Method for reducing hydrogen loss

Abstract

The present invention relates to a method for reducing hydrogen loss in a liquid hydrogen storage tank, the storage tank being refillable and mounted on a vehicle to feed the vehicle, the storage tank being provided with a vent for discharging gaseous hydrogen to the outside of the storage tank under overpressure, the method comprises: providing data regarding a next refill of the liquid hydrogen storage tank according to a next parking operation planned by the vehicle after the next refill, the data providing at least a target fill level to be reached for the next refill of the storage tank, the target filling level is determined in such a way that, after a possible travel of the vehicle between refilling to the target filling level and the start of the parking operation, the storage tank has a parking start filling level at the start of the parking operation of the vehicle, the parking start fill level is designed such that the loss of hydrogen via the tank vent is minimized for the duration of the next parking operation of the vehicle. The invention also relates to a system for reducing hydrogen loss in a liquid hydrogen storage tank.

Description

Technical Field

[0001] The present invention relates to a method for reducing hydrogen boil-off losses in a liquid hydrogen storage tank which is refillable and mounted on a vehicle. Background Art

[0002] Cryogenic storage of hydrogen in vehicles (cars, trucks, ships, trains, airplanes, etc.) increases the range of the vehicle. A major drawback associated with this storage method is the vaporization of hydrogen (a phenomenon known as "boiling off"), which is caused by heat transfer between the outside and the hydrogen stored at a temperature of 20-150 Kelvin. The vaporization results in losses via the exhaust, which increases the carbon footprint and operating costs. There is an urgent need to reduce these losses. Summary of the invention

[0003] The present invention is particularly intended to overcome this problem.

[0004] The present invention therefore relates to a method for reducing hydrogen gasification losses in a liquid hydrogen tank, which tank is refillable and is mounted onboard a vehicle (land, sea, air or space) in order to feed, for example, a fuel cell of the vehicle, the tank being provided with a vent for venting gaseous hydrogen outside the tank in the event of overpressure, the method comprising the following steps:

[0005] - providing data on the next refilling of the liquid hydrogen tank according to the next parking operation planned for the vehicle after the next refilling, the next refilling data providing at least a target filling level (L -目标 ), the target filling level (L -目标 ) is determined in such a way that: when the vehicle is refilled to the target filling level (L -目标 ) and the start of the parking operation, at the start of the parking operation of the vehicle, the tank has a parking start filling level (L -停放 ), the parking starts filling level (L -停放 ) is designed so that the loss of hydrogen through the tank vent is minimized during the duration of this next parking operation of the vehicle.

[0006] The invention advantageously enables the use of data relating to said next refilling of the tank to guide the driver / pilot of a vehicle equipped with a cryogenic liquid hydrogen tank in order to optimize the refilling strategy and minimize boil-off losses. The invention is particularly advantageous for intensive use applications, such as for trucks that are used all day / all day, alternating between driving phases and parking phases.

[0007] During the parking phase of the vehicle, when hydrogen gasification may occur, it is important to place the tank in a condition / state that minimizes losses via the vent. The present invention makes this possible.

[0008] In the present invention, during the parking phase (i.e. the vehicle is stopped, the engine is turned off), the liquid hydrogen tank stops feeding the fuel cell. The parking phase is in particular different from a simple stop at a red light or a short stop at a service station to refill the hydrogen tank. Parking within the meaning of the present invention means that the fuel cell is idle / resting at this time.

[0009] According to one aspect of the invention, the duration of parking is at least one hour or at least two hours, or indeed longer, such as at least five hours or at least eight hours.

[0010] It should be noted that the extraction of hydrogen from the battery reduces the pressure in the tank while the vehicle is in motion. Furthermore, the pressure increase due to thermodynamic stratification (formation of thermal gradients along the height of the tank) is more severe in a static tank than in a moving tank. Therefore, the "boil-off" phenomenon is less important / not critical while in motion.

[0011] The object of the invention is to determine the target filling level (L -目标 ) so that at the start of the parking operation, the tank is filled to the parking start filling level (L -停放 In practice, the user / driver does not necessarily need to know the parking start filling level (L -停放 The user / driver needs to know the target fill level (L -目标 ), because he or she will refill the tank knowing this target level. For example, the user / driver can enter the level value (L -目标 ), the station automatically refills the tank to this level (L -目标 ). The liquid level (L -目标 ) can also be reached manually by the user. As a variant, in the case where refilling occurs fully automatically, the user / driver does not need to know the target fill level (L -目标 ), and the filling station receives the data to automatically perform the refilling operation.

[0012] According to one of the aspects of the invention, the vehicle equipped with the liquid hydrogen tank is a road motor vehicle, such as a truck, in particular a truck weighing at least 3.5 tons, or a bus, in particular a bus with at least 8 seats.

[0013] According to one of the aspects of the present invention, the vehicle equipped with the liquid hydrogen storage tank is a train, a ship or an airplane.

[0014] According to one aspect of the present invention, the target filling level (L) provided by the next refilling data -目标 ) is related to the time (date / time) when the next refill is planned.

[0015] According to one of the aspects of the present invention, the next refilling data is determined at least according to the duration of the next parking operation of the vehicle.

[0016] According to one of the aspects of the invention, the duration of parking is at least one hour or at least two hours, or indeed longer, such as at least five hours or at least eight hours.

[0017] According to one of the aspects of the invention, the next refill data is determined based on at least a sleep parameter representing a waiting time before venting the tank (via the vent) due to the pressure increase in the tank when hydrogen is gassed.

[0018] For a given situation, the higher the value of this dormancy parameter, the longer the time delay in releasing boil-off hydrogen from the tank. This is advantageous because it helps to reduce boil-off losses.

[0019] According to one aspect of the present invention, the determination of the next refilling data uses a thermodynamic model, which provides sleep parameters and a parking start filling level (L -停放 ) and may also relate the value of the dormant parameter to the pressure within the tank / the thermodynamic model may also relate to the pressure within the tank.

[0020] According to one aspect of the present invention, the thermodynamic model is in the form of a correspondence table, which converts the tank filling percentage (or the parking start filling level (L -停放 )) is associated with the value of the dormant parameter and it is also possible to associate the pressure in the tank with the value of the dormant parameter / it is also possible to associate the tank filling percentage or the parking start filling level (L -停放 ) is related to the pressure inside the tank.

[0021] By providing next refilling data for refilling the tank at a refueling station, the method according to the invention makes it possible to ensure that during the next parking operation of the vehicle the target refilling level (L -目标 ) is adapted to the duration of the parking. By using thermodynamic models and predicting the journey of the vehicle and more generally the route planning of the vehicle, the hydrogenation occurring during the parking phase is minimized.

[0022] According to one of the aspects of the present invention, the next refilling data is determined based on two different thermodynamic models, for example, one of the models is used if the duration of the next parking operation is less than / below a predetermined threshold, and the other model is used if the duration of the next parking operation of the vehicle is above / greater than the predetermined threshold.

[0023] As described above, one of the models may use dormant parameters, while the other thermodynamic model may, for example, use parameters that reflect the cumulative amount of vaporized hydrogen vented from the storage tank.

[0024] Thus, in particular depending on the duration of the next parking operation of the vehicle, the next refilling data may be determined based on one or the other of the two models as a function of the duration of the next parking operation.

[0025] For example, if liquid hydrogen is stored in a tank at a pressure of 10 bar, the dormancy parameter maximum value is 50%.

[0026] For example, the thermodynamic model uses parameters that reflect the cumulative amount of vaporized hydrogen exhausted from the storage tank.

[0027] According to one of the aspects of the present invention, in case the next parking operation of the vehicle lasts N hours, the next refilling data is determined by taking into account this parking duration of the vehicle.

[0028] According to one of the aspects of the present invention, the next refilling data also takes into account liquid hydrogen consumption during the vehicle journey between the time when the next refilling data is provided and the time when the vehicle arrives at the liquid hydrogen refueling station.

[0029] According to one of the aspects of the invention, the next refill data also takes into account the possible journey the vehicle needs to make between the refueling station and where the vehicle will be parked, such as a parking lot or garage.

[0030] According to one of the aspects of the invention, the next refilling data is further determined based on vehicle trip data and / or data related to the vehicle surroundings (eg external temperature).

[0031] According to one of the aspects of the invention, the next refilling data is further determined based on data related to a travel history of the vehicle.

[0032] According to one aspect of the present invention, the travel data of the vehicle is, for example, the average mileage of the vehicle on a normal travel day.

[0033] According to one of the aspects of the invention, the trip data also includes a typical time when the vehicle is parked, such as 7:00 PM, for example, when work for the day has been completed.

[0034] For example, when a vehicle is parked overnight, the duration of the parking may be set to 8 hours or 12 hours.

[0035] According to one of the aspects of the present invention, the next refilling data can also be determined based on data input by the user via the human-machine interface. The input data relates to, for example, a trip that the user plans to take, in particular a trip just before the next refilling and a trip just after the next refilling.

[0036] The invention also relates to a system for reducing hydrogen vaporization losses (evaporation) in a liquid hydrogen tank, the tank being refillable and mounted onboard a vehicle (land, sea, air or space) in order to feed, for example, a fuel cell of the vehicle, the tank being provided with an exhaust port for discharging gaseous hydrogen outside the tank in the event of overpressure, the system being configured as follows:

[0037] - providing data on the next refilling of the liquid hydrogen tank according to the next parking operation planned for the vehicle after the next refilling, the next refilling data providing at least a target filling level (L -目标 ), target filling level (L -目标 ) is determined in such a way that: when the vehicle is refilled to the target filling level (L -目标 ) and the start of the parking operation, at the start of the parking operation of the vehicle, the tank has a parking start filling level (L -停放 ), parking start filling level (L -停放 ) is designed so that the loss of hydrogen through the tank vent is minimized during the duration of this next parking operation of the vehicle.

[0038] According to one of the aspects of the invention, the system comprises a data processing unit, in particular a computer, configured to: receive data on the duration of a next parking operation of the vehicle; and determine a target filling level (L ) of the tank for the next refilling at least as a function of the duration of the next parking operation of the vehicle. -目标 ) related data.

[0039] According to one of the aspects of the present invention, the data processing unit is configured to: receive vehicle trip data and / or data related to the vehicle surroundings, such as external temperature; and determine a target filling level (L) of the tank for the next refilling.-目标 ) related data.

[0040] According to one of the aspects of the present invention, the data processing unit is installed on a vehicle (as an onboard computer of the vehicle) and can communicate with a remote server.

[0041] An onboard vehicle-mounted data processing unit links to remote server-based software for more complex computing operations.

[0042] According to one of the aspects of the invention, the data processing unit is remote (remotely connected to the vehicle).

[0043] In particular, the data processing unit is a remote computing unit, the memory of which contains typical driving cycles.

[0044] According to one of the aspects of the invention, the system comprises a human-machine interface for providing the driver with a target filling level (L) of the tank for the next refilling. -目标 ) related information.

[0045] According to one aspect of the present invention, the system is configured to perform at least some of the following steps:

[0046] - Processing data from sensors, such as meters measuring the level of liquid hydrogen in a tank;

[0047] - Processing of driving cycle related data;

[0048] - Retrieve the trip history of a vehicle;

[0049] -Communicate with the liquid hydrogen refueling network database and GPS;

[0050] - calculation of next refilling data, which in particular comprises the next refuelling location, the timetable and the target filling level (L -目标 )

[0051] - Displaying the next refill data to the user via the human-machine interface.

[0052] According to one of the aspects of the present invention, at least one pressure sensor and / or at least one liquid level sensor is placed in the liquid hydrogen storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Other characteristics, details and advantages of the invention will become more apparent from reading the following description, with reference to the attached schematic drawings, as well as from reading a number of exemplary embodiments given by way of non-limiting indication, in which:

[0054] Figure 1 is a schematic diagram of a system for reducing hydrogen loss according to the present invention;

[0055] Figure 2 Shows Figure 1 The sleep curve used by the system;

[0056] Figure 3 A curve showing the amount of hydrogen discharged;

[0057] Figure 4 is a block diagram illustrating a method according to one embodiment of the present invention. DETAILED DESCRIPTION

[0058] The features, variations and different embodiments of the present invention may be associated with each other in various combinations, as long as they are not mutually incompatible or mutually exclusive. In particular, if only selecting some of the following features without selecting other features is sufficient to make the present invention have a technical advantage over the prior art and / or to distinguish the present invention from the prior art, it is conceivable that the variation of the present invention only includes the selection of the said part of the features.

[0059] Figure 1 A system 100 is shown for reducing hydrogen vaporization losses (or "boil-off") in a liquid hydrogen storage tank 10 that is refillable and mounted on a highway vehicle V (in this case a truck) to feed a fuel cell (not shown here) of the vehicle V.

[0060] The storage tank 10 is provided with an exhaust port 11 for discharging gaseous hydrogen to the outside of the storage tank 10 in an overpressure condition.

[0061] The system 100 is configured to provide data on the next refilling of the liquid hydrogen storage tank 10 according to the next parking operation that the vehicle is scheduled to perform after the next refilling, and the next refilling data at least provides a target filling level (L ) to be achieved for the next refilling of the storage tank 10. -目标 ), the target filling level (L -目标 ) is determined in such a way that: when the vehicle is refilled to the target filling level (L -目标 ) and the start of the parking operation, at the start of the parking operation of the vehicle V, the tank 10 has a parking start filling level (L -停放 ), the parking starts filling level (L -停放 ) is designed so that the loss of hydrogen via the tank vent 10 is minimized during the duration D of this next parking operation of the vehicle.

[0062] These aspects are described in more detail below.

[0063] The system 100 comprises a data processing unit 101, such as a computer, which is configured to:

[0064] - receiving data on the duration of the next parking operation of the vehicle and determining a target filling level (L ) of the tank 10 for the next refilling at least as a function of the duration of this next parking operation of the vehicle -目标 ) related data; and / or

[0065] - receiving vehicle trip data and / or data relating to the vehicle's surroundings, such as the outside temperature, and determining a target filling level (L) of the tank for the next refilling -目标 ) related data.

[0066] The data processing unit 101 is installed on the vehicle V and can communicate with a remote server 120 (also referred to as the cloud).

[0067] The data processing unit 101 installed on the vehicle V is linked to a computer 130 on a remote server 120 for more complex computing operations.

[0068] The remote server 120 contains data in memory 135 relating to the history of drive cycles and / or fill cycles.

[0069] Therefore, the next refill data is determined by taking into account data related to the trip history of vehicle V, if applicable.

[0070] The travel data of the vehicle V is, for example, the average mileage of the vehicle on a normal travel day.

[0071] The trip data also includes typical times when the vehicle is parked, such as 6:00 pm or 7:00 pm, for example, when work for the day has been completed.

[0072] For example, when a vehicle is parked overnight, the duration of the parking may be set to 8 hours, 10 hours, or 12 hours.

[0073] The next refilling data may also be determined based on data input by the user via the human-machine interface 105. The input data relates, for example, to a trip that the user plans to make, in particular a trip just before the next refilling and a trip just after the next refilling.

[0074] A human-machine interface 105, such as a touch screen permanently installed in the vehicle V or a smartphone in the hands of the driver C, is used to provide the driver with a target filling level (L ) of the tank for the next refilling. -目标 ) related information.

[0075] Remote server 120 contains a database 137 of liquid hydrogen refueling station locations, for example in the form of a liquid hydrogen refueling station network map. This database 137 may be updated regularly.

[0076] The system 100 is configured to perform the following steps:

[0077] - Processing data from the sensor 111, such as a meter for measuring the liquid hydrogen level in the tank 10;

[0078] - Processing of driving cycle related data;

[0079] - retrieving the travel history of the vehicle from the memory 135;

[0080] -Communicate with the liquid hydrogen refueling network database 137 and GPS;

[0081] - calculation of next refilling data, which in particular comprises the next refuelling location, the timetable and the target filling level (L -目标 )

[0082] - Displaying the next refill data to the user via the human-machine interface 105 .

[0083] At least one pressure sensor 111 and / or at least one liquid hydrogen level sensor 111 is placed in the liquid hydrogen storage tank 10 .

[0084] The system 100 may be used to implement a method for reducing hydrogen gasification losses via the vent 11 of the storage tank 10, the method comprising the following steps:

[0085] - providing data on the next refilling of the liquid hydrogen tank 10 according to the next parking operation planned for the vehicle V after the next refilling, the next refilling data providing at least a target filling level (L -目标 ), the target filling level (L -目标 ) is determined in such a way that when the vehicle is refilled to the target filling level (L -目标 ) and the start of the parking operation, at the start of the parking operation of the vehicle V, the tank 10 has a parking start filling level (L -停放 ), the parking starts filling level (L -停放 ) is designed so that the loss of hydrogen via the tank vent is minimized during the duration of this next parking operation of the vehicle V.

[0086] The invention advantageously enables the use of data relating to said next refilling of the tank 10 to guide the driver / pilot of a vehicle equipped with a cryogenic liquid hydrogen tank, in order to optimize the refilling strategy and minimize losses via the exhaust port 11. The invention is particularly advantageous for intensive use applications, such as for trucks in full day / all day use alternating between driving phases and parking phases.

[0087] During the parking phase of the vehicle, when hydrogen gasification may occur, it is important to place the tank in a condition / state that minimizes losses via the vent. The present invention makes this possible.

[0088] In the present invention, during the parking phase (i.e. the vehicle is stopped, the engine is turned off), the liquid hydrogen tank stops feeding the fuel cell. The parking phase is in particular different from a simple stop at a red light or a short stop at a service station to refill the hydrogen tank. Parking within the meaning of the present invention means that the fuel cell is idle / resting at this time.

[0089] According to one of the aspects of the invention, the duration of parking is at least one hour or at least two hours, or indeed longer, such as at least five hours or at least eight hours.

[0090] The object of the invention is to determine the target filling level (L -目标 ) so that at the start of the parking operation, the tank is filled to the parking start filling level (L -停放 In practice, the user / driver does not necessarily need to know the parking start filling level (L -停放 The user / driver needs to know the target fill level (L -目标 ), because he or she will refill the tank knowing this target level. For example, the user / driver can enter the level value (L -目标 ), the station automatically refills the tank to this level (L -目标 ). The liquid level (L -目标 ) can also be reached manually by the user. As a variant, in the case where refilling occurs fully automatically, the user / driver does not need to know the target fill level (L -目标 ), and the filling station receives the data to automatically perform the refilling operation.

[0091] Preferably, the target filling level (L -目标 ) is related to the time (date / time) when the next refill is planned.

[0092] Preferably, the next refilling data are determined at least in dependence on the duration of a next parking operation of the vehicle.

[0093] Preferably, the duration of parking is at least one hour or at least two hours, or indeed longer, such as at least five hours or at least eight hours.

[0094] In the example described, the next refilling data are determined at least as a function of a dormancy parameter DORM which represents the waiting time before venting the tank (via the vent 11 ) due to the pressure increase in the tank when hydrogen is gasified.

[0095] In this case, the dormancy parameter DORM uses days as units and assumes a 5 watt heat input to the tank.

[0096] Figure 2 The C1-C4 curve is shown, with the filling level L of the tank on the X-axis. -停放 (expressed as a percentage of the filling of the tank 10), and on the Y-axis is the dormancy parameter DORM (expressed in days).

[0097] For a given situation, the higher the value of the dormancy parameter DORM, the longer the time delay for releasing the vaporized hydrogen from the tank. This is advantageous because it helps to reduce losses via the exhaust port 11.

[0098] Curve C1 corresponds to a model of the variation of the dormancy parameter DORM for liquid hydrogen LH2 at a pressure in the range from 6 bar to 10 bar (but at a 100% filling value the pressure is in the range from 8 bar to 10 bar).

[0099] Curve C2 corresponds to a model of the variation of the dormancy parameter DORM of supercooled liquid hydrogen sLH2 at a pressure in the range 6 to 20 bar (but at a 100% filling value the pressure is in the range 16 to 20 bar).

[0100] Curve C3 corresponds to the model for the case involving liquid hydrogen LH2 with a pressure varying from 1 bar to 10 bar.

[0101] Curve C4 corresponds to the model for the case involving hydrogen sLH2 with a pressure varying from 1 bar to 20 bar.

[0102] For example, curve C1 shows that the dormancy parameter DORM is maximum when the filling level is 80%.

[0103] Curve C2 shows that the dormancy parameter DORM is maximum when the filling level is 50%.

[0104] It can be seen that, surprisingly, filling the tank to 100% is not always desirable if the aim is to reduce the risk of hydrogen being lost via the vent.

[0105] The next refilling data is determined using a thermodynamic model that provides the dormant parameters and the parking start filling level (L -停放 ) and it is also possible to relate the value of the dormant parameter to the pressure within the tank.

[0106] In the example described, the thermodynamic model takes the form of a correspondence table that maps the tank fill percentage (or the parking start fill level (L -停放 )) is associated with the value of the dormant parameter, and it is also possible to associate the pressure within the tank with the value of the dormant parameter.

[0107] By providing the next refilling data for refilling the tank at a refueling station, the method according to the invention can ensure that during the next parking operation of the vehicle the target refilling level (L -目标 ) is adapted to the duration of the parking. By using thermodynamic models and predicting the travel of the vehicle, and more generally the route planning of the vehicle V, the hydrogenation occurring during the parking phase is minimized.

[0108] In one embodiment of the invention, the next refilling data is determined based on two different thermodynamic models, for example, one of the models is used if the duration of the next parking operation is less than / below a predetermined threshold, and the other model is used if the duration of the next parking operation of the vehicle is above / greater than the predetermined threshold.

[0109] As described above, one of the models may use dormant parameters, while the other thermodynamic model may, for example, use parameters that reflect the cumulative amount of vaporized hydrogen exhausted from the storage tank 10 .

[0110] Thus, in particular depending on the duration of the next parking operation of the vehicle, the next refilling data can be determined based on one or the other of the two models depending on the duration of the next parking operation.

[0111] Another thermodynamic model will now be described.

[0112] Figure 3 The S1 - S3 curve is shown, with the duration D (in hours) since the start of the parking operation being shown on the X-axis and the cumulative amount CQ (in kg) of hydrogen exhausted through the exhaust port 11 being shown on the Y-axis.

[0113] The S1-S3 curves simulate the behavior of supercooled liquid hydrogen (sLH2) with a maximum allowable working pressure (also called MAWP) of 20 bar, assuming a pressure of 6 bar at the beginning of the parking operation at D=0.

[0114] These curves were obtained at 30 Watts of heat input.

[0115] Curve S1 corresponds to a filling level L of 20% of the tank at the beginning of the parking operation (D=0). -停放 .

[0116] Curve S2 corresponds to a filling level L of 50% of the tank at the start of the parking operation (D=0). -停放 .

[0117] Curve S3 corresponds to a filling level L of 80% of the tank at the start of the parking operation (D=0). -停放 .

[0118] It can be seen, for example, that after a parking period of 45 hours, a tank that is initially 20% full (curve S1) has less cumulative exhaust hydrogen losses than a tank that is 50% full at the start of the parking operation (curve S2).

[0119] Therefore, depending on the duration of the parking, it may be more advisable to fill the tank to a lower level to reduce losses via the vent.

[0120] Other parameters may be considered.

[0121] For example, in case the next parking operation of the vehicle lasts N hours, the next refilling data is determined by taking into account this parking duration of the vehicle.

[0122] The next refill data also takes into account the consumption of liquid hydrogen during the vehicle's journey between the time the next refill data is provided and the time the vehicle arrives at the liquid hydrogen refueling station.

[0123] The next refill data also takes into account the likely journey the vehicle will need to make between a refueling station and where the vehicle will be parked, such as a parking lot or garage.

[0124] The next refilling data is also determined based on vehicle trip data and / or data related to the vehicle surroundings (eg external temperature).

[0125] Reference now Figure 4 The different steps of a method according to one embodiment of the invention are described.

[0126] The method begins at the beginning of a daily usage cycle of the vehicle V (step 200 ).

[0127] At the beginning of the daily cycle, the lower limit (L -最小 ) and upper limit (L -最大)(step 201); These limits are recommended for the end of the day, ie just before the parking operation begins. This is an initialization.

[0128] When the vehicle V is traveling during the day, the system 100 checks the current filling level (L ) of the tank 10 in real time or at regular time intervals. -实际 ) is less than the lower limit (L -最小 ), namely L -实际 whether <L -最小 (Step 202).

[0129] As long as the current filling level L -实际 Did not drop to the lower limit L -最小 Next, monitoring is performed (step 203) to determine whether the next parking operation starts.

[0130] As long as the parking operation has not yet started, step 202 is repeated.

[0131] If the current filling level L -实际 Drop to the lower limit L -最小 Thereafter, it is concluded that the next refilling of the tank 10 is necessary.

[0132] At this time, in step 204, the parking start filling level L is calculated. -停放 .

[0133] Next, in step 205, the parking start filling level L is determined. -停放 Is it less than the upper limit L? - maximum.

[0134] If L -停放 Less than L -最大 , then the value of L is 100% -目标 (Step 206).

[0135] The next step is a step 206 of filling the tank to 100% of the liquid level. In other words, the liquid level L -目标 is set to 100%.

[0136] If it is determined in step 205 that L -停放 Greater than L -最大 , then execute step 208, which includes calculating the target filling level L to be reached for the next refilling. -目标 .

[0137] Once this step 208 has been performed, the tank is refilled in step 207 .

[0138] In step 203, if the time for the parking operation to start is reached, step 210 is executed, in which the current filling level L -实际and the lower limit L -最小 Compare between.

[0139] If the current filling level L -实际 (which basically corresponds to L -停放 ) is greater than the lower limit L -最小 , then the parking operation can effectively start in step 211.

[0140] However, if the current filling level L -实际 Less than the filling lower limit L -最小 , then a signal is issued to refill the tank 10 to the target filling level L -目标 (step 212).

[0141] If this is not necessary, the tank can be filled to a level different from L. -目标 , for example in order to avoid a refilling operation before the parking phase.

[0142] The purpose of the steps described is to maximize the sleep parameters.

Claims

1. A method for reducing hydrogenation losses in a liquid hydrogen tank (10), the tank being refillable and mounted on a vehicle (V) in order to supply, for example, a fuel cell of the vehicle, the tank (10) being provided with an exhaust port for discharging gaseous hydrogen outside the tank in the event of overpressure, the method comprising the following steps: - providing next refilling data for the next refilling of the liquid hydrogen tank according to the next parking operation planned for the vehicle after the next refilling, the next refilling data providing at least a target filling level (L) to be reached for the next refilling of the tank -目标 ), the target filling level (L -目标 ) is determined in such a way that: when the vehicle is refilled to the target filling level (L -目标 ) and the start of the parking operation, at the start of the parking operation of the vehicle, the tank has a parking start filling level (L -停放 ), the parking starts filling level (L -停放 ) is designed so that the loss of hydrogen via said exhaust port of the tank is minimized during the duration of this next parking operation of the vehicle.

2. The method according to claim 1, wherein: The next refilling data are determined at least as a function of a dormancy parameter (DORM) which represents a waiting time before venting the tank due to a pressure increase in the tank when hydrogen is gasified.

3. The method according to claim 2, wherein: The determination of the next refilling data uses a thermodynamic model, which provides the dormant parameters and the parking start filling level (L -停放 ) and may also be associated with the pressure within the tank.

4. The method according to claim 3, wherein: The thermodynamic model is in the form of a correspondence table, which converts the tank filling percentage or the parking start filling level (L -停放 ) is associated with the value of the dormancy parameter and possibly the pressure in the tank.

5. A method according to any one of the preceding claims, wherein: The next refilling data is determined based on two different thermodynamic models, for example, one of the models is used if the duration of the next parking operation of the vehicle is less than a predetermined threshold, and the other of the two models is used if the duration of the next parking operation of the vehicle is greater than the predetermined threshold.

6. A method according to any one of the preceding claims, wherein: The next refill data also takes into account the consumption of liquid hydrogen during the vehicle's journey between the time the next refill data is provided and the time the vehicle arrives at a liquid hydrogen refueling station.

7. A method according to any one of the preceding claims, wherein: The next refill data is also determined based on data relating to the travel history of the vehicle.

8. A method according to any one of the preceding claims, wherein: The next refilling data is also determined based on data input by the user via the human-machine interface, which input data relates to, for example, a trip that the user plans to make, in particular a trip just before the next refilling and a trip just after the next refilling.

9. A system (100) for reducing hydrogen gasification losses in a liquid hydrogen storage tank (10), the tank (10) being refillable and mounted on a vehicle to feed, for example, a fuel cell of the vehicle, the tank being provided with an exhaust port for discharging gaseous hydrogen out of the tank in the event of overpressure, the system (100) being configured as follows: - providing next refilling data for the next refilling of the liquid hydrogen tank according to the next parking operation planned for the vehicle after the next refilling, the next refilling data providing at least a target filling level (L) to be reached for the next refilling of the tank -目标 ), the target filling level (L -目标 ) is determined in such a way that: when the vehicle is refilled to the target filling level (L -目标 ) and the start of the parking operation, at the start of the parking operation of the vehicle (V), the tank has a parking start filling level (L -停放 ), the parking starts filling level (L -停放 ) is designed so that the loss of hydrogen via said exhaust port of the tank is minimized during the duration of this next parking operation of the vehicle.

10. The system (100) according to claim 9, wherein: The system comprises a data processing unit (101), in particular a computer, configured to: receive data on the duration of the next parking operation of the vehicle; and determining a target filling level (L ) of the tank for said next refilling at least as a function of the duration of said next parking operation of the vehicle. -目标 ) related data.

11. The system (100) according to claim 10, wherein: The data processing unit (101) is configured to: receive travel data of the vehicle (V) and / or data related to the surrounding environment of the vehicle, such as the external temperature; and determine a target filling level (L) of the tank for the next refilling. -目标 ) when using the trip data and / or the data related to the surrounding environment of the vehicle.

12. The system (100) according to any one of claims 9 to 11, wherein: The system is configured to perform at least some of the following steps: - Processing data from sensors (111), such as meters measuring the level of liquid hydrogen in a tank; - Processing of driving cycle related data; - retrieve the trip history of a vehicle (V); -Communicate with the liquid hydrogen refueling network database and GPS; - calculation of next refilling data, which in particular comprises the next refuelling location, the timetable and the target filling level (L -目标 ) - Displaying the next refill data to the user via the human-machine interface (105).

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