METHOD FOR RECOVERING ELECTRICAL ENERGY FROM A REGENERATIVE BRAKING SYSTEM OF A FUEL CELL-POWERED MOTOR VEHICLE

Abstract

The invention relates to a method for recovering electrical energy from a regenerative braking system of a fuel cell motor vehicle to heat said fuel cell when said vehicle is started, comprising the following steps: a step of recovering a total amount of electrical energy (E1) from the regenerative braking system; a step of determining a maximum amount of electrical energy (E2) that can be supplied to said battery; a step of transmitting the total amount of electrical energy to said battery (E3) when said maximum amount of electrical energy is greater than the total amount of electrical energy or a step of transmitting the total amount of electrical energy to said fuel cell (E4) causing said fuel cell to heat when said maximum amount of electrical energy is less than the total amount of electrical energy.Abstract figure: Fig. 1.

Description

Title of the invention: METHOD FOR RECOVERING ELECTRICAL ENERGY FROM A REGENERATIVE BRAKING SYSTEM OF A FUEL CELL-POWERED MOTOR VEHICLE

[0001] The invention relates to fuel cell motor vehicles, and more particularly to the means for heating these fuel cells.

[0002] Known from the prior art is a patent application EP4197865 which describes a braking system for a fuel cell motor vehicle. The fuel cell generates electrical energy which is sent to the electric motor of said vehicle in order to enable its propulsion. The braking system comprises a reservoir arrangement comprising a first inlet configured to be in communication with an outlet of the fuel cell. A fluid is able to flow through said reservoir arrangement and through said outlet of the fuel cell and said first inlet. Thus, said fuel cell emits exhaust gases which exit through the outlet of the fuel cell and which enter the reservoir arrangement via the first inlet. The reservoir arrangement also comprises a first outlet whose role is to exit said exhaust gases. The braking system comprises an air blower.The air blower is put into operation when the said vehicle is braking. The role of the air blower is to transport ambient air in an air duct extending from the air blower to the second inlet of the tank arrangement. However, the patent application describes a conventional braking system that does not allow electrical energy to be regenerated to recharge the battery and / or to heat the fuel cell of the vehicle.

[0003] The objective of the present invention is to remedy these drawbacks by proposing to recover and use the electrical energy intended to be lost by the regenerative braking system to recharge the battery and / or to heat the fuel cell of a motor vehicle.

[0004] To achieve this objective, the invention proposes a method for recovering electrical energy from a regenerative braking system of a fuel cell motor vehicle to heat said fuel cell when said vehicle is started, said regenerative braking system making it possible to recover a total quantity of electrical energy, said vehicle comprising a battery having a temperature and a state of charge, said battery being capable of receiving a maximum quantity of electrical energy, said state of charge of the battery being greater or equal to a predetermined threshold value, the threshold value being the value for which the total quantity of electrical energy is less than the maximum quantity of electrical energy, said vehicle comprising a cooling circuit for said battery, said vehicle having a speed, a deceleration setpoint and a resistance to deceleration, said vehicle moving in an environment having an outside temperature, remarkable in that said method comprises the following steps: - a step of recovering the total quantity of electrical energy from the regenerative braking system, said total quantity of electrical energy being determined as a function of the speed of the vehicle, the deceleration setpoint of the vehicle and the resistance of the vehicle to deceleration; - a step of determining the maximum quantity of electrical energy that can be supplied to said battery as a function of the state of charge and the temperature of said battery; - a step of transmitting the total quantity of electrical energy to said battery when said maximum quantity of electrical energy is greater than the total quantity of electrical energy; - a step of transmitting the total quantity of electrical energy to said fuel cell causing the heating of said fuel cell, the electrical energy intended for heating said fuel cell varying according to the total quantity of electrical energy, the temperature of the cooling circuit and the external temperature of the environment when said maximum quantity of electrical energy is less than the total quantity of electrical energy.

[0005] Thanks to the invention, the electrical energy generated by the regenerative braking system is recovered in order to allow the heating of the fuel cell, which avoids using the electrical energy provided by the battery for this.

[0006] Preferably, said predetermined threshold value is greater than or equal to 80%.

[0007] Preferably, said predetermined threshold value is greater than or equal to 90%.

[0008] Thus, this makes it possible to prioritize the return of electrical energy to the battery when This is capable of storing it. If the fuel cell is already at an ideal temperature, this prevents the loss of electrical energy.

[0009] Advantageously, said step of transmitting the total quantity of electrical energy to said battery is carried out when the maximum quantity of electrical energy is at least twice the total quantity of electrical energy.

[0010] Advantageously, said step of transmitting the total quantity of electrical energy to said battery is carried out when the maximum quantity of electrical energy is at least three times greater than the total quantity of electrical energy.

[0011] Thus, electrical energy is transmitted to said fuel cell only in the case where the total amount of energy is significant.

[0012] The invention also relates to a system for recovering electrical energy from a regenerative braking system of a motor vehicle comprising a battery and a fuel cell, said recovery system comprising a means for recovering a total quantity of electrical energy from the regenerative braking system, a means for determining a maximum quantity of electrical energy that can be supplied to said battery, a means for transmitting the total quantity of electrical energy to the battery and a means for transmitting the total quantity of electrical energy to the fuel cell implementing the method for recovering electrical energy from a motor vehicle with a fuel cell to heat said fuel cell when starting said vehicle previously described.

[0013] Furthermore, the invention relates to a fuel cell motor vehicle comprising a system for recovering electrical energy from a previously mentioned regenerative braking system.

[0014] Finally, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement the steps of said method for recovering electrical energy from a fuel cell motor vehicle to heat said fuel cell when starting said vehicle previously described.

[0015] The invention will be further detailed by the description of a non-limiting embodiment, and on the basis of the appended figure illustrating the invention, in which [Fig.l] schematically illustrates, in the form of a flowchart, a method for recovering electrical energy from a regenerative braking system of a fuel cell motor vehicle to heat said fuel cell when starting said vehicle according to an embodiment of the invention.

[0016] [Fig.l] schematically illustrates a method for recovering electrical energy from a regenerative braking system of a fuel cell motor vehicle to heat said fuel cell when said vehicle is started in the form of a flowchart. The electrical energy of the regenerative braking system represents a total amount of electrical energy. In other words, the total amount of electrical energy is the amount of electrical energy collected from the regenerative braking system. The vehicle includes a battery allowing in particular the heating of the fuel cell when the vehicle is started. Indeed, to put the fuel cell into operation, it must reach a temperature of between 50°C and 90°C, or in the majority of cases depending on the type of fuel cell between 70°C and 80°C. Preferably, the temperature of the fuel cell is 75°C.The battery also has a charging status that . corresponds to the remaining available capacity of the battery to provide electrical energy at a given time. The battery is capable of receiving a maximum quantity of electrical energy, this being the quantity of electrical energy that can be redirected to said battery without there being any loss of electrical energy. For the implementation of said method, the state of charge of said battery must be greater than or equal to a predetermined threshold value, the predetermined threshold value being the value for which said battery is capable of storing the total quantity of electrical energy. In other words, the threshold value is the value for which the total quantity of electrical energy is less than the maximum quantity of electrical energy. Preferably, the predetermined threshold value is greater than or equal to 80%. More preferably, the predetermined threshold value is greater than or equal to 90%.The vehicle also includes a cooling circuit whose role is to reduce the temperature of the battery in order to avoid overheating. Indeed, overheating of the battery leads to a risk of fire of the battery, and consequently a risk of fire of the said vehicle as a whole. In addition, the said vehicle has a speed at which it travels and a deceleration setpoint when a driver stops accelerating. Finally, the vehicle has mechanical resistance to deceleration. The resistance to deceleration is particularly important on slopes, to avoid runaway rotation of the wheels causing an excessive gain in speed of the vehicle. The vehicle operates in an environment with an outside temperature which has an impact on the quantity of electrical energy to be supplied to the said fuel cell to heat it.The amount of electrical energy is the amount of electrical charges moved by electrons, also known as the amount of electricity. The amount of electrical energy is measured in Coulombs. The vehicle has an electric motor. When the vehicle is moving, the electrical energy is converted into kinetic energy, allowing the wheels to rotate and, consequently, the vehicle to move. When the vehicle slows down, the kinetic energy is returned to the motor, which converts it back into electrical energy, which is stored in the battery. The return of electrical energy when the vehicle slows down is called regenerative braking. Regenerative braking recovers a significant amount of energy that would otherwise be lost. This means that the electric vehicle can travel a greater distance with the same amount of energy, increasing its range.In a step of recovering the total amount of electrical energy El, the total electrical energy from the regenerative braking system is collected. The total amount of electrical energy varies depending on the speed at which the vehicle is traveling, the deceleration setpoint and the vehicle's resistance to deceleration. In a step of determining the maximum amount of electrical energy E2, the maximum amount of electrical energy that can be stored by said . battery is determined. The maximum amount of electrical energy is dependent on the state of charge of said battery. Indeed, when the battery has a state of charge of less than 10%, then said battery is capable of storing a large amount of electrical energy. Conversely, when the state of charge of said battery is 95%, then only a small amount of electrical energy can be supplied to said battery. In addition, the determination of said maximum amount of electrical energy is dependent on the temperature of said battery. The temperature of the battery is managed by the cooling circuit of said vehicle. During a step of transmitting the total amount of electrical energy to said battery E3, the total amount of electrical energy is transmitted in full to the battery provided that the maximum amount of electrical energy is less than the total amount of electrical energy.Indeed, if the battery is capable of storing the entirety of the total amount of energy regenerated by the regenerative braking system, then said total amount of electrical energy is entirely directed to said battery. As a result, there is no energy loss. During a step of transmitting the total amount of electrical energy to said fuel cell E4, said total amount of electrical energy is directed to the fuel cell in its entirety when the maximum amount of electrical energy is less than the total amount of electrical energy. Indeed, if the total electrical energy is transmitted to said battery while the latter is not capable of storing the entirety of the total amount of electrical energy, then there is necessarily a loss of electrical energy. The total electrical energy allows the heating of said fuel cell.The heating of said fuel cell is dependent on the total amount of electrical energy transmitted, the temperature of the cooling circuit of said vehicle and the outside temperature of the vehicle's environment. The invention also relates to a system for recovering electrical energy from said regenerative braking system implementing said method previously described, as well as a fuel cell motor vehicle comprising such a system. Finally, the invention relates to a computer program, the execution of which leads to implementing said method previously described.

Claims

Claims

1. Method for recovering electrical energy from a regenerative braking system of a fuel cell motor vehicle to heat said fuel cell when said vehicle is started, said regenerative braking system making it possible to recover a total quantity of electrical energy, said vehicle comprising a battery having a temperature and a state of charge, said battery being capable of receiving a maximum quantity of electrical energy, said state of charge of the battery being greater than or equal to a predetermined threshold value, the threshold value being the value for which the total quantity of electrical energy is less than the maximum quantity of electrical energy, said vehicle comprising a cooling circuit for said battery, said vehicle having a speed, a deceleration setpoint and a resistance to deceleration,said vehicle moving in an environment having an outside temperature, characterized in that said method comprises the following steps:, - a step of recovering the total quantity of electrical energy (El) from the regenerative braking system, said total quantity of electrical energy being determined as a function of the speed of the vehicle, the deceleration setpoint of the vehicle and the resistance of the vehicle to deceleration; - a step of determining the maximum quantity of electrical energy (E2) which can be supplied to said battery as a function of the state of charge and the temperature of said battery; - a step of transmitting the total quantity of electrical energy to said battery (E3) when said maximum quantity of electrical energy is greater than the total quantity of electrical energy; - a step of transmitting the total quantity of electrical energy to said fuel cell (E4) causing the heating of said fuel cell, the electrical energy intended for heating said fuel cell varying as a function of the total quantity of electrical energy, the temperature of the cooling circuit and the external temperature of the environment when said maximum quantity of electrical energy is less than the total quantity of electrical energy.

2. Method according to claim 1 characterized in that said predetermined threshold value is greater than or equal to 80%.

3. Method according to claim 2 characterized in that said predetermined threshold value is greater than or equal to 90%.

4. A method according to any one of claims 1 to 3 characterized in that said step of transmitting the total amount of electrical energy to said battery is carried out when the maximum amount of electrical energy is at least twice the total amount of electrical energy.

5. A method according to any one of claims 1 to 4 characterized in that said step of transmitting the total amount of electrical energy to said battery is carried out when the maximum amount of electrical energy is at least three times greater than the total amount of electrical energy.

6. A system for recovering electrical energy from a regenerative braking system of a motor vehicle comprising a battery and a fuel cell, said recovery system comprising means for recovering a total amount of electrical energy from the regenerative braking system, means for determining a maximum amount of electrical energy that can be supplied to said battery, means for transmitting the total amount of electrical energy to the battery and means for transmitting the total amount of electrical energy to the fuel cell implementing the method for recovering electrical energy from a motor vehicle with a fuel cell to heat said fuel cell when said vehicle is started according to any one of claims 1 to 5.

7. A fuel cell motor vehicle comprising a system for recovering electrical energy from a regenerative braking system according to claim 6.

8. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to implement the steps of said method for recovering electrical energy from a fuel cell motor vehicle to heat said fuel cell when said vehicle is started according to any one of claims 1 to 5.

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