Direct liquefaction for vehicle refueling

A refueling system may include an inlet tube that fluidly connects to a container containing gaseous hydrogen, a cryocooler including a cold tip and a cold head, the cold tip driven to a hydrogen liquefaction temperature by the cold head, a condensation chamber fluidly connected to the inlet tube to receive the gaseous hydrogen and thermally connected to the cryocooler cold tip, a catalyst disposed in the condensation chamber and that conducts ortho-to-para hydrogen conversion. The cryocooler cold tip absorbs a resulting exothermic reaction. The refueling system may also include a funnel fluidly connected to the condensation chamber and that receives liquid hydrogen from the condensation of the gaseous hydrogen, and a coupling mechanism fluidly connected to the funnel to receive the liquid hydrogen and having a nozzle downwardly movable to fluidly connect from above to an upwards facing tank inlet of a vehicle.

BACKGROUND

Liquid hydrogen is typically provided by compressed gas suppliers and their distributors to their customers. Large liquid hydrogen storage Dewars are either permanently installed on the customer site or transported to the customer site and temporarily left on the customer site for use until empty. These storage Dewars then require and extensive set of ground support equipment to transfer the hydrogen between the storage Dewar and where the customer is using the liquid hydrogen for product development or validation. The ground support equipment usually includes long lengths of vacuum jacketed piping and valves. This equipment along with the storage Dewar that are expensive to purchase or rent, custom made, and require a large footprint of land to sit on. This land must be modified to meet certain compressed gas supplier requirements based on best practices and standards. Modifications may include such things as a cement pad and secure fencing. In addition, substantial amount of land is needed for the liquid hydrogen delivery trailers to maneuver. All of these hardware requirements and land usage are cost prohibited to those that only require a small amount of liquid hydrogen (less than 100 L). In addition, remote locations logistically do not have access to liquid hydrogen at all.

As a result, obtaining small quantities of liquid hydrogen to conduct experiments and validate prototypes of products that store and use liquid hydrogen and conduct flight operations in remote locations has been determined to be cost prohibitive with many logistical and legal barriers. There is a demand for a system for making small quantities of liquid hydrogen at relatively low cost with relatively small amount of hardware required.

SUMMARY OF THE INVENTION

To this end, an invention is disclosed that addresses these issues by taking room temperature gaseous hydrogen in high pressure bottles that are commercially available at reasonable prices or gaseous hydrogen generated locally and liquefying the hydrogen using a cryocooler directly on top of a closely coupled UAV flight Dewar.

The systems disclosed herein will enable extremely long-duration (20 hours)/long-range (1,000 miles) operations for Unmanned Aerial Vehicles (UAVs). This UAV liquid hydrogen energy storage technology combined with fuel cell produced electrical power is scalable for commercial UAVs operating at less than 55 lbs. all the way up to Personal Air Vehicles or flying cars. The technology disclosed herein may work in combination with systems and processes for refueling the UAV flight Dewar patented by NEOEx as U.S. Pat. Nos. 10,773,822 and 10,981,666, the disclosures of which are hereby incorporated by reference in their entirety.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example systems, methods, and so on, that illustrate various example embodiments of aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that one element may be designed as multiple elements or that multiple elements may be designed as one element. An element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale.

DETAILED DESCRIPTION

FIG.1illustrates an exemplary system110for refueling a vehicle200. The system110may include a frame or skid120which may include wheels or casters125for facilitating transport of the system110. The system110may include an apparatus100for direct liquefaction of hydrogen, as described in detail below. The apparatus100may be installed on a hydraulic lift115for lifting and lowering the apparatus100. The system110may also include a compressor140, a chiller145, gas storage150, a generator155, an energy storage (batteries) cabinet165, and an instrumentation and controls cabinet170. The system110is described herein for contextual purposes and is not meant to limit the herein disclosed apparatus100for direct liquefaction of hydrogen.

FIG.2Aillustrates a schematic drawing of an exemplary apparatus100for direct liquefaction of hydrogen into a flight Dewar. The apparatus100may be used for producing liquid hydrogen without the need for vacuum jacketed transfer hoses. The apparatus100is compact and may be designed to interface with the systems and methods for the transfer of cryogenic fluids disclosed in U.S. Pat. Nos. 10,773,822 and 10,981,666. The apparatus100may include a cryocooler1that includes cold head1a, a middle portion1b, and a cold tip1c, an actuator rod2(including a top portion2aand a bottom portion2b), bellows3for the actuator rod2, a cryocooler mounting flange4, a liquefier chamber5that in itself may be constructed of a vacuum jacketed insulated wall, radiation shield wall seals6, radiation shields7, insulation (aerogel with multilayer insulation)8, main bellows9, a cap10with compression fitting features, a cap arm hinge mechanism11, a cold hydrogen gas inlet12, cryogenic foam insulation (polyurethane)13, an ortho-to-para conversion catalyst15, a condensation chamber16, a mesh screen filter17, a drain funnel18, a liquid transfer tube nozzle19(shown inFIG.1in refueling configuration), a transfer tube nozzle compression fitting20, a coupling flange21, a tank flange22, a flange clamp23, a vacuum space24, and a vacuum port25.

The direct hydrogen liquefaction apparatus coupling flange21may be connected to the tank flange22and held together by the flange clamp23. A vacuum may be created in the vacuum space24through the vacuum port25to eliminate any air and moisture in the system and to improve the performance of the insulation8. The cap10that is normally closed on the UAV liquid hydrogen flight tank may then be pressed open using the actuator rod2via the cap arm hinge mechanism11. The actuator arm2may be made of two materials to minimize heat leak towards the flight tank. For example, the actuator arm's upper portion2amay be made of stainless steel or similar material and the lower portion2bmay be made of a composite material such as G10 high-pressure fiberglass laminate composite or similar material for low thermal conductivity and high strength at cryogenic temperatures. A stainless-steel flexure bellows3may be attached to the rod2.

Radiation shields7may be located at the top of the liquefier chamber5to keep the cryocooler mounting flange4from getting cold. Radiation shield wall seals6of a compliant seal material (e.g., Kapton) may be located against the walls of the liquefier chamber5and the cryocooler1bto keep convective flows from forming and increasing heat transfer. A bellows9may be used to provide flexibility in independently moving and connecting the liquid transfer tube nozzle19and the actuator rod2.

Cold gaseous hydrogen that is pre-chilled using a liquid nitrogen bath or another cryocooler may be introduced into the liquefier chamber5through the cold gaseous hydrogen inlet tube12that may be insulated with cryogenic temperature rated foam13(e.g., two-part polyurethane foam). The gaseous hydrogen coming in should be at a steady state condition of ortho to para hydrogen concentration at a temperature of 80 K or lower. This can be achieved by running the gaseous hydrogen through an ortho to para conversion catalyst at 80 K.

The cold gaseous hydrogen may then enter the condensation chamber16around and cooled by the cryocooler cold tip1c. The cryocooler cold tip1cmay be driven to the hydrogen liquefaction temperature of between 20 and 25 K by the cryocooler cold head connected to a compressor (not shown). Further ortho-to-para hydrogen conversion may be conducted using the catalyst15and the cryocooler cold tip1cabsorbs the exothermic reaction. Liquid may then drip into the funnel18by gravitational force and into the liquid transfer tube nozzle19. The liquid transfer nozzle compression fitting20seals onto the tank flange22. Any vapor that is generated as the system is cooled down will rise back into the condensation chamber16and re-condense. The cold hydrogen inlet12is maintained at a constant pressure of approximately 50 psia or below.

System100achieves liquefaction from above the flight tank, eliminating the need for vacuum jacketed transfer hoses. Room temperature gaseous hydrogen may be procured in high pressure bottles (commercially available at reasonable prices) and the gaseous hydrogen therein turned into liquid hydrogen locally at the refueling site (and indeed right above the aircraft fuel tank inlet) using a cryocooler above a closely coupled UAV flight Dewar. This approach lowers cost and amount of hardware.

FIG.2Billustrate a schematic diagram of an exemplary alternative version of the direct liquid hydrogen apparatus100awith the addition of an isolation valve27that fluidly traverses the liquid transfer nozzle19. The valve27may be pneumatically actuated using gaseous helium because the gas does not condense at 20 K.

FIG.2Cillustrates a schematic diagram of an exemplary actuator system200that works with the system100a. Helium is a non-renewable resource. This invention will minimize the use of helium in cryogenic hydrogen system100aby eliminating the loss of helium in the actuator when the valve27is opened and closed.

The helium saver actuator system200may include a pneumatic bladder28that is operably connected to the valve27and is divided in two halves28a,28b. The first half28ahas gaseous nitrogen in it and the second half28bhas gaseous helium in it. The bladder28operates at room temperature. The pneumatic valve27is normally closed and actuated by a spring. Helium pressure is required to counter the spring force to open the valve27. The helium half28bof the bladder is charged up to operating pressure via one or more tubes26just prior to opening the valve27. Nitrogen pressure is supplied via the one or more tubes26to the other half28aof the bladder which pressurizes the helium side and opens the valve27. Nitrogen pressure may then be relieved via the one or more tubes26and vented to the atmosphere to close the valve27.

An alternative would be to replace the pneumatically actuated valve27with an electric solenoid valve that can operate at 20 K. This would eliminate all use of helium. The helium tube26would be replaced with electrical power leads to the solenoid actuator.

FIG.3illustrates a schematic diagram of yet another exemplary alternative version of the direct liquid hydrogen apparatus100b. The system100binvolves flowing high pressure gaseous hydrogen28through a series of heat exchangers29thermally attached to various cryocoolers30a,30b. Each cryocooler30a,30bis specifically sized to reduce the gas temperature, remove heat of the ortho-to-para hydrogen conversion process, and then liquefy the gas. In this scenario the liquid is stored in a Dewar31at low pressure and then, once filled, is transferred via pressure32into the UAV33using the apparatus34patented in U.S. Pat. Nos. 10,773,822 and 10,981,666.

FIG.4Aillustrates a perspective view of an exemplary alternative version of the direct liquid hydrogen apparatus100cwith the addition of a rotary feed through35for a mechanically actuated liquid hydrogen isolation valve27a(shown inFIGS.4B and4C). The rotary feed through35enables the use of a manual or automated actuator to open and close the liquid hydrogen isolation valve27a.

FIG.4Billustrates a transparent perspective view of the exemplary alternative version of the direct liquid hydrogen apparatus100cwith the addition of a mechanically driven isolation valve27aconnected to a rotary feed through35via a rotary actuator rod57.

FIG.4Cillustrates a transparent perspective view of the exemplary alternative version of the direct liquid hydrogen apparatus100cwith the addition of a fill level sensor37incorporated into the liquid transfer tube nozzle19. The sensor37enables accurate filling of the flight tank using ground support equipment thus reducing the amount of sensing hardware on the flight vehicle. The fill level sensor37senses a fill level of the vehicle's tank and communicates the information. Fueling may be terminated upon the sensor37detecting a certain fuel level in the tank.FIG.4Calso shows the cap opener plunger38.

FIG.5Aillustrates a top view of the exemplary alternative version of the direct liquid hydrogen apparatus100cwith the addition of feed throughs40and39for a cryocooler temperature sensor45and heater44, respectively, for controlling the cryocooler cold tip1ctemperature during the hydrogen liquefaction process.

FIG.5Billustrates a bottom view of a perspective view of the exemplary alternative version of the direct liquid hydrogen apparatus100cwith the addition of the fill level sensor37integrated into the liquid transfer tube nozzle19and the bellows mounting flange36that connects the bellows9to the bottom of the liquefier chamber5via the liquefier chamber bottom flange5das shown inFIG.6E.

FIG.6Aillustrates an exploded view of the exemplary direct liquid hydrogen apparatus100cin four sections that would be described in more detail inFIGS.6B-6E. Insulation of the various cryogenic parts in each section is not shown.

FIG.6Billustrates an exploded view of the top section of the direct liquid hydrogen apparatus. The cryocooler cold head1ais installed into the cryocooler mounting flange4and is sealed to4using cryocooler flange seal53. The cryocooler mounting flange is attached to the liquefier chamber top flange5cusing bolts52and nuts55and is sealed using cryocooler mounting flange seal54. Radiation shields7a,7b, and7care mounted to the bottom of flange4using threaded rods41shown inFIG.6C. Space nuts56are used to separate and hold the radiation shields in place. Radiation shield wall seals6a,6b, and6care used to minimize convection along the liquefier chamber5wall.

FIG.6Cillustrates an exploded view of the top middle section of the direct liquid hydrogen apparatus100c. Split seal fittings are used as feed throughs for cold gaseous hydrogen12, cold tip heater power wires39, and cold tip temperature measurement wires40. Tubes12a,39a, and40aare used to connect12,39, and40to the condensation chamber16split seal fitting feed throughs12b,39b, and40b. The condensation chamber16consists of a top flange42constructed of stainless steel, an inner wall43constructed of oxygen-free high thermal conductivity (OFHC) copper, an inner wall flange46constructed of OFHC copper, the condensation chamber outer wall16is constructed of stainless steel, the filter flange47constructed of stainless steel, and the condensation bottom flange50constructed of stainless steel. The condensation bottom flange50features a drain funnel18, mesh screen filter17, top flange48for holding filter17, and a bottom flange49for holding filter17. Bolts51hold the condensation chamber bottom flange50to the filter flange47and are sealed using a copper gasket and serrated sealing surfaces (not shown). Ortho-to-para hydrogen catalyst15is installed inside the condensation chamber. A heater44is mounted to the external wall of the condensation chamber inner wall43to control the temperature of the inner wall based on temperature measurements from temperature sensor45.

FIG.6Dillustrates an exploded view of the bottom middle section of the direct liquid hydrogen apparatus. The liquid hydrogen isolation valve27a, which can be a cryogenic ball valve, is mechanically actuated using a rotary actuator rod57and a rotary feed through35. A manual or automated actuator (not shown) on the outside of the liquefier chamber5can be used to open and close valve27a. The rotary feed through is mounted to the liquefier chamber outer vacuum wall5avia a vacuum clamp38. A vacuum port25is used to pull vacuum inside the liquefier chamber. A separate vacuum pump out not shown is used to pull vacuum between the liquefier chamber outer vacuum wall5aand the inner vacuum wall5b. Liquid hydrogen generated in the condensation chamber16drains via gravity through the liquid transfer tube58, liquid hydrogen isolation valve27a, and the liquid transfer nozzle19into the flight tank not shown. The fill level sensor37is used to accurately measure the full level of the tank. The fill tube insulation13insulates the liquid transfer nozzle19.

FIG.6Eillustrates an exploded view of the bottom section of the direct liquid hydrogen apparatus. The figure shows the bellows mounting flange36is attached to the liquefier chamber bottom flange5dusing bolts60and nuts64. The flanges5dand36are sealed using seal59. Bellows9is attached to the bellows mounting flange36on one end and to a coupling flange21at the other end. The coupling flange21is attached to the tank flange22using flange clamp23. The tank cap is opened using the cap opener plunger38and a compression spring61housed inside the spring housing62. The spring housing62is mounted to the liquefier chamber bottom flange5dusing bolts63.

Definitions

The following includes definitions of selected terms employed herein. The definitions include various examples or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions.

As used herein, an “operable connection” or “operable coupling,” or a connection by which entities are “operably connected” or “operably coupled” is one in which the entities are connected in such a way that the entities may perform as intended. An operable connection may be a direct connection or an indirect connection in which an intermediate entity or entities cooperate or otherwise are part of the connection or are in between the operably connected entities. In the context of signals, an “operable connection,” or a connection by which entities are “operably connected,” is one in which signals, physical communications, or logical communications may be sent or received. Typically, an operable connection includes a physical interface, an electrical interface, or a data interface, but it is to be noted that an operable connection may include differing combinations of these or other types of connections sufficient to allow operable control. For example, two entities can be operably connected by being able to communicate signals to each other directly or through one or more intermediate entities like a processor, operating system, a logic, software, or other entity. Logical or physical communication channels can be used to create an operable connection.