiting directional independence with respect to the channels associated with the anode. The channels may include reactant channels and coolant channels.
An exemplary embodiment of an assembly for use in a fuel cell stack comprises: a first plate, a second plate and a third plate, with the third plate being positioned between the first plate and the second plate, the third plate having an anode side facing the first plate and an opposing cathode side facing the second plate; the first plate defining fuel reactant channels on a side of the first plate facing away from the third plate and anode coolant channels on a side of the first plate facing the third plate; and the second plate defining oxidant reactant channels on a side of the second plate facing away from the third plate and cathode coolant channels on a side of the second plate facing the third plate. The first, second, and third plates have a mutually coincident active area. At least the first and second plates are typically stamped to form at least the channels therein.
In another embodiment having first, second and third plates, at least the first and second plates further include non-active manifold regions having associated mid-plane regions to provide fluid communication between respective manifolds and the reactant and coolant channels. The mid-plane regions are limited to substantially only non-active, manifold portions of the associated fluid flow plates, to thereby relatively improve the performance and/or durability of the fuel cell stack.
Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure.
Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts in the several views.
Fuel cells and related assemblies involving directionally independent channels are provided, exemplary embodiments of which will be described in detail. In this regard, some embodiments involve the use of three plates (e.g., stamped plates) to create reactant channels and coolant channels of adjacent fuel cells. The use of three plates enables the orientation of the fuel channels to be decoupled from the orientation of the oxidant channels, thus providing directional independence of the reactant channels. Additionally, in some embodiments, the coolant channels exhibit directional independence, in that a first set of the coolant channels turns with the fuel channels and a second set of the coolant channels turns with the oxidant channels. Further, such use of directionally independent channels enables mid-plane regions to be eliminated from the active regions of the fluid flow plates, and their use confined to the inactive inlet and/or outlet regions adjacent to the manifolds.
An exemplary embodiment of a fuel cell stack is partially depicted in the schematic diagram of
Adjacent to substrate 110 and opposing the membrane electrode assembly is an anode flow field plate structure 111 that serves as an electrically conductive electrode and includes an array 113 that serves as a fuel reactant flow field. The anode flow field plate structure 111 is formed typically by a stamping operation that defines an array of alternating ribs 114 and valleys, or channels, 116. Channels 116 are defined between the ribs 114. By way of example, each channel 116 of array 113 is defined by a pair of adjacent ribs 114, a corresponding channel wall 117 of the anode flow field plate structure 111, and a corresponding portion 119 of substrate 110. Notably, the channels of array 113 are anode channels, with the reactant or fuel of this embodiment that is provided to the anode channels being hydrogen or a hydrogen-rich gas.
Adjacent to substrate 112 and opposing the membrane electrode assembly is a cathode flow field plate structure 121 that serves as an electrically conductive electrode and includes an array 123 that serves as an oxidant reactant flow field. The cathode flow field plate structure 121 is formed typically by a stamping operation that defines an array of alternating ribs 124 and valleys, or channels, 128. Channels 128 are defined between the ribs 124. By way of example, each channel 128 of array 123 is defined by a pair of adjacent ribs 124, a corresponding channel wall 125 of the cathode flow field plate structure 121, and a corresponding portion 129 of substrate 112. In this embodiment, the channels 128 of array 123 are cathode channels with the reactant provided to the cathode channels being an oxidant, such as air.
Fuel cell 102 is positioned adjacent to fuel cell 101 and is structurally the same as fuel cell 101. Accordingly, the various elements of fuel cell 102 have the same reference numbers as their identical counterparts in fuel cell 101.
Important in the present disclosure is the provision of coolant channels formed by and in association with the anode flow field plate structure 111 and the cathode flow field plate structure 121, and the further provision of a separator member, or plate, intermediate the anode flow field plate structure 111 and the cathode flow field plate structure 121 to enable the fluid flow channels of the anode flow field plate structure 111 to exhibit or possess, directional independence with respect to the fluid flow channels of the cathode flow field plate structure 121. In this regard, a separator plate 150, typically of non-porous, electrically-conductive material, is located intermediate the anode flow field plate structure 111 and the cathode flow field plate structure 121 in mutual liquid sealing engagement with each, thereby forming a three-plate, fluid flow field assembly 152. The coolant is typically a liquid, such as water. The anode flow field plate structure 111 and the cathode flow field plate structure 121 are each stamped plates, typically of a metal alloy, for example stainless steel, and having a thickness of the order of 0.1 mm. The separator plate 150 may be similar to the anode flow field plate structure 111 and the cathode flow field plate structure 121, but may be flat throughout and need not be stamped.
Referring additionally to
By locating plate 150 between plates 111 and 121, the set of reactant and coolant channels located on one side of plate 150 can be oriented directionally independent of the set of reactant and coolant channels located on the other side of plate 150 without disturbing the coolant flow or flow distribution. Such a configuration is depicted schematically in
Referring to
As shown in
As an example of multi-pass flow, two discrete fluid paths are depicted in
Referring generally to
In operation, oxidant is provided to oxidant edge 376 of inlet 308 and coolant is provided to coolant edge 378. The mid-planed configuration of inlet 308 directs the oxidant from the oxidant edge to cathode channels (e.g., channel 328) located at the fluid transition edge 380, while directing coolant from the coolant edge to coolant channels 358, which run adjacent to the cathode channels 328 on the back of the cathode plate. Similarly, fuel is provided to fuel edge 382 of inlet 310 and coolant is provided to coolant edge 384. The mid-planed configuration of inlet 310 directs the fuel from the fuel edge to anode channels (e.g., channel 316) located at the fluid transition edge 386, while directing coolant from the coolant edge to coolant channels 356, which run adjacent to the anode channels on the back of the anode plate.
After flowing through the respective channels, outlet 312 receives the fuel and associated coolant at fluid transition edge 388 and directs the fluids via a mid-plane region to separate sides, or edges. Specifically, fuel is directed out through fuel edge 390 and coolant is directed out through coolant edge 392. Similarly, outlet 314 receives the oxidant and associated coolant at fluid transition edge 394, with the oxidant being directed out through oxidant edge 396 and coolant being directed out through coolant edge 398.
As shown in
Although the disclosure has been described and illustrated with respect to the exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made without departing from the spirit and scope of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US09/00020 | 1/5/2009 | WO | 00 | 4/29/2011 |