Patent ID: 12212214

Like reference symbols in the various drawings indicate like elements. Drawings not to scale.

DETAILED DESCRIPTION

The turboexpander described herein can be used for various hydrogen applications. The turboexpander can process high pressure hydrogen and convert the pressure energy into electricity for a variety of uses. Applications where the turboexpander can be implemented include: pipeline distribution pressure let down, hydrogen production, hydrogen fuel gas for gas turbines or combustion engines, hydrogen dispensing from trailers, and hydrogen liquefaction. Each of these applications provides a sufficient pressure drop and flow to operate and produce energy using the turboexpander described herein.

The power grid that the turboexpander can supply power to (and draw power from) can be a national or regional power grid, a local power grid for a city or district, or a small grid, local grid, or microgrid, such as an on-site grid that supplies power to a building, campus, industrial manufacturing or processing plant, or neighborhood.

FIG.1is a schematic diagram of an electric power generation system100coupled to a power grid140in accordance with embodiments of the present disclosure. The electric power generation system100can be added at a PLD station to capture energy from gas expansion from the PLD process, or in any of the other applications described above. The electric power generation system100includes a turboexpander102in parallel with a pressure control valve130. The turboexpander102is arranged axially so that the turboexpander102can be mounted in-line with a pipe. The turboexpander102acts as an electric generator by generating electrical energy from rotational kinetic energy derived from expansion of a gas through a turbine wheel104. For example, rotation of the turbine wheel104can be used to rotate a rotor108within a stator110, which then generates electrical energy.

FIG.1is a schematic diagram of an electric power generation system100coupled to a power grid140in accordance with embodiments of the present disclosure. The electric power generation system100can be added at a PLD station to capture energy from gas expansion from the PLD process. The electric power generation system100includes a turboexpander102in parallel with a pressure control valve130. The turboexpander102is arranged axially so that the turboexpander102can be mounted in-line with a pipe. The turboexpander102acts as an electric generator by generating electrical energy from rotational kinetic energy derived from expansion of a gas through a turbine wheel104. For example, rotation of the turbine wheel104can be used to rotate a rotor108within a stator110, which then generates electrical energy.

The turboexpander102is shown to have the process gas flow through the system, which cools the generator section and eliminates the need for auxiliary cooling equipment. In some embodiments, non-flow-through overhung systems can also be implemented. The power electronics118for turboexpander combines a Variable Speed Drive (VSD)166and Magnetic Bearing Controller (MBC)168into one cabinet, in some implementations. The VSD allows for a consistent and clean delivery of generated power from the turboexpander102to a power grid140. The VSD166regulates the frequency and amplitude of the generated current to match the local grid. After expansion, the gas exits the turboexpander102along the same axial path for downstream processes.

The turboexpander102is shown as having a flow-through configuration. The flow-through configuration permits process gas to flow from an inlet side of the turboexpander102to an outlet side of the turboexpander102. The gas flows into a radial gas inlet154to a turbine wheel104and an axial gas outlet156from the turbine wheel104. The gas then flow through the generator and out of the outlet156, where the gas rejoins the gas pipeline170. Generally, high pressure process gas120is directed to flow into the turboexpander102through a flow control system126. The flow control system126includes a flow or mass control valve and an emergency shut off valve. Flow control system126can be controlled electrically from power electronics118by control line164. In embodiments, the turboexpander housing112is hermetically sealed. As mentioned above, the turboexpander can be non-flow-through and overhung without deviating from the scope of this disclosure. The high pressure process gas120is expanded by flowing through the turbine wheel104, resulting in a pressure letdown of the process gas. Lower pressure process gas128exits the turboexpander. The expansion of the high pressure process gas120through the turbine wheel104causes the turbine wheel104to rotate, which causes the rotor108to rotate. The rotation of the rotor108within the stator110generates electrical energy. The turboexpander102achieves the desired pressure letdown and captures the energy from the pressure letdown to generate electricity. A pressure control valve130, such as a conventional pressure regulator, can be installed in parallel to the turboexpander102. The pressure control valve130can be used to control the pressure of the high pressure process gas120that flows through the turboexpander. Any excess high pressure process gas that is not directed into the turboexpander can be directed through the pressure control valve130. In addition, upon deactivation of the turboexpander102, flow control system126can shut off process gas flow to the turboexpander. In that case, the pressure control valve130can be set to perform the pressure let-down for the high-pressure gas for downstream distribution and consumption.

The flow control system126can include a pressure relief valve, flow control valve, an emergency shut-off valve, etc. The flow control system126can use one or more valves to control the pressure of the hydrogen entering the turbine wheel104to achieve both a desired turbine wheel speed (and resulting electrical output) and a desired hydrogen output pressure from the turboexpander102.

In some embodiments, a heater122can heat the high pressure process gas120prior to flowing the gas into the turboexpander102. For example, if the expansion of the gas through the turbine wheel104lowers the temperature of the process gas to a point where moisture in the gas freezes at the turbine wheel or other downstream locations in the pipeline, the pressurized process gas120can be heated by heater122. (Heated) high pressure process gas124can then be directed into the turboexpander102. The heating of the process gas can prevent freezing moisture as the gas expands and its temperature drops.

The turboexpander102includes a turbine wheel104. The turbine wheel104is shown as a radial inflow turbine wheel, though other configurations are within the scope of this disclosure, such as axial flow turbine wheels. In this example, heated high pressure process gas124is received from an inlet conduit150of the housing112enters a radially oriented inlet154of the turbine wheel104. In certain embodiments, the fluid flows through an inlet conduit150and is diverted by a flow diverter to a radial inlet154that directs the flow into the radial inflow of the turbine wheel104. After expanding, the lower pressure process gas exits the turbine wheel104from an axially oriented outlet156to outlet conduit152of the housing112.

The turbine wheel104can be directly affixed to the rotor108, or to an intermediate common shaft, for example, by fasteners, rigid drive shaft, welding, or other manner. For example, the turbine wheel104may be received at an end of the rotor108, and held to the rotor108with a shaft. The shaft threads into the rotor108at one end, and at the other, captures the turbine wheel104between the end of rotor108and a nut threadingly received on the shaft. The turbine wheel104and rotor108can be coupled without a gearbox and rotate at the same speed. In other instances, the turbine wheel104can be indirectly coupled to the rotor108, for example, by a gear train, clutch mechanism, or other manner.

The turbine wheel104includes a plurality of turbine wheel blades106extending outwardly from a hub and that react with the expanding process gas to cause the turbine wheel104to rotate.FIG.1shows an unshrouded turbine wheel, in which each of the turbine blades106has an exposed, generally radially oriented blade tip extending between the radial inlet154and axial outlet156. As discussed in more detail below, the blade tips substantially seal against a shroud114on the interior of the housing112. In certain instances, the turbine wheel104is a shrouded turbine wheel.

In configurations with an un-shrouded turbine wheel104, the housing112includes an inwardly oriented shroud114that resides closely adjacent to, and at most times during operation, out of contact with the turbine wheel blades106. The close proximity of the turbine wheel blades106and shroud114substantially seals against passage of process gas there between, as the process gas flows through the turbine wheel104. Although some amount of the process gas may leak or pass between the turbine wheel blades106and the shroud114, the leakage is insubstantial in the operation of the turbine wheel104. In certain instances, the leakage can be commensurate with other similar unshrouded-turbine/shroud-surface interfaces, using conventional tolerances between the turbine wheel blades106and the shroud114. The amount of leakage that is considered acceptable leakage may be predetermined. The operational parameters of the turbine generator may be optimized to reduce the leakage. In embodiments, the housing112is hermetically sealed to prevent process gases from escaping the radial inlet154of the turbine wheel104.

The shroud114may reside at a specified distance away from the turbine wheel blades106, and is maintained at a distance away from the turbine wheel blades106during operation of the turboexpander102by using magnetic positioning devices, including active magnetic bearings and position sensors.

The turboexpander102can include a high-performance, high-speed permanent magnet generator. In certain embodiments, the turboexpander102includes a radial in-flow expansion turbine wheel104. Turboexpander102can also include low loss active magnetic bearings (AMBs)116a,b. The rotor assembly can include permanent magnet section with the turbine wheel104mounted directly to the rotor hub. The rotor108can be levitated by the magnetic bearing system creating a frictionless (or near frictionless) interface between dynamic and static components. The AMBs116a,bfacilitate a lossless (or near lossless) rotation of the rotor108.

Bearings116aand116bare arranged to rotatably support the rotor108and turbine wheel104relative to the stator110and the shroud114. The turbine wheel104is supported in a non-cantilevered manner by the bearings116aand116b. In embodiments, the turbine wheel104may be supported in a cantilevered manner and bearings116aand116bmay be located on the outlet side of turbine wheel104. In certain instances, one or more of the bearings116aor116bcan include ball bearings, needle bearings, magnetic bearings, foil bearings, journal bearings, or others.

Bearings116aand116bmay be a combination radial and thrust bearing, supporting the rotor108in radial and axial directions. Other configurations could be utilized. The bearings116aand116bneed not be the same types of bearings.

In the embodiments in which the bearings116aand116bare magnetic bearings, a magnetic bearing controller (MBC)168is used to control the magnetic bearings116aand116b. Position sensors117a,117bcan be used to detect the position or changes in the position of the turbine wheel104and/or rotor108relative to the housing112or other reference point (such as a predetermined value). Position sensors117a,117bcan detect axial and/or radial displacement. The magnetic bearing116aand/or116bcan respond to the information from the position sensors117a,117band adjust for the detected displacement, if necessary. The MBC168may receive information from the position sensor(s)117a,117band process that information to provide control signals to the magnetic bearings116a,116b. MBC168can communicate with the various components of the turboexpander102across a communications channel162.

The use of magnetic bearings116a,116band position sensors117a,117bto maintain and/or adjust the position of the turbine wheel blades106such that the turbine wheel blades106stay in close proximity to the shroud114permits the turboexpander102to operate at high efficiencies. The use of the active magnetic bearings116a,bin the turboexpander102eliminates physical contact between rotating and stationary components, as well as eliminate lubrication and lubrication systems. In some embodiments, brush seals can be used to prevent gas leakage. The magnetic bearings116a,band position sensors117a,ballow for the rotor to stay in close proximity to the brush seals157.

The turboexpander102may include one or more backup bearings. For example, at start-up and shut-down or in the event of a power outage that affects the operation of the magnetic bearings116aand116b, bearings may be used to rotatably support the rotor108during that period of time. The backup bearings and may include ball bearings, needle bearings, journal bearings, or the like. As mentioned previously, the turboexpander102is configured to generate electricity in response to the rotation of the rotor108. In certain instances, the rotor108can include one or more permanent magnets. The stator110includes a plurality of conductive coils. Electrical current is generated by the rotation of the magnet within the coils of the stator110. The rotor108and stator110can be configured as a synchronous, permanent magnet, multiphase alternating current (AC) generator. The bi-directional electrical connection160can include a three-phase output, for example. The bi-directional electrical connection160can facilitate conveyance of (e.g., 3 phase) power output from the generator and can also supply power to the generator for start-up (e.g., to cause the rotor to begin rotating while process gas or other working fluid pressure builds up and can spin the rotor108and turbine wheel104). In certain instances, stator110may include a plurality of coils (e.g., three or six coils for a three-phase AC output). When the rotor108is rotated, a voltage is induced in the stator coil. At any instant, the magnitude of the voltage induced in coils is proportional to the rate at which the magnetic field encircled by the coil is changing with time (i.e., the rate at which the magnetic field is passing the two sides of the coil). In instances where the rotor108is coupled to rotate at the same speed as the turbine wheel104, the turboexpander102is configured to generate electricity at that speed. Such a turboexpander102is what is referred to as a “high speed” turbine generator. For example, in embodiments, the turboexpander102can produce up to 280 kW at a continuous speed of 30,000 rpm. In embodiments, the turboexpander can produce on the order of 350 kW at higher rotational speeds (e.g., on the order of 35,000 rpm).

In some embodiments, the design of the turbine wheel104, rotor108, and/or stator110can be based on a desired parameter of the output gas from the turboexpander102. In some embodiments, the design of the turbine nozzle155can also be based on a desired parameter of the output gas from the turboexpander102. For example, the design of the turbine nozzle and turbine wheel can be based on a desired temperature of the gas128.

The turboexpander102can be coupled to a power electronics118. Power electronics118can include a variable speed drive (VSD)166(or variable frequency drive) and the magnetic bearing controller (MBC)168(discussed above).

The bi-directional electrical connection160of the turboexpander102is connected to the VSD166, which can be programmed to specific power requirements. The VSD166can include an insulated-gate bipolar transistor (IGBT) rectifier208to convert the variable frequency, high voltage output from the turboexpander102to a direct current (DC). The rectifier208can be a three-phase rectifier for three-phase AC input current. An inverter210then converts the DC from the rectifier AC for supplying to the power grid140. The inverter210can convert the DC to 380 VAC-480 VAC at 50 to 60 Hz for delivery to the power grid140. The specific output of the VSD166depends on the power grid and application. Other conversion values are within the scope of this disclosure. The VSD166matches its output to the power grid140by sampling the grid voltage and frequency, and then changing the output voltage and frequency of the inverter to match the sampled power grid voltage and frequency. In embodiments, rectifier208and inverter210are bi-directional, so that power from the grid140can be supplied to the turboexpander102. Power from the grid140can be used to start rotation of the rotor108within the stator110during start-up.

The turboexpander102is also connected to the MBC168in the power electronics118. The MBC168constantly monitors position, current, temperature, and other parameters to ensure that the turboexpander102and the active magnetic bearings116aand116bare operating as desired. For example, the MBC168is coupled to position sensors117a,117bto monitor radial and axial position of the turbine wheel104and the rotor108. The MBC168can control the magnetic bearings116a,116bto selectively change the stiffness and damping characteristics of the magnetic bearings116a,116bas a function of spin speed. The MBC168can also control synchronous cancellation, including automatic balancing control, adaptive vibration control, adaptive vibration rejection, and unbalance force rejection control.

Pressure let down systems convert kinetic energy from the process flow into shaft power. The turboexpander can support islanding operations. The turboexpander can continue to provide power to a location in the event that a power grid supplying power to that location is interrupted. This disclosure describes components that can facilitate load matching between the shaft power converted from the process gas flow at the pressure letdown station to load demands. In this way, the turboexpander can support microgrid functionality for islanding operations.

The turboexpander102described above includes example features that are implementation-specific. Certain features may be changed, added, removed, or redesigned without deviating from the scope of this disclosure. For example, other types of bearings can be used instead of or in addition to AMBs, such as ball bearings, fluid film bearings, etc. Different designs of rotors and stators can be used, such as brushless DC, induction-type, etc. Other types of stator cooling architectures can be used, such as non-flow-through and overhung architectures.

Distribution pipelines contain the highest gas flow rates in the distribution network and therefore offer the highest power potential for turboexpander-based pressure reduction. Both natural gas and hydrogen pressure reduction stations can utilize multiple turboexpander units in parallel to maximize power production (though one turboexpander is shown in the figures). Potential power generation in high-flow applications can yield up to 3 megawatts (MW) of power potential, the equivalent of about 12,000 tons of CO2e emissions offset annually.

Hydrogen is compressed for traversal through a pipeline and the pressure of the hydrogen will be reduced along the pipeline, as hydrogen flows from high pressure to low pressure. During distribution pressure drops (e.g., using pressure letdown (PLD) or pressure reduction stations (PRS)), usable energy can be recovered by the turboexpander102to generate clean electricity. Such a topology is illustrated generally byFIG.1described above and more specifically byFIG.2.

FIG.2is a schematic diagram of a hydrogen pressure letdown system200that includes a turboexpander102in accordance with embodiments of the present disclosure. The hydrogen pressure letdown system200includes a turboexpander102or similar turboexpander. The turboexpander102receives high-pressure hydrogen gas222from a pipeline, for example, as part of a hydrogen gas pressure letdown process. The high-pressure hydrogen gas can enter a turbine wheel of the turboexpander. The high-pressure hydrogen gas can cause the turbine wheel to rotate, thereby rotating a rotor within a stator. Rotation of the rotor within the stator can generate electrical current. The electrical current can be output from the turboexpander to a power electronics118. Power electronics118can convert the electrical current to be compatible with the grid140or other electrical loads. This electricity can be consumed on-site by the facility, consumed on-site in some energy intensive process such as green hydrogen production, or sold to the local energy utility creating a revenue stream for the pipeline owner.

High-pressure hydrogen gas222can traverse a pipeline and enter the hydrogen pressure letdown system200. The hydrogen pressure letdown system200includes a flow control system (e.g., flow control system126ofFIG.1) and a pressure control valve130(also shown inFIG.1). The flow control system126can include a flow control valve (FCV)240and an emergency shutoff valve (ESV)242. FCV240can control the pressure of the flow of the high-pressure hydrogen gas222that enters the turboexpander102. The flow rate of the high-pressure hydrogen gas222can be controlled by the FCV240based on the size of the turbine wheel104and the desired power output of power electronics118; the rotational speed of the rotor108can be determined based on the desired rotordynamic performance of the rotor108. The FCV240can be controlled manually or electronically. The FCV240, for example, can be controlled electronically based on information about the power output in power electronics118. If the power output is too low, FCV240can be adjusted to increase flow rate of high-pressure hydrogen gas222input to the turboexpander102to increase the torque of rotor108; conversely, if power output is too high, FCV240can be adjusted to decrease flow rate of high-pressure hydrogen gas222input to the turboexpander102to decrease the torque of rotor108.

The flow control system126can also include ESV242. ESV242can close quickly to prevent high-pressure hydrogen gas222from entering the turboexpander102during emergency situations. Emergency situations can include rotor over-speed conditions, hydrogen gas leaks, fault conditions at the power electronics118or grid140or elsewhere (which can cause rotor over-speed), or other emergency situations.

The turboexpander102can expand the high-pressure hydrogen gas222, resulting in low (or lower) pressure hydrogen gas224. The low-pressure hydrogen gas224can be directed to downstream pipelines or elsewhere for distribution. The expansion of the high-pressure hydrogen gas222by the turbine wheel104of the turboexpander102results in the generation of electrical current. The electrical current can be output by the turboexpander102through bi-directional electrical connection160to power electronics118. Power electronics118can convert the generated electrical current into a form compatible with intended consumers of the electrical current. For example, power electronics118can change the amplitude and frequency of the generated electrical current to be compatible with supplying power to grid140or to electrical loads.

The power electronics118can include a variable speed drive (VSD)206. VSD206can include circuitry that can change electrical current to suit a specific load or the grid. For example, the VSD206can include circuitry that can convert the generated electrical current from AC to DC (e.g., a rectifier circuit) and from DC to AC (e.g., inverter circuit). The VSD206can include a bi-directional inverter212to allow the turboexpander to receive power from the grid for start-up. The VSD206can also include circuitry to change the waveform of the generated electrical current to conform the electrical current to have a frequency and amplitude compatible with the power grid140. Other electrical circuits are also contemplated and are within the scope of this disclosure.

The power electronics118can include a brake resistor assembly202. The brake resistor assembly202can be used to oppose run-away current generation during rotor over-speed conditions to slow the rotor rotation speed to prevent damage to the rotor. The brake resistor assembly202can be coupled to the bi-directional electrical connection160by a contactor204. Contactor204can close the circuit between the turboexpander power output and the brake resistor quickly to protect the rotor based on the detection220of an over-speed condition. The brake resistor assembly202impedance can be selected (or tuned) based on the power output of the turboexpander. The brake resistor assembly202can include a plurality of resistors (and in some cases resistors and capacitors). Though shown as part of the power electronics118, it is understood that the brake resistor assembly202and contactor204can be directly connected to the output of the turboexpander102, to reduce the latency between detecting the fault condition responsible for rotor over-speed and the closing of the contactor204.

FIG.3is a process flow diagram300for operating a turboexpander for high-pressure hydrogen gas pressure letdown in accordance with embodiments of the present disclosure. High-pressure hydrogen gas is input into turbine wheel of turboexpander (302). The high-pressure hydrogen gas input into the turbine wheel can cause the turbine wheel to rotate, which causes a rotor to rotate within a stator (304). The turbine wheel also expands the high-pressure hydrogen gas, thereby lowering the pressure of the hydrogen gas. This low (or lower)-pressure hydrogen gas is output from the turboexpander for downstream distribution and consumption (306).

The electrical current generated by the turboexpander can be output to a power electronics system. The power electronics can adjust the electrical current to be a form compatible with the intended load(s) or for supplying to the grid (308). The power electronics system can output the adjusted electrical current to the intended load(s) or to the grid (310).

It is understood that the order of operations shown inFIG.3(or in other process flow figures described herein) can be performed in a different order. Some processes are performed in parallel. For example, the turboexpander will generate electrical current once the turboexpander rotor is rotating at a certain speed with a certain torque. The flow of the hydrogen gas can be continuous, which maintains the desired power output from the power electronics. While the rotor is spinning at the desired speed, the expanded hydrogen gas is output from the turboexpander and directed downstream and the electrical current is output from the power electronics. These processes of generating electrical current by the turboexpander from expansion of high-pressure hydrogen gas can continue until the system is shut down for whatever reason.

The pressure letdown application shown inFIG.2can be used in combination with other hydrogen applications. Generally, the turboexpander102can be used to expand high-pressure hydrogen gas222and output lower pressure hydrogen gas224and generate electrical current.

FIG.4is a schematic diagram of a hydrogen-based power station400that includes a turboexpander102in accordance with embodiments of the present disclosure. Hydrogen is used to generate power in gas turbines (such as gas turbine410) and fuel cells (such as fuel cell412). Both applications use large volumes of hydrogen, which can be supplied by on-site storage or by a co-located production facility via pipeline. The pipeline or storage pressure is reduced (or let down) before the hydrogen enters the gas turbine410or fuel cell412. The turboexpander102can be used to recover energy from pressure reduction of the hydrogen fuel gas.

In some circumstances, the volumetric flow rate in these applications can be on the order of 1,000 to 5,000 Nm3/h. The potential recoverable power ranges from 10 kW up to 300 kW, which can be enough to improve overall plant efficiency. One example use for the generated power is to offset the electrical demand of the facility. The economic benefit or return on investment can then be evaluated using the retail price of electricity rather than the wholesale price for selling the electricity to the grid.

At the outset, high-pressure hydrogen gas404is delivered to the hydrogen-based power station400from a hydrogen fuel gas source402. The hydrogen fuel gas source can include a hydrogen storage tank or a hydrogen pipeline. The hydrogen-based power station400includes a flow control system126and a pressure control valve130. As mentioned before, flow control system126includes a FCV240and ESV242. Flow control system126can control the flow of high-pressure hydrogen fuel gas404into the turbine wheel104of the turboexpander102. The turbine wheel104of the turboexpander102can expand and reduce the pressure of the high-pressure hydrogen fuel gas404. The low (or lower)-pressure hydrogen fuel gas406can be supplied to a hydrogen-based power system408, such as a gas turbine410or fuel cell412. The hydrogen-based power system408can provide power to the grid or to one or more loads.

The energy reclaimed from the pressure letdown of the high-pressure hydrogen fuel gas404by the turbine wheel104is used to generate electrical current. The expansion of the high-pressure hydrogen fuel gas404causes the turbine wheel104to rotate, thereby rotating a rotor108. Rotation of the rotor108within the stator110generates electrical current. The electrical current can be used to power certain loads, such as those at the power station facility; or the electrical current can be used to supply power to the grid. For example, electrical current generated by the turboexpander102can be directed to a power electronics118(described above). Power electronics118can include circuitry to condition the generated electrical current to be compatible with the load(s) or the grid. The power electronics118can also condition the power generated by the turboexpander102to have a frequency and amplitude compatible with the gas turbine410or the fuel cell412.

FIG.5is a process flow diagram for expanding hydrogen fuel gas using a turboexpander in accordance with embodiments of the present disclosure. High-pressure hydrogen fuel gas is input into turbine wheel of turboexpander (502). The high-pressure hydrogen fuel gas input into the turbine wheel can cause the turbine wheel to rotate, which causes a rotor to rotate within a stator (504). The turbine wheel also expands the high-pressure hydrogen fuel gas, thereby lowering the pressure of the hydrogen fuel gas. This low (or lower)-pressure hydrogen fuel gas is output from the turboexpander for downstream distribution and consumption (506).

The electrical current generated by the turboexpander can be output to a power electronics. The power electronics can condition the electrical current to be compatible with the intended load(s) or for supplying to the grid (508). The power electronics can output the adjusted electrical current to the intended load(s) or to the grid (510).

FIG.6Ais a schematic diagram for a hydrogen fueling station600that includes a turboexpander in accordance with embodiments of the present disclosure. Hydrogen gas can be transported from a starting point to hydrogen fueling station600via bulk delivery trailers. Hydrogen gas is offloaded from the hydrogen gas trailer container602to onsite storage614at the fueling station600, where the hydrogen gas is stored until it is dispensed to consumers' vehicles. The use of trailers for transporting hydrogen gas is useful while a global hydrogen pipeline infrastructure is being constructed and implemented.

These bulk trailers deliver gaseous hydrogen604at high pressure (˜700-bar) which is bled into a storage container614at the hydrogen fueling station600. This process includes expansion of high-pressure hydrogen gas604. In embodiments of this disclosure, turboexpander102can be used to control the expansion of the high-pressure hydrogen gas604from the trailer container602and reclaim energy from the expansion of the high-pressure hydrogen gas to generate electrical current. During the initial portion of the trailer offloading process, when the pressure of the H2 gas trailer602is at a pressure higher than that of the H2 Gas storage614, the turboexpander102can be used to recover expansion energy by generating electrical current. This electrical current can be used to offset at least some of the electrical demand required to run compressor612, which is used to pump hydrogen gas into the hydrogen gas storage container614at a latter portion of the emptying process when the pressure of the H2 gas trailer602is at a pressure lower than that of the H2 Gas storage614.

At the outset, high-pressure hydrogen gas604is delivered to the hydrogen fuel station600by a hydrogen gas trailer602. The hydrogen fuel station400includes a flow control system126and a pressure control valve130. As mentioned before, flow control system126includes a FCV240and ESV242. Flow control system126can control the flow of high-pressure hydrogen gas604into the turbine wheel104of the turboexpander102. The turbine wheel104of the turboexpander102can expand and reduce the pressure of the high-pressure hydrogen gas604.

The energy reclaimed from the pressure letdown of the high-pressure hydrogen gas604by the turbine wheel104is used to generate electrical current. The expansion of the high-pressure hydrogen gas604causes the turbine wheel104to rotate, thereby rotating a rotor108. Rotation of the rotor108within the stator110generates electrical current. The electrical current can be used to power certain loads, such as compressor612via a battery storage system614, or at least offset the power consumed by compressor612by selling generated power to the grid or by using the generated power to power other loads at the facility. For example, electrical current generated by the turboexpander102can be directed to a power electronics118(described above). Power electronics118can include circuitry to condition the generated electrical current to be compatible with the battery storage system614, or other load(s) at the fueling station or the grid.

FIG.6Bis a graphical representation620of hydrogen pressure changes in a hydrogen trailer container and a hydrogen storage system in accordance with embodiments of the present disclosure. As the hydrogen pressure in the trailer container falls, a compressor is used to pump the hydrogen into the storage tank. The compressor can be powered by the turboexpander via a battery storage system, as shown inFIG.6Ato fill the storage tank at the fueling station with pressurized hydrogen.

FIG.7is a process flow diagram for transferring hydrogen from a trailer container to a storage tank using a turboexpander in accordance with embodiments of the present disclosure. High-pressure hydrogen gas is input into turbine wheel of turboexpander from the trailer container (702). The high-pressure hydrogen gas input into the turbine wheel can cause the turbine wheel to rotate, which causes a rotor to rotate within a stator (704). The turbine wheel also expands the high-pressure hydrogen gas, thereby lowering the pressure of the hydrogen gas. This low (or lower)-pressure hydrogen gas is output from the turboexpander into a storage container at the fueling station (706).

The electrical current generated by the turboexpander can be output to a power electronics. The power electronics can condition the electrical current to be compatible with a battery storage system, as well as other facility load(s) or for supplying to the grid (708). The power electronics can output the adjusted electrical current to battery storage system or intended load(s) or to the grid (710). The compressor can be operated using the power generated from the expansion of the hydrogen gas to pump the hydrogen gas into the fuel tank (712).

FIG.8is a schematic diagram of a hydrogen production system800that includes a turboexpander102in accordance with embodiments of the present disclosure. The turboexpander102can recover energy lost during pressure let down in a natural gas distribution network. Natural gas distribution is an energy intensive process that uses several megawatt class compressors to pressurize the gas and transmit it along thousands of miles of pipeline. At city gate Pressure Reduction Stations (PRS), this compressed pipeline gas is reduced to a pressure suitable for distribution to local businesses, energy production, and residential use.

At PRS, instead of pressure reduction valves or Joule-Thomson (JT) valves, the turboexpander102can be used to reduce the pressure. The energy from the expansion of the natural gas can be recovered and converted into useable electricity using the turboexpander102.

Some PRS are located in remote areas with limited access to the surrounding electrical grid. Therefore, locally consuming the generated power is desirable. In embodiments, the power generated by the turboexpander102can be consumed for green hydrogen production through electrolysis. The electricity generated from the turboexpander102can power a bank of electrolyzers, which can produce hydrogen and oxygen from water.

Current polymer electrolyte membrane (PEM) electrolyzer efficiencies range from 70 to 82% with the expectation of reaching 86% by2030according to the Fuel Cells and Hydrogen Joint Undertaking. Current PEM technology produces about 1 kg of hydrogen per 50 kWh of electricity, thus a 280 kW FIT system producing 2.45 GWh of power per year can produce up to 54 tons of green hydrogen annually. Production of green hydrogen from clean and renewable energy sources will play an integral role in meeting The Paris Agreement goals.

InFIG.8, the hydrogen production system800is linked to a natural gas PRS that links a pipeline that can transport high-pressure natural gas822. The high-pressure natural gas822can be heated using heater122. The heated, high-pressure natural gas can be directed into the turboexpander102through a flow control system126. The hydrogen production system800includes a flow control system126and a pressure control valve130. As mentioned before, flow control system126includes a FCV240and ESV242. Flow control system126can control the flow of heated, high-pressure natural gas824into the turbine wheel104of the turboexpander102. The turbine wheel104of the turboexpander102can expand and reduce the pressure of the heated, high-pressure natural gas824. The low (or lower)-pressure natural gas826is directed to the pipeline for downstream distribution and consumption.

The energy reclaimed from the pressure letdown of the heated, high-pressure natural gas824by the turbine wheel104is used to generate electrical current. The expansion of the heated, high-pressure natural gas824causes the turbine wheel104to rotate, thereby rotating a rotor108. Rotation of the rotor108within the stator110generates electrical current. The electrical current can be used to power electrolyzer802, or at least offset the power consumed by electrolyzer802by selling generated power to the grid or by using the generated power to power other loads at the hydrogen production station800. For example, electrical current generated by the turboexpander102can be directed to a power electronics118(described above). Power electronics118can include circuitry to condition the generated electrical current from the turboexpander to be compatible with the electrolyzer802, or other load(s) at the hydrogen production system800or the grid.

The electrolyzer802can use water as an input to produce hydrogen804and oxygen806through electrolysis. The hydrogen can then be transported offsite by trailer or blended into the natural gas pipeline.

FIG.9is a process flow diagram for producing hydrogen using a turboexpander in accordance with embodiments of the present disclosure. High-pressure natural gas is input into turbine wheel of turboexpander from (902). The high-pressure natural gas input into the turbine wheel can cause the turbine wheel to rotate, which causes a rotor to rotate within a stator (904). The turbine wheel also expands the high-pressure natural gas, thereby lowering the pressure of the natural gas. This low (or lower)-pressure natural gas is output from the turboexpander for downstream distribution and consumption (906).

The electrical current generated by the turboexpander can be output to a power electronics. The power electronics can condition the electrical current to be compatible with an electrolyzer for a hydrogen production process system (908). The power electronics can output the adjusted electrical current to power the electrolyzer (910). The electrolyzer can then operate to produce hydrogen, as described in the text accompanyingFIG.8(912).

FIG.10is a schematic diagram of a hydrogen liquefaction system1000that includes a turboexpander in accordance with embodiments of the present disclosure. Hydrogen, like other gases, is most efficiently transported in its liquid state. The liquefaction process shown inFIG.10can be used to convert hydrogen gas (GH21002) into liquid hydrogen (LH21004). A series of processes are used to reduce the temperature of the GH21002down to −253° C., including compression, heat exchange, and expansion. The turboexpander102can be used to recover energy lost during the expansion of H2 and the expansion of the closed-loop heat exchange fluid (such as hydrogen, helium, or nitrogen).

The example liquefaction system1000shown inFIG.10, two heat exchangers (e.g., heat exchanger1006and heat exchanger1008) are used. The heat exchangers drop the temperature from the incoming GH21002and the exiting LH21004. There may be more than two heat exchangers (or more than two heat exchange processes). Other equipment may also be included in this portion of the system that are not illustrated, such as compressors or other devices. Heat exchanger can include pre-cooling heat exchanger, cryogenic heat exchangers, etc.

The heat exchange system100also includes a closed-loop Brayton cycle1010. The closed-loop Brayton cycle includes a compressor1006for compressing the heat exchange fluid. The compressor1012directs the heat exchange fluid into a cooler1014. The cooled heat exchange fluid can be used in heat exchanger1006to cool hydrogen The turboexpander102acan be used to further expand and cool the heat exchange fluid for use in heat exchanger1008and in heat exchanger1006to further cool the hydrogen. The heat exchange fluid is then directed into the compressor1012to continue the Brayton cycle1010.

The expansion of the heat exchange fluid by the turbine wheel of the turboexpander102acan result in the generation of electricity. The power generated by the turboexpander102aby the expansion of the heat exchange fluid can be used to power loads. Power electronics118can condition the electricity output by the turboexpander for use by one or more loads. For example, electricity generated by the turboexpander102acan be used to power the compressor1012(or offset power used by the compressor1012). The turboexpander102acan also provide power to other loads1018. Such loads can include other devices that are part of the liquefaction process, such as compressors in the heat exchangers1006,1008or other devices.

In some embodiments, a turboexpander102bcan also be used to generate electricity from the expansion of the hydrogen in the liquefaction process. Power generated from hydrogen expansion can be used to power compressors or other devices.

FIG.11is a process flow diagram for performing hydrogen liquefaction using a turboexpander in accordance with embodiments of the present disclosure. As mentioned above, the liquefaction system includes heat exchangers and a closed-loop Brayton cycle. The Brayton cycle can include a compressor that compresses heat exchange fluid (1102). The compressed heat exchange fluid can be cooled by a cooling device (1104). The pressurized and cooled heat exchange fluid can be used in a heat exchanger of the hydrogen liquefaction process (1106). The heat exchange fluid can be expanded by a turbine wheel of a turboexpander (1108). The expansion of the heat exchange fluid by the turbine wheel of the turboexpander reduces the pressure of the heat exchange fluid and causes a rotor coupled to the turbine wheel to rotate.

The expanded heat exchange fluid can be output from the turboexpander and directed back into the Brayton cycle, and into heat exchangers of the liquefaction process to cool hydrogen (1110). The heat exchange fluid can then be directed back into the compressor (1102).

The rotation of the rotor of the turboexpander can result in the generation of electricity (1112). The electricity can be conditioned by power electronics so that it is compatible to supply power to one or more loads (1114), including one or more compressors of the Brayton cycle and/or the heat exchangers. The compressor(s) can be operated (at least partially) by the power generated by the turboexpander (1116).

In some embodiments, energy lost during expansion of the hydrogen during the liquefaction process can also be used to rotate a turbine wheel of a turboexpander to generate electricity. Likewise, such power can be used to operate various loads, including compressors of the heat exchangers or other devices.

The use of turboexpander102for generating electricity from gas expansion offers the following benefits in the liquefaction process:1. Magnetic bearings allow for oil and air free operation eliminating process gas contamination2. Magnetic bearings offer a long life (25 years), maintenance-free operation3. System is designed to deliver 125 kW or 280 kW, a convenient and scalable power building block for liquefactions plants4. Modular design allows for low capital costs instead of a custom-engineered solution5. Flow-through design eliminates dynamic seals and risks of leaks6. Energy balance due to generator loaded design

Existing liquefaction plants process up to 40 tons per day (tpd) of liquid hydrogen, creating ˜400 kW of potential power generation from the turboexpander102. Future liquefaction plants are being designed with capacities up to 200 tpd, creating ˜2 MW of clean power. Based on 2019 U.S. totals from the Energy Information Administration, 2 MW of power generation equates to 8,000 tons per year of CO2 equivalent (CO2e) emissions offset.

The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. Furthermore, the foregoing use of embodiment and other exemplarily language does not necessarily refer to the same embodiment or the same example, but may refer to different and distinct embodiments, as well as potentially the same embodiment. In the foregoing specification, a detailed description has been given with reference to specific exemplary embodiments. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the claims.