Pre-heating system for a vehicle and pre-heating method

Abstract

Pre-heating system (1) for a vehicle (2) comprising a first cooling circuit (3) comprising a first coolant (4) circulating therein and connected to a fuel cell system (5) of the vehicle (2) for regulating the operating temperature of said fuel cell system (5), a second cooling circuit (6) comprising a second coolant (7) circulating therein, the second cooling circuit (6) being separated from the first cooling circuit (3), and a heat exchanger (8) for thermally coupling the first cooling circuit (3) to the second cooling circuit (6) and for determining a heat exchange between the first coolant (4) and the second coolant (7), wherein the second cooling circuit (6) comprises at least a high power resistor (9).

Description

[0001] PRE-HEATING SYSTEM FOR A VEHICLE AND PRE-HEATING METHOD

[0002] Technical Field

[0003] The present invention relates to a pre-heating system for a vehicle, in particular to a system for assisting the cold start of the fuel cell. Also, the present invention relates to a vehicle comprising said pre-heating system and to a method for pre-heating a fuel cell system.

[0004] Background Art

[0005] The start of a vehicle having a fuel cell system can be strongly affected by the external temperatures. As a matter of fact, at very cold ambient temperatures, for example between -40°C and +10°, a fuel cell system cannot be started due to the danger of frozen components and needs to be first pre-heated with an external heat source. If the system is started without pre-heating, a very quick degradation (wear) of the fuel cell system is to be expected. Of course, it is possible to renounce using any dedicated heating source. However, in this case the vehicle needs to be parked inside a parking hall maintaining the internal temperature always above 10°C.

[0006] Usually, to assist the cold start of a fuel cell, fuel cell systems are provided with dedicated electric heating devices, for example a coolant power heater (CPH) or a positive temperature coefficient (PTC) heater, installed in the fuel cell cooling circuit. By activating the electric heating device, a certain amount of heat is generated and can be transferred to the fuel cell system by warming up the fuel cell coolant. However, to transfer the generated heat into the circulating fuel cell coolant, the electric heating device comprises a large metallic surface. This surface can introduce ions into the fuel cell coolant. Furthermore the lifetime of the fuel cell coolant can be reduced, due to local overheating > 100°C.

[0007] With a large amount of ions in the fuel cell coolant, there is the risk of a reduction of the insulating resistance in the environment of the fuel cell system. Also, there is the risk of an internal short circuit in the fuel cell system. Furthermore, the presence of ions in the fuel cell coolant would reduce the service life of the ion exchanger. In other words, at a certain point the ions concentration can be so high that the fuel cell system cannot be restarted anymore.

[0008] US 2023 / 364962 A1 describes an integrated thermal management system for a fuel cell electric vehicle CN 109962268 B describes a fuel cell vehicle thermal management method system, the system including a fuel cell subsystem, a power battery subsystem, a passenger compartment heating subsystem, and a heat exchange control subsystem.

[0009] DE 10 2010 052703 A1 describes a device for adjusting temperature of fuel cell of a vehicle, having heating system operated by electric power source that is arranged external to motor vehicle, and secondary heating circuit coupled with primary heating circuit and fuel cell

[0010] US 2023 / 001761 A1 describes an apparatus for controlling energy of a fuel cell vehicle, to expand a usable range of an energy consuming device, to increase efficiency of heating and cooling, and to simplify a layout of the device.

[0011] Although known methods can usefully assist the driver by starting the vehicle in cold conditions, these approaches can degrade the fuel cell system since they usually employ a heating device inside the fuel cell cooling circuit of the fuel cell system that would increase the ions concentration inside the coolant.

[0012] Summary of the Invention

[0013] Examples of the present disclosure seek to address or at least alleviate the above problems.

[0014] In a first aspect, there is provided a pre-heating system for a vehicle comprising: a first cooling circuit comprising a first coolant circulating therein and connected to a fuel cell system of the vehicle for regulating the operating temperature of said fuel cell system; a second cooling circuit comprising a second coolant circulating therein, the second cooling circuit being separated from the first cooling circuit; and a heat exchanger for thermally coupling the first cooling circuit to the second cooling circuit and for determining a heat exchange between the first coolant and the second coolant, wherein the second cooling circuit comprises at least a high power resistor.

[0015] In a second aspect there is provided a vehicle comprising the pre-heating system of the first aspect.

[0016] In a third aspect of the invention there is provided a method for pre-heating a fuel cell system of a vehicle, the method comprising: providing a first cooling circuit comprising a first coolant circulating therein and connected to a fuel cell system of the vehicle for regulating the operating temperature of said fuel cell system; providing a second cooling circuit comprising a second coolant circulating therein, the second cooling circuit being separated from the first cooling circuit, wherein the second cooling circuit comprises at least a high power resistor and wherein the second cooling circuit is thermally coupled to the first cooling circuit by means of a heat exchanger; and heating the second coolant by supplying electrical energy to the high power resistor and transferring heat from the second coolant to the first coolant at the heat exchanger.

[0017] Other aspects and features are defined in the appended claims.

[0018] Examples of the disclosure may provide a system, a vehicle, and a method for pre-heating the fuel cell system that maintains the service life of the fuel cell system by avoiding the introduction on ions into the cooling circuit of the fuel cell system.

[0019] Also, examples of the disclosure may provide a system, a vehicle, and a method that are efficient in assisting the driver by cold starting of the vehicle by using devices already present in the vehicle and used also for different purposes.

[0020] The present pre-heating system comprises a cooling circuit (having a heating device) distinct from the cooling circuit of the fuel cell system that is used to transfer heat from one coolant to another coolant. Since the two cooling circuits are separated, the heat transfer only occurs through a heat exchanger without mixing the coolants of the two circuits. Therefore, any possible ion generation and local overheating in the coolant of the cooling circuit comprising the heating device would not influence to the coolant of the cooling circuit of the fuel cell system, thereby avoiding or strongly reducing any degradation of the fuel cell system.

[0021] In addition, the pre-heating system comprises a heating element that is part of a system already present in the vehicle so that no additional components or devices are needed for preheating the fuel cell system.

[0022] Brief Description of the Drawings

[0023] Examples of the disclosure will now be described by way of example only with reference to the accompanying drawings, in which like references refer to like parts, and in which:

[0024] Figure 1 is a schematic representation of a pre-heating system and vehicle according to an example; Figure 2 is a schematic representation of the two cooling circuits of the pre-heating system according to an example; and

[0025] Figure 3 is a flow diagram of the method according to an example.

[0026] Unless otherwise indicated, elements common to or similar to several figures bear the same reference signs and have identical or similar features, so that these common elements are generally not described again for the sake of simplicity.

[0027] Detailed Description of Embodiments

[0028] The solutions provided in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Figure 1 describes a generic representation of the pre-heating system 1 according to the present disclosure. The system 1 comprises two cooling circuits, a first cooling circuit 3 connected to a fuel cell system 5 of a vehicle 2 and a second cooling circuit 6. A first coolant 4 circulates into the first cooling circuit 3 and is used to regulate the temperature of the fuel cell system 5. It is noted that the first cooling circuit 3 is typically used when working with a fuel cell system 5. As a matter of fact, a proper temperature control and heat management is necessary to ensure that the fuel cell system 5 runs consistently. Any deviation from an optimal operating temperature range can result in lowered efficiencies.

[0030] A second coolant 7 circulates into the second cooling circuit 6. The second cooling circuit 6 is provided with a heating element, such as a high power resistor (HPR) 9 to heat the second coolant 7 when needed, for example at cold starting of the vehicle.

[0031] It is noted that the second cooling circuit 6 is physically separated from the first cooling circuit 3. The physical separation between the two circuits means that there is no connection between the conduits of the circuits and that therefore the coolant of one circuit cannot be mixed with the coolant of the other circuit. The first coolant 4 can have the same composition of the second coolant 7. In alternative, the first coolant 4 can be different from the second coolant 7. In one example, the first coolant 4 is an ion-free coolant and the second coolant 7 is an ethylene glycol based antifreeze coolant, in particular a G40 coolant. Based on the above described circuit configuration, even if ions (or other polluting elements) would be generated in the second coolant 7, the ions cannot be transported into the first coolant 4 during the heat transfer. Hence, the first coolant 4 - that is in contact with the fuel cell system 5 - would remain an ion-free coolant.

[0032] The first cooling circuit 3 is thermally coupled to the second cooling circuit 6 by means of a heat exchanger 8 so that heat is transferred from one coolant to another coolant. In one example, to increase the heat transfer effect, the heat exchanger 8 can be a plate heat exchanger. In particular, metal plates can be used to transfer heat between the first and second coolant 4, 7. Since the coolants are spread out over the plates, the coolants are exposed to a much larger surface area.

[0033] As mentioned above, the second cooling circuit 6 comprises a high power resistor 9 that is used to heat the second coolant 7 when needed. This type of resistor is advantageously useful in case of converting kinetic energy into heat. In one example, the high power resistor 9 can be part of a regenerative braking system of the vehicle 2. In this way, a system already present in the vehicle, such as the regenerative braking system, can be used with expanded functionalities for another purpose, such as pre-heating the fuel cell system 5. It is noted that a vehicle 2 with an electric drive axle has the possibility of storing kinetic energy inside the battery through the recuperation process. Therefore, such type of vehicles can transform into heat the electric energy coming from the recuperation process. It is noted that to effectively conduct an electric vehicle, the kinetic energy primarily always needs to be stored in the battery. For some battery conditions (i.e. very low state of charge, high state of charge, or at cold cell temperatures), the recuperation process in the battery is not completely possible. In these cases, the high power resistor (HPR) is used to transform the kinetic energy into heat.

[0034] To generate heat, the high power resistor 9 is supplied with electric energy. According to the invention, the high power resistor 9 is supplied with electric energy from the battery of the vehicle 2. In alternative or in addition, the high power resistor 9 is supplied with electric energy from an external power supply, for example using a charging socket of the vehicle 2.

[0035] The dashed line in figure 1 schematically represents a vehicle 2 (car, truck, etc.) comprising the pre-heating system 1. The vehicle 2 can be for example an electric vehicle having a fuel cell system 5 and the first cooling circuit 3 can be a typical cooling circuit connected to the fuel cell system 5. The second cooling system 6 can be, on the other hand, a separated cooling circuit including a high power resistor 9 that is used for warming up the second coolant 7 circulating in the second cooling circuit 6. As already mentioned, the high power resistor 9 can be connected to, or be a part of, another system of the vehicle 2 used for recuperation of kinetic energy.

[0036] Figure 2 illustrates the pre-heating system 1 of figure 1 , wherein some components of the cooling circuits are shown in more detail. The first cooling circuit 3 is the fuel cell cooling circuit and comprises a first coolant pump 12 for regulating the flow of the first coolant 4 inside the circuit 3. The second cooling circuit 6 is the pre-heating cooling circuit and comprises a second coolant pump 13 for regulating the flow of the second coolant 7 inside the circuit 6. In one example, the first coolant pump 12 and the second coolant pump 13 can be activated and controlled to determine a temperature gradient between the first coolant 4 and the second coolant 7 at the heat exchanger 8. In particular, the temperature gradient is such that the temperature of the second coolant 7 is higher than the temperature of the first coolant 4. In this way, heat is transferred from the second coolant 7 to the first coolant 4.

[0037] The fuel cell system 5 can comprise one or more fuel cell modules 14. Figure 2 shows for example a fuel cell system 5 configuration, wherein two fuel cell stack modules 14 are connected in parallel. The first cooling circuit 3 can also comprise a fuel cell radiator 10 for cooling down the temperature of the first coolant 4 and a three-way valve 11 for by-passing the fuel cell radiator 10. The radiator 10 can be a standard element used in a cooling circuit for fuel cells. Based on the necessity, the coolant can pass through the radiator 10, or can bypass the radiator 10, and then enter the fuel cell system 5. The passage through the radiator 10 is used to lower the coolant 4 temperature before entering the fuel cell system 5. The second cooling circuit 6 comprises one or more high power resistors 9. In one example, the second cooling circuit 6 comprises a plurality of high power resistors 9 connected in parallel. Figure 2 illustrates a configuration wherein two high power resistors 9 are used in parallel. Using one or more valves (two-way valves) 15 present in the circuit 6, this configuration gives the possibility of selecting the passage of the coolant 7 across only one or both resistors 9. In principle, it is also possible to close the passage across both the resistors 9 so that the second cooling circuit 6 can be “deactivated”.

[0038] The thermal coupling between the first cooling circuit 3 and the second cooling circuit 6 occurs through a heat exchanger 8. The heat exchanger can be of different types and shapes provided that heat is efficiently transferred from the second coolant 7 (warmed up by the high power resistor 9) to the first coolant 4 passing through the fuel cell system 5. As already mentioned, the heat exchanger 8 can be for example a plate heat exchanger. The heat exchanger 8 can comprise a corresponding heat exchanger interface 16 at both the first cooling circuit 3 and the second cooling circuit 6. According to figure 2, the heat exchanger interface 16 at the first cooling circuit 3 is upstream the fuel cell radiator 10 and the heat exchanger interface 16 at the second cooling circuit 6 is downstream the high power resistor 9. Thanks to the presence of the three-way valve 11 , located downstream the radiator 10, it is possible to control the flow of the first coolant 4 before reaching the fuel cell system 5, e.g. passing only through the radiator 10 or passing only through the radiator bypass. With the presence of the two-way valve 15, it is possible to control the flow of the first coolant 4 through the heat exchanger 8, i.e. the heat exchanger interface 16.

[0039] It is noted that the control of the different components of both the first cooling circuit 3 (e.g. the first coolant pump 12, the three-way valve 11 , the two-way valve 15, etc.) and the second cooling circuit 6 (e.g. the second coolant pump 13, the two-way valve 15, etc.) is carried out by a control unit (not shown in the figure). The control unit can be part of the pre-heating system 1 or can be an external element used for other purposes.

[0040] Figure 3 schematically illustrates in a flow diagram the steps of the method 100 for preheating a fuel cell system 5 of a vehicle 2. This method 100 refers to the use of the pre-heating system 1 as described above with reference to figures 1 and 2. Therefore, all the technical features related to the pre-heating system 1 also apply to the method 100 and vice versa.

[0041] At steps S101 and S102, the method 100 comprises providing a first cooling circuit 3 and a second cooling circuit 6, respectively. At step S103, electrical energy is supplied to the high power resistor 9 of the second cooling circuit 6 and the second coolant 7 is heated. Accordingly, heat is transferred from the second coolant 7 to the first coolant 4 at the heat exchanger 8. Since the two cooling circuits are separated, the heat transfer occurs without any type of mixture between the first coolant 4 and the second coolant 7. According to the invention, the electrical energy can be supplied to the high power resistor 9 from the battery of the vehicle 2 and / or from an external power supply.

[0042] As already mentioned, the electrical energy supplied to the high power resistor 9 can be generated using a regenerative braking system of the vehicle 2.

[0043] The activation and control of the first coolant pump 12 and of the second coolant pump 13 results in the generation of a temperature difference at the heat exchanger 8, for example inside the plate heat exchanger, between the first coolant 4 and the second coolant 7. In particular, at the heat exchanger the temperature of the second coolant 7 can be higher than the temperature of the first coolant 4 so that heat is transferred from the second coolant 7 to the first coolant 4. The heated first coolant 4 can be used by the first cooling circuit 3 to pre-heat the fuel cell system 5.

[0044] It is noted that the pre-heating method, i.e. the heating of the second coolant 7 by supplying electric energy to the high power resistor 9, occurs when the environment conditions at the fuel cell system 5 require a pre-heating, for example when the environmental temperature is below a certain temperature threshold, e.g. 10°C. Accordingly, the pre-heating method is activated after measuring the environmental temperature. For this purpose a temperature sensor is used to first evaluate the temperature of the fuel cell system 5. The temperature sensor is advantageously connected to a control unit (as defined above) for activating and controlling the coolant pumps 12, 13, the valves 11, 15 and the heating of the resistor 9 once the measured temperature is above said threshold temperature.

[0045] Although a variety of techniques and examples of such techniques have been described herein, these are provided by way of example only and many variations and modifications on such examples will be apparent to the skilled person and fall within the spirit and scope of the present invention, which is defined by the appended claims and their equivalents.

[0046] REFERENCE NUMERALS

[0047] 1 Pre-heating system

[0048] 2 Vehicle

[0049] 3 First cooling circuit

[0050] 4 First coolant

[0051] 5 Fuel cell system

[0052] 6 Second cooling circuit

[0053] 7 Second coolant

[0054] 8 Heat exchanger

[0055] 9 High power resistor

[0056] 10 Fuel cell radiator

[0057] 11 Three-way valve

[0058] 12 First coolant pump

[0059] 13 Second coolant pump

[0060] 14 Fuel cell stack module

[0061] 15 Two-way valve

[0062] 16 Heat exchanger interface

Claims

CLAIMS1. Pre-heating system (1) for a vehicle (2) comprising: a first cooling circuit (3) comprising a first coolant (4) circulating therein and connected to a fuel cell system (5) of the vehicle (2) for regulating the operating temperature of said fuel cell system (5); a second cooling circuit (6) comprising a second coolant (7) circulating therein, the second cooling circuit (6) being separated from the first cooling circuit (3); and a heat exchanger (8) for thermally coupling the first cooling circuit (3) to the second cooling circuit (6) and for determining a heat exchange between the first coolant (4) and the second coolant (7), wherein the second cooling circuit (6) comprises at least a high power resistor (9) and wherein the high power resistor (9) is supplied with electric energy from the battery of the vehicle (2) and / or from an external power supply.

2. Pre-heating system (1) according to 2 claim 1, wherein the heat exchanger (8) is a plate heat exchanger.

3. Pre-heating system (1) according to any one of claims 1 to 2, wherein high power resistor (9) is part of a regenerative braking system of the vehicle (2).

4. Pre-heating system (1) according to any one of claims 1 to 3, wherein the second cooling circuit (6) comprises a plurality of high power resistors (9) connected in parallel.

5. Pre-heating system (1) according to any one of claims 1 to 4, wherein the first cooling circuit (3) comprises a fuel cell radiator (10) for cooling down the temperature of the first coolant (4) and a three-way valve (11) for by-passing the fuel cell radiator (10).

6. Pre-heating system (1) according to any one of claims 1 to 5, wherein the first coolant (4) is an ion-free coolant and the second coolant (7) is an ethylene glycol based antifreeze coolant, in particular a G40 coolant.

7. Pre-heating system (1) according to any one of claims 1 to 6, wherein the first cooling circuit (3) comprises a first coolant pump (12) and the second cooling circuit (6) comprises a second coolant pump (13), the first coolant pump (12) and the second coolant pump (13) beingactivated and controlled to determine a temperature gradient between the first coolant (4) and the second coolant (7) at the heat exchanger (8).

8. Pre-heating system (1) according to claim 7, wherein the temperature gradient is such that the temperature of the second coolant (7) is higher than the temperature of the first coolant (4).

9. Vehicle (2) comprising the pre-heating system (1) according to any one of claims 1 to 8.

10. Method (100) for pre-heating a fuel cell system (5) of a vehicle (2), the method (100) comprising: providing (S101) a first cooling circuit (3) comprising a first coolant (4) circulating therein and connected to a fuel cell system (5) of the vehicle (2) for regulating the operating temperature of said fuel cell system (5); providing (S102) a second cooling circuit (6) comprising a second coolant (7) circulating therein, the second cooling circuit (6) being separated from the first cooling circuit (3), wherein the second cooling circuit (6) comprises at least a high power resistor (9) and wherein the second cooling circuit (6) is thermally coupled to the first cooling circuit (3) by means of a heat exchanger (8); and heating (S103) the second coolant (7) by supplying electrical energy to the high power resistor (9) and transferring heat from the second coolant (7) to the first coolant (4) at the heat exchanger (8), wherein the method further comprising: supplying electrical energy to the high power resistor (9) from the battery of the vehicle (2) and / or from an external power supply.

11. Method (100) according to claim 10, comprising: generating electrical energy to be supplied to the high power resistor (9) using a regenerative braking system of the vehicle (2).

12. Method (100) according to any one of claims 10 to 11, comprising: activating and controlling a first coolant pump (12) in the first cooling circuit (3) and a second coolant pump (13) in the second cooling circuit (6) to determine a temperature gradient between the first coolant (4) and the second coolant (7) at the heat exchanger (8).

13. Method (100) according to claim 12, wherein the temperature gradient is such that the temperature of the second coolant (7) is higher than the temperature of the first coolant (4).

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