WO2021235945A1 - Système de ravitaillement en carburant et de stockage - Google Patents

Système de ravitaillement en carburant et de stockage Download PDF

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Publication number
WO2021235945A1
WO2021235945A1 PCT/NO2021/050129 NO2021050129W WO2021235945A1 WO 2021235945 A1 WO2021235945 A1 WO 2021235945A1 NO 2021050129 W NO2021050129 W NO 2021050129W WO 2021235945 A1 WO2021235945 A1 WO 2021235945A1
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WO
WIPO (PCT)
Prior art keywords
pressure
fuel hose
fuel
underwater vehicle
hose
Prior art date
Application number
PCT/NO2021/050129
Other languages
English (en)
Inventor
Kjell E ELLINGSEN
Ola Ravndal
Erling MYHRE
Lorents REINÅS
Original Assignee
Equinor Energy As
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Equinor Energy As filed Critical Equinor Energy As
Publication of WO2021235945A1 publication Critical patent/WO2021235945A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B27/00—Arrangement of ship-based loading or unloading equipment for cargo or passengers
    • B63B27/30—Arrangement of ship-based loading or unloading equipment for transfer at sea between ships or between ships and off-shore structures
    • B63B27/34—Arrangement of ship-based loading or unloading equipment for transfer at sea between ships or between ships and off-shore structures using pipe-lines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B25/00—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby
    • B63B25/02—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods
    • B63B25/08—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid
    • B63B25/12—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid closed
    • B63B25/14—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid closed pressurised
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/001—Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/42—Towed underwater vessels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/001—Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations
    • B63G2008/002—Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations unmanned
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/42—Towed underwater vessels
    • B63G2008/425—Towed underwater vessels for transporting cargo, e.g. submersible barges for fluid cargo

Definitions

  • the invention relates to underwater vehicles and the operation thereof, and more specifically the utilisation of autonomous underwater vehicles for the transporting of gas or liquid for a refuelling operation of a surface vessel.
  • the video also describes a distribution and storage network, which could be powered by renewable energy sources, such as wind and solar.
  • the following publication discloses a subsea shuttle system: Research Disclosure database number 677082 published digitally on 21 August 2020.
  • the subsea shuttle described is used as a materials handling system and adapted to receive a cargo tank in order to deliver a payload to an unmanned platform.
  • the subsea shuttle navigates the seabed using a plurality of acoustic or electromagnetic beacons and corresponding receivers on the shuttle.
  • FIFO Fleavy Fuel Oil
  • the invention provides a method, a fuel hose and an unmanned underwater vehicle, for refuelling a surface vessel as set out in the accompanying claims.
  • Figure 1 is a schematic view of an underwater vehicle containing a pressure vessel
  • Figure 2A is a schematic view of a pressure vessel at a first depth underwater
  • Figure 2B illustrates the pressure vessel of Figure 2A having ascended to a shallower depth
  • Figure 2C illustrates the pressure vessel of Figure 2A having descended to a lower depth
  • Figures 3A and 3B are schematic views showing parts of a pressure vessel having a pressure compensation system
  • FIGS. 4A to 4C show parts of example pressure compensation systems
  • Figure 5 is a schematic view of an underwater vehicle having a gas pocket in the outer hull
  • Figure 6A is a schematic view of an underwater vehicle having a plurality of pressure vessels
  • Figures 6B and 6C are perspective views the underwater vehicle interior, having a plurality of pressure vessels.
  • Figure 7 is a flow chart of a method.
  • Figure 8 is a schematic view of an underwater vehicle refuelling a surface vessel.
  • Figure 9 is a schematic view of a refuelling hose, deployed from a surface vessel.
  • Figure 10 is a schematic view of steering means on the refuelling hose.
  • Figure 11 is a schematic view of steering means on the refuelling hose.
  • Figure 12 is a schematic view of a refuelling connection.
  • Figure 13 is a schematic view of refilling stations.
  • Figure 14 is a flow chart of a method.
  • the subsea transportation of a fluid cargo can be improved by providing of a pressure compensating system to maintain or control the internal pressure of the fluid based on the external hydrostatic pressure.
  • a pressure compensating system to maintain or control the internal pressure of the fluid based on the external hydrostatic pressure.
  • the shuttle a double hull is used.
  • internal pressure within the hull of an AUV but outside the pressure vessel holding the fluid is also maintained and controlled at or near external hydrostatic pressure. In this way, it is ensured that the internal pressure of the fluids remains the same as or similar to the external hydrostatic pressure, meaning that the vessel (containing the fluid) is not at risk of a collapse (or burst) failure.
  • FIG 1 illustrates a schematic underwater vehicle according to an embodiment of the invention.
  • the underwater vehicle may be an autonomous underwater vehicle (AUV), or a remotely operated underwater vehicle (ROV).
  • the vehicle comprises an outer hull 10, having a hydrodynamic shape to reduce drag.
  • An elliptical outer hull 10 is shown in Figure 1 , but other hydrodynamic shapes known in the art are suitable.
  • the pressure vessel 12 may be fixed within the outer hull 10 using a frame or other rigid supports (not shown). In this way, a space between the outer hull 10 and pressure vessel 12 is formed.
  • the outer hull 10 has a channel 14, which is in fluid communication, or pressure communication, with the surrounding water when the vehicle is submerged.
  • the space between the outer hull 10 and inner pressure 12 vessel at least partially fills with seawater, depending on the net buoyancy requirements.
  • a part of the outer hull 10 volume is occupied by one or more compartments for containing gas (e.g. ballast tanks), as discussed in more detail below.
  • gas e.g. ballast tanks
  • the channel 14 is selectively closed (e.g. via operation of a valve) to allow or block fluid communication through the channel.
  • a propeller 16 is provided.
  • the propeller is coupled to a power source and control unit (not shown) to enable autonomous and/or remote operation of the vehicle.
  • An electric power source is preferably used.
  • the vehicle includes a docking station 18 provided on the bottom of the outer hull 10 for docking with an external platform or other equipment.
  • the docking station 18 is provided within or largely within the outer hull 10 to reduce the drag.
  • the outer hull 10 may include a hinged or detachable section (not shown) for accessing the internal pressure vessel 12.
  • the vehicle structure shown in Figure 1 is similar to a double hull structure used in some conventional submarines.
  • the inner structure includes instead a pressure vessel 12 maintained at a pressure similar to the external hydrostatic pressure.
  • the pressure vessel 12 can be designed with a much lower collapse pressure capacity than a standard pressure hull, which results in significant weight savings (e.g. by reducing the need for stiffeners).
  • similar to the external hydrostatic pressure, it is meant that the internal pressure is kept suitably close to the external pressure so that the pressure differential dP (i.e. overpressure or under pressure) is not too large. If the overpressure is too large, the pressure vessel may undergo a burst failure. Conversely, if the under-pressure is too large, the pressure vessel is at risk of a collapse failure.
  • the collapse pressure threshold is sensitive to geometric imperfections in the pressure vessel 12 shape, meaning that a smooth, curved shape is preferable.
  • the pressure hull 12 has a substantially cylindrical shape with hemispherical ends.
  • the underwater vehicle may include a plurality of cylindrical pressure vessels, preferably aligned parallel to each other, as discussed in more detail below.
  • FIGs 2A-2C illustrate part of a pressure compensation system, where the internal pressure is equalised with the external pressure.
  • the outer hull is not shown for clarity.
  • the internal vessel 22 contains a cargo, in this example a fluid F.
  • the fluid F has an initial pressure P1.
  • a pressure relief 26 is provided to selectively allow seawater SW in and out of the pressure vessel 22.
  • the pressure relief unit 26 may also be connected to one or more of the other vessels and in pressure communication or fluid communication with that other vessel.
  • a barrier 24 is provided to separate the fluid F and the seawater SW. In this way, the pressure vessel is divided into a first portion 28a and a second portion 28b, containing the fluid F and seawater SW, respectively.
  • the barrier 24 prevents fluids from being transferred across the barrier, while is moveable to allow pressure communication. (although the barrier is illustrated like a piston in Figures 2A-2C, further examples of barriers are discussed below.) If the vehicle changes depth, the external hydrostatic pressure Pe will change. As shown in Figure 2B, if the vehicle ascends, the external pressure Pe decreases (i.e. Pe ⁇ P1). To compensate for this change, the pressure relief unit 26 opens to allow water SW to be expelled from the second portion 28b of the pressure vessel 22, as indicated by the arrow 29 in Figure 2B. The barrier 24 moves to the right as the fluid F decompresses, and the pressure in the first and second portions 28a, 28b is equalised with Pe.
  • the fluid F may be a liquid, meaning that the fluid F will always have some degree of compressibility.
  • FIG 2C illustrates the reverse case, where the vehicle descends.
  • the external pressure Pe increases (i.e. Pe > P1).
  • the pressure relief unit 26 opens to allow seawater SW to flow into the pressure vessel 22 and the barrier 24 moves to the left, compressing the fluid F until the pressure is equalised.
  • the pressure relief unit 26 then closes.
  • stress on the pressure vessel is effectively eliminated.
  • the surrounding seawater temperature Tsw may change from one location to the next during transit. If the seawater temperature Tsw is increased but the volume of fluid remains fixed, the fluid pressure will increase, with the potential for a burst failure of the vessel. Conversely, if temperature is decreased for a constant volume of fluid, the pressure will decrease, with the potential for a collapse failure of the vessel.
  • the pressure compensation system described herein may also compensate for such thermal volume changes. As the vehicle is loaded with cargo fluid, the incoming fluid may have a temperature T1 that is different to the seawater temperature Tsw.
  • the vehicle is submerged while transporting the fluid to a destination, meaning that the fluid temperature will change and become equal or close to equal to Tsw due to heat being exchanged with the surrounding seawater over time.
  • Tsw seawater temperature
  • the fluid volume will adjust correspondingly, because fluid volumes are temperature dependent, It can be seen, therefore that the pressure compensating/equalising system proposed herein has the added advantage of compensating for thermal volume changes.
  • the pressure vessel is thermally insulated to reduce the heat exchange process. Flowever, insulation will add cost and weight to the shuttle. Additionally, in some embodiments, the vehicle further comprises a heater system to add heat to the pressure vessel to compensate for heat exchange to the surroundings.
  • the fluid may be temperature managed, e.g. by use of a heat exchanger as a part of the fluid loading system, to match the seawater temperature Tsw at the time of loading to the shuttle.
  • Figures 2A-2C show a single valve to represent pressure relief unit 26, other suitable arrangements may be used.
  • the pressure relief unit 26 includes a pair of one-way relief valves, with the valves having opposite operational directions. If the external pressure increases so that dP ⁇ 0 (i.e. under-pressure), the first valve opens to allow water into the pressure vessel. Likewise, when dP>0 (i.e. overpressure), the second valve opens to allow water out of the pressure vessel, thereby equalising the pressure.
  • the valves are pressure relief valves which open when dP exceeds pre-set thresholds.
  • the dP thresholds are adjustable, and may be controlled by a control system.
  • the pressure compensation system maintains the internal pressure at a slight overpressure (dP>0), rather than equalising the pressure as above.
  • the burst pressure threshold is higher than the collapse pressure threshold, meaning that keeping the internal pressure vessel in an overpressure regime may be preferable.
  • the overpressure is maintained at a target value suitably far removed from the burst pressure threshold for the vessel, so that the pressure vessels are not at risk of bursting.
  • the slight overpressure provides a buffer such that if the external pressure were to increase suddenly, the risk of a collapse failure is reduced.
  • the pressure compensation system includes a pump unit and a pressure relief unit.
  • the pump unit is configured to pump seawater into the pressure vessel to create an overpressure (dP > 0) within the pressure vessel.
  • the pump unit and relief unit may work against each other if they are two separate systems, e.g. a pressure relief valve will need to have relief settings carefully determined and possibly controllable if combined with a pump system for pressure increase.
  • the pump unit and relief unit may be configured to disable/enable based on operational parameters, measurements or an autonomous control system. This will ensure that the pressure vessel never will experience a detrimental collapse pressure.
  • the vehicle includes a secondary pressure compensation system for safety and increased reliability, configured to engage in the case the primary pressure compensation system fails.
  • the pressure vessel includes one or more weak link burst plates or disks as a safety measure, should the pressure relief unit fail or stop working.
  • the fluid F cargo is C02
  • the underwater vehicle travels at an optimal depth of 200 m. This operation depth is deep enough to avoid wave motion at the surface, but shallow enough to avoid any contact with the seabed topology.
  • the hydrostatic pressure is approximately 20 bar.
  • the C02 by way of the pressure compensating system and the external hydrostatic pressure combined
  • the C02 is pressurised to an absolute pressure of 40 bar (i.e. having a 20 bar overpressure at the 200 m depth)
  • the C02 is then in the liquid phase for typical subsea temperatures e.g. between 0 and 10 °C. Transport of C02 in liquid state is beneficial as a larger mass of C02 can be moved in a single shipment.
  • the external hydrostatic pressure is reduced by approximately 10 bar (i.e. from 20 bar to 10 bar).
  • the pressure relief unit is not operated, thereby maintaining the C02 absolute pressure of 40 bar inside the pressure vessel. This implies that the pressure vessel is able to withstand an overpressure of 30 bar (i.e. dPmax is greater than 30 bar in this example).
  • the pressure relief valve opens. In this way, it is ensured that that the C02 absolute pressure is reduced to avoid a structural failure (e.g. a burst failure) while the external hydrostatic pressure is reduced by the vehicle ascending.
  • the relief unit is operated (e.g. pressure relief valve opened) to allow the seawater hydrostatic pressure to communicate into the pressure vessel, thereby equalising the internal pressure with the surroundings. This will prevent the pressure vessel from failing structurally (e.g. collapsing) as the external hydrostatic pressure is increased by the vehicle descending.
  • the pump unit may be operated to increase the absolute pressure of the C02 to a pressure that is the same or above the external hydrostatic pressure, but not higher than the threshold dPmax. This will prevent the pressure vessel from failing structurally (e.g. collapsing) as the external hydrostatic pressure is increased by the vehicle descending.
  • the outer hull is not free-flooding, but is selectively opened to the surrounding seawater via one or more pressure communication channels.
  • the outer hull may also be configured with a pressure compensation system.
  • the pressure of both the internal vessel and the outer hull are compensated separately.
  • the outer hull may be maintained at a slight overpressure, when compared to the external hydrostatic pressure.
  • this allows the outer hull to be made of a lightweight flexible or semi-rigid material, while maintaining a hydrodynamic shape (i.e. analogous to an airship).
  • the difference between the internal vessel pressure and the external hydrostatic pressure can be staggered. In this way, the pressure differential across the internal pressure vessel may be reduced, reducing the risk of a burst failure of the internal pressure vessel.
  • Pressure compensation of the outer hull may also be beneficial for safety reasons, i.e. to avoid a potential pressure build-up in the internal volume between the pressure vessels and the outer hull in the event of a failure.
  • the pressure compensation system of the outer hull may be used a safety device for automatic bleed off (e.g. of escaped gas) in case something goes wrong. In this way, the vehicle will sink to the bottom rather than rise to the surface, which is generally preferable.
  • Another illustrative example relates to the offloading of C02 as the cargo.
  • the vehicle is stationary and connected to a receiving client for delivering of the cargo out of the internal pressure vessel.
  • the pressure compensation system operates the pump unit to maintain an overpressure (dP > 0) as the volume of the cargo is gradually reduced during offloading to the receiving client.
  • the pump unit controls the absolute pressure of the cargo at a pressure above the external hydrostatic pressure and/or the inlet pressure threshold of the receiving client.
  • the receiving client may be equipped with a pump that drains the cargo fluid, with the risk of imposing a negative overpressure (dP ⁇ 0) and causing a structural failure (e.g. collapse) of the pressure vessel.
  • the cargo flows into the receiving client, without the risk of a collapse failure during cargo offloading.
  • the design of the receiving client may be simplified i.e. by reducing/eliminating operation of the external pump, or eliminating the need for an external pump altogether.
  • the pressure compensation system is operated to ensure that the internal pressure does not exceed dPmax as the cargo fluid is input from a supply client. If the input pressure exceeds the allowable pressure structural failure (e.g. bursts) of the pressure vessel may be the result.
  • operation of the pressure relief unit provides an acceptable and safe overpressure dP inside the cargo fluid in the pressure vessel during filling.
  • Operation of the pump unit (in the reverse direction compared to the above offloading example) may provide a desired dP inside the cargo fluid inside the pressure vessel during filling.
  • the pump unit and relief valve are both be operated simultaneously to achieve a higher filling volume rate.
  • the pump may be operated to further generate an absolute pressure inside the pressure vessel less than the pressure at the supply client, such that the cargo fluid will flow naturally into the pressure vessel. This may only be possible within the structural limitations of the pressure vessel, e.g the absolute pressure inside the pressure vessel cannot be lower that the collapse strength of the pressure vessel.
  • FIGS 3A and 3B show an example pressure vessel 300 in more detail.
  • the vessel 300 has a cylindrically body 302, with a hemispherical end section 304 bolted to the end of the body 302 via a flange 306.
  • the end section 304 includes a first one-way valve 308 as an inlet, and a second one-way valve 310 as an outlet.
  • the end section 304 may be unbolted for access to the vessel interior.
  • a reel 312 is provided inside the end section 304.
  • the reel 312 may be spring energised.
  • a cable 314 is coiled.
  • a piston assembly 316 is connected, as shown in Figure 3B.
  • the piston assembly 316 includes a rigid outer frame 318.
  • a pair of inflatable sealing rings 320a, 320b are provided at the front and rear end of the outer frame.
  • the sealing rings 320a, 320b are inflated with a gas (e.g. air).
  • the sealing rings 320a, 320b are connected to an umbilical 322 for pressure adjustment and condition monitoring.
  • the sealing rings 320a, 320b When inflated, the sealing rings 320a, 320b each form a ring-shaped seal between the frame 318 and the inner surface of pressure vessel body 302, thereby defining a closed volume 324 between the rings 320a, 230b.
  • the closed volume 324 is filled with a barrier substance.
  • the barrier substance is a non-reactive liquid, oil or gel (e.g. silicone grease). In some embodiments, the barrier substance is maintained at a slight overpressure compared to the neighbouring fluids.
  • the piston assembly also comprises buoyancy chambers 326a, 326b, at the front and rear end, respectively.
  • the buoyancy chambers make the piston neutrally buoyant within the surrounding fluids.
  • a positioning device 328 is provided on the far end of the piston assembly, for detecting the longitudinal position of the piston assembly within the pressure vessel.
  • the positioning device 328 is calibrated relative to a reference point within the vessel body 302.
  • Pressure and temperature sensors 330 are provided on both end faces of the outer frame 318. Further pressure and temperature sensors 330 may also be provided the inside buoyancy chambers 326a, 326b and inner volume 324.
  • the cable 314 is a bundle comprising the following: a feed line umbilical for supply of the fluids (e.g. the barrier substance, and gas for sealing ring inflation); power cables; and cables for acoustic and/or digital communication.
  • Power is supplied by an internal power supply (e.g. a battery or accumulator, not shown), which may be provided on the reel 312 or within the piston assembly 316.
  • Figures 2A-C and 3A-B show a piston-like movable barrier
  • other types of barrier are suitable for separating the fluid F and seawater SW in the present invention.
  • Figure 4A (not to scale) illustrates an example movable piston 40, which resembles a batching pig used in the pipeline industry.
  • batching pigs are used in pipelines as a moving seal to separate two different products so that they can both be transported using the same pipeline.
  • Batching pigs typically employ polyurethane (PU) disc seals.
  • PU polyurethane
  • the inventors have realised that a batching pig (scaled up to the diameter required for the pressure vessel) may be used as the moveable barrier, as illustrated in the Figure.
  • Figure 4B shows an alternative embodiment, wherein the barrier is a balloon-type piston.
  • a balloon 42 is connected to an external pressure supply and control system (not shown).
  • the balloon 42 is inflated by the external pressure supply such that it seals in the transverse direction, but can move in the longitudinal direction under the pressure of the seawater SW or fluid F.
  • the balloon 42 may be filled with air or any other suitable compressible gas.
  • the barrier may be formed by a bladder 44.
  • the bladder 44 is elastic (i.e. a balloon) or inelastic, and is situated inside the pressure vessel to divides at the fluids from mixing.
  • the bladder 44 has a maximum volume that exceeds that of the pressure vessel, meaning it will receive protection from overpressuring from the walls of the pressure vessel.
  • the bladder 34 will float in the seawater SW (or vice versa, depending on the density of the fluid F).
  • the movable barrier is a layer of a third substance which divides the two fluids.
  • the third substance may be an emulsion or a chemical matter that does not resolve in any of the other fluids, but will coalesce enough to ensure that the first and second fluid does not have direct contact.
  • the third substance may be an immiscible liquid.
  • the pressure vessel may be oriented vertically, relative to the overall longitudinal axis of the vehicle, so that the third substance layer floats on the seawater SW but sinks beneath the fluid F, or vice versa dependant on the fluid F density.
  • the space between the outer hull and internal pressure vessel is filled partially with gas instead of being completely water-filled, as shown in Figure 5.
  • the space between the outer hull 50 and pressure vessel(s) 52 is partially filled with gas G.
  • gas G Partially filling the outer hull with gas G provides a method to adjust the resulting buoyancy forces of the vehicle, and also adjust the location of the buoyancy centroid relative to the gravitational forces and centroid. In this way, the gas may improve the stability of the vehicle, as gas will be at top. Further, it can provide weight benefit and remove some or all of the need for ballast tanks.
  • the underwater vehicle is configured to have variable buoyancy so that that the equilibrium depth of the vehicle can be controlled.
  • the vehicle in a docking approach where the vehicle proceeds to lay on the seabed, the vehicle will need to become negatively buoyant and sink to the bottom. In reverse, the vehicle needs to leave the seabed by becoming more buoyant, e.g. after having offloaded or loaded with a cargo, again affecting the total weight.
  • salinity of seawater may have minute differences over time at one ocean location or as one moves from one ocean location to another.
  • the equilibrium depth may change due to minute salinity changes (i.e. the water density is changed) and buoyancy is adjusted accordingly to maintain a desired water depth during transit.
  • the gas is evaporated from a liquid gas tank, located within or attached to the outer hull.
  • the gas is evaporated and allowed directly into the fluid-filled volume (typically seawater) between the outer hull and the internal pressure vessel(s).
  • the in-situ water is allowed to evacuate through a pressure relief system, thereby allowing for some of the seawater to be displaced by the gas.
  • the gas locates itself at the top of the water inside the outer hull.
  • the gas may be air, C02, H2 etc. Coolant fluids known from use in heating, ventilation and air conditioning (FIVAC) applications may be used.
  • FVAC heating, ventilation and air conditioning
  • the gas is evacuated from the top of the outer hull e.g. by venting into the surrounding environment exterior to the vehicle. This will imply that the gas is environmental friendly.
  • the gas may be allowed into a bladder to contain the gas and expand in volume, displacing the seawater in the same way as before.
  • the bladder can be located and secured in a desirable location inside the outer hull.
  • the gas is released from the bladder into the surrounding seawater exterior to the vehicle to decrease the buoyancy. This may be more easily achieved when the gas is contained within the bladder and not free inside the hull, since if the gas is free inside the hull, its location relative to vent exit(s) would be dependent of the orientation of the vehicle.
  • the gas G is evaporated into a rigid tank (i.e. a tank which has a fixed volume).
  • the tank is originally liquid filled, and the evaporated gas displaces the liquid (e.g. seawater) out of the tank.
  • the tank becomes increasingly and finally positively buoyant.
  • the tank may be equipped with a technology that isolates the gas and the fluid (seawater) e.g. a bladder or movable piston as described above in connection with the pressure vessels.
  • the gas is circulated between a pressurised tank holding gas in liquefied state and another tank (the variable buoyancy tank) where gas is in gas state, using vaporization/condensing phase change recirculating refrigeration technology (i.e. an evaporator and compressor system).
  • the variable buoyancy tank the process of displacing seawater by gas produces a change to the tanks buoyant forces.
  • a control system is provided to control the operation of the evaporator pump vs. the compressor, allowing the accumulation of gas in the variable buoyancy tank to be controlled to achieve the desired buoyancy. If the compressor rate is increased and/or the evaporation process is reduced, the gas will accumulate in the liquid holding tank, allowing the buoyancy to decrease.
  • the power required to operate the evaporator s typically low, and the cooling effect of the surrounding seawater can be used for the compressor and the condensing phase change.
  • the control system may be operated automatically and/or remotely.
  • the buoyant tank may be equipped with a technology that isolates the gas and the fluid (seawater) e.g. a bladder or movable piston as described above in connection with the pressure vessels.
  • the source of liquefied buoyancy gas may be the cargo liquid itself.
  • the amount of C02 required for buoyancy control is negligible compared to the bulk volume under transportation. The benefit of this approach is that no additional gas source is required.
  • a plurality of bladders and/or rigid tanks as described above may be provided along the length and breadth of the vehicle to enable buoyancy and trimming of stability.
  • the C02 gas that has served its buoyant purpose may be released to the surrounding water, with negligible negative environmental consequences.
  • the underwater vehicle may include a plurality of pressure vessels.
  • the plurality of pressure vessels are arranged substantially parallel to each other, as shown in Figures 6A-6C.
  • the pressure vessels 62 are arranged horizontally, in line with the axis of the outer hull 64.
  • the vessels are arranged vertically, or at an angle in between the horizontal and vertical.
  • the vessels 62 are held in place by a plurality of supports 66 provided along the length of the vessels 62.
  • Figure 6C illustrates the end of the pressure vessels at which the cargo fluid is loaded/unloaded.
  • the pressure vessels 62 are mutually connected to a conduit system 68 for loading/unloading the fluid from the vessels 62.
  • approximately half of the pressure vessels contain the fluid cargo at the front end, and the remaining half contain the fluid cargo at the rear end. In this way, the vehicle remains balanced. Further, such embodiments are suitable for management of the vehicle trim angle (the longitudinal axis being changed from horizontal, including all the way to a vertical or near to a vertical position).
  • the present invention can be used for storage and then the transportation of a variety of fluids for various applications.
  • the underwater vehicle can be used to transport fluids to a well or from a well.
  • suitable fluids are: CO2 (for injection into a well); chemical supply (MEG, Methanol etc); oil & gas; freshwater; toxic waste; separation of oil, gas, water and sand; septic/bio-mass; and rig fluids such as mud, brine, drill cuttings etc.
  • the ‘fluid’ cargo throughout this specification may comprise a liquid with solids suspended or contained within the liquid.
  • the vehicle can further be used for energy storage and transportation: the internal volume can be filled with bio fuel such as ethanol; diesel, heli-fuel or ammonia; or the internal volume can be filled with a battery bank for temporary storage and/or transport of electrical energy.
  • bio fuel such as ethanol
  • the internal volume can be filled with a battery bank for temporary storage and/or transport of electrical energy.
  • the internal volume could even be used to storage and transport of live seafood, e.g fish.
  • the general method described above is illustrated in Figure 7, and includes the steps of (S1) loading the one or more vessels with the fluid cargo; (S2) balancing the pressure of the internal volume with the pressure exterior to the underwater vehicle; and (S3) controlling the pressure of the fluid cargo based on a pressure outside of the internal vessels.
  • Paragraph 1 An underwater vehicle for transporting a fluid cargo, comprising: an outer hull defining an internal volume; a pressure communication channel between the internal volume and the exterior of the outer hull, arranged control the pressure in the internal volume based on the exterior pressure; one or more internal vessels for containing the fluid cargo; and a pressure compensation system arranged to control the pressure of the cargo based on a pressure outside of the interval vessels.
  • Paragraph 2 The underwater vehicle of paragraph 1 , wherein the pressure compensation system comprises: within each internal vessel, a barrier for separating a first portion of the vessel from a second portion of the vessel, the barrier permitting pressure communication between the first and second portions.
  • Paragraph 3 The underwater vehicle of paragraph 2, wherein the first portion contains the fluid cargo and wherein the second portion contains seawater.
  • Paragraph 4 The underwater vehicle of paragraph 2 or 3, wherein the pressure compensation system is arranged to control the pressure of the fluid cargo based on the pressure within the internal volume.
  • Paragraph 5 The underwater vehicle of paragraph 4, wherein the pressure compensation system is arranged to maintain the pressure of the fluid cargo equal to or above the pressure within the internal volume.
  • Paragraph 6 The underwater vehicle of paragraph 2 or 3, wherein the pressure compensation system is arranged to control the pressure of the fluid cargo based on the pressure exterior to the outer hull.
  • Paragraph 7 The underwater vehicle of paragraph 6, wherein the pressure compensation system is arranged to maintain the pressure of the fluid cargo equal to or above the pressure exterior to the outer hull, and wherein the pressure compensation system further comprises: a second pressure communication channel between the second portion and the exterior of the outer hull.
  • Paragraph 8 The underwater vehicle of any of paragraph 4 to 7, wherein the pressure compensation system comprises: a pump unit for pumping seawater into the second portion of the vessel to create an overpressure in the vessel; and a relief unit for relieving pressure when the overpressure exceeds a maximum overpressure value and for increasing the pressure the when the underpressure exceeds a maximum underpressure value.
  • Paragraph 9 The underwater vehicle of any of paragraph 2 to 8, wherein the barrier comprises one of the following: a mechanical piston; a batching pig; an expandable balloon; or a layer of a third substance separating the fluid cargo and seawater.
  • Paragraph 10 The underwater vehicle of any preceding paragraph, wherein the cargo in each of the one or more internal vessels comprises one or more of the following: C02; production fluids; injection fluids; MEG; methanol; freshwater; seawater; toxic waste; sand; septic/bio-mass; mud; brine; drill cuttings; and bio fuel.
  • Paragraph 11 The underwater vehicle of any preceding paragraph, wherein the internal volume is filled with seawater.
  • Paragraph 12 The underwater vehicle of any preceding paragraph, further comprising an evaporator for evaporating a liquefied gas, the evaporated gas arranged to fill at least one of: a top portion of the outer hull; an expandable bladder in the top portion of the outer hull; and a rigid tank in the top portion of the outer hull.
  • Paragraph 13 The underwater vehicle of paragraph 12, wherein the evaporated gas is selectively vented from the outer hull to decrease the buoyancy; or wherein the vehicle further comprises a compressor for compressing the evaporated gas into a liquefied state.
  • Paragraph 14 The underwater vehicle of paragraph 12 or 13, wherein the liquefied gas is the fluid cargo.
  • Paragraph 15 The underwater vehicle of any of paragraph 12 to 14, further comprising a tank for holding the liquefied gas.
  • Paragraph 16 The underwater vehicle of any preceding paragraph, wherein each of the one or more inner vessels has a substantially cylindrical shape, and wherein the outer hull has a hydrodynamic shape.
  • Paragraph 17 A method for transporting a fluid cargo in an underwater vehicle, the underwater vehicle having an outer hull and one or more internal vessels arranged within the outer hull, the outer hull defining an internal volume, the method comprising: loading the one or more vessels with the fluid cargo; balancing the pressure of the internal volume with the pressure exterior to the underwater vehicle; and controlling the pressure of the fluid cargo based on a pressure outside of the internal vessels.
  • Paragraph 18 The method of paragraph 17, wherein loading the one or more internal pressure vessels with the fluid cargo comprises: filling a first portion of the pressure vessel with the fluid cargo, wherein the first portion is separated from a second portion of the pressure vessel by a barrier, the barrier permitting pressure communication between the first and second portions.
  • Paragraph 19 The method of paragraph 18, further comprising: when the pressure of the internal volume changes, opening the second portion to the pressure of the internal volume, causing the moveable barrier to move to equalise the pressure of the fluid cargo in the first portion with the pressure of the internal volume.
  • Paragraph 20 The method of paragraph 18, further comprising: when the pressure external to the outer hull changes, opening the second portion to the pressure external to the outer hull, causing the moveable barrier to move to equalise the pressure of the fluid cargo in the first portion with the pressure external to the outer hull.
  • Paragraph 21 The method of paragraph 18, further comprising: pumping seawater into the second portion of the vessel to create an overpressure; relieving surplus pressure if the internal overpressure exceeds a maximum overpressure value; and increasing the pressure if the internal underpressure exceeds a maximum underpressure value.
  • Paragraph 22 The method of any preceding paragraph, further comprising: flooding an internal volume between the outer hull and the one or more vessels with seawater.
  • Paragraph 23 The method of any preceding paragraph, further comprising: evaporating a liquefied gas to fill at least one of: a top portion of the outer hull, an expandable bladder in the top portion of the outer hull; and a rigid tank in the top portion of the outer hull.
  • Paragraph 25 The method of paragraph 23, further comprising: venting the evaporated gas from the outer hull to decrease the buoyancy; or compressing the evaporated gas into a liquefied state to decrease the buoyancy.
  • Paragraph 25 The underwater vehicle of paragraph 23 or 24, wherein evaporating a liquefied gas comprises evaporating some of the cargo.
  • the underwater vehicle 802 transports fuel to a tanker 808 (surface vessel) for in-situ refuelling.
  • the tanker or other vessel may be at rest or may be moving. Typically, the vessel slows down from its normal transport speed but keeps moving during the refuelling operation.
  • the tanker 808 comprises a refuelling hose 804, which is deployed from a reel, spool or other storage device on the tanker 808, to a water depth below the wave zone.
  • the refuelling hose 804 is also referred to herein as fuel hose 804.
  • the wave zone may be defined as the volume of water proximal to the surface of the water 810, which is affected by surface weather conditions.
  • the end of the refuelling hose which terminates in the water, comprises a head 806.
  • the head 806 may comprise a connecting means, stabilising means and a communicating means.
  • the underwater vehicle 802 can transport the fuel to the head of the refuelling hose 806.
  • the underwater vehicle 802 comprises a connector.
  • the connector may be built into the underwater vehicle 802, or, it may be disposed on the end of an arm 1208, which protrudes from the underwater vehicle.
  • the arm can be withdrawn into a cavity of the underwater vehicle 802 during transit and can be extended in response to locating the head of the refuelling hose.
  • the arm can be extended when the position of the head at a distance smaller than the length of the arm from the underwater vehicle.
  • the arm is rigid.
  • the arm is able to transport fuel from the underwater vehicle 802 to the refuelling hose 804 via the connector, when in connection with the connector of the refuelling hose.
  • the connecting means of the refuelling hose may comprise a mechanical connector, adapted in shape to form a hermetic seal with the underwater vehicle 802 such that fuel from the underwater vehicle 802 can be delivered to the moving tanker 808 via the refuelling hose 804.
  • the connecting means further comprises an electrical connector.
  • the electrical connector and the connector of the underwater vehicle may comprise an inductor element for transferring electrical power.
  • the electrical connector may comprise a male or female end, which is respectively configured to fit or receive a female or male end of the connector of the underwater vehicle 802. In this way, electrical power can be transferred from the tanker 808 to the underwater vehicle 802.
  • the head of the refuelling hose 806 comprises a “shuttlecock shaped” end, which increases water resistance and therefore ensures that this substantially horizontal configuration is set up.
  • substantially horizontal means the head of the refuelling hose 806 is disposed at an angle of less than 10 degrees relative to the water surface 810, more preferably 5 degrees. This horizontal configuration ensures that the connecting means of the refuelling hose can easily fit or receive the corresponding connector on the underwater vehicle.
  • one or more weights 902 are attached to the refuelling hose 804.
  • the head of the refuelling hose 806 is in a substantially horizontal configuration as this simplifies the geometry of the connecting process.
  • Figure 9A shows a refuelling hose 804 without a weight.
  • the refuelling hose 804 is attached to a moving tanker 808. If the velocity or the drag on the refuelling hose 804, which acts, to a first approximation, in a horizontal direction, is not large enough, the head of the refuelling hose 806 may not reach the horizontal, as depicted in Figure 8.
  • a weight 902 is added to the refuelling hose 804
  • the shape of refuelling hose in the water can be modified.
  • the weight is added to the midpoint of the refuelling hose.
  • one or more weights 902 can be added at one or more different points on the refuelling hose 804.
  • the end of the refuelling hose 806 can reach closer to the horizontal because the refuelling hose 804 is able to bend around the point in which the weight is disposed.
  • the “shuttlecock-shaped” end may be the stabilising means.
  • the stabilising means of the refuelling hose further comprises one or more elements 1002, 1104.
  • the one or more elements 1002, 1104 may act as a steering means to stabilise the head of the refuelling hose 806.
  • the head of the refuelling hose 806 comprises two wing elements 1002. Referring to Figures 10A to 10D, exemplary wing-shaped steering elements 1002 are shown in different configurations and views. In Figure 9A, a projected view of the head of the refuelling hose 806 and two wing elements 1002 is shown along the direction of water drag.
  • FIG 9B a side-view of the head of the refuelling hose 806 and wing elements 1002 are shown.
  • the direction of water drag is denoted by the arrow.
  • Figure 10C and 10D two configurations of the wing elements 1002 are shown.
  • the wing 1002 is in a “negative y” configuration.
  • both the wing elements 1002 are inclined at a “negative” angle to the direction of water drag, thereby causing a net force on the wing element 1002 in the negative y direction.
  • the wing element 1002 is in a “positive y” configuration.
  • both the wing elements 1002 are inclined at a “positive” angle to the direction of water drag, thereby causing a net force on the wing element 1002 in the positive y direction.
  • the wings 1002 are respectively rotated in an anticlockwise and clockwise fashion along the longitudinal axis of the wing element.
  • the wing elements 1002 may not be configured to rotate but are fixed instead.
  • the water which flows above and below the wing elements 1002 as the tanker moves, acts to increase the rotational inertia of the refuelling hose 804, thereby stabilising it.
  • the wing elements 1002 act to stabilise the head of the refuelling hose 806, which aids the connection process.
  • the position of the head 806 may be controlled by unreeling the refuelling hose 804 from the surface vessel 808.
  • the head of the refuelling hose 806 comprises four wing elements 1002, 1104. Referring to Figures 11 A to 11 D, exemplary wing-shaped steering elements 1002, 1104 are shown in different configurations and views.
  • FIG 11A a projected view of the head of the refuelling hose 806 and four wing elements 1002, 1104 are shown along the direction of water drag.
  • Figure 11 B a topside view of the head of the refuelling hose 806 and wing elements 1104 is shown. The direction of water drag is denoted by the arrow.
  • Figure 11C and 11 D two configurations of the wing elements 1104 are shown. In Figure 11C, the wing 1104 is in a “positive x” configuration. In the “positive x” configuration, both the wing elements 1104 are inclined at a “positive” angle to the direction of water drag, thereby causing a net force on the wing element 1104 to move in the positive x direction.
  • both the wing elements 1104 are inclined at a “negative” angle to the direction of water drag, thereby causing a net force on the wing element in the negative x direction.
  • the position of the head of the refuelling hose 806 can be controlled in the x direction.
  • the wings 1104 are respectively rotated in an anticlockwise and clockwise fashion along the longitudinal axis of the wing element.
  • the other two wing elements 1002 can be used to control the position of the head of the refuelling hose 806 in the y direction, thereby facilitating greater control of the refuelling hose 804.
  • the position of the head 806 may be controlled by unreeling the refuelling hose 804 from the surface vessel 808.
  • the actuation of the steering elements is powered by power lines connected to the surface vessel.
  • the controller may also be located on the surface vessel.
  • the head of the refuelling hose 806 may comprise one or more propulsion elements.
  • the propulsion elements may be configured to control the position of the head.
  • the propulsion elements may be propellers, thrusters or other elements known to the skilled person and may be controlled from the vessel via an umbilical or wireless communication means.
  • the head of the refuelling hose 806 may comprise one or more buoyancy elements.
  • the communicating means between the head of the refuelling hose and the subsea vehicle may comprise an acoustic receiver and/or transmitter.
  • the acoustic system can be either active or passive. In an active acoustic system, an acoustic transmitter generates a sound, which in turn, may cause an echo. The echo can be analysed to determine the position of the object that caused the echo.
  • the head of the refuelling hose 806 may comprise an acoustic receiver and acoustic transmitter to locate the connector of the underwater vehicle 802.
  • the connector of the underwater vehicle 802 may also comprise an acoustic receiver and/or transmitter.
  • the underwater vehicle may also be configurable to locate the connector of the refuelling hose 804 in the manner described above.
  • the connector of the underwater vehicle 802 and the acoustic receiver may further be communicatively coupled.
  • they may be communicatively coupled by wireless communication means.
  • the relative position of each connector can be more finely tuned.
  • the relative positions of each result can be compared to generate a moving average.
  • the acoustic transmitters and receivers may comprise an array, centred on the connector of the refuelling hose or connector of the underwater vehicle, in order that the results can be triangulated to improve accuracy.
  • the acoustic system may be passive.
  • the connecting means may comprise a transmitter or a receiver and the connector of the underwater vehicle comprises a corresponding receiver or transmitter.
  • a transmitter emits a sound from the head of the refuelling hose 806, which is detected by the receiver.
  • the “stationary” object comprises a transmitter and the component comprising the receiver element moves relative to that object. Therefore, either the connector of the underwater vehicle can be actively positioned onto the connecting means of refuelling hose, or, the connecting means of the refuelling hose can be actively positioned onto the connector of the underwater vehicle.
  • the underwater vehicle 802 will have a large inertia. Accordingly, fine positional control of the underwater vehicle 802 may be difficult to achieve in practice. For this reason, the underwater vehicle 802 may be used to position the fuel proximal to the connecting means of the refuelling hose 806. In some examples, proximal means within a ten-metre radius of the connecting means of the refuelling hose 806, more preferably 1 metre. In other examples, it may include positioning the underwater vehicle within the range of the arm 1208, or the range of motion of the refuelling hose.
  • the method of refuelling the tanker 808 may therefore comprise two stages: i) positioning of the underwater vehicle 802 into range of the arm 1208 of the underwater vehicle 802 and/or range of the head of the refuelling hose 806; and ii) fine positioning of the arm 1208 of the underwater vehicle 802 or fine positioning of the head of the refuelling hose 806.
  • the connector of the underwater vehicle 802 and the connector of the refuelling hose 806 may each comprise a magnetic element. The magnetic elements of each connector may be configured to attract to ensure the connectors align and engage correctly.
  • the underwater vehicle 802 and the head of the refuelling hose 806 may be connected to a surface buoy via a line.
  • the line is preferably slack to decouple subsea components from the wave zone.
  • Each surface buoy may include one or more positioning devices, such as a GPS tracker, to monitor the position of the surface buoys.
  • the respective buoys can be used to determine the location of the underwater vehicle and the head of the refuelling hose.
  • the buoys may not be directly above the underwater vehicle 802 or head of the refuelling hose 806 from which they are connected. The buoys may therefore serve as an indicator of the position, rather than denoting an accurate location.
  • the communicating means may comprise an optical system, comprising an optical transmitter and/or receiver in an analogous way to the acoustic system described above.
  • the seal can be locked into place using a locking mechanism.
  • a valve separating the fuel in the underwater vehicle 802 from the arm 1208 may be opened.
  • the fuel may be stored under high pressure and the pressure difference between the refuelling hose 804 and internal vessel of the underwater vehicle urges the fuel, from the internal vessel of the underwater vehicle, through the arm 1208 via the connection, into the refuelling hose 804 and finally into the tanker 808.
  • the overpressure may not be large enough to urge the fuel into the tanker 808 because the refuelling hose 804 is at a reasonable depth (to avoid the wave zone).
  • one or more pumps are used to deliver the fuel from the underwater vehicle 802 to the tanker 808.
  • the one or more pumps are located within the refuelling hose 804. Power cables may connect the pump directly to a power source on the tanker 808.
  • the pumps may be disposed in series along the refuelling hose 804 to ensure rapid refuelling.
  • a pump may be located in the underwater vehicle 802.
  • the pump may be powered by a local energy storage unit on the underwater vehicle 802, or, by a power source on the tanker 808.
  • the local energy storage unit may comprise a hydrogen fuel cell, battery or a nuclear power source.
  • the connecting means of the refuelling hose 806 and the connector of the underwater vehicle 802 may comprise an inductor element.
  • the inductor elements may comprise a coil 1202, 1206 and the plane of each coil may be adjacent to the connection/seal between each connector to ensure efficient energy transfer.
  • the coil 1202, 1206 may be located in an annulus 806, 1212 of the refuelling hose and arm 1208.
  • Power cables 1204, 1210 for connecting the power source on the tanker 808 and the local energy storage unit on the underwater vehicle may also be located in the annulus 806, 1212 of the refuelling hose and arm 1208. In this way, power can be delivered to the local energy storage unit for recharging, or, directly to the pump.
  • the fuel is ammonia and stored in a liquid state at a pressure of around 10 bar.
  • the fuel may also be other types of fuel, including biofuels, liquid oxygen or liquefied petroleum gas, as would be appreciated by the skilled reader.
  • refuelling occurs just below the wave zone. That is, at a water depth of approximately 100 metres. At this depth, the temperature and pressure conditions are that ammonia may be in a liquid state.
  • the locking mechanism is unlocked and the connectors are disengaged.
  • the refuelling hose 804 may then be reeled back onto the reel on the tanker 808.
  • the valve, separating the internal vessel containing the fuel from the refuelling hose 804 may be closed before the pump is stopped to ensure that any fuel inside the refuelling hose 804 has been delivered to the tanker 808 before disengagement.
  • the surface vessel does not release a refuelling hose, but instead the underwater vehicle releases a refuelling hose with a positive buoyancy element in the vicinity of the surface vessel.
  • the refuelling hose is also referred to herein as fuel hose.
  • the vicinity of the surface vessel means within a distance between the surface vessel (or tanker) which is less than the length of the refuelling hose.
  • the refuelling hose is released along a shipping lane so that the surface vessel does not need to deviate substantially from its path.
  • the refuelling hose may be stored in a cavity of the underwater vehicle and can be released when it is detected that the underwater vehicle is in the vicinity of the surface vessel.
  • the positive buoyancy element will bring the head of the hose to the water surface where it can be located and picked up by the surface vessel and connected to the surface vessel for refuelling.
  • This arrangement does not require any specialised equipment at the surface vessel, but equipment conventionally present at the surface vessel can be used in this operation.
  • the positive buoyancy element may include an acoustic or optical beacon or simply a brightly coloured buoy to facilitate locating the element at the water surface.
  • the underwater vehicle 802 may be refilled with fuel at a designated refilling station 1302.
  • the refilling station 1302 is preferably located on the seabed in shallow water. Shallow water means water to a depth of less than 500 metres, preferably less than 300 metres.
  • the refilling station 1302 comprises one or more fuel storage tanks for refilling the underwater vehicle 802.
  • the refilling station may also be connected to an onshore storage or production facility with pipelines. In some examples, the same connector used in the refuelling process of the tanker 808 may be used with the one or more storage tanks during refilling.
  • the refilling station 1302 may be located on a floating platform 1310, which is anchored to the seabed using one or more wires 1306.
  • the floating platform 1310 may comprise one or more buoyancy elements 1304 configured to ensure that the platform 1310 and the one or more storage tanks 1308 have a combined positive buoyancy.
  • the floating platform 1310 may comprise a platform where one or more underwater vehicles 802 can park for refilling. The depth of the platform where the underwater vehicles park is preferably less than 500 metres.
  • the general method described above is illustrated in Figure 14, and includes the steps of (S1402) positioning the surface vessel and the unmanned underwater vehicle relative to each other at a distance smaller than the length of a fuel hose; (S1404) connecting the fuel hose between the unmanned underwater vehicle and the surface vessel; (S1406) transferring the fuel from the unmanned underwater vehicle to the surface vessel; and (S1408) releasing the fuel hose.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Ocean & Marine Engineering (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Abstract

L'invention concerne un procédé de ravitaillement en carburant d'un navire de surface à partir d'un véhicule sous-marin sans équipage, le véhicule sous-marin comprenant un ou plusieurs récipients internes pour contenir du carburant, le procédé comprenant les étapes consistant à : positionner le navire de surface et le véhicule sous-marin sans équipage l'un par rapport à l'autre à une distance inférieure à la longueur d'un tuyau de carburant; raccorder le tuyau de carburant entre le véhicule sous-marin sans équipage et le navire de surface ; transférer le carburant du véhicule sous-marin sans équipage au navire de surface ; et libérer le tuyau de carburant.
PCT/NO2021/050129 2020-05-22 2021-05-21 Système de ravitaillement en carburant et de stockage WO2021235945A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB2007678.2A GB2585758B (en) 2020-05-22 2020-05-22 Underwater vehicle for transporting cargo
GB2007678.2 2020-05-22
GB2018077.4 2020-11-17
GB2018077.4A GB2595321B (en) 2020-05-22 2020-11-17 Refuelling and storage system

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PCT/NO2021/050114 WO2021235940A1 (fr) 2020-05-22 2021-05-05 Véhicule sous-marin pour le transport d'une cargaison
PCT/NO2021/050129 WO2021235945A1 (fr) 2020-05-22 2021-05-21 Système de ravitaillement en carburant et de stockage

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WO2022221924A1 (fr) * 2021-04-22 2022-10-27 Christopher Colin Stephen Système de transport et de stockage de gaz
GB2608814A (en) * 2021-07-12 2023-01-18 Equinor Energy As Subsea shuttle landing and support device
GB2608862A (en) * 2021-07-15 2023-01-18 Equinor Energy As Buoyancy control method
GB2609952A (en) * 2021-08-18 2023-02-22 Equinor Energy As An underwater vehicle for transporting fluid
GB2614756A (en) * 2022-01-18 2023-07-19 Equinor Energy As Energy harvesting in subsea shuttle
GB2615601A (en) * 2022-02-15 2023-08-16 Equinor Energy As Autonomous vehicle pressure control

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CN114604397B (zh) * 2022-03-18 2023-09-29 天津大学 一种海洋温差供蓄能定域剖面穿梭无人平台

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WO2021235940A1 (fr) 2021-11-25
GB202018077D0 (en) 2020-12-30
GB2585758A (en) 2021-01-20
GB202007678D0 (en) 2020-07-08
GB2585758B (en) 2021-12-22
GB2595321A (en) 2021-11-24
GB2595321B (en) 2022-08-24

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