Fuel cell system
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SYMBIO FRANCE
- Filing Date
- 2024-08-22
- Publication Date
- 2026-07-01
Smart Images
Figure EP2024073603_27022025_PF_FP_ABST
Abstract
Description
[0001] TITLE: Fuel Cell System
[0002] The present invention relates to a fuel cell system.
[0003] A fuel cell is a device for generating electricity by electrochemical reaction between a fuel, in particular dihydrogen, otherwise known more simply as hydrogen, and an oxidant, in particular dioxygen, otherwise known more simply as oxygen, typically that of air. We are primarily interested here in fuel cells of the proton exchange membrane type, with solid electrolyte, commonly designated by the English acronym PEMFC, which usually comprise a stack, otherwise known as a "stack" in English, of unit cells each constituting an electrochemical generator.
[0004] Schematically, each unit cell comprises two separators, also called polar plates, between which is inserted a solid electrolyte 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 delimits with the corresponding membrane a reactive compartment. One of the two reactive compartments is a cathode compartment, in which oxygen circulates, while the other reactive compartment is an anodic compartment, in which hydrogen circulates.
[0005] Within the stack, the cells are stacked so as to alternate the cathode and anode compartments. The invention is particularly relevant to fuel cells in which, for two neighboring cells, a separator of one of the two cells is 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 glycolated water circulates, is generally arranged between the two separators of the bipolar separator.
[0006] Hydrogen, air and coolant are delivered to the fuel cell by respective dedicated circuits. Thus, a cooling circuit, in which the coolant circulates outside the fuel cell, is able to send the coolant from a cooling outlet of the fuel cell to a radiator allowing the temperature of this coolant to be lowered, before the cooling circuit brings the coolant leaving the radiator to a cooling inlet of the fuel cell. Furthermore, a hydrogen circuit makes it possible to supply the anode inlet of the fuel cell with both hydrogen from a hydrogen tank and hydrogen recirculated from an anode outlet of the fuel cell, which are mixed before entering the fuel cell.In practice, recirculated hydrogen is often hotter and more humid than the hydrogen from the hydrogen tank, which poses a risk of water condensation in the hydrogen mixture entering the fuel cell, which can then affect the performance and durability of the fuel cell. To address this problem, it is known to heat the hydrogen from the hydrogen tank using energy-consuming devices, which, however, degrades the energy efficiency of the entire system. For its part, JP5721451 B2 proposed using a heat exchanger to which a fraction of the coolant flow leaving the fuel cell can be sent, before this fraction is returned downstream of the radiator, while the rest of the coolant flow leaving the fuel cell passes through the radiator, which requires complex regulation of the cooling circuit.
[0007] The aim of the present invention is to propose a fuel cell system, making it possible to heat recirculated hydrogen in a simple and efficient manner.
[0008] To this end, the invention relates to a fuel cell system, comprising:
[0009] - a fuel cell which is provided with an anode inlet, an anode outlet, a cooling inlet and a cooling outlet,
[0010] - a hydrogen circuit which is adapted to flow hydrogen outside the fuel cell and which includes:
[0011] - a supply line which:
[0012] - connects a hydrogen tank to the anode inlet,
[0013] - is provided with a mixer adapted to mix a hydrogen flow from the hydrogen tank and a hydrogen flow recirculated from the anode outlet and to send a mixture of said hydrogen flows to the anode inlet, and
[0014] - is also provided with a heat exchanger, arranged upstream of the mixer and adapted to heat the flow of hydrogen from the hydrogen tank,
[0015] - a recirculation line which connects the anode outlet to the mixer, and
[0016] - a cooling circuit, which is adapted to flow a cooling fluid outside the fuel cell and which includes:
[0017] - a supply line which connects a radiator to the cooling inlet,
[0018] - a return line that connects the cooling outlet to the radiator, and
[0019] - 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 flow of hydrogen from the hydrogen tank, from a fraction of a flow of coolant from the cooling outlet.
[0020] One of the ideas underlying the invention is to heat the hydrogen from a hydrogen tank before mixing it with the hydrogen that is recirculated from the anode outlet to the anode inlet of the fuel cell, by heat transfer from a fraction of the coolant flow leaving the fuel cell, this heat transfer being carried out at a heat exchanger which, upstream of the radiator associated with the cooling circuit, is connected in parallel with the coolant flow leaving the fuel cell. The invention thus provides that the heat exchanger is arranged 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 is traversed by the aforementioned fraction of the coolant flow leaving the fuel cell, thanks to a branch which forms, upstream of the radiator, a closed loop on a hydrogen return line, connecting the cooling outlet of the fuel cell to the radiator. When the fuel cell is in service, that is to say when it operates in steady state, the heat exchanger transfers to the hydrogen from the hydrogen tank the heat of the fraction of the coolant flow leaving the fuel cell, this fraction thus circulating in the aforementioned branch, while the rest of the coolant flow flows without being diverted in the branch, before being joined, upstream of the radiator, by the aforementioned fraction after it has passed through the heat exchanger.Thus, the coolant flow leaving the fuel cell can, downstream of the branch, be sent entirely to the radiator, which optimizes the performance of the cooling circuit. In addition, even if the coolant is sent entirely to the radiator, this has no impact on the cooling of the fuel cell, since the branch forms a closed loop on the return line, and not on the supply line, or a loop on the supply and return line. The fact that the branch forms a closed loop on the return line also allows for a hotter coolant than if the coolant came from the supply line. Thus, before being mixed with the recirculated hydrogen, the hydrogen from the hydrogen tank can be heated efficiently and simply, in particular without resorting to energy-consuming heating devices.The temperature of the hydrogen thus heated can advantageously be raised to substantially the temperature of the cooling fluid leaving the fuel cell, and therefore to the temperature of the recirculated hydrogen, or even beyond. The performance and durability of the fuel cell belonging to the system according to the invention are thus remarkable.
[0021] According to additional advantageous characteristics of the fuel cell system according to the invention, taken in isolation or in all technically possible combinations:
[0022] - said fraction represents less than half of the flow of cooling fluid from the cooling outlet;
[0023] - 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;
[0024] - the return line is provided with a pump adapted to drive the cooling fluid into the cooling circuit and the radiator, and the loop formed by the branch is closed on the return line upstream of the pump;
[0025] - the branch is fitted with a calibrated flow reducer;
[0026] - the return line is provided with a pump adapted to drive the cooling fluid into the cooling circuit and the radiator and the loop formed by the branch is closed on the return line by being connected downstream and upstream of the pump;
[0027] - the heat exchanger is adapted, by heat transfer from said fraction of the coolant flow coming from the cooling outlet, to raise the temperature of the hydrogen flow coming from the hydrogen tank to a value substantially equal to the temperature of the coolant flow coming from the cooling outlet;
[0028] - the cooling circuit also includes a deionization line, which connects the supply line to the return line and which is provided with a deionization device adapted to deionize and then send 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;
[0029] - 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 regulating device, such as a three-way valve, adapted to control the flow of the coolant 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; - the mixer is a Venturi ejector which is adapted to drive into the recirculation line the flow of hydrogen recirculated from the anode outlet, by Venturi effect.
[0030] The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings in which [Fig.1] figure 1 is a diagram of a fuel cell system according to the invention.
[0031] 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 operate the aforementioned electric motor.
[0032] The fuel cell system 1 comprises 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 combustible gas, typically pure dihydrogen, more commonly called "hydrogen" for the sake of simplification, with an oxidizing gas, typically dioxygen from the air, more commonly called "oxygen" for the sake of simplification, and with a cooling fluid, for example glycolated water.
[0033] In practice, the fuel cell 10 is provided for this purpose:
[0034] - an anode inlet 11 through which the fuel cell 10 is intended to be supplied with hydrogen intended to react inside the fuel cell,
[0035] - an anode outlet 12 through which the fuel cell 10 is designed to evacuate hydrogen which has not been consumed inside the fuel cell,
[0036] - 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,
[0037] - a cathode outlet 14 through which the fuel cell 10 is designed to evacuate oxygen which has not been consumed inside the fuel cell, typically mixed with the other components of the air supplying the fuel cell,
[0038] - a cooling inlet 15 through which the fuel cell 10 is provided to admit cooling fluid, and
[0039] - a cooling outlet 16 through which the fuel cell 10 is designed to discharge cooling fluid.
[0040] As shown schematically in Figure 1, the fuel cell 10 generally comprises a stack 17 of electrochemical cells which each have an anode compartment and a cathode 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 electrochemical cells adjacent to each other. In practice, the fuel cell 10 comprises an integer N of electrochemical cells, N preferably being between one and several hundred.
[0041] When the fuel cell 10 is operating in steady state, hydrogen feeds, via the anode inlet 11, the anode compartments while, at the same time, oxygen, typically oxygen from the air, feeds, via the cathode inlet 13, the cathode compartments. The hydrogen that has not been consumed in the anode compartments is evacuated, via the anode outlet 12, from the anode compartments, typically being mixed with nitrogen, while, at the same time, the oxygen that has not been consumed in the cathode compartments is evacuated, via the cathode outlet 14, from the cathode compartments, typically being mixed with the other components of the air that fed these cathode compartments.It is understood that the respective anode compartments of the stack 17 jointly form an anode of the fuel cell 10 while the respective cathode compartments of this stack jointly form a cathode of the fuel cell.
[0042] Also when the fuel cell 10 is operating in steady state, cooling fluid is supplied, via the cooling inlet 15, to the cooling compartments, from which the cooling fluid is discharged, via the cooling outlet 16, the cooling fluid having, at the cooling outlet 16, a temperature higher than that which the cooling fluid has at the cooling inlet 15.
[0043] Regardless of the embodiment of the fuel cell 10, the fuel cell system 1 comprises a hydrogen circuit 20, an air circuit 30 and a cooling circuit 40, which are adapted to flow outside the fuel cell 10, respectively, hydrogen, air and cooling fluid.
[0044] As shown schematically in Figure 1, the hydrogen circuit 20 comprises a supply line 21 which connects a hydrogen tank 2 to the anode inlet 11 so as to be able to supply the fuel cell 10 with hydrogen from the hydrogen tank 2. When the fuel cell is operating in steady state, hydrogen from the hydrogen tank 2 flows in the supply line 21 from the hydrogen tank 2 to the anode inlet 11. The supply line 21 thus has an upstream end, which opens into the hydrogen tank 2, and a downstream end, which opens into the anode inlet 11. In practice, the hydrogen tank 2 is a pressurized tank which is for example on board the vehicle mentioned above.
[0045] As shown schematically in Figure 1, the supply line 21 is provided with a mixer 21.1 which makes it possible to mix two separate hydrogen flows, namely a hydrogen flow, which is denoted H1 and which comes from the hydrogen tank 2, and a hydrogen flow, which is denoted H2 and which is recirculated from the anode outlet 12. In addition to being adapted to mix the hydrogen flows H1 and H2, the mixer 21.1 is adapted to send the mixture of these hydrogen flows, denoted H3, to the anode inlet 11. When the fuel cell 10 operates in steady state, the hydrogen flow H1 coming from the hydrogen tank 2 flows in the supply line 21 from the hydrogen tank 2 to the mixer 21.1, while the hydrogen flow H3, resulting from the mixing of the hydrogen flows H1 and H2, flows into the feed line 21 from mixer 21.1 to anode input 11.
[0046] Before looking at the rest of the supply line 21, it will be noted that, in connection with the mixer 21.1, the hydrogen circuit 20 comprises a recirculation line 22 which connects the anode outlet 11 to the mixer 21.1 so as to be able to evacuate from the fuel cell 10 hydrogen which has not been consumed inside the latter and to cause this hydrogen to flow from the anode outlet 11 to the mixer 21.1. The recirculation line 22 thus has an upstream end, which opens into the anode outlet 12, and a downstream end, which opens into the mixer 21.1. When the fuel cell 10 operates in steady state, hydrogen from the anode outlet 12 flows into the recirculation line 22 from the anode outlet 12 to the mixer 21.1, forming, in a downstream terminal portion of the recirculation line 22, the flow of hydrogen H2 recirculated from the anode outlet 12.The recirculation line 22 makes it possible to avoid discharging, outside the fuel cell system 1, hydrogen that has not been consumed by the fuel cell 10, by recirculating, towards the anode inlet 11, hydrogen discharged by the fuel cell 10 at its anode outlet 12. This recirculation of hydrogen is advantageous because it makes it possible to improve the performance of the fuel cell 10 without increasing the consumption of hydrogen. In particular, this recirculation makes it possible to ensure a sufficient flow of hydrogen within the anode compartments of the fuel cell 10 to avoid any accumulation of liquid water in the anode compartments and thus avoid local shortages of hydrogen, which consequently makes it possible to ensure optimal efficiency and durability of the fuel cell 10.
[0047] In practice, the recirculation line 22 is provided with a separator 22.1 which makes it possible to separate a discharge stream, which leaves the fuel cell 10 at the anode outlet 12, into two separate streams, namely the stream of hydrogen H2 recirculated from the anode outlet 12 and a purge stream, which is evacuated from the recirculation line 22 by a purge line 50. The separator 22.1 thus makes it possible to separate a portion of the gaseous hydrogen contained in the discharge stream from the anode outlet 12, from the rest of this discharge stream, namely liquid water and nitrogen, mixed with hydrogen. The gaseous hydrogen, which is separated from the aforementioned reject stream by the separator 22.1, constitutes the stream of hydrogen H2 recirculated from the anode outlet 12. In practice, the separator 22.1 is based on technology known per se, which will not be detailed further here.
[0048] According to a preferred embodiment, the mixer 21.1 is a Venturi ejector which makes it possible to drive the flow of hydrogen H2 recirculated from the anode outlet 12 into the recirculation line 22, by the Venturi effect. Thus, the recirculation of hydrogen via the recirculation line 22 is controlled by the Venturi effect produced by this Venturi ejector.
[0049] Returning now to the description of the supply line 21, the latter is, in the embodiment considered here, provided, upstream of the mixer 21.1:
[0050] - a flow control valve 21.2, which makes it possible to control the flow, in the supply line 21, and to adjust the flow rate of the hydrogen flow H1 from the hydrogen tank 2, this flow control valve 21.2 typically being a proportional valve, in particular designed to deliver a flow rate proportional to its opening,
[0051] - a safety valve 21.3 which allows the flow, in the supply line 21, of the hydrogen flow H1 from the hydrogen tank 2 to be controlled “on-off”, and
[0052] - a filtering device 21.4 which purifies the flow of hydrogen H1 from the hydrogen tank 2.
[0053] 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.
[0054] Upstream of the mixer 21.1, or even, 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 makes it possible to heat, in the supply line 21, the flow of hydrogen H1 coming from the hydrogen tank 2. This heat exchanger 21.5 will be described in more detail below.
[0055] For its part, the air circuit 30 comprises a supply line 31, which is connected to the cathode inlet 13 so as to be able to supply the fuel cell 10 with air, more precisely with the oxygen in the air, and an evacuation line 32, which is connected to the cathode outlet 14 so as to be able to evacuate from the fuel cell 10 air containing oxygen that has not been consumed inside the fuel cell. The specific features of the supply line 31 and the evacuation line 32, as well as, more generally, the specific features of the air circuit 30 are not limiting of the invention and will therefore not be described here further.
[0056] As clearly visible in Figure 1, the cooling circuit 40 is associated with a radiator 3 which makes it possible to cool, by heat exchange with the ambient air, the cooling fluid of the cooling circuit 40. The radiator 3, the specific features of which are not limiting, is for example installed on the vehicle mentioned above.
[0057] More specifically, the cooling circuit 40 comprises:
[0058] - a supply line 41 which connects the radiator 3 to the cooling inlet 15 so as to be able to supply the fuel cell 10 with cooling fluid having been cooled by the radiator 3, and
[0059] - 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.
[0060] 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 leaving 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.
[0061] 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.
[0062] 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 makes it possible to cause the cooling fluid to flow from the return line 42 to the supply line 41 by bypassing, i.e. bypassing, 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 both in the radiator 3 and in the bypass line 43.In the embodiment considered here, the three-way valve 44 is arranged on the supply line 41, at the connection of the bypass line 43 to the supply line 41: the cooling fluid, leaving 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.
[0063] In practice, and in a manner known per se in the field, other embodiments than the three-way valve 44 described above are conceivable as regulating devices capable of controlling the distribution of the flow of the cooling fluid in the radiator 3 and in the bypass line 43.
[0064] In all cases, the driving of the cooling fluid in the cooling circuit 40 and the radiator 3 is advantageously operated by a pump 42.1 with which the return line 42 is provided. The pump 42.1 is thus located, on the return line 42, upstream of the radiator 3, being here located upstream of the connection of the bypass line 43 to the return line 42. The specific features of the pump 42.1 are not limiting.
[0065] In the embodiment considered here, the cooling circuit 40 advantageously comprises a deionization line 45 which connects the supply line 41 to the return line 42 so as to be able to cause cooling fluid 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 cooling fluid flowing in the supply line 41 and to send this fraction into the return line 42. This deionization device 45.1, which is based on technology known per se, captures ions suspended in the cooling fluid 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 cooling fluid of the cooling circuit 40.The deionization device 45.1 typically comprises an ion capture cartridge 45.2.
[0066] In all cases, the cooling circuit 40 comprises a branch 46 specifically dedicated to the heat exchanger 21.5 of the supply line 21 of the hydrogen circuit 20.
[0067] More precisely, as clearly visible in Figure 1, the 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 the branch 46 thus has two ends which each open into the return line 42, and this in a manner distinct from one another along the return line 42: one of these two ends is an upstream end 46.1, which is here located 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
[0068] 46.1 and upstream of the radiator 3 and, as here, of the pump 42.1.
[0069] In addition, the branch 46 connects the heat exchanger 21.5 in parallel to the return line 42: the branch 46 thus extends from its upstream end 46.1 to its downstream end 46.2, passing through the heat exchanger 21.5 so as to be able to cause cooling fluid to flow from the upstream end 46.1 to the downstream end.
[0070] 46.2 of branch 46, passing through heat exchanger 21.5.
[0071] 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 the branch 46, a coolant flow C1. In addition, at the upstream end 46.1 of the branch 46, a fraction C2 of this coolant flow C1 is diverted into the branch 46 in which this fraction C2 of the coolant flow C1 flows, passing into the heat exchanger 21.5, before returning to the return line 42 at the downstream end 46.2 of the branch 46, where this fraction C2 mixes with the coolant flowing in the return line 42 to form a coolant flow having the same flow rate as the flow C1.In this way, all of the coolant leaving 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 a bypass of the radiator 3 for the fraction C2 of the coolant flow C1. The performance of the cooling circuit 40 is thus optimized.
[0072] The heat exchanger 21.5 is adapted to transfer heat, from the fraction C2 of the coolant flow C1 coming from the cooling outlet 16, to the hydrogen flow passing through this heat exchanger 21.5, in other words to the hydrogen flow H1 coming from the hydrogen tank 2. Thus, when the fuel cell 10 operates in steady state, the hydrogen flow H1 coming from the hydrogen tank 2 passes through the heat exchanger 21.5 at the level of which the latter heats this hydrogen flow H1 by transferring heat to it which is delivered, also at the level of the heat exchanger 21.5, by the fraction C2 of the coolant flow C1, 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 flow H1 is increased by the heat exchanger 21.5, that is, before this flow of hydrogen H1 reaches the mixer 21.1.As a result, the mixing between the hydrogen flow H1, thus heated by the heat exchanger 21.5, and the hydrogen flow H2 recirculated from the anode outlet 12, is carried out while limiting, or even avoiding, the condensation of water.
[0073] According to a preferred dimensioning, the heat exchanger 21.5 is adapted, by heat transfer from the fraction C2 of the coolant flow C1 coming from the cooling outlet 16, to raise the temperature of the hydrogen flow H1 coming from the hydrogen tank 2 to a value substantially equal to the temperature of the coolant flow C1. In other words, the temperature to which the hydrogen flow H1 is thus brought by the heat exchanger 21.5 corresponds to the maximum temperature of the coolant leaving the fuel cell 10. This promotes the fact that, at the mixer 21.1, the temperature of the hydrogen flow H1 is equal to or greater than the temperature of the hydrogen flow H2. The risk of water condensation at the outlet of the mixer 21.1 is thus avoided.
[0074] In any case, it is understood that the heat exchanger 21.5 is a passive material, as opposed to heating materials that consume energy to produce heat. Thus, the overall energy efficiency of the fuel cell system 1 is optimized.
[0075] In practice, the fraction C2 of the cooling fluid flow C1 preferably represents less than half of the latter, or even less than 10% of the cooling fluid flow C1. In this way, the pressure losses in the cooling circuit 40 are limited.
[0076] To size the fraction C2 of the coolant flow C1 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.
[0077] Finally, various arrangements and variants of the fuel cell system 1, as well as its operating method, described so far are conceivable.
[0078] Figure 2 shows a fuel cell system 100, as an alternative embodiment to the system 1 described previously.
[0079] Elements of system 100 similar to system 1 are referenced with the same reference signs and are not described again in detail. Fuel cell system 100 includes a branch 146, which replaces branch 46. Branch 146 is similar to branch 46 except for the differences described below.
[0080] The branch 146 comprises two ends, an upstream end 146.1 and a downstream end 146.2. The upstream end 146.1 is located downstream of the pump 42.1 and the downstream end 146.2 is located upstream of the pump 42.1. Thus, the branch 146 forms a closed loop on the return line 42 by being connected downstream and upstream of the pump 42.1.
[0081] In the example of Figure 2, the branch 146 is provided with a flow reducer 146.3. Advantageously, the flow reducer 146.3 is calibrated. The flow reducer 146.3 advantageously serves to size the fraction C2 of the coolant flow C1 and to force it to flow in the branch 146. Advantageously, in the case where the branch 146 is provided with the flow reducer 146.3, the branch 42 does not include a flow reducer 42.2. Any feature described for an embodiment or variant in the above can be implemented for the other embodiments and variants described previously, as long as technically feasible.
Claims
CLAIMS 1. Fuel cell system (1; 100), comprising: - a fuel cell (10) which is provided with an anode inlet (11), an anode outlet (12), a cooling inlet (15) and a cooling outlet (16), - a hydrogen circuit (20) which is adapted to flow hydrogen outside the fuel cell (10) and which includes: - a supply line (21) which: - connects a hydrogen tank (2) to the anode inlet (11), - is provided with a mixer (21.1) adapted to mix a hydrogen flow (H1) from the hydrogen tank (2) and a hydrogen flow (H2) recirculated from the anode outlet (12) and to send a mixture (H3) of said hydrogen flows to the anode inlet (11), and - is also provided with a heat exchanger (21.5), arranged upstream of the mixer (21.1) and adapted to heat the flow of hydrogen (H1) from the hydrogen tank (2), - a recirculation line (22) which connects the anode outlet (12) to the mixer (21.1), and - a cooling circuit (40), which is adapted to flow 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; 146), 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; 146) connects in parallel the heat exchanger (21.5) to the return line (42) so that the heat exchanger transfers heat to the hydrogen flow (H1) coming from the hydrogen tank (2), from a fraction (C2) of a coolant flow (C1) coming from the cooling outlet (16).
2. Fuel cell system (1; 100) according to claim 1, wherein said fraction (C2) represents less than half of the flow of cooling fluid (C1) from the cooling outlet (16).
3. Fuel cell system (1) according to one of claims 1 or 2, wherein the return line (42) is provided with a calibrated flow reducer (42.2), and wherein 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 (1) according to any one of the preceding claims, wherein the return line (42) is provided with a pump (42.1) adapted to drive the cooling fluid into the cooling circuit (40) and the radiator (3), and wherein the loop formed by the branch (46) is closed on the return line (42) upstream of the pump (42.1).
5. Fuel cell system (100) according to one of claims 1 or 2, wherein the branch (146) is provided with a calibrated flow reducer (146.3).
6. Fuel cell system (100) according to one of claims 1, 2 or 5, wherein the return line (42) is provided with a pump (42.1) adapted to drive the cooling fluid into the cooling circuit (40) and the radiator (3), and wherein the loop formed by the branch (146) is closed on the return line (42) by being connected downstream and upstream of the pump (42.1).
7. Fuel cell system (1; 100) 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 (C1) coming from the cooling outlet (16), to raise the temperature of the hydrogen flow (H1) coming from the hydrogen tank (2) to a value substantially equal to the temperature of the coolant flow (C1) coming from the cooling outlet (16).
8. Fuel cell system (1; 100) 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 in which the loop formed by the branch (46; 146) is closed on the return line (42) downstream of the connection of the deionization line (45) to the return line.
9. Fuel cell system (1; 100) according to any one of the preceding claims, wherein the cooling circuit also includes: - a bypass line (43) which connects the return line (42) to the supply line (41) without passing through the radiator (3), and - a regulating 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; 146) is closed on the return line (42) upstream of the connection of the bypass line (43) to the return line.
10. Fuel cell system (1; 100) according to any one of the preceding claims, in which 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 anode outlet (12), by Venturi effect.