METHOD FOR INTELLIGENT HEATING OF A FUEL CELL SYSTEM AND VEHICLE

Abstract

The invention relates to a method for the intelligent heating of a fuel cell system (1), wherein a heat required for heating a fuel cell system (1) integrated in a vehicle (2) to an operating temperature is provided by a secondary brake system (3) of the vehicle (2) in the form of at least one retarder (3.1) and/or a brake chopper (3.2), The invention is characterized in that a planned journey is carried out with the vehicle (2), wherein the vehicle (2) switches from battery-electric operation to a fuel cell operating mode at a switchover time during the journey, in which a drive energy required to drive the vehicle (2) is provided by the fuel cell system (1), wherein an analysis of the planned journey is carried out before the start of the journey in order to determine an amount of heat which can be drawn from the secondary braking system (3) during a period of the journey, and wherein the switchover time is determined as a function of the amount of heat which can be drawn and/or heating of the fuel cell system (1) is started before the start of the journey in order to ensure that the fuel cell system (1) has reached the operating temperature when the switchover time is reached.

Claims

1. Method for the intelligent heating of a fuel cell system (1), wherein a heat required for heating a fuel cell system (1) integrated in a vehicle (2) to an operating temperature is provided by a secondary brake system (3) of the vehicle (2) in the form of at least one retarder (3.1) and/or a brake chopper (3.2), characterized in that a planned journey is carried out with the vehicle (2), wherein the vehicle (2) switches from battery-electric operation to a fuel cell operating mode at a switchover time during the journey, in which a drive energy required to drive the vehicle (2) is provided by the fuel cell system (1), wherein an analysis of the planned journey is carried out before the start of the journey in order to determine an amount of heat which can be drawn from the secondary braking system (3) during a period of the journey, and wherein the switchover time is determined as a function of the amount of heat which can be drawn and/or heating of the fuel cell system (1) is started before the start of the journey in order to ensure that the fuel cell system (1) has reached the operating temperature when the switchover time is reached.

2. Method according to claim 1, characterized in that the journey is analyzed on a vehicle-internal (4.1) or a computing unit outside the vehicle (4.2).

3. Method according to claim 1 or 2, characterized in that at least part of the energy recuperated by the brake chopper (3.2) during a braking operation of the vehicle (2) is used to charge a traction battery (5) of the vehicle (2).

4. Method according to one of claim 1 or 3, characterized in that the fuel cell system (2) is heated when the vehicle (2) is stationary, taking into account the current or future charge level of the traction battery (5).

5. Method according to one of claims 1 to 4, characterized in that in addition to an evaluation of a planned route and a corresponding route profile, the analysis of the journey also takes into account any idle times of the vehicle (2).

6. Method according to one of claims 1 to 5, characterized in that energy required for energy conversion with the secondary braking system (3) is obtained from an energy source inside and/or outside the vehicle.

7. Vehicle (2) with a fuel cell system (1), a secondary braking system (3) and a computing unit (4.1), characterized in that the fuel cell system (1), the secondary braking system (3) and the computing unit (4.1) are set up to carry out a method according to one of claims 1 to 6.

8. Vehicle (2) according to claim 7, characterized by a design as a commercial vehicle.

9. Vehicle (2) according to claim 8, characterized by a design as a truck, van or omnibus.

10. Vehicle (2) according to one of claims 7 to 9, characterized by an at least partially automated control system.

Description

[0033] In the drawings:

[0034] FIG. 1 shows a simplified schematic representation of a vehicle according to the invention; and

[0035] FIG. 2 a flow chart of a method according to the invention.

[0036] FIG. 1 shows a highly simplified representation of a vehicle 2 according to the invention, in this case in the form of a truck. The vehicle 2 has an electric drive train 11 with two electric motors 6. The electric motors 6 can be operated in a generator mode to brake the vehicle 2. The electric motors 6 are connected to a high-voltage network 7 and can receive energy via this from a traction battery 5 and/or a fuel cell system 1, in particular in the form of a PEM fuel cell, in order to supply them with electrical drive energy. Furthermore, the vehicle 2 has a charging interface 8 via which the vehicle 2 can obtain energy from a charging station 9.

[0037] The fuel cell system 1 must be heated to the correct operating temperature for correct and energy-efficient operation. The amount of heat required for this is provided by a secondary braking system 3 of the vehicle 2. The secondary braking system 3 comprises at least one retarder 3.1 and/or at least one brake chopper 3.2. The retarder 3.1 and the brake chopper 3.2 are integrated into a common cooling circuit 10, to which the fuel cell system 1 is also connected. Similarly, other vehicle components such as the traction battery 5 and/or the electric motors 6 can be connected to the cooling circuit 10 (not shown). Furthermore, other additional components such as pipes, pumps, valves, heat exchangers and the like are not shown.

[0038] In order to heat up the fuel cell system 1, electricity is dissipated at resistors of the brake chopper 3.2 into heat, which is transferred to a coolant flowing through the cooling circuit 10. Additionally, or alternatively, the cooling circuit 10 and thus the fuel cell system 1 can also be heated via the retarder 3.1. For this purpose, the retarder 3.1 taps shaft power from the drive train 11 of the vehicle 2, causing an impeller or blade wheel surrounded by fluid to rotate. The fluid heats up due to friction between the impeller or blade wheel and the fluid surrounding the wheel. The waste heat generated in this process is also transferred to the cooling circuit 10. The retarder 3.1 can be operated while the vehicle 2 is moving or when stationary. When stationary, the wheels 12 of the vehicle 2 are decoupled from an operative connection to the electric motors 6 and the torque generated by the electric motors 6 is fed into the retarder 3.1. Corresponding shifting processes take place within a transmission, for example in the form of a so-called E-axis 15.

[0039] To control the warm-up process of the fuel cell system 1, the vehicle 2 also comprises a central, internal computing unit 4.1, which is connected to vehicle subsystems via individual control units 13. Furthermore, the vehicle 2 has a communication interface 14 via which the vehicle 2 exchanges data with a computing unit 4.2 outside the vehicle, in this case in the form of a back end or a cloud.

[0040] A process sequence of a method according to the invention is illustrated in FIG. 2. In a method step 201, an itinerary of a planned journey with the vehicle 2 is entered into the internal or external computing unit 4.1, 4.2. In addition to a route, the itinerary also includes scheduled departure, arrival and/or break times, as well as any other idle times of the vehicle 2.

[0041] The itinerary is evaluated in method step 202. By analyzing the planned driving route, sections of the route can be identified where vehicle 2 is likely to brake. By taking other driving parameters into account, such as the expected vehicle speed and braking distance, it is possible to estimate the amount of heat that can be generated by the secondary braking system 3 and used to heat the fuel cell system 1 to operating temperature.

[0042] In method step 203, which can generally also be carried out simultaneously or before method step 202, further vehicle parameters such as a charge level of the traction battery 5, a charging cable of a charging station 9 plugged into the charging interface 8, a tank capacity of a hydrogen tank not shown, a current temperature of the cooling circuit 10 and/or the fuel cell system 1 or the like are analyzed.

[0043] A switchover time for changing from a purely battery-electric operating mode of the vehicle 2 to a fuel cell operating mode during the journey to be made is determined in the method step 204. This switchover time is selected so that vehicle 2 can begin its journey in accordance with the itinerary in such a way that a predetermined schedule can be met as time-efficiently as possible while minimizing potential delays. This also includes the fastest possible departure of vehicle 2 from its starting point. In addition, the switchover time is selected in such a way that energy consumption for driving the vehicle is minimized as far as possible. For this purpose, an amount of energy required to heat up the fuel cell system 1 must be taken into account in addition to the pure drive energy.

[0044] Furthermore, the switchover time can be determined in such a way that the costs incurred for making the journey are minimized. If, for example, electricity can be obtained at a particularly favorable rate via the charging station 9, the traction battery 5 is charged as fully as possible and the fuel cell system 1 is warmed up before departure by means of the secondary braking system 3 while the vehicle 2 is stationary, in accordance with the schedule to be met. If, on the other hand, the electricity available from the charging station 9 is relatively expensive, the fuel cell system 1 is preferably heated up during the journey. Heating up the fuel cell system 1 while driving also has the advantage that the vehicle 2 can depart in good time.

[0045] In method step 205, a check is made as to whether sufficient heat can be provided by the secondary braking system 3 during the journey in order to heat the fuel cell system 1 to the operating temperature when the switchover time is reached. If this is not the case, preheating of the fuel cell system 1 is begun in method step 206. The journey with vehicle 2 begins in method step 210. If the journey is begun before the fuel cell system 1 has warmed up, heating of the fuel cell system 1 is begun in method step 211.

[0046] In method step 212, the fuel cell system 1 reaches its operating temperature, whereupon a switchover is made to the fuel cell operating mode in method step 213 in accordance with the switchover time.

[0047] By analyzing the planned journey or the itinerary and the vehicle parameters such as the current charge status of the traction battery 5, it is possible for the vehicle 2 to depart very early, as the fuel cell system 1 can also be heated up to operating temperature during the journey. The idle time of the vehicle 2 can also be further reduced by charging the traction battery 5 only to the extent that the traction battery 5 is empty or has reached a critical state of charge when the switchover time is reached. In addition, the switchover time is determined in such a way that the amount of heat required to warm up the fuel cell system 1 is obtained in a particularly sustainable and therefore environmentally friendly way. This means that costs can be reduced. The secondary braking system 3, which is already in place, is used to generate heat, eliminating the need for a costly separate heating system.