Systems and methods with boil-off management for liquefied gas storage

Abstract

A system and method with boil-off management for liquefied fuel storage is provided. The system includes a cryotank for storing the liquefied fuel, a pump for supplying and compressing a first flow of the liquefied fuel, a heat exchanger for providing a cooling duty to the first flow of the liquefied fuel, and an expansion valve for expanding the first flow of the liquefied fuel after the heat exchanger into a multiphase flow including a liquid phase and a gas phase. The multiphase flow has a temperature lower than an initial temperature of the first flow from the cryotank. The system further includes a liquid vapor splitter for separating the liquid and gas phases in the multiphase flow. The liquid phase is returned to the cryotank.

Description

Detailed Description of the Invention

[0001] FIELD OF THE INVENTION FIELD OF THE DISCLOSURE The present disclosure relates generally to methods and systems for storing, transporting, or dispensing liquefied gases or fuels. More particularly, the disclosed subject matter relates to systems and methods for storing and / or refueling hydrogen.

[0002] (background) Many automobiles are currently powered by internal combustion engines with fossil fuels. Due to limited supply and adverse environmental impacts associated with burning petroleum-derived fuels, vehicles powered by alternative, environmentally friendly fuels, such as hydrogen, are currently being developed. Fuel cells can be used to generate electrical power for automobiles by electrochemically reacting hydrogen fuel with an oxidizer, such as air. Other hydrogen-powered vehicles can be powered by the combustion of hydrogen. Fueling or refueling fuel cell vehicles (FCVs) and other hydrogen-powered vehicles with hydrogen presents different challenges than adding petroleum-based fuels, such as gasoline, to vehicles.

[0003] Hydrogen refueling stations for fuel cell vehicles can store fuel as a gas or liquid before dispensing it to the vehicle as compressed gaseous hydrogen. Liquefied gases or fuels, such as liquid hydrogen, can be stored in cryogenic tanks insulated from the environment. However, heat leakage into the tank causes the liquefied gas to vaporize, producing "boil-off" vapor, as the liquid absorbs the heat leakage from the environment. The pressure inside the tank increases as vapor continues to accumulate inside the tank. The excess vapor must be vented to the environment through a relief valve to keep the tank under pressure, causing some loss of liquefied fuel or gas. A system with minimal or no boil-off is required.

[0004] (Summary of the Invention) The present disclosure provides systems and methods with boil-off management for the storage of liquefied gas or fuel, for example, the liquefied fuel includes or is hydrogen, and the system is for storing and / or using liquid hydrogen.

[0005] According to some embodiments, a system includes a cryotank configured to store liquefied fuel therein, a pump fluidly coupled to the cryotank, a heat exchanger coupled to the pump, an expansion valve, and a liquid vapor splitter fluidly coupled to the expansion valve. The pump is configured to provide or pump the first flow of liquefied fuel from the cryotank while compressing the first flow of liquefied fuel to a high pressure. The heat exchanger is configured to provide a cooling duty to the first flow of liquefied fuel from the pump. The expansion valve is configured to expand the first flow of liquefied fuel from the heat exchanger into a multiphase flow including a liquid phase and a gas phase. The multiphase flow has a temperature lower than the initial temperature of the first flow from the cryotank. The liquid vapor splitter is fluidly coupled to the expansion valve and configured to separate the liquid and gas phases in the multiphase flow. The liquid phase is configured to be returned to the cryotank.

[0006] In some embodiments, the liquefied fuel includes or is hydrogen. The pump comprises one or more submerged liquid pumps disposed within the cryotank and configured to compress and increase the pressure of the first flow of liquefied fuel being pumped.

[0007] In some embodiments, the system further comprises an expander turbine coupled to the heat exchanger and the expansion valve, the expander turbine configured to isentropically expand the first flow of liquefied fuel from the heat exchanger.

[0008] In some embodiments, the expansion valve is a Joule-Thomson (JT) valve. The system may further include an interlock chamber fluidly coupled to the cryotank and configured to return the liquid phase to the cryotank. The liquid phase may be mixed with liquefied fuel or sprayed into the headspace of the cryotank. A gas phase may be present in the headspace.

[0009] In some embodiments, the liquid vapor splitter is configured to provide a gas phase to the heat exchanger to provide additional cooling duty to the first flow of liquefied fuel from the pump. Additionally, the cryotank may be configured to provide a gas phase of the liquefied fuel from the headspace of the cryotank to the heat exchanger to provide additional cooling duty to the first flow of liquefied fuel from the pump. The system may further include at least one or both of a refrigeration unit and a backup power unit coupled to the heat exchanger. The refrigeration unit is configured to receive the gas or vapor phase from the heat exchanger and provide cooling duty to a facility such as a data center. The backup power unit is configured to receive the gas or vapor phase from the heat exchanger and generate electrical power. The backup power unit includes one or more fuel cells or combustion engines for generating electricity.

[0010] In some embodiments, the system may further include a refueling station comprising a dispenser configured to receive a second stream of liquefied fuel from the cryotank and dispense it in the form of gaseous or liquid fuel to a receiving fuel tank, such as an on-board fuel tank for a vehicle.

[0011] In another aspect, the present disclosure provides a method. The method includes providing liquefied fuel stored in a cryotank and pumping a first stream of liquefied fuel from the cryotank through a pump fluidly coupled to the cryotank while compressing the first stream of liquefied fuel to a high pressure. The method further includes cooling the first stream of liquefied fuel from the pump through a heat exchanger, which may be coupled with a cooler gas stream from the system (either headspace gas or vapor gas after the splitter), and expanding the first stream of liquefied fuel from the heat exchanger through an expansion valve into a multiphase stream. The cooling process may be substantially isobaric. The multiphase stream includes a liquid phase and a vapor phase and has a temperature lower than the initial temperature of the first stream from the cryotank. The method further includes separating the liquid and vapor phases in the multiphase stream through a liquid vapor splitter fluidly coupled to the expansion valve and returning the liquid phase from the liquid vapor splitter to the cryotank.

[0012] In some embodiments, the liquefied fuel includes or is hydrogen. The pump comprises one or more submerged liquid pumps disposed within the cryotank. The method can further include isentropically expanding the first flow of liquefied fuel from the heat exchanger through an expander turbine coupled to the heat exchanger and an expansion valve. The expansion valve, in some embodiments, is a Joule-Thomson valve.

[0013] In some embodiments, the liquid phase is returned to the cryotank through an interlock chamber fluidly coupled to the cryotank, and may be fed into the liquid phase in the cryotank or sprayed into the gas phase in the headspace of the cryotank in a top-fill process.

[0014] In some embodiments, the method further includes providing a vapor phase from the liquid vapor splitter to a heat exchanger to provide additional cooling duty to the first flow of liquefied fuel from the pump. Additionally, the method may further include providing a vapor phase of liquefied fuel from the headspace of the cryotank to the heat exchanger to provide additional cooling duty to the first flow of liquefied fuel from the pump. The method may further include at least one of: using the vapor or gas phase from the heat exchanger to provide cooling capacity from a refrigeration unit coupled to the heat exchanger to equipment requiring it; and using the gas or gas phase from the heat exchanger to generate power in a backup power unit. In some embodiments, the power is generated via one or more fuel cells in the backup power unit. The power from the backup power unit may be supplied to a data center or a pump. The refrigeration unit provides cooling capacity to an equipment or environment requiring cooling, such as a data center.

[0015] The method may further include providing a second stream of liquefied fuel from the cryotank to a refueling station comprising a dispenser and dispensing it in the form of gaseous or liquid fuel to a receiving fuel tank, for example, an on-board fuel tank in a vehicle.

[0016] The systems and methods provided in the present disclosure provide many of the advantages described herein. For example, in some embodiments, the present disclosure provides a system for hydrogen storage and refueling. The system in the present disclosure minimizes or eliminates losses of liquefied fuels, such as hydrogen, or eliminates hydrogen boil-off losses. Hydrogen gas or vapor from liquefied fuels in storage tanks can be used, for example, to provide backup power for pumps and can also be used, for example, to provide cooling capacity for data centers.

[0017] BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not necessarily to scale. On the contrary, dimensions of various structures have been arbitrarily increased or decreased for clarity. Like reference numerals refer to like features throughout the specification and drawings.

[0018] FIG. 1 is a block diagram illustrating a first exemplary system and flow paths for liquids, vapors, and supercritical fluids, according to some embodiments.

[0019] FIG. 2 is a temperature-entropy (specific entropy) diagram (ie, TS diagram) illustrating one example of an exemplary state condition in the exemplary system of FIG.

[0020] FIG. 3 is a block diagram illustrating a second exemplary system and flow paths for liquid, vapor, and supercritical fluids, according to some embodiments.

[0021] FIG. 4 shows the effect of headspace flow on the liquid fraction after Joule-Thomson (JT) expansion and cooling efficiency.

[0022] FIG. 5 is a TS diagram illustrating an example of an exemplary state condition in the example system of FIG.

[0023] FIG. 6 shows the effect of headspace flow on the liquid fraction after Joule-Thomson (JT) expansion and cooling efficiency at pump discharge pressure of 900 bar.

[0024] FIG. 7 is a block diagram illustrating a third exemplary system integrating boil-off management with downstream power generation using hydrogen from a cryotank, according to some embodiments.

[0025] FIG. 8 is a block diagram illustrating a fourth exemplary system integrating boil-off management, downstream power generation, and a refrigeration unit providing cooling duty, according to some embodiments.

[0026] FIG. 9 is a block diagram illustrating a fifth exemplary system including a refueling station, according to some embodiments.

[0027] FIG. 10 shows the liquid level in the cryotank, the hydrogen mass flow rate, and the headspace pressure in the cryotank during an exemplary refueling operation of a liquid hydrogen refueling station (LHRS).

[0028] Figure 11A is a flowchart illustrating an exemplary method according to some embodiments. Figures 11B and 11C are flowcharts illustrating some steps that may be included in the exemplary method of Figure 11A.

[0029] FIG. 12 shows a thermodynamic refrigerant subcooler (TCS) proposed for a launch pad subcooling system reported in the prior art.

[0030] (Detailed explanation) This description of exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are to be considered part of the entire written description. As used herein, relative terms such as "lower," "upper," "horizontal," "vertical," "upper," "lower," "upper," "bottom," and derivatives thereof (e.g., "horizontal," "bottom," "top," etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the devices be constructed or operated in a particular orientation. Terms relating to attachments, couplings, and the like, such as "connected" and "interconnected," unless expressly stated otherwise, refer to a relationship in which structures are fixed or attached to one another, both directly or indirectly through intervening structures, and through movable or rigid attachments or relationships.

[0031] For purposes of the following description, it is to be understood that the embodiments described below may assume alternative variations and embodiments, and that the specific articles, compositions, and / or processes described herein are illustrative and should not be considered limiting.

[0032] In this disclosure, the singular forms "a," "an," and "the" include plural references, and reference to a specific numerical value includes at least that particular value unless the context clearly dictates otherwise. When values ​​are expressed as approximations by use of the antecedent "about," it is understood that the particular value forms another embodiment. As used herein, "about X" (where X is a numerical value) preferably refers to ±10% of the recited value. For example, the phrase "about 8" preferably refers to a value between 7.2 and 8.8, inclusive. Where present, all temperature ranges are inclusive and combinable. For example, if a temperature range of "1 to 5" is provided, the temperature range should be interpreted as including ranges such as "1 to 4," "1 to 3," "1 to 2," "1 to 2 and 4 to 5," "1 to 3 and 5," "2 to 5," etc. Additionally, when a list of options is provided in the affirmative, such list may be interpreted to mean that any of the options may be excluded, for example, by a negative limitation in the claims. For example, if a range of "1 to 5" is recited, the recited range may be interpreted to include situations in which any of 1, 2, 3, 4, or 5 is negatively excluded; thus, the recitation of "1 to 5" may be interpreted as "1 and 3 through 5, but not including 2," or simply as "not including 2," and any components, elements, attributes, or steps that are positively recited herein are intended, regardless of whether such components, elements, attributes, or steps are listed as alternatives or whether they are listed by themselves.

[0033] Unless otherwise specified, the term "substantially" as used herein, such as "substantially the same," is understood to encompass parameters with an appropriate range of variation, for example, a variation of ±10% or ±15% of the parameter. In some embodiments, the range of variation is within ±10%.

[0034] Unless otherwise specified, liquefied fuels such as hydrogen are stored in storage tanks and pumped using a pump in liquid form. It can be dispensed as a gaseous or liquid fuel to a receiving tank within the vehicle. In this disclosure, the terms "refueling" and "fuel supply" are used interchangeably.

[0035] As used herein, when an element or component is described as being "connected," "coupled," "coupled," or "in contact" with another element or component, it may be directly connected to, directly coupled to, or in direct contact with the particular element or component, or intervening elements or components may be connected to, coupled to, or in contact with the particular element or component. When an element or component is referred to as being "directly connected," "directly coupled," "directly coupled," or "in direct contact with" another element, there are no intervening elements or components present.

[0036] As used herein, the terms "thermally coupled to" or "thermally coupled with" should be understood to mean that components are coupled directly or through intervening components such that heat can be transferred between the components, and that the components may be in direct contact with each other or that the intervening components may be in contact with the components. As used herein, the terms "fluidly coupled to" or "fluidly coupled with" should be understood to mean that the components are connected with pipes or lines and configured to have a flow of gas or liquid through the components. As used herein, the terms "electronically connected" or "electrically connected" should be understood to encompass electrical connections using wired or wireless connections.

[0037] The term "ambient temperature" as used herein is understood as the temperature under ambient conditions, for example room temperature between 20 and 22°C.

[0038] Fuels such as liquefied gases or liquid hydrogen are stored in cryogenic tanks. Heat leaks into these tanks vaporize the liquid, creating "boil-off" vapor and increasing the headspace gas pressure within the tank. Over time, the increased pressure within the tank creates a need to vent the gaseous hydrogen in the headspace to keep the cryotank below its pressure limit. As an alternative to venting, the boil-off problem can be solved by introducing a cooling duty into the tank to offset the heat leak.

[0039] The goal of cryogenic liquid hydrogen storage is zero boil-off, which minimizes or eliminates the loss of hydrogen as a gas from the cryogenic tank, resulting in improved operational efficiency.

[0040] Options for large-scale storage of hydrogen are outlined in J. Andersson, et al., "Large-scale storage of Hydrogen," International Journal of Hydrogen Energy 44 (2019): 11901-11919. Vented boil-off gas can be injected into the later stages of the liquefaction cycle to avoid its net loss from the system. However, the storage cryotank must be in close proximity to the large-scale liquefaction facility, and measures must be taken to gravimetrically collect the vented boil-off gas and deliver it to the liquefaction system.

[0041] As described in WU Notardonato, et al., "Zero boil-off methods for large-scale liquid hydrogen tanks using integrated refrigeration and storage," IOP Conference Series: Materials Science and Engineering, 278(1), 2017, an integrated refrigeration and storage (IRAS) system was used to remove energy from the liquid hydrogen tank and control the propulsion system. Heat leakage into the tank was removed by a helium-based cryocooler with a heat exchanger inserted into the tank. One cryocooler was the Linde LR1620 cryocooler, a Brayton cycle unit using a closed-loop helium refrigeration system. However, this approach faces many challenges, including temperature and pressure control of the integrated system during zero boil-off operation, challenges in manufacturing cryotanks with embedded heat exchangers, and energy consumption of the helium cryocooler, including during cycling, to meet transient cooling duty requirements.

[0042] reported using a cryogenic loop heat pipe to remove the amount of vapor generated from a storage tank and transport it to a cryogenic cooler where it is condensed back into a liquid and returned to the tank. See DR Zakar et al., "Zero Boil-Off Vehicle Storage Cryogenic Loop Heat Pipe for Use in Unmanned Aerial Vehicles," 15th International Energy Transition Technology Conference, 2017. The heat pipe system requires a cryocooler to re-liquefy the vapor extracted from the tank headspace.

[0043] However, systems using cryocoolers can provide cooling duty at temperatures below 30 K using expansion cycles. Existing cryocoolers are complex and require multiple stages. Alternative cryocoolers based on magnetocaloric processing are still in the development stage, awaiting material and engineering breakthroughs for large-scale operation. Additionally, when cryocoolers are used, there are also limitations on the size of the cryocooler system. While multiple systems can be installed in parallel, this presents challenges to scalability due to complexity, energy use, and capital costs.

[0044] A thermodynamic cryogenic subcooler (TCS) concept has been proposed for launch pad subcooling systems. See S. Mustafi, et al. (2009, September), "Subcooling cryogenic propellants for long duration space exploration," AIAA SPACE 2009 Conference & Exposition (2009). In the theoretical isobaric cooling process, liquid hydrogen is isenthalpically expanded through a Joule-Thomson valve using a heat exchanger to subcool liquid hydrogen circulated from the cryotank. Hydrogen from the expanded stream is not returned to the tank.

[0045] However, in such TCS concepts, the degree of cooling is limited by the starting pressure in the cryotank and the final pressure after expansion. The expanded hydrogen must be compressed for use outside the tank system; for example, a four-stage compressor is required. None of the expanded hydrogen is returned to the cryotank. This results in a potential drop in pressure that must be offset by cold helium pressurized gas added to prevent the tank from collapsing.

[0046] The possibility of compressing the liquid flow from the cryotank before isenthalpic expansion is not considered.

[0047] The present disclosure provides systems and methods with boil-off management for the storage of liquefied gas or fuel, for example, the liquefied fuel includes or is hydrogen, and the system is for storing and / or using liquid hydrogen.

[0048] In some embodiments, the present disclosure provides a boil-off management system that offsets at least a portion of heat leaks to a cryotank-containing liquid hydrogen using a compression-expansion cycle to generate a liquid hydrogen stream having a temperature lower than that of the liquid hydrogen in the tank. The compression-expansion cycle includes a liquid hydrogen stream extracted from the cryotank, a liquid hydrogen pump for compressing the liquid stream, a heat exchanger for cooling the compressed liquid hydrogen, an expander for producing saturated liquid hydrogen at a temperature lower than that of the initial liquid stream, and a return mechanism for delivering liquid hydrogen cooled to a temperature lower than that of the liquid hydrogen originally extracted from the cryotank. The system optionally includes a power generation system that generates electricity using hydrogen, the power generation system being powered by a portion of the boil-off gas and optionally providing electricity to operate the pump. The present disclosure also provides systems and methods for refueling while also providing backup power and cooling capacity. For example, the system is a hydrogen refueling station. Both the backup power and cooling capacity are supplied to a site or facility in need thereof, such as a data center.

[0049] In Figures 1, 3, and 7-9, like items are indicated by like reference numerals, and for brevity, the description of the structures given above with reference to the preceding figures will not be repeated. Figures 2, 4, 5-6, and 10 show example TS diagrams and characteristics associated with the systems shown in Figures 1, 3, and 7-9. The method described in Figures 11A-11C will be described with reference to the exemplary structures described in Figures 1, 3, and 7-9. In Figures 1, 3, and 7-9, numbers within circles represent fluid flows and different flows. The same flow at different stages may be labeled using different numbers.

[0050] 1 , an exemplary system 100 includes a cryotank 20, a pump 40, a heat exchanger 60, an expansion valve 80, and a liquid vapor splitter 90. The system may further include an expander turbine 70. The cryotank 20 is configured to store a liquefied fuel 14 therein.

[0051] The cryotank 20 may be an insulated tank suitable for storing a liquefied fuel 12, such as liquid hydrogen, at low temperatures and pressures. In some embodiments, the liquefied fuel 14 includes or is hydrogen. The cryotank 20 may include a headspace 22 in which a vapor phase 16 (boil-off) of the liquefied fuel 14 may reside.

[0052] The pump 40 is fluidly coupled to the cryotank 20 and configured to provide or pump the first stream 1 of liquefied fuel 14 from the cryotank 20 while compressing the first stream 1 of liquefied fuel 14 to a high pressure. The pump 40 comprises one or more submerged liquid pumps disposed within the cryotank 20 and configured to compress and increase the pressure of the pumped liquefied fuel stream. The liquefied fuel stream (labeled 2) discharged from the pump 40 may be in a supercritical state.

[0053] Heat exchanger 60 is coupled to pump 40 and configured to provide cooling duty to liquefied fuel stream 2 from pump 40. The cooled stream is labeled 3 and may be in a supercritical state.

[0054] Expander turbine 70 is coupled to heat exchanger 60 and expansion valve 80. Expander turbine 70 is configured to isentropically expand liquefied fuel stream 3 from heat exchanger 60 while producing an outlet stream (labeled 4) at a lower temperature.

[0055] Expansion valve 80 is configured to expand the liquefied fuel stream from heat exchanger 60 or expander turbine 70 into a multiphase stream 5 including a liquid phase 7 and a vapor phase 6. The expansion valve, in some embodiments, is a Joule-Thomson (JT) valve. The liquid is forced through a JT valve or plug, reducing its temperature. Multiphase stream 5 is a mixed-phase liquid-vapor stream and has a lower temperature than the initial temperature of first stream 1 from cryotank 20.

[0056] The liquid vapor splitter 90 is fluidly coupled to the expansion valve 80 and configured to separate the liquid phase 7 and the vapor phase 6 in the multiphase flow 5. The liquid phase 7 is configured to be returned into the cryotank 20. Such returned liquid phase 7 provides a cooling duty to the cryotank 20 to minimize or eliminate boil-off of the liquefied fuel, such as liquid hydrogen.

[0057] The exemplary system 100 can further include an interlock chamber 94 fluidly coupled to the cryotank 20 and configured to return the liquid phase 7 to the cryotank 20. The interlock chamber 94 can include at least two ports that can be opened in sequence to allow a lower-pressure liquid to be pumped into the cryotank 20 at a higher pressure. The interlock chamber 94 can also include a check valve coupled to reduce the pressure in the cryotank 20 to be lower than the pressure of the cooled liquid (liquid phase 7). The liquid phase 7 can be mixed with the liquefied fuel 14 or sprayed into the headspace 22 of the cryotank 20 to mix with the gas phase 16 that may be present in the headspace 22.

[0058] The vapor phase 6 from the liquid vapor splitter 90 may be provided to a heat exchanger 60 to provide additional cooling duty to the compressed stream 2 of liquefied fuel 14 from the pump 40. The vapor phase 6 after passing through the heat exchanger 60 is labeled as gas stream 8.

[0059] As an example, an exemplary system 100 is designed with a submerged liquid pump for isentropic compression to increase the pressure of liquid hydrogen to 450 bar. Figure 2 is a TS diagram showing the thermodynamic state of hydrogen as it travels through the exemplary system 100 with boil-off management. In the TS diagram, lines parallel to the horizontal axis represent isothermal processing, and lines parallel to the vertical axis represent isentropic processing.

[0060] 2, the hydrogen processes and states include isentropic compression by pump 40 (hydrogen state 1 to 2), cooling by heat exchanger 60 (2 to 3), liquid expansion by expander turbine 70 (3 to 4), expansion to multiphase flow by expansion valve 80, such as a JT valve (4 to 5), and separation by splitter 90 (5 to 6 and 7). The hydrogen stream in states 2 and 3 is supercritical (SC). The change of vapor phase from 6 to 8 in heat exchanger 60 provides additional cooling in the cooling process (2 to 3).

[0061] The flow conditions at each point are listed in Table 1.

[0062] [Table 1]

[0063] In the thermodynamic cycle of Example 1, hydrogen liquid stream 1 is extracted from cryotank 20. In this example, the tank pressure is 5 bar, the temperature is 27 K, and stream 1 is a saturated liquid. A pump isentropically compresses the liquid hydrogen stream to 450 bar while the temperature is 47.4 K. Hydrogen stream 2 is supercritical. This supercritical hydrogen stream is heat exchanged with a cooler gas (vapor phase 6) to cool its temperature to 43.0 K. The cooled supercritical stream 3 is isentropically expanded through a turbine from 70 to 30 bar (a) to avoid two-phase flow at the turbine outlet. The temperature is 27.3 K. Stream 4 is expanded using a Joule-Thompson valve to produce multiphase saturated liquid-saturated vapor stream 5. In this example, multiphase stream 5 is at 1 bar and 20.3 K. Based on the enthalpy balance, the stream contains 77.6% liquid and 22.4% vapor. After separation, it becomes saturated liquid 7 and saturated vapor 6, both of which are at 1 bar(a). Vapor 6 is used to cool the supercritical hydrogen stream exiting the pump (mentioned above). The vapor stream cools the supercritical hydrogen stream from 47 K to 43 K. The vapor stream then exits the boil-off control system at 38.2 K. The vapor stream has lost 44.04 kJ of energy.

[0064] Liquid stream 7 at 20 K and 1 bar is returned to the tank. An interlock chamber is used to manage the pressure differential to return the liquid to the tank at 5 bar. The net cooling load delivered to the water tank is 68 kJ / kg H2. Using a measured power draw of 720 kJ / kg H2 pump (0.2 kWh / kg), the energy efficiency was 9.5%. This energy efficiency compares favorably to cryocooler systems that can draw kilowatts of power to provide cooling power on the order of watts over a similar temperature range, corresponding to efficiencies of less than 1%.

[0065] 3, an exemplary system 200 is shown. The components for exemplary system 200 are the same as those of exemplary system 100, except that cryotank 20 may be configured to provide the vapor phase 16 of liquefied fuel 14 from headspace 22 of the cryotank 20 to heat exchanger 60 to provide additional cooling duty to the first stream of liquefied fuel from pump 40 (i.e., stream 2).

[0066] As an example, an exemplary system 200 is designed for 450 bar using a P200H pump with headspace gas 9 (which becomes stream 9 after vapor 16 exits cryotank 20) ​​as an additional coolant. Cooling of the compressed gas is achieved using a mixture of headspace vapor 9 (5 bar in Example 2) saturated at cryotank pressure and JT flash gas (stream 6, saturated vapor at 1 bar in Example 2). The resulting mixture is stream 10 at 1 bar and 21.1 K. Ideally, a two-step process would be thermodynamically more efficient with less exergy destruction, with the warmer headspace gas (stream 9) first cooling the pump discharge (stream 2), and then the cooler JT flash gas (stream 6) further cooling the pump discharge. However, such a two-step process would be more complex and potentially more costly. Instead, the mixed stream 10 is used to cool the pump discharge.

[0067] As shown in Figure 4, varying amounts of headspace gas relative to JT flash gas can achieve various amounts of cooling efficiency. Figure 4 shows the effect of headspace flow on the liquid fraction after JT expansion and cooling efficiency. The headspace mass flow rate is the ratio of the pump discharge flow rate, and the cooling efficiency is the cooling power of the JT flash liquid at 1 bar relative to the pump energy consumption (0.2 kWh / kg). The abbreviations "liq" and "eff" in Figure 4 stand for "liquid" and "efficiency," respectively. Higher headspace gas flows increase the liquid fraction and cooling efficiency, but the return decreases as the liquid fraction approaches 100%. The best return on investment is 0.5 kg of headspace gas per kg of pump discharge flow, as it is at the steepest part of the curve. The TS diagram using this condition is shown in Figure 5, which shows the thermodynamic state of the flow in Example 2. The flow conditions are also listed in Table 2.

[0068] [Table 2]

[0069] As in Example 3, exemplary system 200 is also designed using isentropic pumping up to 900 bar with headspace cooling. Example 2 demonstrates that using headspace gas improves cooling efficiency and, therefore, headspace gas flow is not a special case. In Example 3, exemplary system 200 is used while stream 2 is compressed to 900 bar.

[0070] Figure 6 shows the effect of headspace flow on the liquid fraction after JT expansion and cooling efficiency at a pump discharge pressure of 900 bar. Pumping at 900 bar uses a pumping energy of 0.4 kWh / kg.

[0071] In Example 3, pump 40 is nominally isentropic, and stream 2 is at a higher temperature than in Example 1 due to the higher pump outlet pressure. In addition, the cooling duty is provided using a combination of headspace gas (stream 9) and saturated vapor (stream 6) produced after JT expansion. Compared to Example 1, compressing stream 2 to a higher pressure results in a higher liquid fraction after JT expansion (0.836 vs. 0.776) even without headspace gas cooling. Although the cooling duty increases, the electrical energy required for pumping is doubled at 450 bar - 0.4 kWh / kg. Furthermore, the small amount of vapor after JT expansion means that the majority of the cooling of stream 2 is achieved using JT flash gas (stream 6).

[0072] Table 3 shows the flows and thermodynamic conditions for Example 3 with a headspace gas flow of 0.2 kg per kg of pump discharge (Stream 2) flow.

[0073] [Table 3]

[0074] Referring to FIG. 7 , an exemplary system 300 is shown. The exemplary system 300 is the same as the exemplary system 200, except that the exemplary system 300 further includes a backup power unit 120. The exemplary system 300 illustrates integration of a boil-off management system with a downstream power generation unit. The backup power unit receives gas 8 from the heat exchanger 60 and is configured to generate electrical power. The backup power unit 120 includes one or more fuel cells or combustion engines for generating electrical power. The exhaust 11 may be water vapor. Optionally, one or more combustion engines can be used within the backup power unit 120 to generate electricity through a thermal cycle. Suitable examples of combustion engines include, but are not limited to, reciprocating engines, gas or microturbines, and hydrogen turbines.

[0075] As Example 4, an exemplary system 300 is also designed with a 450 bar pump discharge and power generation using a polymer electrolyte membrane (PEM) fuel cell or cells. This embodiment includes integrating a boil-off management system with subsequent power generation using H from the cryotank 20. This example demonstrates the use of a backup power unit 120 with a PEM fuel cell to generate power, where 20 kWh / kg of H vapor is supplied to the PEM fuel cell. Here, a portion of the power generated by the PEM system is used to power the pump 40, corresponding to 0.2 kWh / kg H drawn from the cryotank 20.

[0076] Referring to FIG. 8 , an exemplary system 400 is shown. The exemplary system 400 is the same as the exemplary system 200, except that the exemplary system 400 further includes a backup power unit 120 and a refrigeration unit 122 coupled to the heat exchanger 60. The exemplary system 400 illustrates the integration of a boil-off management system with downstream power generation and refrigeration units for data center cooling. The refrigeration unit 122 is configured to receive the gas 8 from the heat exchanger 60 and provide cooling duty to a facility 124, such as a data center. The backup power unit 120 can be coupled to the refrigeration unit 122 and receive the hydrogen gas from the heat exchanger 60 and / or the refrigeration unit 122 and generate electrical power. The backup power unit 120 includes one or more fuel cells or combustion engines for generating electricity.

[0077] An exemplary system 400 is also designed as Example 5. For illustrative purposes, the pump discharge pressure is set to 450 bar and the ratio of headspace gas mass flow rate to pump discharge flow rate is set to 0.5. In this case, the boil-off management system is integrated with subsequent production using H from cryotank 20, with additional cooling duty extracted from the vapor H stream for use in production (e.g., from Gas 8 to Gas 12). Optional integration with cooling loads within a facility 124, such as a data center, is shown in FIG. 8.

[0078] Example 5 illustrates the use of a heat exchanger 60 to extract cooling load from a vapor H stream after it has been exchanged with a compressed liquid H stream, but before it enters a backup power unit 120, such as a PEM fuel cell power generation unit. The cooling load is used to provide cooling duty to a data center. The cooling load can also be used in any process requiring a cold sink with a temperature below 0°C. In Example 5, the cryotank is at 5 bar, the exit temperature of the vapor from the heat exchanger is 33.8K, and the cooling potential in raising the stream to -20°C is approximately 1.0 kWh.th / kg H.

[0079] Referring to FIG. 9 , an exemplary system 500 is shown. The exemplary system 500 is similar to the exemplary system 100, except that the exemplary system 500 further includes a refueling station 140 including a dispenser. The exemplary system 500 illustrates the integration of a hydrogen refueling station for a fuel cell vehicle with a boil-off management system. The refueling station 140 is configured to receive a second stream 13 of liquefied fuel 14 from the cryotank 20 and dispense it in the form of gaseous or liquid fuel to a receiving fuel tank, such as an on-board fuel tank for the vehicle. The refueling station 140 may also include an additional heat exchanger to convert the liquefied fuel 14 to the gaseous fuel that is dispensed from the cryotank 20.

[0080] As Example 6, an exemplary system 500 is also designed, in which the boil-off management system is integrated with a hydrogen refueling station (HRS) for fuel cell vehicles. The refueling station 140 uses compressed liquid H from pump 40 to ultimately deliver a pre-cooled compressed gas charge or compressed liquid hydrogen to an on-board H storage tank for the hydrogen fuel cell vehicle.

[0081] In addition to integration with the HRS, a feature of Example 6 is the return of the chilled liquid. Rather than using an interlock, the chilled liquid 7 is stored in a chamber 94 with a check valve. The pump 40 is also used to supply hydrogen for refueling. Under some conditions (e.g., high flow rate operation), the pressure in the cryotank 20 drops. During the HRS operating cycle, the pressure in the cryotank 20 increases when the system does not dispense fuel due to boiloff associated with static heat leaks into the cryotank 20. During HRS operation, fuel removal can cause a pressure drop. In this example, if the pressure in the cryotank drops below the pressure of the chilled liquid 7, it can flow through the check valve into the cryotank 20.

[0082] Figure 10 shows the headspace pressure in the cryotank during an LHRS fueling operation. During the back-to-back fueling of three buses, the pressure drops from 6.3 bar to 5.5 bar. In Figure 10, the liquid level in the cryotank, the hydrogen mass flow rate (kg / hr), and the headspace pressure in the cryotank (bar (g)) are shown in the top, middle, and bottom panels, respectively. The curves were generated from the test system database. Each of the three back-to-back fills lasted approximately 12 minutes, dispensed approximately 40 kg of hydrogen, and reduced the cryotank headspace pressure by more than 0.5 bar. However, during the idle time between fills, the headspace pressure recovered by approximately 0.2 bar as the cryotank two-phase system equilibrated and static heat leaks creeped in. The results in Figure 10 provide evidence of the pressure drop described above, which can be difficult to achieve in a pump, and also support a dynamic method of returning the cooler liquid stream to the cryotank by pumping out the warmer liquid hydrogen through a re-fueling operation.

[0083] In the present system and method, the refueling process may be performed periodically, cooling duty may be generated periodically from the refueling station, and backup power may be generated intermittently.

[0084] Referring to FIG. 11A, the present disclosure also provides an exemplary method 600 as described above and generally below.

[0085] In step 602, liquefied fuel 14 is provided and stored in a cryotank 20. In some embodiments, liquefied fuel 14 includes or is hydrogen.

[0086] In step 604, a first stream 1 of liquefied fuel is pumped from cryotank 20 and compressed to an increased pressure via pump 40 fluidly coupled to cryotank 20. Stream 1 and subsequent streams are referred to as the first stream. Pump 40 may comprise one or more submerged liquid pumps disposed inside cryotank 20.

[0087] In step 606, the first stream of liquefied fuel 14 from pump 40 (i.e., stream 2 at this stage) is cooled through a heat exchanger 60 coupled to pump 40. The cooling process may be substantially isobaric.

[0088] In step 610, the first stream of liquefied fuel 14 from heat exchanger 60 (i.e., stream 3 at this stage) is expanded through expansion valve 80 into multiphase stream 5, which in some embodiments is a Joule-Thomson valve. Multiphase stream 5 includes a liquid phase 7 and a vapor phase 6 and has a temperature lower than the initial temperature of the first stream from cryotank 20.

[0089] 11B, the exemplary method 600 may further include step 608 before step 610. In step 608, the first stream of liquefied fuel (i.e., stream 3) from the heat exchanger 60 is isentropically expanded through an expander turbine 70 coupled to the heat exchanger and an expansion valve.

[0090] Referring back to FIG. 11A, in step 612 , the liquid phase 7 and vapor phase 6 in the multiphase stream 5 are separated through a liquid-vapor splitter 90 fluidly coupled to an expansion valve 80 .

[0091] In step 614, the liquid phase 7 is returned from the liquid vapor splitter 90 to the cryotank 20. In some embodiments, the liquid phase 7 is returned to the cryotank 20 through an interlock chamber 94 fluidly coupled to the cryotank. The liquid phase 7 can be supplied to the liquid phase in the cryotank. Step 614 can include step 616 of FIG. 11B. In step 616, the liquid phase 7 can be sprayed into the vapor phase in the headspace 22 of the cryotank 20 in a top-fill process.

[0092] In some embodiments, in step 604, the flow rate of the LH2 stream is up to 280 kg / h using a single pump (e.g., using a P200H pump base). If multiple pumps are used, each pump has a flow capacity of up to 280 kg / h. The pressure of the hydrogen stream after pumping is up to approximately 90 MPa. After step 606, the temperature of the high-pressure stream after cooling can be limited at the lower end by the temperature of the liquid hydrogen extracted from the cryotank. The upper end can be the theoretical temperature achieved by isentropic compression with respect to the pump outlet pressure (point 2 on the TS diagram, e.g., Figure 5, in the absence of cooling of stream 2). After step 610 for expansion, the fraction of liquid stream 6 can range from 0.5 to approximately 0.999. Liquid stream 7 can have a temperature in the range of approximately 20 K as a lower limit and a temperature slightly lower than the temperature of the liquid stream extracted from the cryotank as an upper limit. Gas from the headspace for auxiliary cooling, together with saturated steam after JT expansion, can have a flow rate ranging from 0 kg / kg.pumping to 10 kg / kg.pumping, and is pumped as the ratio of headspace gas flow rate to pump discharge flow rate.

[0093] 11C and 7-8, the exemplary method 600 may further include one or more of steps 622, 624, 626, 628, and 630. In step 622, the vapor phase 6 from the liquid vapor splitter 90 is fed to a heat exchanger 60 to provide additional cooling duty to the first stream 2 of liquefied fuel from the pump 40.

[0094] In step 624, the vapor phase 16 of the liquefied fuel from the headspace 22 of the cryotank 20 is fed to the heat exchanger 60 to provide additional cooling duty to the first stream 2 of the liquefied fuel from the pump 40.

[0095] An example may also include one or both of steps 626 and 628. In step 626, cooling is provided to equipment requiring it from a refrigeration unit 122 coupled to the heat exchanger by using gas 8 from the heat exchanger 60. The refrigeration unit 122 provides cooling to the equipment or environment requiring cooling. For example, the cooling from the refrigeration unit 122 may be used to cool a data center. Backup power and cooling may also be provided to other equipment, such as a distribution center (e.g., for HVAC or refrigeration).

[0096] In step 628, power is generated in the backup power unit 120 by using the gas 8 from the heat exchanger 60. In some embodiments, the power is generated through one or more fuel cells in the backup power unit 120. Optionally, one or more combustion engines can be used in the backup power unit 120 to generate electricity through a thermal cycle. Suitable examples of combustion engines include, but are not limited to, reciprocating engines, gas turbines or microturbines, and hydrogen turbines. The power from the backup power unit 120 may be supplied to the data center or the pump 40.

[0097] Referring to Figures 11C and 9, in step 630, a second stream 13 of liquefied fuel is supplied from the cryotank to a refueling station equipped with a dispenser and then dispensed in the form of gaseous or liquid fuel to a receiving fuel tank, for example, an on-board fuel tank in a vehicle.

[0098] Referring to Figure 12, a system 150 proposed by Mustafi et al. is shown for comparison. Cryogenic propellant, such as hydrogen (TC1), is extracted from tank 21. A portion passes through JT valve 81 and expands into a two-phase mixture (TC2) at lower pressure and temperature. Via pump 41, most of the liquid hydrogen is pumped as a single-phase liquid into the shell of concentric tube heat exchanger 61. The two-phase hydrogen (TC2) passes through the central tube of the concentric tube heat exchanger, extracting heat from the single-phase hydrogen. The two-phase hydrogen is completely vaporized and discharged to the flare stack (TC3) through compressor 71; the expanded hydrogen is not returned to the tank. A four-stage compressor is required, which is identified as a large and heavy piece of equipment. Helium gas must be added to prevent the tank from collapsing.

[0099] In comparison, the system provided in the present disclosure has at least the differences described herein. For example, pump 40 is used to increase the pressure of the liquid hydrogen prior to isenthalpic expansion. A portion of the expanded hydrogen (e.g., liquid phase 7) is returned to cryotank 20. A pressure equalization mechanism is used to return the liquid to cryotank 20. The application of helium to maintain tank integrity is also eliminated. The need for compressor 71 as described above is also eliminated.

[0100] The present system and method address energy consumption, system complexity, and control challenges by using a single-stage compression process to provide refrigeration duty to liquid H2 stored in a cryotank 20. The system operates in a unique manner. For example, a liquid hydrogen stream is extracted from liquid hydrogen stored in the cryotank 20. Liquid stream 1 is compressed to at least 100 bar using a submerged liquid pump 40, which is nominally at the same entropy as the liquid hydrogen in the cryotank 20, in a theoretically isotropic compression process. The compressed (liquid / supercritical) stream 2 is cooled by heat exchange at near-constant pressure with gas 6 from the JT expansion. Optionally, vapor 9 from the headspace 22 of the cryotank 20 is used to provide additional refrigeration duty. Neither vapor 9 nor gas 6 from the cryotank headspace is returned to the tank after heat exchange; they can be combined. The cooled (supercritical) stream is first expanded (isentropically) using an expansion turbine to an intermediate pressure (e.g., 30 bar) to avoid two-phase formation, followed by a Joule-Thompson (JT) throttling process to expand the two-phase mixture below the pressure at which the liquid is extracted from the cryotank, producing saturated gas 6 and liquid stream 7 at a temperature lower than that of the liquid in the cryotank 20. The cooled liquid stream 7 is returned to the cryotank, thereby introducing a net cooling load to the tank. Mechanisms for delivering the liquid include the use of an interlock chamber 94 or reducing the pressure of the cryotank 20 via a re-fueling operation that draws H2 from the vessel at a rate that reduces the net pressure to that of the expanded liquid stream. As described herein, after providing cooling duty, the hydrogen vapor or gas can also be used to generate electricity.

[0101] Further optimization is possible by varying the pump discharge pressure, the end temperature of the isobaric cooling process, the end pressure of the turbine expansion process, and the final pressure of the JT expansion process. The pump discharge pressure, the cooling capacity of the turbine expansion process, and the end temperature of the isobaric cooling process are interconnected and present optimization opportunities. For example, Figure 4 shows the results of a simulation of compression using a submerged liquid pump operating on saturated liquid hydrogen compressed to different outlet pressures at different inlet temperature and pressure conditions. The outlet temperature is a function of the inlet conditions and outlet pressure and is constrained by thermodynamic limits imposed by an ideal isothermal or isentropic compression process. In other words, the lower temperature limit is the inlet temperature, and the upper temperature limit is calculated using a thermodynamic relationship that assumes an isentropic compression process using hydrogen properties.

[0102] The systems described herein can also be integrated with upstream liquefaction systems, where the boil-off management system is integrated with cryotanks used to store the products of the liquefaction process. The upstream components of the system can include a liquefier and a hydrogen production unit, such as an electrolyzer, for converting water to hydrogen and oxygen. At least one or both of the liquefaction unit and the hydrogen production unit can be powered by wind or solar power.

[0103] The devices described herein can also be integrated with a distribution grid where LH2 from the storage vessels is transported to one or more of the following: hydrogen refueling stations for heavy duty vehicles (HDVs), light duty vehicles (LDVs), ground vehicle transport such as rail, industrial sites where H2 is used as part of a steel manufacturing process, industrial sites where H2 is used as part of a metal manufacturing process, and industrial sites where H2 is used in combustion processes to provide power and heat.

[0104] Submerged liquid pumps can be used to compress a liquid flow to achieve a final temperature and pressure that are limited by the isothermal and isentropic limits. Existing technology uses external pumps and requires cooling (which introduces additional boil-off losses). However, submerged pumps enable practical implementation of the compression-expansion cycle described herein. For example, Figure 4 shows the response curve of a submerged liquid pump approaching the isentropic limit.

[0105] The cooled liquid hydrogen is returned to the cryotank, thus reducing or minimizing boil-off losses. The return mechanism involves an interlock chamber, similar to an airlock; liquid enters, equalizes with the cryotank, and the chamber is closed and returned to low pressure, allowing more liquid to enter. The return mechanism can use dynamic operating processes within the cryotank; a pump is used to dispense H2 for vehicle refueling fast enough to reduce the pressure within the cryotank. The cooled liquid is returned to the cryotank as the cryotank pressure drops due to H2 dispensing. The pressure then rises again as thermal leaks cause boil-off.

[0106] The present system and method also provide additional benefits, such as: For example, such a simplified process uses a submerged liquid pump and a single stage loop, and does not require a cryocooler.

[0107] The system and method offer energy efficiency. Providing cooling duty at temperatures below 30 K is a difficult and energy-intensive process. Assuming a pump energy consumption of 0.2 kWh.e / kg, a cooling duty of 68 kJ / kg is generated (see Example 1). That cooling load condenses approximately 0.15 kg of hydrogen into a liquid (the hydrogen latent heat of condensation is 454 kJ / kg). In other words, to produce 1 kg of liquid, an input of 1.3 kWh.e / kg is required. For reference, a full liquefaction method theoretically requires 3.9 kWh.e / kg, and in practice, only about 12 kWh / kg to produce liquid H2. However, most of this energy is used to cool the H2 to its boiling point and provide energy for the para-ortho transition. Because liquid hydrogen is nominally 100% para-H2, this method avoids the energy penalty associated with the ortho-para transition, which can be significant when cooling gaseous H2 during the liquefaction process.

[0108] The system and method also provide controllability. Cooling duty can be delivered by operating a submersible pump and controlled by the pump flow rate. Because the pump is submerged and in thermal equilibrium with the liquid H2 in the tank, there is no boil-off associated with starting the pump.

[0109] The system and method also provide scalability. Submersible pumps have been demonstrated at a 285 kg / hr gravimetric scale. For example purposes, a 240 kg / hr pump base was used in the system described herein. This means that a single pump can achieve kW-scale cooling duty. Multiple pumps can be used to increase the cooling load for large cryotanks.

[0110] The system and method are also compatible with liquid hydrogen fueling stations. Integration with liquid hydrogen fueling stations that use a liquid pump to deliver fuel to vehicles is one mechanism that allows for the return of cooled liquid from the boil-off management system to the cryotank. Additionally, the use of a liquid tank to deliver fluid increases the utilization of the liquid pump for value-added activities beyond boil-off management. This integration amplifies the benefits of a simplified design and also improves the economic value of the system by increasing utilization of the liquid pump.

[0111] The systems and methods provided in the present disclosure provide many of the advantages described herein. For example, in some embodiments, the present disclosure provides a system for hydrogen storage and refueling. The system in the present disclosure minimizes or eliminates losses of liquefied fuels, such as hydrogen, or eliminates hydrogen boil-off losses. Hydrogen gas or vapor from liquefied fuels in storage tanks can be used, for example, to provide backup power for pumps and can also be used, for example, to provide cooling capacity for data centers.

[0112] In some embodiments, the systems provided herein may further include one or more control units or central units (not shown in FIGS. 1, 3, and 7-9) for controlling the method steps and fuel quantities at each step or through each component. The control units may be electronically connected to associated components in the system. The control units may include one or more processors and at least one tangible, non-transitory, machine-readable medium encoded with one or more programs executed by the one or more processors. The control units are configured to coordinate with each component to control operations such as managing boil-off during storage, refueling vehicles, cooling data centers, and providing backup power.

[0113] The methods and systems described herein may be implemented, at least in part, in the form of computer-implemented processes and apparatuses for performing those processes. The disclosed methods may also be embodied, at least in part, in the form of a tangible, non-transitory, machine-readable storage medium encoded with computer program code. The medium may include, for example, RAM, ROM, CD-ROM, DVD-ROM, BD-ROM, hard disk drive, flash memory, or any other non-transitory, machine-readable storage medium, or any combination of these media. When the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for performing the method. The methods may also be embodied, at least in part, in the form of a computer into which the computer program code is loaded and / or executed, such that the computer becomes an apparatus for performing the method. When implemented on a general-purpose processor, the computer program code segments configure the processor to create specific logic circuits. The methods may alternatively be embodied, at least in part, in a digital signal processor formed with an application-specific integrated circuit for performing the method. The computer or control unit may be remotely controlled using a cloud-based system.

[0114] While the present subject matter has been described with respect to exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variations and embodiments that may occur to those skilled in the art. [Brief explanation of the drawings]

[0115] [Figure 1] FIG. 1 is a block diagram illustrating a first exemplary system and flow paths for liquids, vapors, and supercritical fluids, according to some embodiments. [Figure 2] FIG. 2 is a temperature-entropy (specific entropy) diagram (ie, TS diagram) illustrating one example of an exemplary state condition in the exemplary system of FIG. [Figure 3]FIG. 3 is a block diagram illustrating a second exemplary system and flow paths for liquid, vapor, and supercritical fluids, according to some embodiments. [Figure 4] FIG. 4 shows the effect of headspace flow on the liquid fraction after Joule-Thomson (JT) expansion and cooling efficiency. [Figure 5] FIG. 5 is a TS diagram illustrating an example of an exemplary state condition in the example system of FIG. [Figure 6] FIG. 6 shows the effect of headspace flow on the liquid fraction after Joule-Thomson (JT) expansion and cooling efficiency at pump discharge pressure of 900 bar. [Figure 7] FIG. 7 is a block diagram illustrating a third exemplary system integrating boil-off management with downstream power generation using hydrogen from a cryotank, according to some embodiments. [Figure 8] FIG. 8 is a block diagram illustrating a fourth exemplary system integrating boil-off management, downstream power generation, and a refrigeration unit providing cooling duty, according to some embodiments. [Figure 9] FIG. 9 is a block diagram illustrating a fifth exemplary system including a refueling station, according to some embodiments. [Figure 10] FIG. 10 shows the liquid level in the cryotank, the hydrogen mass flow rate, and the headspace pressure in the cryotank during an exemplary refueling operation of a liquid hydrogen refueling station (LHRS). [Figure 11A] FIG. 11A is a flowchart illustrating an exemplary method according to some embodiments. [Figure 11B] 11B is a flowchart illustrating some steps that may be included in the exemplary method of FIG. 11A. [Figure 11C] 11C is a flowchart illustrating some steps that may be included in the exemplary method of FIG. 11A. [Figure 12] FIG. 12 shows a thermodynamic refrigerant subcooler (TCS) proposed for a launch pad subcooling system reported in the prior art.

Claims

1. a cryotank configured to store a liquefied fuel therein; a pump fluidly coupled to the cryotank and configured to provide the first flow of liquefied fuel from the cryotank while compressing the first flow of liquefied fuel to an increased pressure; a heat exchanger coupled to the pump and configured to provide a cooling duty to the first flow of the liquefied fuel from the pump; an expansion valve configured to expand the first flow of the liquefied fuel from the heat exchanger into a multiphase flow including a liquid phase and a vapor phase, the multiphase flow having a temperature that is lower than an initial temperature of the first flow from the cryotank; a liquid vapor splitter fluidly coupled to the expansion valve and configured to separate the liquid phase and the gas phase in the multiphase flow, the liquid phase being configured to be returned to the cryotank.

2. The system of claim 1 , wherein the liquefied fuel comprises hydrogen.

3. The system of claim 1 , wherein the pump comprises one or more submerged liquid pumps disposed within the cryotank.

4. 10. The system of claim 1, further comprising an expander turbine coupled to the heat exchanger and the expansion valve and configured to isentropically expand the first flow of the liquefied fuel from the heat exchanger.

5. The system of claim 1 , wherein the expansion valve is a Joule-Thomson valve.

6. The system of claim 1 , further comprising an interlock chamber fluidly coupled to the cryotank and configured to return the liquid phase to the cryotank.

7. The system of claim 1 , wherein the liquid vapor splitter is configured to provide the vapor phase to the heat exchanger to provide additional cooling duty to the first flow of the liquefied fuel from the pump.

8. 8. The system of claim 7, wherein the cryotank is configured to provide a vapor phase of the liquefied fuel from a headspace of the cryotank to the heat exchanger to provide additional cooling duty to the first flow of the liquefied fuel from the pump.

9. a refrigeration unit coupled to the heat exchanger, the refrigeration unit configured to receive gas from the heat exchanger and provide a cooling duty to a facility; a backup power unit configured to receive gas from the heat exchanger and generate electrical power.

10. The system of claim 9 , wherein the backup power unit includes one or more fuel cells for generating the electrical power.

11. 10. The system of claim 1, further comprising a refueling station comprising a dispenser configured to receive the second stream of liquefied fuel from the cryotank and dispense it into a receiving fuel tank in the form of gaseous or liquid fuel.

12. providing a liquefied fuel to be stored within a cryotank; pumping the first stream of liquefied fuel out of the cryotank through a pump fluidly coupled to the cryotank while compressing the first stream of liquefied fuel to an increased pressure; cooling the first flow of the liquefied fuel from the pump through a heat exchanger coupled to the pump; expanding the first stream of the liquefied fuel from the heat exchanger through an expansion valve into a multiphase stream, the multiphase stream including a liquid phase and a vapor phase and having a temperature lower than the initial temperature of the first stream from the cryotank; separating the liquid and vapor phases in the multiphase flow through a liquid-vapor splitter fluidly coupled to the expansion valve; returning the liquid phase from the liquid vapor splitter to the cryotank.

13. The method of claim 12 , wherein the liquefied fuel comprises hydrogen.

14. The method of claim 12 , wherein the pump comprises one or more submerged liquid pumps disposed within the cryotank.

15. 13. The method of claim 12, further comprising isentropically expanding the first stream of the liquefied fuel from the heat exchanger through an expander turbine coupled to the heat exchanger and the expansion valve.

16. The method of claim 12, wherein the expansion valve is a Joule-Thomson valve.

17. 13. The method of claim 12, wherein the liquid phase is returned to the cryotank through an interlock chamber fluidly coupled to the cryotank.

18. 13. The method of claim 12, wherein the step of returning the liquid phase to the cryotank comprises spraying the liquid phase into a gas phase in a headspace of the cryotank in a top-fill process.

19. 13. The method of claim 12, further comprising providing the vapor phase from the liquid vapor splitter to the heat exchanger to provide additional cooling duty to the first flow of the liquefied fuel from the pump.

20. 20. The method of claim 19, further comprising providing a vapor phase of the liquefied fuel from a headspace of the cryotank to the heat exchanger to provide additional cooling duty to the first flow of the liquefied fuel from the pump.

21. utilizing the gas from the heat exchanger to provide cooling capacity to a facility requiring it from a refrigeration unit connected to the heat exchanger; and utilizing gas from the heat exchanger to generate electrical power with a backup power unit.

22. 22. The method of claim 21, wherein the power is generated via one or more fuel cells in the backup power unit.

23. the power is supplied from the backup power unit to the data center or the pump; 22. The method of claim 21, wherein the cooling capacity from the refrigeration unit is used to cool the data center.

24. delivering a second flow of the liquefied fuel from the cryotank to a refueling station including a dispenser; 13. The method of claim 12, further comprising the step of: dispensing the liquefied fuel into a receiving fuel tank in the form of a gaseous fuel or a liquid fuel.

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