BIPOLAR PLATE FOR AN ELECTROCHEMICAL REACTOR

Abstract

A bipolar plate for an electrochemical reactor, including at least one anode sheet and one cathode sheet, each having an internal face and an external face, the anode and cathode sheets being in contact with each other via their internal face, each anode and cathode sheet including, on its external face, channels for circulating reactive fluids, the channels demarcating, at the internal faces of the anode and cathode sheets, cooling pipes for a flow of a heat transfer fluid, the channels of the anode and cathode sheets including alternating bosses and indentations, the bosses of the anode sheet being arranged in a staggered manner and the bosses of the cathode sheet being arranged in a staggered manner.

Claims

1. A bipolar plate for an electrochemical reactor, comprising at least one anode sheet and one cathode sheet, each having an internal face and an external face, the anode and cathode sheets being in contact with each other via their internal face, each anode and cathode sheet comprising, on its external face, channels for circulating reactive fluids, the channels demarcating, at the internal faces of the anode and cathode sheets, cooling pipes for a flow of a heat transfer fluid, the channels of the anode and cathode sheets comprising alternating bosses and indentations, the bosses of the anode sheet being arranged in a staggered manner and the bosses of the cathode sheet being arranged in a staggered manner.

2. The bipolar plate as claimed in claim 1, the bosses of the anode sheet being arranged in a staggered manner in relation to the bosses of the cathode sheet.

3. The bipolar plate as claimed in claim 1, at least one boss of the anode sheet being in contact with at least one boss of the cathode sheet.

4. The bipolar plate as claimed in claim 1, at least one boss of the cathode sheet being in contact with at least one boss of the anode sheet.

5. The bipolar plate as claimed in claim 1, the bosses of the anode sheet being in contact with at least one boss of the cathode sheet over at least 75% of their total length.

6. The bipolar plate as claimed in claim 1, the anode sheet and the cathode sheet each comprising patterns formed by a consecutive boss and indentation in the same channel, the patterns of the anode sheet all having a first length and the patterns of the cathode sheet all having a second length.

7. The bipolar plate as claimed in claim 6, the first length being different from the second length.

8. The bipolar plate as claimed in claim 7, the first length being greater than the second length.

9. The bipolar plate as claimed in claim 6, the ratio of the first to the second length being a substantially integer ratio.

10. The bipolar plate as claimed in claim 9, the ratio of the first to the second length being an even integer ratio.

11. The bipolar plate as claimed in claim 10, the ratio of the first to the second length being equal to 2 or to 4.

12. The bipolar plate as claimed in claim 1, the length of at least one indentation of the anode sheet and/or of the cathode sheet being less than the length of at least one boss of the sheet.

13. The bipolar plate as claimed in claim 1, the length of at least one indentation of the anode and/or cathode sheet being equal to the length of the bosses.

14. The bipolar plate as claimed in claim 1, the channels comprising curved portions.

15. The bipolar plate as claimed in claim 14, the channels and/or the bosses being obtained by stamping or hydroforming anode and/or cathode sheets.

16. An electrochemical reactor comprising: a bipolar plate as claimed in claim 1; a membrane-electrode assembly, at least one of the electrodes of which is in contact with the anode sheet or the cathode sheet of the bipolar plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The invention will be better understood upon reading the following description of non-limiting embodiments thereof, and with reference to the accompanying drawings, in which:

[0069] FIG. 1a is a schematic and partial top view of a cathode sheet according to the prior art;

[0070] FIG. 1b is a schematic and partial top view of an anode sheet according to the prior art;

[0071] FIG. 1c is a schematic and partial top view of a cooling circuit provided between the two sheets of FIGS. 1a and 1b;

[0072] FIG. 2a is a schematic perspective view of a cathode sheet according to the invention;

[0073] FIG. 2b is a schematic perspective view of an anode sheet according to the invention;

[0074] FIG. 2c is a schematic and partial top view of a cooling circuit provided between the two sheets of FIGS. 2a and 2b;

[0075] FIG. 3a is a view similar to FIG. 2c of an alternative embodiment;

[0076] FIG. 3b is a view similar to FIG. 2c of an alternative embodiment;

[0077] FIG. 3c is a view similar to FIG. 2c of an alternative embodiment;

[0078] FIG. 4a is a view similar to FIG. 2b of an alternative embodiment;

[0079] FIG. 4b is a view similar to FIG. 2a of an alternative embodiment; and

[0080] FIG. 4c is a schematic and partial top view of a cooling circuit provided between the two sheets of FIGS. 4a and 4b.

DETAILED DESCRIPTION

[0081] In the figures and throughout the remainder of the description, the same reference signs represent identical or similar elements.

[0082] FIGS. 2a and 2b show an example of a cathode sheet Tc and an anode sheet Ta according to the invention. These sheets Tc, Ta each comprise an external face 101 and an internal face 102. In the case of the cathode sheet Tc, the external face 101 is intended to be in contact with a cathode of the electrochemical reactor. In the case of the anode sheet Ta, the external face 101 is intended to be in contact with an anode of the electrochemical reactor. These sheets Tc, Ta are made from a metallic material that can be shaped.

[0083] The cathode sheet Tc comprises channels Cc1, Cc2, Cc3, Cc4, which substantially extend along a longitudinal axis X and the anode sheet Ta comprises channels Ca1, Ca2, Ca3, Ca4, which substantially extend along the longitudinal axis X. All the channels Cc1, Cc2, Cc3, Cc4, Ca1, Ca2, Ca3, Ca4 have the same width e, which is substantially constant along the longitudinal axis X.

[0084] The channels Cc1, Cc2, Cc3, Cc4 together form ribs Nc1, Nc2, Nc3, Nc4. The channels Ca1, Ca2, Ca3, Ca4 together form ribs Na1, Na2, Na3, Na4. In the embodiment shown, the ribs Nc1, Nc2, Nc3, Nc4, Na1, Na2, Na3, Na4 comprise a substantially flat top 10. These ribs Nc1, Nc2, Nc3, Nc4, Na1, Na2, Na3, Na4 substantially extend along the longitudinal axis X and have a constant cross-section, taken perpendicular to the longitudinal axis X. The thickness of a rib Nc1, Nc2, Nc3, Nc4 corresponds to the distance d between two consecutive channels Cc1, Cc2, Cc3, Cc4. The thickness of a rib Na1, Na2, Na3, Na4, corresponds to the distance d between two consecutive channels Cc1, Ca1, Ca2, Ca3, Ca4. The width e of the channels is equal to the distance d between two channels.

[0085] All the channels of the two sheets Cc1, Cc2, Cc3, Cc4, Ca1, Ca2, Ca3, Ca4 comprise alternating bosses Bc, Ba and indentations Ec, Ea.

[0086] In the embodiment of the prior art, the cathode sheet Tc, which is schematically shown in FIG. 1a, comprises channels Cc1, Cc2, Cc3, Cc4, which comprise alternating bosses Bc and indentations Ec that are aligned, and the anode sheet Ta, which is schematically shown in FIG. 1b, comprises channels Ca1, Ca2, Ca3, Ca4, which comprise alternating bosses Ba and indentations Ea that are arranged in a staggered manner. The cooling circuit that is provided between these two plates is schematically shown in FIG. 1c. The heat transfer fluid flows through the pipes 20 that are formed by the series of anode Ba and cathode Bc bosses.

[0087] On the sheets according to the invention, shown in FIGS. 2a and 2b, the cathode bosses Bc and the cathode indentations Ec are arranged in a staggered manner and the anode bosses Ba and the anode indentations Ea are also arranged in a staggered manner. For example, on the cathode sheet Tc a boss in the channel Cc2 is opposite an indentation in the channel Cc1 and an indentation in the channel Cc2 when the sheet is viewed along the transverse axis Y. Similarly, on the anode sheet Ta, a boss in the channel Ca2 is opposite an indentation in the channel Ca1 and an indentation in the channel Ca2 when the sheet is viewed along the transverse axis Y. A boss in a channel therefore is at the same level as an indentation of an adjacent channel.

[0088] In order to form an electrochemical reactor according to the invention, the two sheets Ta, Tc are superimposed by stacking the anode sheet Ta on the cathode sheet Tc. The internal faces 102 of the two sheets are brought into contact. The channels Ca1, Ca2, Ca3, Ca4 of the anode sheet Ta are offset along the lateral axis Y in relation to the channels Cc1, Cc2, Cc3, Cc4 of the cathode sheet Tc by a distance d.

[0089] Thus, the channel of one sheet inserts into the rib of the other sheet. For example, the rib Nc1 inserts into the channel Ca4, the rib Nc2 inserts into the channel Ca3, the rib Nc3 inserts into the channel Ca2, the rib Nc4 inserts into the channel Ca1, and so on over the entire width of the sheets. Similarly, the rib Na1 inserts into the channel Cc4, the rib Na2 inserts into the channel Cc3, the rib Na3 inserts into the channel Cc2, the rib Na4 inserts into the channel Cc1, and so on over the entire width of the sheets. The two sheets Tc, Ta are thus partially interlocked. This partial interlocking allows the spatial requirement of the bipolar plate to be reduced.

[0090] The bosses of the anode sheet Ba can be offset along the longitudinal axis X in relation to the bosses of the cathode sheet Bc. The bosses of the anode sheet Ba are offset along the lateral axis Y in relation to the bosses of the cathode sheet Bc, since the channels Ca1, Ca2, Ca3, Ca4 of the anode sheet Ta are offset along the lateral axis Yin relation to the channels Cc1, Cc2, Cc3, Cc4 of the cathode sheet Tc. At least some of the bosses Ba of the anode sheet Ta are thus arranged in a staggered manner in relation to the bosses Bc of the cathode sheet Tc.

[0091] The staggered arrangement of the bosses of the anode sheet Ba in relation to the bosses of the cathode sheet Bc allows, when the two sheets are superimposed, the cooling pipes 20 shown in FIG. 2c to be provided. The zones 21 between the cooling pipes 20 are zones where the heat transfer fluid does not flow. A cooling circuit is thus formed between the sheets Ta, Tc. The heat transfer fluid successively circulates from a boss Ba of a channel Ca1, Ca2, Ca3, Ca4 of the anode sheet to a boss Bc of a channel Cc1, Cc2, Cc3, Cc4 of the cathode sheet, and then again to a boss of Ca1′, Ca2′. As these bosses Ba, Bc are staggered, the heat transfer fluid can thus progress along the longitudinal axis X. The staggered arrangement of the bosses allows the heat transfer fluid to flow continuously along the longitudinal axis X, by transitioning from an anode boss to a cathode boss and vice versa. In the example shown in FIG. 2c, the heat transfer fluid flows along a line L that comprises curved portions. In this example, each boss of the anode sheet Ba is in contact with three bosses of the cathode sheet Bc.

[0092] A pattern of the anode sheet corresponds to a consecutive boss Ba and indentation Ea in the same channel. A pattern of the cathode sheet corresponds to a consecutive boss Bc and indentation Ec in the same channel. The patterns of the anode sheet are all the same length l.sub.a and the patterns of the cathode sheet are all the same length l.sub.c. In the embodiment shown in FIGS. 2a, 2b, 2c, the length l.sub.a of the patterns of the anode sheet is greater than the length l.sub.c of the patterns of the cathode sheet. In this example, the ratio of the length l.sub.a of the anode patterns to the length l.sub.c of the cathode patterns is substantially equal to 2.

[0093] This difference in length, combined with the staggered arrangement of the bosses of one sheet in relation to the other, allows a cooling circuit to be created in which the restrictions of the flow of the cooling fluid are reduced. In particular, the cross-section provided for the flow of the heat transfer fluid is at least equal to the width of two channels, that is a width that is equal to 2e. In some locations, the cross-section provided for the flow of the heat transfer fluid is equal to the width of three channels, that is a width that is equal to 3e.

[0094] FIG. 3a shows the cooling circuit obtained by superimposing an anode sheet Ta and a cathode sheet Tc, which comprise bosses arranged in a staggered manner, and for which the ratio of the lengths of the patterns is substantially equal to 1.

[0095] FIG. 3b shows the cooling circuit obtained by superimposing an anode sheet Ta and a cathode sheet Tc, which comprise bosses arranged in a staggered manner, and for which the ratio of the lengths of the patterns is substantially equal to 3.

[0096] FIG. 3c shows the cooling circuit obtained by superimposing an anode sheet Ta and a cathode sheet Tc, which comprise bosses arranged in a staggered manner, and for which the ratio of the lengths of the patterns is substantially equal to 4.

[0097] When the ratio of the length l.sub.a of the bosses of the anode sheet to the length l.sub.c of the bosses of the cathode sheet is odd, as shown in FIGS. 3a and 3b, the flow direction D of the heat transfer fluid is inclined by an angle of inclination α in relation to the longitudinal axis X. The angle of inclination α can range between 2 and 45°, preferably between 5 and 30°, preferably between 10 and 20°, for example, of the order of 15°. In this case, the heat transfer fluid may need to be supplied and collected through the sides of the anode and cathode sheets.

[0098] When the ratio of the length l.sub.a of the patterns of the anode sheet to the length l.sub.c of the patterns of the cathode sheet is even, as shown in FIGS. 2c and 3c, the flow direction D is substantially parallel to the longitudinal axis X.

[0099] FIGS. 4a and 4b show the anode Ta and cathode Tc sheets of an alternative embodiment of the invention. In this alternative embodiment, the channels Ca1, Ca2, Ca3, Ca4, Cc1, Cc2, Cc3, Cc4 do not extend along a longitudinal axis X. In this embodiment, the channels Ca1, Ca2, Ca3, Ca4 of the anode sheet Ta comprise alternating straight portions 30 and curved portions 31. Also in this embodiment, the channels Cc1, Cc2, Cc3, Cc4 of the cathode sheet Tc comprise alternating straight portions 30′ and curved portions 31′. The curved portions 31 of the channels of the anode sheet Ta have the same curvature as the curved portions 31′ of the channels of the cathode sheet Tc. The straight portions 30 of the channels of the anode sheet Ta are parallel to the straight portions 30′ of the channels of the cathode sheet Tc. Thus, the channels of the cathode sheet Cc1, Cc2, Cc3, Cc4 follow the channels of the anode sheet Ca1, Ca2, Ca3, Ca4.

[0100] In this embodiment, the length of the anode bosses Ba is greater than the length of the cathode bosses Bc.

[0101] In the same way as in the embodiment of FIGS. 2a and 2b, in order to form an electrochemical reactor according to the invention, the two sheets Ta, Tc are superimposed by stacking the anode sheet Ta on the cathode sheet Tc and by bringing the internal faces 102 of the two sheets into contact.

[0102] The cooling circuit provided between the anode sheet Ta of FIG. 4a and the cathode sheet Tc of FIG. 4b is shown in FIG. 4c. This cooling circuit allows a flow direction D to be obtained that substantially extends along the longitudinal axis X. Such sheets with curved portions 31, 31′ allow the ripples in the flow of the heat transfer fluid to be reduced that can be present, for example, in the embodiment of FIG. 2c. Such a flow that substantially extends along the longitudinal axis X particularly allows the pressure drop in the cooling channels to be reduced further.