LOW-PRESSURE PUMP FOR HYDROGEN PUMPING SYSTEM

Description

FIELD

The present disclosure relates generally to a hydrogen pumping system, and more particularly to a cryogenic pump used in a hydrogen pumping system.

BACKGROUND

Fuel cells have shown promise as an alternative power source for vehicles and other transportation applications. Fuel cells operate with a renewable energy carrier, such as hydrogen. Fuel cells also operate without toxic emissions and greenhouse gases. In order to resupply a vehicle operating with a fuel cell which uses hydrogen as the renewable energy carrier hydrogen is stored, typically in a fluid form, at a hydrogen pumping system which, when used to provide fuel for a vehicle, is also called a hydrogen fueling station.

Hydrogen fueling stations for vehicles can store bulk hydrogen as a liquid at a pressure of 1 to 6 barg and a temperature of 18 to 25K. (Note: “barg” refers to gage pressure in units of bar). In order to dispense the stored liquid hydrogen to hydrogen-fueled vehicles, the hydrogen is typically provided in a gaseous state at a high pressure of 600 to 1000 barg and a temperature of −40 to −20 deg C. (233 to 253K).

In other applications, hydrogen fueling stations are configured to provide liquid hydrogen at substantially lower pressures. These stations, referred to as “subcooled liquid hydrogen or “sLH2” fueling stations provide liquid fuel to vehicles at about 0.4 MPa to 2.0 MPa, and typically between 0.6 MPa and 1.4 MPa.

The transition from liquid to gaseous hydrogen in some systems is effected with the aid of a dual stage pumping system. In a first stage the liquid hydrogen is “subcooled” by increasing the pressure of the fluid with a low-pressure pump which in dual stage systems is referred to as a first stage pump. The temperature of the subcooled hydrogen is increased from the initial temperature due to the working of the first stage pump. Additionally, the temperature of the subcooled liquid hydrogen increases as a result of heat gain from the atmosphere. The increased pressure provided by the first stage pump ensures the hydrogen fluid stays in a fluid form as it is heated. A second stage pump is then used to further increase pressure with incumbent increase in temperature.

The two-stage approach described above is typically limited by the physical constraints of liquid hydrogen entering the first stage of the pumping system. In particular, since the bulk liquid hydrogen is kept close to its triple point so as to reduce costs associated with storing the liquid hydrogen, the bulk liquid hydrogen is easily vaporized with only a slight increase in temperature or reduction of pressure. Consequently, even the presence of a valve between the bulk storage tank and the first stage pump which creates a small pressure drop as the liquid hydrogen flows into the suction of a first stage pump can be sufficient to flash the bulk hydrogen to vapor which makes pumping of the hydrogen problematic.

Moreover, when a low-pressure pump sits idle for a period of time, the system absorbs heat from the surrounding environment. This heat vaporizes some of the liquid hydrogen within the low-pressure pump which is typically ejected along with vented hydrogen in state-of-the-art pump technology. This reduces the efficiency of the system.

When a low-pressure pump is being used as a transfer pump to pump between pumping stages or storage tanks/reservoirs the problem of vaporization is further exacerbated by any gain of energy from the piping between the bulk storage tank and the low-pressure pump suction since even a slight increase in temperature can cause vaporization of the bulk liquid hydrogen. Accordingly, in many applications the bulk liquid hydrogen is gravity fed into the suction of the low-pressure pump. Alternatively, the bulk hydrogen may be further cooled as it exits the bulk storage tank.

In dual stage systems, in order to minimize energy transfer into the liquid hydrogen as it moves thorough the first and second pumping stages a single drive rod is typically used to drive both the first stage and second stage pumps. While effective in reducing the amount of energy put into the liquid hydrogen, the mechanical coupling required in this type of apparatus causes the first stage pump to be operated at a mass flow rate exceeding the capacity of the second stage pump. This results in inefficiency in the system since the excess hydrogen must be removed from the outlet of the first stage pump. The excess hydrogen may be released into the atmosphere, burned, or fed back into the bulk storage tank.

Other issues arise with known systems due to the orientation of the systems. In systems wherein a low-pressure pump is submerged in a liquid hydrogen bath, any vaporized hydrogen migrates to the uppermost areas of the pump, which can be problematic since pumps are typically not effective at moving vaporized hydrogen. Consequently, the pump outlet is generally located at the bottom of the pumps. This configuration, while effective in guarding against attempting to pump vapor makes the pump top-heavy and thus inherently unstable. Additionally, vapor in the pump is trapped thus requiring the pump to be intermittently vented which results in system product loss.

What is needed is a system which reduces one or more of the issues discussed above.

SUMMARY

According to one embodiment of the present disclosure, a hydrogen pumping system includes a low-pressure pump system. The low-pressure pump system includes at least one fluid reservoir, a hydrogen pump cylinder fluidically connected to the at least one fluid reservoir, a piston assembly positioned within the hydrogen pump cylinder, a hydrogen cylinder rod portion at least partially positioned within the hydrogen pump cylinder, and a plunger assembly including a sealing member and including a presser component, the plunger assembly operably connected to the hydrogen cylinder rod portion. The sealing member is configured to seal with a valve body of the piston assembly with the presser component not contacting the piston assembly. The presser component is configured to selectively force the valve body in a direction toward the sealing member.

In one or more embodiments of the hydrogen pumping system the piston assembly, the hydrogen pump cylinder, and the plunger assembly define at least in part a variable volume compression chamber above the piston assembly when the sealing member is sealed with the valve body. The hydrogen cylinder rod portion defines a longitudinal axis. Additionally, the presser component is located beneath the sealing member along the longitudinal axis.

In one or more embodiments of the hydrogen pumping system the low-pressure pump system includes a guide, which in some embodiments is configured as a guide ring, ring operably connected to the hydrogen cylinder rod portion and configured to center the hydrogen cylinder rod portion within the hydrogen pump cylinder.

In one or more embodiments of the hydrogen pumping system the low-pressure pump system the guide is located beneath the presser component.

In one or more embodiments of the hydrogen pumping system the piston assembly includes a hollow body, a piston ring positioned about the hollow body, and a presser surface axially aligned with the presser component with respect to the longitudinal axis and configured to be contacted by the presser component to selectively force the valve body in the direction toward the sealing member. The valve body is a circular valve body in some of these embodiments.

In one or more embodiments of the hydrogen pumping system the plunger assembly includes a plunger operably connected to the hydrogen cylinder rod portion and the sealing member is a circular sealing member. Additionally, the circular sealing member is supported by the plunger and the presser component is located beneath the plunger along the longitudinal axis.

In one or more embodiments of the hydrogen pumping system an upper surface of the sealing member is spaced apart from a lower surface of the presser component by a first distance along the longitudinal axis. The sealing member is configured to seal with a lower surface of the valve body. The lower surface of the valve body is spaced apart from the presser surface by a second distance along the longitudinal axis. Additionally, The second distance is greater than the first distance, such that the sealing member cannot seal with the lower surface of the valve body when the presser component is in contact with the presser surface.

In one or more embodiments of the hydrogen pumping system the low-pressure pump system includes a pump head assembly located at an upper end of the hydrogen pump cylinder, the pump head assembly including a low-pressure pump unit outlet, the hydrogen cylinder rod portion extending through the pump head assembly. An insulation vessel is positioned around the hydrogen pump cylinder. A thermal decoupling rod portion is operably connected to the hydrogen cylinder rod portion within the insulation vessel at a location above the pump head assembly. In some embodiments the hydrogen cylinder rod portion and the thermal decoupling rod portion are integrally formed. A cold end portion top plate seals an upper end of the insulation vessel and the thermal decoupling rod portion extends through the cold end portion top plate.

In one or more embodiments of the hydrogen pumping system a drive rod of a drive system is operably connected to the hydrogen cylinder rod portion through the thermal decoupling rod portion. A position indicator is configured to generate a signal associated with a position of the drive rod. A control system is configured to control the drive system based upon the signal generated by the position indicator to move the drive rod.

In one or more embodiments of the hydrogen pumping system the control system includes a memory including program instructions stored therein. A controller is operably connected to the memory, the drive system, and the position indicator. The controller is configured to execute the program instructions to control the drive system to move the drive rod such that the hydrogen cylinder rod portion moves upwardly along the longitudinal axis from a first position whereat the presser component is in contact with the presser surface to a second position whereat the presser component is not in contact with the presser surface and the sealing member is not sealed with the valve body. The controller is further configured to execute the program instructions to control the drive system to move the drive rod such that the hydrogen cylinder rod portion moves upwardly along the longitudinal axis from the second position to a third position whereat the presser component is not in contact with the presser surface and the sealing member is sealed with the valve body. The controller is further configured to execute the program instructions to control the drive system to move the drive rod such that the hydrogen cylinder rod portion moves upwardly along the longitudinal axis from the third position to a fourth position with the sealing member sealed with the valve body thereby compressing a fluid within the variable volume compression chamber.

In one or more embodiments of the hydrogen pumping system the controller is further configured to execute the program instructions to control the drive system to move the hydrogen cylinder rod portion downwardly along the longitudinal axis from the fourth position to a fifth position whereat the sealing member is not sealed with the valve body and the presser component is not in contact with the presser surface, to move the hydrogen cylinder rod portion downwardly along the longitudinal axis from the fifth position to a sixth position whereat the presser component contacts the presser surface and the sealing member is not sealed with the valve body, and to move the hydrogen cylinder rod portion downwardly along the longitudinal axis from the sixth position to the first position with the presser component contacting the presser surface and the sealing member not sealed with the valve body.

In one or more embodiments of the hydrogen pumping system the longitudinal axis is not aligned with a horizontal axis, such that gas within the hydrogen pump cylinder moves upwardly within a fluid in the hydrogen pump cylinder toward the low-pressure pump unit outlet.

In one or more embodiments a low-pressure pump for use in a hydrogen pumping system includes a hydrogen pump cylinder configured to be supplied with hydrogen from a fluid reservoir, a piston assembly positioned within the hydrogen pump cylinder, a hydrogen cylinder rod portion at least partially positioned within the hydrogen pump cylinder, and a plunger assembly including a sealing member and including a presser component, the plunger assembly operably connected to the hydrogen cylinder rod portion. The sealing member is configured to seal with a valve body of the piston assembly with the presser component not contacting the piston assembly. The presser component is configured to selectively force the valve body in a direction toward the sealing member.

In one or more embodiments of the low-pressure pump the piston assembly, the hydrogen pump cylinder, and the plunger assembly define at least in part a variable volume compression chamber above the piston assembly when the sealing member is sealed with the valve body. The hydrogen cylinder rod portion defines a longitudinal axis. The presser component is located beneath the sealing member along the longitudinal axis.

In one or more embodiments of the low-pressure pump a guide, which can be embodied as a guide ring, is operably connected to the hydrogen cylinder rod portion and configured to center the hydrogen cylinder rod portion within the hydrogen pump cylinder.

In one or more embodiments of the low-pressure pump the guide is located beneath the presser component.

In one or more embodiments of the low-pressure pump the piston assembly includes a hollow body, a piston ring positioned about the hollow body, and a presser surface axially aligned with the presser component with respect to the longitudinal axis and configured to be contacted by the presser component to selectively force the valve body in the direction toward the sealing member. The valve body in some of these embodiments is a circular valve body.

In one or more embodiments of the low-pressure pump the plunger assembly comprises a plunger operably connected to the hydrogen cylinder rod portion. The sealing member is a circular sealing member. The circular sealing member is supported by the plunger. The presser component is located beneath the plunger along the longitudinal axis.

In one or more embodiments of the low-pressure pump an upper surface of the sealing member is spaced apart from a lower surface of the presser component by a first distance along the longitudinal axis. The sealing member is configured to seal with a lower surface of the valve body. The lower surface of the valve body is spaced apart from the presser surface by a second distance along the longitudinal axis. The second distance is greater than the first distance, such that the sealing member cannot seal with the lower surface of the valve body when the presser component is in contact with the presser surface.

In one embodiment, a method of operating a low-pressure pump for a pumping operation includes providing a hydrogen cylinder output at an upper end of a hydrogen cylinder and providing a hydrogen cylinder inlet at a lower end of the hydrogen cylinder. A first hydrogen fluid is provided to the hydrogen cylinder and tension is applied to a hydrogen piston rod portion within the hydrogen cylinder such that a gas at the upper end of the hydrogen cylinder is forced through the hydrogen cylinder output. The method includes continuing to apply the tension to the hydrogen piston rod portion such that the first hydrogen fluid is forced through the hydrogen cylinder output after the gas is forced through the hydrogen cylinder output.

In one or more embodiments of the method the hydrogen cylinder defines a longitudinal axis which defines, along with a horizontal axis, an angle of at least 15 degrees.

In one or more embodiments the method includes moving second hydrogen fluid into the hydrogen cylinder by the applying of the tension to the hydrogen piston rod portion.

In one or more embodiments of the method the second hydrogen fluid is moved into the hydrogen cylinder from a hydrogen supply pipe.

In one or more embodiments of the method the second hydrogen fluid is moved into the hydrogen cylinder from a hydrogen reservoir, and the hydrogen cylinder is located at least partially within the hydrogen reservoir.

In one or more embodiments of the method applying the tension to the hydrogen piston rod portion includes controlling the hydrogen piston rod portion using a controller and the control of the hydrogen piston rod portion does not use an input associated with a hydrogen level in the hydrogen reservoir.

In one or more embodiments of the method the applying the tension to the hydrogen piston rod portion is performed without any previous venting of the hydrogen cylinder for the pumping operation.

In one or more embodiments the method is performed in a system which cannot be configured to vent the hydrogen cylinder.

According to another embodiment of the present disclosure, a hydrogen pumping system includes a low-pressure pump system. The low-pressure pump system includes a hydrogen pump cylinder, a hydrogen cylinder rod portion within the hydrogen pump cylinder, a plunger assembly within the hydrogen pump cylinder, the plunger assembly including a presser component and a plunger, a piston assembly within the hydrogen pump cylinder, the piston assembly including a valve body and a presser surface spaced apart from the valve body, a drive system which in some embodiments is a hydraulic drive system, a memory including program instructions stored therein, and a controller operably connected to the memory and the drive system. The controller is configured to execute the program instructions to control the drive system to move the hydrogen cylinder rod portion between a lowermost position whereat the presser component is in contact with the presser surface and the plunger assembly is not sealed with the valve body and an uppermost position whereat the presser component is not in contact with the presser surface and the plunger assembly is sealed with the valve body.

In one or more embodiments of the hydrogen pumping system, the controller is further configured to execute the program instructions to control the drive system to move the hydrogen cylinder rod portion between the lowermost position and a first plurality of intermediate positions whereat the presser component is not in contact with the presser surface and the plunger assembly is sealed with the valve body, and control the drive system to move the hydrogen cylinder rod portion between the uppermost position and a second plurality of intermediate positions whereat the presser component is in contact with the presser surface and the plunger assembly is not sealed with the valve body.

In one or more embodiments of the hydrogen pumping system the controller is further operably connected to at least one fluid level detector and the controller is further configured to execute the program instructions to obtain a signal associated with a fluid level in the hydrogen pump cylinder, determine presence of gas within the hydrogen pump cylinder based upon the obtained signal, and control the drive system to move the hydrogen cylinder rod portion from the lowermost position to the uppermost position based upon the determining the presence of gas in the hydrogen pump cylinder.

In one or more embodiments of the hydrogen pumping system the controller is further configured to execute the program instructions to receive a signal indicative of a fuel delivery request, determine a stroke length of the hydrogen cylinder rod portion associated with a fuel delivery rate associated with the fuel delivery request, at least one of (i) associate the determined stroke length with a first of the first plurality of intermediate positions, (ii) associate the determined stroke length with a first of the second plurality of intermediate positions, and (iii) associate the determined stroke length with a pair of intermediate positions including a second of the first plurality of intermediate positions and a second of the second plurality of intermediate positions. The controller is further configured to execute the program instruction to control the drive system to move the hydrogen cylinder rod portion based upon the at least one of the associated first of the first plurality of intermediate positions, the associated first of the second plurality of intermediate positions, and the associated pair of intermediate positions.

In one or more embodiments of the hydrogen pumping system the controller is configured to execute the program instructions to associate the determined stroke length with the first of the second plurality of intermediate positions, and control the drive system to move the hydrogen cylinder rod portion based upon the associated first of the second plurality of intermediate positions to provide a first partial power stroke between the uppermost position and the associated first of the second plurality of intermediate positions.

In one or more embodiments of the hydrogen pumping system the controller is configured to execute the program instructions to associate the determined stroke length with the first of the first plurality of intermediate positions, and control the drive system to move the hydrogen cylinder rod portion based upon the associated first of the first plurality of intermediate positions to provide a second partial power stroke between the lowermost position and the associated first of the first plurality of intermediate positions.

In one or more embodiments of the hydrogen pumping system the controller is configured to execute the program instructions to associate the determined stroke length with the pair of intermediate positions, and control the drive system to move the hydrogen cylinder rod portion based upon the pair of intermediate positions to provide a third partial power stroke between the pair of intermediate positions.

In one or more embodiments of the hydrogen pumping system the controller is further operably connected to a position indicator configured to provide a signal indicative of a position of the hydrogen cylinder rod portion within the hydrogen pump cylinder, and the controller is further configured to execute the program instructions to control the drive system based upon the signal indicative of the position of the hydrogen cylinder rod portion.

In one or more embodiments of the hydrogen pumping system a vapor barrier extending within the lantern from the cold end portion top plate to the warm end portion and positioned about at least one of the hydraulic rod portion and the thermal decoupling rod portion.

In one or more embodiments a low-pressure pump system includes a hydrogen pump cylinder, a hydrogen cylinder rod portion within the hydrogen pump cylinder, a plunger assembly within the hydrogen pump cylinder, the plunger assembly including a presser component and a plunger, a piston assembly within the hydrogen pump cylinder, the piston assembly including a valve body and a presser surface spaced apart from the valve body, a drive system, a memory including program instructions stored therein, and a controller operably connected to the memory and the drive system, which may be a hydraulic drive system. The controller is configured to execute the program instructions to control the drive system to move the hydrogen cylinder rod portion between a lowermost position whereat the presser component is in contact with the presser surface and the plunger assembly is not sealed with the valve body and an uppermost position whereat the presser component is not in contact with the presser surface and the plunger assembly is sealed with the valve body.

In one or more embodiments of the low-pressure pump system the controller is further configured to execute the program instructions to control the drive system to move the hydrogen cylinder rod portion between the lowermost position and a first plurality of intermediate positions whereat the presser component is not in contact with the presser surface and the plunger assembly is sealed with the valve body, and control the drive system to move the hydrogen cylinder rod portion between the uppermost position and a second plurality of intermediate positions whereat the presser component is in contact with the presser surface and the plunger assembly is not sealed with the valve body.

In one or more embodiments of the low-pressure pump system the controller is further operably connected to at least one fluid level detector. The controller is further configured to execute the program instructions to obtain a signal associated with a fluid level in the hydrogen pump cylinder, determine presence of gas within the hydrogen pump cylinder based upon the obtained signal, and control the drive system to move the hydrogen cylinder rod portion from the lowermost position to the uppermost position based upon the determining the presence of gas in the hydrogen pump cylinder.

In one or more embodiments of the low-pressure pump system the controller is further configured to execute the program instructions to receive a signal indicative of a fuel delivery request, determine a stroke length of the hydrogen cylinder rod portion associated with a fuel delivery rate associated with the fuel delivery request, at least one of (i) associate the determined stroke length with a first of the first plurality of intermediate positions, (ii) associate the determined stroke length with a first of the second plurality of intermediate positions, and (iii) associate the determined stroke length with a pair of intermediate positions including a second of the first plurality of intermediate positions and a second of the second plurality of intermediate positions The controller is further configured to execute the program instructions to control the drive system to move the hydrogen cylinder rod portion based upon the at least one of the associated first of the first plurality of intermediate positions, the associated first of the second plurality of intermediate positions, and the associated pair of intermediate positions.

In one or more embodiments of the low-pressure pump system the controller is configured to execute the program instructions to associate the determined stroke length with the first of the second plurality of intermediate positions, and control the drive system to move the hydrogen cylinder rod portion based upon the associated first of the second plurality of intermediate positions to provide a first partial power stroke between the uppermost position and the associated first of the second plurality of intermediate positions.

In one or more embodiments of the low-pressure pump system the controller is configured to execute the program instructions to associate the determined stroke length with the first of the first plurality of intermediate positions, and control the drive system to move the hydrogen cylinder rod portion based upon the associated first of the first plurality of intermediate positions to provide a second partial power stroke between the lowermost position and the associated first of the first plurality of intermediate positions.

In one or more embodiments of the low-pressure pump system the controller is configured to execute the program instructions to associate the determined stroke length with the pair of intermediate positions, and control the drive system to move the hydrogen cylinder rod portion based upon the pair of intermediate positions to provide a third partial power stroke between the pair of intermediate positions.

In one or more embodiments of the low-pressure pump system the controller is further operably connected to a position indicator configured to provide a signal indicative of a position of the hydrogen cylinder rod portion within the hydrogen pump cylinder, and the controller is further configured to execute the program instructions to control the drive system based upon the signal indicative of the position of the hydrogen cylinder rod portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings.

FIG. 1 is a simplified schematic depiction of a hydrogen pumping system that is used to provide hydrogen to a vehicle or to transfer hydrogen from one reservoir or tank to another reservoir or tank;

FIG. 2 depicts a side perspective view of the first and second stage pump systems of FIG. 1 along with the bulk storage tank of FIG. 1;

FIG. 3 depicts a side perspective view of a low-pressure pump unit of FIG. 1;

FIG. 4 depicts a side cross sectional view of the low-pressure pump unit of FIG. 3;

FIG. 5 depicts a perspective view of the cold end portion of the low-pressure pump of FIG. 3;

FIG. 6 depicts a perspective cross sectional view of the cold end portion of FIG. 5;

FIG. 7 depicts a cross-sectional view of the intermediate portion of the low-pressure pump of FIG. 3;

FIG. 8 depicts a perspective view of the upper portion of the intermediate portion of the low-pressure pump of FIG. 3;

FIG. 9 depicts a perspective cross-sectional view of the upper portion of the intermediate portion of the low-pressure pump of FIG. 3;

FIG. 10 depicts a cross-sectional view of the warm end portion of the low-pressure pump of FIG. 3;

FIG. 11 depicts a simplified schematic view of a control system for the hydrogen pumping system of FIG. 1;

FIG. 12 depicts a schematic view of the drive system of FIG. 11 embodied as a hydraulic drive system;

FIG. 13 depicts a phase diagram used by the controller of FIG. 11;

FIG. 14 depicts a side cross sectional view of the low-pressure pump of FIG. 3 at the beginning of a power stroke with the presser component contacting the presser surface and the sealing member not sealed with the valve body;

FIG. 15 depicts a side cross sectional view of the low-pressure pump of FIG. 3 with the presser component not contacting the presser surface and the sealing member sealed with the valve body;

FIG. 16 depicts a side cross sectional view of the low-pressure pump of FIG. 3 with the presser component not contacting the presser surface and the sealing member sealed with the valve body after hydrogen or other fluid has been pressurized by a partial power stroke;

FIG. 17 depicts a side cross sectional view of the low-pressure pump of FIG. 3 with the presser component not contacting the presser surface and the sealing member sealed with the valve body after hydrogen or other fluid has been pressurized by a full power stroke;

FIG. 18 depicts a side cross sectional view of the low-pressure pump of FIG. 3 with the presser component not contacting the presser surface and the sealing member not sealed with the valve body after pressurized hydrogen or other fluid has moved the sealing member away from the valve body; and

FIG. 19 depicts a side cross sectional view of the low-pressure pump of FIG. 3 with the presser component contacting the presser surface and the sealing member not sealed with the valve body after the hydraulic drive system has moved the plunger downwardly.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written description. It is to be understood that no limitation to the scope of the disclosure is thereby intended. It is further to be understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the disclosure as would normally occur to one skilled in the art to which this disclosure pertains.

FIG. 1 is a simplified schematic depiction of a hydrogen pumping system 100 which in this embodiment is configured in part as a hydrogen pumping station to provide hydrogen to a vehicle 102, a vehicle 103, and/or a bulk storage tank 105. The hydrogen pumping system 100 includes a bulk storage tank 104, a low-pressure pump system 106, a second stage pump system 108, a ready storage tank 110, and a dispensing unit 112 fluidly connected to the ready storage tank 110 through a supply line 111. The dispensing unit 112 includes a nozzle 114 which is used to couple with a receiver 116 of the vehicle 102 to fill a hydrogen tank 118 of the vehicle 102.

The hydrogen pumping system 100 further includes an sLH2 pumping system with a dispensing unit 113 including a nozzle 115 which is used to couple with a receiver 117 of a vehicle 103 to fill a hydrogen tank 119 of the vehicle 103. The vehicle 103 in various embodiments is a motorcycle, a passenger vehicle, a truck, a heavy-duty truck, a train, a boat or ferry, an aircraft, or any desired vehicle. The low-pressure pump system 106 is in fluid connection with the dispensing unit 113 through a supply line 121.

In some embodiments, one or more of the bulk storage tank 105, the dispensing unit 112, and the dispensing unit 113 is omitted from the hydrogen pumping system 100. By way of example, in one embodiment the hydrogen pumping system 100 is incorporated into a vehicle 123 such as a transport vehicle which includes the bulk storage tank 104 which is configured to transport hydrogen. The low-pressure pump system 106, which may be located within the bulk storage tank 104 as indicted by the low-pressure pump system 106′, is used to move liquid hydrogen from the bulk storage tank 104 to a bulk storage tank of another hydrogen pumping system. In other embodiments, the hydrogen pumping system omits the bulk storage tank 105 and is configured to provide hydrogen to vehicles at high pressure and/or low pressure (sLH2).

Continuing with FIG. 1, the bulk storage tank 104 is configured to store liquid hydrogen at a pressure of 0 to 6 barg and a temperature of 18 to 25° K. The bulk storage tank 104 includes at least one port 120 which is used to supply liquid hydrogen to, and/or provide liquid hydrogen from, the bulk storage tank 104. Isolation valves 122 and 124 are used to selectively connect the port 120 to a supply line 126 or an input header 128 of the low-pressure pump system 106. In some embodiments the bulk storage tank 105 is configured similarly to the bulk storage tank 104.

Another isolation valve 130 is provided on the second stage supply header 132 between the low-pressure pump system 106 and the second stage pump system 108. Isolation valve 134 is provided on the supply line 111 between the ready storage tank 110 and the dispensing unit 112. Isolation valve 135 is provided on a supply line 136 between the low-pressure pump system 106 and the bulk storage tank 105. Isolation valve 137 is provided on the supply line 121 between the low-pressure pump system 106 and the dispensing unit 113. More or fewer valves may be incorporated into the system as desired for a particular configuration.

FIG. 2 shows some of the components of the hydrogen pumping system 100 in greater detail so as to further describe the low-pressure pump system. The low-pressure pump system in the embodiment of FIG. 2 is configured as a first stage pump system and in this embodiment includes a vessel 140 and three low-pressure pump units 142, 144, and 146. In other embodiments, more or fewer low-pressure pump units are provided. In some embodiments the vessel 140 is omitted. For example, in configurations wherein the low-pressure pump system 106 is incorporated into a transport vessel, the low-pressure pump system 106 can simply be positioned with the transport vessel which corresponds to the bulk storage tank 104.

Returning to FIG. 2, each of the three low-pressure pump units 142, 144, and 146 are connected to the second stage supply header 132 by a respective discharge pipe assembly 148, 150, and 152. The second stage supply header 132 supplies four second stage pump units 154, 156, 158, and 160 of the second stage pump system 108.

In the embodiment of FIG. 2, the low-pressure pump units 142, 144, and 146 share a common vessel 140 which is insulated. A dedicated insulated neck 162, 164, and 166 is provided by the vessel 140 for each of the low-pressure pump units 142, 144, and 146, respectively. Alternatively, each low-pressure pump is provided with a dedicated vessel. For example, FIGS. 3 and 4 depict a low-pressure pump unit 170 positioned within a vessel 172. The vessel 172 includes a dewar 174, also referred to as an insulation vessel, positioned about a fluid reservoir 176 which is supplied by an input header 178 as shown in FIG. 4. This configuration is particularly useful in embodiments with a single low-pressure pump unit. In some embodiments, the input header 178 is directly connected to the cold end portion 180 of the low-pressure pump unit 170 as indicated by the extension 179 and the fluid reservoir 176 is omitted. In embodiments wherein the low-pressure pump system 106 is located within the bulk storage tank 104, the dewar can be omitted.

The low-pressure pump units 142, 144, 146, and 170 are identical with the exception of connection geometry to the input header, reservoir, and second stage supply header and are described with reference to the low-pressure pump unit 170. As shown in FIG. 4, the low-pressure pump unit 170 incudes the cold end portion 180, an intermediate portion 182, and a warm end portion 184. The cold end portion 180, shown in further detail in FIG. 5, includes a hydrogen pump cylinder 186, fluidically connected to the fluid reservoir 176, and a pump head assembly 188. Two baffles 190 and 192 position the hydrogen pump cylinder 186 within the insulation vessel 174. The baffles 190 and 192 further interrupt movement of hydrogen in the fluid reservoir 176 to reduce thermal transfer between the top and bottom of the reservoir.

A fluid level detector 194, which is used in some embodiments to identify the level of liquid within the fluid reservoir 176, extends along the hydrogen pump cylinder 186 and is connected to a cold end portion flange 196. The fluid level detector 194 in some embodiments is a thermal probe. In some embodiments the fluid level detector 194 is additionally and/or alternatively in the form of an external tank level detector. An external tank level detector is particularly useful in determining whether gas is present in the hydrogen pump cylinder 186. In embodiments wherein the hydrogen pump cylinder 186 is not aligned with a vertical axis, more than one fluid level detector 194 may be incorporated to obtain fluid level information.

A vent line 198 and discharge pipe assembly 200 extend from the pump head assembly 188 through the cold end portion flange 196. The vent line 198 is in fluid communication with the hydrogen pump cylinder 186 and is configured to selectively vent non-hydrogen purge gas from the hydrogen pump cylinder 186. As discussed below, the vent line 198 is not used in normal operations. A thermal decoupling rod portion 202 extends outwardly from a thermal decoupling cylinder 204 which extends between the pump head assembly 188 and the cold end portion flange 196.

Referring to FIG. 6, the thermal decoupling cylinder 204 is inserted within an upper flange 210 of the pump head assembly 188. A hydrogen cylinder rod portion 212 is slidingly received within the thermal decoupling cylinder 204 and extends into the hydrogen pump cylinder 186. In this embodiment, the thermal decoupling rod portion 202 and the hydrogen cylinder rod portion 212 are integrally formed. A plunger assembly 214 is operably connected to the hydrogen cylinder rod portion 212 within the hydrogen pump cylinder 186. The plunger assembly 214 includes a plunger 216 and a presser 218. A sealing member 220, which in this embodiment is a circular sealing member 220, is positioned on and supported by the plunger 216. While in this embodiment the plunger 216, presser 218, and sealing member 220 are separately formed in other embodiments two or more of the components are integrally formed. The plunger 216 and presser 218 in one embodiment are fixedly positioned with respect to one another. In this embodiment each of the plunger 216 and presser 218 are separately operably connected to the hydrogen cylinder rod portion 212.

A guide 222 is operably connected to a lower portion of the hydrogen cylinder rod portion 212. A guide member 224 of the guide 222 is configured to slidingly engage an inner wall of the hydrogen pump cylinder 186. In one embodiment the guide 222 is configured as guide ring configured to center the hydrogen cylinder rod portion 212 within the hydrogen pump cylinder 186. The guide 222 has an open webbed construction which is designed to minimize turbulence in, and resistance to, a fluid flowing therethrough. The guide 222 maintains alignment of the hydrogen cylinder rod portion 212, and the components operably connected to the hydrogen cylinder rod portion 212, within the hydrogen pump cylinder 186. This allows the low-pressure pump unit 170 to be positioned at a non-zero angle with respect to the vertical axis. Consequently, in some embodiments the longitudinal axis 244 is angled up to 750 or more off of the vertical axis as discussed in further detail below.

A valve assembly 226 is optionally located at the inlet of the hydrogen pump cylinder 186. In some embodiments the valve assembly 226 is omitted. In other embodiments, the valve assembly 226 is controllable. In other embodiments the valve assembly 226 is spring operated.

A piston assembly 230 includes an upper guide member 232 and lower guide member 234, which slidingly engage the inner wall of the hydrogen pump cylinder 186, along with piston ring 236 and piston ring 238. A transfer member 240 of the piston assembly 230 includes a presser surface 242 axially aligned with the presser 218 along the longitudinal axis 244 of the hydrogen cylinder rod portion 212 and hydrogen pump cylinder 186. The transfer member 240 has an open webbed construction which is designed to minimize turbulence in, and resistance to, a fluid flowing therethrough.

The transfer member 240 is operably connected to a piston body 246 which receives the upper guide member 232, lower guide member 234, piston ring 236, and piston ring 238. The piston body 246 is hollow and defines a valve body 248, which in one embodiment is a circular valve body 248 and which is aligned with the sealing member 220 along the longitudinal axis 244. The distance between the lower surface of the valve body 248 which is configured to contact the upper surface of the sealing member 220 and the upper surface of the presser surface 242 which is configured to be contacted by a lower surface of the presser 218 is greater than the distance between the upper surface of the sealing member 220 and the lower surface of the presser 218 for reasons discussed below.

The upper surface of the piston body 246, the upper surface of the plunger 216, the inner wall of the hydrogen pump cylinder 186, and a lower surface of a valve manifold 250 of the pump head assembly 188 generally define a variable volume compression chamber 252. The valve manifold 250 holds at least one valve assembly 254 which in some embodiments are configured as a spring operated check valve. In some embodiments, the valve assembly 254 is controllably actuated.

The upper portion of the valve manifold 250 and the lower portion of the upper flange 210 define a plenum 262 which is in fluid communication with the variable volume compression chamber 252 through the at least one spring operated check valve assembly 254. The plenum 262 has a low-pressure pump unit outlet 263 in fluid communication with a discharge pipe 264 of the discharge pipe assembly 200 through a coupler 266. The coupler 266 provides a base for an insulation jacket 268 of the discharge pipe assembly 200.

A seal assembly 270 is received within the valve manifold 250. The hydrogen cylinder rod portion 212 extends through the seal assembly 270 and the rest of the pump head assembly 188 into the thermal decoupling cylinder 204 wherein the hydrogen cylinder rod portion 212 is coupled with the thermal decoupling rod portion 202 as shown in FIG. 7. The thermal decoupling cylinder 204 is coupled to a seal assembly 272 which extends through a cold end portion top plate 274. The cold end portion top plate 274 is fixedly connected to insulation vessel 174 and a lantern 276 is fixedly connected to the cold end portion top plate 274 as further shown in FIG. 8.

The discharge pipe assembly 200 extends through a seal assembly 278 (see FIG. 9) which extends through the cold end portion top plate 274. The thermal decoupling rod portion 202 extends through the seal assembly 272. The seal assembly 272 includes a pressure relief vent 280, for the seal assembly 272, best viewed in FIG. 9. A vapor barrier 282 is attached to the top of the seal assembly 272 (FIG. 7) and extends within the lantern 276 to the warm end portion 184. The vapor barrier 282 in one embodiment is in the form of a bellows and is positioned around the hydraulic rod 284 and/or the thermal decoupling rod portion 202. The thermal decoupling rod portion 202 extends through the seal assembly 272 where it is operably coupled to a drive system. In one embodiment, the operable coupling includes coupling the thermal decoupling rod portion 202 to a hydraulic rod 284 with a coupler 286.

As shown in FIG. 10, the hydraulic rod 284 extends through the lantern 276 and into a hydraulic cylinder 290 of a hydraulic pump 292. A hydraulic manifold 294 controllably provides hydraulic fluid to opposite sides of a hydraulic piston 296 fixedly attached to the hydraulic rod 284 to operate the low-pressure pump unit 170 as discussed in more detail below. A position indicator is included which provides a signal indicative of the position of the hydrogen cylinder rod portion 212 within the hydrogen pump cylinder 186. In some embodiments the position indicator senses the position of the hydrogen cylinder rod portion 212 directly. In some embodiments the position of the hydrogen cylinder rod portion 212 is sensed or otherwise indicted indirectly. In one embodiment the position indicator is a potentiometer 298 configured to provide precise position data associated with the hydraulic rod 284 and/or the hydraulic piston 296 in an embodiment wherein the hydraulic rod 284 is a drive rod of a drive system. In configurations in which the thermal decoupling rod portion 202 is configured as a drive rod the position of the thermal decoupling rod portion 202 may be indicated by the position indicator. The position indicator in various embodiments is configured as a sensor, an encoder, a transducer, a transformer, a potentiometer, or the like.

Returning to FIG. 1, the second stage pump system 108 is used to provide hydrogen to the ready storage tank 110 in a gaseous state at a high pressure of 400 to 950 barg and a temperature of −40 to −20 degrees C. (233 to 253K), or higher.

The hydrogen pumping system 100 is controlled by a control system 300 shown in FIG. 11. The control system 300 includes a controller 302 and a memory 304. The controller 302 is operably connected to the memory 304 which in some embodiments is separately provided and in other embodiments is part of the controller 302. Stored within the memory 304 are program instructions which, when executed by the controller 302, cause the hydrogen pumping system 100 to perform various operations such as refilling the bulk storage tank 104, transferring hydrogen, and filling the ready storage tank 110 as discussed in further detail below.

The controller 302 is operably connected to the other components of the hydrogen pumping system 100, including various pressure sensors 306 and temperature sensors 308 positioned throughout the hydrogen pumping system 100. The controller 302 further controls a drive system 310. In one embodiment the drive system 310 is a hydraulic drive system while in other embodiments the drive system is an electromagnetic drive system, ball screw drive system, or some other drive system. In embodiments wherein the drive system 310 is a hydraulic drive system, the drive system 310 may include the hydraulic manifold 294 and the potentiometer 298.

The drive system 310 is shown in simplified schematic form in FIG. 12. The drive system 310 includes the hydraulic pump 292. The hydraulic piston 296 separates the hydraulic cylinder 290 into a variable volume extension chamber 314 and a variable volume retraction chamber 316. The variable volume extension chamber 314 is connected by a discharge header 318 to a hydraulic motor assembly 320 and the variable volume retraction chamber 316 is connected the hydraulic motor assembly 320 by a discharge header 322.

The hydraulic motor assembly 320 includes a motor 324 and a fixed displacement pump 326 which in some embodiments is a swashplate type pump. A drain 328 is provided for the fixed displacement pump 326. A hydraulic volume source 330 maintains a minimum hydraulic pressure within the discharge headers 318 and 322 while relief assemblies 332 and 334 establish maximum possible pressures within the discharge headers 318 and 322, respectively. In some embodiments, the relief assembly 332 is set at a higher pressure than the relief assembly 334. The relief assemblies 332 and 334 discharge to a drain line 336. A pendulum volume container system 338 is fluidically connected to the discharge header 318 to account for volume changes in the system.

Various operations of the hydrogen pumping system 100 may be controlled in response to various inputs such as a user input, a low pressure reading from a pressure sensor 306 of the ready storage tank 110, and/or from a signal from the dispensing unit 112/113 indicating that the nozzle 114/115 has been connected to the receiver 116/117 and is being used, or is about to be used, to fill the tank 118/119. For example, the controller 302 in some embodiments receives a signal from the dispensing unit 112 indicating that an amount of fuel required to fill the hydrogen tank 118 will cause the ready storage tank 110 to drop below a threshold pressure so that the controller 302 can begin filling the ready storage tank 110 before the low-pressure threshold is reached.

The basic operation of the hydrogen pumping system by execution of the program instructions within the memory 304 to provide hydrogen to the ready storage tank 110, to provide hydrogen to the dispensing unit 113, or to provide hydrogen to the bulk storage tank 105 is common to each of the operations is described with reference to the following exemplary method wherein further details of the hydrogen pumping system 100 are provided.

Initially, the controller 302 receives a signal indicative of a fuel delivery request. Depending upon the particular scenario, this signal may originate from the ready storage tank 110, the dispensing unit 112, the vehicle 102, the dispensing unit 113, the vehicle 103, the bulk storage tank 105 or a user. Once the signal is received, the controller 302 determines a stroke length of the hydrogen cylinder rod portion 212 that will be needed to provide a delivery rate of fuel from the low-pressure pump system 106 that will be needed to satisfy the delivery request. In some embodiments, the determination of the stroke length is based upon one or more look-up tables stored within the memory 304.

In embodiments including more than one low-pressure pump unit 144, the controller 302 may perform an efficiency analysis to ascertain the optimal combination of low-pressure pump units 144 and associated stroke lengths. Even when only one low-pressure pump unit 144 is used, an efficiency analysis is performed. The efficiency analysis in some embodiments includes heat transfer analysis. As part of the analysis, the controller 302 will further identify specific travel locations of the hydrogen cylinder rod (or rods) 212 to optimize efficiency. For example, minimizing the amount of the hydrogen cylinder rod portion 212 which extends into the lantern 276 reduces heat added to the system from the environment. Additionally, as the low-pressure pump units 144 operate localized heat is generated by friction. Depending upon the particular scenario, it may beneficial for heat generated by, for example, the piston ring 236 and piston ring 238 to be generated at a location spaced apart from the lower end of the hydrogen pump cylinder 186.

In addition to heat transfer issues, the controller 302 accounts for the initial conditions within the hydrogen pump cylinder 186. For example, when the system is initially operated it is possible that some amount of gas is present within the hydrogen pump cylinder 186. Accordingly, the controller 302 receives a signal from the fluid level detector (or detectors) 194. Based upon the fluid level signals and/or pressure and temperature signals from the various pressure sensors 306 and temperature sensors 308, the controller 302 determines how much gas, if any, is present within the hydrogen pump cylinder 186. This informs the optimal stroke length, at least initially, to move the gas out of the hydrogen pump cylinder 186 into the into the plenum 262. Thus, while a heat analysis may indicate a partial initial stroke is all that is needed, a full stroke may be used, at least for an initial stroke, to move at least the majority of the gas into the plenum 262.

With the initial and subsequent stroke lengths determined, the controller 302 executes the program instructions to ensure proper preliminary conditions are met. In addition to ensuring adherence to various safety protocols, the controller 302 obtains pressure and temperature data from throughout the hydrogen pumping system 100 or at least from portions which will be involved in the movement of hydrogen. The controller 302 further establishes a valve line-up necessary for the operation. For example, when only charging the ready storage tank 110 the controller 302 controls the isolation valves 124 and 130 to open positions while ensuring that the valves 135 and 137 are shut. When filling is from only the bulk storage tank 104, the controller 302 further ensures that the isolation valve 122 is in the closed position. Depending upon whether the dispensing unit 112 is being used, the isolation valve 134 may be open or shut.

The controller 302 then controls the one or more low-pressure pumps in the low-pressure pump system 106 to provide a desired flow rate of hydrogen at a desired pressure using the determined stroke lengths. As discussed above, the desired flow rate and pressure is a function of the temperature of various components within the hydrogen pumping system 100 and is determined by the controller using, for example, look-up tables stored within the memory 304. In particular, when the controller initiates a refilling operation, various components within hydrogen pumping system 100 are warmer than the hydrogen stored within the bulk storage tank 104. If the hydrogen is warmed sufficiently relative to the pressure at a particular location within the hydrogen pumping system 100, the hydrogen will change to a vapor state which inhibits operation of, for example, the second stage pump(s) in the second stage pump system 108.

Additionally, during the filling operation the temperatures within the system change. For example, moving components will generate heat while the hydrogen will be cooling/heating the pipes/chambers depending upon the relative temperature of the components and the hydrogen at that point in the system. Thus, the controller 302 in one embodiment monitors temperatures and pressures throughout the hydrogen pumping system 100 during the entire refilling operation.

The controller 302 in one embodiment controls the low-pressure pump system 106 to subcool the hydrogen at the outlet of the low-pressure pump system 106 using a phase diagram stored in the memory 304. One such phase diagram is the phase diagram 350 shown in FIG. 13. As shown in FIG. 13, the hydrogen within the bulk storage tank 104 is stored at a pressure of about 0 to 2.5 barg and a temperature of 20 to 25K as indicated by the curve 352. Simply pumping the hydrogen without increasing pressure would move the hydrogen in the direction of the arrow 354 toward a gaseous state. Increasing the pressure of the hydrogen “subcools” the hydrogen by moving the curve 352 generally in the direction of the arrow 356. While some hydrogen pumping systems subcool to about the line 358, the controller 302 in one embodiment further controls the low-pressure pump system 106 to subcool the hydrogen at the outlet of the low-pressure pump system 106 to the curve 360. This results in potentially a 10 bar increase in pressure. In one embodiment, the hydrogen fluid is discharged from the low-pressure pump system 106 at a pressure of about 4-20 bar at a temperature of about 20-22 degrees Kelvin.

Operation of the low-pressure pump system 106 during a pumping operation is described with reference to low-pressure pump unit 170 and initial reference to FIG. 14. In FIG. 14 the controller 302 has controlled the drive system 310 to position the hydrogen cylinder rod portion 212 at its lowest level. In particular, if the hydrogen cylinder rod portion 212 is not already so positioned, the controller 302 controls the motor 324 to rotate while controlling the fixed displacement pump 326 to direct its output to the discharge header 318 as suction is taken on the discharge header 322. This increases the pressure in the variable volume extension chamber 314 while reducing pressure in the variable volume retraction chamber 316 causing the hydraulic rod 284 to move outwardly of the hydraulic cylinder 290.

Since the hydraulic rod 284 is coupled to the thermal decoupling rod portion 202 (see FIG. 7), the thermal decoupling rod portion 202 is forced downwardly causing the hydrogen cylinder rod portion 212 to move downwardly. This places the hydrogen cylinder rod portion 212 at its lowermost position. In this configuration, the guide 222 is at its lowest level and the presser 218 is in contact with the presser surface 242 of the transfer member 240. Additionally, the sealing member 220 is spaced apart from the valve body 248 along the longitudinal axis 244. Accordingly, liquid hydrogen within the fluid reservoir 176 (see FIG. 4) has flowed through the open webbed guide 222, through the transfer member 240, and through the valve body 248 of the hollow piston body 246 and into the variable volume compression chamber 252. In some embodiments, the system is configured to ensure the hydrogen pump cylinder 186 is completely filled.

In embodiments with a controllable valve assembly 254, the controller 302 controls the controllable valve assembly 254 to an open or unlocked configuration. The controller 302 further controls the drive system 310 to move the hydraulic rod 284 upwardly along the longitudinal axis 244 based upon the determined stroke length. In particular, the controller 302 controls the motor 324 to rotate while controlling the fixed displacement pump 326 to direct its output to the discharge header 322 as suction is taken on the discharge header 318. This increases the pressure in the variable volume retraction chamber 316 while reducing pressure in the variable volume extension chamber 314 causing the hydraulic rod 284 to move into the hydraulic cylinder 290 thereby causing the hydrogen cylinder rod portion 212 to move upwardly under tension along the longitudinal axis 244. Variations in the volume associated with the discharge header 318 are compensated by the pendulum volume container system pendulum volume container system 338, while leakage from the system is compensated by the hydraulic volume source 330.

The plunger 216 and presser 218, which are operably connected to the hydrogen cylinder rod portion 212, are thus moved upwardly along the longitudinal axis 244. The piston body 246, however, is not connected to the hydrogen cylinder rod portion 212 and thus does not move. In some embodiments the piston body 246 is buoyantly neutral to assist in allowing for separation from the presser 218. In any event, the further friction provided by the piston rings 236/238 is sufficient to allow for separation of the presser 218 from the transfer member 240.

Continued upward movement by the hydrogen cylinder rod portion 212 brings the sealing member 220 into sealing contact with the valve body 248 with which the sealing member 220 is aligned along the longitudinal axis 244 as shown in FIG. 15. Continued upward movement of the hydrogen cylinder rod portion 212 reduces the volume of the variable volume compression chamber 252 as the sealing member 220 is forced against the valve body 248 thereby increasing pressure of the hydrogen (or other fluid) within the variable volume compression chamber 252.

The pressure in the variable volume compression chamber 252 increases until the pressure within the variable volume compression chamber 252 equals the pressure within the plenum 262 and, in instances without a controllable check valve, the spring force of the at least one spring operated check valve assembly 254. At this time continued upward movement of the hydrogen cylinder rod portion 212 results in flow of hydrogen and/or gas through the at least one spring operated check valve assembly 254, into the plenum 262, and then through the discharge pipe assembly 200 (see FIG. 6).

Since the low-pressure pump unit 170 is vertically oriented, any gas which is present in the hydrogen pump cylinder 186 is directed toward and through the at least one spring operated check valve assembly 254. Thus, losses from boil-off of the hydrogen are eliminated. While the longitudinal axis 244 in some embodiments is aligned with the vertical axis, in other embodiments the vertical orientation of the longitudinal axis 244 is offset from the vertical axis by up to 750 or more. Larger offsets from the vertical axis are particularly beneficial in embodiments such as those incorporated into a transportation tank or truck, and embodiments wherein hydrogen is provided directing to the inlet (e.g., no fluid reservoir 176).

So long as the longitudinal axis 244 is not aligned with the horizontal axis and the longitudinal axis 244 is angled upwardly from the inlet of the hydrogen pump cylinder 186 to the upper flange 210 of pump head assembly, any bubbles in the system will migrate toward the upper flange 210 and the plenum 262. Additionally, since the inlet of the hydrogen pump cylinder 186 is the lowest portion of the hydrogen pump cylinder 186, the inlet is positioned in the coldest and most dense hydrogen in the fluid reservoir 176. This provides increased efficiency of the low-pressure pump system. Furthermore, since the inlet of the hydrogen pump cylinder is the lowest portion of the hydrogen pump cylinder 186, the inlet of the hydrogen pump cylinder will always be immersed in the fluid during steady state operation provided the system components are adequately sized. Consequently, there is no need for liquid level control in the fluid reservoir.

Moreover, as the sealed plunger assembly 214 and piston assembly 230 move upwardly within the hydrogen pump cylinder 186, a pressure differential is created within the hydrogen pump cylinder 186 between the location beneath the plunger assembly 214 and the inlet of the hydrogen pump cylinder 186 due to the upward movement of the sealed plunger assembly 214 and piston assembly 230. Consequently, fuel is drawn into the hydrogen pump cylinder 186, filling the hydrogen pump cylinder 186 behind the sealed plunger assembly 214 and piston assembly 230. Preferably a sufficiently high overpressure is maintained within the hydrogen pump cylinder 186 such as by fluid level within the supply to the hydrogen pump cylinder 186 or a pressure source operably connected to the fuel supply to prevent the hydrogen beneath the sealed plunger assembly 214 and piston assembly 230 from flashing to a gaseous state.

The above-described configuration ensures that any gas above the sealed plunger assembly 214 and piston assembly 230 is located at the uppermost portion of the hydrogen pump cylinder 186. This optimizes the potential for charging any gas within the hydrogen pump cylinder 186 into the plenum 262, thereby eliminating the need to use a vapor return line (e.g., vent line 198) to vent the gasses during pumping operations. Since gas is not vented, the efficiency of the system is increased.

Additionally, since the low-pressure pump unit is configured to force any gas into the plenum 262, the low-pressure pump unit can be used as a boil-off pump to remove vapor from top of storage tank and move it to a tank or to a second stage pump. This provides for transfer of additional hydrogen after the liquid hydrogen is emptied from a storage/transport tank reducing the amount of hydrogen which is not pumped thereby providing cost savings. The configuration further enables the use of the low-pressure pump unit to cool the pump prior to operation.

Since the low-pressure pump unit is configured to move gas into the plenum 262, the low-pressure pump unit is particularly well-adapted for use in a system which is designed to operate with some amount of gas in the second stage pump system. One such system is described in U.S. application Ser. No. 18/636,132, filed Apr. 15, 2024, the contents of which are incorporated herein by reference.

The low-pressure pump system is configured to provide sufficient hydrogen to the second stage supply header 132 to allow the second stage pump system 108 to operate at or near full capacity. Accordingly, if the demand identified by the controller 302 is less than full capacity for the second stage pump system 108, the controller 302 controls the drive system 310 to provide only the required amount of hydrogen while optimizing efficiency of the system based upon the stroke length determination described above. Accordingly, for less than full capacity for the second stage pump system 108 the controller 302 controls the drive system 310 in some embodiments to provide a partial power stroke for the low-pressure pump unit 170, typically after a full stroke to empty any gas within the hydrogen pump cylinder 186, such as the partial power stroke shown in FIG. 16. In FIG. 16, the volume of the variable volume compression chamber 252 is about half the volume of the variable volume compression chamber 252 in FIG. 15, but the piston assembly 230 is spaced apart from the the valve manifold 250.

In systems which do not incorporate shorter strokes, or when the system is operating at or near full capacity, the upward movement of the piston assembly 230 continues until the volume of the variable volume compression chamber 252 is at its minimum with the hydrogen cylinder rod portion 212 at its uppermost position. Consequently, the piston assembly 230 and plunger assembly 214 are immediately adjacent the valve manifold 250 as shown in FIG. 17. In some embodiments, a potentiometer or other position indicator associated with the hydraulic rod 284 is used to provide precise control of the drive system 310 to minimize the volume of the variable volume compression chamber 252.

In both the configuration of FIG. 16 and in the configuration of FIG. 17, once the upward movement of the piston assembly 230 terminates, the controller 302 controls the drive system 310 to force the hydrogen cylinder rod portion 212 to begin moving downwardly along the longitudinal axis 244. In particular, the controller 302 controls the motor 324 to rotate while controlling the fixed displacement pump 326 to direct its output to the discharge header 318 as suction is taken on the discharge header 322. This increases the pressure in the variable volume extension chamber 314 while reducing pressure in the variable volume retraction chamber 316 causing the hydraulic rod 284 to move outwardly of the hydraulic cylinder 290 thereby causing the hydrogen cylinder rod portion 212, and the plunger assembly 214, to move downwardly along the longitudinal axis 244.

As noted above, the piston body 246 is not connected to the hydrogen cylinder rod portion 212 and thus does not move as the plunger assembly 214 moves due to friction provided by the piston rings 236/238 and/or neutral buoyancy. As described above, overpressure is typically maintained within the hydrogen pump cylinder 186 such as by fluid level within the supply to the hydrogen pump cylinder 186 or a pressure source operably connected to the fuel supply. In addition to preventing the hydrogen beneath the sealed plunger assembly 214 and piston assembly 230 from flashing to a gaseous state, the overpressure prevents movement of fluid within the hydrogen pump cylinder 186 out of the inlet of the hydrogen pump cylinder 186 keeping the hydrogen pump cylinder 186 full of liquid.

In embodiments which do not provide such overpressure, the valve assembly 226 may be incorporated. Consequently, as the sealing member 220 moves away from the valve body 248 in these embodiments, the pressure within the hydrogen pump cylinder 186 beneath the plunger assembly 214 increases. This seals the valve assembly 226. Accordingly, the hydrogen fluid which was sucked into the hydrogen pump cylinder 186 during the upward movement of the piston assembly 230 is trapped within the hydrogen pump cylinder 186. Consequently, even if the fluid level in the fluid reservoir 176 is lower than the top of the hydrogen pump cylinder 186, the hydrogen pump cylinder 186 remains full as the hydrogen cylinder rod portion 212 moves downwardly.

In either scenario, because the distance between the lower surface of the valve body 248 and the upper surface of the presser surface 242 is greater than the distance between the upper surface of the sealing member 220 and the lower surface of the presser 218, the piston assembly 230 initially remains at or about the same location in the hydrogen pump cylinder 186 as shown in FIG. 18 as the plunger assembly 214 moves downwardly.

The presser 218 is aligned with the presser surface 242 along the longitudinal axis 244. Accordingly, continued movement of the hydrogen cylinder rod portion 212 downwardly along the longitudinal axis 244 brings the presser 218 into contact with the presser surface 242 as shown in FIG. 19. Continued movement of the hydrogen cylinder rod portion 212 from this configuration forces the piston assembly downwardly through the fluid within the hydrogen pump cylinder 186 until the system is once again positioned as shown in FIG. 14.

While the above description introduced partial strokes while discussing movement of the hydrogen cylinder rod portion 212 from the position of FIG. 14 to the position of FIG. 16, the ability to finely control the position of the hydrogen cylinder rod portion 212 using the drive system 310 allows for partial strokes to be made between any desired locations in the hydrogen pump cylinder 186. Thus, in addition to partial strokes between the positions of FIGS. 14 and 16 (the lower portion of the hydrogen pump cylinder 186), partial strokes can be provided which move between the locations of FIGS. 16 and 17 (the upper portion of the hydrogen pump cylinder 186), as well as any desired pair of intermediate positions such as the positions of FIGS. 15 and 16 (mid-portions of the hydrogen pump cylinder 186).

The low-pressure pump system 106 thus provides hydrogen to any desired receptor including the second stage supply header 132 for further pressurization by the second stage pump system 108 for storage in the ready storage tank 110 and/or for provision to the dispensing unit 112, the dispensing unit 113, or the bulk storage tank 105.

While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the disclosure are desired to be protected. By way of example, while the system described above is a vertically oriented system, many of the improvements can be incorporated into systems with other orientations such as horizontal orientations.