Fuel cell system

Abstract

Fuel Cell System This fuel cell system (1) comprises a fuel cell (10), a hydrogen circuit (20), and a cooling circuit (40). A supply line (21) of the hydrogen circuit is provided with a mixer (21.1) for mixing hydrogen from a reservoir (2) and hydrogen recirculated from an anodic outlet (12) of the cell, as well as a heat exchanger (21.5), upstream of the mixer, for heating the hydrogen from the reservoir. The cooling circuit includes a supply line (41) connecting a radiator (3) to a cooling inlet (15) of the cell, a return line (42) connecting a cooling outlet (16) of the cell to the radiator, and a branch (46) connecting to the return line, forming a closed loop upstream of the radiator.The branch connects the heat exchanger in parallel to the return line so that the heat exchanger transfers heat to the hydrogen from the tank, using a portion of the cooling fluid from the cooling outlet. See Figure 1 for abbreviations.

Description

Title of the invention: Fuel cell system

[0001] The present invention relates to a fuel cell system.

[0002] A fuel cell is a device that generates electricity through an electrochemical reaction between a fuel, in particular dihydrogen, also known simply as hydrogen, and an oxidant, in particular dioxygen, also known simply as oxygen, typically that of the air. We are primarily interested here in proton exchange membrane fuel cells with a solid electrolyte, commonly referred to by the English acronym PEMFC, which usually comprise a stack of individual cells, each constituting an electrochemical generator.

[0003] Schematically, each unit cell comprises two separators, also called polar plates, between which a solid electrolyte is interposed in the form of a proton exchange membrane. The membrane is made, for example, of a sulfonated perfluorinated polymer material. Within each cell, each separator, together with its corresponding membrane, delimits a reactive compartment. One of the two reactive compartments is a cathodic compartment, in which oxygen circulates, while the other reactive compartment is an anodic compartment, in which hydrogen circulates.

[0004] Within the stack, the cells are stacked so as to alternate cathode and anodic compartments. The invention is particularly relevant to fuel cells in which, for two adjacent cells, a separator of one of the two cells is located back-to-back with a separator of the other cell. These two separators together form a bipolar separator, also called a bipolar plate. A cooling compartment, in which a cooling fluid such as glycol water circulates, is generally provided between the two separators of the bipolar separator.

[0005] Hydrogen, air, and coolant are delivered to the fuel cell via dedicated circuits. A cooling circuit, in which the coolant circulates outside the fuel cell, sends the coolant from a fuel cell cooling outlet to a radiator to lower its temperature. The cooling circuit then returns the coolant from the radiator to a fuel cell cooling inlet. A separate hydrogen circuit supplies the fuel cell's anodic inlet with both hydrogen from a hydrogen tank and hydrogen recirculated from a fuel cell anodic outlet. The hydrogen is mixed before entering the fuel cell. In practice, recirculated hydrogen is often warmer and more humid than hydrogen from the storage tank, which creates a risk of water condensation in the hydrogen mixture entering the fuel cell. This can then impair the fuel cell's performance and lifespan. To address this issue, it is known to heat the hydrogen from the storage tank using energy-consuming devices, but this degrades the overall energy efficiency of the system.JP5721451B2, for its part, proposed using a heat exchanger to which a fraction of the coolant flow exiting the fuel cell can be sent, before this fraction is returned downstream of the radiator, while the rest of the coolant flow exiting the fuel cell passes through the radiator, which requires complex regulation of the cooling circuit.

[0006] The aim of the present invention is to propose a fuel cell system, allowing the recirculated hydrogen to be heated in a simple and efficient manner.

[0007] To this end, the invention relates to a fuel cell system, comprising:

[0008] - a fuel cell which is provided with an anodic input, an output anode, a cooling inlet and a cooling outlet,

[0009] - a hydrogen circuit which is adapted to flow hydrogen to the exterior of the fuel cell and which includes:

[0010] - a power supply line which:

[0011] - connects a hydrogen tank to the anodic inlet,

[0012] - is equipped with a mixer adapted for mixing a hydrogen stream from the hydrogen reservoir and a recirculated hydrogen stream from the anodic outlet to send a mixture of said hydrogen streams to the anodic inlet, and

[0013] - is also equipped with a heat exchanger, located upstream of the mixer and adapted to heat the hydrogen stream from the hydrogen tank,

[0014] - a recirculation line that connects the anode outlet to the mixer, and

[0015] - a cooling circuit, which is adapted to allow a cooling fluid to flow division outside the fuel cell and which includes:

[0016] - a supply line that connects a radiator to the cooling inlet,

[0017] - a return line that connects the cooling outlet to the radiator, and

[0018] - a branch, which connects to the return line by forming a closed loop on the return line upstream of the radiator, which branch connects in parallel the heat exchanger to the return line so that the heat exchanger transfers heat to the hydrogen stream from the hydrogen tank, from a fraction of a coolant fluid stream from the cooling outlet.

[0019] One of the ideas behind the invention is to heat the hydrogen from a reservoir of hydrogen before its mixing with the hydrogen that is recirculated from the anodic outlet to the anodic inlet of the fuel cell, by heat transfer from a fraction of the coolant flow exiting the fuel cell. This heat transfer is carried out at a heat exchanger which, upstream of the radiator associated with the cooling circuit, is connected in parallel with the coolant flow exiting the fuel cell. The invention thus provides that the heat exchanger is located on a supply line of the hydrogen circuit, upstream of a mixer of this supply line, at which the recirculated hydrogen is mixed with the hydrogen from the hydrogen tank.The heat exchanger carries the aforementioned fraction of the coolant flow exiting the fuel cell, via a branch that forms a closed loop upstream of the radiator on a hydrogen return line, connecting the fuel cell's coolant outlet to the radiator. When the fuel cell is in operation, i.e., when it is running in steady state, the heat exchanger transfers heat from the fraction of the coolant flow exiting the fuel cell to the hydrogen from the hydrogen tank. This fraction circulates in the aforementioned branch, while the remainder of the coolant flow continues undiverted through the branch, before being joined upstream of the radiator by the aforementioned fraction after it has passed through the heat exchanger.Thus, the entire flow of coolant exiting the fuel cell downstream of the branch can be directed to the radiator, thereby optimizing the performance of the cooling circuit. Before being mixed with the recirculated hydrogen, the hydrogen from the hydrogen tank can be heated efficiently and simply, particularly without the need for energy-intensive heating devices. The temperature of the hydrogen thus heated can advantageously be raised to approximately the temperature of the coolant exiting the fuel cell, and therefore to the temperature of the recirculated hydrogen, or even higher. The performance and durability of the fuel cell in the system according to the invention are therefore remarkable.

[0020] According to additional advantageous features of the fuel cell system according to the invention, taken individually or in any technically possible combination:

[0021] - said fraction represents less than half of the cooling fluid flow from the cooling outlet;

[0022] - the return line is provided with a calibrated flow reducer, and the loop formed by the branch is closed on the return line by being connected upstream and downstream of the flow reducer;

[0023] - the return line is provided with a pump adapted to drive the re fluid cooling in the cooling circuit and the radiator, and the loop formed by the branch is closed on the return line upstream of the pump;

[0024] - the heat exchanger is adapted, by heat transfer from said fraction of the cooling fluid flow from the cooling outlet, to raise the temperature of the hydrogen flow from the hydrogen tank to a value substantially equal to the temperature of the cooling fluid flow from the cooling outlet;

[0025] - the cooling circuit also includes a deionization line, which connects the supply line to the return line and which is equipped with a deionization device suitable for deionizing and then sending into the return line a fraction of a flow of cooling fluid flowing in the supply line, and the loop formed by the branch is closed on the return line downstream of the connection of the deionization line to the return line;

[0026] - the cooling circuit also includes (i) a bypass line which connects the return line to the supply line without passing through the radiator and (ii) a control device, such as a three-way valve, suitable for controlling the flow of the cooling fluid in the radiator and in the bypass line, and the loop formed by the branch is closed on the return line upstream of the connection of the bypass line to the return line;

[0027] - the mixer is a Venturi ejector which is adapted to drive into the line of recirculation the flow of hydrogen recirculated from the anodic outlet, by Venturi effect.

[0028] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the drawings in which [Fig.1] [Fig.1] is a diagram of a fuel cell system according to the invention.

[0029] Figure 1 shows a fuel cell system 1 which is, for example, intended to be integrated into an electric motor vehicle, so that the fuel cell system 1 produces electrical energy to power the aforementioned electric motor.

[0030] The fuel cell system 1 includes a fuel cell 10 in which fluids circulate for the purposes of the operation of the fuel cell 10. Thus, during the operation of the fuel cell 10, the latter is supplied, at the same time, with a fuel gas, typically pure dihydrogen, more commonly called "hydrogen" for the sake of simplicity, with an oxidizing gas, typically dioxygen from the air, more commonly called "oxygen" for the sake of simplicity, and with a cooling fluid, for example glycol water.

[0031] In practice, the fuel cell 10 is equipped for this purpose: - an anodic inlet 11 through which the fuel cell 10 is intended to to be supplied with hydrogen intended to react inside the fuel cell, - an anodic outlet 12 through which the fuel cell 10 is intended to discharge hydrogen that has not been consumed inside the fuel cell, - a cathode inlet 13 through which the fuel cell 10 is intended to be supplied with oxygen, typically oxygen from the air, intended to react inside the fuel cell, - a cathode outlet 14 through which the fuel cell 10 is intended to expel oxygen not consumed inside the fuel cell, typically mixed with the other components of the air supplying the fuel cell, - a cooling inlet 15 through which the fuel cell 10 is intended to receive cooling fluid, and - a cooling outlet 16 through which the fuel cell 10 is intended to discharge cooling fluid.

[0032] As schematically represented in [Fig. 1], the fuel cell 10 generally comprises a stack 17 of electrochemical cells, each having an anodic compartment and a cathodic compartment, separated from each other by a proton exchange membrane. Depending on the direction in which the electrochemical cells of the stack 17 are stacked, a cooling compartment is interposed between the electrochemical cells of each pair of adjacent electrochemical cells. In practice, the fuel cell 10 comprises an integer number N of electrochemical cells, N preferably being between one and several hundred.

[0033] When the fuel cell 10 is operating in steady state, hydrogen feeds the anodic compartments via the anodic inlet 11, while at the same time, oxygen, typically oxygen from the air, feeds the cathodic compartments via the cathodic inlet 13. The hydrogen not consumed in the anodic compartments is discharged from the anodic compartments via the anodic outlet 12, typically mixed with nitrogen, while at the same time, the oxygen not consumed in the cathodic compartments is discharged from the cathodic compartments via the cathodic outlet 14, typically mixed with the other components of the air that fed these cathodic compartments.It is understood that the respective anodic compartments of the stack 17 jointly form an anode of the fuel cell 10, while the respective cathodic compartments of this stack jointly form a cathode of the fuel cell.

[0034] Also when the fuel cell 10 is operating in steady state, coolant supplies, via the cooling inlet 15, the cooling compartments, from which the coolant is discharged, via the cooling outlet 16, the coolant having, at the cooling outlet 16, a temperature higher than that of the coolant at the cooling inlet 15.

[0035] Regardless of the embodiment of the fuel cell 10, the fuel cell system 1 includes a hydrogen circuit 20, an air circuit 30 and a cooling circuit 40, which are adapted to allow hydrogen, air and cooling fluid to flow out of the fuel cell 10, respectively.

[0036] As schematically represented in [Fig. 1], the hydrogen circuit 20 comprises a supply line 21 which connects a hydrogen reservoir 2 to the anodic inlet 11 so as to be able to supply the fuel cell 10 with hydrogen from the hydrogen reservoir 2. When the fuel cell is operating in steady state, hydrogen from the hydrogen reservoir 2 flows in the supply line 21 from the hydrogen reservoir 2 to the anodic inlet 11. The supply line 21 thus has an upstream end, which opens into the hydrogen reservoir 2, and a downstream end, which opens into the anodic inlet 11.

[0037] In practice, the hydrogen tank 2 is a pressurized tank which is for example carried on board the vehicle mentioned above.

[0038] As schematically represented in [Fig. 1], the feed line 21 is provided with a mixer 21.1 which allows two separate hydrogen streams to be mixed, namely a hydrogen stream, denoted H1, which comes from the hydrogen reservoir 2, and a hydrogen stream, denoted H2, which is recirculated from the anodic outlet 12. In addition to being adapted to mix the hydrogen streams H1 and H2, the mixer 21.1 is adapted to send the mixture of these hydrogen streams, denoted H3, to the anodic inlet 11. When the fuel cell 10 is operating in steady state, the hydrogen stream H1 from the hydrogen reservoir 2 flows in the feed line 21 from the hydrogen reservoir 2 to the mixer 21.1, while the hydrogen stream H3, resulting from the mixing of the hydrogen streams H1 and H2, flows in the supply line 21 from the mixer 21.1 to the anode inlet 11.

[0039] Before considering the rest of the supply line 21, it should be noted that, in connection with the mixer 21.1, the hydrogen circuit 20 includes a recirculation line 22 which connects the anodic outlet 11 to the mixer 21.1 so as to be able to remove from the fuel cell 10 hydrogen that has not been consumed inside the latter and to make this hydrogen flow from the anodic outlet 11 to the mixer 21.1. The recirculation line 22 thus has an upstream end, which opens into the anodic outlet 12, and a downstream end, which opens into the mixer 21.1. When the fuel cell 10 is operating in steady state, hydrogen from the anodic outlet 12 flows in the recirculation line 22 from the anodic outlet 12 to the mixer 21.1, forming, in a downstream terminal part of the recirculation line 22, the flow of hydrogen H2 recirculated from the anodic outlet 12. The recirculation line 22 prevents the release, outside the fuel cell system 1, of hydrogen not consumed by the fuel cell 10, by recirculating, towards the anodic inlet 11, hydrogen rejected by the fuel cell 10 at its anodic outlet 12.This hydrogen recirculation is advantageous because it improves the performance of the fuel cell 10 without increasing hydrogen consumption. In particular, this recirculation ensures a sufficient flow of hydrogen within the anodic compartments of the fuel cell 10 to prevent any accumulation of liquid water in the anodic compartments and thus avoid local hydrogen shortages, which consequently ensures optimal efficiency and durability of the fuel cell 10.

[0040] In practice, the recirculation line 22 is provided with a separator 22.1 which allows a discharge stream, which exits the fuel cell 10 at the anodic outlet 12, to be separated into two distinct streams, namely the hydrogen H2 stream recirculated from the anodic outlet 12 and a purge stream, which is evacuated from the recirculation line 22 by a purge line 50. The separator 22.1 thus allows a part of the gaseous hydrogen contained in the discharge stream from the anodic outlet 12 to be separated from the rest of this discharge stream, namely liquid water and nitrogen, mixed with hydrogen. The gaseous hydrogen, which is separated from the aforementioned rejection stream by the separator 22.1, constitutes the recirculated H2 hydrogen stream from the anodic outlet 12. In practice, the separator 22.1 is based on a technology known in itself, which will not be detailed further here.

[0041] In a preferred embodiment, the mixer 21.1 is a Venturi ejector that draws the recirculated hydrogen H2 flow from the anodic outlet 12 into the recirculation line 22 by means of the Venturi effect. Thus, the recirculation of hydrogen via the recirculation line 22 is controlled by the Venturi effect produced by this Venturi ejector.

[0042] Returning now to the description of the supply line 21, in the embodiment considered here, the latter is provided, upstream of the mixer 21.1: - with a flow control valve 21.2, which allows the flow in the supply line 21 to be controlled and the flow rate to be adjusted. of hydrogen H1 from hydrogen tank 2, this flow control valve 21.2 being typically a proportional valve, specifically designed to deliver a flow proportional to its opening, - a safety valve 21.3 which allows "on / off" control of the flow, in the supply line 21, of the hydrogen flow H1 from the hydrogen tank 2, and - a filtering device 21.4 which purifies the hydrogen flow H1 from the hydrogen tank 2.

[0043] The flow control valve 21.2, the safety valve 21.3 and the filtering device 21.4 are arranged in series on the supply line 21.

[0044] Upstream of the mixer 21.1, or, as here, upstream of the flow control valve 21.2, the safety valve 21.3 and the filtering device 21.4, the supply line 21 is also provided with a heat exchanger 21.5 which allows the hydrogen flow H1 from the hydrogen tank 2 to be heated in the supply line 21. This heat exchanger 21.5 will be described in more detail below.

[0045] The air circuit 30, for its part, comprises a supply line 31, which connects to the cathode inlet 13 so as to supply the fuel cell 10 with air, more precisely with oxygen from the air, and an exhaust line 32, which is connected to the cathode outlet 14 so as to exhaust air containing oxygen that has not been consumed inside the fuel cell from the fuel cell 10. The specific features of the supply line 31 and the exhaust line 32, as well as, more generally, the specific features of the air circuit 30, are not limiting to the invention and will therefore not be described further here.

[0046] As can be clearly seen in [Fig.1], the cooling circuit 40 is associated with a radiator 3 which cools the cooling fluid of the cooling circuit 40 by heat exchange with the ambient air. The radiator 3, whose specifications are not limiting, is for example mounted on the vehicle mentioned above.

[0047] More specifically, the cooling circuit 40 comprises: - a supply line 41 which connects the radiator 3 to the cooling inlet 15 so as to supply the fuel cell 10 with cooling fluid that has been cooled by the radiator 3, and - a return line 42 which connects the cooling outlet 16 to the radiator 3 so as to be able to send to the radiator 3 cooling fluid which has been heated by the fuel cell 10.

[0048] When the fuel cell 10 is operating in steady state, coolant from the radiator 3 flows in the supply line 41 from the radiator 3 to the cooling inlet 15, while coolant exits The fuel cell 10 flows in the return line 42 from the cooling outlet 16 to the radiator 3. The supply line 41 thus has an upstream end, which opens into the radiator 3, and a downstream end, which opens into the cooling inlet 15. The return line 42 has, for its part, an upstream end, which opens into the cooling outlet 16, and a downstream end, which opens into the radiator 3.

[0049] In the embodiment considered here, the supply line 41 is advantageously provided with a filtering device 41.1 which makes it possible to purify the cooling fluid circulating in the cooling circuit 40.

[0050] Also in the embodiment considered here, the cooling circuit 40 further comprises a bypass line 43 which connects the return line 42 to the supply line 41 without passing through the radiator 3. The bypass line 43 thus allows the cooling fluid to flow from the return line 42 to the supply line 41 by bypassing, that is to say, by going around, the radiator 3. To control the distribution of the flow of the cooling fluid in the radiator 3 and in the bypass line 43, the cooling circuit 40 comprises a three-way valve 44 adapted to control and adjust the flow rate of the cooling fluid in both the radiator 3 and in the bypass line 43.In the embodiment considered here, the three-way valve 44 is disposed on the supply line 41, at the connection of the bypass line 43 to the supply line 41: the cooling fluid, exiting the three-way valve 44 and sent to the cooling inlet 15 via the part of the supply line 41, extending downstream of the three-way valve 44, has a flow rate corresponding to the sum of two flow rates, each potentially adjustable to zero by the three-way valve 44, namely the flow rate of the cooling fluid entering the three-way valve 44 from the bypass line 43 and the flow rate of the cooling fluid entering the three-way valve 44 from the radiator 3.

[0051] In practice, and in a way known in itself in the field, other forms of embodiment than the three-way valve 44 described above are conceivable as control devices capable of controlling the distribution of the flow of the cooling fluid in the radiator 3 and in the bypass line 43.

[0052] In all cases, the coolant flow in the cooling circuit 40 and the radiator 3 is advantageously carried out by a pump 42.1 which is provided with the return line 42. The pump 42.1 is thus located, on the return line 42, upstream of the radiator 3, being located here upstream of the connection of the bypass line 43 to the return line 42. The specifications of the pump 42.1 are not limiting.

[0053] In the embodiment considered here, the cooling circuit 40 comprises advantageously a deionization line 45 that connects the supply line 41 to the return line 42 so as to allow coolant to flow from the supply line 41 to the return line 42. This deionization line 45 is provided with a deionization device 45.1 adapted to deionize a fraction of a flow of coolant flowing in the supply line 41 and to send this fraction to the return line 42. This deionization device 45.1, which is based on a known technology per se, captures ions suspended in the coolant of the cooling circuit 40 in order to extract excess ions generated during the operation of the fuel cell 10 and to maintain a low level of electrical conductivity for the coolant of the cooling circuit 40. The deionization device 45.1 typically includes an ion capture cartridge 45.2.

[0054] In all cases, the cooling circuit 40 includes a branch 46 specifically dedicated to the heat exchanger 21.5 of the supply line 21 of the hydrogen circuit 20.

[0055] More specifically, as clearly shown in [Fig. 1], branch 46 connects to the return line 42 by forming a closed loop on the return line 42, upstream of the radiator 3, preferably upstream of the pump 42.1 and, as here, downstream of the connection of the deionization line 45 to the return line 42. The closed loop formed by branch 46 thus has two ends, each opening into the return line 42, and these openings are distinct from each other along the return line 42: one of these two ends is an upstream end 46.1, which is located here downstream of the connection of the deionization line 45 to the return line 42, while the other end is a downstream end 46.2, which is located both downstream of the upstream end 46.1 and upstream of the radiator 3 and, as here, of the pump 42.1.

[0056] In addition, branch 46 connects in parallel the heat exchanger 21.5 to the return line 42: branch 46 thus extends from its upstream end 46.1 to its downstream end 46.2 by passing through the heat exchanger 21.5 so as to allow the cooling fluid to flow from the upstream end 46.1 to the downstream end 46.2 of branch 46, passing through the heat exchanger 21.5.

[0057] When the fuel cell 10 is operating in steady state, the coolant from the cooling outlet 16 flows into the return line 42, forming, upstream of branch 46, a coolant flow CL. Furthermore, at the upstream end 46.1 of branch 46, a fraction C2 of this coolant flow Cl is diverted into branch 46, in which this fraction C2 of the coolant flow Cl flows, passing through the heat exchanger 21.5, before returning to the return line 42 at the downstream end 46.2 from branch 46, where this fraction C2 mixes with the cooling fluid flowing in the return line 42 to form a cooling fluid flow having the same flow rate as the Cl flow. In this way, all of the cooling fluid exiting the fuel cell 10, via the cooling outlet 16, can be sent to the radiator 3, without the presence of the heat exchanger 21.5 causing the C2 fraction of the cooling fluid Cl flow to bypass the radiator 3. The performance of the cooling circuit 40 is thus optimized.

[0058] The heat exchanger 21.5 is adapted to transfer heat from fraction C2 of the cooling fluid stream Cl from the cooling outlet 16 to the hydrogen stream passing through this heat exchanger 21.5, in other words, to the hydrogen stream H1 from the hydrogen reservoir 2. Thus, when the fuel cell 10 is operating in steady state, the hydrogen stream H1 from the hydrogen reservoir 2 passes through the heat exchanger 21.5, where the latter heats this hydrogen stream H1 by transferring heat to it. This heat is also delivered at the heat exchanger 21.5 by fraction C2 of the cooling fluid stream Cl, this fraction C2 passing through the heat exchanger 21.5 due to its flow in the branch 46. In this way, the temperature of the hydrogen stream H1 is increased by the heat exchanger 21.5. that is, before this flow of hydrogen H1 reaches the mixer 21.1.The result is that the mixing between the hydrogen stream Hl, thus heated by the heat exchanger 21.5, and the hydrogen stream H2 recirculated from the anodic outlet 12, is carried out in a way that limits, or even avoids, water condensation.

[0059] According to a preferred sizing, the heat exchanger 21.5 is adapted, by transferring heat from fraction C2 of the cooling fluid stream Cl from the cooling outlet 16, to raise the temperature of the hydrogen stream Hl from the hydrogen reservoir 2 to a value substantially equal to the temperature of the cooling fluid stream CL. In other words, the temperature to which the hydrogen stream Hl is thus raised by the heat exchanger 21.5 corresponds to the maximum temperature of the cooling fluid exiting the fuel cell 10. This promotes the fact that, at the mixer 21.1, the temperature of the hydrogen stream Hl is equal to or greater than the temperature of the hydrogen stream H2. The risk of water condensation at the outlet of the mixer 21.1 is thus avoided.

[0060] In all cases, it is understood that the heat exchanger 21.5 is a passive device, as opposed to heating devices that consume energy to produce heat. Thus, the overall energy efficiency of the fuel cell system 1 is optimized.

[0061] In practice, the fraction C2 of the cooling fluid flow Cl represents prefer normally less than half of the latter, or even less than 10% of the cooling fluid flow Cl. In this way, the pressure losses in the cooling circuit 40 are limited.

[0062] To size the fraction C2 of the cooling fluid flow Cl and force it to flow into the branch 46, the return line 42 is advantageously provided with a calibrated flow reducer 42.2, which is located both downstream of the upstream end 46.1 of the branch 46 and upstream of the downstream end 46.2 of this branch 46. Thus, the loop formed by the branch 46 is closed on the return line 42 upstream and downstream of the flow reducer 42.2. The implementation of this flow reducer 42.2 is simple and economical.

[0063] Finally, various modifications and variants to the fuel cell system 1, as well as to its operating method, described so far are conceivable.

Claims

Demands

1. Fuel cell system (1), comprising: - a fuel cell (10) which is provided with an anodic inlet (11), an anodic outlet (12), a cooling inlet (15) and a cooling outlet (16), - a hydrogen circuit (20) which is adapted to discharge hydrogen out of the fuel cell (10) and which includes: - a feed line (21) which: - connects a hydrogen reservoir (2) to the anodic inlet (11), - is provided with a mixer (21.1) adapted to mix a stream of hydrogen (H1) from the hydrogen reservoir (2) and a stream of hydrogen (H2) recirculated from the anodic outlet (12) and to send a mixture (H3) of said hydrogen streams to the anodic inlet (11), and - is also provided with a heat exchanger (21.5), located upstream of the mixer (21.1) and adapted to heat the hydrogen (Hl) stream from the hydrogen tank (2), - a recirculation line (22) which connects the anodic outlet (12) to the mixer (21.1), and - a cooling circuit (40), which is adapted to carry a cooling fluid outside the fuel cell (10) and which includes: - a supply line (41) which connects a radiator (3) to the cooling inlet (15), - a return line (42) which connects the cooling outlet (16) to the radiator (3), and - a branch (46), which connects to the return line (42) by forming a closed loop on the return line (42) upstream of the radiator (3), which branch (46) connects in parallel to the heat exchanger (21.5) to the return line (42) so that the heat exchanger transfers heat to the hydrogen stream (Hl) from the hydrogen tank (2), from a fraction (C2) of a cooling fluid stream (Cl) from the cooling outlet (16).

2. Fuel cell system according to claim 1, wherein said fraction (C2) represents less than half of the coolant fluid flow (Cl) from the coolant outlet (16).

3. Fuel cell system according to claim 1 or 2, in which the return line (42) is provided with a calibrated flow reducer (42.2), and in which the loop formed by the branch (46) is closed on the return line (42) by being connected upstream and downstream of the flow reducer (42.2).

4. Fuel cell system according to any one of the preceding claims, wherein the return line (42) is provided with a pump (42.1) adapted to drive the coolant into the cooling circuit (40) and the radiator (3), and wherein the loop formed by the branch (42) is closed on the return line (42) upstream of the pump (42.1).

5. Fuel cell system according to any one of the preceding claims, wherein the heat exchanger (21.5) is adapted, by heat transfer from said fraction (C2) of the coolant flow (Cl) from the cooling outlet (16), to raise the temperature of the hydrogen flow (Hl) from the hydrogen reservoir (2) to a value substantially equal to the temperature of the coolant flow (Cl) from the cooling outlet (16).

6. Fuel cell system according to any one of the preceding claims, wherein the cooling circuit (40) also includes a deionization line (45), which connects the supply line (41) to the return line (42) and which is provided with a deionization device (45.1) adapted to deionize and then send into the return line a fraction of a flow of cooling fluid flowing in the supply line (41), and wherein the loop formed by the branch (46) is closed on the return line (42) downstream of the connection of the deionization line (45) to the return line.

7. A fuel cell system according to any one of the preceding claims, wherein the cooling circuit also includes: - a bypass line (43) that connects the return line (42) to the supply line (41) without passing through the radiator (3), and - a control device, such as a three-way valve (44), adapted to control the flow of the cooling fluid in the radiator (3) and in the bypass line (43), and in which the loop formed by the branch (46) is closed on the return line (42) upstream of the connection of the bypass line (43) to the return line.

8. Fuel cell system according to any one of the preceding claims, wherein the mixer (21.1) is a Venturi ejector which is adapted to drive into the recirculation line (22) the flow of hydrogen (H2) recirculated from the anodic outlet (12), by Venturi effect.

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