Bipolar plate which has reactant gas channels with variable cross-sectional areas, fuel cell stack, and vehicle comprising such a fuel cell stack

Abstract

The invention relates to a bipolar plate for a fuel cell, comprising an anode plate with anode gas channels and a cathode plate with cathode gas channels, said plates having an active region and supply regions and being arranged one over the other such that the gas channels form coolant channels. The aim of the invention is to improve such a bipolar plate such that the flow conditions of reactants and coolant in the bipolar plate are optimized. This is achieved in that the height and/or the width of the cathode gas channels increase(s) from a first side of the active region to a second side of the active region, and the height and/or the width of the anode gas channels decrease(s) from the first side of the active region to the second side of the active region, wherein the cross-sectional area and/or the hydraulic diameter of the cathode gas channels increases, and the cross-sectional area and/or the hydraulic diameter of the anode gas channels decreases. The invention additionally relates to a fuel cell stack and to a vehicle.

Claims

1. A bipolar plate for a fuel-cell, comprising: an anode plate; a cathode plate; an active area; two supply areas for supply and discharge of operating media to or from the active area, each of the two supply areas having: an anode gas port for supplying or discharging fuel; a cathode gas port for supplying or discharging oxidant; and a coolant port for supplying or discharging coolant; and wherein: the anode plate includes anode gas channels; the cathode plate includes cathode gas channels, each of the anode gas channels and the cathode gas channels have open channel structures and are arranged above one another, and the anode plate and the cathode plate are on adjacent sides and form coolant channels which connect coolant inlets of the two supply areas; a height or a width of the cathode gas channels of a first side of the active area increases toward a second side of the active area; a height or a width of the anode gas channels of the first side of the active area decreases in a direction of flow toward the second side of the active area; a cross-sectional area of the cathode gas channels increases; a cross-sectional area of the anode gas channels decreases; and a partial cross-sectional area or a hydraulic partial diameter of coolant sub-channels formed in the anode plate increases from the first side of the active area to the second side of the active area, and a partial cross-sectional area or a hydraulic partial diameter of coolant sub-channels formed in the cathode plate decreases from the first side of the active area to the second side of the active area.

2. The bipolar plate according to claim 1 wherein the bipolar plate is rectangular.

3. The bipolar plate according to claim 1 wherein mutually-opposing sides of the anode plate and the cathode plate are plano-parallel to each other.

4. The bipolar plate according to claim 1 wherein at least one of mutually-facing sides of the anode plate and the cathode plate are plano-parallel to each other or mutually-opposing sides of the anode plate and the cathode plate are plano-parallel to each other.

5. The bipolar plate according to claim 1 wherein a cross-sectional area or a hydraulic diameter of the coolant channels in the active area is constant.

6. The bipolar plate according to claim 3 wherein a cross-sectional area or a hydraulic diameter of the coolant channels is constant along the active area.

7. The bipolar plate according to claim 1 wherein the coolant channels extend parallel to surfaces of the anode gas channels and parallel to surfaces of the cathode gas channels.

8. The bipolar plate according to claim 1 wherein a surface of the anode plate engaged with the cathode plate and a surface of the cathode plate engaged with the anode plate each extend in a direction parallel to surfaces of the anode gas channels and parallel to surfaces of the cathode gas channels.

9. The bipolar plate according to claim 1 wherein the coolant channels extend parallel to a surface of the anode plate engaged with the cathode plate and parallel to a surface of the cathode plate engaged with the anode plate.

10. A fuel-cell stack, comprising: at least one bipolar plate, the bipolar plate including: an anode plate; a cathode plate; an active area; two supply areas for supply and discharge of operating media to or from the active area, each of the two supply areas having: an anode gas port for supplying or discharging fuel; a cathode gas port for supplying or discharging oxidant; and a coolant port for supplying or discharging coolant; and wherein: the anode plate includes anode gas channels; the cathode plate includes cathode gas channels, each of the anode gas channels and the cathode gas channels have open channel structures and are arranged above one another, and the anode plate and the cathode plate are on adjacent sides and form coolant channels which connect coolant inlets of the two supply areas; a height or a width of the cathode gas channels of a first side of the active area increases toward a second side of the active area; a height or a width of the anode gas channels of the first side of the active area decreases toward the second side of the active area; a cross-sectional area of the cathode gas channels increases; a cross-sectional area of the anode gas channels decreases; and a partial cross-sectional area of coolant sub-channels formed in the anode plate increases from the first side of the active area to the second side of the active area, and a partial cross-sectional area of coolant sub-channels formed in the cathode plate decreases from the first side of the active area to the second side of the active area.

11. The fuel-cell stack according to claim 10 wherein a cross-sectional area of the coolant channels in the active area is constant.

12. The fuel cell according to claim 10 wherein a hydraulic diameter of the cathode gas channels increases and a hydraulic diameter of the anode gas channels decreases.

13. A vehicle, comprising: a fuel-cell system, including a fuel-cell stack, the fuel-cell stack having: at least one bipolar plate including: an active area having a first side and a second side; an anode plate having anode gas channels; and a cathode plate having cathode gas channels, the cathode plate positioned adjacent to the anode plate to locate each of the anode gas channels adjacent to a corresponding cathode gas channel, each of the anode gas channels and the cathode gas channels positioned within the active area of the at least one bipolar plate; wherein a depth and a cross-sectional area of the anode gas channels each taper between the first side of the active area and the second side of the active area in a first direction; wherein a depth and a cross-sectional area of the cathode gas channels each taper between the first side of the active area and the second side of the active area in a second direction that is opposite to the first direction; wherein coolant channels are formed by a first portion of the coolant channels disposed in the anode plate and a second portion of the coolant channels disposed in the cathode plate; and wherein a partial cross-sectional area or a hydraulic partial diameter of coolant sub-channels formed in the anode plate increases from the first side of the active area to the second side of the active area, and a partial cross-sectional area or a hydraulic partial diameter of coolant sub-channels formed in the cathode plate decreases from the first side of the active area to the second side of the active area.

14. The vehicle according to claim 13 wherein a cross-sectional area of the coolant channels in the active area is constant.

15. The vehicle according to claim 13 wherein at least one of mutually-facing sides of the anode plate and the cathode plate are plano-parallel to each other or mutually-opposing sides of the anode plate and the cathode plate are plano-parallel to each other.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention is explained below in exemplary embodiments in reference to the respective drawings. The following are shown:

(2) FIG. 1 is a top view of a bipolar plate;

(3) FIG. 2 is a sectional view (C-C) in the longitudinal direction of a bipolar plate according to the invention according to a first embodiment, which is arranged between two membrane electrode units;

(4) FIG. 3 is a sectional view (A-A) in the transverse direction of the bipolar plate according to FIG. 2;

(5) FIG. 4 is a sectional view (B-B) in the transverse direction of a bipolar plate according to FIG. 2;

(6) FIG. 5 is a sectional view (A-A) in the transverse direction of the bipolar plate according to FIG. 2;

(7) FIG. 6 is a sectional view (B-B) in the transverse direction of the bipolar plate according to FIG. 2;

(8) FIG. 7 is a sectional view (C-C) in the longitudinal direction of a bipolar plate according to the invention according to a second embodiment, which is arranged between two membrane electrode units;

(9) FIG. 8 is a sectional view (A-A) in the transverse direction of the bipolar plate according to FIG. 7;

(10) FIG. 9 is a sectional view (B-B) in the transverse direction of a bipolar plate according to FIG. 7;

(11) FIG. 10 is a sectional view (A-A) in the transverse direction of the bipolar plate according to FIG. 7;

(12) FIG. 11 is a sectional view (B-B) in the transverse direction of the bipolar plate according to FIG. 7;

(13) FIG. 12 is a sectional view (C-C) in the longitudinal direction of a bipolar plate according to the invention according to a third embodiment, which is arranged between two membrane electrode units;

(14) FIG. 13 is a sectional view (A-A) in the transverse direction of the bipolar plate according to FIG. 12;

(15) FIG. 14 is a sectional view (B-B) in the transverse direction of a bipolar plate according to FIG. 12;

(16) FIG. 15 is a sectional view (A-A) in the transverse direction of a bipolar plate according to a fourth, and

(17) FIG. 16 is a sectional view (B-B) in the transverse direction of the bipolar plate according to a fourth FIG. 12.

DETAILED DESCRIPTION

(18) FIG. 1 shows a top view of rectangular bipolar plate 10 according to the invention.

(19) The bipolar plate 10 is divided into an active area AA and inactive areas IA. The active area AA is characterized in that the fuel-cell reactions take place in this area. The inactive areas IA can in each case be divided into supply areas SA and distribution areas DA, wherein the distribution areas DA connect the supply areas SA to the active area AA.

(20) An anode inlet opening 11 for supplying the anode gas, i.e., the fuel, e.g., hydrogen, is provided within a supply area SA. The anode outlet opening 12 in the other supply area SA is used for discharging the anode exhaust gas after overflowing the active area AA. The cathode inlet opening 13 in the first supply area SA is used for supplying the cathode gas, which is, in particular, oxygen or an oxygen-containing mixture—preferably, air. The cathode outlet opening 14 is used for discharging the cathode gas after overflowing the active area AA in the other supply area SA. The coolant inlet opening 15 is used for supplying and the coolant outlet opening 16 is used for discharging the coolant in the various supply areas SA.

(21) The bipolar plate 10 shown in FIG. 1 has a cathode side 17 that is visible in the illustration and also an anode side 18 that is not visible, wherein the bipolar plate 10 is constructed from an anode plate 19 and a cathode plate 20, which are joined to each other. On the cathode side 17 illustrated, cathode gas channels 21 are formed as open, groove-like channel structures which connect the cathode inlet opening 13 to the cathode outlet opening 14. Similarly, the anode side 18 (not visible here) has corresponding anode gas channels 22 which connect the anode inlet opening 11 to the anode outlet opening 12. The anode gas channels 22 also take the form of open, groove-like channel structures. Enclosed coolant channels 23 run within the interior of the bipolar plate 10, between the anode plate 19 and the cathode plate 20, and connect the coolant inlet opening 15 to the coolant outlet opening 16. The dashed lines in FIG. 1 indicate seals 24.

(22) FIG. 2 shows a bipolar plate 10 according to FIG. 1 in a longitudinal section C-C, the course of which is shown in FIG. 3. FIGS. 3 and 4 show cross-sections A-A and B-B of the bipolar plate 10, showing, respectively, the first side 26 (inlet side) and the second side 27 (outlet side) of the active area AA of the bipolar plate 10.

(23) Membrane electrode units 25 are arranged on the cathode side 17 and also on the anode side 18 of the bipolar plate 10. The anode gas channels 22, the cathode gas channels 21, and the coolant channels 23 extend, as already explained for FIG. 1, over the active area AA from a first side 26 of the active area AA to a second side 27 of the active area AA, wherein the coolant channels 23 are formed from coolant subchannels 23a, 23b in the anode plate 19 and the cathode plate 20. The profiled sides of the anode and cathode plates 19, 20, as well as their mutually-facing sides 28, 29, into which the coolant subchannels 23a, 23b are incorporated, are piano-parallel in form.

(24) The height H of the anode gas channels 22 decreases from the first side 26 to the second side 27 of the active area AA. In contrast, the height H of the cathode gas channels 21 increases from the first side 26 to the second side 27 of the active area AA. The coolant channels 23, on the other hand, extend over the active area AA with a constant cross-sectional area and/or a constant hydraulic diameter, wherein the distance from the anode and cathode gas channels 21, 22 remains constant, and wherein the coolant subchannels 23a in the anode plate 19 have an increasing partial cross-sectional area and/or a hydraulic partial diameter. In the case of the cathode plate 20, this is formed in exactly the opposite way.

(25) FIGS. 5 and 6 represent a slightly varied embodiment of the bipolar plate according to FIGS. 2 through 4 and once again show cross-sections A-A and B-B, which show, respectively, the first side 26 (inlet side) and the second side 27 (outlet side) of the active area AA, but without any membrane electrode units being shown here. For facilitating manufacturability, the anode gas channels 22 and the cathode gas channels 21, and also the coolant channels 23, are not made to be rectangular, but instead have a trough-like design with flank angles of less than 90°. In addition, in this embodiment, the coolant subchannels 23a in the anode or cathode plate 19, 20 have widths B differing from each other. In the area of the first side 26 of the active area AA, the coolant subchannels 23a are narrower in the anode plate 19 than in the cathode plate 20. The reverse is true in the area of the second side 27, and the coolant subchannels 23a are narrower in the cathode plate 20 than in the anode plate 19. Between the first and second sides 26, 27, there is of course an area in which both coolant subchannels 23a, 23b have the same width B.

(26) FIG. 7 also shows a bipolar plate 10 in a longitudinal section C-C, whose course is shown in FIG. 8. FIGS. 8 and 9 show cross-sections A-A and B-B of the bipolar plate 10, showing, respectively, the first side 26 (inlet side) and the second side 27 (outlet side) of the active area AA of the bipolar plate 10.

(27) In contrast to the embodiment shown in FIGS. 2 through 6, the profiled sides of the anode and cathode plates 19, 20 are piano-parallel, but not so the mutually-facing sides 28, 29 into which the coolant subchannels 23a, 23b are incorporated.

(28) The mutually-facing sides 28, 29 run parallel to the anode gas channels and the cathode gas channels. This means that there is no change in the partial cross-sectional area and/or the hydraulic partial diameter of the coolant subchannels 23a, 23b in the anode and the cathode plates 19, 20.

(29) FIGS. 10 and 11 show, as do FIGS. 5 and 6, a slightly varied embodiment of the bipolar plate according to FIGS. 7 through 9, with trough-like anode gas channels 22 and cathode gas channels 21 (having flank angles less than 90°), as well as coolant channels 23.

(30) Although, in this variant, the forms of the partial coolant cross-section of the coolant subchannels 23a, 23b are different, the cross-sectional area and/or the hydraulic diameter does, however, remain constant. In addition, the thickness of the material between the coolant channels 23 and the adjacent anode gas channels 22 and cathode gas channels 21 is also constant.

(31) FIG. 12 again shows a bipolar plate 10 according to FIG. 1 in a longitudinal section C-C, the course of which is shown in FIG. 13. FIGS. 13 and 14 show cross-sections A-A and B-B of the bipolar plate 10, showing, respectively, the first side 26 (inlet side) and the second side 27 (outlet side) of the active area AA of the bipolar plate 10.

(32) The profiled sides of the anode and cathode plates 19, 20, as also their mutually-facing sides 28, 29 into which the coolant subchannels 23a, 23b are incorporated, are piano-parallel in form.

(33) Differing from the other embodiments illustrated, the coolant channels 23 are not aligned parallel to the anode gas and cathode gas channels 22, 21, but rather to the mutually-facing sides 28, 29 of the anode plate 19 and the cathode plate 20.

(34) FIGS. 15 and 16 represent an embodiment of the bipolar plate 10, in which the width B of anode and cathode gas channels 22, 21 is varied, and again show cross-sections A-A and B-B, which show, respectively, the first side 26 (inlet side) and the second side 27 (outlet side) of the active area AA, in which the width B of the anode gas channels 22 decreases from the first side 26 to the second side 27 of the active area AA. In contrast, the width B of the cathode gas channels 21 increases from the first side 26 to the second side 27 of the active area AA. The coolant channels 23, on the other hand, extend over the active area AA with a constant cross-sectional area and/or a constant hydraulic diameter, wherein the distance from the anode and cathode gas channels 21, 22 remains constant, and wherein the coolant subchannels 23a in the anode plate 19 have an increasing partial cross-sectional area and/or a hydraulic partial diameter. In the case of the cathode plate 20, this is formed in exactly the opposite way. The profiled sides of the anode and cathode plates 19, 20, as also their mutually-facing sides 28, 29 into which the coolant subchannels 23a, 23b are incorporated, are piano-parallel in form.

(35) The anode gas channels 22 and the cathode gas channels 21, and also the coolant channels 23, have a trough-like design with flank angles of less than 90°.

LIST OF REFERENCE SYMBOLS

(36) 10 Bipolar plate

(37) 11 Anode inlet opening

(38) 12 Anode outlet opening

(39) 13 Cathode inlet opening

(40) 14 Cathode outlet opening

(41) 15 Coolant inlet opening

(42) 16 Coolant outlet opening

(43) 17 Cathode side

(44) 18 Anode side

(45) 19 Anode plate

(46) 20 Cathode plate

(47) 21 Cathode gas channel

(48) 22 Anode gas channel

(49) 23 Coolant channel

(50) 23a, 23b Coolant subchannels

(51) 24 Seal

(52) 25 Membrane electrode unit

(53) 26 First side

(54) 27 Second side

(55) 28, 29 Side

(56) AA Active area (reaction area)

(57) IA Inactive area

(58) SA Supply area

(59) DA Distribution area

(60) H Height

(61) B Width