WO2002032715A1

WO2002032715A1 - System and method for controlling a fuel cell mounted in an electrically-powered vehicle

Info

Publication number: WO2002032715A1
Application number: PCT/FR2001/003162
Authority: WO
Inventors: David Corgier; Gilles Dewaele; Fahri Keretli
Original assignee: Renault
Priority date: 2000-10-18
Filing date: 2001-10-12
Publication date: 2002-04-25
Also published as: FR2815302B1; FR2815302A1; EP1326762A1

Abstract

The invention concerns a system for controlling a fuel cell assembly (2) equipped with means generating hydrogen (26) from another fuel and means generating electric power (29) from said hydrogen and an oxidant. The fuel cell is designed to power a vehicle. The system comprises at least means (14) for detecting an intention of subsequent starting of the vehicle by the driver, and a control unit (13) adapted to actuate the hydrogen generating means upon detection of said intention of subsequent starting.

Description

System and method for controlling a fuel cell mounted in an electric traction vehicle

The present invention relates to fuel cells and their control.

Fuel cells are known comprising a proton exchange membrane (PEM) cell traversed for cooling by a heat transfer fluid which makes it possible to obtain electrical energy in the form of direct current with a high efficiency from energy. chemical without going through the intermediate stage of thermal or mechanical energy conversion. The fuel cell is supplied with hydrogen and oxygen-supplying air. These gases, sent into the core of the cell consisting of a stack of elementary cells where reverse reactions of the electrolysis of water take place, allow by electrochemical combination of hydrogen and oxygen, a circulation of protons producing a direct electric current as well as water. Generally, a fuel cell is an electrochemical generator supplied with hydrogen and oxygen, in particular with air. The installation of a fuel cell in a vehicle makes it possible to have a range comparable to that of a conventional vehicle with a "heat engine, while significantly reducing the emissions of carbon dioxide and pollutants.

The use of a fuel other than hydrogen to supply the cell requires the installation of a reformer which produces hydrogen from a primary fuel, generally a hydrocarbon such as methanol, or fuels usual vehicles with thermal engine. The operation of the reformer requires bringing it to a temperature of the order of 300 ° in the case of a methanol supply and of the order of 600 ° in the case of a gasoline supply, to ensure the generation of hydrogen.

During the phase of rise to the operating temperature of the reformer, the generation of electrical energy by the fuel cell is not very operational and therefore cannot adequately power the electric traction motor. One could consider prohibiting the starting of the vehicle during this phase, which would present a major drawback of use. One could also consider supplying the electric motor with an auxiliary source of energy such as electrochemical batteries, but which are generally of high mass and poor performance. The temperature rise time of the reformer is currently estimated at a few minutes.

The invention proposes to reduce the duration of the temperature rise phase of the reformer as perceived by the user of the vehicle.

The invention proposes to make the temperature rise phase of the reformer totally or partially transparent to the user of the vehicle. The control system according to the invention is intended for a fuel cell assembly equipped with means for generating hydrogen from another fuel and means for generating electrical energy from said hydrogen and an oxidizer. The fuel cell is intended to power a vehicle. The system comprises at least one means for detecting an intention to subsequently start the vehicle by the driver, and a control unit able to activate the means for generating hydrogen upon detection of said intention to start subsequently. By starting the commissioning of the hydrogen generation means before the driver actually starts the vehicle, for example by engaging and turning the key in the starter lock, the duration of temperature rise perceived by the driver is reduced .

In one embodiment of the invention, the means for detecting an intention to start later is a contactor of a vehicle door capable of detecting the opening of the door, for example of the door of the driver.

In one embodiment of the invention, the means for detecting an intention to start later is a contactor of a vehicle door lock capable of detecting the unlocking of the lock. In one embodiment of the invention, the means for detecting an intention to start later is a receiver for a remote control for opening the vehicle door.

In one embodiment of the invention, the means for detecting an intention for subsequent starting is a receiver for a remote control for subsequent starting of the vehicle. Said remote control can be dedicated to this function. Said remote control can be housed in the same housing as a door opening remote control.

In one embodiment of the invention, the means for detecting a subsequent start-up intention transmits to the control unit a commissioning signal at a predetermined time. It is thus possible to pre-program the time of said commissioning.

In one embodiment of the invention, the means for detecting a subsequent starting intention is a detector of the presence of the driver in the vehicle. A displacement or stress sensor can be provided in the seat of the driver's seat.

The system may include a temperature sensor of the hydrogen generation means connected to the control unit which is capable of authorizing the commissioning of the hydrogen generation means upon detection of said intention to start later if the temperature is less than a predetermined threshold value.

The system may include an indicator light indicating that the hydrogen generation means has been put into service upon detection of said intention for subsequent start-up.

According to another aspect of the invention, a vehicle comprises a fuel cell assembly equipped with means for generating hydrogen from another fuel and with means for generating electrical energy from said hydrogen and an oxidizer. The fuel cell is intended to power a vehicle. The vehicle is further provided with a control system comprising at least one means for detecting an intention to subsequently start the vehicle by the driver, and a control unit capable of putting into service the means for generating hydrogen upon detection of said intention to start later.

According to another aspect of the invention, a method for controlling a fuel cell capable of supplying a vehicle and equipped with means for generating hydrogen from another fuel and with means for generating d electrical energy from said hydrogen and from an oxidizer, comprises steps of detecting an intention to start the vehicle subsequently by the driver, and of activating the means for generating hydrogen upon detection of said intention to start ulterior.

In one embodiment of the invention, fuel is supplied to a burner of the hydrogen generation means in order to heat a main reactor of the hydrogen generation means. In one embodiment of the invention, fuel is supplied to a burner of the hydrogen generation means by bypassing the electric power generation means to send the hydrogen produced to said burner in order to heat a main reactor of the means. of hydrogen generation. In one embodiment of the invention, hydrogen is supplied to a burner of the hydrogen generation means from a hydrogen reserve in order to heat a main reactor of the hydrogen generation means.

In one embodiment of the invention, a main reactor of the hydrogen generation means is heated by means of an electrical resistance. The electrical resistance can be supplied by a vehicle battery and / or by the means for generating electrical energy.

The invention will be better understood from the study of a few embodiments taken by way of non-limiting examples and illustrated by the appended drawings, in which:

- Figure 1 is a schematic view of the system according to one aspect of the invention;

- Figure 2 is a flow diagram of process steps according to one aspect of the invention; - Figure 3 is a schematic view of a battery cell assembly fuel according to one aspect of the invention; and

- Figures 4 to 8 are schematic views of variants of Figure 3.

The system which will be described with reference to Figure 1, is intended to be mounted in a motor vehicle. The system referenced 1 as a whole is capable of controlling a fuel cell assembly 2, of the type comprising a fuel cell proper and a reformer by means of a link, for example a communication bus. A fuel conversion stage 3 is provided in the vehicle for supplying the fuel cell system 2 via a pipe 4. The fuel cell system 2 supplies electrical energy by means of a cable 5 connected to one or more batteries 6 and to the traction motor 7. The traction motor 7 drives a transmission 8, of the type comprising a differential, the output of which is connected to wheel half-shafts 9 and 10, themselves connected to the driving wheels 11 and 12.

The system 1 comprises a central unit 13 comprising at least one microprocessor, at least one memory, a communication bus between these elements, and at least one control software stored in the memory and capable of being executed by the microprocessor. The control unit 13 can be the vehicle supervisor. The control unit 13 is permanently supplied, not shown, at least by the batteries 6, to allow the early start-up of the fuel cell system 2 on receipt of information representative of the intention of the driver. start the vehicle. System 1 comprises at least one, but preferably several, of the following sensors:

- A sensor 14 for opening the driver's door connected to the central unit 13. The sensor 14 sends the door opening information as soon as the door is considered to be open, for example if it has been opened from an angle, or a distance greater than a threshold. The sensor

14 can also be used for other uses, such as controlling the interior lighting of the passenger compartment of the vehicle.

- A sensor 15 for unlocking and re-locking the driver's door lock, connected to the central unit 13. The sensor 15 sends information to the central unit 13 as soon as the lock is unlocked. The sensor 15 also sends corresponding information if the lock is relocked. The sensor 15 can be used for other uses, for example for a centralized closing / opening system of the doors of a vehicle. - A sensor 16 of a remote control signal, for example infrared, emitted by a remote control 17 for locking / unlocking the driver's door. The sensor 16 is of course also used to control the locking and unlocking of said door.

- A sensor 18 of a remote control signal for early start-up of the fuel cell assembly 2 by means of a dedicated remote control 19 which the driver actuates remotely and can keep on him in a pocket of clothing, for example .

- A sensor 20 for the presence of the driver in the vehicle. The sensor 20 can be of the infrared type. The sensor 20 can also be integrated into the seat of the driver's seat and detect its presence by detecting pressure, stress, displacement, etc.

The system 1 further comprises an early start indicator 21, positioned in the passenger compartment of the vehicle and being, for example, in the form of an indicator light which lights up on command from the central unit 13 when early commissioning is controlled by the central unit 13.

Provision will also be made to connect the central unit 13 to the lock 22 for controlling the start of the vehicle, in which the driver will engage his key to start the vehicle. It is also possible to provide a preprogramming unit 23 and a preprogramming interface 24 connected to the control unit 13. The operation of the system is illustrated in FIG. 2. The central unit 13 periodically scans the signals received from the sensors 14, 15 , 16, 18 and 20, the anti-theft lock 22 and the preprogramming unit 23. If the vehicle is unlocked, by key or by remote control signal, then the central unit 13 sets the logic variable DEVERR to 1 If the vehicle is re-locked, then the central unit 13 sets DEVERR to 0.

If the driver's door is open, then the central processing unit 13 sets the OPEN logic variable to 1. If the driver's door is closed, then the central unit 13 sets OPEN to 0.

If the presence of the driver in the vehicle is detected by the presence sensor 20, the central unit 13 sets the PRESCOND variable to 1. Otherwise, the central unit 13 sets PRESCOND to 0.

If a request for early commissioning is sent by a remote transmitter, for example a radio transmitter, and picked up by the sensor 18, then the central unit 13 sets the logic variable DEMDIST to 1.

If a request to interrupt the early start-up is sent by this transmitter, then the central unit 13 sets DEMDIST to 0.

If a request for early commissioning is generated by preprogramming, then the central unit 13 sets the logic variable DEMPROG to l.

The preprogramming unit 23 generates a new request for early start-up only if since the last request for early start-up, there has been at least one vehicle start-up. This avoids unnecessarily launching early start-ups in a vehicle which has been parked for a long period without deprograrning the normal service of the fuel cell assembly 2. The central unit 13 sets a logic variable DEMCOND to 1 if DEVERR goes from 0 to 1, or OPEN goes from 0 to 1, or DEMDIST goes from 0 to 1, or DEMPROG goes from 0 to 1.

If the vehicle is requested to start by positioning the ignition key in a predefined position or by any other appropriate means, then the central unit 13 sets the logic variable DEMVEH to 1. This variable is reset to 0 when the cut-off of the engine is requested.

Early commissioning takes place only if the driver has not yet requested the vehicle to start. If start-up is requested by the driver, then we stop the early start-up and switch to a management mode which simultaneously manages the heating of the reformer and the traction.

Early start-up is only carried out if the reformer temperature is lower than its operating temperature Tl. As soon as this temperature is reached, the early commissioning ends. After carrying out the early start-up, a new early start-up can only be launched when a new request for early start-up is made, in other words when the DEMCOND variable takes again the value 1. If early commissioning is started after unlocking,

DEVERR = 1, or when the driver's door is opened, OUVPORTE = 1, then the central unit 13 starts a COMPTEMPS time counter. If COMPTEMPS reaches a predefined TIMEOUT value and if the PRESCOND variable is 0, then early commissioning is interrupted. This makes it possible to avoid continuing the early start-up in the event that the driver simply wishes to access the vehicle without starting it.

At the start of the process illustrated by the flow diagram of steps in FIG. 2, an ARRCOND variable representative of the stopping of the early commissioning is set to 0. The DEMCOND variable is also set to 0. The central unit 13 performs a test on the ARRCOND variable, then, if the ARRCOND variable is 1, another test on the DEMCOND variable. If this equals 0, we return to the start of the process. In contrary cases, that is to say if ARRCOND is worth 0 or if ARRCOND is worth 1, DEMCOND is worth 1, we pass to the test on the temperature of the reformer and on the variable

DEMVEH. If the temperature of the reformer is lower than Tl and if the variable DEMVEH is worth 0, one carries out a test on the unlocking and the opening of door. In the contrary cases, we go directly to a stage of stopping the early commissioning. At the end of the early commissioning stop, the variable

ARRCOND is set to 1 and the variables COMPTEMPS, DEMDIST, DEMPROG, DEVERR and OUVPORTE are set to 0 and we start again at the beginning of the process.

If the variable DEVERR is worth 1 or if the variable OUVPORTE is worth 1, we go to a step of incrementing the counter COMPTEMPS.

When COMPTEMPS becomes greater than the TIMEOUT constant, a test is performed on the PRESCOND variable. If PRESCOND is equal to 1, we go to the early commissioning stage. If COMPTEMPS is less than TIMEOUT, we pass to the stage of stopping the early commissioning. At the end of the early commissioning, the variables DEMCOND and ARRCOND are set to 0 and we start again at the start of the process. If PRESCOND is worth 0, we go to the stage of stopping the early commissioning.

During the test on the variables DEVERR and OUVPORTE, if DEVERR is worth 0 and OUVPORTE is worth 0, we pass to a test on the variables

DEMDIST and DEMPROG. If DEMDIST is worth 1 or if DEMPROG is worth 1, we go to the early commissioning stage. Otherwise, a test is performed on the ARRCOND variable. If ARRCOND is worth 1, we start again at the start of the process. If ARRCOND is equal to 0, we pass to the stage of stopping the early commissioning.

In FIG. 3, a type of fuel cell assembly 2 is illustrated. The assembly 2 is supplied with fuel coming from the conversion stage 3 by the line 4, as well as with air by a line 25. L assembly 2 comprises a reformer 26 supplied with fuel, air and water, a conversion stage 27 disposed at the outlet of the reformer 26 and can also be supplied with water, a filter 28 disposed at the outlet of the conversion stage 27 and also supplied with air, intended to purify the hydrogen at the outlet of the conversion stage 27 in order to remove possible residues of carbon monoxide therefrom, and a fuel cell 29 disposed at the outlet of the filter 28 and supplied with hydrogen by said filter 28 and in air. The electrical output of the fuel cell 29 is not shown.

The fuel cell 29 includes a hydrogen outlet 30 and an air outlet 31. The air outlet 31 is connected to a water trap 32 provided with an outlet connected to a water tank 33 which allows supplying water to the reformer 26 and the conversion stage 27. The assembly 2 further comprises a burner 34 supplied by the hydrogen outlet 30 from the fuel cell 29 and by another outlet from the water trap 32, the burner 34 being provided with an exhaust 35. The fuel cell assembly allows a double transformation of a fuel of the hydrocarbon and hydrogenated type into hydrogen and of the hydrogen added with oxidant, into electrical energy.

Several reforming possibilities exist: 1 ° / Cracking consists in breaking the molecules of the fuel, previously vaporized if necessary, entering thanks to the effect of the temperature obtained by a burner or a plasma.

2 ° / Partial oxidation consists in oxidizing the fuel through the addition of air, and this at a high temperature depending on the fuel used. This reaction is exothermic.

3 ° / Steam reforming consists of adding water vapor to the fuel previously vaporized if necessary, to initiate a catalytic reaction, this at a high temperature, depending on the fuel used.

This reaction is endothermic. 4 ° / Auto thermal reforming consists of combining the two preceding reactions within the same reactor so that the endothermic and exothermic reactions compensate each other.

All these reactions require a certain level of temperature for their initiation and to obtain a level of hydrogen purity satisfactory for the fuel cell. In addition, the reformer consists of a certain mass of material having a high thermal inertia. Consequently, the rapid rise in temperature of the reformer 26 is relatively difficult.

In the embodiment illustrated in FIG. 4, a starter burner 36 is added to the reformer 26 and is supplied with fuel in order to heat the reformer and reach the appropriate operating temperature. This embodiment requires dimensioning in power a specific fuel burner to obtain a suitable preheating time. As a variant, as illustrated in FIG. 5, the reformer 26 can be supplied with high flow rate of fuel while providing a bypass 37 allowing the battery 29 to be bypassed. The hydrogen flow leaving the filter 28 is sent directly to the burner 34 which is added to the reformer 26 and burning hydrogen in overstoichiometry in the burner 34. The addition of a specific starting burner is avoided.

In the embodiment illustrated in FIG. 6, a heating resistor 38 for heating the reformer 26 is supplied by the battery 6.

The resistor 38 is dimensioned as a function of the voltage of the battery 6, of the thermal inertia of the reformer 26 and of the desired duration of the preheating.

The variant of FIG. 7 is close to that of FIG. 6, except that the resistor 38 is supplied by the fuel cell 29. The value and the power of the resistor 38 are then dimensioned as a function of the voltage of the battery 29 at low temperature and low air pressure, while respecting the desired preheating time.

In the embodiment illustrated in FIG. 8, the assembly 2 comprises a hydrogen accumulator 39 disposed at the outlet of the filter 28, parallel to the fuel cell 29 and capable of supplying, during preheating, the burner 34 provided to heat the reformer 26.

It thus succeeds in reducing or eliminating the time required between actuation of the starting by means of the vehicle anti-theft lock and the actual movement of the vehicle, delay due to the heating up of the fuel cell assembly. . The invention also allows a reduction in energy consumption in comparison with a solution consisting in permanently maintaining the fuel cell assembly at operating temperature.

The invention therefore makes it possible to anticipate by several seconds, or even several minutes, the preheating of the reformer and to offer the driver, when he actuates the anti-theft lock, the possibility of moving the vehicle, either immediately or at at the very least, significantly faster than in a conventional system.

It is also possible to provide for an early start-up request generated by an electronic unit internal to the vehicle, at a preprogrammed instant, thanks to an internal clock. A driver who leaves every day at the same time or in a given time slot, of the order of a few tens of minutes, can thus program the preheating of the reformer of the fuel cell assembly for the start of said time slot.

Claims

1 -System for controlling a fuel cell assembly (2) equipped with a means for generating hydrogen (26) from another fuel and a means for generating electrical energy (29) at starting from said hydrogen and from an oxidizer, said fuel cell being intended to supply a vehicle, characterized in that it comprises at least one means for detecting an intention of subsequent starting of the vehicle by the driver, and a control unit (13) able to put into service the means for generating hydrogen upon detection of said intention to start up subsequently. 2-System according to claim 1, characterized in that the means for detecting a subsequent start intention is a contactor (14) of a vehicle door capable of detecting the opening of the door.

3-System according to claim 1 or 2, characterized in that the means for detecting a subsequent starting intention is a contactor (15) of a vehicle door lock capable of detecting the unlocking of the lock.

4-System according to any one of the preceding claims, characterized in that the means for detecting an intention to start later is a receiver (16) of a remote control for opening. vehicle door.

5-System according to any one of the preceding claims, characterized in that the means for detecting a subsequent start intention is a receiver (18) of a remote control for subsequent start of the vehicle.

6-System according to any one of the preceding claims, characterized in that the means for detecting an intention to start later transmits to the control unit a commissioning signal at a predetermined time. 7-System according to any one of the preceding claims, characterized in that the means for detecting a subsequent start intention is a detector (20) of presence of the driver in the vehicle. 8-Vehicle comprising a system according to any one of the preceding claims.

9 — Method for controlling a fuel cell capable of supplying a vehicle and equipped with a means of generating hydrogen from another fuel and a means of generating electrical energy from said hydrogen and an oxidizer, in which an intention to subsequently start the vehicle by the driver is detected, and the means for generating hydrogen is put into service on detection of said intention to start subsequently. 10-The method of claim 9, wherein the fuel is supplied to a burner of the hydrogen generation means in order to heat a main reactor of the hydrogen generation means.

11-A method according to claim 9 or 10, wherein hydrogen is supplied to a burner of the hydrogen generation means by bypassing the electric power generation means to send the hydrogen produced to said burner in order to heat a main reactor means of hydrogen generation.

12-A method according to any one of claims 9 to 11, wherein hydrogen is supplied to a burner of the hydrogen generation means from a hydrogen reserve in order to heat a main reactor of the generation means. hydrogen.

13-A method according to any one of claims 9 to 12, wherein heating a main reactor of the hydrogen generation means by means of an electrical resistance supplied by a vehicle battery.

14-A method according to any one of claims 9 to 13, wherein heating a main reactor of the hydrogen generation means by means of an electrical resistance supplied by the co-bustile cell.