Hydrogen fueling system

Abstract

A hydrogen fueling system (1) comprising a control system (10), a hydrogen storage unit (2), a cooling system (3), a heating system (4), and a heat transfer fluid circuit interconnecting the hydrogen storage unit (2) to the cooling system (3) and the heating system (4), the hydrogen fueling system configured for receiving hydrogen from a hydrogen source at a first pressure through a hydrogen inlet (11i) and outputting hydrogen at a second pressure higher that the first pressure through a hydrogen outlet (16), the hydrogen storage unit comprising containers lodging therein a metal hydride adapted for hydrogen storage, the cooling system connected to the heat transfer fluid circuit via at least one valve (Vc1, Vc2) and the heating system connected to the heat transfer fluid circuit via at least one valve (Vh1, Vh2). The heating system (4) comprises a thermal energy storage unit (7) including a tank containing a volume of thermal liquid connected to a heating unit (8, 9), the volume of thermal liquid comprising a sensible thermal energy capacity exceeding 80% of a thermal energy required by the hydrogen storage unit to desorb and compress to the second pressure at least 80% of the hydrogen stored in a full hydrogen storage unit (2).

Description

[0001] P3024PC00

[0002] HYDROGEN FUELING SYSTEM

[0003] The present invention relates to a system and a method for refueling hydrogen vehicles using a metal hydrides hydrogen compression system coupled with a thermal management system.

[0004] Hydrogen is a key element of the decarbonization of mobility and industrial processes. Several serial vehicles including trucks, buses and passenger cars running on hydrogen have now been commercialized. However, one bottleneck for the widespread use of hydrogen as a fuel is the development of an effective, safe and affordable infrastructure, including production, storage, compression and distribution units.

[0005] Metal hydrides are known for their ability to store and compress hydrogen. Storage densities of up to 150 kgH2 / m3 are reachable. Further, metal hydrides can be used for the compression of hydrogen using thermal energy. Molecular hydrogen is dissociated at the surface before absorption. Two H atoms then recombine to H2 upon desorption. The thermodynamic aspects of hydride formation from gaseous hydrogen are described by pressure - composition isotherms as illustrated in Figure 1 which shows typical absorption and desorption isotherms of H2 in metal hydrides. The hydrogen absorption reaction in the material is typically exothermic (producing heat) whereas the hydrogen desorption reaction is conversely endothermic (absorbing heat). The low pressure and thermodynamics of metal hydride systems increase the level of safety of the system: in case of a container failure, the hydrogen will be released in a restricted manner, the process being thermally limited by the endothermic desorption reaction.

[0006] Metal hydride storage and compression systems are thus safe, reliable and compact in comparison to compressed gas or liquefied H2 storage systems. Further, they require minimal maintenance and have a long lifetime. Such systems can be used to absorb hydrogen directly from an electrolyzer or a low-pressure hydrogen source such as a pipeline, a low-pressure storage system, a source of hydrogen such as a chemical process or a steam reformer. The hydrogen is then stored in the metal hydrides storage-compression unit. Upon demand, the system is heated up and can desorb hydrogen at the required flow rate and pressure by controlling the rate of heat supply.

[0007] The hydrogen desorption from metal hydrides is characterized as an endothermic reaction. As such, substantial amounts of heat must be provided to enable the desorption of hydrogen. P3024PC00

[0008] Further, the amount of hydrogen desorbed is approximately linearly correlated with the amount of heat provided. Therefore, desorbing large amounts of hydrogen within a short period of time requires the supply of large quantities of heat. As an approximation, the desorption of 1 kg of hydrogen from a metal hydrides system requires between 2.5 and 4.0 kWh of thermal energy to offset the heat absorbed by the endothermic reaction. In addition, the sensible heat required to reach the desired level of temperature (and corresponding level of pressure) must be provided as well. In typical application, the amount of sensible heat required amounts to 2.0 to 6.0 kWh per kg of hydrogen to be compressed, depending on the pressure ratio to be reached, the design of the system and various other parameters.

[0009] In conventional hydrogen storage systems using metal hydrides, the relatively slow desorption is a major limitation for the implementation of a metal hydrides hydrogen storagecompression system for direct vehicle refueling where the time required to refuel the vehicle with a given amount of hydrogen is an important consideration. Typically, refueling stations seek to complete refueling within minutes, whereby refueling times in excess of 20 minutes are generally considered unacceptable.

[0010] In view of the foregoing, it is an object of this invention to provide a hydrogen fueling system enabling the fast and safe supply of hydrogen to vehicles at elevated pressures. As vehicles are included passenger cars, heavy-duty vehicles such as trucks and busses, but also other type of vehicles such as drones, planes, ships, heavy-duty construction engines, or any pressurized vessels that requires to be filled with hydrogen at an elevated pressure in a short amount of time.

[0011] It is advantageous to provide a hydrogen fueling system that can be installed in various locations with limited facilities such as limited electrical power supply and no additional utilities such as cooling water, heat sources such as steam, or compressed air.

[0012] It is advantageous to provide a hydrogen fueling system that operates with minimal noise emission and vibration, particularly when installed in urban surroundings.

[0013] It is advantageous to provide a hydrogen fueling system that can be installed with minimal site preparation and that is compact.

[0014] It is advantageous to provide a hydrogen fueling system that is cost effective and energy efficient. P3024PC00

[0015] It is advantageous to provide a hydrogen fueling system that compactly stores hydrogen at low pressure (< 30 bar) and ambient temperature.

[0016] It is advantageous to provide a hydrogen fueling system that pressurizes and dispenses hydrogen in a controlled way.

[0017] It is advantageous to provide a hydrogen fueling system that is reliable, requires minimal maintenance, and is easy to use.

[0018] It is advantageous to provide a hydrogen fueling system that is economical to produce and operate.

[0019] Objects of the invention have been achieved by providing a hydrogen fueling system according to claim 1.

[0020] Dependent claims set out various advantageous features of embodiments of the invention.

[0021] Disclosed herein is a hydrogen fueling system comprising a control system, a hydrogen storage unit, a cooling system, a heating system, and a heat transfer fluid circuit interconnecting the hydrogen storage unit to the cooling system and the heating system. The hydrogen fueling system is configured for receiving hydrogen from a hydrogen source at a first pressure through a hydrogen inlet and outputting hydrogen at a second pressure higher that the first pressure through a hydrogen outlet. The hydrogen storage unit comprises one or a plurality of containers lodging therein a metal hydride adapted for hydrogen storage, the cooling system connected to the heat transfer fluid circuit via at least one valve and the heating system connected to the heat transfer fluid circuit via at least one valve.

[0022] According to an aspect of the invention, the heating system comprises a thermal energy storage unit including a tank containing a volume of thermal liquid connected to a heating unit, the volume of thermal liquid comprising a sensible thermal energy capacity exceeding 80% of a thermal energy required by the hydrogen storage unit to desorb and compress to the second pressure at least 80% of the hydrogen stored in a full hydrogen storage unit.

[0023] In an advantageous embodiment, the sensible thermal energy capacity exceeds 90% of the thermal energy required by the hydrogen storage unit to desorb and compress at least 80% of P3024PC00 the hydrogen stored in a full hydrogen storage unit.

[0024] In a preferred embodiment, the sensible thermal energy capacity reaches or exceeds 100% of the thermal energy required by the hydrogen storage unit to desorb and compress preferably at least 90%, more preferably 100% of the hydrogen stored in a full hydrogen storage unit.

[0025] In an advantageous embodiment, the heating system includes an active heating unit comprising an electrical heater.

[0026] In an advantageous embodiment, the heating system comprises at least one heat exchanger.

[0027] In an advantageous embodiment, the cooling system includes an active cooling machine the active cooling machine including a hydrogen inlet connected to a hydrogen outlet of the hydrogen storage unit and a hydrogen outlet connected to the hydrogen system outlet to fueling station.

[0028] In an advantageous embodiment, the cooling system further comprises a passive cooler, for instance an air cooler.

[0029] In an advantageous embodiment, the passive cooler is connected to the heat transfer fluid circuit via a cooling circuit valve.

[0030] In an advantageous embodiment, the active cooling machine is connected to the transfer fluid circuit via a cooling circuit valve.

[0031] In an advantageous embodiment, the thermal energy storage unit comprises a thermal fluid storage tank.

[0032] In an advantageous embodiment, the thermal energy storage unit comprises a phase change media tank.

[0033] In an advantageous embodiment, the heating units are connected to the thermal energy storage unit via a heat transfer fluid circuit portion comprising one way to valves and a heat circuit pump.

[0034] In an advantageous embodiment, the heating system is connected to the heat transfer fluid P3024PC00 circuit via at least two heating circuit valves at an inlet and outlet respectively of the heating system.

[0035] In an advantageous embodiment, the hydrogen unit comprises a heat transfer fluid inlet and heat transfer fluid outlet connected to the heat transfer fluid circuit including a heat transfer fluid pump to circulate thermal fluid through the hydrogen storage unit container, the transfer fluid flowing around the metal hydride containers during a cooling or heating process.

[0036] In an advantageous embodiment, the cooling system is connected via a heat exchanger to the heating system.

[0037] In an advantageous embodiment, the thermal liquid comprises of consists of a thermal oil, for instance any one or more of a synthetic aromatic hydrocarbon mixture, benzyltoluene, dibenzyltoluene.

[0038] Also disclosed herein is a method of operating a hydrogen fueling system according to any of the above embodiments, comprising the following steps as a function of the mode of operation:

[0039] - a hydrogen storage mode in which hydrogen at said first pressure is input into the metal hydride containers of the hydrogen storage unit during which the hydrogen inlet valve is opened, the hydrogen outlet valve is closed, at least one cooling circuit valve is opened, and a heat transfer fluid pump is on to cool the hydrogen storage unit with thermal fluid flowing through the cooling system;

[0040] - a mode of desorption and compression for fueling a vehicle in which the hydrogen inlet valve is closed, the hydrogen outlet valve is opened, and the heating system is connected to the hydrogen storage unit for heating up the metal hydrides in the containers of the hydrogen storage unit, the heating circuit valves being opened for fluid from the thermal energy storage unit to flow through the hydrogen storage unit.

[0041] In an advantageous embodiment, in a hydrogen storage state or during the hydrogen absorption state, the thermal energy storage unit is connected to the heating unit and the heating circuit pump is on, configured to heat the thermal fluid or phase change media in the thermal energy storage unit.

[0042] Further advantageous features of the invention will be apparent from the following detailed description of embodiments of the invention and the accompanying illustrations. P3024PC00

[0043] Brief description of the figures

[0044] Figure l is a plot of a representative compression cycle using metal hydrides materials;

[0045] Figure 2 is a schematic block diagram of a hydrogen fueling system according to an embodiment of this invention;

[0046] Figure 3 is a plot of metal hydride hydrogen content and temperature evolution of a hydrogen fueling system according to an embodiment of the invention when going through a full storage-compression cycle;

[0047] Figures 4 to 8 are schematic block diagrams of the hydrogen fueling system according to the embodiment of figure 2 illustrating different operation states in which valves and pumps are switched according to the operation state, whereby:

[0048] - Figure 4 illustrates an operation state of an absorption mode;

[0049] - Figure 5 illustrates an operation state of storage mode;

[0050] - Figure 6 illustrates an operation state of compression (heatup+desorption) mode;

[0051] - Figure 7 illustrates an operation state of a cooldown of metal hydride to ambient temperature through an air cooler mode;

[0052] - Figure 8 illustrates an operation state of a cooldown of metal hydride to the absorption temperature through a cooling machine mode;

[0053] Figure 9 is a plot of the thermal storage temperature and output heating power of a hydrogen fueling system according to an embodiment of the invention during the desorption process;

[0054] Figures 10a and 10b shows two examples of thermal energy storage solutions that may be implemented in a hydrogen fueling system according to embodiments of the invention, the first one is based on storing a certain volume of thermal fluid at high temperature and the second one is based on phase change material storing heat by alternating between the solid and the liquid phase.

[0055] Figure 1 illustrates a typical compression cycle using metal hydrides material which shows for instance that hydrogen is absorbed at a low pressure (e.g., < 35 bar) directly from a hydrogen source and can then be stored as long as necessary in a safe manner. Upon demand P3024PC00 for hydrogen, the metal hydrides of the system are heated up to reach the required pressure and hydrogen for desorption and supply to the user.

[0056] A refueling cycle is illustrated in figure 3. During absorption the metal hydride stack is cooled down while the absorption process produces heat: the temperature is therefore constant and the hydrogen content increases, in this example by 28 kg, during the absorption time. During storage the hydrogen content stays constant and the temperature may increase depending on the storage time and the insulation type. Then, the stack is heated up and hydrogen desorption to the tank is started. This process can be very fast, therefore fulfilling the fast filling requirement time, thanks to the thermal storage providing very high amount of heating power. The hydrogen pressure may be increased in a controlled manner using for instance a PID control. The hydrogen content therefore decreases and the temperature increases. Finally, during cooldown, the temperature decreases in preparation for the next absorption process.

[0057] Referring to figure 2, a hydrogen fueling system according to embodiments of the invention is illustrated. The hydrogen fueling system 1 receives hydrogen at a relatively low first pressure, which could be in a range of 1 to 50 bars, for instance in a range of 30 to 40 bars, from a hydrogen source such as an electrolyser, and outputs hydrogen at a relatively high second pressure on demand, for instance up to 380 bars, for the refueling of a vehicle. Between the low pressure input and the high pressure output, the hydrogen fueling system stores hydrogen in a safe manner using metal hydrides.

[0058] The hydrogen fueling system 1 according to embodiments of the invention comprises a hydrogen storage unit 2, a cooling system 3, and a heating system 4.

[0059] The hydrogen storage unit 2 comprises one or more containers, typically a plurality of containers in which one or more metal hydrides are contained. The hydrogen storage unit comprises a per se known design, for instance as described in the WO2023 / 025657. Other per se known metal hydride container configurations may be used within the scope of this invention.

[0060] The hydrogen storage unit 2 comprises a hydrogen inlet 1 li coupled to a hydrogen source via a hydrogen inlet valve Vi and a hydrogen outlet 1 lo that is connected to the hydrogen system outlet 16 for fueling a vehicle via a hydrogen outlet valve Vo. The hydrogen outlet 1 lo passes through the cooling system 3 before exiting the hydrogen system outlet 16 to fueling station. The hydrogen storage unit further comprises a heat transfer fluid inlet 12i and a heat transfer P3024PC00 fluid outlet 12o connected to a heat transfer fluid circuit connected to the cooling system 3 and the heating system 4 via various valves that are operated to switch between open and closed states depending on the mode of operation of the hydrogen fueling system 1.

[0061] Pumps including a heat transfer fluid pump Pl and a heating circuit pump P2 may be provided to pump thermal fluid in the heat transfer circuit, the operation of the pumps also depending on the mode of operation of the hydrogen fueling system 1.

[0062] The cooling system 3 comprises an active cooling machine 5 having a hydrogen inlet 14i connected to the hydrogen outlet l lo of the hydrogen storage unit 2, and a hydrogen outlet 14o connected to the hydrogen system outlet 16 to fueling station via the hydrogen outlet valve Vo.

[0063] The active cooling machine 5 may for instance comprise a liquid-liquid or liquid-air cooling system according to conventional designs per se well known in the art of refrigeration and cooling systems. The active cooling machine 5 may for instance comprise the cooling side of an active heat pump whereby the heating side of the heat pump may provide complementary energy supplied to the heating system 4, for instance via a heat exchanger 9 of the heating system 4.

[0064] The cooling system 3 may optionally further comprise a passive cooler 6, for instance an air cooler, optionally comprising a ventilator, such passive coolers also being per se well known in the art of passive cooling systems.

[0065] The active cooling machine 5 is coupled to the heat transfer fluid circuit via a first cooling circuit valve Vcl and the passive cooler 6 may also be connected to the heat transfer fluid circuit via a second cooling circuit valve Vc2.

[0066] The heating system 4 comprises a thermal energy storage unit 7 connected to the heat transfer fluid circuit via heating circuit valves Vhl, Vh2, and an active heating unit 8 connected to the thermal energy storage unit 7 via a heat transfer fluid circuit portion connected to the thermal energy storage unit via one-way valves Vh3, Vh4.

[0067] The heating system 4 may further comprise a heat exchanger 9 as previously mentioned, coupled for instance to the cooling system for receiving heat output by the cooling system 3. The heat exchanger 9 may be coupled to other heat sources or additional heat exchangers may P3024PC00 be provided coupled to other heat sources available in the environment in which the hydrogen fueling system is installed. A heat circuit pump P2 is provided to transfer fluid from the active heating unit 8 to the thermal energy storage unit 7 whereby during heating output of the thermal energy storage unit 7 the heating circuit between the thermal energy storage unit 7 and active heating unit 8 forms a closed circuit.

[0068] The hydrogen fueling system 1 further comprises a control system 10 connected to the heat transfer fluid pump Pl and heating circuit pump P2 as well as to the various cooling circuit valves Vcl, Vc2 and heating circuit valves Vhl, Vh2, Vh3, Vh4 controlling the operation state of the hydrogen fueling system 1. The control system is further connected to the hydrogen inlet and outlet valves Vi, Vo to control the flow of hydrogen into and out of the hydrogen fueling system 1. The hydrogen fueling system 1 further comprises a plurality of sensors including temperature sensors BT and pressure sensors BP connected to the control system 10. The pressure sensors BP are configured to measure the pressure of hydrogen at various positions in the hydrogen circuit including at the inlet and outlet of the system. The temperature sensors BT are configured for measuring temperatures in the heat transfer fluid circuit at various positions, and for measuring temperatures of the hydrogen circuit at various positions between the inlet and outlet. Control of fluid flows and the state of operation of the machine relies on the measurement data from the pressure, temperature, and flow rate sensors.

[0069] The thermal energy storage unit 7 includes, in a first embodiment as schematically illustrated in figure 10a, a thermal fluid storage tank for containing a volume of thermal fluid, the thermal fluid storage tank connected to a heat transfer fluid circuit portion that flows through the active heating unit 8 and any optional heat exchanger units 9, the thermal fluid circulating by means of a heating circuit pump P2. Examples of appropriate thermal fluids are described in more detail below. In a second embodiment, the thermal energy storage unit 7 comprises a phase change media tank also connected via a heat transfer circuit to the active heating unit 8 and any optional heat exchangers 9, the thermal fluid flowing in the circuit by means of the heating circuit pump P2. The phase change media tank may comprise phase change materials for instance in a layered structure of phase change media such as high temperature salts bathed in a tank filled with hot thermal fluid.

[0070] The thermal fluid should satisfy the following requirements:

[0071] • Stability as a liquid in a wide temperature range, from below 0°C to around 300°C depending on the metal hydride and the desired outlet pressure P3024PC00

[0072] • Good thermal and operational properties such as high heat capacity, low viscosity, and high thermal conductivity

[0073] For these reasons, thermal oils such as benzyltoluene, dibenzyltoluene or other synthetic aromatic hydrocarbon mixture could be suitable. Common fluids such as water or glycol are usually unsuitable because of their low boiling point, despite good thermal properties.

[0074] The thermal energy storage unit needs to be insulated in order to increase the efficiency of the system and minimizing the thermal losses. As an example, for a cylindrical storage tank of 4m3 with a diameter of 1.6m and a height of 2m, 20cm of thickness of medium temperature resistant mineral wool fibers with a thermal conductivity of 0.075 W / mK would yield heat losses around 1 kW when the storage is full.

[0075] The sensible heat capacity of the thermal fluid, respectively phase change media contained in the thermal energy storage unit 7 is configured to provide sufficient thermal energy to the metal hydrides of the hydrogen storage unit 2 to desorb from the metal hydride and compress the hydrogen to the output refueling pressure, which as previously mentioned may be up to 380 bars. The volume of thermal fluid and the specific thermal capacity of the thermal fluid is thus configured such that the temperature drop of the thermal fluid that heats up the metal hydrides during the desorption process, provides a large portion or all of the energy required by the endothermic desorption process.

[0076] The energy provided by the sensible heat capacity of the volume of thermal fluid contained in the thermal storage unit provides at least 80% of the required energy for the desorption of at least 80% of the stored hydrogen contained in the metal hydrides of the hydrogen storage unit 2. Preferably, the energy provided by the sensible heat capacity of the volume of thermal fluid contained in the thermal storage unit provides at least 90%, more preferably at least 100%, of the required energy for desorption of at least 80% of the stored hydrogen contained in the metal hydrides of the hydrogen storage unit 2.

[0077] A very rapid heating up of the metal hydrides and thus a very rapid desorption process and accompanying pressure increase of hydrogen may thus be formed by the rapid release of stored sensible thermal energy provided by the thermal energy storage unit during the desorption and compression operation mode.

[0078] The metal hydride containers of the hydrogen storage unit 2 are surrounded by a thermal fluid container that allows the thermal fluid to flow around the containers and transfer heat from P3024PC00 the thermal transfer fluid to the metal hydride container walls by conduction. A forced liquid flow due to the pumping operation ensures rapid heat exchange between the thermal fluid and the metal hydride containers. In view of the pre-heated thermal fluid a very rapid transfer of thermal energy can be performed to achieve a short desorption and compression of hydrogen up to high pressures required for vehicle refueling.

[0079] As illustrated in figure 4, during absorption of hydrogen in the hydrogen storage unit 2, the hydrogen inlet valve Vi is open and hydrogen outlet valve Vo is closed such that the containers of the hydrogen storage unit 2 receive low pressure hydrogen, for instance in a range of 30 to 40 bars, from a hydrogen source. The heating system 4 is disconnected from the hydrogen storage unit 2 whereby the heating circuit valves Vhl, Vh2 are in a closed state. A portion of the heat transfer fluid circuit that circulates between the hydrogen storage unit 2 and the cooling system 3 is open and the heat transfer fluid pump Pl activated and circulating the thermal fluid between the hydrogen storage unit 2 and cooling system 3. The first cooling circuit valve Vcl is open such that the thermal fluid flows through the active cooling machine 5.

[0080] The absorption process is exothermic and the cooling machine 5 thus serves to cool the metal hydride containers during the absorption process. As mentioned previously, the cooling machine may be coupled to a heat exchanger that transfers the recovered heat, which may be transferred to the heating system 4 via the heat exchanger 9, potentially using a heat pump to maximize the amount of heat recovered.

[0081] Figure 5 shows a state in which the hydrogen storage unit 2 has been filled with hydrogen and the hydrogen is stored in a safe manner in view of the use of the metal hydrides, until it is required for fueling. In this storage state, all of the valves are in a closed state and the pumps in an off state. Optionally, the heating system 4 may be in operation during the hydrogen storage state since the heating up of the thermal energy storage unit 7 is performed independently of the hydrogen absorption and hydrogen storage process.

[0082] The independent heating of the thermal energy storage is shown in figure 4 which as mentioned above may also occur in the state shown in figure 5. In this situation, the heating circuit valves Vhl and Vh2 that connect the heating system 4 to the hydrogen storage unit 2 are in a closed position, the active heating unit 8 is on, and the heat circuit pump P2 is on thus circulating the thermal fluid between the thermal energy storage unit 7 and the heating device(s) 8, 9. The active heating unit 8 may be regulated as a function of the heat supplied P3024PC00 by the heat exchanger(s) 9 to provide complementary heating power as needed to raise the temperature of the thermal fluid contained in a thermal energy storage unit 7 to the desired level for release through the hydrogen storage unit 2 upon demand when hydrogen desorption and compression for a vehicle refueling operation is required.

[0083] Figure 6 shows a refueling operation whereby the heating circuit valves Vhl, Vh2 are open and the heat transfer fluid pump Pl on such that the thermal fluid contained in the heating system 4 flows through the hydrogen storage unit 2. During desorption and compression, the hydrogen inlet valve Vi is closed and the hydrogen outlet valve Vo is opened for transferring pressurized hydrogen gas to a vehicle. The hydrogen gas passes through a cooling system 3, preferably through the active cooling machine 5, such that the heated hydrogen gas is cooled down to an acceptable operational temperature. Here also the heat recovered by the cooling machine during this process may be transferred to the heating system 4 via a heat exchanger 9. In this process example illustrated in figure 6, the thermal energy storage unit 7 is shut off from the active heating unit 8 and heat exchanger 9, however it is possible also during the desorption and compression process to have the heating system on and heating circuit pump P2 on in order to supply complementary energy to the thermal fluid during the desorption and compression process.

[0084] Referring to figure 7, after the refueling process, the hydrogen storage unit 2 may be further cooled by the cooling system 3, with the heat transfer fluid pump Pl on and the second cooling circuit valve Vc2 open such that the thermal fluid flows through the passive cooler 6. This allows to cool the metal hydrides in an efficient manner prior to recharging with hydrogen from the hydrogen source. As illustrated in figure 8, the cooling down of the metal hydrides may however also be performed by the active cooling machine 5 for efficient recovery of the thermal energy or for more rapid cooling in order to shorten the time to recharge the hydrogen storage unit 2 with hydrogen from the hydrogen source.

[0085] A specific example of a hydrogen fueling system for refueling of a 28kg and 350 bars tank in 15 minutes is described below for illustrative purposes. In this example, the hydrogen fueling system comprises:

[0086] • A plurality of containers containing metal hydride in a quantity sufficient to compress 28 kg of hydrogen, for instance weighing about 7800 kg in which there is about 4000 kg of metal hydride and 3800 kg of steel for the containers, occupying a volume of around 2 m3;

[0087] • An active heating unit, for example including an electrical in-line heater with a power of 75 kW; P3024PC00

[0088] • A thermal energy storage unit, for example comprising an insulated tank storing about 3000 kg of thermal fluid, such as benzyltoluene, at 250°C prior to the desorption process. In addition to an insulation material layer, the insulated tank may further be jacketed by an inert gas layer depending on the kind of thermal fluid used. The sensible thermal energy stored in this example provides around 230 kWh of heat during the 15 minutes needed to desorb 28 kg of hydrogen and a maximum of around 1.1 MW of heat when the desorption rate is maximum. This corresponds to around 8.2 kWh per kg of hydrogen. The storage can be sized depending on the type of vehicle which needs to be recharged: a truck typically requires around 30kg of hydrogen, a car around 5 kg and a forklift around 1.5 kg;

[0089] • A thermal fluid, for example benzyltoluene, being circulated by the pump at up to 50 m3 / h;

[0090] • A cooling machine with a cooling power of about 55kW; and

[0091] • Balance of plant components such as valves, pumps, sensors and heat exchangers.

[0092] The working principle of the hydrogen fueling system according to embodiments of the invention may be described in the following four processes:

[0093] • Absorption: Hydrogen is being absorbed within the metal hydride at a first pressure, for instance a constant inlet pressure of 30 bars. This process is exothermic, and the hydrogen storage unit needs to be cooled and maintained at a low temperature, for instance at around - 25°C. The duration of this absorption process can vary depending on the different requirements of the fueling station. In the example provided above, for 4 hours, an average cooling power of about 20 kW is required. At the end of this step, the hydrogen can be stored safely indefinitely within the metal hydride containers.

[0094] • Heat-up: The metal hydride containers of the hydrogen storage unit are heated up, for instance to ambient temperature, to increase the pressure of hydrogen in the hydrogen storage unit in preparation for the desorption phase.

[0095] • Heat-up and desorption: This step needs to be carried out as quickly as possible, preferably in less than 20 minutes, for instance in 10 to 15 minutes. Sensible thermal energy is used to provide very high instant heating power to increase the pressure within the metal hydride stack and compensate for the endothermic process of hydrogen desorption. The hot thermal fluid at above 250°C enables a fast increase of the pressure of the hydrogen desorbed from the metal hydride in the containers of the hydrogen storage unit.

[0096] • Cool-down: The system is cooled down to be ready for the next cycle. This step may be split into two by first cooling to around ambient temperature and then to about -25°C required to start the following absorption phase. P3024PC00

[0097] The thermal energy storage unit of the present invention offers several advantages when compared to conventional metal hydride-based hydrogen compression systems. First of all, the heating system can be operated when excess energy, for instance solar or wind energy, is available to recharge the thermal energy storage unit. Secondly, the high initial temperature of the thermal fluid of the thermal energy storage unit enables a very high thermal power output at the start of the desorption process. Indeed, as seen in Figure 3 which corresponds to the above-described specific example, in the first 5 minutes, the thermal power transmitted from the thermal energy storage unit to the metal hydride reaches around 1.1 MW. This is very helpful as it enables a high mass flow rate of hydrogen at throughout the process. Finally, the high temperature available also allows a finer control of the exchanged heat and therefore the desorption rate and the pressure ramp up rate.

[0098] P3024PC00

[0099] List of features

[0100] Hydrogen fueling system 1

[0101] Control system 10

[0102] Temperature sensors BT

[0103] Pressure sensors BP

[0104] Hydrogen storage unit 2

[0105] Container(s)

[0106] Hydrogen inlet Hi

[0107] Hydrogen outlet l lo

[0108] Metal Hydride

[0109] Heat transfer fluid inlet 12i

[0110] Heat transfer fluid outlet 12o

[0111] Heat transfer fluid pump Pl

[0112] Cooling system 3

[0113] Active cooling machine 5

[0114] Hydrogen inlet 14i

[0115] Hydrogen outlet 14o

[0116] Passive cooler 6

[0117] Air cooler

[0118] Cooling circuit valves Vcl, Vc2

[0119] Heating system 4

[0120] Thermal energy storage unit 7

[0121] Fluid storage tank

[0122] Phase change media tank

[0123] Active heating unit 8

[0124] Electrical heater

[0125] Heating circuit valves Vhl, Vh2, Vh3, Vh4

[0126] Heat exchanger 9

[0127] Heating circuit pump P2

[0128] Heat transfer fluid circuit 19

[0129] Hydrogen output to fueling station 16

[0130] Hydrogen vent 17

[0131] Heat transfer fluid vent 18

[0132] Hydrogen inlet valve Vi

[0133] Hydrogen outlet valve Vo

Claims

P3024PC00Claims1. A hydrogen fueling system (1) comprising a control system (10), a hydrogen storage unit (2), a cooling system (3), a heating system (4), and a heat transfer fluid circuit interconnecting the hydrogen storage unit (2) to the cooling system (3) and the heating system (4), the hydrogen fueling system configured for receiving hydrogen from a hydrogen source at a first pressure through a hydrogen inlet (Hi) and outputting hydrogen at a second pressure higher that the first pressure through a hydrogen outlet (16), the hydrogen storage unit comprising one or more containers lodging therein a metal hydride adapted for hydrogen storage, the cooling system connected to the heat transfer fluid circuit via at least one valve (Vcl, Vc2) and the heating system connected to the heat transfer fluid circuit via at least one valve (Vhl, Vh2), characterized in that the heating system (4) comprises a thermal energy storage unit (7) including a tank containing a volume of thermal liquid connected to a heating unit (8, 9), the volume of thermal fluid comprising a sensible thermal energy capacity exceeding 80% of a thermal energy required by the hydrogen storage unit to desorb and compress to the second pressure at least 80% of the hydrogen stored in a full hydrogen storage unit (2).

2. The system of claim 1 wherein the sensible thermal energy capacity exceeds 90%, preferably reaches or exceeds 100%, of the thermal energy required by the hydrogen storage unit to desorb and compress at least 80%, preferably at least 90%, more preferably 100% of the hydrogen stored in a full hydrogen storage unit (2).

3. The system of any preceding claim wherein the heating system includes an active heating unit (8) comprising an electrical heater.

4. The system of any preceding claim wherein the heating system (4) comprises at least one heat exchanger (9).

5. The system of any preceding claim wherein the cooling system (3) includes an active cooling machine (5) the active cooling machine including a hydrogen inlet (14i) connected to a hydrogen outlet (1 lo) of the hydrogen storage unit (2) and a hydrogen outlet (14o) connected to the hydrogen system outlet to fueling station (16).

6. The system of any preceding claim wherein the cooling system further comprises a passive cooler (6), for instance an air cooler.P3024PC007. The system of the preceding claim wherein the passive cooler (6) is connected to the heat transfer fluid circuit via a cooling circuit valve (Vc2).

8. The system of any preceding claim in combination with claim 5 wherein the active cooling machine is connected to the transfer fluid circuit via a cooling circuit valve (Vcl).

9. The system of any preceding claim wherein the thermal energy storage unit comprises a thermal fluid storage tank and / or a phase change media tank.

10. The system of any preceding claim wherein the heating units (8, 9) are connected to the thermal energy storage unit via a heat transfer fluid circuit portion comprising one way to valves (Vh3, Vh4) and a heat circuit pump (P2).

11. The system of any preceding claim wherein the heating system is connected to the heat transfer fluid circuit via at least two heating circuit valves (Vhl, Vh2) at an inlet and outlet respectively of the heating system.

12. The system of any preceding claim wherein the hydrogen unit (2) comprises a heat transfer fluid inlet ( 12i) and heat transfer fluid outlet (12o) connected to the heat transfer fluid circuit including a heat transfer fluid pump (Pl) to circulate thermal fluid through the hydrogen storage unit container, the transfer fluid flowing around the metal hydride containers during a cooling or heating process.

13. The system of any preceding claim wherein the cooling system is connected via a heat exchanger (9) to the heating system (4).

14. A method of operating a hydrogen fueling system according to any preceding claim comprising the following steps as a function of the mode of operation:- a hydrogen storage mode in which hydrogen at said first pressure is input into the metal hydride containers of the hydrogen storage unit during which the hydrogen inlet valve (Vi) is opened, the hydrogen outlet valve (Vo) is closed, at least one cooling circuit valve (Vcl, Vc2) is opened, and a heat transfer fluid pump (Pl) is on to cool the hydrogen storage unit with thermal fluid flowing through the cooling system;- a mode of desorption and compression for fueling a vehicle in which the hydrogen inlet18P3024PC00 valve (Vi) is closed, the hydrogen outlet valve (Vo) is opened, and the heating system (4) is connected to the hydrogen storage unit (2) for heating up the metal hydrides in the containers of the hydrogen storage unit, the heating circuit valves (Vhl, Vh2) being opened for fluid from the thermal energy storage unit (7) to flow through the hydrogen storage unit (2).

15. The method of the preceding claim wherein in a hydrogen storage state or during the hydrogen absorption state the thermal energy storage unit is connected to the heating unit and the heating circuit pump (P2) is on, configured to heat the thermal fluid or phase change media in the thermal energy storage unit.

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