JP2023546799A - Heat management method for vehicle fuel cell system - Google Patents

Abstract

A power supply system (2) for a vehicle, comprising a hydrogen battery (6), a plurality of ammonia storage cartridges (16), an injection circuit (20) of each cartridge (16) for the battery (6), and a heat transfer system. In this method of thermal management in a system comprising a fluid-containing battery cooling circuit (8) and a heat sink (14), at least one of the cartridges (16) is active and at least one of the cartridges (16) One is passive and includes a) increasing the ammonia pressure inside at least one of the active cartridges (16) and b) directing the heat transfer fluid leaving the battery (6) to at least one of the passive cartridges (16). c) increasing the rate of ammonia desorption in at least one of the active cartridges (16) and storing a portion of the desorbed ammonia in one of the passive cartridges (16); Execute at least one of the following.

Description

The present invention relates to thermal management in vehicles. More particularly, the present invention relates to a fuel cell power supply system for a vehicle and a method for thermal management of the system.

Motor vehicles are equipped with drive means supplied by an energy source, by means of which the vehicle can be moved. One of the most popular energy sources is the internal combustion engine, which runs on fuel. However, since burning fuel generates carbon dioxide that causes air pollution, it is considered preferable to use less polluting energy sources.

It is known to use fuel cells, such as hydrogen cells, in place of internal combustion engines. Oxidation of hydrogen in the form of hydrogen molecules in the battery generates electricity and heat to supply the drive means. Hydrogen can be stored in the form of gaseous ammonia absorbed or adsorbed on salts within the storage cartridge. That is one way to safely store hydrogen. Therefore, to generate hydrogen molecules that can be supplied to batteries, ammonia must be desorbed from the salt and cracking must be performed.

In the context of the description of the present invention, for simplicity, the terms absorption and desorption will be used to refer to the storage and release of gaseous ammonia into and from the salt, respectively, whether the storage is by absorption or not. It does not matter whether it is due to adsorption or not.

"Cool" cells generally exhibit optimal operation at temperatures between 60°C and 80°C. Therefore, it is necessary to discharge the heat generated by the oxidation of hydrogen molecules so that the temperature of the battery does not significantly exceed this value.

Therefore, it is known to absorb heat by passing a cooling fluid in contact with the battery, and then use a radiator to dissipate the heat with the outside air. However, this solution is not always sufficient to keep the battery at optimal operating temperature. In fact, if the ambient temperature is high to begin with, such as in the summer and/or in hot countries, a radiator can dissipate enough heat to keep the battery at its optimal operating temperature due to the temperature difference between the outside air and the battery. There is a possibility that there is no. Furthermore, in situations where the battery has to deliver more electrical energy and therefore generate more heat, the heat sink may not be sufficient to dissipate that excess heat. be.

Since the desorption of ammonia is an endothermic reaction, Patent Document 1 proposes that part of the heat generated in the battery is used to supply the desorption of ammonia in the storage cartridge. Thereby, in addition to the heat sink, another source of heat generated by the battery can be obtained. However, this may not always be sufficient to maintain the temperature of the battery at optimal operating temperature.

International Publication No. 2011107279

The present invention specifically aims to solve this problem by allowing more heat to be dissipated from the battery, especially in situations where the battery is used intensively.

According to the present invention, there is provided a method of thermal management in a power supply system for a vehicle, the system comprising:
- a fuel cell capable of receiving a supply of hydrogen molecules;
- a plurality of cartridges storing ammonia in a matrix-absorbed form;
- an injection circuit connecting the outlet of each cartridge and the inlet of the battery;
- a cooling circuit for the battery in which a heat transfer fluid circulates, the cooling circuit comprising branch pipes supplying each cartridge;
- a radiator capable of cooling the heat transfer fluid;
In a method comprising:
at least one of the cartridges is in an active state that releases gaseous ammonia into the injection circuit; at least one of the cartridges is in a passive state that does not release gaseous ammonia into the injection circuit;
a) increasing the ammonia pressure inside at least one of the cartridges in the active state;
b) circulating the heat transfer fluid exiting the battery through at least one of the cartridges in a passive state;
c) increasing the rate of ammonia desorption in one of the cartridges in the active state and storing a portion of the desorbed ammonia in one of the other cartridges, preferably in one of the cartridges in the passive state;
A method is provided for performing at least one of the following.

Therefore, a temporary heat demand can be created for the ammonia storage cartridge. Step a) may shift the thermodynamic equilibrium within the cartridge. By being able to increase the ammonia pressure within the cartridge, the temperature required to reach equilibrium can be increased, thus increasing the heat demand of that cartridge. In other words, the additional absorption of heat results in an increase in the temperature within the cartridge, thereby indirectly increasing the ammonia pressure within the cartridge. Step b) may store heat in at least one cartridge in a passive state, thereby preventing that cartridge from switching to an active state. Step c) may create an excess of ammonia in the at least one cartridge in the active state compared to the instantaneous consumption of the battery, and thus an excess of heat consumption in that cartridge.

Each of these steps can temporarily increase the heat dissipated by the cartridge, which therefore needs to be evacuated using a heatsink to keep the battery close to its optimal operating temperature. Heat generated by batteries can be reduced.

Advantageously, at least two of step a), step b) and step c) are carried out.

Advantageously, three steps are carried out: step a), step b) and step c).

This can further increase the amount of heat that is consumed by the system out of the battery. It also makes it possible to flexibly adjust the amount of thermal energy consumed by the cartridge.

In a particular embodiment, step d) of reducing the power of the battery is performed.

Advantageously, in step a) the pressure of at least one of the cartridges in the active state is increased to a value greater than 3 bar, preferably greater than 4 bar and even more preferably greater than 5 bar.

By increasing the pressure in this way, the thermodynamic equilibrium temperature within the cartridge can be significantly increased. For example, if the matrix is calcium chloride, increasing the pressure from 2 bar to 5 bar shifts the equilibrium temperature from approximately 45°C to 65°C.

Advantageously, the cartridges each contain a matrix of calcium chloride capable of absorbing and desorbing ammonia.

This salt can efficiently store ammonia.

More generally, the matrix can take the form _of a salt with the basic chemical formula M _a (NH ₃ ) _n Alkali metals, alkaline earth metals such as Mg, Ca or Sr, and/or transition metals such as V, Cr, Mn, Fe, Co, Ni, Cu or Zn, or NaAl, KAl, _K2Zn , CsCu or K ₂ Fe and X is one or more cations selected from among those compounds such as fluoride, chloride, bromide, iodide, nitrate, thiocyanate, sulfate, molybdate and one or more anions selected from phosphates, a is the number of cations per molecule of salt, z is the number of anions per molecule of salt, and n is the coordination The numbers range from 2 to 12.

Advantageously, the injection circuit comprises an ammonia cracking module capable of converting ammonia into a gas mixture comprising nitrogen molecules, hydrogen molecules and ammonia and, if necessary, reducing the ammonia content of the gas mixture. It further includes a purification module.

Therefore, it is possible to supply a gas mixture with particularly high hydrogen molecular purity to the battery. Therefore, the present invention is directed to a battery that requires a high purity level of hydrogen for operation, using the term "PEMFC", which is an abbreviation for the English-speaking term "Proton Exchange Membrane Fuel Cell". It is particularly applicable to type batteries.

Advantageously, the method is carried out in a vehicle.

According to the present invention, in the vehicle power supply system,
- a fuel cell capable of receiving a supply of hydrogen molecules;
- a plurality of cartridges storing ammonia in a matrix-absorbed form;
- an injection circuit connecting the outlet of each cartridge and the inlet of the battery;
- a cooling circuit for the battery in which a heat transfer fluid circulates, the cooling circuit comprising branch pipes supplying each cartridge;
- a radiator capable of cooling the heat transfer fluid;
- a control unit capable of carrying out the aforementioned thermal management method;
Provides a system with.

According to the invention there is also provided a motor vehicle comprising the aforementioned supply system.

The invention will now be introduced through the following description, given by way of example only and with reference to the accompanying drawings, in which: FIG.

1 is a diagram showing a vehicle power supply system according to a first embodiment of the present invention. FIG. 3 is a diagram showing a vehicle power supply system according to a second embodiment of the present invention.

FIG. 1 shows a power supply system 2 for a vehicle 4 according to a first embodiment of the invention.

The power supply system 2 includes a hydrogen fuel cell 6 . This is more specifically referred to as "AMFC", which stands for Alkaline Membrane Fuel Cell (Alkaline Membrane Fuel Cell) in English-speaking parlance, or "Proton Exchange Membrane Fuel Cell" (Proton Exchange Membrane Fuel Cell) in English-speaking parlance. It is generally referred to as "PEMFC". These types of batteries are known in the art today and their operation will not be described in detail below.

The battery 6 is configured to obtain the generation of electrical energy by oxidizing the supplied hydrogen molecules, and the electrical energy is transmitted to the driving means (not shown) of the vehicle 4. Since this oxidation reaction is an exothermic reaction and simultaneously generates heat, the temperature also rises when the battery 6 is in operation.

To cool the battery 6, the supply system 2 is equipped with a battery cooling circuit 8. The cooling circuit 8 is a conduit through which a heat transfer fluid flows, and has a conduit through which the heat transfer fluid can exchange heat with the battery 6 through a path in contact with the battery 6 . The battery 6 has an optimum operating temperature (here, around 70° C.) at which efficiency is maximized. To monitor the temperature of the battery 6 , the cooling circuit 8 comprises temperature sensors located upstream and downstream of the battery 6 along the direction of circulation of the heat transfer fluid within the cooling circuit 8 . Circulation of the heat transfer fluid within the cooling circuit 8 is made possible by a pump 12 located on the output side of the battery 6. In FIG. 1, the direction of circulation of the heat transfer fluid within the cooling circuit 8 is indicated by arrows.

The supply system 2 comprises a heat sink 14 through which the cooling circuit 8 passes. The heat radiator 14 is exposed to the outside air so that the heat transfer fluid passing through the radiator 14 can exchange heat with the outside air to cool the heat transfer fluid.

The supply system 2 comprises a plurality of storage cartridges 16, each containing a matrix 18 capable of storing gaseous ammonia, a precursor of molecular hydrogen. The ammonia is absorbed by the matrix 18, but it can also be adsorbed to the matrix 18. The matrix 18 may therefore consist of a salt, for example calcium chloride. Calcium chloride is particularly advantageous since one calcium chloride molecule can bind eight ammonia molecules.

The supply system 2 comprises an injection circuit 20 connecting the outlet of each cartridge 16 and the inlet of the battery 6. Injection circuit 20 serves to pass ammonia from cartridge 16 to battery 6 . The injection circuit 20 includes a temperature sensor 10 capable of measuring the temperature of ammonia and a check valve 21 at the outlet of each cartridge 16. The check valve 21 allows the cartridge 16 with an ammonia pressure above the ammonia pressure at the inlet of the injection circuit 20 to desorb ammonia and inject it into the injection circuit 20.

The injection circuit 20 comprises a metering unit 22 that is able to meter the amount of ammonia delivered towards the battery. A pressure sensor 24 is placed at the inlet of the metering unit 22 to measure the pressure of ammonia entering the metering unit 22.

The injection circuit 20 includes a cracking module 26 downstream of the metering unit 22 along the direction of circulation of ammonia in the injection circuit 20, in which an ammonia cracking reaction takes place. This reaction can produce a gas mixture containing nitrogen molecules, hydrogen molecules, and ammonia from ammonia.

The injection circuit 20 comprises, downstream of the cracking module 26 along the direction of circulation of ammonia in the injection circuit 20, a purification module 28 capable of reducing the ammonia content of the gas mixture. This purification step is particularly important if the cell is of the "PEMFC" type. This is because this type of battery requires a supply of particularly pure hydrogen molecules. The mixed gas exiting the purification module 28 is supplied to the battery 6, where hydrogen molecules are oxidized.

The cooling circuit 8 includes a three-way valve 30 that receives supply from the outlet of the pump 12. A portion of the heat transfer fluid leaving pump 12 is directed toward radiator 14 . The remaining heat transfer fluid is directed toward branch pipes 32 that supply each cartridge 16. Branch pipe 32 is configured such that each cartridge 16 is attached in parallel. Each of the branch pipes 32 that supply the cartridges 16 is provided with a fully open and fully closed valve 34 so that the cartridges 16 through which the heat transfer fluid must pass can be constantly controlled. The heat transfer fluid leaving the cartridge 16 is directed by the cooling circuit 8 towards the radiator 14 .

The feeding system 2 comprises a control unit 36 capable of controlling the operation of each element of the feeding system.

From now on, a method of thermal management of the supply system 2 carried out in the vehicle by the control unit 36 will be described.

In the nominal operating phase, the battery 6 is capable of generating an electrical output of approximately 100 kW. The battery has an efficiency of approximately 50%, so it consumes 200 kW of chemical power while providing an additional 100 kW of thermal power in the form of heat. To reach this chemical output, it is necessary to supply the cell with a mass flow rate of 10.75 g/s (corresponding to a molar flow rate of 0.63 mol/s) of ammonia. Some of the cartridges 16 are then placed in an active state where they release gaseous ammonia into the injection circuit 20, and the remaining cartridges 16 are placed in a passive state where they do not release gaseous ammonia into the injection circuit 20. The heat power that cartridge 16 would need to consume in order to desorb this amount of ammonia per second is 26 kW. Therefore, in order to avoid a rise in the temperature of the battery 6 that could exceed the optimum operating temperature, it is still necessary to discharge the heat output of 74 kW using the radiator 14 or the like.

Depending on the outside temperature, the radiator 14 may not be able to dissipate all of the heat output that it must dissipate. It is also possible that the vehicle 4 is placed in a situation requiring a greater electrical output from the battery 6, which would then involve a greater thermal output that would need to be dissipated.

In order to temporarily increase the heat output dissipated by the supply system 2, the control unit 36 performs at least one of the following operations.
a) increasing the ammonia pressure inside at least one of the cartridges 16 in the active state; Thereby, the thermodynamic equilibrium within the cartridge can be shifted. Doing so increases the temperature required to reach equilibrium and therefore increases the heat demand of that cartridge. In this case, by increasing the pressure from 2 bar to 5 bar (absolute), the equilibrium temperature shifts from approximately 45°C to 65°C. It can therefore be seen that the cartridge needs to absorb more heat emitted by the battery in order to maintain its equilibrium state.
b) circulating the heat transfer fluid exiting the battery 6 to at least one of the cartridges 16 in a passive state; Monitoring of the temperature within the cartridge must then take place. This is because a threshold temperature must not be exceeded at which the cartridge becomes active, ie the desorption of ammonia begins in the cartridge and the supply to the injection circuit 20 takes place. However, the cartridge may absorb a certain amount of thermal energy before reaching its threshold temperature.
d) If possible, the electrical output generated by the battery 6 can be reduced. As a result, the heat output generated by the battery 6 will be reduced, i.e. the heat output that the heat sink 14 has to dissipate, the remaining heat that should be dissipated but cannot be dissipated by the heat sink 14. This will reduce the output.

Depending on the heat output that cannot be dissipated by the heat sink 14, one can choose to carry out one or two of actions a) and b) and, if possible, action d). Also, these operations can be performed over different time periods. Therefore, it can be seen that the present invention allows agile management of the dissipation of thermal power generated by the battery 6.

FIG. 2 shows a power supply system 2' for a vehicle 4 according to a second embodiment of the invention. Elements similar to those in the first embodiment are given the same reference numerals.

A second embodiment of the present invention is a recycling system in which the injection circuit 20 is a fully open fully closed valve 34 arranged in parallel with the cartridge 16, and is opened and closed by the fully open fully closed valve 34 which is controlled by a control unit 36. This embodiment differs from the first embodiment in that the circuit 38 is provided in the opposite direction to the metering unit 22. Downstream of this valve, the recycle circuit 38 includes a reinsertion branch 40 to each of the cartridges 16 through which ammonia exits the cartridge 16. A check valve 21 is provided to prevent this.

System 2' functions in the same way as the system according to the first embodiment. The system may also perform other operations to increase the heat output consumed by the system. That is,
c) increasing the rate of ammonia desorption in one of the cartridges 16 in the active state and storing a portion of the desorbed ammonia in one of the cartridges 16 in the passive state; The surplus ammonia thus removed passes through the recycle circuit 38 and reenters the cartridge 16 in the passive state through the check valve 21 of the corresponding re-insertion branch pipe 40 due to the pressure difference.

Acts a), b), and optionally d) can be performed simultaneously with act c) to increase the amount of heat output used by the system 2'.

The invention is not limited to the embodiments introduced, but other embodiments will be obvious to those skilled in the art.

2, 2' Energy supply system 4 Vehicle 6 Battery 8 Cooling circuit 10 Temperature sensor 12 Pump 14 Heat sink 16 Storage cartridge 18 Matrix 20 Injection circuit 21 Check valve 22 Metering unit 24 Pressure sensor 26 Cracking module 28 Purification module 30 Three-way valve 32 Branch pipe 34 Fully open and fully closed valve 36 Control unit 38 Recycling circuit 40 Re-insertion branch pipe

Claims (10)

A thermal management method in a vehicle power supply system (2, 2'), the power supply system comprising:
- a fuel cell (6) capable of receiving a supply of hydrogen molecules;
- a plurality of cartridges (16) storing ammonia in absorbed form in a matrix (18);
- an injection circuit (20) connecting the outlet of each said cartridge (16) and the inlet of said fuel cell (6);
- a cooling circuit (8) in which a heat transfer fluid circulates, comprising branch pipes (32) supplying each said cartridge (16);
- a radiator (14) capable of cooling the heat transfer fluid;
In a thermal management method comprising:
At least one of said cartridges (16) is in an active state discharging gaseous ammonia into said injection circuit (20) and at least one of said cartridges (16) is in a passive state discharging gaseous ammonia into said injection circuit (20). can be,
a) increasing the ammonia pressure inside at least one of said cartridges (16) in said active state;
b) circulating the heat transfer fluid leaving the fuel cell (6) to at least one of the cartridges (16) in the passive state;
c) increasing the rate of ammonia desorption in one of the cartridges (16) in the active state and transferring a portion of the desorbed ammonia to another one of the cartridges (16), preferably in the passive state; storing in one of the cartridges (16);
A thermal management method characterized by performing at least one of the following. The thermal management method according to claim 1, wherein at least two of the steps a), b) and c) are performed. The thermal management method according to claim 1 or 2, wherein the three steps of step a), step b) and step c) are performed. Thermal management method according to any one of claims 1 to 3, further comprising performing step d) of reducing the output of the fuel cell (6). From claim 1, wherein in step a) the pressure of at least one of the cartridges (16) in the active state is increased to a value greater than 3 bar, preferably greater than 4 bar, and even more preferably greater than 5 bar. 4. The heat management method according to any one of 4. The thermal management method according to any one of claims 1 to 5, wherein the cartridges (16) each contain a calcium chloride matrix (18) capable of absorbing and desorbing ammonia. The injection circuit (20) includes an ammonia cracking module (26) capable of converting ammonia into a gas mixture comprising nitrogen molecules, hydrogen molecules and ammonia, and a purification module capable of reducing the ammonia content of the gas mixture. A thermal management method according to any one of claims 1 to 6, comprising a module (28). Thermal management method according to any one of claims 1 to 7, carried out in a vehicle (4). In the vehicle power supply system (2, 2),
- a fuel cell (6) capable of receiving a supply of hydrogen molecules;
- a plurality of cartridges (16) storing ammonia in absorbed form in a matrix (18);
- an injection circuit (20) connecting the outlet of each said cartridge (16) and the inlet of said fuel cell (6);
- a cooling circuit (8) in which a heat transfer fluid circulates, comprising branch pipes (32) supplying each said cartridge (16);
- a radiator (14) capable of cooling the heat transfer fluid;
- a control unit (36) capable of implementing the thermal management method according to any one of claims 1 to 8;
A power supply system comprising: A motor vehicle (4) comprising a power supply system (2, 2') according to claim 9.

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