WO2003052847A2

WO2003052847A2 - Bipolar collector for proton membrane fuel cell

Info

Publication number: WO2003052847A2
Application number: PCT/FR2002/004380
Authority: WO
Inventors: Guy Bronoel; Serge Besse; Clément KIRRMANN
Original assignee: Sorapec
Priority date: 2001-12-18
Filing date: 2002-12-16
Publication date: 2003-06-26
Also published as: FR2833762A1; WO2003052847A3

Abstract

The invention concerns a proton membrane fuel cell characterized in that the bipolar manifolds are divided into several partitioned domains (10) having independent fluid supply and evacuation channels. The separating partitions (12) between the domains enable the passage of conduits for circulating the coolant (18). The connection between the different conduits linked to each domain and concerning a common type of fluid is provided by the end plates.

Description

COMPACT STRUCTURE FOR MEMBRANE FUEL CELL

PROTON

The invention relates to a proton membrane fuel cell characterized in that it comprises bipolar manifolds whose total thickness is very small (less than 3 mm) and constituted by a plurality of partitioned areas, each having the orifices of arrival and departure of reactive fluids; the parallel partitions separating these areas constitute the walls of the conduits where a heat transfer fluid circulates. The stack of elements constituting the cell is traversed perpendicularly by the supply and discharge conduits for the reactive fluids, for each partitioned area, and at least by an inlet conduit and a conduit for discharging the heat transfer fluid. The end plates of the fuel cell have the function of distributing each of the fluids, from a single inlet or outlet duct, to the ducts dedicated to these same fluids, perpendicularly crossing the entire stack of elements. .

The bipolar collectors described in most of the publications are all characterized by the supply of each element with reactive fluid through a single orifice (and likewise for the evacuation of the same fluid), the homogenization of the flow over the entire active surface of the electrodes being ensured by the circulation of fluids in channels or through specific obstacles, pawns or strands of open-cell foam.

Concerning the thermal management of the proton membrane elements, therefore of the proton membrane cell, several provisions have been proposed:

- several conduits are located in the middle part of the collector, the axis of the conduits being parallel to the plane of the electrodes, - cooling plates, supplied with fluid by holes in the stacking direction, are interposed between the elements of the battery, as mentioned in patent EP 0 959 511 (Toyota Motor),

- the cooling fluid circulates in a double wall surrounding the stack,

- conduits for circulation of the heat transfer fluid pass perpendicularly through the stack, including through the membrane and electrodes.

With regard to these various thermal management devices, all have drawbacks. In the case of conduits in the middle part of the manifold, this results in a relatively large thickness thereof. The use of cooling plates inserted between the elements of the stack results in increasing the thickness of the stack of the stack to combustible, which has the same effect as the above solution. The cooling in a double external wall requires, for its part, that at least one of the dimensions of the elements is not too high, therefore a very rectangular shape which, for power elements, will involve a great length, incompatible with certain applications. . The crossing of all the elements perpendicular to their surface poses serious sealing problems when this crossing is carried out through electrodes and membranes. The device described in patent JP 58 155664

(Hitachi Seisakusko KK) is different from the systems mentioned above but it applies to the case of molten salt cells, for which the heat exchanges are completely different from those encountered in proton membrane cells. The system described comprises conduits for circulation of the heat transfer fluid in each collector, but they open out on either side of the collectors; the mode of supply and evacuation of the heat transfer fluid in these conduits is not described.

With regard to the mode of supply of fluids at the level of each element, the very conventional design of the supply (or the evacuation) of the reagents from a single orifice poses the essential problem of the homogeneity of the flow. gas, over the entire surface of the electrode. In the case where one uses a single vein filled by a very open porous or localized contacts to drain the charges, it is necessary to have, at least at the entrance of each vein, a distributor whose pressure drop will allow the distribution of substantially equal gas flows over the entire surface. In the case where one would use a channel covering, in a pattern back and forth, the entire surface, this will result in a good homogenization of the flow at the cost of a high flow rate (to avoid any depletion effect) therefore an equally high pressure drop. In both cases, this results in a significant energy loss. Finally, note that the use of flow routing in several parallel channels effectively reduces the pressure drop but increases the risk of heterogeneity between the channels if one of the two is totally or partially obstructed. The device represented in patents EP 0 959 511 (Toyota Motor) and JP 58 155664 (Hitachi Seisakusho KK) makes it possible to improve the distribution of the reactive fluids, by decomposing the active surface of each cell element into several partitioned areas supplied by independent orifices.

The objective of the present invention is to eliminate, or at least limit, the extent of the aforementioned drawbacks by proposing a mode of thermal management at the level of each element, totally different from the conventional designs developed for fuel cells with protonic membrane. The invention also describes, for a stack of stack elements, the mode of distribution of the reactive gases and of the heat transfer fluid, carried out in the extreme plates of the fuel cell

At the level of each element, the active surface is broken down into several fluidly independent domains. Indeed, each domain, the width of which is essentially a function of the characteristics of the thermal conduction in the collector (thermal conductivity of the material constituting it, thickness) has a supply orifice for the reactive fluid at one of its ends and an orifice to the other end for its evacuation. As the width of the field does not generally exceed 75 mm, it follows that the homogenization of the reactive flows will be easier to achieve than if it had been, for example, the supply of an element whose width would have been 300 mm. The supply of reactive gases in these partitioned domains is carried out in parallel, which does not impose perfect sealing of the partitioned domains between them.

From the point of view of thermal management, the essential characteristic of the device resides in the fact that the duct, generally of circular or oblong shape, necessary for the circulation of the heat-transfer fluid, is placed partly in the separating partitions of the fluidly independent domains, partitions located on either side of the bipolar collector separating two neighboring elements, the electrodes coming to bear on the external surfaces of these partitions. When the number of fluidically independent domains is not too high (for example <6), the manifold may have a single inlet port and a single outlet port for the heat transfer fluid, each orifice being connected to a distribution duct. supplying each longitudinal duct placed in each partition. At the level of the entire stack, there will therefore be conduits situated at its two ends, conduits which pass through the entire stack perpendicular to the plane of the electrodes. The stack, as far as reactive fluids are concerned, will therefore be crossed at each of its ends by a number of conduits equal to twice the number of partitioned domains existing in an element. On the other hand, the number of conduits for the circulation of the heat transfer fluid may be, at each end, reduced to only one for a small number of areas, so as to centralize the distribution of this fluid and reduce the number of passages.

As a result, it is the end plates of the stack which include distributors making it possible to supply in an identical manner all the conduits allocated to a type of reagent from a single inlet connected to the outside.

The proton membrane fuel cell according to the invention is characterized by the use of bipolar manifolds whose total thickness is very small (less than 3 mm) but which comprise nevertheless a network of parallel conduits located in partitions whose thickness is equal to that of the collectors; these conduits allow the circulation of a heat transfer fluid in order to ensure good thermal management of the system.

The stack of elements constituting the proton membrane fuel cell according to the invention is crossed perpendicularly on two of its sides by as many supply or discharge conduits in reactive fluids as there are partitioned domains, and by one or more conduits ensuring the arrival and evacuation of the heat transfer fluid.

The end plates of the fuel cell with a pro tonic membrane according to the invention have the function of distributing, from a single inlet or outlet duct, each of the fluids towards the ducts dedicated to these same fluids passing through. perpendicularly the entire stack of elements. To this end, each plate limiting the two ends of the stack of the proton membrane fuel cell according to the invention has three main conduits connected to the outside and dedicated to each type of fluid (fuel, oxidizer and coolant) and comprises, moreover, the arrival of all the conduits passing through the stack, two or three distribution ramps connecting the main conduits to each type of fluid.

The bipolar collectors used in the proton membrane fuel cell according to the invention are made of a composite material, for example a polymer-carbon composite, the electrical conductivity of which is greater than 10 S.cm ^"1 and the thermal conductivity greater than 10 Wm '.K ¹ .

According to another characteristic of the invention, the distance between the conduits for circulation of the heat transfer fluid, that is to say the width of the partitioned areas, is between 25 and 75 mm. The number of partitioned domains is between 2 and 10.

According to the invention, the conduits for circulation of the heat-transfer fluid have a circular or oblong section, with an area of between 0.5 and 3 mm ² in the case of a circular-shaped conduit and between 1 and 5 mm ² in the case of an oblong duct.

According to the present invention, the space between two partitions integrating the conduits for the circulation of the coolant comprises channels or pins made of the same material as the manifold; these channels or these pions ensure the circulation of reactive or reacted species. The circulation space of reactive or reacted species is always less than 1.5 mm. The function of this network of channels or pins is, on the one hand, to ensure the homogenization of the flows circulating in each of them, the upper faces of the channels or pins serving as support for the electrodes and, on the other hand apart, to transmit the electrical charges and the heat from the electrodes to the central part of the collector. The thickness of the space allocated to the circulation of reactive or reacted species is defined so as to ensure a sufficient gas flow at the electrodes in order to reach the maximum power required from the cell, while ensuring, on the cathode side , the departure of the water formed. Thus, the thickness of this space will advantageously be greater on the cathode side than on the anode side; for example, the thickness of the anode side may be close to 1 mm, while the space on the cathode side will rather have a thickness close to 1.5 mm. It should be noted that the use of channels or pins does not constitute an innovation, these means being already described for fuel cells.

According to the invention, the partitions integrating the conduits for circulation of the heat-transfer fluid have a height equal to the height of the stream in which the reactive fluids circulate, the electrodes being pressed on the upper face of these partitions.

The invention and its various characteristics are illustrated in FIGS. 1 to 6:

FIG. 1 is a view of a bipolar collector used in the proton membrane fuel cell according to the invention, this collector being represented on the fuel supply side,

FIG. 2 is a view of a bipolar collector used in the proton membrane fuel cell according to the invention, this collector being represented on the oxidant supply side,

FIG. 3a represents the sectional view of the manifold along a median axis, FIG. 3b represents the detail of the sectional view of FIG. 3a,

FIG. 4 represents a mode of distribution of the heat transfer fluid in a bipolar collector according to the invention, the distribution being, in this case, ensured by an inlet and an outlet by cooling channel,

- Figure 5a shows the distribution channels and distribution of fluids in an end plate of the stack constituting the proton membrane fuel cell

(front view),

FIG. 5b represents the distribution and distribution channels for the fluids in an end plate of the stack constituting the proton membrane fuel cell (side view), - Figure 6 shows another mode of distribution of the heat transfer fluid in a bipolar collector, the distribution circuit being, in this case, centralized on a single inlet pipe and a single outlet pipe of the heat transfer fluid.

Example of realization

A proton membrane fuel cell constituted by the stack of 36 elements was produced according to the characteristics described. Each cell element has a manifold (1) as shown in Figure 1 for the fuel side (eg H ^ and in Figure 2 for the oxidant side (eg OJ. The manifolds shown in Figures 1 and 2 have, in the upper part, fuel (2) and oxidant (3) supply orifices and, in the lower part, discharge orifices (4) and (5), respectively for the same reactive gases. two figures also appear the orifices for supplying (6) and evacuating (7) the heat transfer fluid. The bipolar collector shown in these two figures comprises 5 partitioned areas, separated by a conduit for circulation of the heat transfer fluid (8), represented in FIGS. 3a and 3b In these same figures, the partitions (12) and the pins (9) which delimit the circulation veins (10) of the reactive fluids are represented. The electrodes used in the stack are placed on both sides of the collection ur and rest on the pins (9). These pins are made of the same material as that used for the core (11) of the bipolar collector. These pins provide electrical contact between the bipolar collector and the electrodes, as well as the transmission of heat from the electrode to the cooling circuits. The material used in this exemplary embodiment is a PVDF-carbon composite, the electrical conductivity of which is 25 S.cm ^"1 and the thermal conductivity of 25 Wm- \ K- \

FIG. 4 represents the circuit of the heat transfer fluid in the bipolar collector according to an embodiment characterized by a completely separate distribution, each conduit (8) comprising an inlet (13) and an outlet (14) of the heat transfer fluid. The central axis of the coolant circulation conduits is located at the intersection between the plane passing through the middle of the thickness of the manifold and the plane which is perpendicular thereto passing through the middle of each partition.

FIGS. 5a and 5b show the conduits for distributing and distributing the fluids in an end plate of the stack, in the case of a lateral connection of the fluids arrivals. The arrival of the heat transfer fluid is ensured by the conduit (15) and its evacuation by the conduit (16); the conduits (17) and (18) ensure the arrival and evacuation of the hydrogen, while the conduits (19) and (20) allow the supply and the evacuation of the oxygen. The oblique passages (21) between the rectangular distribution openings (22) and the distribution clarinets (18) allow these clarinets to be shifted towards the axis of the proton membrane fuel cell. The oxidizing drainage clarinet (oxygen or air) can be placed near the bottom edge, so as to take advantage of a gravity effect favorable to the flow of the water formed. These end plates can be made of a non-conductive material on condition of interposing current collector plates between these plates and the mono-polar end plates.

The invention is not limited to the embodiment described but embraces all the variants. One of these variants is represented in FIG. 6 which represents the circuit of the heat transfer fluid in the bipolar collector when the distribution of this fluid is centralized. In this case, the manifold (1) has only one inlet duct (23) and a single outlet duct (24).

Claims

1 - Protonic membrane fuel cell characterized in that it comprises one or more bipolar manifolds whose total thickness is very small - less than 3 mm - but which nevertheless include a network of parallel conduits located in partitions whose thickness is that of the coËectors, said conduits allowing the circulation of a heat-transfer fluid to ensure good thermal management of the system.

2 - Protonic membrane fuel cell according to claim 1, characterized in that the material constituting the bipolar collector (s) is a composite material whose electrical conductivity is greater than 10 S.cm ^"1 and the thermal conductivity greater than 10 Wm '.K ^"1 .

3 - Protonic membrane fuel cell according to claim 1, characterized in that the distance between the conduits which comprise the bipolar collector (s) for ensuring the circulation of the heat-transfer fluid is between 25 and 75 mm, the section of a conduit , circular in shape with an area between 0.5 and 3 mm ² .

4 - Fuel cell with pro tonic membrane according to claim 1, characterized in that the distance between the conduits which comprise the two-pole manifold (s) for ensuring the circulation of the heat-transfer fluid is between 25 and 75 mm, the section of a duct, oblong, with an area between 1 and 5 mm ² .

5 - Protonic membrane fuel cell according to claim 1, characterized in that the space between two partitions integrating the conduits for the circulation of the heat-transfer fluid comprises channels or pins made of the same material as the rest of the collector, these channels or these pins ensuring the circulation of reactive or reacted species as well as possible, this circulation space always having a thickness of less than 1.5 mm.

6 - Protonic membrane fuel cell according to claim 1, characterized in that the partitions integrating the conduits have a height equal to the height of the vein where the reactive fluids circulate, the electrodes being pressed on the upper face of these partitions. 7 - Protonic membrane fuel cell according to claim 1, characterized in that the stack of elements constituting the cell is crossed perpendicularly on two of its sides by as many supply or discharge conduits in reactive fluids as there are partitioned areas and by one or more conduits ensuring supply and evacuation of the heat transfer fluid.

8 - Protonic membrane fuel cell according to claim 1, characterized in that each plate limiting the two ends of the stack has three main conduits connected to the outside and dedicated to each type of fluid (fuel, oxidizer, coolant) and also includes the arrival of all the conduits passing through the stack, two or three distribution ramps connecting the main conduits to each type of fluid.