Hydrogen Fuel Cell Stack and Method for Upgrading a Hydrogen Fuel Cell Stack

Abstract

This disclosure relates to a hydrogen fuel cell stack with one or more hydrogen fuel cell (102) having in turn a proton exchange membrane (104), a hydrogen reaction layer (112) and an oxygen reaction layer (116) within a pair of bipolar plates (106). At least a bipolar plate (106) comprises a channel (108) inside for hydrogen inflow. Additionally, this disclosure relates to a method of upgrading a hydrogen fuel cell stack, said method comprising inserting a channel (108) for hydrogen inflow inside at least a bipolar plate (106).

Claims

1. A hydrogen fuel cell stack comprising one or more hydrogen fuel cell comprising a Proton Exchange Membrane, a hydrogen reaction layer configured for receiving an hydrogen inflow, and an oxygen reaction layer within a pair of bipolar plates, the hydrogen fuel cell stack characterized in that at least one of the bipolar plates comprises a channel inside connected to the hydrogen inflow.

2. The hydrogen fuel cell stack of claim 1, wherein the channel connected to the hydrogen inflow is made within a first layer said first layer contacting the hydrogen reaction layer of the hydrogen fuel cell.

3. The hydrogen fuel cell stack of claim 1, wherein the channel connected to the hydrogen inflow is made within a second layer, said second layer contacting the oxygen reaction layer of the hydrogen fuel cell.

4. The hydrogen fuel cell stack of claim 1, wherein the channel for the hydrogen inflow is engraved within the bipolar plate.

5. The hydrogen fuel cell stack of claim 1, wherein the hydrogen reaction layer comprises a plurality of distribution ducts.

6. The hydrogen fuel cell stack of claim 1, wherein the oxygen reaction layer comprises a plurality of cooling grooves.

7. The hydrogen fuel cell stack of claim 1, wherein the oxygen reaction layer comprises a plurality of distribution ducts.

8. The hydrogen fuel cell stack of claim 5, wherein the channel connected to the hydrogen inflow has the same cross-sectional area as the distribution ducts of the hydrogen reaction layer.

9. The hydrogen fuel cell stack of claim 1, wherein the bipolar plates are made of graphite.

10. Method of upgrading a hydrogen fuel cell stack, the fuel cell stack comprising one or more hydrogen fuel cell comprising a Prroton Exchange Membrane, a hydrogen reaction layer configured for receiving an hydrogen inflow, and an oxygen reaction layer within a pair of bipolar plates, the method comprising inserting inside at least a bipolar plate a channel connected to the hydrogen inflow.

11. The method of upgrading a hydrogen fuel cell stack of claim 10, said method comprising inserting a first layer comprising the channel connected to the hydrogen inflow contacting the hydrogen reaction layer of the hydrogen fuel cell.

12. The method of upgrading a hydrogen fuel cell stack of claim 10, said method comprising inserting a second layer comprising the channel connected to the hydrogen inflow contacting the oxygen reaction layer of the hydrogen fuel cell.

13. The method of upgrading a hydrogen fuel cell stack of claim 10, said method comprising engraving the channel connected to the hydrogen inflow within the bipolar plate.

14. The method of upgrading a hydrogen fuel cell stack of claim 13, comprising a first step of splitting the bipolar plate in two parts, a second step of engraving the channel and a third step of connecting again both parts of the bipolar plate.

15. A hydrogen fuel cell stack comprising: one or more hydrogen fuel cell comprising: a Proton Exchange Membrane; a hydrogen reaction layer configured for receiving an hydrogen inflow; and an oxygen reaction layer within a pair of bipolar plates, wherein at least one of the bipolar plates comprises a channel inside connected to the hydrogen inflow, the channel comprising an inlet configured for receiving super cooled hydrogen gas and an outlet connected to the hydrogen inflow.

16. The hydrogen fuel cell stack of claim 15, wherein the hydrogen reaction layer is an anode and the oxygen reaction layer is a cathode of the hydrogen fuel cell.

17. The hydrogen fuel cell stack of claim 15, wherein at least one of the pair of bipolar plates is split into two parts, and wherein the channel is engraved on one of the two parts to form the channel inside the pair of bipolar plates.

18. The hydrogen fuel cell stack of claim 15, wherein at least one of the pair of bipolar plates is split into two parts, and wherein the channel is engraved on both of the two parts to form the channel inside the pair of bipolar plates.

19. The hydrogen fuel cell stack of claim 15, wherein at least one of the hydrogen reaction layer and the oxygen reaction layer comprises a plurality of distribution ducts.

20. The hydrogen fuel cell stack of claim 15, wherein the oxygen reaction layer comprises a plurality of cooling grooves.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Next, in order to facilitate the comprehension of this disclosure, in an illustrative rather than limitative manner a series of embodiments with reference to a series of figures shall be made below.

[0029] FIG. 1 is a schematic view of an exemplary embodiment of a fuel cell stack showing its main elements.

[0030] FIG. 2 shows one of the bipolar plates of the fuel cell stack of FIG. 1 split for the inclusion of a channel according a particular embodiment.

[0031] FIG. 3 shows the two parts of the bipolar plate of FIG. 2 with the channel according a particular embodiment.

[0032] FIG. 4 shows a top-perspective view of an exemplary embodiment of the main layers of a fuel cell including a first layer including the channel contacting the hydrogen reaction layer.

[0033] FIG. 5 shows a bottom-perspective view of the embodiment of the main layers of the fuel cell of FIG. 4.

[0034] These Figures Refer to the Following Set of Elements: [0035] 100. hydrogen fuel cell stack [0036] 102. hydrogen fuel cell [0037] 104. proton exchange membrane [0038] 106. bipolar plates [0039] 106a, 106b parts of the bipolar plates [0040] 108. Channel [0041] 110. first layer for the channel [0042] 112 hydrogen reaction layer [0043] 116 oxygen reaction layer [0044] 118 distribution ducts of the hydrogen and oxygen reaction layers [0045] 120 cooling grooves of the oxygen reaction layer

DETAILED DESCRIPTION

[0046] The present disclosure refers to a hydrogen fuel cell stack 100 which comprises one or more hydrogen fuel cell 102. Each one of these hydrogen fuel cells 102 comprises in turn at least a Proton Exchange Membrane (PEM) 104, a hydrogen reaction layer 112 and an oxygen reaction layer 116 within a pair of bipolar plates 106. The hydrogen reaction layers 112 are the anodes and the oxygen reaction layers 116 are the cathodes of the fuel cells 102.

[0047] As it can be seen in FIG. 1 at least a bipolar plate 106 comprises a channel 108 inside for hydrogen inflow, in order to heat up the hydrogen gas boiled off from a cryogenic liquid state at a very low temperature (about 20K) up to a usable temperature (about 273K-300K) for the fuel cell in which the hydrogen inflow enters. This channel 108 inside the bipolar plate 106 may have different shapes and length, and it acts as a heat exchanger, so the hydrogen inflow will be heated up before entering the hydrogen reaction layer 112, taking advantage of the heat generated in the fuel cells 102 themselves and accumulated in the bipolar plates 106, without the need for an external heating source.

[0048] This channel 108 inside the bipolar plates 106 acting as a heat exchanger increase the hydrogen inflow temperature before reaching the hydrogen reaction layer 112. So, this heat exchanger or slim gas heating circuit increase the hydrogen inflow temperature with the minimum weight and volume increase of the overall system while using the, otherwise lost, heat dissipated by the fuel cells 102 through the bipolar plates 106, minimizing the power self-consumption of the system, therefore making it as efficient as possible.

[0049] Then, the channel 108 of the present disclosure is a light-weight and compact heat exchanger integrated into the fuel cell 102 body, which takes advantage of the low viscosity and the great thermal conductivity of hydrogen.

[0050] Unlike existing solutions, which need a dedicated and external heat exchanger being volume and weight consuming, in the present disclosure the heat exchanger is inside the bipolar plates 106, so the heat exchange may be considered the fuel cell 102 itself and no substantial volume increase is expected.

[0051] Moreover, since the channel 108 or heat exchanger is located inside a heat source (the bipolar plate 106), the heat for heating up the hydrogen inflow does not need to be ducted to an external heat exchanger, avoiding fans, ducts, wiring, piping, fittings or certain valves with the corresponding weight and volume thereof. Additionally, this leads to a simpler system with many fewer components.

[0052] Another advantage of the present disclosure is that undesirable icing of the already existing solutions is avoided by heating the overcooled hydrogen inflow in a high temperature environment, as that existing in the fuel cells 102 core, specifically the bipolar plates 106 (about 323K), being such temperature far away from the dew point of any water vapour flow that could be around.

[0053] Additionally, as the heat exchanger is enclosed inside the hydrogen fuel cell stack 100, only clean hydrogen is in contact with the channel 108 or heat exchanger, therefore no heat exchanger cleaning or maintenance is necessary.

[0054] Furthermore, reduced cooling of the fuel cells 102 is needed. Since the fuel cell 102 dissipates half of the total power produced in form of heat, this heat must be removed from the cell 102 by means of the cell's cooling system as already existing. However, using some of this heat (around 10%) for a useful purpose, which is the heating of the hydrogen inflow, the cooling system requirements decrease, allowing lighter and smaller fans and less power needed for them. So, the channel 108 provides sufficient heating of the hydrogen and useful cooling of the fuel cell 102.

[0055] Although this disclosure is specifically described here for Proton Exchange Membrane (PEM) fuel cell stacks, it can be used with any kind of fuel cells couple to a liquid hydrogen system.

[0056] FIGS. 2 and 3 show a particular embodiment in which the channel 108 for the hydrogen inflow is engraved directly within the bipolar plate 106. This channel 108 or heat exchanger is machined directly within the bipolar plates 106 and no additional parts are expected, neither appreciable weight nor volume increase, since the channel 108 is integrated into the fuel cell 102 mainly by removing material in existing parts. For such purpose the bipolar plates 106 are firstly split in two parts 106a and 106b and then the channel 108 is engraved directly on one of the parts 106a or 106b or on both parts 106a and 106b which will be connected together again forming the bipolar plate 106 with the channel 108 inside.

[0057] Accordingly, some components such as sealing joints or some small piping will be needed, although the will add very low weight in any case and even lower when compared to an external dedicated heat exchanger.

[0058] In this case, as the heat exchanger channels 108 are engraved directly inside the fuel cell 102, the resulting structural integrity of the heat exchanger is even greater.

[0059] Alternatively, FIGS. 4 and 5 show a particular embodiment in which the channel 108 for the hydrogen inflow is made within a first layer 110, the first layer 110 contacting the hydrogen reaction layer 112 or anode of the hydrogen fuel cell 102. In order to include the first layer 110 with the channel 108, the depth of the bipolar plate 106 might have to be reduced.

[0060] As an alternative embodiment not shown in the figures, the channel 108 for the hydrogen inflow is made within a second layer, the second layer contacting in this case the oxygen reaction layer 116 of the hydrogen fuel cell 102. Similarly, in order to include the second layer with the channel 108, the depth of the bipolar plate 106 might have to be reduced.

[0061] With accord to a preferred embodiment, the oxygen reaction layer 116 comprises a plurality of cooling grooves 120 for the cooling of said oxygen reaction layer 116, being the cooling fluid flowing through the cooling grooves 120 typically air or water.

[0062] In accordance with a particular embodiment, the hydrogen reaction layer 112 or anode comprises a plurality of distribution ducts 118 for the distribution of the hydrogen all along the entire surface of the Proton Exchange Membrane (PEM) 104.

[0063] According with other particular embodiment, the oxygen reaction layer 116 or cathode has a plurality of distribution ducts 118 for the distribution of the oxygen all along the entire surface of the cathode, and additionally so that the entering air drags the generated water outside the fuel cell 102.

[0064] Moreover, preferably both hydrogen reaction layer 112 and oxygen reaction layer 116 have distribution ducts 118 for the complete distribution of hydrogen and oxygen, in order to provide a uniform reaction over the surface of the membrane.

[0065] According to an exemplary embodiment, the channel 108 for the hydrogen inflow of the present disclosure is related to the fuel consumption of an aircraft fuel system. Since the quantity of hydrogen flow to be heated is substantially the same as the quantity of hydrogen being consumed by the cell, the channel 108 for the hydrogen inflow has approximately the same cross-sectional area as the distribution ducts 118 of the hydrogen reaction layer 112. More specifically, the channel 108 and the distribution ducts 118 are each sized such that, in operation, the quantity of hydrogen flowing through the channel 108 is approximately equal to the quantity of hydrogen flowing through the distribution ducts 118.

[0066] Regarding the materials, the bipolar plates 106 are made of any electrical conductor material. According to a particular embodiment the bipolar plates 106 are made of graphite.

[0067] Additionally, the present disclosure relates to a method of upgrading a hydrogen fuel cell stack, the method comprising inserting a channel 108 for hydrogen inflow inside at least a bipolar plate 106.

[0068] According a preferred embodiment, the method comprises inserting a first layer 110 with the channel 108 for hydrogen inflow, the first layer 110 contacting the hydrogen reaction layer 112 of the hydrogen fuel cell 102.

[0069] With accord to an alternative embodiment, the method comprises inserting a second layer with the channel 108 for hydrogen inflow, the second layer contacting in this case the oxygen reaction layer 118 of the hydrogen fuel cell 102.

[0070] Alternatively, a particular embodiment of the method comprises engraving the channel 108 for hydrogen inflow directly within the bipolar plate 106.

[0071] For such purpose, in a first step of the method the bipolar plates 106 are split in two parts. Then, in a second step of the method the channel 108 is engraved directly on one of the parts or on both parts of the bipolar plate 106. Finally, in a third step both parts of the split bipolar plate 106 are connected together again forming the bipolar plate 16 with the channel 108 inside.