FUEL CELL SYSTEM AND CORRESPONDING START-UP METHOD

Abstract

Fuel cell system (FCS1) comprising: a fuel cell (303), to which are fluidically connected a source of reducing fluid (304), a compressor (306) and at least one pressurized reservoir of oxidizing fluid (305), via respectively first, second and third valves (V1, V2, V3); and a controller (307) configured to, in a start-up phase, open the first and third valves, to supply the fuel cell with reducing fluid coming from the source of reducing fluid and with oxidizing fluid coming from the at least one pressurized reservoir, and in a use phase, keep the first valve open, to supply the fuel cell with reducing fluid, and close the third valve, open the second valve and activate the compressor, to supply the fuel cell with oxidizing fluid coming from the compressor. This allows a rapid start-up and a gain in mass and volume. Figure to be published with the abstract: Fig. 3

Description

Title of the invention: FUEL CELL SYSTEM AND CORRESPONDING START-UP METHOD Technical field

[0001] The invention relates to a fuel cell system (or FCS, for "Fuel Cell System" in English), as well as a method for starting such a system.

[0002] The invention applies in particular, but not exclusively, to a fuel cell system integrated into a propulsion system of a vehicle, such as an aircraft. STATE OF THE PRIOR ART

[0003] In a conventional implementation, a fuel cell system comprises a fuel cell stack supplied with reducing fluid from a reducing fluid source and with oxidizing fluid from a compressor. In general, the reducing fluid is dihydrogen and the oxidizing fluid is dioxygen or a gas, particularly air, comprising dioxygen.

[0004] Conventionally, the fuel cell system also comprises an electric starting system comprising a battery of accumulators. In the starting phase, this battery is used to electrically power the compressor, so that the latter begins to supply the oxidizing fluid to the fuel cell, and thus the priming (start of the reaction) of the fuel cell is initiated, which requires both the reducing fluid (hydrogen for example) and the oxidizing fluid (compressed air for example). In the use phase (also called the "operating phase"), that is to say once the fuel cell has started to operate, it is the electricity that it provides that takes over to electrically power the compressor.

[0005] This known starting solution is satisfactory, but there is a need to improve it further, both for starts in normal situations and for those in abnormal situations (emergency situations).

[0006] A first area of improvement concerns the start-up time, in particular, but not exclusively, in the field of aeronautics, when the fuel cell system is integrated into an aircraft propulsion system. In particular, in the event of a total engine flameout (or TEFO, for "Total Engine Flame Out" in English), it must be possible to restart it in the shortest possible time.

[0007] A second area of improvement, also important in the field of aeronautics, concerns the size and weight of the fuel cell system's starting system. Statement of the invention

[0008] A fuel cell system is provided comprising: a fuel cell; a source of reducing fluid fluidly connected, via a first valve, to a reducing fluid inlet of the fuel cell; a first compressor comprising an outlet fluidly connected, via a second valve, to an oxidizing fluid inlet of the fuel cell; and a controller comprising electronic circuitry configured to control the first compressor and the first and second valves. The fuel cell system further comprises at least one pressurized tank containing an oxidizing fluid and comprising an outlet fluidly connected, via a third valve, to the oxidizing fluid inlet of the fuel cell.The electronic circuitry of the controller is configured to: in a start-up phase, open the first and third valves, to supply the fuel cell with reducing fluid from the reducing fluid source and with oxidizing fluid from the at least one pressurized tank; and in a use phase following the start-up phase, keep the first valve open, to supply the fuel cell with reducing fluid from the reducing fluid source, and close the third valve, open the second valve and activate the first compressor, to supply the fuel cell with oxidizing fluid from the first compressor.

[0009] The proposed solution is therefore based on the use of at least one pressurized tank, to supply the fuel cell with oxidizing fluid during the start-up phase thereof. Thus, during the start-up phase, thanks to the pressurized tank it is no longer necessary to use the aforementioned conventional electric start-up system comprising a storage battery which electrically powers the compressor. In the proposed solution, the (first) compressor is used during the use phase (operation phase), being electrically powered by the fuel cell (the latter operates at the end of the start-up phase), therefore again without requiring a storage battery. The proposed solution therefore offers several advantages. It allows for faster start-up than the known solution since it does not require a complex sequence for starting the compressor with a storage battery (external source of electrical energy).It also allows a gain in mass and volume since the (at least one) pressurized tank and its associated elements (fixing and piping) have a mass and volume lower than those of the accumulator battery of the known solution and the associated elements (fixing, wiring, boxes, electrical precharge, DC / DC converters).

[0010] According to a particular embodiment, the reducing fluid is dihydrogen and the oxidizing fluid is dioxygen or a gas, in particular air, comprising dioxygen.

[0011] According to a particular embodiment, the at least one pressurized tank is mounted as a bypass of a pipe fluidically connecting the outlet of the first compressor to the oxidizing fluid inlet of the fuel cell.

[0012] According to a particular embodiment, the controller is connected to the first compressor and to the first, second and third valves via a direct current and low voltage network.

[0013] According to a particular embodiment, the at least one pressurized tank is rechargeable.

[0014] According to a particular embodiment, the fuel cell system comprises a second compressor comprising an outlet fluidically connected, via a fourth valve, to an oxidizing fluid inlet of the at least one pressurized tank, and in which the electronic circuitry of the controller is configured to, during the use phase: keep the third valve closed, open the fourth valve and activate the second compressor, to recharge the at least one pressurized tank with oxidizing fluid coming from the second compressor.

[0015] According to a particular embodiment, the second compressor is the same as the first compressor.

[0016] Also provided is an assembly of at least two fuel cell systems (each as discussed above, according to any one of the embodiments), wherein the at least one pressurized tank is common to the at least two fuel cell systems.

[0017] There is also provided an aircraft comprising at least one propulsion system integrating a fuel cell system as mentioned above, according to any one of the embodiments, or a set of at least two fuel cell systems as mentioned above.

[0018] There is also provided a method for starting a fuel cell system as mentioned above, according to any one of the embodiments, the method being implemented by the electronic circuitry of the controller and comprising: - in a start-up phase, open the first and third valves, to supply the fuel cell with reducing fluid from the reducing fluid source and with oxidizing fluid from the at least one pressurized tank; and - in a usage phase following the start-up phase, keep the first valve open to supply the fuel cell with reducing fluid from the reducing fluid source, and close the third valve, open the second valve and activate the first compressor to supply the fuel cell with oxidizing fluid from the first compressor.

[0019] A computer program product is also provided, comprising instructions causing the execution, by a processor, of the method mentioned above according to any one of its embodiments, when said instructions are executed by the processor.

[0020] A storage medium is also provided, storing such instructions. Brief description of the drawings

[0021] The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of at least one exemplary embodiment, said description being made in relation to the attached drawings, among which:

[0022] [Fig-1] schematically illustrates, in perspective, an aircraft equipped with systems of propulsion integrating fuel cell systems according to the invention;

[0023] [Fig.2] schematically illustrates one of the propulsion systems appearing on the [Fig.l], in one embodiment;

[0024] [Fig.3] schematically illustrates one of the fuel cell systems appearing in [Fig.2], in one embodiment;

[0025] [Fig.4] schematically illustrates an example of an algorithm executed by the controller appearing in [Fig.3], as part of a fuel cell system start-up process;

[0026] [Fig.5] schematically illustrates an example of hardware architecture of the controller appearing in [Fig.3], in one embodiment; and

[0027] [Fig.6] schematically illustrates a set of two fuel cell systems appearing in [Fig.2], in an alternative embodiment.

[0028] DETAILED DESCRIPTION OF EMBODIMENTS

[0029] The detailed description below focuses on describing embodiments of the present invention in the context of an aircraft. The principles of the present invention apply, however, in a broader context. These principles are in fact particularly applicable to other vehicles (such as trucks, buses, coaches, automobiles, boats, etc.). Even more generally, the present invention applies to any system (including a machine, an apparatus or a device) comprising at least one fuel cell system.

[0030] [Fig.l] schematically illustrates, in perspective, an aircraft 100 equipped with two propulsion systems 101 (one under each wing) integrating fuel cell systems according to the invention. In variants, the aircraft may comprise a different number of propulsion systems 101. Each propulsion system 101 is for example implemented in the form of a hydrogen nacelle (or “pod” in English), comprising a complete electric propulsion system.

[0031] [Fig. 2] schematically illustrates one of the propulsion systems 101 appearing in [Fig. 1], in one embodiment. The propulsion system 101 comprises a propeller 201 connected to two motor systems SMI and SM2 (alternating current motors) via a coupling system 203. Each of the motor systems SMI and SM2 is connected to the coupling system 203 by a secondary transmission shaft, one is referenced A1 and the other A2. The coupling system 203 is connected to the propeller 201 via a main transmission shaft 202. The propulsion system 101 also comprises a system control unit 204.

[0032] The engine system SMI comprises an electric motor M1 electrically powered by two fuel cell systems FCS1 and FCS2. Each of the fuel cells FCS1 and FCS2 is connected to the electric motor M1 via a DC / AC converter (direct current to alternating current converter), one is referenced C1 and the other C2. Similarly, the engine system SM2 comprises an electric motor M2 electrically powered by two fuel cell systems FCS3 and FCS4. Each of the fuel cells FCS3 and FCS4 is connected to the electric motor M2 via a DC / AC converter, one is referenced C3 and the other C4.

[0033] [Fig. 3] schematically illustrates one of the fuel cell systems (the one referenced FCS1) appearing in [Fig. 2], in one embodiment. The left part, referenced 301, represents the fluidic part and the right part, referenced 302, represents the electrical part. The fuel cell system FCS1 comprises: - a fuel cell 303 having a reducing fluid inlet EPI, an oxidizing fluid inlet EP2, an effluent outlet SP1 (to a pipe 315) and an electrical outlet SP2 (to a direct current electrical line 316); for example, the fuel cell is configured to produce electrical energy by oxidation-reduction of the reducing fluid and the oxidizing fluid through at least one electrolytic membrane (for example a proton exchange membrane, or PEM for “Proton Exchange Membrane” in English); for example, the reducing fluid is dihydrogen and the oxidizing fluid is dioxygen or a gas, in particular air, comprising dioxygen; - a source of reducing fluid 304 fluidly connected, via a first valve VI, to the reducing fluid inlet EPI of the fuel cell 303; - a compressor 306 comprising an air inlet EC and an outlet SC fluidically connected, via a second valve V2, to the oxidizing fluid inlet EP2 of the fuel cell 303; the compressor 306 is electrically powered and controlled by a motor control unit (or MCU, for “Motor Control Unit” in English) 310; - a pressurized tank 305 (for example in the form of a bottle) containing oxidizing fluid (for example dioxygen or a gas, in particular air, comprising dioxygen; for example under a pressure less than or equal to 1000 bars) and comprising an outlet ST fluidically connected, via a third valve V3, to the oxidizing fluid inlet EP2 of the fuel cell 303; in the implementation illustrated in [Fig. 3], the pressurized tank 305 is mounted on a pipe 313, in bypass of a pipe 312 fluidically connecting the outlet SC of the compressor 306 to the oxidizing fluid inlet EP2 of the fuel cell 303; and - a controller 307 comprising electronic circuitry (see description of [Fig.5]) configured to control the compressor 306 (via its MCU 310) and the first, second and third valves VI, V2 and V3, via a low voltage direct current network 307 (or LVDC, for “Low Voltage Direct Current” in English).

[0034] The electrical line 316, which is connected to the electrical output SP2 of the fuel cell 303, comprises a first branch 316b which makes it possible to power the electric motor Ml via the converter Cl (see [Fig.2]; Ml and Cl are not shown in [Fig.3] for the sake of simplification). The power line 316 also comprises a second branch 316a which makes it possible to power, via a DC / DC converter (direct current to direct current converter) 308, a bus 309 to which the auxiliary equipment (or BoP, for “Balance of Plant” in English) 311 of the FCS1 fuel cell system are connected, i.e. the equipment other than the fuel cell 303. The auxiliary equipment (BoP) 311 notably comprises the compressor 306 and its MCU 310, the air supply system (ASP) equipment, the thermal management system (TMS, for “Thermal Management System” in English), etc.

[0035] We now present, in connection with [Fig. 4], an example of the algorithm executed by the controller 307 appearing in [Fig. 3], within the framework of a method of starting the fuel cell system (for example, during a cold start, a normal start or a re-ignition of the SMI engine system included in the propulsion system 101 of the aircraft 100).

[0036] In a start-up phase 401, the controller 307 controls the opening of the first and third valves VI and V3 (the second valve V2 remains closed), to supply the fuel cell 303 with reducing fluid coming from the reducing fluid source 304 and with oxidizing fluid coming from the pressurized tank 305.

[0037] In a usage phase (operation) 402 which follows the start-up phase 401, the controller 307 keeps the first valve VI open, to continue to supply the fuel cell 303 with reducing fluid from the reducing fluid source 304, and controls the closing of the third valve V3, the opening of the second valve V2 and the activation of the compressor 306 (via its MCU 310), to supply the fuel cell 303 with oxidizing fluid from the compressor 306.

[0038] In the implementation illustrated in [Fig. 3], the pressurized tank 305 is rechargeable. It has an oxidizing fluid inlet ET which is fluidically connected, via a fourth valve V4 (and via the second valve V2), to the outlet SC of the compressor 306. The fourth valve is also controlled by the controller 307, via the network 307. To proceed with the filling of the pressurized tank 305 during the use phase (operation) of the fuel cell 303 (i.e. while the second valve V2 is open and the compressor 306 is activated), the controller 307 is configured to control the keeping of the third valve V3 closed and the opening of the fourth valve V4.

[0039] In a variant, the filling of the pressurized tank 305 is carried out using an additional compressor (separate from the compressor 306) one outlet of which is fluidically connected, via the fourth valve V4, to the oxidizing fluid inlet ET of the pressurized tank 305.

[0040] In another variant, the fuel cell system FCS1 comprises N pressurized tanks (rechargeable or not), with N an integer greater than 2, each containing oxidizing fluid and comprising an outlet fluidically connected, via a separate valve (therefore N valves for the N pressurized tanks), to the oxidizing fluid inlet EP2 of the fuel cell 303. In the start-up phase 401, the controller 307 controls the opening of the first valve VI and of the aforementioned N valves (the second valve V2 remains closed), to supply the fuel cell 303 with reducing fluid coming from the reducing fluid source 304 and with oxidizing fluid coming from the N pressurized tanks. If the N pressurized tanks are rechargeable, either they are recharged by the same compressor (the one referenced 306 or another), or they are each recharged by a separate compressor.

[0041] In another variant, the fuel cell system FCS1 comprises, as a backup solution in the event of failure of the starting system with the pressurized tank 305, a conventional electric starting system (comprising a battery of accumulators to electrically power the compressor at start-up).

[0042] [Fig. 5] schematically illustrates an example of hardware architecture of the controller 307 appearing in [Fig. 3], in one embodiment. The controller 307 comprises, connected by a communication bus 510: a processor or CPU (“Central Processing Unit” in English) 501; a RAM (“Random Access Memory” in English) 502; a ROM (“Read Only Memory” in English) 503, for example a Flash memory; a data storage device, such as a hard disk drive (HDD) or a storage media reader, such as an SD (“Secure Digital” in English) card reader 504; at least one communication interface 505 allowing the controller 307 to interact with other elements, in particular the MCU 310 of the compressor 306 and the valves VI, V2, V3 and V4.

[0043] The processor 501 is capable of executing instructions loaded into the RAM 502 from the ROM 503, from an external memory (not shown), from a storage medium, such as an SD card, or from a communication network (not shown). When the controller 307 is powered on, the processor 501 is capable of reading instructions from the RAM 502 and executing them. These instructions form a computer program causing the processor 351 to implement the behaviors, steps and algorithm described herein.

[0044] All or part of the behaviors, steps and algorithm described herein may thus be implemented in software form by executing a set of instructions by a programmable machine, such as a DSP (Digital Signal Processor) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component (chip) or a set of components (chipset), such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specified Integrated Circuit). Generally speaking, the controller 307 comprises electronic circuitry arranged and configured to implement the behaviors, steps and algorithms described herein.

[0045] [Fig. 6] schematically illustrates a set 600 of two fuel cell systems appearing in [Fig. 2] (those referenced FCS1 and FCS2), in an alternative embodiment. As already described above in connection with [Fig. 3], each fuel cell system FCS1 comprises, for the fluidic part, a fuel cell 303 (having a reducing fluid inlet EPI, an oxidizing fluid inlet EP2 and an effluent outlet SP1), a reducing fluid source 304, a compressor 306, a pressurized tank 305 and valves VI to V4. The pressurized tank 305 is common to both fuel cell systems FCS1 and FCS2.

Claims

Claims

1. Fuel cell system (FCS1 to FCS4) comprising: - a fuel cell (303); - a source of reducing fluid (304) fluidically connected, via a first valve (VI), to a reducing fluid inlet (EPI) of the fuel cell (303); - a first compressor (306) comprising an outlet (SC) fluidically connected, via a second valve (V2), to an oxidizing fluid inlet (EP2) of the fuel cell (303); and - a controller (307) comprising electronic circuitry configured to control the first compressor (306) and the first and second valves (VI, V2);characterized in that it further comprises at least one pressurized tank (305) containing an oxidizing fluid and comprising an outlet (ST) fluidically connected, via a third valve (V3), to the oxidizing fluid inlet (EP2) of the fuel cell (303), and in that the electronic circuitry of the controller (307) is configured to: - in a start-up phase, open the first and third valves (VI, V3), to supply the fuel cell (303) with reducing fluid coming from the reducing fluid source (304) and with oxidizing fluid coming from the at least one pressurized tank (305);and - in a use phase following the start-up phase, keep the first valve (VI) open, to supply the fuel cell (303) with reducing fluid from the reducing fluid source (304), and close the third valve (V3), open the second valve (V2) and activate the first compressor (306), to supply the fuel cell (303) with oxidizing fluid from the first compressor.;

2. A fuel cell system according to claim 1, wherein the reducing fluid is dihydrogen and the oxidizing fluid is dioxygen or a gas, especially air, comprising dioxygen.

3. Fuel cell system according to any one of claims 1 and 2, in which the at least one pressurized tank (305) is mounted as a bypass of a pipe (312) fluidically connecting the outlet (SC) of the first compressor (306) to the oxidizing fluid inlet (EP2) of the fuel cell (303).

4. A fuel cell system according to any one of claims 1 to 3, wherein the controller (307) is connected to the first compressor (306) and the first, second and third valves (VI, V2, V3) via a low voltage direct current network (314).

5. A fuel cell system according to any one of claims 1 to 4, wherein the at least one pressurized tank (305) is rechargeable.

6. Fuel cell system according to claim 5, comprising a second compressor comprising an outlet fluidically connected, via a fourth valve (V4), to an oxidizing fluid inlet (ET) of the at least one pressurized tank (305), and in which the electronic circuitry of the controller (307) is configured to, during the use phase: keep the third valve (V3) closed, open the fourth valve (V4) and activate the second compressor, to recharge the at least one pressurized tank with oxidizing fluid coming from the second compressor.

7. The fuel cell system of claim 6, wherein the second compressor is identical to the first compressor (306).

8. An assembly (600) of at least two fuel cell systems (FCS1, FCS2), each according to any one of claims 1 to 7, wherein the at least one pressurized tank (305) is common to the at least two fuel cell systems.

9. Aircraft (100) comprising at least one propulsion system (101) integrating a fuel cell system (FCS1 to FCS4) according to any one of claims 1 to 7 or a set (600) of at least two fuel cell systems according to claim 8.

10. A method of starting a fuel cell system (FCS1 to FCS4) according to any one of claims 1 to 7, the method being implemented by the electronic circuitry of the controller (307) and comprising:

11.

12. - in a start-up phase (401), opening the first and third valves (VI, V3), to supply the fuel cell with reducing fluid coming from the reducing fluid source and with oxidizing fluid coming from the at least one pressurized tank; and - in a use phase (402) which follows the start-up phase, keep the first valve (VI) open, to supply the fuel cell with reducing fluid coming from the reducing fluid source, and close the third valve (V3), open the second valve (V2) and activate the first compressor, to supply the fuel cell with oxidizing fluid coming from the first compressor. Computer program product, comprising instructions causing the execution, by a processor (501), of the method according to claim 10, when said instructions are executed by the processor. Storage medium (503), comprising instructions causing the execution, by a processor (501), of the method according to claim 10, when said instructions are executed by the processor.

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