Low temperature and fast cylinder filling with circulating path

Abstract

A method and apparatus for filling a gas cylinder (20) is provided in which the method can include the steps of fluidly connecting a main gas flow line (12) from a gas dispenser (10) to the gas cylinder, thereby providing a fluid connection between the gas dispenser and the gas cylinder; fluidly connecting a circulating line (22) of the gas dispenser with the gas cylinder, thereby providing a second fluid connection between the gas dispenser (10) and the gas cylinder (20); flowing gas from the gas dispenser to the gas cylinder using the main gas flow line (12); flowing warm return gas from the gas cylinder to the gas dispenser (10) using the circulating line (22); cooling the warm return gas within the gas dispenser (10); and sending the cooled return gas to gas cylinder (20) of the gas cylinder using the main gas flow line (12).

Description

[0001] LOW TEMPERATURE AND FAST CYLINDER FILLING WITH CIRCULATING PATH

[0002] Cross Reference of Related Applications

[0003] This patent application claims priority to U.S. Provisional Patent Application Serial No. 63 / 523.531 filed on June 27, 2024, which is hereby incorporated by reference in its entirety’.

[0004] Background of the Invention

[0005] Hydrogen pressure vessels in Fuel Cell Electric Vehicles (FCEVs) are Type 4 cylinders, which are made of an inner liner that is wrapped in composite and solidified with an epoxy resin. The epoxy provides strength for the carbon fiber composite at normal temperatures. At a temperature above 85°C. the epoxy has a glass transition temperature at which point the epoxy loses strength. The temperature should never exceed 85°C in order to maintain the integrity / strength of hydrogen pressure vessels in vehicles.

[0006] A hydrogen cylinder experiences warming when it is filled from a loyv pressure to a high pressure due to the heat of compression (adiabatic heating). In order to prevent the temperature from increasing above 85°C in the cylinder, the automotive manufacturers only permit vehicles to be filled at stations that follow SAE fueling protocols which are designed to limit the temperature to less than 85°C. For a typical fill (T40 H70), the SAE fueling protocols require hydrogen to be chilled (-33°F to -40°F) and the flow rate is controlled based on a pressure ramp table. A similar approach of chilling hydrogen and controlling the flow' rate is applied to fueling practices for other vehicles.

[0007] Using chilled hydrogen is very expensive for hydrogen stations. Impacts of the chiller are: • high CAPEX. Chillers needed for stations are non-standard chillers, which causes high CAPEX. In addition, heavy-duty stations will require a large chilling capacity, which has a maj or CAPEX impact;

[0008] • high OPEX. The chilling fluid loses cold to the ambient and requires constant operation of the chiller in order for the station to be prepared for a vehicle fueling;

[0009] • high inertia in the system. The chilling fluid must always remain cold because the chilling circuit must be cold when a car arrives. (Not able to turn on the chiller and only cool the H2. Must maintain the recirculating fluid at a cold temperature.);

[0010] • poor reliability. These non-standard chillers have multiple systems that fail frequently: circulating pump, specialized compressors, refrigerant leaks, etc.;

[0011] • complexity of station design. Each piece of equipment adds substantial complexity to station reliability, operational cost, and design. Chillers are an additional unit that require significant engineering and controls work to be properly integrated to the station; and

[0012] • increased footprint. In particular, the refrigerant / air heat exchanger is large and must be designed for appropriate air flow.

[0013] • increased noise. The chiller fans are constantly operating and cause the most significant noise for neighbors, customers, and the public.

[0014] In addition to maintaining appropriate temperatures in carbon fiber wrapped cylinders, cooling the gas in a cylinder allows the gas to reach the desired density while avoiding excessive overpressures during filling. Regardless of cylinder type, all cylinder-filling operations see a temperature increase due to the heat of compression, and cylinders need to be filled with the correct density of product. As the temperature increases, the cylinder has to be filled to a higher pressure. For example, the target density of a EI70 fuel cell electric vehicle is approximately 2.5 lb / ft\ The target density can be reached at 700 barg and 70°F, but due to the temperature rise, the pressure is usually much higher. The pressure needed to reach 2.5 lb / ft3at 85°C is approximately 12,400 psig. Due to the temperature constraint at 85 °C (for the cylinder integrity ), 12,400 psig is the maximum pressure that a station would ever need to supply to a vehicle, and if the temperature within the cylinder is lower, than the pressure needed to fill the cylinder is lower. Without chilling of the gas, the temperature of the cylinder would exceed 85°C, which would require much greater pressure for filling the cylinder.

[0015] Therefore, an invention is needed to avoid a chiller but still 1) allow the temperature to remain below 85°C in order to protect the cylinder integrity, and 2) cool gas within the cylinder so that the target density7can be achieved at lower pressures.

[0016] Summary of the Invention

[0017] In certain embodiments, the invention can include a process for filling a cylinder(s) with the following flow paths:

[0018] • Flow paths o hydrogen supplied from a high pressure source (buffer or compressor or pump) to the dispenser / manifold; o hydrogen from the cylinder that is recirculating back to the dispenser / manifold from the cylinder; o the combined hydrogen stream that is flowing from the dispenser / manifold to the cylinder.

[0019] • Components o gas jet Venturi ejector: Mixing junction where the incoming gas provides energy to induce flow in the circulating path to form a combined stream; and o heat exchanger: The heat exchanger provides an interface where heat is transferred from the hydrogen to a cooler fluid. The cooler fluid can be air, cooling water, liquid hydrogen, cry ogenic gaseous hydrogen, or any other refrigerant.

[0020] Pressure of the cylinder rises as hydrogen flows into the system from the incoming gas stream. As the gas is compressed in the cylinder, the temperature increases. The circulating path allows gas to exit the cylinder and be cooled to remove the heat of compression. While the drawing shows two separate lines connecting the cylinder to the manifold / dispenser, in an embodiment not shown, the device can be configured such that both lines are disposed within a single hose, preferably with an insulation layer separating the two lines.

[0021] In one embodiment of the invention, a method for filling a hydrogen cylinder disposed within a vessel is provided. In this embodiment, the method may include the steps of: a) fluidly connecting a main gas flow line from a hydrogen gas dispenser to the vessel, thereby providing a first fluid connection between the hydrogen gas dispenser and the hydrogen cylinder of the vessel; b) fluidly connecting a circulating line of the hydrogen gas dispenser with the hydrogen cylinder of the vessel, thereby providing a return fluid connection between the hydrogen gas dispenser and the hydrogen cylinder of the vessel; c) flowing a pressurized hydrogen gas feed flow through the hydrogen gas dispenser; d) cooling the pressurized hydrogen gas feed flow; e) flowing cold hydrogen gas to the vessel using the main gas flow line; I) flowing return hydrogen gas from the vessel to the hydrogen gas dispenser using the circulating line; g) introducing the return hydrogen gas from the circulating line to a Venturi ejector, wherein the pressurized hydrogen gas feed flow also flows through the Venturi ejector, thereby providing a driving force for the return hydrogen gas to flow through the hydrogen gas dispenser; and h) sending the return hydrogen gas to the hydrogen cylinder of the vessel.

[0022] In optional embodiments of the invention: • step d) occurs within the hydrogen gas dispenser;

[0023] • step d) is accomplished using a heat exchanger;

[0024] • the heat exchanger uses a cooling fluid selected from the group consisting of cooling water, a refrigerant, and ambient air;

[0025] • the method may further include the step of cooling the return hydrogen gas prior to step h);

[0026] • the method may further include the step of cooling the return hydrogen gas within the hydrogen gas dispenser;

[0027] • the method may further include the step of cooling the return hydrogen gas within the circulating line upstream of the Venturi ejector;

[0028] • the circulating line and the main gas line are disposed within a common conduit;

[0029] • the common conduit comprises an insulation layer disposed between the main gas line and the circulating line;

[0030] • the circulating line and the main gas line are each disposed within a different conduit; and / or

[0031] • the vessel is selected from the group consisting of a motorized bike, motorcycle, car, bus, semi-truck, a forklift, watercraft, amphibious vehicle, aircraft, and spacecraft.

[0032] In another embodiment of the invention, the method for filling a hydrogen cylinder may include the steps of: establishing a primary fluid connection between a gas dispenser and the hydrogen cylinder; establishing a return fluid connection between the gas dispenser and the hydrogen cylinder; transferring hydrogen gas from the gas dispenser to the hydrogen cylinder using the primary fluid connection; transferring a return gas from the hydrogen cylinder to the gas dispenser using the return fluid connection; cooling the return gas within the gas dispenser to produce a cooled return gas; and sending the cooled return gas to the hydrogen cylinder, wherein the return fluid connection comprises an absence of a compression device that uses externally provided electricity to perform compression.

[0033] In optional embodiments of the method:

[0034] • the gas dispenser comprises a Venturi ejector having a lower pressure inlet, a higher pressure inlet, and an intermediate pressure outlet, wherein the Venturi ejector is configured to receive the return gas from the hydrogen cylinder in the lower pressure inlet and a pressurized hydrogen gas feed in the higher pressure inlet;

[0035] • the method may further include the step of mixing the return gas and the pressurized hydrogen gas feed within the Venturi ejector before flowing the resulting mixed stream through the intermediate pressure outlet of the Venturi ejector; and / or

[0036] • the step of cooling the return gas within the gas dispenser comprises providing a heat exchanger downstream of the Venturi ejector, such that the heat exchanger is configured to cool the mixed stream from the intermediate pressure outlet of the Venturi ejector.

[0037] In another embodiment of the invention, an apparatu for transferring a gas from a gas dispenser to a gas cylinder is provided. In this embodiment, the apparatus may include: a main gas flow transfer line that is configured to fluidly connect an outlet of the gas dispenser and an inlet of the gas cylinder, such that once connected, the main gas flow line provides fluid communication between the outlet of the gas dispenser and the inlet of the gas cylinder; a return flow line that is configured to fluidly connect an outlet of the gas cylinder and a return inlet of the gas dispenser, such that once connected, the return flow line provides fluid communication between the return inlet of the gas dispenser and the outlet of the gas cylinder; and a Venturi ejector in fluid communication with the return flow line and the main gas flow transfer line, wherein the Venturi ejector is configured to receive a gas flow from the return flow line and send the gas flow to the main gas flow transfer line. In optional embodiments of the apparatus:

[0038] • the V enturi ej ector comprises a lower pressure inlet, a higher pressure inlet, and an intermediate pressure outlet, wherein the Venturi ejector is configured to receive the gas flow from the return flow line in the lower pressure inlet and a pressurized hydrogen gas feed in the higher pressure inlet;

[0039] • the apparatus may further include a heat exchanger disposed within the gas dispenser, wherein the heat exchanger is disposed downstream the Venturi ejector;

[0040] • the main gas flow- transfer line and the return gas flow line are disposed within a common conduit;

[0041] • the main gas flow- transfer line is disposed w-ithin a first conduit and the return gas flow line is disposed within a second conduit; and / or

[0042] • the gas cylinder is disposed within a vessel, wherein the vessel is selected from the group consisting of a motorized bike, motorcycle, car, bus, semi -truck, a forklift, watercraft, amphibious vehicle, aircraft, and spacecraft.

[0043] Brief Description of the Drawings

[0044] These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

[0045] FIG. 1 shows an embodiment of the invention.

[0046] FIG. 2 shows a gas Venturi ejector in accordance wdth an embodiment of the invention. FIG. 3a provides a first embodiment of a cross sectional view of a common conduit used to house two flow lines.

[0047] FIG. 3b provides a second embodiment of the cross sectional view of the common conduit used to house two flow lines.

[0048] FIG. 3c provides a third embodiment of the cross sectional view of the common conduit used to house two flow lines.

[0049] Detailed Description

[0050] While the invention will be described in connection with several embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all the alternatives, modifications and equivalence as may be included within the spirit and scope of the invention defined by the appended claims.

[0051] The hydrogen supplied from a high-pressure source may be warmer than ambient temperature due to reverse Joule-Thomson expansion or because the hydrogen is provided from a compressor. Also, the hydrogen recirculating from the cylinder back to the dispener / manifold will be warmer than ambient temperature due to the heat of compression that occurs in the cylinder during filling. As hydrogen from the high-pressure source flows through the Venturi j et ej ector, the V enturi j et ej ector causes a lower pressure to be realized where the recirculating path connects to the jet Venturi ejector. This lower pressure at the jet Venturi ejector causes a pressure gradient in the recirculating path that allows flow to occur.

[0052] While the hydrogen from the high-pressure source is flowing through the Venturi jet ejector, there is a pressure drop that occurs. Due to the reverse Joule-Thomson effect, this pressure drop causes a simultaneous temperature increase. Due to the warm temperature of the recirculating fluid and the warming of the high-pressure hydrogen that occurs during pressure drop through the Venturi jet ejector, a preferred location to remove heat from the system is downstream of the V enturi j et ej ector, and the heat exchanger would be preferably placed in this location; however, the invention is not so limited. For example, the heat exchanger could also be placed on the recirculating path, or on the high- pressure hydrogen line coming into the manifold / dispenser.

[0053] Now turning to FIG. 1. In the embodiment shown, the apparatus may include hydrogen gas dispenser 10, main gas flow line 12, and circulating line 22. The hydrogen gas dispenser 10 is configured to fluidly connect with cylinder 20 of a vessel (outline of vessel not shown for clarity purposes) via main gas flow line 12 and circulating line 22. During operation, once the two lines are connected between the dispenser 10 and the cylinder 20, pressurized hydrogen gas feed 2 is sent into hydrogen gas dispenser 10, wherein it passes through Venturi ejector 9.

[0054] Since pressurized hydrogen gas feed 2 is at a higher-pressure than the circulating line 22, the flow of the pressurized hydrogen gas feed 2 through the Venturi ejector 9 acts as a pseudopump by drawing low er-pressure gas from the cylinder 20 into the low pressure inlet 11 of the Venturi ejector 9. Therefore, once the main gas flow line 12 and the circulating line are connected to the dispenser and the flow of pressurized hydrogen gas feed 2 is started, the apparatus is configured to withdraw w arm hydrogen gas from cylinder 20 via circulating line 22, wherein it enters the dispenser 10, and is subsequently combined with pressurized hydrogen gas feed 2 within Venturi ejector 9.

[0055] The combined hydrogen flow may then be cooled in heat exchanger 25, with the resulting cooled hydrogen gas being sent to cylinder 20 via the main gas flow line 12, thereby providing hydrogen gas to the cylinder of the vessel within the appropriate temperature range and thus preventing the gas within the cylinder from exceeding the maximum temperature range of the cylinder. Furthermore, heat from increasing of pressure within the cylinder is advantageously removed with the hot hydrogen gas leaving cylinder through the circulating line 22, wherein it is ultimately cooled before returning to the cylinder via the main gas flow line 12.

[0056] In another embodiment, the hydrogen transferred to the cylinder can be measured Fi (e.g., in order to be able to accurately charge the customer). The measurement of hydrogen with these flow paths is less straightforward because of the returning path. Two main options are available: 1) one flowmeter 41 on the high-pressure hydrogen path will measure all of the hydrogen added to the cylinder and the dispenser, or 2) the amount of hydrogen transferred to the vehicle can be measured by the difference of two flowmeters. For the difference of two flowmeters, one flowmeter 45 can be used to measure the hydrogen on the combined stream and the second flowmeter 43 can be used to measure the hydrogen returning to the dispenser. The difference of the outgoing flow (combined path) minus the returning flow' (recirculating path) will determine the amount of hydrogen transferred to the cylinder.

[0057] FIG. 2 provides a Venturi gas ejector in accordance w ith an embodiment of the invention. In the embodiment shown, the Venturi ejector 9 includes a lower-pressure inlet 11, a higher- pressure inlet 13, and an intermediate pressure outlet 15. The pressurized hydrogen gas feed 2 is introduced into the higher-pressure inlet, wherein it passes through a nozzle and then diffuser. As noted previously, this results in a driving force for the lower-pressure gaseous hydrogen in circulating line 22 to enter into lower-pressure inlet 13 and ultimately mix with the pressurized hydrogen gas feed 2. The resulting combined hydrogen flow, which is at an intermediate pressure, exits Venturi gas ejector 9 at intermediate pressure outlet 15, wherein it is preferably then sent for cooling in heat exchanger 25. Non-limiting potential vessels this may be used for may include: automobiles, buses, heavy- duty semi-trucks, forklifts, portable cylinders, aircraft, watercraft, standalone-compressed-gas cylinders, etc.

[0058] As compared to prior art, certain embodiments of the present invention allow for fueling of a gas cylinder with lower power consumption, reduced maintenance, reduced engineering design costs, and lower equipment costs.

[0059] In alternative embodiments, the apparatus may include one or more flow meters located in various positions. For example, a flow meter 11 can be placed on the incoming stream 2 to determine how much hydrogen enters the hydrogen gas dispenser 10. Two flowmeters can be used to measure the amount of hydrogen returning from the customer in the circulating line 22 and the amount of hydrogen provided to the customer in the main gas flow line 12.

[0060] Additionally, while the cooling is shown using heat exchanger 25 that is located within dispenser 10 and downstream of Venturi ejector 9, it is possible to cool at different locations of the process. For example, the cooling may immediately after the Venturi ejector as shown, or it may also include cooling of the circulating line 22, or on the main gas flow line 12 prior to entering the cylinder 20. Due to the heat of expansion of hydrogen though, it is preferable to have the cooling step downstream of the Venturi ejector. Cooling can also occur outside of the dispenser.

[0061] Moreover, while not required, a compressor or blower can be included to improve flow through the circulating path.

[0062] The Venturi jet ejector is a well-known component, and the sizing of the Venturi jet ejector depends on the recirculating flow. In order to change the flow through the recirculating path, several options are available: multi nozzle ejector, variable flow7ejector, or multiple Venturi jet ejector. Instead of inducing flow by using a Venturi jet ejector, the flow within the recirculating path can be induced by a blower or compressor on the recirculating path. When the flow through the recirculating path is variable, the temperature of the recirculating path can be monitored to determine if more flow or less flow should be recirculated for cooling.

[0063] The Venturi ejector can be one device or multiple devices used at the same time, or even multiple devices of different sizes for different flow conditions. A variable-type V enturi ej ector can also be used in accordance with various embodiments of the invention.

[0064] Those of ordinary skill in the art will recognize that the heat exchanger may be of several designs: plate heat exchanger, shell and tube heat exchanger, forced air over finned tubes, natural air convection over finned tubes, tube in tube heat exchanger, or other designs. The temperature of the combined stream can be monitored 47 downstream of the heat exchanger to ensure that the heat exchanger is properly cooling the hydrogen stream. In an additional embodiment, the dispenser may comprise a controller that is configured to receive data from various flow meters 41, 43, 45 and / or temperature indicators 47. Based on this data, the controller can determine the net amount of hydrogen gas sent to the cylinder, and also adjust a flow rate of the refrigerant and / or mixed hydrogen stream entering the heat exchanger. The former can help determine the price charged, while the latter can assist in maintaining a proper temperature within main gas flow line 12, and ultimately, the cylinder 20.

[0065] The heat exchanger 25 can be any type of heat exchange system including fins to reject heat to ambient air. The cooling fluid can be any fluid that removes heat from the warm hy drogen stream (e.g., cooling water, refrigerant, ambient air, etc.). The main gas flow and the circulating path can be connected to the cylinder or inserted / removed from the cylinder in any position. Additionally, while main gas flow line 12 and circulating line 22 are shown as two separate conduits, it is possible to also have the two lines combined into one main hose. FIGs. 3a, 3b, and 3c provide non-limiting examples of three different such configurations. For example. FIG. 3a provides an embodiment in which the two lines 12, 22 would be within one common conduit 19, preferably with insulation between them to reduce heat transfer between the two paths.

[0066] FIG. 3b provides an example of an embodiment in which the circulation line 22 is a separate partition in one side of the main gas flow line 12. FIG. 3c provides an example in which the two lines can be more or less concentric with each other. Of course, the invention should not be limited to the embodiments shown in FIGs. 3a, 3b, and 3c. Rather, those of ordinary skill in the art will recognize that numerous other alternatives may exist, and they are intended to be encompassed within the present invention.

[0067] Use of a single conduit for both lines 12, 22 advantageously allows for a single hose / conduit connection from the dispenser 10 to the cylinder 20, while providing hydrogen gas to the cylinder and transferring warm hydrogen gas from the cylinder to the dispenser.

[0068] One advantage of certain embodiments of the present invention is that the hydrogen gas transferred to the gas cylinder does not have to be at cryogenic temperatures (e.g., -30°C to - 40°C), since the embodiments of the invention are able to remove heat buildup in the gas cylinder via the circulation line. Therefore, the gaseous hydrogen in the main flow transfer line can be at temperatures above 0°C. preferably between 0°C and 30°C. more preferably between 10°C and 25°C. These warmer temperatures help to prevent ice formation at the interface of main gas flow transfer line and the gas cylinder / vessel containing the gas cylinder. As such, certain embodiments of the invention provide improved performance and safety’ as compared to methods known heretofore. The cylinder can be one or multiple cylinders. The positions where hydrogen can enter the cylinder and the positions where hydrogen is removed from the cylinder may vary. In a preferred configuration for a single cylinder, hydrogen enters from one end and and warm hydrogen is removed from the opposite end of the cylinder. Also, the flows can be supplied and removed from a same end of the cylinder.

[0069] The dispenser can be, but is not limited to, an enclosure that houses components. Another embodiment of the dispenser utilizes a manifold of components that is not enclosed.

[0070] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0071] The singular forms "a", "an" and "the" include plural referents, unless the context clearly dictates otherwise.

[0072] "Comprising" in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e.. anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms "consisting essentially of' and “consisting of' unless otherwise indicated herein. “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0073] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0074] Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.

[0075] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

Claims

CLAIMSI claim:

1. A method for filling a hydrogen cylinder (20) disposed within a vessel, the method comprising the steps of a) fluidly connecting a main gas flow line (12) with ahydrogen gas dispenser (10) and the vessel, thereby providing a first fluid connection between the hydrogen gas dispenser (10) and the hydrogen cy linder (20) of the vessel; b) fluidly connecting a circulating line (22) with the hydrogen gas dispenser (10) and the hydrogen cylinder (20) of the vessel, thereby providing a return fluid connection between the hydrogen gas dispenser (10) and the hydrogen cylinder (20) of the vessel; c) flowing a pressurized hydrogen gas feed flow (2) through the hydrogen gas dispenser (10); d) cooling the pressurized hydrogen gas feed flow (2); e) flowing cool hydrogen gas to the vessel using the main gas flow line (12); f) flowing return hydrogen gas from the vessel to the hydrogen gas dispenser (10) using the circulating line (22); g) introducing the return hydrogen gas from the circulating line (22) to a Venturi ejector (9), wherein the pressurized hydrogen gas feed flow also flows through the Venturi ejector (9), thereby providing a driving force for the return hydrogen gas to flow through the hydrogen gas dispenser (10); and h) sending the return hydrogen gas to the hydrogen cylinder (20) of the vessel.

2. The method as claimed in Claim 1, wherein step d) occurs within the hydrogen gas dispenser (10).

3. The method as claimed in Claim 1, wherein step d) is accomplished using a heat exchanger (25).

4. The method as claimed in Claim 3, wherein the heat exchanger (25) uses a cooling fluid selected from the group consisting of cooling water, a refrigerant, and ambient air.

5. The method as claimed in Claim 1, further comprising the step of cooling the return hydrogen gas prior to step h).

6. The method as claimed in Claim 1, further comprising the step of cooling the return hydrogen gas within the hydrogen gas dispenser (10).

7. The method as claimed in Claim 1. further comprising the step of cooling the return hydrogen gas within the circulating line (22) upstream of the Venturi ejector (9).

8. The method as claimed in Claim 1, wherein the circulating line (22) and the main gas line are disposed within a common conduit (19).

9. The method as claimed in Claim 8, wherein the common conduit comprises an insulation layer disposed between the main gas line and the circulating line (22).

10. The method as claimed in Claim 1, wherein the circulating line (22) and the main gas flow line (12) are each disposed within a different conduit.

11. The method as claimed in Claim 1, wherein the vessel is selected from the group consisting of a motorized bike, motorcycle, car, bus, semi-truck, a forklift, watercraft, amphibious vehicle, aircraft, and spacecraft.

12. A method for fdling a hydrogen cylinder (20) , the method comprising the steps of: establishing a primary fluid connection (12) between a gas dispenser (10) and the hydrogen cylinder (20); establishing a return fluid connection (22) between the gas dispenser (10) and the hydrogen cylinder (20); transferring hydrogen gas from the gas dispenser (10) to the hydrogen cylinder (20) using the primary fluid connection (12); transferring a return gas from the hydrogen cylinder (20) to the gas dispenser (10) using the return fluid connection (22); cooling (25) the return gas within the gas dispenser (10) to produce a cooled return gas; and sending (12) the cooled return gas to the hydrogen cylinder (20), wherein the return fluid connection (22) comprises an absence of a compression device that uses externally provided electricity to perform compression.

13. The method as claimed in Claim 12, wherein the gas dispenser (10) comprises a Venturi ejector (9) having a lower pressure inlet (13), a higher pressure inlet (11), and an intermediate pressure outlet (15), wherein the Venturi ejector (9) is configured to receive the return gas fromthe hydrogen cylinder (20) in the lower pressure inlet (13) and a pressurized hydrogen gas feed (2) in the higher pressure inlet (11).

14. The method as claimed in Claim 13, further comprising the step of mixing the return gas and the pressurized hydrogen gas feed (2) within the Venturi ejector (9) before flowing the resulting mixed stream through the intermediate pressure outlet (15) of the Venturi ejector (9).

15. The method as claimed in Claim 13, wherein the step of cooling the return gas within the gas dispenser (10) comprises providing a heat exchanger downstream of the V enturi ej ector(9), such that the heat exchanger (25) is configured to cool the mixed stream from the intermediate pressure outlet (15) of the Venturi ejector (9).

16. An apparatus for transferring a gas from a gas dispenser (10) to a gas cylinder (20), the apparatus comprising: a main gas flow transfer line (12) that is configured to fluidly connect an outlet of the gas dispenser (10) and an inlet of the gas cylinder (20), such that once connected, the main gas flow transfer line (12) provides fluid communication between the outlet of the gas dispenser(10) and the inlet of the gas cylinder (20); a return flow line (22) that is configured to fluidly connect an outlet of the gas cylinder (20) and a return inlet of the gas dispenser (10). such that once connected, the return flow line (22) provides fluid communication between the return inlet of the gas dispenser (10) and the outlet of the gas cylinder (20); and a Venturi ejector (9) in fluid communication with the return flow line (22) and the main gas flow transfer line, wherein the Venturi ejector (9) is configured to receive a gas flow from the return flow line (22) and send the gas flow to the main gas flow transfer line (12).

17. The apparatus as claimed in Claim 16, wherein the Venturi ejector (9) comprises a lower pressure inlet (13), a higher pressure inlet (11), and an intermediate pressure outlet (15), wherein the V enturi ej ector (9) is configured to receive the gas flow from the return flow line (22) in the lower pressure inlet (13) and a pressurized hydrogen gas feed (2) in the higher pressure inlet (13).

18. The apparatus as claimed in Claim 16, further comprising a heat exchanger (25) disposed within the gas dispenser (10), wherein the heat exchanger (25) is disposed downstream the Venturi ejector (9).

19. The apparatus as claimed in Claim 16, wherein the main gas flow transfer line (12) and the return gas flow line (22) are disposed within a common conduit (19).

20. The apparatus as claimed in Claim 16, wherein the main gas flow transfer line (12) is disposed within a first conduit and the return gas flow line (22) is disposed within a second conduit.

21. The apparatus as claimed in Claim 16, wherein the gas cylinder (20) is disposed within a vessel, wherein the vessel is selected from the group consisting of a motorized bike, motorcycle, car, bus, semi-truck, a forklift, watercraft, amphibious vehicle, aircraft, and spacecraft.

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