Hydrogen refueling system and method for uses in different climates

Abstract

A system such as a fueling station and a method for fueling hydrogen to vehicles are disclosed. The system includes a cryotank configured to store a liquid hydrogen, a cryo pump to provide a hydrogen stream with an elevated pressure, a first heat exchanger to accept a first portion of the hydrogen stream and exchange energy with ambient air to increase temperature, a by-pass line to accept a second portion of the hydrogen stream and combine it with the first portion of the hydrogen stream to provide a combined stream, a second heat exchanger to optionally provide heating to the combined stream in cold climates, and a dispenser to a dispense the hydrogen fuel of a desired pressure, a desired temperature, and a predetermined flow rate to a vehicle having an onboard storage system. The ratio of the compression energy input (Ws) to thermal management energy input (Qth) is greater than one.

Description

HYDROGEN REFUELING SYSTEM AND METHOD FOR USES IN DIFFERENTCLIMATESPRIORITY CLAIM AND CROSS-REFERENCE

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 654,503, filed May 31, 2024, which application is expressly incorporated by reference herein in its entirety.FIELD OF THE INVENTION

[0002] The disclosure relates to systems and methods for storing, dispensing, and using a liquefied gas generally. More particularly, the disclosed subject matter relates to a system and a method for storing, dispensing, and using liquefied gas such as liquid hydrogen for transportation applications.BACKGROUND

[0003] Many motor vehicles are currently powered by internal combustion engines with fossil fuels. Due to limited supply and adverse environmental effects associated with burning petroleum-derived fuels, vehicles are now being developed that are powered by alternative environmentally friendly fuels like hydrogen. Fuel cells can be used to produce electric power for motor vehicles by electrochemically reacting hydrogen fuel with an oxidant such as air. Other hydrogen-powered vehicles can be powered by combustion of hydrogen. Fueling or refueling hydrogen to fuel cell vehicles (FCV) and other hydrogen- powered vehicles presents different challenges from adding petroleum-based fuels like gasoline into a vehicle.

[0004] In addition, outdoor environments vary significantly in different seasons and different geographical locations. For example, temperature variations pose tremendous challenges to hydrogen refueling systems and vehicles operated with hydrogen.

[0005] U.S. Patent No. 11,009,185 discloses a system with ambient vaporization for a liquid hydrogen refueling station, where a slip stream, also known as a bypass stream or a partial stream, upstream of the ambient vaporizer is used to provide the final temperature control before the high-pressure hydrogen gas is dispensed into a fuel cell vehicle, using a fluid bypass method. Such a fluid bypass method is also described in U.S. Patent No. 10,961,109. The method described in U.S. Patent No. 11,009,185 avoids using electricalenergy input for vaporization, but in cold climate, the discharge temperature from the vaporizer could be less than -40°C, even without any bypass flow which could further decrease the mixed stream temperature.

[0006] Others such as Linde as described in U.S. Patent No. 9,253,912 not only use electrical energy for vaporization, but also add complicated heat capture and storage systems involving additional heat transfer fluid loops, pumps, and storage vessels, making the system complicated, unreliable and prone to maintenance problems.

[0007] It is desirable to have hydrogen refueling stations and related vehicles with capabilities of operation with a high efficiency in both hot and cold climates or weathers.SUMMARY OF THE INVENTION

[0008] The present disclosure provides a system and a method for storing, dispensing, and using liquefied gas such as hydrogen, for applications, for example, for transportation applications. The present disclosure provides a system such as a fueling station and a method for fueling hydrogen to vehicles, which may be fuel cell-based or internal combustion engine vehicles.

[0009] In accordance with some embodiments, such a system for refueling hydrogen to vehicles comprises a cryotank configured to store a liquid hydrogen, a cryo pump fluidly connected with the cryotank, a first heat exchanger fluidly connected to the cryo pump, a bypass line fluidly connected to the cryo pump and parallel to the first heat exchanger, and a second heat exchanger.

[0010] The cryotank is configured to withdraw a portion of the liquid hydrogen from the cryotank, increase a pressure of the portion of the liquid hydrogen to a first predetermined pressure, and provide a hydrogen stream at the first predetermined pressure and a first predetermined temperature.

[0011] The first heat exchanger is configured to accept a first portion of the hydrogen stream from the cryo pump, exchange energy with ambient air at an ambient temperature, and increase a temperature of the first portion of the hydrogen stream to equal to or below the ambient temperature.

[0012] The by-pass line is configured to accept a second portion of the hydrogen stream from the cryo pump to bypass the first heat exchanger and connect with a downstream of the first heat exchanger so as to combine the second portion of the hydrogen stream withthe first portion of the hydrogen stream to provide a combined stream. A second proportion of the hydrogen stream is controlled by a control valve.

[0013] The second heat exchanger is fluidly connected with the first heat exchanger and the by-pass line. The second heat exchanger is configured to accept the combined stream and provide heating when the ambient temperature is lower than a threshold and provide a hydrogen fuel at a second predetermined pressure and a second predetermined temperature.

[0014] The system further comprises a dispenser fluidly connected with the second heat exchanger and configured to accept the hydrogen fuel and dispense the hydrogen fuel at a predetermined flow rate to a vehicle having an onboard storage system.

[0015] In the system, the ratio of the compression energy input (Ws) to the thermal management energy input (Qth) is greater than one.

[0016] In some embodiments, the compression energy input (Ws) is defined by enthalpy of the hydrogen stream from the cryo pump (he) minus enthalpy of the liquid hydrogen from the cryotank (ht). The thermal management energy input not from the ambient environment is energy required for vaporization and cooling of the combined hydrogen and the hydrogen fuel needed before the hydrogen fuel is dispensed. Energy input from the ambient environment is freely available thus excluded. However, the energy input to devices such as fans and blowers that make the energy input available from the ambient environment is a form of energy input to the thermal management effort, although such amount is relatively small.

[0017] In some embodiments, the ratio of the compression energy input to thermal management energy input is greater than two, for example, greater than three, greater than four. For example, in some embodiments, such a ratio is in a range of from 1 to 10, 2 to 9, 2 to 8, or any other suitable ranges.

[0018] In some embodiments, the first heat exchanger is an open-air ambient vaporizer where the heat transfer surfaces are exposed to the ambient air and air movement is due to density differences at different temperatures under gravity. This type of heat exchanger is also known as a natural convection, or natural draft, ambient vaporizer. In some embodiments, the first heat exchanger is an enclosed forced air vaporizer with induced draft or force draft fan arrangement. In this type of vaporizer, an enclosure surrounds the heat transfer surfaces, and air movement is through fans or blowers. If the pressure inside the enclosure is higher than the ambient pressure, it is a forced draft arrangement. If the pressure inside the enclosure is lower than the ambient pressure, it is an induced draft arrangement.

[0019] In some embodiments, the second heat exchanger is a direct electrical heater without an intermediate heat transfer fluid medium.

[0020] In some embodiments, for example, in warm or hot climates or environments, the second heat exchanger provides no heating when the ambient temperature is higher than the threshold, and the combined stream is fed to the dispenser directly.

[0021] The onboard storage system in a vehicle is selected from a liquid hydrogen onboard storage system, a cryo-compressed H2 system, a H35 fuel onboard storage system, and a H70 fuel onboard storage system in some embodiments.

[0022] The system may further comprise a controller, which is connected electronically with and configured to individually control one or more of the cryo pump, the first heat exchanger, the control valve, and the second heat exchanger, and the dispenser. In some embodiments, the controller is configured to control a proportion of the bypass around the first heat exchanger, and / or control the second heat exchanger.

[0023] In another aspect, the present disclosure provides a method of making the system as described herein. Such a method comprises steps of providing components, and assembling the components together to provide the pump or the system.

[0024] In another aspect, the present disclosure provides a method of using the system of any of the preceding claims. Such a method comprises providing the first predetermined pressure, the first predetermined temperature, the second predetermined pressure, the second predetermined temperature, and the predetermined flow rate. A proportion of the first portion and the second portion of the hydrogen stream from the cryo pump is determined based on these parameters. Such a method further comprises providing the first portion and the second portion of the hydrogen stream based on the proportion, and determining whether and how much the second heat exchanger needs to provide heating and providing heating when needed.

[0025] In some embodiments, the method further comprises determining a type of fuel onboard storage system of a vehicle; and fueling a type of fuel corresponding to the type of fuel onboard storage system to the vehicle. The type of fuel onboard storage system may be selected from a H35 fuel onboard storage system, and a H70 fuel onboard storage system.

[0026] Other features of the system and the methods as described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Like reference numerals denote like features throughout specification and drawings.

[0028] FIG. 1 illustrates an existing hydrogen refueling station using liquid hydrogen.

[0029] FIG. 2 illustrates an exemplary system such as a hydrogen refueling station in accordance with some embodiments.

[0030] FIG. 3 illustrates an exemplary electrical heater design in the exemplary system of FIG. 2 in accordance with some embodiments.DETAILED DESCRIPTION

[0031] This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

[0032] For purposes of the description hereinafter, it is to be understood that the embodiments described below may assume alternative variations and embodiments. It is also to be understood that the specific articles, compositions, and / or processes described herein are exemplary and should not be considered as limiting.

[0033] In the present disclosure the singular forms “a,” “an,” and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. When values are expressed asapproximations, by use of the antecedent “about,” it will be 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, inclusive. For example, the phrase “about 8” preferably refers to a value of 7.2 to 8.8, inclusive. Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, “2-5”, and the like. In addition, when a list of alternatives is positively provided, such listing can be interpreted to mean that any of the alternatives may be excluded, e.g., by a negative limitation in the claims. For example, when a range of “1 to 5” is recited, the recited range may be construed as including situations whereby any of 1, 2, 3, 4, or 5 are negatively excluded; thus, a recitation of “1 to 5” may be construed as “1 and 3-5, but not 2”, or simply “wherein 2 is not included.” It is intended that any component, element, attribute, or step that is positively recited herein may be explicitly excluded in the claims, whether such components, elements, attributes, or steps are listed as alternatives or whether they are recited in isolation.

[0034] The word “tanks,” “cryotank,” and “vessel” may be used interchangeably. The terms “refueling station” and “fueling station” may be used interchangeably.

[0035] Hydrogen storage includes at least four types of storages including cryogenic hydrogen storage (liquid hydrogen storage), subcooled liquid hydrogen (SLH2), cryocompressed hydrogen (CCH2) storage, and compressed hydrogen storage in an order of increasing pressure. The term “cryogenic hydrogen storage” refers to liquid hydrogen being stored at a cryogenic temperature and a low pressure. One of disadvantages of cryogenic hydrogen storage is the inevitable boil-off losses. The term “subcooled liquid hydrogen (SLH2)” refers to liquid hydrogen stored at a higher pressure, for example, in a range of from 1 MPa to 2 MPa (e.g., 1.6 MPa). The term “compressed hydrogen storage” refers to compressed hydrogen gas stored under ambient temperature but at a high pressure, for example, between 300 bar (30 MPa) and 1,000 bar (100 MPa). The term “cryo-compressed hydrogen (ccH2) storage” refers to hydrogen being stored at a lower pressure, for example, between 300 bar (30 MPa) and 500 bar (50 MPa), but at low, cryogenic temperatures. The term “cryo-compressed hydrogen (ccH2)” used herein refers to hydrogen stored or dispensed at a pressure equal to or less than 450 bar (45 MPa).

[0036] Hydrogen dispensing described herein includes at least H35 and H70. The term “H35” means that hydrogen is dispensed at a nominal pressure of 350 bar(g) (35 MPa). The term “H70” means that hydrogen is dispensed at a nominal pressure of 700 bar(g) (70MPa). Hydrogen may be dispensed at any other pressure coded as “Hn,” where n refers to the pressure in MPa.

[0037] For clarity, cold climate in this disclosure means outdoor ambient temperatures would cause the fluid outlet temperature from a vaporizer using ambient air as the heat source to be less than -40 °C. The actual outdoor ambient temperature might be higher than -40 °C for such conditions to occur because there is a non-zero temperature difference between the heating source and the fluid to be heated in the vaporizer. Such low temperatures are too cold for dispensing per industry fueling standards. Such “cold climate” condition can occur in cold weather locations or a cold environment. Such a cold condition may occur in certain months, days, or hours in a particular day.

[0038] In FIGS. 1- 3, like items are indicated by like reference numerals, and for brevity, descriptions of the structure, provided above with reference to the preceding figures, are not repeated. The methods described herein are described with reference to the exemplary structure described in FIGS. 2-3.

[0039] One of the objectives in the present disclosure is to provide a system such as a refueling station for fueling hydrogen to vehicles.

[0040] Hydrogen is an energy carrier that can be used as a fuel for transportation. In transportation, hydrogen can be used to power vehicles with fuel cell drive systems that run on hydrogen. Options for storing the fuel on-board include: (1) as a compressed gas at 35 or 70 MPa; (2) as a cryocompressed fluid at certain pressure; or (3) as liquid hydrogen. The storage pressure for such a cryocompressed fluid is between 300 bar to 500 bar, and temperature between 30 K to 80 K. In all three cases, the storage and delivery of hydrogen in liquid form at the station can offer advantages in vehicle refueling. For compressed gas, the use of LH2 facilitates pressurization and pre-cooling of the gas so as to reduce energy demand of the fueling station equipment, allow for faster refueling, and allow for extended vehicle throughput (back-to-back fueling). For cryocompressed and LH2 onboard storage modes, the use of LH2 simplifies the refueling equipment, and allows rapid vehicle refueling.

[0041] Thermal management is a major challenge for hydrogen refueling stations using delivered liquid hydrogen. The refueling system must be able to operate in both hot and cold climates. There are two complementary loads - one for heating and one for cooling. But these cannot be readily or directly compensated due to differences in timing, quantitative thermal load, and actual temperatures for heat exchange. As a result, these loads are addressed with separate thermal management systems. For the heating load needed to vaporize liquid hydrogen, electrical heating is used. This increases power demand chargeand energy consumption. For the cooling load needed to adjust gas temperature before dispensing, a refrigeration system is used. Newer generation designs have started using ambient air vaporizers for heating and the cold energy from liquid hydrogen for refrigeration, but the system suffers from not being able to meet the desired dispensing temperature in cold climate where the ambient vaporizer outlet temperature is below the desired dispensing temperature.

[0042] In the present disclosure, a system with a unique design and a method are provided to thermally integrate these loads, eliminating the need for separate thermal management systems, and ensuring that the system is capable of operation in all climates, weathers, or other conditions with temperature variations. A simple solution provided in the present disclosure allows the refueling station to operate in all climates or any other outdoor conditions without incurring a large electrical heating load.

[0043] The efficiency of energy use is measured by the ratio of compression energy input to thermal management energy input. The system and the method provided in the present disclosure are highly energy efficient because this ratio is significantly higher than one.

[0044] In hydrogen refueling stations using liquid hydrogen storage, vaporization is a significant heat load. For example, a cryo pump with a flow rate of 240 kg / hr (4 kg / min) would need 238 kW for vaporization, assuming isentropic compression from a cryotank pressure of 2 barg (0.2 MPa) to a pump discharge pressure of 960 barg (96 MPa), and an ambient temperature of 300K. In existing technologies, vaporization of liquid hydrogen is provided by electrical heating. For example, a flowsheet of a refueling station currently in operation is illustrated in FIG. 1.

[0045] The reasons cited by the industry for using electrical energy to vaporize liquid hydrogen rather than using an ambient air vaporizer include the steam cloud from an ambient vaporizer being perceived as a public nuisance, and footprint considerations. Public education and a visual barrier can address the steam cloud issue which affects only public access HRSs. For behind-the-fence stations and truck stops outside the urban setting, neither footprint nor steam cloud are problems. Instead, energy efficiency and power demand are key performance metrics.

[0046] The other issue with ambient vaporizers is ice buildup due to moisture from the air which degrades heat transfer performance. The use of electrical heating for vaporization would increase the station power demand cost (related to kW) as well as theenergy consumption by approximately 1.0 kWh / kg hydrogen dispensed, as calculated by Q / m, where Q is vaporization duty in kW, m is pump flow rate in kg / hr.

[0047] In the flowsheet shown in FIG. 1, hydraulic oil is being used to heat up the warm tank fluid. Such a waste heat integration would reduce the electrical demand, but a typical hydraulic system has electrical-to-hydraulic efficiency of approximately 70%, leaving approximately 30% of the total compression power demand as waste heat. Continue with the example with a flow rate of 240 kg / hr above. Raising the liquid hydrogen pressure from cryotank pressure of 2 barg (0.2 MPa) to 960 barg (96 MPa) at that flow rate would need 77 kW which means 110 kW total electrical demand, leaving 33 kW as waste heat. This level is short of the 238 kW vaporization duty required. In real applications, compression is never fully isentropic so there is more waste heat. But this order of magnitude analysis still holds. Therefore, current methods for heat integration still require significant electrical energy input into heaters to support vaporization, and the heat from the hydraulic system is mainly for hydraulic oil temperature control rather than heat input for the vaporization process.

[0048] In addition to liquid hydrogen vaporization, hydrogen refueling stations will need to cool gas streams at the dispenser to offset the heat of compression experienced inside the onboard compressed hydrogen storage system (CHSS) during refueling. The process may require cooling the stream to as low as -40°C at the nozzle. In some existing designs, the cooling is achieved using chillers, which themselves require electrical power to operate and can also result in operating delays when the demand for cooling exceeds the cooling duty of the refrigeration system, especially in hot and humid environments. FIG. 1 also shows an intermediate cold tank that can reduce the net electricity requirement by heat integrating the vaporization thermal load and boil-off gas cold capture to provide on-demand cooling duty.

[0049] The system in FIG. 1 requires separate thermal reservoirs to provide controllability for the system. The two separate thermal management loops are complex, costly to build, operate and maintain.

[0050] The system disclosed in US 11,009,185 does not use electrical vaporization and the additional thermal management loops. It further discloses a direct fill approach where no cascade storage is used. This arrangement simplifies the refueling station substantially but requires a high flow rate pump and a responsive control system to manage the dispensing temperature to within SAE J2601 standards. Such pumps and controls are available today. However, in cold climate, the fluid temperature out of the ambient vaporizer is too cold to mix with the cryogenic bypass stream to produce a desirable dispensing temperature. The system fails to meet the dispensing temperature requirement and stops.

[0051] The system and the method provided in the present disclosure solve the problem of fueling at all climate conditions without incurring large electrical heating loads or creating complicated thermal management loops.

[0052] The objectives of the present disclosure are to solve several problems. Liquid hydrogen can be vaporized with ambient air, but the existing technologies utilize electrical heating, which increases power demand charge and energy consumption. This is the first problem. Another problem is controlling the fluid temperature at the dispenser nozzle to meet SAE J2601 requirements in all climate conditions.

[0053] The first problem is solved with ambient air vaporizers with a cold bypass. The second problem is solved by adding a specially designed heat exchanger just upstream of the dispenser nozzle to provide a small amount of heating so that the final dispensed fluid meets the J2601 temperature requirement. This heat exchanger can be of any kind but preferably it is an electrically heated unit without the complication of an intermediate heat transfer fluid. Such a unit operates only in conditions where the ambient vaporizer output is below the required dispenser nozzle temperature requirement but before the ambient temperature itself drops below -40°C when J2601 protocol mandates to cease fueling. Such conditions are not frequent even in cold climate environment; therefore, the use of electrical heat is limited. Furthermore, the amount of power demand when it is in use is small relative to the overall station requirements.

[0054] The system and method disclosed herein have many advantages. For example, the system and the method reduce a total power demand charge of a system such as a hydrogen refueling station by as much as one half, and energy consumption cost by up to 1.0 kWh / kg hydrogen dispensed and allow the refueling station to operate even in cold environment, where the ambient vaporizer outlet temperature is below the dispenser nozzle temperature requirement. The power demand is a separate ongoing cost, and a large power demand can complicate station permitting and cause long delays especially when additional electrical transformer capacity is needed in a power substation. Energy consumption in kWh is an ongoing cost, and the ability to operate the refueling station in all climate environments is nonnegotiable.

[0055] The invention disclosed herein aims to vaporize liquid hydrogen with minimum electrical heating and allow the station to operate in all climate environments.

[0056] Referring to FIG. 2, an exemplary system such as an exemplary liquid hydrogen refueling station according to the invention in this disclosure is shown. A cryotank 10 stores liquid hydrogen. A cryo pump 20 withdraws liquid from the cryotank and increasesits pressure to a desired level. The high-pressure hydrogen enters an ambient air vaporizer 30, which can be open air natural draft, or fan-driven induced draft or forced draft. The ambient air vaporizer 30 is referred as the first heat exchanger. A cold bypass line 32 with a control valve 34 takes a portion of the pump discharge stream around the vaporizer to meet the desired temperature required by the dispenser nozzle. Although a fanned-air design requires a fan thus a piece of moving equipment and some electrical energy input, the heat transfer coefficient of a typical fanned unit can be 2 to 4 times higher than a natural draft vaporizer, thus significantly reducing the size of the vaporizer which lowers capital cost and reduces footprint requirements. Meanwhile, the fans need only a few kW power. The vaporized hydrogen, along with a side stream bypassed around the vaporizer, is then sent to the dispenser 50 where it is charged into the compressed hydrogen storage system (CHSS) in a vehicle 60 at the desired dispensing temperature, e.g., -40 °C, and with pressure and flow controls (not shown).

[0057] In a cold climate environment, the outlet temperature from the ambient air vaporizer, even without any fluid bypass, may be close to or lower than the desired dispensing temperature. In such conditions, the refueling system cannot meet the dispensing temperature requirement and has to shut down. However, a heat exchanger 40 can be used to bring the fluid temperature to the desired level. The heat exchanger 40 is referred as the second heat exchanger. A direct electrical heater can be used for this purpose. For example, heating wires can be wrapped around the outside diameter of high-pressure hydrogen tubing encased in external insulation so that energy is directed inward to the hydrogen inside the tubing.

[0058] Examples of electrical heater elements include, but are not limited to, the Cooperheat heating pads provided by Red-D-Arc, an Airgas Company; and the FLUENT heaters by Watlow Electric Manufacturing Company. The Cooperheat heating pads provided by Red-D-Arc comprise a nickel chrome wire heating element encased in a flexible ceramic insulator. Such heated pads can be wrapped around hydrogen tubing to provide heating.

[0059] The FLUENT heater by Watlow Electric Manufacturing Company is an inline heater in a cylindrical package. The gas being heated flows through an annulus between the heating core and the external pipe. Inside the heating core, electrical heating wires pass through a thin tube packed with magnesium oxide powder as an electrical insulator. Multiple such tubes may be used to provide the desired power output. These heating elements are encased in a thin tube to become the heating core. A thermocouple may be used to provide temperature control for the heater.

[0060] A direct electrical heater for hydrogen is considered incompatible in the existing technologies because of hydrogen embrittlement concerns. However, the small load and the operating temperature range for the heat exchanger 50, as illustrated in the examples to follow, do not lead to hydrogen embrittlement. It is nonobvious to incorporate such a device to achieve a special purpose for applications where the state of the art deems incompatible. Additionally, there is only one fluid stream at pressure so cross-stream leak or contamination is possible.

[0061] The power required per unit mass flow, or called a specific energy requirement, is dimensionally identical to enthalpy and for simplicity in discussion, enthalpy and power per unit mass flow appear in energy balance equations, as is customarily done in thermodynamics. For isentropic compression, the power required per unit mass flow, ws, from the cryo tank condition to the cryo pump discharge can be calculated using the equation: ws= he— ht, where heis enthalpy of the hydrogen stream at the pump discharge, htis enthalpy of the hydrogen stream at the cryo tank condition. In addition to compression, there is energy requirement for thermal management Qth, which includes vaporization and final cooling of the hydrogen stream before dispensing it to the vehicle. A high efficiency refueling station minimizes thermal management energy requirement Qth. On a per fill basis, the customary units for specific energy requirement are kWh / kg dispensed hydrogen.

[0062] The exemplary systems and methods provided herein are described using the following examples, which are for illustration only.

[0063] Example 1

[0064] For an H70 refueling station, the pump discharge pressure, which is the pressure downstream of the pump 20 (FIG. 2), is set at 960 barg (96 MPa). Assuming a cryotank condition of 2 barg (0.2 MPa) and saturated, the enthalpy of the saturated liquid htis 50.1 kJ / kg, the entropy is 2.09 kJ / kg / K, according to the REFPROP database. See NIST Reference Fluid Thermodynamic and Transport Properties - REFPROP, NIST Standard Reference Database 23, National Institute of Standards and Technology, US DOE, 2013. When this liquid is compressed isentropically to 960 barg (96 MPa), the discharge stream has enthalpy heat 1,191 kJ / kg, so the isentropic compression energy requirement is 1,141 kJ / kg, or 0.32 kWh / kg.

[0065] For comparison, if hydrogen gas at 233K (-40 °C) is compressed isentropically from 2 barg (0.2 MPa) to 960 barg (96 MPa) using the ideal gas law, specific energy 3.95 kWh / kg is required. If this gas is compressed from 0.2 MPa to 96 MPa from theambient temperature of 300 K (27°C) rather than the precooled temperature of -40°C, 5.1 kWh / kg is required. The discharge temperature, assuming ideal gas behavior and k = cp / cv= 1.4, would have been T = To p / po)1^-1= 300(961 / 3)°'286= 1,562 K or 1289 °C, which is completely unacceptable. Multi-stage compression with inter-stage cooling will have to be used for such gas compression.

[0066] Following isentropic compression of the liquid hydrogen to 960 barg (96 MPa), the stream is heated in a vaporizer to ambient condition of 300 K (27°C). Assuming no pressure drop in the vaporizer, the discharge stream enthalpy is 4,610 kJ / kg, therefore 3,419 kJ / kg or 0.95 kWh / kg is needed for this vaporization process. Furthermore, when this hydrogen is to be dispensed to vehicles at -40°C, the ending enthalpy is 3,603 kJ / kg, thus a refrigeration load of 1,007 kJ / kg (0.28 kWh / kg) is required. The total thermal management energy requirement is 1.23 kWh / kg, assuming the refrigeration system has a coefficient of performance (COP) of unity. If vaporization is achieved through ambient air heating, and the cooling duty is satisfied using the refrigeration in liquid hydrogen, no electrical or mechanical energy input is required for thermal management.

[0067] Although the cold bypass method can provide the desired dispensing temperature in any hot climate, the outlet temperature from the vaporizer can be lower than - 40°C in cold climate due to non-zero temperature approach in an ambient heat exchanger. That is, if the ambient temperature is -40°C, the ambient vaporizer outlet temperature would always be lower than -40°C because a nonzero temperature difference must exist between the stream providing the heating and the stream receiving the heating, a difference known as the temperature approach. In that case, any cold bypass flow would make the final fluid temperature even colder. Thus, the stream from the outlet of the vaporizer must be heated.

[0068] For example, if the outlet temperature from the vaporizer is -50°C, the stream must be heated to a minimum of -40°C for dispensing. The required heat input is 0.041 kWh / kg. For a hydrogen refueling station having a mass rate of 4 kg / min, that means the heating power required is 9.8 kW. A 10 kW heater would be sufficient. If the ambient temperature is below -40°C, the SAE J2601 protocol would require halting fueling operations. Therefore, the heater is only needed to provide a small boost in a limited temperature window to overcome the temperature approach in the vaporizer.

[0069] Referring to FIG. 3, an exemplary electrical heater 40 is illustrated. The heater 40 comprises a plurality of heating elements 41 connected via wires 43 to a power supply 42. The plurality of heating elements 41 may be connected in parallel or in series. Insome embodiments, the plurality of heating elements 41 are connected in parallel. These heating elements 41 are disposed inside an enclosure 47 where hydrogen inflow 44 enters from an inlet. After being heated, the hydrogen flows out of the heater as the heated outflow 45 from an outlet. The hydrogen flow path can be cross flow, counter flow, parallel flow or any combination thereof with respect to the heating element arrangement with the objective being maximum heat exchange to the hydrogen gas and optimal hardware arrangement.

[0070] Each of the plurality of the heating elements 41 may be straight, curved, zigzag, single path or multiple paths through the heater. Each element 41 comprises an electrical resistance wire encased or coated with a gas impermeable ceramic material to avoid any reaction with hydrogen. The heating element can also be enclosed in stainless steel tubing packed with a heat conducting but electrically insulating material such as magnesium oxide to eliminate any void space between the heating wire and the tubing and to facilitate heat transfer between the heating wire and the tubing wall. Furthermore, the tubing may have fins on the outside to enhance heat transfer with the hydrogen gas.

[0071] Because the outflow hydrogen temperature is targeted at -40 °C and the heating power is minimal, the design can provide the required heat input without causing the surface of the heating elements in contact with hydrogen to go over 300 °C where hydrogen embrittlement for chrome-nickel stainless steel alloys such as 304 or 316 stainless steel may start to experience hydrogen embrittlement under pressures up to 900 barg (90 MPa), as reported in Silfies, T., Dobis, J.D. and Nugent, M., “Looking behind the curtain of API RP941 high temperature hydrogen attack (HTHA) data,” Paper number 7516, Corrosion 2016 Conference and Expo, NACE International, 2016.

[0072] The isentropic compression energy requirement, or input, for this operation is 0.32 kWh / kg as described above. The only thermal management energy input is the electrical heater at 0.041 kWh / kg. The ratio of the compression energy input to thermal management energy requirement, or input, is 7.8. In reality, compression is not isentropic, and there are other small parasitic loads such as fans for the vaporizer, the ratio of compression energy to thermal management energy input would be less than 7.8 but is expected to be significantly more than one.

[0073] Example 2

[0074] For an H35 refueling station, the pump discharge pressure is set at 480 barg (48 MPa). Assuming a cryotank condition of 2 barg (0.2 MPa) and saturated, the enthalpy of the saturated liquid htis 50.1 kJ / kg, and the entropy is 2.09 kJ / kg / K. When this liquid iscompressed isentropically to 480 barg (48 MPa), the discharge stream has enthalpy heat 666 kJ / kg, so the isentropic compression energy requirement is 616 kJ / kg, or 0.17 kWh / kg.

[0075] Following isentropic compression to 480 barg (48 MPa), the stream is heated in a vaporizer to ambient condition of 300 K. Assuming no pressure drop in the vaporizer, the vaporizer discharge stream enthalpy is 4,248 kJ / kg, therefore 3,582 kJ / kg or 0.99 kWh / kg is needed for this vaporization process. Furthermore, when this hydrogen is to be dispensed to vehicles at -40°C, the ending enthalpy is 3,248 kJ / kg, thus a refrigeration load of 1,000 kJ / kg (0.28 kWh / kg) is required. The total thermal management energy requirement is 1.27 kWh / kg, assuming the refrigeration system has a coefficient of performance (COP) of unity. If vaporization is achieved through ambient air heating, and the cooling duty is satisfied using the refrigeration in liquid hydrogen, no electrical or mechanical energy input is required for thermal management.

[0076] Although the cold bypass method can provide the desired dispensing temperature in any hot climate, the outlet temperature from the vaporizer can be lower than - 40°C in cold climate due to non-zero temperature approach in an ambient heat exchanger. That is, if the ambient temperature is -40°C, the ambient vaporizer outlet temperature would always be lower than -40°C. In that case, any cold bypass flow would make the final fluid temperature even colder. Thus, the stream from the outlet of the vaporizer must be heated. For example, if the outlet temperature from the vaporizer is -50°C, the stream must be heated to a minimum of -40°C for dispensing. The required heat input is 0.041 kWh / kg. For a 4 kg / min station, that means the heating power required is 9.8 kW. A lOkW heater would be sufficient. If the ambient temperature is below -40°C, the SAE J2601 protocol would require halting fueling operations. Therefore, the heater is only needed to provide a small boost in a limited temperature window to overcome the temperature approach in the vaporizer.

[0077] The isentropic compression energy input for this operation is 0.17 kWh / kg. The only thermal management energy input is the electrical heater at 0.041 kWh / kg. The ratio of the compression energy input to thermal management energy input is 4.1. In reality, compression is not isentropic, and there are other small parasitic loads such as fans for the vaporizer. Assume a 70% pumping efficiency and a 10 kW forced draft fan motor for the ambient vaporizer as a parasitic load, the ratio of compression energy to thermal management energy input would be 5.4.

[0078] Table 1 summarizes the calculated results including energy requirements for compression, vaporization, and refrigeration.

[0079] Table 1.

[0080] The actual compression process is not isentropic. Cryo pumps have less than 100% volumetric efficiency and there are frictional and irreversibility losses in the process. Those with ordinary skills in the art would appreciate that the orders of magnitude of the compression, vaporization, refrigeration, and heating requirements are correctly reflected in the aforementioned examples. For pumping systems, it is desirable that most of the energy used is for pumping rather than for thermal management or parasitic functions. If vaporization is achieved through ambient air heating, and the cooling duty is satisfied using the refrigeration in liquid hydrogen, the thermal management energy requirement would be zero theoretically and the ratio of isentropic compression energy requirement to that of thermal management would be infinity. In real systems, inefficiencies and irreversibilities would result in a non-zero parasitic energy requirement. Assume a 70% pumping efficiency and a 10 kW forced draft fan motor for the ambient vaporizer as a parasitic load, the ratio of compression energy to thermal management energy input would be 2.9. In the system provided in the present disclosure, the direct electrical heat exchanger 40 (FIG. 2) without an intermediate heat transfer fluid medium to bring the fluid temperature to meet the J2601 requirements consumes negligible energy, but provides the needed control. The heat exchanger with electrical heating in accordance with some embodiments provides a solution significantly different from the existing technologies.

[0081] Industry is aware of the significant thermal management energy use in refueling stations, but struggles with the time shift and magnitude mismatch in cooling and heating needs, especially when a refueling station initiates a vehicle fill after a period of inactivity so that all components, including the gas in the hydrogen storage system, are warm. Thus, the state-of-the-art solution is to use electrical systems for their fast response with ahuge energy penalty and to use multiple heat transfer fluid loops for energy storage and release.

[0082] The system may further comprise a controller, which is connected electronically with and configured to individually control one of more of the cryo pump, the first heat exchanger, the control valve, and the second heat exchanger, and the dispenser. In some embodiments, the controller is configured to control a proportion of the bypass around the first heat exchanger, and / or control the second heat exchanger. The electronic connection may be made through wire or wirelessly, and may be controllable through cloud operations.

[0083] In another aspect, the present disclosure provides a method of making the system as described herein. Such a method comprises steps of providing components, and assembling the components together to provide the pump or the system.

[0084] In another aspect, the present disclosure provides a method of using the system of any of the preceding claims. Such a method comprises providing the first predetermined pressure, the first predetermined temperature, the second predetermined pressure, the second predetermined temperature, and the predetermined flow rate. A proportion of the first portion and the second portion of the hydrogen stream from the cryo pump is determined based on these parameters. Such a method further comprises providing the first portion and the second portion of the hydrogen stream based on the proportion, and determining whether and how much the second heat exchanger needs to provide heating and providing heating when needed.

[0085] In some embodiments, the method further comprises determining a type of fuel onboard storage system of a vehicle; and fueling a type of fuel corresponding to the type of fuel onboard storage system to the vehicle. The type of fuel onboard storage system may be selected from a H35 fuel onboard storage system and a H70 fuel onboard storage system.

[0086] The controller is used for controlling the steps of the method including selection of the device and the amount of the material flow in each step or going through each component, and controlling the heating step. The control unit(s) may be electronically connected with the related components in the system. The control unit may comprise one or more processors and at least one tangible, non-transitory machine readable medium encoded with one or more programs to be executed by the one or more processors. The control unit is configured to coordinate with each component so as to control the operation of each component and dispensing hydrogen in a suitable form to refuel fuel cell electric vehicles, monitoring safety, and so on.

[0087] The methods and system described herein may be at least partially embodied in the form of computer-implemented processes and apparatus for practicing those processes. The disclosed methods may also be at least partially embodied in the form of tangible, nontransient machine-readable storage media encoded with computer program code. The media may include, for example, RAMs, ROMs, CD-ROMs, DVD-ROMs, BD-ROMs, hard disk drives, flash memories, or any other non-transient machine-readable storage medium, or any combination of these mediums, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the method. The methods may also be at least partially embodied in the form of a computer into which computer program code is loaded and / or executed, such that the computer becomes an apparatus for practicing the methods. 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 at least partially embodied in a digital signal processor formed of application specific integrated circuits for performing the methods. The methods may partially or fully be performed through cloud operations as well.

[0088] The references described herein are incorporated herein by reference.

[0089] Although the subject matter has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art.

Claims

What is claimed is:

1. A system for refueling hydrogen to vehicles, comprising a cryotank configured to store a liquid hydrogen; a cryo pump fluidly connected with the cryotank and configured to withdraw a portion of the liquid hydrogen from the cryotank, increase a pressure of the portion of the liquid hydrogen to a first predetermined pressure, and provide a hydrogen stream at the first predetermined pressure and a first predetermined temperature; a first heat exchanger fluidly connected to the cryo pump and configured to accept a first portion of the hydrogen stream from the cryo pump, exchange energy with ambient air at an ambient temperature, and increase a temperature of the first portion of the hydrogen stream to equal to or below the ambient temperature; a by-pass line configured to accept a second portion of the hydrogen stream from the cryo pump to bypass the first heat exchanger and connect with a downstream of the first heat exchanger so as to combine the second portion of the hydrogen stream with the first portion of the hydrogen stream to provide a combined stream, wherein the second proportion of the hydrogen stream is controlled by a control valve; a second heat exchanger fluidly connected with the first heat exchanger and the bypass line, and configured to accept the combined stream and provide heating when the ambient temperature is lower than a threshold and provide a hydrogen fuel at a second predetermined pressure and a second predetermined temperature; and a dispenser fluidly connected with the second heat exchanger and configured to accept the hydrogen fuel and dispense the hydrogen fuel at a predetermined flow rate to a vehicle having an onboard storage system, wherein the ratio of the compression energy input (Ws) to thermal management energy input (Qth) is greater than one.

2. The system of claim 1, wherein the compression energy input (Ws) is defined by enthalpy of the hydrogen stream from the cryo pump (he) minus enthalpy of the liquid hydrogen from the cryotank (ht), and the thermal management energy input is energy fromsources other than the ambient environment required for vaporization and cooling of the combined hydrogen and the hydrogen fuel needed before the hydrogen fuel is dispensed.

3. The system of claim 1, wherein the ratio of the compression energy input to thermal management energy input is greater than two.

4. The system of claim 1, wherein the first heat exchanger is an open-air natural draft ambient vaporizer.

5. The system of claim 1, wherein the first heat exchanger is an enclosed forced air vaporizer with induced draft or force draft fan arrangement.

6. The system of claim 1, wherein the second heat exchanger is a direct electrical heater without an intermediate heat transfer fluid medium.

7. The system of claim 1, wherein the second heat exchanger provides no heating when the ambient temperature is higher than the threshold, and the combined stream is fed to the dispenser directly.

8. The system of claim 1, wherein the onboard storage system is selected from a H35 fuel onboard storage system, and a H70 fuel onboard storage system.

9. The system of claim 1, further comprising a controller connected electronically with and configured to individually control one of more of the cryo pump, the first heat exchanger, the control valve, and the second heat exchanger, and the dispenser.

10. The system of claim 1, wherein the controller is configured to control a proportion of the bypass around the first heat exchanger, and / or control the second heat exchanger.

11. A method of making the system of any of the preceding claims, comprising: providing components; and assembling the components together to provide the pump or the system.

12. A method of using the system of any of the preceding claims, comprising:providing the first predetermined pressure, the first predetermined temperature, the second predetermined pressure, the second predetermined temperature, and the predetermined flow rate; determining a proportion of the first portion and the second portion of the hydrogen stream from the cryo pump; providing the first portion and the second portion of the hydrogen stream based on the proportion; and determining whether and how much the second heat exchanger needs to provide heating and providing heating when needed.

13. The method of claim 12, further comprising: determining a type of fuel onboard storage system of a vehicle; and fueling a type of fuel corresponding to the type of fuel onboard storage system to the vehicle.

14. The method of claim 13, wherein the type of fuel onboard storage system is selected from a H35 fuel onboard storage system, and a H70 fuel onboard storage system.

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