FR3053534A1 - FUEL CELL MODULE HAVING A 2 INPUT HYDROGEN CIRCUIT - Google Patents

Abstract

A fuel cell module having a hydrogen circuit for supplying hydrogen to the respective anode compartments of cells of an electrochemical cell assembly, the hydrogen circuit having a plurality of inputs (111, 112) through which hydrogen is intended to be injected alternately, which can promote the evacuation of water in the hydrogen circuit while limiting the overall consumption of hydrogen consumed (Figure 3).

Description

(54) FUEL CELL MODULE HAVING A HYDROGEN CIRCUIT WITH 2 INPUTS.

(© Fuel cell module provided with a hydrogen circuit for supplying hydrogen to the respective anode compartments of cells of an assembly of electrochemical cells, the hydrogen circuit comprising several inputs (111, 112) through which Hydrogen is intended to be injected alternately, which can promote the evacuation of water in the hydrogen circuit while limiting the overall consumption of hydrogen consumed (Figure 3).

FUEL CELL MODULE HAVING A 2 INPUT HYDROGEN CIRCUIT

DESCRIPTION

TECHNICAL AREA AND PRIOR ART

The present application relates to the technical field of fuel cells and in particular a fuel cell device having an improved configuration of the hydrogen circuit making it possible to obtain better efficiency.

A fuel cell 1 is a converter of chemical energy into electrical energy provided with at least one electrochemical cell 2 comprising an anode 4 separated from a cathode 6 by an electrolyte 8 typically in the form of a polymer membrane. The electrochemical cell is generally supplied by two different gases, the first can for example be hydrogen oxidizing on contact with the anode, the second oxygen reduced in contact with the cathode according to the following electrochemical reactions:

ff, -> 2B * + 2e

Equation 1

-Ο, + 2H + 2e ~ O

Equation 2

Fuel cells that consume hydrogen are also called hydrogen cells. Oxidation of hydrogen produces electrons flowing from anode 4 to cathode 6 via an electrical circuit 10 external to the cell, so that an element 12 integrated into this electrical circuit 10 can be supplied with electricity by the battery. The membrane 8 separating the electrodes 4, 6 is generally made from porous and electrically insulating material, but ionic conductor.

PEMFC type fuel cell cells (acronym in English for “Polymer Electrolyte Membrane Fuel Cells” or “proton exchange membrane fuel cells”) typically have a proton exchange membrane based on a polymer, in particular a fluoropolymer.

A PEMFC type fuel cell is typically produced by stacking elementary cells, each cell being formed between one face of a bipolar plate, of an element called AME (for "electrode membrane assembly" corresponding here to the stack cathode membrane anode) and one side of another bipolar plate. The bipolar plates are generally metallic or based on composite graphite and provided with grooves or supply channels on each face, the channels of a first face allowing the hydrogen supply, while the channels of a second opposite face on the first side allow oxygen supply.

The reactants are thus introduced towards the electrodes 4, 6 via the supply channels present in the bipolar plates 13, these supply channels also making it possible to remove the product of the above electrochemical reactions. The volume delimited by a supply channel and an electrode forms an anode compartment 14 when the electrode is the anode, or a cathode compartment 16 when the electrode is the cathode (FIG. 1).

A hydrogen electrochemical cell 2 theoretically provides an electrical voltage which varies in particular as a function of the partial pressure of the fluids transporting the fuels in the anode and cathode compartments. In order to obtain exploitable electrical voltages for the uses mentioned above, several electrochemical cells 2 are assembled in series to form an assembly, in the form of a stack also called a "stack". An electrochemical cell can therefore comprise several electrochemical cells, supplied from the same supply channel serving several cathode or anode compartments.

The performance of a hydrogen electrochemical cell depends in particular on the humidity level of the membrane 8: this humidity allows good ionic conduction of the hydrogen ions through the membrane 8. The hydration of the membrane 8 is naturally maintained thanks to the water generated at the cathode.

A fraction of the water generated at the cathode is transferred to the anode after diffusion through the membrane 8.

A phenomenon of water accumulation in the compartments intended for hydrogen can then occur. However, too high a humidity level or an accumulation of water under (liquid phase) at the anode is likely:

- to cause a reduction in the active surface of the anode and therefore an increase in the current density passing through its still active areas,

- being at the origin of overvoltages at the anode which reduces the voltage delivered by the battery and consequently its efficiency,

- reduce the current that can be generated by the battery for a voltage across its terminals imposed by the external circuit, and consequently its power,

- create a hydrogen shortage in localized flooded areas which can lead to degradation of the battery structure and reduce its lifespan,

- To increase too much the diffusion of nitrogen from the cathode towards the anode at the origin of a shortage in hydrogen likely to degrade the battery.

In other words, stagnation of water, liquid, and too much nitrogen accumulation, especially in the anode compartment, degrades the performance of an electrochemical cell.

To prevent these drawbacks, the anode compartment can be regularly purged. The water in the liquid state and the inert gases present in the compartment are then removed. This evacuation can lead to hydrogen consumption in the battery.

A typical hydrogen fuel cell module has a single input port for injecting hydrogen throughout the stack, a single output port common to all cells.

An example of a hydrogen injection and purging cycle of such a module is illustrated in FIGS. 2A-2B.

In the anode compartment, the pressure increases up to a regulated set pressure. The hydrogen pressure is regulated in order to inject only the 2N quantity of hydrogen consumed at each instant by the stack of cells at the anode.

In FIG. 2A, the injection and circulation of hydrogen in the channels of a bipolar plate are symbolized respectively by arrows SI, S2. When water collects at the anode, a purge sequence is initiated.

A purge valve is then opened in order to evacuate the water as well as nitrogen (arrow S3). At the same time, hydrogen is evacuated. A hydrogen pressure regulator upstream of the cell is provided to then increase the hydrogen flow rate (arrow S4) in order to compensate for the loss of hydrogen due to the purging.

Typically, the hydrogen flow rate can then be doubled.

During the purge, the water located near an exhaust pipe is firstly evacuated, followed by droplets hanging in the channels.

This second evacuation phase is generally ineffective, which generally requires prolonging the purge and consequently results in a high consumption of hydrogen and a low yield.

The problem arises of finding a new improved device making it possible to correctly purge the hydrogen circuit of a fuel cell while limiting the quantity of hydrogen consumed.

STATEMENT OF THE INVENTION

One embodiment of the present invention relates to a fuel cell module provided with a hydrogen circuit for supplying hydrogen to respective anode compartments of cells of an assembly of electrochemical cells of the module, the hydrogen circuit comprising:

- a first inlet capable of allowing the introduction of hydrogen into the hydrogen circuit,

- a second inlet to allow the introduction of hydrogen into the hydrogen circuit, the first inlet, the second inlet and the hydrogen circuit being configured so that a first stream of hydrogen introduced through the first inlet is brought through a first set of one or more cells of the assembly before crossing a second set of one or more cells of the assembly and so that a second stream of hydrogen introduced by the second inlet is brought through the second set of cells before crossing the first set of cell (s) of the assembly,

- A purge outlet adapted, when open, to allow purging of the hydrogen circuit.

Thus, the module can be provided with hydrogen supply control means for:

- introduce hydrogen through the first inlet and for,

- introduce hydrogen through the second inlet.

It is possible to inject hydrogen alternately between the first and the second inlet. Thus, the hydrogen supply control means can be configured to alternately, introduce hydrogen through the first inlet and then to introduce hydrogen through the second inlet.

The alternating injections make it possible to unhook the droplets of liquid water present in the anode channels and to concentrate this liquid water in the vicinity of the purge orifice. This improves the hydrogen yield of the cell by preparing the dropout of the liquid water droplets in advance of the phase and by favoring the evacuation of the liquid water in the first moments of the anodic purging phase.

The parameters of the purge sequence can be optimized, in particular the time between two purges and the duration of the purges.

Advantageously, when hydrogen is introduced through the first inlet, the second inlet is closed so that no hydrogen is introduced through the second inlet, and when hydrogen is introduced through the second inlet, the first entry is closed so that no hydrogen is introduced through the first entry.

According to a possible implementation of the device, the hydrogen supply control means comprise a first solenoid valve connected to the first input of the hydrogen circuit and a second solenoid valve connected to the second input of the hydrogen circuit.

The opening and closing of the purge outlet can also be carried out by means of a solenoid valve.

According to a particular operating mode, the first inlet and the second hydrogen injection inlet can be opened simultaneously during the purging phase. In this way, the entire content of the anode circuit is blown towards the purge outlet during this phase.

Advantageously, the first hydrogen injection inlet and / or the second inlet can (have) not be provided with a solenoid valve with controllable proportional opening. This type of solenoid valve, which can be opened to a greater or lesser amplitude, allows the implementation of a balancing strategy for the two sets of cells when an imbalance in the cell voltages occurs between the two sets of cells. Such a strategy may consist, for example, during the purging phase, when such an imbalance is detected, to further open a hydrogen injection solenoid valve primarily serving a given set of cells, in particular that presenting the voltages of lowest cells or with the largest standard deviation in terms of individual cell voltages.

Thus, an embodiment of the present invention relates to a method of controlling the module in which:

- the respective voltages of the cells of the first set of cells and of the second set of cells are measured, then

- the opening amplitude of the first solenoid valve with proportional opening which can be controlled or of the second solenoid valve with proportional opening which can be controlled is adapted as a function of the voltage measurement carried out.

The assembly of cells is typically in the form of a stack.

Advantageously, the first entry is then located at a first end of this stack while the second entry is located at another end of this stack.

The module cell assembly can be provided with a first set of cells and a second set of cells with an evacuation structure disposed between this first set and the second set, the evacuation structure leading to the outlet. purge.

This evacuation structure can be integrated into a separating plate arranged in the stack of cells and provided with an evacuation means. Such a plate sealingly separates the two hydrogen injection chambers respectively associated with the first hydrogen inlet and the second hydrogen inlet, while allowing communication between the outlet chambers of the anode channels of the two sets of cells.

Advantageously, the purge outlet orifice can be offset so as to be located between the first set and the second set of cells, at the level of the separating plate. This configuration allows not to favor the blowing of a set of cells during the purge phase if the two hydrogen injection inlets are open.

Advantageously, the fuel cell is of the PEMFC type, i.e. a fuel cell with a polymer electrolyte membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

Other details and characteristics of the invention will appear from the description which follows, given with reference to the following appended figures.

The identical, similar or equivalent parts of the different figures have the same references so as to facilitate the passage from one figure to another. The different parts shown in the figures are not necessarily so on a uniform scale, to make the figures more readable.

FIG. 1 illustrates a fuel cell provided with several electrochemical cells;

FIG. 2 illustrates a principle for managing the injection of hydrogen into a hydrogen circuit and the purging of such a circuit belonging to a fuel cell;

FIG. 3 illustrates an exemplary embodiment of a hydrogen injection circuit in a fuel cell module comprising a hydrogen circuit with several inputs;

FIGS. 4A-4D represent different phases of operation of the hydrogen circuit of a fuel cell according to the invention;

FIGS. 5A-5C illustrate an assembly of elements of a fuel cell provided with two hydrogen circuit inputs;

Identical, similar or equivalent parts of the different figures have the same reference numerals so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not necessarily shown on a uniform scale, to make the figures more readable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 4 shows a fuel cell module 100, in particular a hydrogen cell of the PEMFC type formed of an assembly comprising a plurality of stacked electrochemical cells (not shown). The module 100 is provided with a gas circuit (not shown), in particular with hydrogen, connecting and comprising anode compartments of the cell which it is desired to supply with hydrogen. This hydrogen circuit is here provided with a first inlet 111 and a second inlet 112.

The hydrogen injected at the inputs 111, 112 can come from the same tank 1 (not shown) after having passed through a supply circuit 10.

To pass the hydrogen from the reservoir 1 stored at high pressure (for example of the order of 350 bars) to a lower pressure and better suited to supplying the battery, the supply circuit 10 is provided in this example of a high pressure regulator 11, followed by a low pressure regulator 13. As a safety measure, a relief valve 12 can be provided at the outlet of the high pressure regulator, in order to allow hydrogen to be released from the supply circuit 10 when the pressure is above a given threshold, for example of the order from 10 bars. The supply circuit 10 is here provided with a pressure probe 14 at the outlet of the low pressure regulator 13.

In order to be able to control the admission of hydrogen respectively to the first inlet 111 and to the second inlet 112, the supply circuit 10 also includes solenoid valves 15, 16 actuated by means of a control device, the first input 111 and the second input 112 can thus be opened (respectively closed) independently of one another. The control device 100 may for example be an electronic device in the form of one or more cards comprising, with analog integrated circuits or ASICs, logic and programmable circuits (for example of the FPGA, microprocessor, microcontroller type).

The hydrogen circuit of the module 100 is also provided with an outlet 120 for evacuation or purging by which any residual part of hydrogen which has been injected by the inputs 111, 112 and which has not been used, as well as water in the liquid state is discharged, this residual hydrogen and this water being capable of constituting obstacles to the free circulation of new hydrogen in the hydrogen circuit.

In this exemplary embodiment, the output 120 operates in "dead end" mode also called "dead-end", which means that it is mostly closed except during purging phases of the hydrogen circuit. During such phases, the outlet 120, which is connected via the hydrogen circuit to the respective anode compartments of cell cells, is temporarily opened so that unreacted hydrogen blows water in the liquid phase. towards the outlet 120. The opening and closing of the outlet 120 can be carried out periodically and are controlled by a solenoid valve 126 for purging, which can itself be controlled by the aforementioned control device.

A special feature of the present device is that instead of supplying hydrogen to the assembly of electrochemical cells of the cell by a single hydrogen intake input, several inputs 111, 112 are used to supply the cell, which can make it possible to create different hydrogen flow paths in the hydrogen circuit depending on the input 111 or 112 through which the hydrogen was injected.

The supply of hydrogen to the cell can be carried out alternately between the first input 111, and the second input 112 according to a repetition of cycles during which alternately hydrogen is injected via the first input 111 while retaining the second input 112 preferably closed, then hydrogen is injected via the second inlet 112 while keeping the first inlet 111 preferably closed.

Thus, when a stream of hydrogen is injected via the first inlet 111, this stream is sent as a priority by a first subset of cells located near this first inlet 111, while when hydrogen is injected through the second inlet 112, this hydrogen is sent as a priority to a second subset of electrochemical cells connected in series to the first subset and associated with this second inlet 112.

Compared to a conventional hydrogen injection with a single inlet, this alternating hydrogen injection allows a more efficient evacuation of the water likely to accumulate in the respective parts of the hydrogen circuit of these subsets of cells. As an example of a result, a 5kW fuel cell supplied with hydrogen in a conventional manner, by a single injection inlet, the purge of which would be timed at 2 seconds of opening every 8 seconds, i.e. a hydrogen yield of 80%, could then be clocked at 1 second opening every 30 seconds, ie a hydrogen yield of 97%, by implementing the present invention.

An example of the operating cycle of the hydrogen circuit of the fuel cell module 100 will now be given in connection with FIGS. 4A-4D.

FIGS. 4A-4B serve to illustrate a first operating phase during which hydrogen is injected into the hydrogen circuit via the first inlet 111 which is located near a first electrochemical cell with a first sub set (schematically represented by a block 102A) of electrochemical cells without injecting hydrogen via the second inlet 112. The hydrogen entering the circuit via the first inlet 111 is brought to traverse the first subset then a second subset (represented schematically by a block 102B) of cells connected in series with the first subset. The path of the hydrogen injected by the first inlet, then circulating in the first subset, then transmitted from the first subset to the second subset, then circulating in the second subset is symbolized respectively by arrows FIA, FA, FAB , FB.

In this exemplary embodiment with two inputs, two cells are advantageously provided with substantially also the same number of cells, in order to allow evacuation of balanced water between these two half-stacks.

When a 2N quantity of hydrogen is injected (FIG. 2A) through the first inlet 111, the first subset 102A may be required to consume an amount of hydrogen substantially equal to N, while an intake of an amount d hydrogen substantially equal to N is brought to the second sub-assembly 102B which is capable of consuming this quantity N. This injection then makes it possible, as a priority, to evacuate the water accumulated in the sub-assembly 102A associated with the inlet 111 through which the hydrogen is emitted. A capture means 115, for example in the form of one or more channels (not shown) can be arranged between the first subset 102A and the second subset 102B in order to allow water to be evacuated from the first subset 102A to the purge outlet 120 which is then closed. This evacuation then takes place without loss of hydrogen.

Water can then tend to accumulate (FIG. 2B) in an area 104B of the second sub-assembly 102B, in particular located near the second inlet 112.

The state of opening of the solenoid valves 15, 16 is then modified to allow the hydrogen circuit to pass into a second operating phase.

FIGS. 4C-4D illustrate this second operating phase during which hydrogen is introduced via the second inlet 112 which is located near an electrochemical cell of the second subset 102B of electrochemical cells, while the first inlet 111 remains closed , which means that the arrival of hydrogen through this inlet 111 is interrupted. A stream of hydrogen injected through the second inlet 111 is caused to pass through the second subset 102B then a first subset 102A of cells. The path of the hydrogen injected by the second inlet, then circulating in the second subset, then transmitted from the second subset to the first subset, then circulating in the first subset is symbolized respectively by arrows F'IB, F 'B, F'BA, F'A.

This injection then makes it possible to evacuate as a priority the water accumulated in the sub-assembly 102B associated with the inlet 112 by which the hydrogen is emitted. The capture means 115 arranged between the first subset 102A and second subset 102B can then make it possible to evacuate the water from the second subset

102B to the drain outlet 120 which is then closed. This evacuation then takes place without loss of hydrogen.

The water evacuated from the subassemblies 102A, 102B of cells during the injection phases is stored near the drain outlet 120, the opening and closing of which are controlled by the solenoid valve 126. When this purge solenoid valve 126 in order to purge the hydrogen circuit, firstly the accumulated water is removed first, then secondly the hydrogen to which a neutral gas such as nitrogen can be added . The duration of the purge can thus be limited and the quantity of hydrogen leaving the hydrogen circuit limited.

With the same fuel cell configuration, another operating mode than that of alternating hydrogen injection can be provided. This consists of supplying the fuel cell with the two hydrogen injection inputs which are permanently open. This mode can be advantageous for supplying a high power fuel cell, formed of a large number of cells.

FIGS. 5A-5C illustrate by means of perspective views of the elements of a fuel cell module as described above, and in particular of the plates 302a, 302b situated respectively at the ends of the stack, a first plate 302a d the end being provided with the first inlet 111 of the hydrogen circuit, a second end plate 302b comprising the second inlet 122 of the hydrogen circuit. In this exemplary embodiment, the outlet 120 for purging the hydrogen circuit is also provided in the first plate 302a.

The first plate 302a, here is further provided with an inlet 133 for the cooling circuit and an outlet 144 for the air circuit, while the second plate 302b, can be provided with an outlet 134 for the cooling circuit and an inlet 143 of the air circuit.

Each end plate 302a (or 302b) may include a current collector 311a (resp. 311b) ensuring the electrical connection between the system and the two end cells of the stack. This component is made of an electrically conductive material and, preferably, also ensures electrical contact with the electrochemical cells. The current collectors 311a, 311b are inserted into the end plates 302a, 302b which compress the collectors against the end cells.

For the sake of simplification, the stack shown in FIGS. 5A-5C comprises only two bipolar plates 322a, 322b belonging respectively to a first subset and to a second subset of electro-chemical cells.

The bipolar plates 322a, 322b are shown here without their splines or channels for supplying hydrogen and oxygen present respectively on their two opposite faces. Likewise, the electrochemical core comprising a proton exchange membrane on each side on which an electrode is formed is not shown.

The stack also includes a separator plate 350 delimiting the two subsets of cells associated respectively with the first inlet 111 and the second inlet 112 of hydrogen.

To allow the stack to be held in position, holding means in the form of centralizing insulating tubes 362 and pulling insulating tubes 361 can be provided.

According to an alternative embodiment, there is provided an evacuation structure integrated into the separating plate of the two sets of cells and configured to seal the two hydrogen injection chambers respectively associated

0 at the first hydrogen inlet and at the second hydrogen inlet. The separator plate allows communication from the outlet chambers of the anode channels of the two sets of cells. A purge outlet port can be located between the first set and the second set of cells, at the separator plate.

Claims (10)

1. Fuel cell module comprising a hydrogen circuit for supplying hydrogen to respective anode compartments of cells of an assembly of electrochemical cells of the module, the hydrogen circuit comprising: - a first input (111) to the hydrogen circuit, - a second input (112) of the hydrogen circuit into the hydrogen circuit, the first input, the second input and the hydrogen circuit being configured so that a first stream of hydrogen introduced by the first input is intended to cross a first set of one or more cells of the assembly before crossing a second set of one or more cells of the assembly and so that a second stream of hydrogen introduced by the second inlet is intended to cross the second set of cells before crossing the first set of cell (s) of the assembly, a purge outlet (120) suitable, when open, for permitting purging of the hydrogen circuit, the module further comprising means for controlling the supply of hydrogen for: - introduce hydrogen through the first inlet, - introduce hydrogen through the second inlet. 2. Fuel cell module according to claim 1, wherein the hydrogen is introduced alternately through the first inlet and then through the second inlet. 3. Fuel cell module according to one of claims 1 or 2, wherein when hydrogen is introduced through the first inlet, the second inlet is closed so that no hydrogen is introduced through the second inlet, and in which when hydrogen is introduced through the second inlet, the first inlet is closed so that no hydrogen is introduced through the first inlet. 4. Fuel cell module according to one of claims 1 to 3, wherein the hydrogen supply control means comprise a first solenoid valve (15) connected to the first inlet (111) of the hydrogen circuit and a second solenoid valve (16) connected to the second inlet (112) of the hydrogen circuit. 5. Module according to one of claims 1 to 4, wherein the opening and closing of the purge outlet are carried out by means of a solenoid valve (126). 6. Module according to one of claims 1 to 5, wherein the cell assembly is a stack, the first inlet (111) being located at a first end of this stack, the second inlet (112) being located at a other end of this stack. 7. Module according to one of claims 1 to 6, wherein the cell assembly comprises a first set of cells and a second set of cells, a discharge structure (150) being disposed between the first set of cells and the second set of cells, the evacuation structure leading to the purge outlet (120). 8. Module according to one of claims 1 to 7, wherein the first set of cells has the same number of cells as the second set of cells. 9. Module according to one of claims 1 to 8, wherein the first hydrogen injection inlet and the second inlet are respectively provided with a first solenoid valve with proportional opening controllable and a second first solenoid valve with proportional opening steerable. 10. A method of controlling a module according to claim 9, in which: - the respective voltages of the cells of the first set of cells and of the second set of cells are measured, then as a function of the measurement of voltages 5 performed, - the opening amplitude of the first solenoid valve with proportional opening which can be controlled or the second solenoid valve with proportional opening which can be controlled is adjusted. S.58777 1/5 8 14 16