Method for reducing hydrogen evaporation losses

Abstract

To provide a method for reducing the hydrogen boil-off loss in a liquid hydrogen tank.SOLUTION: The liquid hydrogen tank is refillable and installed on board a vehicle (V), and is provided with a vent for discharging gaseous dihydrogen out of the liquid hydrogen tank in the event of overpressure. The method comprises the step of providing data on a next refill of the liquid hydrogen tank as a function of a next parking operation of the vehicle planned after the next refill. The data on the next refill provides at least a target fill level to be reached for the next refill. The target fill level is determined such that, at the start of the parking operation of the vehicle after a possible movement of the vehicle between the refill to the target fill level and the start of the parking operation, the liquid hydrogen tank has a start-of-parking fill level designed to minimize the loss of dihydrogen through the vent for the duration of the next parking operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] [1] The present invention relates to a method for reducing hydrogen evaporative loss in a liquid hydrogen tank, the tank being refillable and installed on-board a vehicle. [Background technology]

[0002] [2] Cryogenic storage of hydrogen on board vehicles (cars, trucks, ships, trains, planes, etc.) provides an increase in the range of travel made by the vehicle. One major drawback associated with this storage method is the evaporation of hydrogen (a phenomenon called "boil-off"), which is caused by the transfer of heat between the outside and the stored hydrogen at temperatures between 20 and 150 Kelvin. Evaporation leads to losses through the exhaust, which increases the carbon footprint and operating costs. There is a great need to reduce these losses.

[0003] [3] The present invention is specifically aimed at overcoming this problem. Summary of the Invention

[0004] [4] The invention therefore relates to a method for reducing hydrogen evaporative losses in a liquid hydrogen tank, the liquid hydrogen tank being refillable and installed, for example, on-board a vehicle (land, sea, air, space) to supply a fuel cell of the vehicle, the liquid hydrogen tank being provided with a vent for venting gaseous dihydrogen from the liquid hydrogen tank in case of overpressure, the method comprising: providing data relating to a next refill of the liquid hydrogen tank in response to a next parking maneuver of the vehicle planned after the next refill, the data relating to the next refill providing at least a target filling level (L-targ) to be reached for the next refill of the liquid hydrogen tank, the target filling level (L-targ) being determined such that at the start of a parking maneuver of the vehicle after a possible movement of the vehicle between refilling to the target filling level (L-targ) and the start of the parking maneuver, the liquid hydrogen tank has a start-of-parking filling level (L-park) designed such that loss of dihydrogen through an outlet of the liquid hydrogen tank is minimized over the duration of the next parking maneuver of the vehicle.

[0005] [5] The present invention advantageously enables the driver / pilot of a vehicle equipped with a cryogenic liquid hydrogen tank to use data regarding the next refill of the tank to guide the driver / pilot of the vehicle to optimize the refill strategy and minimize evaporation losses. The present invention is particularly advantageous for intensive use applications, such as trucks used all day, alternating between driving and parking phases.

[0006] [6] During the parking phase of the vehicle, when hydrogen evaporation may occur, it is important to have the tank in a condition that minimizes losses through the exhaust. This is made possible by the present invention.

[0007] [7] In the present invention, during a parking phase (i.e. the vehicle is stopped with the engine switched off), the liquid hydrogen tank stops supplying to the fuel cell. A 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 tank with hydrogen. When parked within the meaning of the present invention, the fuel cell is put into a rest state.

[0008] [8] According to one of the aspects of the invention, the duration of parking is at least 1 or 2 hours, or indeed longer, for example at least 5 or 8 hours.

[0009] [9] Note that when the vehicle is driving, the withdrawal of hydrogen by the battery reduces the pressure in the tank. Moreover, thermodynamic bedding (the development of a thermal gradient across the height of the tank) increases the pressure more in a stationary tank than in a moving tank. Therefore, the "boil-off" phenomenon is less significant when driving.

[0010]

[10] The object of the invention is to determine a target filling level (L-targ) to be reached for the next refilling of the tank, so that at the start of the parking operation the tank is filled up to the parking start filling level (L-park). In practice, the user / driver does not necessarily need to know the value of the parking start filling level (L-park). The user / driver needs to know the target filling level (L-targ) to be reached for the next refilling of the tank, since he will know this target filling level (L-targ) to refill the tank. The user / driver can, for example, enter the level value (L-targ) at a filling station, which automatically refills the tank to this level (L-targ). This level (L-targ) can also be reached manually by the user. As a variant, if the refilling is performed fully automatically, the user / driver does not need to know the target filling level (L-targ) to be reached, and the filling station receives this data and automatically performs the refilling operation.

[0011]

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

[0012]

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

[0013]

[13] According to one of the aspects of the invention, the target fill level (L-targ) provided by the data regarding the next refill is correlated to the moment (date / time) planned for the next refill.

[0014]

[14] According to one aspect of the invention, the data regarding the next refill is determined at least in response to a duration of a next parking maneuver of the vehicle.

[0015]

[15] According to one of the aspects of the invention, the duration of parking is at least 1 or 2 hours, or actually longer, for example at least 5 or 8 hours.

[0016]

[16] According to one of the aspects of the invention, the data regarding the next refill is determined in response at least to a hibernation parameter representing a waiting time before the liquid hydrogen tank is vented (through a vent) due to the increasing pressure in the liquid hydrogen tank as the hydrogen evaporates.

[0017]

[17] For a given situation, the higher the value of this sleep parameter, the longer the release of evaporated hydrogen from the tank is delayed, which is advantageous as it helps reduce evaporative losses.

[0018]

[18] According to one of the aspects of the invention, the determination of the data for the next refill uses a thermodynamic model that provides a relationship between the park parameters and the start-of-park fill level (L-park), possibly also related to the pressure inside the liquid hydrogen tank.

[0019]

[19] According to one aspect of the invention, the thermodynamic model is in the form of a correspondence table relating the tank fill rate (or the start of parking fill level (L-park)) to values ​​of the sleep parameters and possibly also to the pressure inside the liquid hydrogen tank.

[0020]

[20] By providing data regarding the next refill in order to refill the tank at the refilling station, the method according to the invention makes it possible to ensure that during the next parking maneuver of the vehicle, the target filling level of the tank (L-targ) is adapted to the duration of parking. The evaporation of hydrogen that occurs during this parking phase is minimized by using a thermodynamic model and by predicting the movements of the vehicle and, more generally, the route planning of the vehicle.

[0021]

[21] According to one aspect of the invention, data regarding the next refill is determined according to two different thermodynamic models, for example using one of the thermodynamic models if the duration of the next parking maneuver is below a predetermined threshold, and using the other model if the duration of the next parking maneuver of the vehicle exceeds a predetermined threshold.

[0022]

[22] As explained above, one of the models may use dormant parameters, and the other thermodynamic model may use parameters that reflect, for example, the accumulation of evaporated hydrogen vented from the tank.

[0023]

[23] Thus, depending in particular on the duration of the next parking maneuver of the vehicle, data regarding the next refill may be determined based on one or the other of the models, depending on the duration of the next parking maneuver.

[0024]

[24] For example, the hibernation parameter is maximized to a value of 50% when liquid hydrogen is stored in a tank at a pressure of 10 bar.

[0025]

[25] For example, the thermodynamic model uses parameters that reflect the accumulation of evaporated hydrogen vented from the tank.

[0026]

[26] According to one of the aspects of the invention, if the next parking operation of the vehicle lasts for N hours, the data regarding the next refill is determined by taking into account this duration of the parking of the vehicle.

[0027]

[27] According to one of the aspects of the invention, the data regarding the next refill also takes into account the consumption of liquid hydrogen during the movement of the vehicle between the moment the data regarding the next refill is provided and the moment the vehicle arrives at the liquid hydrogen refilling station.

[0028]

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

[0029]

[29] According to one of the aspects of the invention, the data regarding the next refill is also determined depending on the vehicle movement data and / or data relating to the vehicle's surrounding environment, such as the outside temperature.

[0030]

[30] According to one of the aspects of the invention, data regarding the next refill is also determined depending on data related to the movement history of the vehicle.

[0031]

[31] According to one aspect of the invention, the vehicle travel data is, for example, the average distance traveled by the vehicle during a typical day of travel.

[0032]

[32] According to one of the aspects of the invention, the movement data also includes the typical time that the vehicle is parked, for example, when the work day ends, such as 7:00 pm.

[0033]

[33] The duration of parking may be set to, for example, 8 or 12 hours when the vehicle is parked overnight.

[0034]

[34] According to one of the aspects of the invention, the data regarding the next refill is determined in response to data entered by the user via the human-machine interface, the entered data relating, for example, to the trips the user plans to make, in particular the trips immediately before and after the next refill.

[0035]

[35] The present invention also relates to a system for reducing hydrogen boil-off in a liquid hydrogen tank, the liquid hydrogen tank being refillable and installed, for example, on board a vehicle (land, sea, air, space) to supply a fuel cell of the vehicle, the liquid hydrogen tank being provided with a vent for venting gaseous dihydrogen from the liquid hydrogen tank in case of overpressure, the system comprising: a system configured to provide data regarding a next refill of the liquid hydrogen tank in response to a next parking operation of the vehicle planned after the next refill, the data regarding the next refill providing at least a target filling level (L-targ) to be reached for the next refill of the liquid hydrogen tank, the target filling level (L-targ) being determined such that at the start of a parking operation of the vehicle after a possible movement of the vehicle between refilling to the target filling level (L-targ) and the start of the parking operation, the liquid hydrogen tank has a start-of-parking filling level (L-park) designed such that loss of dihydrogen through the vent of the liquid hydrogen tank is minimized over the duration of the next parking operation of the vehicle.

[0036]

[36] According to one of the aspects of the invention, the system comprises a data processing unit, in particular a computer, configured to receive data relating to the duration of a next parking maneuver of the vehicle and to determine data relating to a target filling level (L-targ) of the liquid hydrogen tank for the next refilling depending at least on the duration of the next parking maneuver of the vehicle.

[0037]

[37] According to one of the aspects of the invention, the data processing unit is configured to receive vehicle movement data and / or data relating to the vehicle's surrounding environment, e.g. outside temperature, and to use this data when determining data relating to a target filling level (L-targ) of the liquid hydrogen tank for the next refill.

[0038]

[38] According to one of the aspects of the invention, a data processing unit is located on-board the vehicle (the vehicle's on-board computer) and may possibly communicate with a remote server.

[0039]

[39] A data processing unit installed on-board the vehicle is linked to software based on a remote server for more complex computational operations.

[0040]

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

[0041]

[41] In particular, the data processing unit is a remote computing unit whose memory contains typical driving cycles.

[0042]

[42] According to one of the aspects of the invention, the system comprises a human machine interface for providing the driver with information regarding the target filling level (L-targ) of the tank for the next refill.

[0043]

[43] According to one aspect of the invention, the system includes: - processing data from a sensor, such as a gauge measuring the level of liquid hydrogen in a liquid hydrogen tank; - processing data related to a driving cycle; - searching the movement history of a vehicle; - communicating with a liquid hydrogen refilling network database and a GPS; - calculating data relating to the next refill, including in particular information regarding the location of the next refill, the timetable and the target filling level (L-targ) of the liquid hydrogen tank, displaying data regarding the next refill to the user via a human machine interface; The method is configured to complete at least some of the steps.

[0044]

[44] According to one of the aspects of the invention, at least one pressure sensor and / or one level sensor is arranged in the liquid hydrogen tank.

[0045]

[45] Further characteristics, details and advantages of the present invention will become more clearly apparent from reading the following description, with reference to the attached schematic drawings, and from some illustrative embodiments given by way of non-limiting indication. [Brief description of the drawings]

[0046] [Figure 1]

[46] Figure 1 is a schematic diagram of a system for reducing hydrogen loss according to the present invention. [Diagram 2]

[47] Figure 2 shows the dormancy curve used by the system of Figure 1. [Diagram 3]

[48] ​​Figure 3 shows the curve of the amount of hydrogen pumped out. [Figure 4]

[49] Figure 4 is a block diagram illustrating a method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047]

[50] The features, variants, and different embodiments of the invention can be associated with each other in various combinations, provided they are not mutually incompatible or mutually exclusive. In particular, it is possible to envisage variants of the invention that comprise only a selection of features described below in isolation from other described features, provided that the selection of features is sufficient to give the invention a technical advantage over the prior art and / or to distinguish the invention from the prior art.

[0048]

[51] Figure 1 shows a system 100 for reducing hydrogen evaporative loss (or "boil-off") in a liquid hydrogen tank 10 that is refillable and installed on-board a road vehicle V, in this case a truck, to supply a fuel cell (not shown here) of the vehicle V.

[0049]

[52] The tank 10 is provided with a vent 11 for venting gaseous dihydrogen from the tank 10 in the event of overpressure.

[0050]

[53] The system 100 is configured to provide data regarding the next refill of the liquid hydrogen tank 10 in response to a next parking maneuver of the vehicle planned after the next refill, the data regarding the next refill providing at least a target filling level (L-targ) to be reached for the next refill of the liquid hydrogen tank 10, the target filling level (L-targ) being determined such that at the start of the parking maneuver of the vehicle after a possible movement of the vehicle V between the refill to the target filling level (L-targ) and the start of the parking maneuver, the liquid hydrogen tank 10 has a start-of-parking filling level (L-park) designed such that the loss of dihydrogen through the vent of the liquid hydrogen tank 10 is minimized over the duration D of the next parking maneuver of the vehicle. These aspects are described in more detail below.

[0051]

[54] The system 100 is receiving data relating to the duration of a next parking maneuver of the vehicle and determining data relating to a target filling level (L-targ) of the liquid hydrogen tank 10 for the next refilling as a function of at least the duration of the next parking maneuver of the vehicle; and / or receiving vehicle movement data and / or data relating to the vehicle's surrounding environment, e.g., outside temperature, and using this data when determining data relating to a target filling level (L-targ) of the liquid hydrogen tank for the next refill; The method comprises the steps of:

[0052]

[55] The data processing unit 101 is located on board the vehicle V and is capable of communicating with a remote server 120, also called the cloud.

[0053]

[56] A data processing unit 101 installed on board the vehicle V is linked to a computer 130 on a remote server 120 for more complex computational operations.

[0054]

[57] The remote server 120 includes in memory 135 data regarding driving and / or refill cycle history.

[0055]

[58] Data concerning the next refill is therefore determined by taking into account data relating to the movement history of vehicle V, if applicable.

[0056]

[59] The travel data for a vehicle V may be, for example, the average distance traveled by the vehicle during a typical day of travel.

[0057]

[60] The movement data may also comprise the usual time that a vehicle is parked, for example when the working day ends, such as 6pm or 7pm.

[0058]

[61] The parking duration may be set to 8, 10, or 12 hours, for example, when the vehicle is parked overnight.

[0059]

[62] Data relating to the next refill may also be determined in response to data entered by the user via the human-machine interface 105. The entered data may, for example, relate to the journeys the user plans to make, in particular the journeys immediately before and after the next refill.

[0060]

[63] A human-machine interface 105, for example a touch screen permanently installed in the vehicle V or a smartphone held by the driver C, is used to provide the driver with information regarding the target filling level of the tank for the next refill (L-targ).

[0061]

[64] The remote server 120 includes a database 137 of liquid hydrogen refilling station locations, for example in the form of a map of the network of liquid hydrogen refilling stations. This database 137 may be updated periodically.

[0062]

[65] The system 100 is - processing data from a sensor 111, such as a gauge, measuring the level of liquid hydrogen in the liquid hydrogen tank 10; - processing data related to a driving cycle; - retrieving a vehicle movement history from memory 135; - communicating with the liquid hydrogen refilling network database 137 and with a GPS; - calculating data relating to the next refill, including in particular information regarding the location of the next refill, the timetable and the target filling level (L-targ) of the liquid hydrogen tank, - displaying data regarding the next refill to the user via the human machine interface 105 The apparatus is configured to execute the following steps:

[0063]

[66] At least one pressure sensor 111 and / or one liquid hydrogen level sensor 111 are disposed in the liquid hydrogen tank 10.

[0064]

[67] The system 100 can be used to implement a method for reducing hydrogen evaporative loss through the vent 11 of the tank 10, the method comprising: The method includes a step of providing data regarding the next refill of the liquid hydrogen tank 10 in response to a next parking operation of the vehicle V planned after the next refill, the data regarding the next refill providing at least a target filling level (L-targ) to be reached for the next refill of the liquid hydrogen tank, the target filling level (L-targ) being determined such that at the start of a parking operation of the vehicle after a possible movement of the vehicle between refilling to the target filling level (L-targ) and the start of the parking operation, the liquid hydrogen tank has a parking start filling level (L-park) designed such that loss of dihydrogen through the vent of the liquid hydrogen tank is minimized over the duration of the next parking operation of the vehicle V.

[0065]

[68] The present invention advantageously enables the use of data regarding the next refill of the tank 10 to guide the driver / pilot of a vehicle equipped with a cryogenic liquid hydrogen tank to optimize the refill strategy and minimize losses through the exhaust 11. The present invention is particularly advantageous for intensive use applications, for example trucks used all day, alternating between driving and parking phases.

[0066]

[69] During the parking phase of the vehicle, when hydrogen evaporation may occur, it is important to have the tank in a condition that minimizes losses through the exhaust. This is made possible by the present invention.

[0067]

[70] In the present invention, during a parking phase (i.e. the vehicle is stopped with the engine switched off), the liquid hydrogen tank stops supplying to the fuel cell. A 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 tank with hydrogen. When parked within the meaning of the present invention, the fuel cell is put into a rest state.

[0068]

[71] According to one of the aspects of the invention, the duration of parking is at least 1 or 2 hours, or indeed longer, for example at least 5 or 8 hours.

[0069]

[72] The object of the invention is to determine a target filling level (L-targ) to be reached for the next refilling of the tank, so that at the start of the parking maneuver, the tank is filled up to the parking start filling level (L-park). In practice, the user / driver does not necessarily need to know the value of the parking start filling level (L-park). The user / driver needs to know the target filling level (L-targ) to be reached for the next refilling of the tank, since he will know this target filling level (L-targ) to refill the tank. The user / driver can, for example, enter the level value (L-targ) at a filling station, which automatically refills the tank to this level (L-targ). This level (L-targ) can also be reached manually by the user. As a variant, if the refilling is performed fully automatically, the user / driver does not need to know the target filling level (L-targ) to be reached, and the filling station receives this data and automatically performs the refilling operation.

[0070]

[73] Preferably, the target fill level (L-targ) provided by the data regarding the next refill is correlated to the moment (date / time) planned for the next refill.

[0071]

[74] Preferably, the data relating to the next refill is determined in response at least to the duration of a next parking maneuver of the vehicle.

[0072]

[75] Preferably, the duration of parking is at least 1 or 2 hours, or indeed longer, for example at least 5 or 8 hours.

[0073]

[76] In the example described, the data regarding the next refill is determined at least in response to a dormancy parameter DORM, which represents the waiting time before the liquid hydrogen tank is vented (through vent 11) due to the increasing pressure in the liquid hydrogen tank as the hydrogen evaporates.

[0074]

[77] The dormancy parameter DORM in this case uses days as the unit and the assumption that the heat input to the tank is 5 watts.

[0075]

[78] Figure 2 shows curves C1 to C4 with the tank filling level L-park (expressed as the filling percentage of tank 10) on the X-axis and the dormancy parameter DORM (expressed as days) on the Y-axis.

[0076]

[79] For a given situation, the higher the value of this dormancy parameter DORM, the longer the release of evaporated hydrogen from the tank is delayed, which is advantageous since it helps to reduce losses through the exhaust 11.

[0077]

[80] Curve C1 corresponds to a model of the variation of the dormancy parameter DORM for liquid hydrogen LH2 at a pressure between 6 and 10 bar, except for the 100% filling value, where the pressure is between 8 and 10 bar.

[0078]

[81] Curve C2 corresponds to a model of the variation of the dormancy parameter DORM for subcooled liquid hydrogen sLH2 at pressures between 6 and 20 bar, except for the 100% fill value, where the pressure is between 16 and 20 bar.

[0079]

[82] Curve C3 corresponds to the model with liquid hydrogen LH2 for pressures varying from 1 to 10 bar.

[0080]

[83] Curve C4 corresponds to the model with hydrogen sLH2 for pressures varying from 1 to 20 bar.

[0081]

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

[0082]

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

[0083]

[86] Unexpectedly, it turns out that filling the tank to 100% is not always desirable if the aim is to reduce the risk of hydrogen loss through the exhaust.

[0084]

[87] The determination of the data for the next refill is made using a thermodynamic model that provides a relationship between the park parameters and the parking start fill level (L-park), which in some cases is also related to the pressure inside the liquid hydrogen tank.

[0085]

[88] In the example described, the thermodynamic model is in the form of a correspondence table relating the tank fill level or (L-park) to values ​​of the park parameters and possibly also to the pressure inside the liquid hydrogen tank.

[0086]

[89] By providing data regarding the next refill in order to refill the tank at the refilling station, the method according to the invention makes it possible to ensure that during the next parking maneuver of the vehicle, the target filling level (L-targ) of the tank is adapted to the duration of parking. The evaporation of hydrogen that occurs during this parking phase is minimized by using a thermodynamic model and by predicting the movements of the vehicle and, more generally, the route planning of the vehicle V.

[0087]

[90] In one embodiment of the present invention, data regarding the next refill is determined according to two different thermodynamic models, for example using one of the thermodynamic models if the duration of the next parking maneuver is below a predetermined threshold, and using the other model if the duration of the next parking maneuver of the vehicle exceeds a predetermined threshold.

[0088]

[91] As explained above, one of the models may use dormant parameters and the other thermodynamic model may use parameters reflecting, for example, the accumulation of evaporated hydrogen vented from tank 10.

[0089]

[92] Thus, depending in particular on the duration of the next parking maneuver of the vehicle, data regarding the next refill may be determined based on one or the other of the models depending on the duration of the next parking maneuver.

[0090]

[93] Here, an alternative thermodynamic model is described.

[0091]

[94] Figure 3 shows curves S1-S3 having on the X-axis the duration D in hours from the start of the parking maneuver and on the Y-axis the cumulative amount CQ of hydrogen exhausted through the exhaust outlet 11, expressed in kg.

[0092]

[95] Curves S1-S3 model the behavior of subcooled liquid hydrogen (sLH2) with a maximum allowable working pressure (also called MAWP) of 20 bar, assuming a pressure of 6 bar at the start of the parking maneuver at D=0.

[0093]

[96] These curves were obtained for a heat input of 30 watts.

[0094]

[97] Curve S1 corresponds to a filling level of the tank L-park of 20% at the start of the parking maneuver (D=0).

[0095]

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

[0096]

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

[0097]

[0100] For example, it can be seen that after a 45 hour parking period, a tank that was initially 20% full (curve S1) has less cumulative vented hydrogen loss than if the tank was 50% full at the start of the parking maneuver (curve S2).

[0098]

[0101] Therefore, depending on the duration of parking, it may be more prudent to fill the tank to a lower level to reduce losses through the exhaust.

[0099]

[0102] Other parameters may be taken into consideration.

[0100]

[0103] For example, if the next parking maneuver of the vehicle will last N hours, the data for the next refill is determined by taking into account this duration of the parking of the vehicle.

[0101]

[0104] The data regarding the next refill also takes into account the consumption of liquid hydrogen during the movement of the vehicle between the moment the data regarding the next refill is provided and the moment the vehicle arrives at the liquid hydrogen refilling station.

[0102]

[0105] The data regarding the next refill also takes into account possible trips that the vehicle needs to make between the refill station and the location where the vehicle will be parked, for example a car park or garage.

[0103]

[0106] The data regarding the next refill may also be determined depending on the vehicle's movement data and / or data relating to the vehicle's surrounding environment, for example the outside temperature.

[0104]

[0107] The different steps of the method according to an embodiment of the present invention will now be described with reference to FIG.

[0105]

[0108] The method begins at the start of a daily use cycle of the vehicle V (step 200).

[0106]

[0109] At the start of this daily cycle, the lower (L-min) and upper (L-max) limits for the filling level of the tank 10 are calculated (step 201), these limits being recommended at the end of the day just before the start of the parking maneuver. This is the initialization.

[0107]

[0110] While the vehicle V is being driven during the day, the system 100 determines, in real time or at regular time intervals, whether the current filling level (L-real) of the tank 10 is below the lower limit (L-min), i.e., L-real <L-minであるかどうかをチェックする(ステップ202)。

[0108]

[0111] As long as the current filling level L-real does not fall below the lower limit L-min, monitoring is performed to determine whether a next parking maneuver is to commence (step 203).

[0109]

[0112] Step 202 is repeated unless a parking maneuver is initiated.

[0110]

[0113] When the current filling level L-real falls below the lower limit L-min, it is presumed that a next refilling of the tank 10 is necessary.

[0111]

[0114] At this point, in step 204, the parking start fill level L-park is calculated.

[0112]

[0115] Next, in step 205, it is determined whether the parking start filling level L-park is less than the upper limit L-max.

[0113]

[0116] If L-park is less than L-max, then L-targ is given a value of 100% (step 206).

[0114]

[0117] The next step is filling the tank 206, where the tank is filled to a level of 100%. In other words, the level L-targ is set to 100%.

[0115]

[0118] If, in step 205, it is determined that L-park is greater than L-max, then step 208 is performed, which involves calculating the target fill level L-targ to be reached for the next refill.

[0116]

[0119] Once this step 208 is performed, the tank is refilled in step 207.

[0117]

[0120] If, in step 203, the moment has arrived when the parking maneuver is to begin, then step 210 is carried out, in which a comparison is made between the current filling level L-real and the lower limit L-min.

[0118]

[0121] If the current filling level L-real (which therefore corresponds substantially to L-park) is greater than the lower limit L-min, a parking maneuver can effectively be started in step 211 .

[0119]

[0122] However, if the current filling level L-real is less than the lower filling limit L-min, a recommendation to refill the tank 10 to the target filling level L-targ is issued (step 212).

[0120]

[0123] If not necessary, it may be possible to park with the tank filled to a value different from L-targ, for example to avoid a refilling operation before the parking phase.

[0121]

[0124] The objective of the described steps is to maximize the dormancy parameter.

Claims

1. A method for reducing hydrogen evaporation losses in a liquid hydrogen tank (10), said liquid hydrogen tank being refillable and installed, for example, on board a vehicle (V) to supply a fuel cell of said vehicle, said liquid hydrogen tank (10) being provided with a vent for venting gaseous dihydrogen from said liquid hydrogen tank in case of overpressure, said method comprising: providing data relating to a next refill of the liquid hydrogen tank in response to a next parking maneuver of the vehicle planned after the next refill; the data relating to the next refill providing at least a target fill level (L-targ) to be reached for the next refill of the liquid hydrogen tank; The target fill level (L-targ) is determined such that at the initiation of the parking maneuver of the vehicle after possible movement of the vehicle between refilling to the target fill level (L-targ) and the initiation of the parking maneuver, the liquid hydrogen tank has a park start fill level (L-park) designed to minimize loss of dihydrogen through an outlet of the liquid hydrogen tank for the duration of the next parking maneuver of the vehicle.

2. 2. The method of claim 1, wherein the data regarding the next refill is determined in response at least to a dormant parameter (DORM) representing a waiting time before the liquid hydrogen tank is vented due to increasing pressure in the liquid hydrogen tank as hydrogen evaporates.

3. 3. The method according to claim 2, wherein the determination of data regarding the next refill uses a thermodynamic model providing a relationship between the sleep parameter and the parking start fill level (L-park), possibly also related to the internal pressure of the liquid hydrogen tank.

4. 4. The method according to claim 3, wherein the thermodynamic model is in the form of a correspondence table relating a tank fill rate or a parking start fill level (L-park) to values ​​of the sleep parameters and possibly also to the pressure inside the liquid hydrogen tank.

5. 5. The method according to claim 1, wherein the data regarding the next refill is determined according to two different thermodynamic models, for example using one of the thermodynamic models if the duration of the next parking maneuver of the vehicle is below a predetermined threshold and using the other model if the duration of the next parking maneuver of the vehicle exceeds the predetermined threshold.

6. 6. The method according to claim 1, wherein the data regarding the next refill also takes into account the consumption of liquid hydrogen during the movement of the vehicle between the moment when the data regarding the next refill is provided and the moment when the vehicle arrives at a liquid hydrogen refilling station.

7. The method according to any one of claims 1 to 6, wherein the data relating to the next refill is also determined depending on data relating to the movement history of the vehicle.

8. 8. The method according to claim 1, wherein the data relating to the next refill is determined in response to data entered by a user via a human-machine interface, the entered data for example relating to a journey that the user plans to make, in particular a journey immediately before and immediately after the next refill.

9. A system (100) for reducing hydrogen evaporation losses in a liquid hydrogen tank (10), the liquid hydrogen tank (10) being refillable and installed on board a vehicle, for example to supply a fuel cell of the vehicle, the liquid hydrogen tank being provided with a vent for venting gaseous dihydrogen from the liquid hydrogen tank in case of overpressure, the system (100) comprising: configured to provide data regarding a next refill of the liquid hydrogen tank in response to a next parking maneuver of the vehicle planned after the next refill; the data relating to the next refill providing at least a target fill level (L-targ) to be reached for the next refill of the liquid hydrogen tank; The target fill level (L-targ) is determined such that at the start of the parking maneuver of the vehicle (V) after possible movement of the vehicle between refilling to the target fill level (L-targ) and the start of the parking maneuver, the liquid hydrogen tank has a park start fill level (L-park) designed to minimize loss of dihydrogen through the vent of the liquid hydrogen tank for the duration of the next parking maneuver of the vehicle.

10. The system (100) according to claim 9, comprising a data processing unit (101), in particular a computer, configured to receive data relating to the duration of the next parking maneuver of the vehicle and to determine data relating to the target filling level (L-targ) of the liquid hydrogen tank for the next refilling in dependence at least on the duration of the next parking maneuver of the vehicle.

11. The system (100) according to claim 10, wherein the data processing unit (101) is configured to receive movement data of the vehicle (V) and / or data relating to the vehicle's surrounding environment, e.g. outside air temperature, and to use this data when determining the data relating to the target filling level (L-targ) of the liquid hydrogen tank for the next refill.

12. The system comprises: - processing data from a sensor (111), such as a gauge, measuring the level of liquid hydrogen in said liquid hydrogen tank; - processing data related to the driving cycle, - searching for the movement history of said vehicle (V); - communicating with a liquid hydrogen refilling network database and a GPS; - calculating data relating to the next refill, including in particular information regarding the next refill location, the timetable and the target filling level (L-targ) of the liquid hydrogen tank, - displaying data relating to said next refill to the user via a human machine interface (105); The system (100) according to any one of claims 9 to 11, configured to perform at least some of the following:

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